A heat-resistant coating with heat-applying properties and its preparation method

Abstract

This invention relates to the field of heat-resistant coatings, and more particularly to a heat-resistant coating for application under heat, comprising the following components by weight: 50-70 parts potassium silicate aqueous solution, 10-25 parts zinc oxide, 5-15 parts lanthanum-cerium mixture, 0.1-1 part defoamer, 0.5-2.5 parts silane coupling agent, 0.1-1 part hydroxypropyl methylcellulose, 0.1-2 parts hydroxyethyl cellulose, 0.1-1 part wetting and dispersing agent, 2-10 parts water, and 1-5 parts silicon tripolyphosphate. This invention uses potassium silicate aqueous solution as the inorganic film-forming agent and silicon tripolyphosphate as the curing agent, enabling cross-linking and curing at high temperatures to form an inorganic heat-resistant coating. Zinc oxide reacts with the silanol groups in the potassium silicate aqueous solution to form a dense complex on the surface of steel components. Both silane coupling agents and defoamers are silane-based substances. They hydrolyze in potassium silicate aqueous solution to form free Si-OH, which can react with the active silanol groups in potassium silicate aqueous solution to increase coating density, and can also form chemical bonds with the steel substrate to improve coating adhesion.

Description

Technical Field

[0001] This invention relates to the field of heat-resistant coatings, and more particularly to a heat-resistant coating with heat-applying properties and its preparation method. Background Technology

[0002] Heat-resistant coatings, also known as high-temperature resistant coatings, generally refer to functional coatings that maintain good physical and mechanical properties at ambient temperatures above 200℃, without cracking, peeling, or flaking, allowing the protected substrate to function normally. Based on the film-forming substances, heat-resistant coatings are divided into three main categories: organic heat-resistant coatings, inorganic heat-resistant coatings, and organic-inorganic composite heat-resistant coatings. Organic heat-resistant coatings mainly use four types of film-forming resins: heterocyclic polymers, organosilicon, organofluorine, and organotitanium. Inorganic heat-resistant coatings mainly use four types of film-forming substances: ethyl silicate, silica sol, silicates, and phosphates. For example, Chinese patent CN 115418125A uses sodium silicate aqueous solution as the film-forming substance, composed of a mixture of organic and inorganic film-forming substances. Another example is Chinese patent CN 116162367A, which uses an inorganic modified silicone resin composed of isopropanol, silicon dioxide, and aluminum oxide, with the organosilicon resin serving as the inorganic-organic composite film-forming substance.

[0003] During long-term high-temperature service, the heat-resistant coatings on the surfaces of steel chimneys, high-temperature pipelines, petroleum cracking units, high-temperature furnaces, and high-temperature reaction equipment in chemical plants, coking plants, and gas plants can discolor, crack, peel, and detach, affecting their durability and protective effectiveness. Therefore, thermal protection maintenance is necessary for in-service high-temperature steel components. However, existing organic, inorganic, and organic-inorganic composite coatings are all applied at room temperature. When applied to high-temperature steel components, they crack and peel off, failing to adhere firmly and thus failing to provide adequate protection. Summary of the Invention

[0004] To address the problem that existing heat-resistant coatings are prone to cracking or peeling under high-temperature conditions after being applied at room temperature, this invention provides a heat-resistant coating with heat-applying properties, comprising the following components by weight: 50-70 parts potassium silicate aqueous solution, 10-25 parts zinc oxide, 5-15 parts lanthanum-cerium mixture, 0.1-1 part defoamer, 0.5-2.5 parts silane coupling agent, 0.1-1 part hydroxypropyl methylcellulose, 0.1-2 parts hydroxyethyl cellulose, 0.1-1 part wetting and dispersing agent, 2-10 parts water, and 1-5 parts silicon tripolyphosphate.

[0005] Specifically, the potassium silicate aqueous solution has a Baumé degree of 40 and a modulus of 3.3; the lanthanum-cerium mixture is a mixture of lanthanum oxide and cerium oxide powders in a mass ratio of 1:2, with a powder diameter of 10–30 μm; the defoamer is a modified polydimethylsiloxane emulsion; the silane coupling agent is methyltrimethoxysilane; and the wetting and dispersing agent is alkylphenol ethoxide or sodium alkylbenzene sulfonate.

[0006] The preparation method of the heat-resistant coating of the present invention includes the following operations: weigh each substance according to the weight parts, stir the potassium silicate aqueous solution and water with a stirrer, and add silane coupling agent, zinc oxide, lanthanum-cerium mixture, hydroxypropyl methylcellulose, hydroxyethylcellulose, wetting and dispersing agent and defoamer to the mixed liquid in sequence during the stirring process. After stirring evenly, add silicon tripolyphosphate and stir to mix.

[0007] This invention relates to a heat-resistant coating with a heat-coating capability. Potassium silicate aqueous solution is used as the inorganic film-forming agent, and silicon tripolyphosphate is used as the curing agent. Cross-linking and curing can be achieved at high temperatures to form an inorganic heat-resistant coating. Zinc oxide reacts with the silanol groups in the potassium silicate aqueous solution to form a dense complex on the surface of the steel component. The silane coupling agent and defoamer are both silanes, which hydrolyze in the potassium silicate aqueous solution to form free Si-OH. Si-OH can react with the active silanol groups in the potassium silicate aqueous solution to increase the coating density, and can also chemically bond with the steel substrate to improve the coating adhesion. Hydroxypropyl methylcellulose and hydroxyethyl cellulose act as thickeners to adjust the viscosity of the coating. The lanthanum-cerium mixture mainly improves the coating adhesion and heat resistance, especially during high-temperature coating processes, it can reduce the internal stress generated by the cross-linking reaction between the potassium silicate aqueous solution and silicon tripolyphosphate, preventing coating cracking. Compared with existing room temperature heat-resistant coatings, this invention comprehensively utilizes the synergistic effect of various fillers and additives to cure into a film on the surface of high-temperature steel substrates at 50℃~150℃. The coating can be applied to in-service equipment without shutdown, thus solving the problem of surface heat protection for high-temperature equipment. Attached Figure Description

[0008] Figure 1 This is a SEM image of the heat-resistant coating of Example 1 after it has been applied and cured on a steel substrate at 150°C. Figure 2 This is a SEM image of the heat-resistant coating of Comparative Example 1 after it has been applied and cured on a steel substrate at 150°C. Detailed Implementation

[0009] The present invention will be described below with reference to examples. These examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0010] Example 1

[0011] A heat-resistant coating for application under heat includes the following components by weight: 60 parts potassium silicate aqueous solution, 19 parts zinc oxide, 10 parts lanthanum-cerium mixture, 0.5 parts modified polydimethylsiloxane emulsion, 1.5 parts methyltrimethoxysilane coupling agent, 0.5 parts hydroxypropyl methylcellulose, 0.5 parts hydroxyethyl cellulose, 1 part sodium alkylbenzene sulfonate, 5 parts water, and 2 parts silicon tripolyphosphate. The potassium silicate aqueous solution has a Baumé degree of 40 and a modulus of 3.3; the lanthanum-cerium mixture is a mixture of lanthanum oxide and cerium oxide powders in a mass ratio of 1:2, with a powder diameter of 10–30 μm.

[0012] The preparation method of the heat-resistant coating with heat coating in this embodiment includes the following steps: weigh each substance according to the weight parts, stir the potassium silicate aqueous solution and water with a stirrer at room temperature, and add methyltrimethoxysilane coupling agent, zinc oxide powder, lanthanum-cerium mixture, hydroxypropyl methylcellulose, hydroxyethylcellulose, sodium alkylbenzene sulfonate and modified polydimethylsiloxane emulsion to the mixed liquid in sequence during the stirring process. After stirring evenly, add silicon tripolyphosphate and stir to complete the coating as soon as possible with heat coating.

[0013] Example 2

[0014] A heat-resistant coating for application under heat includes the following components by weight: 50 parts potassium silicate aqueous solution, 25 parts zinc oxide, 5 parts lanthanum-cerium mixture, 1 part modified polydimethylsiloxane emulsion, 2.5 parts methyltrimethoxysilane coupling agent, 0.1 parts hydroxypropyl methylcellulose, 0.1 parts hydroxyethylcellulose, 0.1 parts alkylphenol ethoxide, 10 parts water, and 5 parts silicon tripolyphosphate. The potassium silicate aqueous solution has a Baumé degree of 40 and a modulus of 3.3; the lanthanum-cerium mixture is a mixture of lanthanum oxide and cerium oxide powders in a mass ratio of 1:2, with a powder diameter of 10–30 μm.

[0015] The preparation method of the heat-resistant coating with heat coating in this embodiment includes the following steps: weigh each substance according to the weight parts, stir the potassium silicate aqueous solution and water with a stirrer at room temperature, and add methyltrimethoxysilane coupling agent, zinc oxide powder, lanthanum-cerium mixture, hydroxypropyl methylcellulose, hydroxyethylcellulose, alkylphenol ethoxide, and modified polydimethylsiloxane emulsion to the mixed liquid in sequence during the stirring process. After stirring evenly, add silicon tripolyphosphate, and complete the coating as soon as possible with heat after stirring and mixing.

[0016] Example 3

[0017] A heat-resistant coating for application under heat includes the following components by weight: 70 parts potassium silicate aqueous solution, 10 parts zinc oxide, 15 parts lanthanum-cerium mixture, 0.1 parts modified polydimethylsiloxane emulsion, 0.5 parts methyltrimethoxysilane coupling agent, 1 part hydroxypropyl methylcellulose, 2 parts hydroxyethylcellulose, 0.5 parts sodium alkylbenzene sulfonate, 2 parts water, and 1 part silicon tripolyphosphate. The potassium silicate aqueous solution has a Baumé degree of 40 and a modulus of 3.3; the lanthanum-cerium mixture is a mixture of lanthanum oxide and cerium oxide powders in a mass ratio of 1:2, with a powder diameter of 10–30 μm.

[0018] The preparation method of the heat-resistant coating with heat coating in this embodiment includes the following steps: weigh each substance according to the weight parts, stir the potassium silicate aqueous solution and water with a stirrer at room temperature, and add methyltrimethoxysilane coupling agent, zinc oxide powder, lanthanum-cerium mixture, hydroxypropyl methylcellulose, hydroxyethylcellulose, sodium alkylbenzene sulfonate and modified polydimethylsiloxane emulsion to the mixed liquid in sequence during the stirring process. After stirring evenly, add silicon tripolyphosphate and stir to complete the coating as soon as possible with heat coating.

[0019] Comparative Example 1

[0020] A heat-resistant coating comprises the following substances in parts by weight: 60 parts of potassium silicate aqueous solution, 0.5 parts of modified polydimethylsiloxane emulsion, 1.5 parts of methyltrimethoxysilane coupling agent, 0.5 parts of hydroxypropyl methylcellulose, 0.5 parts of hydroxyethyl cellulose, 1 part of sodium alkylbenzene sulfonate, 5 parts of water, and 2 parts of MDI-50 curing agent. The potassium silicate aqueous solution has a Baume degree of 40 and a modulus of 3.3.

[0021] The preparation method of the heat-resistant coating with heat coating in this embodiment includes the following steps: weigh each substance according to the weight parts, stir the potassium silicate aqueous solution and water with a stirrer at room temperature, and add methyltrimethoxysilane coupling agent, hydroxypropyl methylcellulose, hydroxyethylcellulose, sodium alkylbenzene sulfonate and modified polydimethylsiloxane emulsion to the mixed liquid in sequence during the stirring process. After stirring evenly, add silicon tripolyphosphate and complete the coating as soon as possible after stirring and mixing.

[0022] Figure 1 This is a SEM image of the heat-resistant coating of Example 1 after curing on a steel substrate at 150°C. The image shows that the heat-resistant coating after heat application at 150°C exhibits a continuous structure, forming a dense coating. Figure 2 The image shows a SEM image of the heat-resistant coating of Comparative Example 1 after curing on a steel substrate at 150°C. The image shows that the heat-resistant coating after heat application at 150°C has a discontinuous structure, with obvious dispersion of components, and no dense coating is formed.

[0023] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A heat-resistant coating with heat-applying properties, characterized in that, It comprises the following substances in parts by weight: 50-70 parts of potassium silicate aqueous solution, 10-25 parts of zinc oxide, 5-15 parts of lanthanum-cerium mixture, 0.1-1 part of defoamer, 0.5-2.5 parts of silane coupling agent, 0.1-1 part of hydroxypropyl methylcellulose, 0.1-2 parts of hydroxyethylcellulose, 0.1-1 part of wetting and dispersing agent, 2-10 parts of water, and 1-5 parts of silicon tripolyphosphate.

2. The heat-resistant coating with heat-applying properties according to claim 1, characterized in that, The potassium silicate aqueous solution has a Baumé degree of 40 and a modulus of 3.

3.

3. The heat-resistant coating with heat-applying properties according to claim 1, characterized in that, The lanthanum-cerium mixture is a mixture of lanthanum oxide and cerium oxide powders in a mass ratio of 1:2, with a powder diameter of 10–30 μm.

4. The heat-resistant coating with heat-applying properties according to claim 1, characterized in that, The defoamer is a modified polydimethylsiloxane emulsion.

5. The heat-resistant coating with heat-applying properties according to claim 1, characterized in that, The silane coupling agent is methyltrimethoxysilane.

6. The heat-resistant coating with heat-applying properties according to claim 1, characterized in that, The wetting and dispersing agent is alkylphenol ethoxide or sodium alkylbenzene sulfonate.

7. A method for preparing a heat-resistant coating with heat-applying properties as described in any one of claims 1 to 6, characterized in that, The process includes the following steps: Weigh each substance according to its weight, stir the potassium silicate aqueous solution and water with a mixer, and add the silane coupling agent, zinc oxide, lanthanum-cerium mixture, hydroxypropyl methylcellulose, hydroxyethylcellulose, wetting and dispersing agent and defoamer to the mixed liquid in sequence during the stirring process. After stirring evenly, add silicon tripolyphosphate and stir to mix.

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