A water-based anti-flash rust coating, a preparation method and application thereof

Abstract

The application discloses a kind of waterborne anti-flash rust coating and its preparation method and application, belong to coating technical field;The waterborne anti-flash rust coating provided by the application includes component A and component B;Component A includes the following components by mass fraction: 0-15 parts of water, 0.1-0.5 parts of pH regulator, 0.1-0.5 parts of dispersant, 0.01-0.1 parts of defoaming agent, 1-10 parts of pigment, 30-60 parts of filler, 20-35 parts of resin, 0.6-4 parts of film-forming aid, 0-0.2 parts of functional aid, 0.01-0.2 parts of thickening agent;Component B includes the following components by mass fraction: 0.3-2 parts of acetone oxime;The pH regulator includes sodium hydroxide;The average molecular weight of dispersant is 2000-4000;The solid content of component A is 69-71%.The early water resistance and anti-flash rust property of the waterborne anti-flash rust coating provided by the application are excellent, and the surface drying time is shorter.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and particularly relates to a water-based anti-flash rust coating, its preparation method, and its application. Background Technology

[0002] Water-based coatings have advantages such as low environmental hazard, convenient application, good safety, and easy storage and transportation, and their application is becoming increasingly widespread, with the potential to completely replace solvent-based coatings in the future. However, when water-based coatings are used on steel surfaces, due to the high latent heat of volatilization of water as the dispersion medium during film formation and its slow evaporation rate, multiple small-area corrosion cells will form on the metal surface under the action of oxygen and water, ions, etc. in the water-based coating components, resulting in electrochemical corrosion and flash rust. Ultimately, this leads to a significant decrease in the adhesion of the paint film, seriously affecting its anti-corrosion performance and aesthetics.

[0003] In existing technologies, water-based coatings applied to metal substrates typically require the addition of anti-flash rust agents to prevent flash rust during the drying process. Early anti-flash rust agents mainly contained components such as chromates, dichromates, tetraborates, arsenates, and nitrites. For example, sodium nitrite works by reacting with the metal surface to form a dense passivation film, thereby slowing down or preventing corrosion. These inorganic compounds generally suffer from high biotoxicity, environmental pollution, and high cost, significantly limiting their application. Currently, most commercially available anti-flash rust agents are highly water-soluble nitrites, but they only have an anti-rust effect on ferrous substrates. This requires large quantities, easily leaches out, and causes poor water resistance in the paint film, severely affecting its anti-corrosion performance. Furthermore, nitrites are toxic and considered indirect carcinogens, contradicting green environmental protection principles. Therefore, developing an anti-flash rust agent that offers excellent anti-flash rust performance, is environmentally friendly, inexpensive, and does not affect paint film performance after application is of great significance. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a water-based anti-flash rust coating with excellent anti-flash rust properties, early water resistance, and short surface drying time, as well as its preparation method and application.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a water-based anti-flash rust coating, the water-based anti-flash rust coating comprising component A and component B;

[0006] Component A comprises the following components in parts by weight: 0-15 parts water, 0.1-0.5 parts pH adjuster, 0.1-0.5 parts dispersant, 0.01-0.1 parts defoamer, 1-10 parts pigment, 30-60 parts filler, 20-35 parts resin, 0.6-4 parts film-forming aid, 0-0.2 parts functional aid, and 0.01-0.2 parts thickener;

[0007] Component B comprises the following components in parts by weight: 0.3-2 parts of acetone oxime;

[0008] The pH adjuster includes sodium hydroxide and / or potassium hydroxide;

[0009] The average molecular weight of the dispersant is 2000-4000;

[0010] The solid content of component A is 69-71%.

[0011] The water-based anti-flash rust coating provided by this invention can effectively achieve a good anti-flash rust effect on metal substrates without adding conventional toxic, harmful or heavily polluting traditional anti-flash rust agents such as sodium nitrite and hexavalent chromium. Furthermore, the water-based anti-flash rust coating provided by this invention has excellent early water resistance and a short surface drying time.

[0012] Specifically, in the first aspect, this invention introduces acetone oxime into component B, which can effectively react with oxygen in water, thereby effectively removing dissolved oxygen from the water-based anti-flash rust coating system itself, as well as dissolved oxygen that slowly seeps in from the air during subsequent coating and coating drying. The equation for the reaction between acetone oxime and oxygen is 4(CH3)2C=N-OH+O2→4(CH3)2C=O+2N2+H2O, and the reaction in small amounts is 2(CH3)2C=N-OH+O2→2(CH3)2C=O+N2O+H2O. In the second aspect, this invention controls the addition amounts of components A and B. Components A and B within a suitable range can effectively consume the oxygen within the system and the dissolved oxygen that subsequently seeps in, while avoiding the impact of acetone oxime on the stability of the water-based anti-flash rust coating, thus achieving a good anti-flash rust effect. Thirdly, this invention selects sodium hydroxide and / or potassium hydroxide as pH adjusters, which are highly alkaline and non-volatile. During the drying process after the water-based anti-flash rust coating is applied, the pH value of the system gradually increases, thereby helping the resin to demulsify quickly under highly alkaline conditions, thus shortening the surface drying time. Simultaneously, the shortened surface drying time further prevents the penetration of dissolved oxygen, thereby improving the product's anti-flash rust effect. Fourthly, this invention selects a dispersant with an average molecular weight of 2000-4000. Dispersants within this molecular weight range can provide more anchoring groups, thus having a better effect on reducing system viscosity. Therefore, under the action of this type of dispersant, relatively more pigments and fillers can be added to increase the solid content of component A, thereby helping to achieve a faster surface drying speed and improving the product's anti-flash rust and early water resistance. Fifthly, this invention further limits the solid content of component A to 69-71%. When component A within this solid content range is mixed with subsequent component B, it can increase the drying speed of the coating, thereby improving the product's anti-flash rust and early water resistance; and it can also avoid the situation where the preparation is impossible due to excessively high solid content.

[0013] For example, the average molecular weight of the dispersant can be any point value or any two-point range value between 2000 and 4000, such as 2000, 2200, 2400, 2600, 2800, 3000, 3200, 3400, 3600, 3800, 4000, etc.

[0014] In one embodiment, the dispersant is SN-5040 from Seinnoko Corporation of Japan, with an average molecular weight of 3500.

[0015] This invention has found that when SN-5040 is further selected as the dispersant, it can better anchor the functional groups, reduce the viscosity of the system, and increase the solid content of the system, thereby helping to achieve good anti-flash rust effect and early water resistance of the product.

[0016] For example, the solid content of component A can be any point value or any two-point range value between 69-71%, such as 69.0%, 69.2%, 69.4%, 69.6%, 69.8%, 70%, 70.2%, 70.4%, 70.6%, 70.8%, 71%, etc.

[0017] As a preferred embodiment of the water-based anti-flash rust coating of the present invention, component A comprises the following components in parts by weight: 10-12 parts water, 0.2-0.3 parts pH adjuster, 0.2-0.3 parts dispersant, 0.02-0.04 parts defoamer, 1.2-2 parts pigment, 45-55 parts filler, 25-30 parts resin, 1-2 parts film-forming aid, 0-0.2 parts functional aid, and 0.05-0.1 parts thickener.

[0018] The present invention has found that the mass fraction of the components in component A and the subsequently added component B interact with each other, thereby affecting the surface drying speed of the coating, and consequently affecting the coating's flash rust prevention ability and early water resistance.

[0019] In a preferred embodiment of the water-based anti-flash rust coating of the present invention, the mass ratio of component A to component B is 1:(0.003-0.022).

[0020] For example, the mass ratio of component A to component B can be any point value or any two points between 1:(0.003-0.022), such as 1:0.003, 1:0.005, 1:0.008, 1:0.01, 1:0.012, 1:0.0014, 1:0.016, 1:0.018, 1:0.02, 1:0.022, etc.

[0021] This invention has found that a suitable mass ratio of components A and B can effectively balance the anti-flash rust effect and early water resistance. When the mass ratio of components A and B is further selected within the above range, the overall effect of the product is even better.

[0022] In a preferred embodiment of the water-based anti-flash rust coating of the present invention, the resin comprises anionic acrylic emulsion.

[0023] In a preferred embodiment of the water-based anti-flash rust coating of the present invention, the solid content of the resin is ≥47%.

[0024] In one embodiment, the resin is Wanhua Chemical's 0628, with a solid content of 47%; or the resin is Foshan Badefu's S984, with a solid content of 47%.

[0025] The present invention has found that selecting 0628 or S984 as resin results in a faster drying speed, which allows it to work well with other components, further improving the surface drying speed and early water resistance of the coating, thereby enhancing the anti-flash rust effect of the coating.

[0026] In a preferred embodiment of the water-based anti-flash rust coating of the present invention, the film-forming aid includes at least one of alcohol ester dodecyl and dipropylene glycol methyl ether.

[0027] The present invention has found that when the film-forming aid is further selected as at least one of alcohol ester dodecyl or dipropylene glycol methyl ether, both can have excellent synergistic effects with other components, helping to improve the drying speed of the coating, thereby achieving good anti-flash rust effect and early water resistance of the coating.

[0028] In a preferred embodiment of the water-based anti-flash rust coating of the present invention, the defoamer includes an organosilicon water-based defoamer.

[0029] In one embodiment, the defoamer is German Dego 901W; or the defoamer is Shanghai Shenzhu Chemical 6791.

[0030] In a preferred embodiment of the water-based anti-flash rust coating of the present invention, the pigment includes at least one of titanium dioxide, carbon black, iron black, phthalocyanine blue, and phthalocyanine green.

[0031] In a preferred embodiment of the water-based anti-flash rust coating of the present invention, the filler includes at least one of calcium carbonate, talc, natural barium sulfate, and precipitated barium sulfate.

[0032] In a preferred embodiment of the water-based anti-flash rust coating of the present invention, the thickener includes a polyurethane associative thickener.

[0033] In one embodiment, the thickener is Vesmody U-505 from Wanhua Chemical; or the thickener is RM-8W from Rohm and Haas; or the thickener is 5010S from Foshan Shierli New Materials Co., Ltd.

[0034] In a preferred embodiment of the water-based anti-flash rust coating of the present invention, the functional additives include at least one of wetting agents and leveling agents.

[0035] The present invention has found that when the defoamer, pigment, filler, thickener and functional additives are further selected as the above-mentioned substances, the overall performance of the obtained product is better.

[0036] In a second aspect, the present invention provides a method for preparing a water-based anti-flash rust coating, the method comprising the following steps:

[0037] (1) While stirring, add pH adjuster, dispersant, defoamer, pigment and filler to water in sequence and grind with sand to obtain slurry;

[0038] (2) While stirring, resin, film-forming aid, thickener and functional aid are added to the slurry in sequence to obtain component A;

[0039] (3) Mix component A and component B evenly to obtain a water-based anti-flash rust coating.

[0040] The method for preparing the anti-flash rust coating provided by this invention can achieve better overall performance of the coating by selecting a specific order of adding materials.

[0041] In a preferred embodiment of the preparation method of the present invention, in step (1), the fineness of the slurry is <50μm.

[0042] In a preferred embodiment of the preparation method described in this invention, the viscosity of component A is ≤120 KU.

[0043] This invention has found that a suitable range of slurry fineness and a suitable range of viscosity of component A can effectively achieve early water resistance and flash rust prevention in coatings.

[0044] In a third aspect, the present invention provides the application of the water-based anti-flash rust coating in the preparation of a protective layer on the surface of a metal substrate.

[0045] The water-based anti-flash rust coating provided by this invention has excellent anti-flash rust properties and early water resistance, and can be effectively applied to the protection of metal substrate surfaces to achieve good results.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] The water-based anti-flash rust coating provided by this invention effectively achieves excellent anti-flash rust effects on metal substrates without adding conventional, toxic, harmful, or heavily polluting anti-flash rust agents such as sodium nitrite and hexavalent chromium. Furthermore, the water-based anti-flash rust coating provided by this invention exhibits excellent early water resistance and a short surface drying time; specifically, the obtained water-based anti-flash rust coatings all performed normally in flash rust tests, and their early water resistance was also normal, with a surface drying time of less than 30 minutes. Simultaneously, the raw materials for the water-based anti-flash rust coating provided by this invention are readily available, and the preparation method is simple to operate, which is beneficial for practical production. Detailed Implementation

[0048] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0049] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in the field.

[0050] Dispersant 1: Average molecular weight 3500, SN-5040, from Sannopco, Japan;

[0051] Dispersant 2: Average molecular weight 1350, HP2000, Anshan Huihong New Materials Co., Ltd.;

[0052] Dispersant 3: Average molecular weight 10000, B190, Foshan Shierli New Materials Co., Ltd.;

[0053] Defoamer: 901W, German brand DIGIC;

[0054] Pigment: Titanium dioxide, commercially available;

[0055] Filler: Calcium carbonate, commercially available;

[0056] Resin 1: Anionic acrylic emulsion, solids content 47%, 0628, Wanhua Chemical;

[0057] Resin 2: Anionic acrylic emulsion, solids content 47%, S984, Foshan Badefu;

[0058] Film-forming aid: Dodecyl alcohol ester, commercially available;

[0059] Thickener: Vesmody U-505, Wanhua Chemical;

[0060] Acetone oxime: Tianjin Damao Chemical Reagent Factory.

[0061] Examples 1-9 and Comparative Examples 1-8

[0062] The present invention provides a water-based anti-flash rust coating in the embodiments and comparative examples. The components (parts by mass) of the water-based anti-flash rust coating are shown in Tables 1-2.

[0063] The solid content of component A was determined in accordance with GB / T 1725-2007 "Determination of Non-volatile Matter Content in Paints, Varnishes and Plastics"; the viscosity of component A was determined in accordance with GB / T 1723-1993.

[0064] Table 1

[0065]

[0066]

[0067] Table 2

[0068]

[0069]

[0070] The preparation method of the water-based anti-flash rust coating provided in Example 1 includes the following steps:

[0071] (1) While stirring, add pH adjuster, dispersant, defoamer, pigment and filler to water in sequence and grind with sand to obtain slurry with a fineness of <50μm.

[0072] (2) While stirring, resin, film-forming aid, thickener and functional aid are added to the slurry in sequence to obtain component A;

[0073] (3) Mix component A and component B evenly to obtain a water-based anti-flash rust coating.

[0074] The preparation methods of Examples 2-9 and Comparative Examples 1-8 are consistent with those of Example 1.

[0075] Example 10

[0076] This invention provides a water-based anti-flash rust coating, the only difference from Example 1 being the addition of 0.05 parts of wetting agent (BYK-302).

[0077] Comparative Example 9

[0078] This invention provides a water-based anti-flash rust coating, the only difference between it and Example 1 being the preparation method. The preparation method of this comparative example is as follows:

[0079] (1) While stirring, add the dispersant, defoamer, pigment and filler into the water in sequence and grind them with sand to obtain a slurry with a fineness of <50μm.

[0080] (2) While stirring, add pH adjuster, resin, film-forming aid, thickener and functional aid to the slurry in sequence to obtain component A;

[0081] (3) Mix component A and component B evenly to obtain a water-based anti-flash rust coating.

[0082] Example of effect

[0083] The effectiveness examples of this invention verify the performance of the water-based anti-flash rust coatings prepared in Examples 1-10 and Comparative Examples 1-9, specifically including the following aspects:

[0084] 1. Surface drying time: Refer to the provisions of GB / T 1728-2020, wherein the surface drying is carried out according to the provisions of surface drying time method B;

[0085] 2. Anti-rust performance: Place the test panel in an environment with a temperature of 25℃ and a humidity of 95%RH or higher and visually observe the coating surface for any rust penetration. If rust is observed on the coating surface, record the time when rust is observed. If no rust is observed after 24 hours, immediately immerse the test panel in methyl ethyl ketone (MEK) to remove the coating (wooden tools can be used if necessary). Visually observe the substrate for any rust spots. If there are no rust spots on the substrate, it is rated as "normal".

[0086] The test panel was prepared by diluting the water-based anti-flash rust coating with appropriate water to a test spray viscosity of 65±2KU, using air spraying, and controlling the dry film thickness to 80μm.

[0087] 3. Early water resistance: Immerse half of the coating of the prepared and cured test panel in distilled water and observe. If at least one of the three test panels shows coating defects such as blistering, rusting, cracking, or peeling in the immersed area, record the corresponding immersion time. If no coating defects such as blistering, rusting, cracking, or peeling are observed after immersion for 5 hours, remove the test panel and visually observe it under natural or artificial sunlight as specified in GB / T 37356-2019 to further confirm that at least two of the three test panels do not show coating defects such as blistering, rusting, cracking, or peeling in the immersed area. After the test panel recovers under standard conditions for 2 hours, no obvious discoloration is observed in the immersed area compared to the unimmersed area. The result is rated as "no abnormality".

[0088] The method for curing the test plates is as follows: the prepared test plates are placed in an environment with a temperature of 25℃ and a humidity of 50%RH for 24 hours.

[0089] The test results are shown in Table 3.

[0090] Table 3

[0091]

[0092] As can be seen from Table 3, when the technical solution provided by the present invention is adopted, the obtained product has good flash rust prevention and early water resistance, and the surface drying time of the obtained product is short; specifically, the surface drying time of the obtained product is less than 30 minutes, and it can pass the flash rust prevention and early water resistance tests normally.

[0093] As can be seen from Example 1 and Comparative Examples 1-2, the mass fraction of acetone oxime has a significant impact on the performance of the product. When the mass fraction of acetone oxime in Comparative Example 1 is too small, the product fails the flash rust prevention test and rust is observed after 15 minutes, indicating poor flash rust prevention. When the mass fraction of acetone oxime in Comparative Example 2 is too large, the surface drying time of the product is too long, reaching 40 minutes, and it fails the early water resistance test, with blistering occurring after 4 hours of soaking, indicating poor early water resistance.

[0094] As can be seen from Example 1 and Comparative Examples 3-4, the solid content of component A also affects the overall performance of the product. When the solid content of component A in Comparative Example 3 is too low, the surface drying time of the obtained product is too long, reaching 42 minutes, and the obtained product fails the flash rust prevention test, with rust appearing after 4 hours of storage, indicating poor flash rust prevention. When the solid content of component A in Comparative Example 4 is too high, the corresponding product cannot be prepared.

[0095] As can be seen from Example 1 and Comparative Example 5, when other conventional pH adjusters such as ammonia are used, the resulting product fails the flash rust prevention test and rust is observed after 10 minutes of standing, indicating poor flash rust prevention.

[0096] As can be seen from Example 1 and Comparative Example 6, when other conventional flash rust inhibitors such as sodium nitrite are used, the product passes the flash rust prevention test normally, but fails the early water resistance test. It bubbles after soaking for 2 hours, indicating poor early water resistance.

[0097] As can be seen from Example 1 and Comparative Examples 7-8, the choice of dispersant also affects the overall performance of the product. When the average molecular weight of the dispersant in Comparative Example 7 is too low, the early water resistance test of the obtained product fails, and foaming occurs after soaking for 3 hours, indicating poor early water resistance. When the average molecular weight of the dispersant in Comparative Example 8 is too high, the corresponding product cannot be prepared.

[0098] As can be seen from Example 1 and Comparative Example 9, the order in which the pH adjuster is added in the preparation method also affects the performance of the product. When the pH adjuster is added after the slurry is formed, the corresponding product cannot be prepared.

[0099] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention and not to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A water-based anti-flash rust coating, characterized in that, The water-based anti-flash rust coating comprises component A and component B; Component A comprises the following components in parts by weight: 5-15 parts water, 0.1-0.5 parts pH adjuster, 0.1-0.5 parts dispersant, 0.01-0.1 parts defoamer, 1-10 parts pigment, 30-60 parts filler, 20-35 parts resin, 0.6-4 parts film-forming aid, 0-0.2 parts functional aid, and 0.01-0.2 parts thickener; The resin is an anionic acrylic emulsion; The functional additives include at least one of wetting agents and leveling agents; Component B consists of the following components in parts by weight: 0.3-2 parts of acetone oxime; The pH adjuster is sodium hydroxide and / or potassium hydroxide; The average molecular weight of the dispersant is 2000-4000; The solid content of component A is 69-71%; The mass ratio of component A to component B is 1:(0.003-0.022). The preparation method of the water-based anti-flash rust coating includes the following steps: (1) While stirring, add pH adjuster, dispersant, defoamer, pigment and filler to water in sequence and grind with sand to obtain slurry; (2) While stirring, resin, film-forming aid, thickener and functional aid are added to the slurry in sequence to obtain component A; (3) Mix component A and component B evenly to obtain a water-based anti-flash rust coating.

2. The water-based anti-flash rust coating according to claim 1, characterized in that, Component A comprises the following components in parts by weight: 10-12 parts water, 0.2-0.3 parts pH adjuster, 0.2-0.3 parts dispersant, 0.02-0.04 parts defoamer, 1.2-2 parts pigment, 45-55 parts filler, 25-30 parts resin, 1-2 parts film-forming aid, 0-0.2 parts functional aid, and 0.05-0.1 parts thickener.

3. The water-based anti-flash rust coating according to claim 1, characterized in that, The resin has a solids content of ≥47%.

4. The water-based anti-flash rust coating according to claim 1, characterized in that, The film-forming aid includes at least one of alcohol ester dodecyl and dipropylene glycol methyl ether; And / or, the defoamer includes an organosilicon aqueous defoamer; And / or, the pigment includes at least one of titanium dioxide, carbon black, iron black, phthalocyanine blue, and phthalocyanine green; And / or, the filler includes at least one of calcium carbonate, talc, natural barium sulfate, and precipitated barium sulfate; And / or, the thickener includes a polyurethane associative thickener.

5. The water-based anti-flash rust coating according to claim 1, characterized in that, In step (1), the fineness of the slurry is <50μm.

6. The water-based anti-flash rust coating according to claim 1, characterized in that, The viscosity of component A is ≤120 KU.

7. The application of the water-based anti-flash rust coating as described in any one of claims 1-4 in the preparation of a protective layer on the surface of a metal substrate.

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