A universal thermal control coating pretreatment agent and preparation and use method thereof

Abstract

The present application discloses a general thermal control coating pretreatment agent and a preparation and use method, which relates to the field of coatings, including silane coupling agent, tetraethyl orthosilicate, boric acid, ethyl acetoacetate, and solvent; the mass ratio of silane coupling agent, tetraethyl orthosilicate, boric acid, and ethyl acetoacetate is (100-150):(50-100):(1-10):(10-30); the silane coupling agent has amino and (ethoxy or methoxy). The bonding strength of the thermal control coating sprayed on the surface after metal gold plating, silver plating or nickel plating is greatly improved.

Description

Technical Field

[0001] The patent of this invention is applicable to the coating field, and is particularly applicable to the pre-treatment technology of spraying thermal control coating on the surface of metal substrates in the aerospace field. Background Art

[0002] The surface of products in the aerospace field often needs to be sprayed with thermal control coatings to meet thermal control requirements. Commonly used thermal control coatings include white paint with silicone rubber as a binder and black paint with epoxy resin as a binder. When non-metallic materials or metal materials are commonly used in the aerospace field to spray thermal control coatings, the pre-treatment methods and environmental requirements are relatively strict to ensure the bonding strength of the thermal control coating.

[0003] Taking aluminum alloy as an example, although phosphoric acid anodizing is beneficial to improving the adhesion of the coating, the surfaces of special-purpose products are usually plated with gold, silver, or nickel. The adhesion of the thermal control coating on the surfaces of these products is poor. The substrate is usually polished, sandblasted, and then sprayed with a surface treatment agent to improve the adhesion of the coating. The process is complicated and time-consuming, and cannot meet the requirements of large-scale production. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to provide a universal thermal control coating pretreatment agent and a preparation and use method, which is applied to the surface of a metal substrate after gold plating, silver plating or nickel plating, and can omit the grinding, sandblasting and other processes of the surface of the metal substrate after gold plating, silver plating or nickel plating, and can significantly improve the bonding strength between the surface of the metal substrate after gold plating, silver plating or nickel plating and the thermal control coating.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A universal thermal control coating pretreatment agent, comprising a silane coupling agent, tetraethyl orthosilicate, boric acid, ethyl acetoacetate, and a solvent;

[0007] The mass ratio of silane coupling agent, tetraethyl orthosilicate, boric acid and ethyl acetoacetate is (100-150):(50-100):(1-10):(10-30);

[0008] The silane coupling agent has an amino group and an (ethoxy group or a methoxy group).

[0009] The silane coupling agent is any one or more of KH550 and CH-792.

[0010] The solvent is one or more of ethanol, methanol, ethyl acetate and butyl acetate.

[0011] The mass ratio of the silane coupling agent, tetraethyl orthosilicate, boric acid and ethyl acetoacetate is 125:70:5:20.

[0012] The mass concentration of the silane coupling agent is 100-150 g / L, the mass concentration of tetraethyl orthosilicate is 50-100 g / L, the mass concentration of boric acid is 1-10 g / L, and the mass concentration of ethyl acetoacetate is 10-30 g / L.

[0013] A method for preparing a universal thermal control coating pretreatment agent, comprising:

[0014] Add silane coupling agent, tetraethyl orthosilicate, boric acid and ethyl acetoacetate in a mass ratio of (100-150):(50-100):(1-10):(10-30) to the solvent, condense and reflux with stirring at 60-70°C until completely dissolved.

[0015] A method for using a universal thermal control coating pretreatment agent, comprising:

[0016] The gold-plated, silver-plated or nickel-plated surface of the metal substrate is degreased and cleaned to obtain a clean surface;

[0017] Treat the clean surface with any of the above-mentioned pretreatment agents at 10 to 30° C. for 15 to 25 minutes to obtain a surface-dried base film;

[0018] A thermal control coating is applied to the surface of the base film.

[0019] The total mass concentration of the silane coupling agent, tetraethyl orthosilicate, boric acid and ethyl acetoacetate in the pretreatment agent is 5% to 10%.

[0020] The treatment method is dipping, spraying or brushing.

[0021] Through creative research, it was found that when silane coupling agents with amino groups and (ethoxy or methoxy groups) and tetraethyl orthosilicate are in the presence of boric acid, the silane coupling agent, tetraethyl orthosilicate and boric acid react with each other to form a uniform nano-scale organic-inorganic hybrid film with strong adhesion on the surface of the metal substrate. The film layer is uniform and dense, and has both hydroxyl and amino functional groups, which increases the types of functional groups required for combining with different thermal control coatings and greatly enhances the bonding strength of subsequent coatings with metal substrates.

[0022] At the same time, among the reactants of silane coupling agent, tetraethyl orthosilicate and boric acid, the ethoxy / methoxy group of the silane coupling agent is hydrolyzed to form a hydroxyl group, and the hydroxyl groups of the silane coupling agent and boric acid can react with the hydroxyl group after the hydrolysis of tetraethyl orthosilicate.

[0023] In addition to the exogroups participating in the reaction, the residual hydroxyl groups of silane coupling agent, tetraethyl orthosilicate, and boric acid can react with the thermal control coating, thereby improving the bonding strength with the thermal control coating, and the residual hydroxyl groups also increase the bonding strength with the metal substrate. The silane coupling agent also introduces amino groups, which increases the versatility of the thermal control coating surface of different materials. Boric acid introduces a large number of hydroxyl groups, and at the same time, B has a pair of lone pairs of electrons, which can chelate with the metal surface, thereby improving the bonding strength between the film and the metal substrate.

[0024] At the same time, the addition of ethyl acetoacetate can inhibit the self-polymerization of the three reactants, namely, silane coupling agent, tetraethyl orthosilicate and boric acid, thereby improving the stability and environmental adaptability of the treating agent and facilitating actual production and use.

[0025] The present application ensures the bonding strength of the formed film to the metal substrate and the thermal control coating by setting the mass ratio of silane coupling agent, tetraethyl orthosilicate and boric acid. Among them, when the content of silane coupling agent is too little, the versatility of the bonding strength of the thermal control coating is poor. When the content of silane coupling agent is too much, gelation occurs during the solution reaction. When the content of tetraethyl orthosilicate is too little, the base film is oily and has poor film-forming properties. When the content of tetraethyl orthosilicate is too much, the base film is easy to crack and has poor film-forming properties. When the content of boric acid is too little, the base film has poor film-forming properties. When the content of boric acid is too much, the coating has poor bonding strength.

[0026] In summary, this application at least includes the following beneficial technical effects:

[0027] The pretreatment agent of the present invention is non-toxic and environmentally friendly, does not contain phosphates and heavy metal ions, has excellent performance, and can greatly improve the bonding strength of the thermal control coating sprayed on the surface after metal gold plating, silver plating or nickel plating. The treatment agent of the present invention can omit traditional grinding, sandblasting and other processes, has a short treatment time, and is convenient for large-scale actual production use. DETAILED DESCRIPTION

[0028] The present invention will be further described below by way of examples.

[0029] A preparation method of a general thermal control coating pretreatment agent is as follows:

[0030] Add KH550 (silane coupling agent), tetraethyl orthosilicate, boric acid and ethyl acetoacetate in a mass ratio of (100-150):(50-100):(1-10):(10-30) to ethanol solvent, condense and reflux at 60-70°C and stir until completely dissolved.

[0031] A method for using a universal thermal control coating pretreatment agent, comprising:

[0032] The gold-plated, silver-plated or nickel-plated surface of the metal substrate is degreased and cleaned to obtain a clean surface;

[0033] The pretreatment agent obtained by the above preparation method is further diluted with ethanol solvent until the total mass concentration of KH550, tetraethyl orthosilicate, boric acid, and ethyl acetoacetate in the pretreatment agent is 5% to 10% (5% in this embodiment) to obtain a diluted pretreatment agent. The diluted pretreatment agent is dip-coated, sprayed, or brushed on a clean surface at 10 to 30° C. (normal temperature) and 60% RH. The spraying amount is 150 to 200 g / m 2 (160), drying for 15 to 25 minutes to obtain a surface-dried base film;

[0034] Apply thermal control coating on the surface of the base film, and the spraying amount of epoxy resin thermal control coating is 50-80g / m 2 , or silicone rubber thermal control coating spraying amount 120~200g / m 2 In the following examples and comparative examples, 150 g / m 2 Silicone rubber thermal control coating and 70g / m 2 The epoxy thermal control coating was subjected to a bonding strength test and the surface was dried for 48 hours and the surface was dried for 48 hours to obtain the final product.

[0035] The difference between Examples 1-5 is that the mass concentrations of KH550, tetraethyl orthosilicate, boric acid, and ethyl acetoacetate in the pretreatment agent are different, and their mass ratios are as follows:

[0036] Example 1

[0037] A metal gold plating, silver plating, nickel plating coating pretreatment agent, composed of the following mass concentrations of raw materials:

[0038]

[0039] Ethanol Residue

[0040] Example 2

[0041] A metal gold plating, silver plating, nickel plating coating pretreatment agent, composed of the following mass concentrations of raw materials:

[0042]

[0043] Ethanol Residue

[0044] Example 3

[0045] A metal gold plating, silver plating, nickel plating coating pretreatment agent, composed of the following mass concentrations of raw materials:

[0046]

[0047] Ethanol Residue

[0048] Example 4

[0049] A metal gold plating, silver plating, nickel plating coating pretreatment agent, composed of the following mass concentrations of raw materials:

[0050]

[0051] Ethanol Residue

[0052] Example 5

[0053] A metal gold plating, silver plating, nickel plating coating pretreatment agent, composed of the following mass concentrations of raw materials:

[0054] KH550 125g / L

[0055] Ethyl orthosilicate 70g / L

[0056] Boric acid 5g / L

[0057] Ethanol Residue

[0058] Whitening, cracking

[0059] Comparative Example 1

[0060] The difference from Example 1 is that:

[0061] Replace the KH550 with a KH560 of equal quality.

[0062] Comparative Example 2

[0063] The difference from Example 1 is that:

[0064] Replace the boric acid with an equal amount of hydrochloric acid.

[0065] When the pretreatment agent obtained in this example was applied to a clean surface, the pretreatment agent failed to form a film.

[0066] Comparative Example 3

[0067] The difference from Example 1 is that:

[0068] The content ratio of the silane coupling agent is 80g / L.

[0069] When the pretreatment agent obtained in this example is applied to a clean surface, the epoxy resin thermal control coating has poor bonding strength.

[0070] Table 1 Comparative Example 3 Pretreatment Agent Conventional Performance Test Results

[0071]

[0072] Comparative Example 4

[0073] The difference from Example 1 is that:

[0074] The content ratio of the silane coupling agent is 170g / L.

[0075] The pretreatment agent solution obtained in this example undergoes gelation during the reaction process, so the pretreatment agent cannot be sprayed to form a film.

[0076] Comparative Example 5

[0077] The difference from Example 1 is that:

[0078] The content ratio of ethyl orthosilicate is 30g / L.

[0079] When the pretreatment agent obtained in this example is applied to a clean surface, the base film is in an oily state and has poor film-forming properties, which does not meet the requirements, and the thermal control coating is no longer sprayed.

[0080] Comparative Example 6

[0081] The difference from Example 1 is that:

[0082] The content ratio of ethyl orthosilicate is 120g / L.

[0083] When the pretreatment agent obtained in this embodiment is applied to a clean surface, the base film is prone to cracking and has poor film-forming properties, which does not meet the requirements, and the thermal control coating is no longer sprayed.

[0084] Comparative Example 7

[0085] The difference from Example 1 is that:

[0086] The content of boric acid is 0.2g / L.

[0087] When the pretreatment agent obtained in this example is applied to a clean surface, the base film is in an oily state and has poor film-forming properties, which does not meet the requirements, and the thermal control coating is no longer sprayed.

[0088] Comparative Example 8

[0089] The difference from Example 1 is that:

[0090] The content of boric acid is 12g / L.

[0091] When the pretreatment agent obtained in this example is applied to a clean surface, the silicone rubber thermal control coating has poor bonding strength.

[0092] Table 2 Comparative Example 8 Pretreatment Agent Conventional Performance Test Results

[0093]

[0094] The performance comparison test of the final products obtained from the above embodiments and comparative examples of the present invention was carried out with reference to relevant national standards. The test results of embodiments 1-4 are shown in Table 1 below:

[0095] Table 3. Results of conventional performance test of pretreatment agents in Examples 1-4

[0096]

[0097]

[0098] Test data of Example 5, Comparative Example 1 and Comparative Example 2 When the pretreatment agent of Example 5 is applied to a clean surface, when the ambient humidity is higher than 60% RH, the base film is prone to cracking and whitening.

[0099] When the pretreatment agent obtained in Comparative Example 1 was applied to a clean surface, the cross-cutting bonding strength of the silicone rubber thermal control coating was higher than level 3. When the pretreatment agent obtained in Comparative Example 2 was applied to a clean surface, the pretreatment agent could not form a film.

[0100] According to Examples 1-4 and the test results, the thermal control coating film has a cross-cut test bonding strength of level 0, and has no cracks or bubbles in the damp heat test and the thermal cycle test.

[0101] According to the test results of Example 1 and Example 5, the base film of Example 1 can maintain good coating adhesion in the humidity range of 10% to 80% RH. The test results of Example 5 show that the base film is prone to cracking and whitening when the humidity is higher than 60% RH, and the coating film adhesion is poor, indicating that the environmental adaptability of Example 5 is poor.

[0102] According to Example 1 and Comparative Example 1 and the test results, the level of the paint film cross-cutting test result of the final product obtained in Comparative Example 1 is higher than that of Example 1, and the result of the paint film thermal cycle test shows that bulging and bubbles appear on the coating, that is, the bonding strength between the final product of Comparative Example 1 and the metal substrate is lower than that of Example 1. Therefore, under the coordinated action of the silane coupling agent defined in the present application with tetraethyl orthosilicate and boric acid, the metal substrate and the thermal control coating have better bonding strength.

[0103] According to Example 1 and Comparative Example 2 and the test results, the pretreatment agent obtained in Comparative Example 2 cannot form a film, indicating that hydrochloric acid is not applicable under the specific raw material ratio of the present application.

[0104] Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A universal thermal control coating pretreatment agent, characterized in that: Including silane coupling agent, tetraethyl orthosilicate, boric acid, ethyl acetoacetate, solvent; The mass ratio of silane coupling agent, tetraethyl orthosilicate, boric acid and ethyl acetoacetate is (100-150):(50-100):(1-10):(10-30), and the total mass concentration of silane coupling agent, tetraethyl orthosilicate, boric acid and ethyl acetoacetate in the pretreatment agent is 5%-10%; The silane coupling agent has both an amino group and an ethoxy group, or both an amino group and a methoxy group.

2. A universal thermal control coating pretreatment agent according to claim 1, characterized in that: The silane coupling agent is any one or more of KH550 and CH-792.

3. A universal thermal control coating pretreatment agent according to claim 1, characterized in that: The solvent is any one or more of ethanol, methanol, ethyl acetate and butyl acetate.

4. A universal thermal control coating pretreatment agent according to claim 1, characterized in that: The mass ratio of the silane coupling agent, tetraethyl orthosilicate, boric acid and ethyl acetoacetate is 125:70:5:

20.

5. A universal thermal control coating pretreatment agent according to claim 1, characterized in that: In the pretreatment agent, the mass concentration of the silane coupling agent is 100-150 g / L, the mass concentration of tetraethyl orthosilicate is 50-100 g / L, the mass concentration of boric acid is 1-10 g / L, and the mass concentration of ethyl acetoacetate is 10-30 g / L.

6. A method for preparing a universal thermal control coating pretreatment agent according to any one of claims 1 to 5, characterized in that: include: Add silane coupling agent, tetraethyl orthosilicate, boric acid, and ethyl acetoacetate in a mass ratio of (100-150):(50-100):(1-10):(10-30) to the solvent, condense and reflux at 60-70°C and stir until completely dissolved; The total mass concentration of silane coupling agent, tetraethyl orthosilicate, boric acid and ethyl acetoacetate in the pretreatment agent is 5% to 10%.

7. A method for using a universal thermal control coating pretreatment agent, characterized in that: include: The gold-plated, silver-plated or nickel-plated surface of the metal substrate is degreased and cleaned to obtain a clean surface; Treat the clean surface with the pretreatment agent according to any one of claims 1 to 5 at 10 to 30° C. for 15 to 25 minutes to obtain a surface-dried base film; A thermal control coating is applied to the surface of the base film.

8. The method for using a universal thermal control coating pretreatment agent according to claim 7, characterized in that: The treatment method is dipping, spraying or brushing.

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