Uniform curing powder coating special for suction coating of inner wall of pipe fitting and coating method thereof

Abstract

The invention discloses a special uniform curing powder coating for suction coating of the inner wall of a pipe fitting and a coating method of the special uniform curing powder coating, relates to the technical field of pipeline anti-corrosion coatings, and aims to solve the problem that the whole anti-corrosion performance of the pipe fitting does not reach the standard due to non-uniform coating and incomplete curing in the coating of the inner wall of the existing pipe fitting. The paint is composed of 400 g of one-step epoxy resin, 200 g of two-step epoxy resin, 80 g of a curing agent, 10 g of an auxiliary agent, 28 g of pigment, 3 g of an accelerant and 279 g of filler. The epoxy value of the one-step method epoxy resin is 0.4 to 0.5 eq / 100g; the epoxy value of the two-step method epoxy resin is 0.1 to 0.2 eq / 100g; the curing agent is an amine curing agent, and a microcapsule type latent accelerator accounting for 5-10% of the mass of the curing agent is dispersed in the curing agent. The powder coating has the advantages that the flowability and the leveling property of the powder coating are effectively adjusted, the sagging phenomenon is reduced, the curing time is shortened, and uniform curing is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline anti-corrosion coatings, and more particularly to a uniformly solidified powder coating specially used for suction coating of inner walls of pipe fittings and a coating method thereof. Background Art

[0002] In modern industry, pipe fittings are widely used in petrochemical, water supply and drainage, gas transmission, and other systems. The quality of their inner protective coatings is directly related to the service life of the pipe fittings and the safe operation of the system. Although powder coating technology for pipe fitting inner walls has been widely used, the deposition of traditional powder coating particles varies significantly during the suction coating process, affected by gravity, airflow distribution, and the shape of the pipe inner wall. When suction coating is applied to vertically positioned pipe fittings, sagging is likely to occur. When suction coating is applied horizontally, the coating is too thick near the suction port and too thin at the distal end, making it difficult to meet the stringent engineering requirements for coating uniformity.

[0003] However, due to the special structure of pipe fittings, the powder coating cannot be completely melted and cross-linked in the middle area during the conventional curing process due to low heat conduction efficiency and uneven heating. The middle area often still needs secondary heat curing, which not only increases energy consumption and time costs, but may also affect the performance of the pipe fittings. In addition, to ensure the leveling of the powder coating on the inner wall of the pipe fitting, most existing coating schemes require the pipe fittings to be heated in advance, which increases equipment investment and process complexity. At the same time, the welds and threaded parts of the pipe fittings are irregular in shape and have large airflow disturbances, making it difficult for the powder coating to fully deposit and adhere. The weak coating formed is easily damaged and corroded under the erosion of complex media, resulting in the overall corrosion resistance of the pipe fittings not meeting the standards.

[0004] In view of this, we propose a uniformly cured powder coating specially used for suction coating of the inner wall of pipe fittings and a coating method thereof. Summary of the Invention

[0005] The purpose of the present invention is to provide a special uniform curing powder coating for the inner wall of pipe fittings and a coating method thereof, aiming to solve the problems of uneven coating and incomplete curing in the existing inner wall coating of pipe fittings, resulting in the overall corrosion resistance of the pipe fittings not meeting the standards.

[0006] To solve the above technical problems, the present invention provides the following technical solution: a uniformly cured powder coating specially used for suction coating on the inner wall of a pipe fitting, wherein 1000g of the powder coating comprises 400g of a one-step epoxy resin, 200g of a two-step epoxy resin, 80g of a curing agent, 10g of an auxiliary agent, 28g of a pigment, 3g of an accelerator, and 279g of a filler; The epoxy value of the one-step epoxy resin is 0.4-0.5eq / 100g, and the relative molecular mass distribution is between 300-700; The epoxy value of the two-step epoxy resin is 0.1-0.2eq / 100g, and the relative molecular mass distribution is between 1500-3000; The curing agent is an amine curing agent, and a microcapsule latent accelerator accounting for 5-10% of the mass of the curing agent is dispersed in the curing agent; The auxiliary agent is composed of a leveling agent, a degassing agent and a dispersant in a ratio of 5:3:2, wherein the leveling agent is an acrylic polymer, the degassing agent is an organic silicone compound, and the surface of the degassing agent is loaded with nano-titanium dioxide accounting for 3-8% of its mass, and the dispersant is a high molecular weight block copolymer; The accelerator is an imidazole curing accelerator, and the accelerator is surface-treated by a silane coupling agent; The filler consists of 200g of thermally conductive filler and 79g of barium sulfate, wherein the thermally conductive filler is one of boron nitride or aluminum oxide with a particle size distribution between 1-5μm, and the surface of the thermally conductive filler is grafted with graphene nanosheets accounting for 1-3% of its mass and with a sheet thickness of ≤10nm, the particle size of the barium sulfate is 10-20μm, the whiteness is ≥95%, and the barium sulfate is surface-treated with an aluminate coupling agent.

[0007] Preferably, the amine curing agent is a compound of alicyclic amine and aromatic amine, and the mass ratio of the two is 1:1-3:1.

[0008] Preferably, the surface of the nano-titanium dioxide is modified with organosiloxane, and the volatile matter of the degassing agent is ≤0.5wt%.

[0009] Preferably, the microcapsule latent promoter uses urea-formaldehyde resin as a shell material and covers a 2-methylimidazole core.

[0010] Preferably, the particle size of the microcapsule-type latent promoter is 1-4 μm, and the thickness of the urea-formaldehyde resin shell material is 0.1-0.5 μm.

[0011] Preferably, the amount of the silane coupling agent is 3-8% of the mass of the accelerator, and the particle size of the accelerator is ≤10 μm.

[0012] A coating method for applying a uniformly cured powder coating specifically for the inner wall of a pipe by suction coating is applicable to any of the above-mentioned uniformly cured powder coating specifically for the inner wall of a pipe by suction coating. The coating method comprises the following steps: S1. Clean and rust the surface of the pipe fittings to make them clean; S2. Place the prepared powder coating in the powder supply device, set the suction voltage of the suction coating equipment to 60-80kV, the suction coating time to 3-5min, and the pipe temperature to 200℃; S3, start the suction coating equipment to make the powder coating be adsorbed onto the inner wall of the pipe under the action of the electric field; S4. After the suction coating is completed, the residual heat of the pipe itself is used to cure the powder coating on the inner wall of the pipe to form a uniform and dense protective coating without the need for post-curing treatment.

[0013] Preferably, in the above step S1, after the surface of the pipe is cleaned and rust-removed, the surface is blown with clean compressed air, and dried at 80-120° C. for 30-60 minutes.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention adopts a specific ratio of one-step epoxy resin and two-step epoxy resin to adjust the fluidity and leveling properties of the powder coating, reduce sagging, and add thermally conductive fillers to improve the heat conduction efficiency inside the coating, ensuring uniform curing. The invention also adds a high-efficiency curing accelerator to reduce the curing temperature, shorten the curing time, achieve residual heat curing, optimize the suction coating voltage, suction coating time, and pipe temperature parameters, and further improve the coating uniformity.

[0015] The additives in the present invention are prepared by compounding a leveling agent, a degassing agent, and a dispersant in a ratio of 5:3:2. The acrylic leveling agent improves the surface flatness of the coating, the organic silicone degassing agent reduces bubbles in the coating, and the high molecular weight block copolymer dispersant promotes uniform dispersion of powder particles, thereby improving the leveling property of the coating during suction coating. The accelerator and the filler enhance the interfacial bonding force with the coating, thereby making the coating more firmly adhered to the inner wall of the pipe, especially to irregular parts such as welds and threads, thereby reducing coating damage and corrosion caused by medium erosion.

[0016] The microcapsule-type latent promoter in the present invention is stable at room temperature and releases the promoter after heating, accurately controlling the starting time of curing, avoiding premature curing during the suction coating process, and ensuring the uniformity of the coating. The barium sulfate in the filler improves the covering power and physical strength of the coating, and the thermally conductive filler grafted with graphene nanosheets further enhances the heat conduction efficiency. It is suitable for suction coating of the inner walls of pipes with different structures and has strong process adaptability.

[0017] The coating in the present invention can be cured by utilizing the waste heat of the pipe itself, eliminating the post-curing treatment step, reducing energy consumption and curing time, and eliminating the need for pre-heating the pipe to ensure leveling. This reduces equipment investment and process complexity, and shortens the overall coating cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the coating process of the present invention. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Example

[0020] A uniformly cured powder coating specifically for pipe inner wall suction coating, wherein 1000g of the powder coating comprises 400g of one-step epoxy resin, 200g of two-step epoxy resin, 80g of curing agent, 10g of auxiliary agent, 28g of pigment, 3g of accelerator, and 279g of filler; The epoxy value of one-step epoxy resin is 0.4-0.5eq / 100g, and the relative molecular mass distribution is between 300-700; The epoxy value of the two-step epoxy resin is 0.1-0.2eq / 100g, and the relative molecular mass distribution is between 1500-3000; The curing agent is an amine curing agent, and a microcapsule latent accelerator accounting for 5-10% of the mass of the curing agent is dispersed in the curing agent; The additive is composed of a leveling agent, a degassing agent and a dispersant in a ratio of 5:3:2. The leveling agent is an acrylic polymer, the degassing agent is an organic silicone compound, and the surface of the degassing agent is loaded with nano-titanium dioxide accounting for 3-8% of its mass. The dispersant is a high molecular weight block copolymer. The accelerator is an imidazole curing accelerator, and the accelerator is surface treated with a silane coupling agent; The filler consists of 200g of thermally conductive filler and 79g of barium sulfate, wherein the thermally conductive filler is boron nitride with a particle size distribution between 1-5μm, and graphene nanosheets accounting for 1-3% of the mass of the thermally conductive filler and with a sheet thickness of ≤10nm are grafted on the surface of the thermally conductive filler. The particle size of the barium sulfate is 10-20μm, the whiteness is ≥95%, and the barium sulfate is surface-treated with an aluminate coupling agent.

[0021] Furthermore, the amine curing agent is a compound of alicyclic amine and aromatic amine, and the mass ratio of the two is 1:1-3:1.

[0022] Furthermore, the surface of the nano-titanium dioxide is modified with organic siloxane, and the volatile matter of the degassing agent is ≤0.5wt%.

[0023] Furthermore, the microcapsule latent accelerator uses urea-formaldehyde resin as a shell material and covers a 2-methylimidazole core.

[0024] Furthermore, the particle size of the microcapsule latent promoter is 1-4 μm, and the thickness of the urea-formaldehyde resin shell material is 0.1-0.5 μm.

[0025] Furthermore, the amount of the silane coupling agent is 3-8% of the mass of the accelerator, and the particle size of the accelerator is ≤10 μm.

[0026] A coating method for applying a special uniformly cured powder coating to the inner wall of a pipe fitting by suction coating is applicable to any of the above-mentioned special uniformly cured powder coatings for the inner wall of a pipe fitting, and the coating method comprises the following steps: S1. Clean and rust the surface of the pipe fittings to make them clean; S2. Place the prepared powder coating in the powder supply device, set the suction voltage of the suction coating equipment to 60-80kV, the suction coating time to 3-5min, and the pipe temperature to 200℃; S3, start the suction coating equipment to make the powder coating be adsorbed onto the inner wall of the pipe under the action of the electric field; S4. After the suction coating is completed, the residual heat of the pipe itself is used to cure the powder coating on the inner wall of the pipe to form a uniform and dense protective coating without the need for post-curing treatment.

[0027] Furthermore, in the above step S1, after the surface of the pipe is cleaned and rust-removed, the surface is blown with clean compressed air and dried at 80-120° C. for 30-60 minutes. Example

[0028] This embodiment is basically the same as the first embodiment, except that alumina is used as the thermal conductive filler; A uniformly cured powder coating specifically for pipe inner wall suction coating, wherein 1000g of the powder coating comprises 400g of one-step epoxy resin, 200g of two-step epoxy resin, 80g of curing agent, 10g of auxiliary agent, 28g of pigment, 3g of accelerator, and 279g of filler; The epoxy value of one-step epoxy resin is 0.4-0.5eq / 100g, and the relative molecular mass distribution is between 300-700; The epoxy value of the two-step epoxy resin is 0.1-0.2eq / 100g, and the relative molecular mass distribution is between 1500-3000; The curing agent is an amine curing agent, and a microcapsule latent accelerator accounting for 5-10% of the mass of the curing agent is dispersed in the curing agent; The additive is composed of a leveling agent, a degassing agent and a dispersant in a ratio of 5:3:2. The leveling agent is an acrylic polymer, the degassing agent is an organic silicone compound, and the surface of the degassing agent is loaded with nano-titanium dioxide accounting for 3-8% of its mass. The dispersant is a high molecular weight block copolymer. The accelerator is an imidazole curing accelerator, and the accelerator is surface treated with a silane coupling agent; The filler consists of 200g of thermally conductive filler and 79g of barium sulfate, wherein the thermally conductive filler is aluminum oxide with a particle size distribution between 1-5μm, and graphene nanosheets accounting for 1-3% of the mass of the thermally conductive filler and with a sheet thickness of ≤10nm are grafted on the surface of the thermally conductive filler, the particle size of the barium sulfate is 10-20μm, the whiteness is ≥95%, and the barium sulfate is surface-treated with an aluminate coupling agent.

[0029] Furthermore, the amine curing agent is a compound of alicyclic amine and aromatic amine, and the mass ratio of the two is 1:1-3:1.

[0030] Furthermore, the surface of the nano-titanium dioxide is modified with organic siloxane, and the volatile matter of the degassing agent is ≤0.5wt%.

[0031] Furthermore, the microcapsule latent accelerator uses urea-formaldehyde resin as a shell material and covers a 2-methylimidazole core.

[0032] Furthermore, the particle size of the microcapsule latent promoter is 1-4 μm, and the thickness of the urea-formaldehyde resin shell material is 0.1-0.5 μm.

[0033] Furthermore, the amount of the silane coupling agent is 3-8% of the mass of the accelerator, and the particle size of the accelerator is ≤10 μm.

[0034] A coating method for applying a special uniformly cured powder coating to the inner wall of a pipe fitting by suction coating is applicable to any of the above-mentioned special uniformly cured powder coatings for the inner wall of a pipe fitting, and the coating method comprises the following steps: S1. Clean and rust the surface of the pipe fittings to make them clean; S2. Place the prepared powder coating in the powder supply device, set the suction voltage of the suction coating equipment to 60-80kV, the suction coating time to 3-5min, and the pipe temperature to 200℃; S3, start the suction coating equipment to make the powder coating be adsorbed onto the inner wall of the pipe under the action of the electric field; S4. After the suction coating is completed, the residual heat of the pipe itself is used to cure the powder coating on the inner wall of the pipe to form a uniform and dense protective coating without the need for post-curing treatment.

[0035] Furthermore, in the above step S1, after the surface of the pipe is cleaned and rust-removed, the surface is blown with clean compressed air and dried at 80-120° C. for 30-60 minutes.

[0036] The embodiments disclosed in the present invention are preferred embodiments, but are not limited to them. Ordinary technicians in this field can easily understand the spirit of the present invention based on the above embodiments and make different extensions and changes. As long as they do not deviate from the spirit of the present invention, they are all within the scope of protection of the present invention.

Claims

1. A uniformly cured powder coating specially used for pipe inner wall suction coating, characterized in that: The powder coating is composed of 400g of one-step epoxy resin, 200g of two-step epoxy resin, 80g of curing agent, 10g of auxiliary agent, 28g of pigment, 3g of accelerator and 279g of filler based on 1000g of the powder coating. The epoxy value of the one-step epoxy resin is 0.4-0.5eq / 100g, and the relative molecular mass distribution is between 300-700; The epoxy value of the two-step epoxy resin is 0.1-0.2eq / 100g, and the relative molecular mass distribution is between 1500-3000; The curing agent is an amine curing agent, and a microcapsule latent accelerator accounting for 5-10% of the mass of the curing agent is dispersed in the curing agent; The auxiliary agent is composed of a leveling agent, a degassing agent and a dispersant in a ratio of 5:3:2, wherein the leveling agent is an acrylic polymer, the degassing agent is an organic silicone compound, and the surface of the degassing agent is loaded with nano-titanium dioxide accounting for 3-8% of its mass, and the dispersant is a high molecular weight block copolymer; The accelerator is an imidazole curing accelerator, and the accelerator is surface-treated by a silane coupling agent; The filler consists of 200g of thermally conductive filler and 79g of barium sulfate, wherein the thermally conductive filler is one of boron nitride or aluminum oxide with a particle size distribution between 1-5μm, and the surface of the thermally conductive filler is grafted with graphene nanosheets accounting for 1-3% of its mass and with a sheet thickness of ≤10nm, the particle size of the barium sulfate is 10-20μm, the whiteness is ≥95%, and the barium sulfate is surface-treated with an aluminate coupling agent.

2. The uniformly cured powder coating specially used for pipe inner wall suction coating according to claim 1, characterized in that: The amine curing agent is a compound of alicyclic amine and aromatic amine, and the mass ratio of the two is 1:1-3:

1.

3. The uniformly cured powder coating specially used for pipe inner wall suction coating according to claim 1, characterized in that: The surface of the nano-titanium dioxide is modified with organic siloxane, and the volatile matter of the degassing agent is less than or equal to 0.5 wt %.

4. The uniformly cured powder coating specially used for pipe inner wall suction coating according to claim 1, characterized in that: The microcapsule latent accelerator uses urea-formaldehyde resin as a shell material and covers a 2-methylimidazole core.

5. The uniformly cured powder coating specially used for pipe inner wall suction coating according to claim 4, characterized in that: The particle size of the microcapsule latent promoter is 1-4 μm, and the thickness of the urea-formaldehyde resin shell material is 0.1-0.5 μm.

6. The uniformly cured powder coating specially used for pipe inner wall suction coating according to claim 1, characterized in that: The amount of the silane coupling agent is 3-8% of the mass of the accelerator, and the particle size of the accelerator is ≤10 μm.

7. A method for applying a uniformly cured powder coating specifically for pipe inner wall by suction coating, the method being applicable to the uniformly cured powder coating specifically for pipe inner wall by suction coating as claimed in any one of claims 1 to 6, characterized in that: The coating method comprises the following steps: S1. Clean and rust the surface of the pipe fittings to make them clean; S2. Place the prepared powder coating in the powder supply device, set the suction voltage of the suction coating equipment to 60-80kV, the suction coating time to 3-5min, and the pipe temperature to 200℃; S3, start the suction coating equipment to make the powder coating be adsorbed onto the inner wall of the pipe under the action of the electric field; S4. After the suction coating is completed, the residual heat of the pipe itself is used to cure the powder coating on the inner wall of the pipe to form a uniform and dense protective coating without the need for post-curing treatment.

8. A method for applying a uniformly cured powder coating specifically for the inner wall of a pipe according to claim 7, characterized in that: In the above step S1, after the surface of the pipe is cleaned and rust-removed, the surface is blown with clean compressed air and dried at 80-120° C. for 30-60 minutes.

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