A bio-based aqueous self-phosphatizing coating material, and a preparation method and application thereof

Abstract

The application discloses a kind of bio-based water-based self-phosphorization coating and its preparation method and application, including the mass ratio of 1:0.3-9 bio-based polysaccharide phosphate and water-based polyurethane curing agent, by bio-based polysaccharide phosphate as the hydroxyl component of coating and water-based polyurethane curing agent form coating, phosphoric acid group in coating can form phosphating film on the surface of metal base material, while keeping the anticorrosion performance of polyurethane coating, effectively save fossil energy, and the flexibility, compactness, salt and acid and alkali resistance of coating after curing are good.

Description

Technical Field

[0001] This invention relates to the field of coatings, and in particular to a bio-based waterborne self-phosphorizing coating, its preparation method, and its application. Background Technology

[0002] Due to increasingly severe environmental problems and the scarcity of fossil fuels, fossil raw materials used in coating materials are becoming increasingly precious and scarce. Utilizing bio-based raw materials to manufacture steel structure decorative and anti-corrosion coating materials, thereby reducing dependence on fossil fuels, is a major trend in the development of industrial anti-corrosion coatings.

[0003] Traditional industrial anti-corrosion coatings, due to their extensive use of volatile organic solvents (VOCs), cause significant environmental harm, leading to increasingly restricted applications. In contrast, water-based industrial anti-corrosion coatings, using water as the dispersion medium, offer advantages such as being non-flammable, non-toxic, environmentally friendly, and energy and resource-saving, resulting in rapid development. The performance of these products primarily depends on the film-forming resin; therefore, improving the performance of water-based industrial anti-corrosion coatings should begin with researching and developing high-performance film-forming resins. Currently, the main problems with water-based industrial anti-corrosion coatings include: poor water resistance due to the presence of hydrophilic emulsifiers; flash rust and corrosion in water-based coatings, resulting in poor alkali and acid resistance; and insufficient crosslinking density, leading to poor coating density and salt spray resistance.

[0004] Therefore, there is a need to provide an anti-corrosion coating with good overall performance. Summary of the Invention

[0005] In view of this, this application provides a bio-based waterborne self-phosphorizing coating, its preparation method and application, to solve the problem of how to improve the anti-corrosion performance of coatings.

[0006] To address the aforementioned technical problems, the present invention provides the following technical solutions.

[0007] In one aspect, this application provides a bio-based waterborne self-phosphorizing coating, comprising a bio-based polysaccharide phosphate ester and a waterborne polyurethane curing agent in a mass ratio of 1:0.3-9.

[0008] Preferably, the mass ratio of bio-based polysaccharide phosphate ester to waterborne polyurethane curing agent is 1:0.7-1.5.

[0009] The preferred method for preparing bio-based polysaccharide phosphate esters is as follows:

[0010] S1. Using bio-based starch as raw material, a hydrolysis reaction is carried out to obtain a sugar solution;

[0011] S2. After heating the sugar solution, mix it with the phosphoric acid solution, then carry out a gradient temperature increase reaction, and then adjust the pH to neutral to obtain the bio-based polysaccharide phosphate ester.

[0012] Preferably, in step S2, the mass concentration of the sugar solution is 60%, the mass concentration of the phosphoric acid solution is 50%, and the mass ratio of the sugar solution to the phosphoric acid solution is 120:30-60.

[0013] Preferably, in step S2, the heating temperature is 60-80℃ and the heating time is 1-2 hours.

[0014] Preferably, in step S2, the sugar solution is heated at 60°C for 1 hour and then mixed with the phosphoric acid solution, followed by a gradient temperature increase reaction. The gradient temperature increase reaction procedure is to react at 70°C for 1 hour, then react at 80°C for another 1 hour, and then adjust the pH to neutral to obtain the bio-based polysaccharide phosphate ester.

[0015] Preferably, bio-based starch includes one or more of tapioca starch and corn starch.

[0016] Preferably, the waterborne polyurethane curing agent includes one or more of Bayhydur VP LS2306, Bayhydur VP LS 2319, Bayhydur VP LS2336, Bayhydur XP 2547, Bayhydur XP 7001, and Bayhydur XP 7165.

[0017] Secondly, this application provides a method for preparing a bio-based waterborne self-phosphorizing coating, comprising the following steps: mixing and stirring a bio-based polysaccharide phosphate ester and a waterborne polyurethane curing agent in proportion to mass to obtain a bio-based waterborne self-phosphorizing coating.

[0018] Thirdly, this application provides an application of a bio-based waterborne self-phosphorizing coating in the protection of metal substrates.

[0019] The beneficial effects of this invention are:

[0020] This application uses bio-based starch as raw material to hydrolyze to obtain bio-based polysaccharide, and then grafts phosphate groups to obtain the hydroxyl component of the coating, so as to realize the self-phosphorization of the coating and eliminate the surface phosphorization treatment process.

[0021] The hydroxyl component is cured with water-based polyurethane curing agent to form a film. The proportion of renewable bio-based materials in the dry film is as high as 50% or more. The phosphate group in the coating can form a phosphate film on the surface of the metal substrate. While maintaining the anti-corrosion performance of polyurethane coating, it effectively saves fossil energy. Moreover, the cured coating has good flexibility, density, salt resistance and acid and alkali resistance.

[0022] Using bio-based starch as a raw material is environmentally friendly, and its hydrolyzed polysaccharide grafted phosphate has a high yield. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] This application provides a bio-based waterborne self-phosphorizing coating, comprising a bio-based polysaccharide phosphate ester and a waterborne polyurethane curing agent in a mass ratio of 1:0.3-9. The coating film performance within this range can achieve resistance to 20% sulfuric acid for more than 48 hours, resistance to 20% strong alkali for more than 48 hours, and resistance to salt spray for more than 500 hours. It also has good flexibility, strong adhesion, and short drying time.

[0025] The mass ratio of bio-based polysaccharide phosphate ester to waterborne polyurethane curing agent is 1:0.7-1.5. Within this range, the coating exhibits more balanced acid resistance, alkali resistance, and salt spray resistance.

[0026] The preparation method of bio-based polysaccharide phosphate esters is as follows:

[0027] S1. Using bio-based starch as raw material, a hydrolysis reaction is carried out to obtain a sugar solution;

[0028] S2. After heating the sugar solution, mix it with the phosphoric acid solution, then carry out a gradient temperature increase reaction, and then adjust the pH to neutral to obtain the bio-based polysaccharide phosphate ester.

[0029] In step S1, the hydrolysis method includes, but is not limited to, one or more of enzymatic hydrolysis and thermal hydrolysis (heating at 60°C for 2 hours); the sugar solution obtained in step S1 is a mixture of polysaccharides.

[0030] In step S2, the mass concentration of the sugar solution is 60%, the mass concentration of the phosphoric acid solution is 50%, and the mass ratio of the sugar solution to the phosphoric acid solution is 120:30-60.

[0031] In step S2, the heating temperature is 60-80℃ and the heating time is 1-2 hours.

[0032] In step S2, the sugar aqueous solution is heated at 60°C for 1 hour and then mixed with a phosphoric acid aqueous solution. A gradient temperature increase reaction is then carried out, with the reaction proceeding at 70°C for 1 hour, followed by a reaction at 80°C for another 1 hour. The pH is then adjusted to neutral to obtain the bio-based polysaccharide phosphate ester. This uniform gradient temperature increase procedure yields a high product yield and a short overall reaction time, enabling a greater amount of polysaccharide to graft onto phosphate groups, forming a high-bio-based hydroxyl component in the coating. This high bio-based content contributes to improved coating fullness and surface gloss.

[0033] In step S2, the reagent used to adjust the pH is an ammonia solution with a mass concentration of 25%-28%.

[0034] Bio-based starch includes one or more of tapioca starch and corn starch; phosphoric acid solution is prepared by adding water to commercially available phosphoric acid.

[0035] Waterborne polyurethane curing agents include one or more of Bayhydur VP LS2306, Bayhydur VP LS2319, Bayhydur VPLS2336, Bayhydur XP 2547, Bayhydur XP 7001, and Bayhydur XP 7165.

[0036] This application provides a method for preparing a bio-based waterborne self-phosphorizing coating, comprising the following steps: mixing and stirring a bio-based polysaccharide phosphate ester and a waterborne polyurethane curing agent in proportion to mass to obtain a bio-based waterborne self-phosphorizing coating.

[0037] This application provides an application of a bio-based waterborne self-phosphorizing coating in the protection of metal substrates. By applying the bio-based waterborne self-phosphorizing coating of this application to the metal substrate layer with a coating thickness of 3-5 mm, excellent anti-corrosion effect can be achieved.

[0038] The present application will be further described below through specific embodiments.

[0039] Example 1

[0040] A bio-based waterborne self-phosphorizing coating is prepared by mixing 40g of bio-based polysaccharide phosphate ester and 60g of waterborne polyurethane curing agent Bayhydur VP LS2306.

[0041] The preparation method of bio-based polysaccharide phosphate esters is as follows:

[0042] S1. Tapioca starch is heated at 60℃ for 2 hours to carry out hydrolysis reaction, and the resulting sugar solution is adjusted to achieve a mass concentration of 60%.

[0043] S2. Heat 120g of a 60% sugar solution to 60°C, then add 60g of a 50% phosphoric acid solution dropwise while stirring. After the addition is complete, keep the temperature at 60°C for 1 hour, then raise the temperature to 70°C and keep it at 70°C for 1 hour, then raise the temperature to 80°C and keep it at 80°C for 1 hour. Then cool to room temperature and neutralize with ammonia water to pH=7 to obtain a bio-based polysaccharide phosphate solution with a mass concentration of 63.75%.

[0044] Examples 2-8

[0045] A bio-based waterborne self-phosphorizing coating is identical to that in Example 1, except that the amounts of bio-based polysaccharide phosphate ester and waterborne polyurethane curing agent are different, and the dosages are shown in Table 1.

[0046] Table 1. Configuration schemes for different raw materials

[0047]

[0048] Examples 9-11

[0049] A bio-based waterborne self-phosphorizing coating is identical to that in Example 1, except that in step S2, 120g of a 60% sugar solution is heated to 60°C, and then 60g of a 50% phosphoric acid solution is added dropwise under stirring. After the addition is complete, the solution is kept warm for 1 hour. The subsequent heating procedure is different and is shown in Table 2.

[0050] Table 2 Configurations for different heating programs

[0051] Heating reaction procedure Example 1 70℃ for 1 hour - 80℃ for 1 hour Example 9 70℃ for 1 hour - 90℃ for 1 hour Example 10 60℃ for 1 hour - 80℃ for 1 hour Example 11 80℃ 1h - 80℃ 1h

[0052] Examples 12-14

[0053] A bio-based waterborne self-phosphorizing coating is identical to that in Example 1, except that the amounts of sugar solution and phosphoric acid solution used in step S2 are different, and the amounts are prepared as shown in Table 3.

[0054] Table 3. Preparation of sugar solution and phosphoric acid solution dosages

[0055]

[0056] Comparative Example 1

[0057] A coating is obtained by mixing 40g of polycaprolactone polyol and 60g of waterborne polyurethane curing agent Bayhydur VP LS 2306.

[0058] Testing and Analysis

[0059] The coatings used in the examples and comparative examples were applied to the surface of iron substrates with a coating thickness of 5 mm. After curing, the coating performance was tested according to national standard test methods. The adhesion was tested according to GB / T 1720-1979, the flexibility according to GB / T 1731-1993, and the acid, alkali and salt spray resistance according to GB / T1763-1979. The test results are shown in Table 4.

[0060] Table 4 Performance Test Results

[0061]

[0062] The results above show that the coatings prepared with the hydroxyl component of the bio-based glycophosphate synthesized by non-uniform heating have poorer adhesion, flexibility, and salt spray performance than those prepared with the hydroxyl component of the bio-based glycophosphate synthesized by uniform heating. In bio-based glycophosphates, the higher the phosphate group content, the better the film performance.

[0063] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0064] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A bio-based aqueous self-phosphatizing coating, characterized in that, The bio-based polysaccharide phosphate ester and the aqueous polyurethane curing agent have a mass ratio of 1:0.3-9. The preparation method of the bio-based polysaccharide phosphate ester is as follows: S1. Taking bio-based starch as raw material, hydrolysis reaction is carried out to obtain a sugar aqueous solution; S2. The sugar aqueous solution is heated and mixed with phosphoric acid aqueous solution, then gradient temperature reaction is carried out, and then the pH is adjusted to neutral, thereby obtaining the bio-based polysaccharide phosphate ester; wherein the heating temperature is 60-80℃, and the heating time is 1-2h.

2. The bio-based aqueous self-phosphatizing coating according to claim 1, characterized in that, The mass ratio of the bio-based polysaccharide phosphate ester and the aqueous polyurethane curing agent is 1:0.7-1.

5.

3. The bio-based aqueous self-phosphatizing coating according to claim 1, characterized in that, In step S2, the mass concentration of the sugar aqueous solution is 60%, the mass concentration of the phosphoric acid aqueous solution is 50%, and the mass ratio of the sugar aqueous solution to the phosphoric acid aqueous solution is 120:30-60.

4. The bio-based aqueous self-phosphatizing coating according to claim 1, characterized in that, In step S2, the sugar aqueous solution is heated at 60℃ for 1h, then mixed with phosphoric acid aqueous solution, and then gradient temperature reaction is carried out, wherein the gradient temperature reaction program is 70℃ for 1h, and then 80℃ for 1h, and then the pH is adjusted to neutral, thereby obtaining the bio-based polysaccharide phosphate ester.

5. The bio-based aqueous self-phosphatizing coating according to claim 1, characterized in that, The bio-based starch includes one or more of cassava starch and corn starch.

6. The bio-based aqueous self-phosphatizing coating according to claim 1, characterized in that, The aqueous polyurethane curing agent includes one or more of Bayhydur VP LS 2306, Bayhydur VP LS 2319, Bayhydur VP LS 2336, Bayhydur XP 2547, and Bayhydur XP 7165.

7. A method for the preparation of a bio-based aqueous self-phosphatizing coating according to any one of claims 1 to 6, characterized in that, The bio-based aqueous self-phosphatizing coating is prepared by mixing and stirring the bio-based polysaccharide phosphate ester and the aqueous polyurethane curing agent according to the mass ratio.

8. The bio-based aqueous self-phosphatizing coating according to any one of claims 1-6 in the protection of metal substrates.

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