Anticorrosive and heat-insulating powder coating and heat-insulating pipeline

Abstract

The present application relates to a kind of anticorrosive thermal insulation powder coating and thermal insulation pipeline, belong to the technical field of coating.A kind of anticorrosive thermal insulation powder coating, including primer, intermediate layer coating and surface layer coating;Primer includes the following raw materials: bisphenol A type epoxy resin, curing agent, accelerator, thermoplastic elastomer, silicone resin, coupling agent, filler, leveling agent, defoaming agent;Intermediate layer coating includes the raw material: maleic anhydride grafted polypropylene resin, aerogel powder, hollow ceramic microsphere, foaming agent, thermoplastic elastomer, silicone resin, antioxidant;Surface layer coating includes the following raw materials: polyvinylidene chloride resin, heat stabilizer, maleic anhydride grafted polypropylene resin, pigment and filler, antioxidant.The problem of penetration accelerated corrosion of the inner wall of thermal insulation pipe when conveying high-temperature water is solved in the form of three-layer structure.

Description

A corrosion-resistant and heat-insulating powder coating and heat-insulating pipe Technical Field

[0001] This invention belongs to the field of coating technology and relates to an anti-corrosion and heat-insulating powder coating and a heat-insulating pipe. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] In long-distance high-temperature water pipeline systems, steel pipes are commonly used for transporting water with a long-term temperature below 130℃ and a peak temperature not exceeding 140℃. Anti-corrosion and heat-insulating structures are added to the outer wall of the steel pipe. The inner wall of the steel pipe is in direct contact with the high-temperature water, but usually no anti-corrosion coating is applied. This is because the permeability of moisture in the coating increases at high temperatures, making it difficult for ordinary anti-corrosion coatings to prevent moisture penetration and damage. The untreated inner wall of the steel pipe, exposed to high temperature and humidity for extended periods, is more prone to corrosion, leading to leaks in the insulated pipeline.

[0004] Utility model patent CN201028159Y discloses a corrosion-resistant and heat-insulating pipeline. It consists of an epoxy heavy-duty anti-corrosion powder coating on the inner wall of a steel pipe, and an outer protective layer made of plastic, fiberglass, or galvanized iron sheet, applied sequentially to the outer wall. It is used for transporting liquids requiring corrosion resistance and heat retention. However, high temperatures promote moisture penetration into the anti-corrosion powder coating, accelerating coating damage and hindering its long-term service life.

[0005] The invention disclosed in application publication number CN104482328A presents a multi-layer system for corrosion protection and insulation of deep-sea steel pipelines. It consists of at least five layers: a phenolic epoxy powder coating sprayed onto the surface of the steel pipeline; a polyamide insulation layer covering the phenolic epoxy powder coating; a foamed polypropylene layer covering the polyamide insulation layer; a polyvinylidene chloride (PVDC) isolation layer covering the foamed polypropylene layer; a rigid polypropylene anti-corrosion layer covering the PVDC isolation layer; and adhesive layers connecting the layers to achieve optimal corrosion protection, insulation, impact and scratch resistance. However, it only considers the outer layer's corrosion protection and insulation performance; the coating does not directly contact the high-temperature water, which differs from the operating conditions of long-distance high-temperature water transportation; furthermore, the need for adhesive layers between the layers makes the process overly complex.

[0006] Patent CN101205425A discloses a foamed powder coating. The raw materials include: resin, curing agent, pigments and fillers, foaming agent, flame retardant, and leveling agent. The coating has heat insulation and heat preservation effects through foaming, but its anti-corrosion performance is relatively weak. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an anti-corrosion and heat-insulating powder coating and heat-insulating pipe to solve the problem of seepage corrosion on the inner wall of steel pipes for long-distance transportation of high-temperature water.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] In a first aspect, an anti-corrosion and heat-insulating powder coating includes a base coat, an intermediate coat, and a top coat;

[0010] The base coating comprises the following raw materials in parts by weight: 40-60 parts of bisphenol A epoxy resin, 10-15 parts of curing agent, 0.5-2 parts of accelerator, 1-5 parts of thermoplastic elastomer, 5-20 parts of silicone resin, 1-2 parts of coupling agent, 10-20 parts of filler, 0.5-1 part of leveling agent, and 0.5-1 part of defoamer;

[0011] The intermediate coating comprises the following raw materials in parts by weight: 30-40 parts maleic anhydride grafted polypropylene resin, 30-60 parts aerogel powder, 5-20 parts hollow ceramic microspheres, 1-15 parts foaming agent, 1-5 parts thermoplastic elastomer, 5-10 parts organosilicon resin, and 0.2-1 parts antioxidant.

[0012] The topcoat comprises the following raw materials in parts by weight: 50-70 parts polyvinylidene chloride resin, 0.5-2 parts heat stabilizer, 20-40 parts maleic anhydride grafted polypropylene resin, 1-10 parts pigments and fillers, and 0.2-1 parts antioxidant.

[0013] Secondly, the preparation method of the above-mentioned anti-corrosion and heat-insulating powder coating includes the following steps:

[0014] S1. Mix the raw materials of the base coating evenly, extrude them using a twin-screw extruder, then crush them into tablets, grind them, and pass them through a 60-180 mesh sieve to obtain the base coating.

[0015] S2. Mix the raw materials included in the intermediate layer coating evenly, melt-extrude them using a twin-screw extruder, and granulate them to obtain granules. Grind the granules and pass them through a 40-100 mesh sieve to obtain the intermediate layer coating.

[0016] S3. Mix the raw materials included in the topcoat evenly, melt-extrude using a twin-screw extruder, granulate to obtain granules, grind the granules and pass them through a 40-100 mesh sieve to obtain the topcoat.

[0017] Thirdly, an insulated pipe with the above-mentioned anti-corrosion and heat-insulating powder coating as raw material, wherein a base layer coating is attached to the inner wall of the pipe, an intermediate layer coating is attached to the base layer coating, and a top layer coating is attached to the intermediate layer coating.

[0018] The bottom layer coating is prepared from the bottom coating material, the intermediate layer coating is prepared from the intermediate layer coating material, and the top layer coating is prepared from the top layer coating material.

[0019] Optionally, the pipeline is a steel pipe.

[0020] Fourthly, the preparation method of the above-mentioned insulated pipe includes the following steps:

[0021] S4. After preheating and derusting the pipeline, heat it and then spray the base coat and intermediate coat onto the inner wall of the steel pipe in sequence.

[0022] S5. Keep the pipe rotating and send it into the heating furnace to heat it, so that the bottom layer coating can be cured and the middle layer coating can be foamed.

[0023] S6. After removing the pipe from the heating furnace, spray the topcoat coating on the inner wall.

[0024] S7. Keep the pipe rotating and send it into the heating furnace to heat it, so that the surface coating melts and flows smoothly, completing the inner wall treatment.

[0025] The beneficial effects of this invention are as follows:

[0026] 1. In this invention, the bottom powder coating uses epoxy resin as the main film-forming material, which has the advantages of high adhesion to the inner wall of the steel pipe and high corrosion resistance; the middle foam layer uses maleic anhydride-grafted polypropylene as the skeleton structure and aerogel powder and hollow ceramic microspheres as the heat insulation medium, which has the advantage of heat insulation; the top layer uses polyvinylidene chloride with excellent barrier properties as the main film-forming material, which has good temperature resistance, can withstand high temperatures of 150°C, and can block high-temperature media to prevent media penetration under high-temperature conditions. The three-layer structure solves the problem of accelerated corrosion of the inner wall of the insulated pipe when transporting high-temperature water.

[0027] 2. The bottom coating of this invention uses epoxy resin and other materials as the main film-forming materials, which can form chemical bonds with the steel pipe substrate, giving it good adhesion. Adding a coupling agent to the bottom coating increases the compatibility between the epoxy resin and the silicone resin, while adding a thermoplastic elastomer reduces coating cracking caused by increased cohesion due to the increased coating temperature when the steel pipe is transporting high-temperature media. Adding a thermoplastic elastomer to the intermediate layer improves the toughness of the maleic anhydride-grafted polypropylene resin, further reducing the risk of skeleton breakage during foaming. The maleic anhydride-grafted polypropylene resin not only serves as the skeleton material for the intermediate layer, but the anhydride can also react with the epoxy resin in the bottom layer, improving the adhesion between the intermediate and bottom layers. The maleic anhydride-grafted polypropylene resin added to the top coating is a similar substance to the maleic anhydride-grafted polypropylene resin in the intermediate layer coating, allowing for good fusion at the contact surface and improving the adhesion between the intermediate and top layers. Therefore, no separate adhesive layer is needed between the three layers to obtain a coating structure with high interlayer bonding and no cracking, simplifying the process.

[0028] 3. The intermediate coating of this invention contains a foaming agent. After the intermediate coating is applied, it foams in a heating furnace to form a foamed layer with maleic anhydride-grafted polypropylene as the skeleton structure and aerogel powder and hollow ceramic microspheres as the insulation medium. The addition of organosilicon resin further improves the temperature resistance of the foamed layer. This foamed layer has an extremely low thermal conductivity, which can reduce heat transfer during the transportation of high-temperature media, keeping the bottom coating, which is in direct contact with the inner wall of the steel pipe, at a low temperature range. This solves the problem of poor temperature resistance of the bottom coating and also slows down the aging rate of the bottom coating and other insulation structures on the outer layer of the pipe.

[0029] 4. The anti-corrosion and heat-insulating powder coating prepared by this invention can complete the bottom layer curing, intermediate layer foaming and surface layer melting and leveling processes in the heating furnace during the anti-corrosion processing of the inner wall of the heat-insulating pipe. The heating process route is simple, the production efficiency is high, and it is easy to promote. Detailed Implementation

[0030] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0031] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0032] A corrosion-resistant and heat-insulating powder coating includes a base coat, an intermediate coat, and a top coat;

[0033] The base coating comprises the following raw materials in parts by weight: 40-60 parts of bisphenol A epoxy resin, 10-15 parts of curing agent, 0.5-2 parts of accelerator, 1-5 parts of thermoplastic elastomer, 5-20 parts of silicone resin, 1-2 parts of coupling agent, 10-20 parts of filler, 0.5-1 part of leveling agent, and 0.5-1 part of defoamer;

[0034] The intermediate coating comprises the following raw materials in parts by weight: 30-40 parts maleic anhydride grafted polypropylene resin, 30-60 parts aerogel powder, 5-20 parts hollow ceramic microspheres, 1-15 parts foaming agent, 1-5 parts thermoplastic elastomer, 5-10 parts organosilicon resin, and 0.2-1 parts antioxidant.

[0035] The topcoat comprises the following raw materials in parts by weight: 50-70 parts polyvinylidene chloride resin, 0.5-2 parts heat stabilizer, 20-40 parts maleic anhydride grafted polypropylene resin, 1-10 parts pigments and fillers, and 0.2-1 parts antioxidant.

[0036] Among them, thermoplastic elastomers are polyolefin thermoplastic elastomers.

[0037] Optionally, the thermoplastic elastomer includes one or more polyolefin thermoplastic elastomers (TPO); optional TPO products include: Basel's Q100F, Q300F and CA10A; Exxon's CMU201; Borealis' EE189AI; Sumitomo Chemical's WT485;

[0038] Optionally, the bisphenol A type epoxy resin has a softening point of 90-130°C and includes one or more of one-step epoxy resin and two-step epoxy resin.

[0039] Optionally, the curing agent includes one or more of phenolic curing agents and amine curing agents.

[0040] Optionally, the promoter is an imidazole or cycloamidinium compound, including one or more of 2-methylimidazole, 2-isopropylimidazole, and 2-phenylimidazole.

[0041] Optionally, the silicone resin includes one or more solid silicone resins; optional silicone resin products include Wacker's SILRES 603, 604, 605 and 610 series products.

[0042] Optionally, the coupling agent includes one or more powder coupling agents, and the optional coupling agent products include: PCA-302A and PCA-302E from Nanjing Nengde Company.

[0043] Optionally, the filler includes one or more of the following: nano-barium sulfate, nano-calcium carbonate, nano-silica powder, nano-wollastonite powder, nano-feldspar powder, and mica powder.

[0044] Optionally, the leveling agent includes one or more acrylate products, and the optional leveling agent products include: PV88 from Ningbo Nanhai, L88 from Wuhan Yincai, and WK538 from Ningbo Weikai Chemical.

[0045] Optionally, the defoamer in the base powder is a benzoin-based product, including one or more of benzoin and anti-yellowing benzoin.

[0046] Optionally, the maleic anhydride-grafted polypropylene resin includes one or more maleic anhydride-grafted polypropylene resins with a melt index of 1-40 g / 10 min (230℃, 2.16 kg); optional maleic anhydride-grafted polypropylene resin products include: DuPont's BYNEL 50E806 and BYNEL 50E571; Arkema's OREVAC 18729 and OREVAC 18750; Mitsui's ADMER QB510A and ADMER QF551, etc.

[0047] Optionally, the aerogel powder is a hydrophobic silica aerogel powder; the aerogel powder has a particle size of 150-200 mesh and micropores with a pore size of 20-50 nm.

[0048] Optionally, the hollow ceramic microspheres are 50-200 mesh; the aerogel particles and hollow ceramic microspheres form a graded relationship, and the uniform mixing can improve the strength of the foamed layer.

[0049] Optionally, the foaming agent includes one or more of azodicarbonamide, 4,4-oxobis(benzenesulfonamide)aminourea, and p-toluenesulfonamide.

[0050] Optionally, the polyvinylidene chloride resin includes one or more of the SLV20 type resin and SLV22 type resin from Zhejiang Juhua.

[0051] Optionally, the antioxidant includes one or more of hindered phenolic antioxidants, phosphite antioxidants, thioester antioxidants, and amine antioxidants.

[0052] Optionally, the heat stabilizer includes one or more of calcium-zinc stabilizers, composite stabilizers, and rare earth stabilizers.

[0053] Optionally, the pigments and fillers include one or more of titanium dioxide, phthalocyanine blue, phthalocyanine green, medium chrome yellow, DPP red, permanent red, permanent violet, ultramarine, nano barium sulfate, nano silica powder, and nano calcium carbonate.

[0054] Optionally, the undercoat may further include 1-5 parts by weight of pigments, including one or more of titanium dioxide, phthalocyanine blue, phthalocyanine green, medium chrome yellow, DPP red, permanent red, permanent violet, ultramarine, nano barium sulfate, nano silica powder, and nano calcium carbonate.

[0055] The preparation method of the above-mentioned anti-corrosion and heat-insulating powder coating includes the following steps:

[0056] S1. Mix the raw materials of the base coating evenly, extrude them using a twin-screw extruder, then crush them into tablets, grind them, and pass them through a 60-180 mesh sieve to obtain the base coating.

[0057] S2. Mix the raw materials included in the intermediate layer coating evenly, melt-extrude them using a twin-screw extruder, and granulate them to obtain granules. Grind the granules and pass them through a 40-100 mesh sieve to obtain the intermediate layer coating.

[0058] S3. Mix the raw materials included in the topcoat evenly, melt-extrude using a twin-screw extruder, granulate to obtain granules, grind the granules and pass them through a 40-100 mesh sieve to obtain the topcoat.

[0059] Optionally, in S2, the granular material is cooled at low temperature and ground into powder using an ultra-low temperature grinding process.

[0060] Optionally, in S3, the pelletizing method is underwater pelletizing; the pellets are cooled at low temperature and ground into powder using an ultra-low temperature grinding process.

[0061] A type of insulated pipe with the raw material including the anti-corrosion and heat-insulating powder coating as described above, wherein the inner wall of the pipe is coated with a base layer coating, an intermediate layer coating is coated on the base layer coating, and a top layer coating is coated on the intermediate layer coating.

[0062] Optionally, the pipeline is a steel pipe.

[0063] The above-mentioned method for preparing insulated pipes includes the following steps:

[0064] S4. After preheating and derusting the pipeline, heat it and then spray the base coat and intermediate coat onto the inner wall of the steel pipe in sequence.

[0065] S5. Keep the pipe rotating and send it into the heating furnace to heat it, so that the bottom layer coating can be cured and the middle layer coating can be foamed.

[0066] S6. After removing the pipe from the heating furnace, maintain the pipe temperature at 190-210℃, and spray the topcoat on the inner wall during this period.

[0067] S7. Keep the pipe rotating and send it into the heating furnace to heat it, so that the surface coating melts and flows smoothly, completing the inner wall treatment.

[0068] Optionally, in S4, after the pipe is preheated and derusted, the surface anchor pattern depth reaches 40μm-100μm, and the surface derusting grade is Sa2.5.

[0069] Optionally, in S4, the pipes are preheated and derusted before being heated to 170-200 ℃.

[0070] Optionally, in S4, the thickness of the base coat is 150-300 μm.

[0071] Optionally, in S4, the thickness of the intermediate layer coating is 150-300 μm.

[0072] Optionally, in S5, the heating temperature is 200-230℃, and the holding time is 10-30 minutes.

[0073] Optionally, in S6, the thickness of the topcoat spray is 200-300 μm.

[0074] Optionally, in S6, the heating temperature is 200-230℃ and the holding time is 10-30 minutes.

[0075] Example 1

[0076] Anti-corrosion and heat-insulating powder coatings include primer, intermediate coating and topcoat;

[0077] The raw materials of the base coat, by weight, include: 50 parts of bisphenol A epoxy resin (HY905 resin from Anhui Hengyuan), 10 parts of curing agent (phenolic curing agent, specifically 969A-2 product from Daqing Qinglu), 1 part of accelerator (2-methylimidazole), 5 parts of thermoplastic elastomer (Q300F resin from Basel), 10 parts of silicone resin (605 resin from Wacker), 2 parts of coupling agent (PCA-302A product from Nanjing Nengde), 18 parts of filler (nano barium sulfate), 1 part of leveling agent (L88 product from Wuhan Yincai), 1 part of defoamer (anti-yellowing benzoin), and 2 parts of pigment (titanium dioxide and phthalocyanine blue in a weight ratio of 1:1).

[0078] The raw materials for the intermediate coating include: 40 parts of maleic anhydride grafted polypropylene resin (Arkema's OREVAC 18729 resin), 40 parts of aerogel powder, 5 parts of hollow ceramic microspheres (100 mesh), 5 parts of foaming agent (4,4-oxobisbenzenesulfonamide), 4 parts of thermoplastic elastomer (Basel's Q300F resin), 5 parts of silicone resin (Wacker's 605 resin), and 1 part of antioxidant (hindered phenolic antioxidant 1010 and phosphite antioxidant 168, with a mass ratio of 1:2).

[0079] The raw materials for the topcoat include: 70 parts of polyvinylidene chloride resin (Zhejiang Juhua's SLV20 type resin), 1 part of heat stabilizer (calcium zinc stabilizer), 20 parts of maleic anhydride grafted polypropylene resin (Arkema's OREVAC 18729 resin), 8 parts of pigments and fillers (mass ratio, titanium dioxide: phthalocyanine blue: barium sulfate = 2:1:7), and 1 part of antioxidant (hindered phenolic antioxidant 1010 and phosphite antioxidant 168, with a mass ratio of 1:2).

[0080] The preparation method of anti-corrosion and heat-insulating powder coating includes the following steps:

[0081] S1. The raw materials for the base coat are added into a rotary mixer and stirred for 10 minutes to ensure uniform mixing. Then, the mixture is extruded through a twin-screw extruder with a set temperature of 95°C and a length-to-diameter ratio of 16:1. The extruded material is then compressed and crushed into flakes by a water-cooled tablet press. Finally, the material is ground into powder by an ACM mill and sieved through a 120-mesh screen to obtain the base coat.

[0082] S2. The raw materials included in the intermediate layer coating are mixed evenly in a high-speed mixer at room temperature. The mixture is then processed into granular material through a twin-screw extruder at 140-180℃, involving melting, extrusion, cooling, and pelletizing. The granular material is then placed in a cooling tank containing liquid nitrogen for low-temperature cooling. The liquid nitrogen-cooled granules are then ground into powder using an ultra-low temperature grinding process. The powder is then sieved through a 100-mesh screen to obtain the intermediate layer coating.

[0083] S3. The raw materials for the topcoat are mixed evenly in a high-speed mixer at room temperature. The mixture is then processed into granules using a twin-screw extruder at 140-180℃ through melting, extrusion, cooling, and pelletizing. The granules are then placed in a cooling tank containing liquid nitrogen for cryogenic cooling. The liquid nitrogen-cooled granules are then ground into powder using an ultra-low temperature grinding process. The powder is sieved through a 100-mesh screen to obtain the topcoat.

[0084] The method for preparing insulated pipes includes the following steps:

[0085] S4. The steel pipe is preheated at 40℃ with medium frequency to remove surface moisture, and then shot blasting is performed to remove rust, so that the anchor pattern depth on the steel pipe surface reaches 40-100μm and the surface rust removal grade reaches Sa2.5. The rust-removed steel pipe is heated to 180℃, and the steel pipe is rotated by a mechanical device. A 150μm thick base coat and a 200μm thick intermediate coat are sprayed on the inner wall of the steel pipe.

[0086] S5. While maintaining rotation, place the steel pipe into a heating furnace at 230°C and maintain the temperature for 10 minutes to allow the bottom layer coating to melt and flow smoothly, and the middle layer coating to complete the foaming process.

[0087] S6. Remove the steel pipe and maintain the pipe temperature at 190-210℃. During this period, directly spray a 300μm thick topcoat.

[0088] S7. While the steel pipe is rotating, place it in a heating furnace at 230℃ and heat it for 10 minutes. Then, take the steel pipe out and let it cool naturally before performing external wall insulation treatment to obtain the finished insulated pipe.

[0089] Comparative Example 1

[0090] The difference from Example 1 is that only the base coat from Example 1 is used.

[0091] The method for preparing the insulated pipe differs from that in Example 1 in that it includes the following steps:

[0092] The steel pipe is preheated at 40℃ with medium frequency to remove surface moisture, and then shot blasting is performed to remove rust, so that the anchor pattern depth on the steel pipe surface reaches 40μm-100μm and the surface rust removal grade reaches Sa2.5. Then the rust-removed steel pipe is heated to 180℃, and the steel pipe is rotated by a mechanical device to spray a 650μm thick base coating on the inner wall of the steel pipe.

[0093] While maintaining rotation, the steel pipe is placed in a 230℃ heating furnace for 10 minutes to allow the bottom coating to melt and flow. After the steel pipe is removed and allowed to cool naturally, the outer wall is insulated to obtain the finished insulated pipe.

[0094] Comparative Example 2

[0095] The difference from Example 1 is that only the intermediate layer coating from Example 1 is used.

[0096] The difference between the preparation method of the insulated pipe and Comparative Example 1 is that: the rust-removed steel pipe is heated to 180°C, the steel pipe is rotated by a mechanical device, a 650μm thick intermediate layer coating is sprayed on the inner wall of the steel pipe, and then the steel pipe is placed in a 230°C heating furnace for 10 minutes while maintaining the rotation, so that the intermediate layer coating can complete the melting, leveling and foaming process.

[0097] Comparative Example 3

[0098] The difference from Example 1 is that only the topcoat coating from Example 1 is used.

[0099] The difference between the preparation method of the insulated pipe and Comparative Example 1 is that: the rust-removed steel pipe is heated to 180°C, the steel pipe is rotated by a mechanical device, a 650μm thick surface coating is sprayed on the inner wall of the steel pipe, and then the steel pipe is placed in a 230°C heating furnace for 10 minutes while maintaining the rotation, so that the surface coating can complete the melting and leveling process.

[0100] Comparative Example 4

[0101] The difference from Example 1 is that only the topcoat and topcoat of Example 1 are used, and the intermediate coating is not used.

[0102] The difference between the preparation method of the insulated pipe and Comparative Example 1 is that: the rust-removed steel pipe is heated to 180°C, and the steel pipe is rotated by a mechanical device. A 350μm thick base coat and a 250μm thick top coat are sprayed on the inner wall of the steel pipe. Then, while maintaining the rotation, the steel pipe is placed in a 230°C heating furnace for 10 minutes to allow the base coat and top coat to complete the melting and leveling process.

[0103] Comparative Example 5

[0104] The difference from Example 1 is as follows:

[0105] The raw materials of the base coat, by weight, include: 45 parts of bisphenol A epoxy resin (HY905 resin from Anhui Hengyuan), 1 part of accelerator (2-methylimidazole), 20 parts of silicone resin (605 resin from Wacker), 2 parts of coupling agent (PCA-302A product from Nanjing Nengde), 18 parts of filler (nano barium sulfate), 1 part of leveling agent (L88 product from Wuhan Yincai), 1 part of defoamer (anti-yellowing benzoin), and 2 parts of pigment (titanium dioxide and phthalocyanine blue in a weight ratio of 1:1). No curing agent or thermoplastic elastic resin is added.

[0106] The preparation process of the bottom layer, the raw materials and preparation process of the intermediate layer coating, the raw materials and preparation process of the top layer coating, and the preparation method of the insulated pipe are the same as in Example 1.

[0107] Comparative Example 6

[0108] The difference from Example 1 is as follows:

[0109] The raw materials for the intermediate coating, by weight, include: 40 parts maleic anhydride-grafted polypropylene resin (Arkema's OREVAC18729 resin), 5 parts hollow ceramic microspheres (100 mesh), 5 parts foaming agent (4,4-oxobisbenzenesulfonamide), 4 parts thermoplastic elastomer (Basel's Q300F resin), 5 parts silicone resin (Wacker's 605 resin), and 1 part antioxidant (hindered phenolic antioxidant 1010 and phosphite antioxidant 168, in a mass ratio of 1:2). No aerogel powder is added.

[0110] The raw materials and preparation process of the bottom layer, the preparation process of the intermediate layer coating, the raw materials and preparation process of the top layer coating, and the preparation method of the insulated pipe are the same as in Example 1.

[0111] Comparative Example 7

[0112] The difference from Example 1 is as follows:

[0113] The raw materials for the topcoat, by weight, include: 90 parts of polyvinylidene chloride resin (Zhejiang Juhua's SLV20 type resin), 1 part of heat stabilizer (calcium-zinc stabilizer), 8 parts of pigments and fillers (mass ratio: titanium dioxide: phthalocyanine blue: barium sulfate = 2:1:7), and 1 part of antioxidant (hindered phenolic antioxidant 1010 and phosphite antioxidant 168, with a mass ratio of 1:2). Maleic anhydride-grafted polypropylene resin is not added.

[0114] The raw materials and preparation process of the bottom layer, the raw materials and preparation process of the intermediate layer coating, the preparation process of the top layer coating, and the preparation method of the insulated pipe are the same as in Example 1.

[0115] Example 2

[0116] The difference compared to Example 1 is as follows:

[0117] The raw materials for the base coat, by weight, include: 40 parts of bisphenol A epoxy resin (HY905 resin from Anhui Hengyuan), 10 parts of curing agent (phenolic curing agent, specifically 969A-2 product from Daqing Qinglu), 1 part of accelerator (2-methylimidazole), 5 parts of thermoplastic elastomer (Q300F resin from Basel), 20 parts of silicone resin (605 resin from Wacker), 2 parts of coupling agent (PCA-302A product from Nanjing Nengde), 18 parts of filler (nano barium sulfate), 1 part of leveling agent (L88 product from Wuhan Yincai), 1 part of defoamer (anti-yellowing benzoin), and 2 parts of pigment (titanium dioxide and phthalocyanine blue in a weight ratio of 1:1), with the addition of silicone resin.

[0118] The preparation process of the bottom layer, the raw materials and preparation process of the intermediate layer coating, the raw materials and preparation process of the top layer coating, and the preparation method of the insulated pipe are the same as in Example 1.

[0119] Example 3

[0120] The difference compared to Example 1 is as follows:

[0121] The raw materials for the intermediate coating, by weight, include: 40 parts maleic anhydride-grafted polypropylene resin (Arkema's OREVAC18729 resin), 30 parts aerogel powder, 15 parts hollow ceramic microspheres (100 mesh), 5 parts foaming agent (4,4-oxobisbenzenesulfonamide), 4 parts thermoplastic elastomer (Basell's Q300F resin), 5 parts silicone resin (Wacker's 605 resin), and 1 part antioxidant (hindered phenolic antioxidant 1010 and phosphite antioxidant 168, in a mass ratio of 1:2).

[0122] The raw materials and preparation process of the bottom layer, the preparation process of the intermediate layer coating, the raw materials and preparation process of the top layer coating, and the preparation method of the insulated pipe are the same as in Example 1.

[0123] Example 4

[0124] The difference compared to Example 1 is as follows:

[0125] The raw materials for the topcoat, by weight, include 50 parts of polyvinylidene chloride resin (Zhejiang Juhua's SLV20 type resin), 1 part of heat stabilizer (calcium-zinc stabilizer), 40 parts of maleic anhydride-grafted polypropylene resin (Arkema's OREVAC 18729 resin), 8 parts of pigments and fillers (by mass ratio, titanium dioxide: phthalocyanine blue: barium sulfate = 2:1:7), and 1 part of antioxidant (hindered phenolic antioxidant 1010 and phosphite antioxidant 168, by mass ratio of 1:2).

[0126] The raw materials and preparation process of the base coat, the raw materials and preparation process of the intermediate coat, the preparation process of the top coat, and the preparation method of the insulated pipe are the same as in Example 1.

[0127] Performance testing includes:

[0128] 1. Adhesion test: The pull-out method in GB / T 5210-2006 was used to test the adhesion between the base powder and the steel pipe, the adhesion between the base powder and the intermediate powder, the adhesion between the intermediate powder and the flour, the adhesion between the intermediate powder and the steel pipe, and the adhesion between the flour and the steel pipe.

[0129] 2. Distilled water absorption rate test: The test method in GB / T1034-2008 was adopted to test the water absorption rate of the coating after soaking in distilled water at 90℃ for 15 days.

[0130] 3. High temperature and high pressure test: Using the test method in SY / T0442-2010, the coated insulation pipe is immersed in a high pressure vessel with water at 14MPa and 150℃. After 168h of immersion test, the adhesion between the coatings is tested according to the adhesion test method.

[0131] The test results are shown in Tables 1 and 2.

[0132] Table 1

[0133]

[0134] Table 2

[0135]

[0136] Table 1 shows a performance comparison between Example 1 and the Comparative Example. It can be seen that: Compared to Comparative Example 1, Example 1 uses only a base powder to coat the steel pipe, and the adhesion between the base powder and the steel pipe mainly depends on the performance of the base powder. Therefore, the adhesion between the base powder and the steel pipe in Comparative Example 1 is consistent with that in Example 1, but after high-temperature and high-pressure testing, the adhesion decreases significantly. Comparative Example 2 uses only an intermediate powder for coating. Since the intermediate powder is a foamed layer, its contact area with the steel pipe is small, resulting in lower adhesion. Comparative Example 3 uses only flour for coating. Because the flour contains maleic anhydride-grafted polypropylene material, it also has a certain adhesion to the steel pipe, and polyvinylidene chloride resin has a strong barrier effect. Therefore, compared to the intermediate powder, the adhesion is relatively larger and shows some temperature resistance, but the overall adhesion is much worse than that of Example 1. Comparative Example 4 uses a steel pipe coated with base powder and flour. The adhesion between the base layer and the steel pipe is similar to that in Example 1. Since the flour also contains maleic anhydride-grafted polypropylene, it can react with the epoxy resin in the base powder, resulting in strong adhesion between the base powder and the flour. However, due to the lack of an intermediate layer, the heat insulation effect is poor, and the adhesion deteriorates after high-temperature and high-pressure testing. Comparative Example 5 removes the thermoplastic elastomer from the base powder, resulting in a significant decrease in the adhesion between the base powder and the metal after high-temperature and high-pressure testing due to the high cohesiveness of the base powder. Comparative Example 6 removes aerogel powder from the intermediate powder. After high-temperature and high-pressure testing, the overall coating adhesion decreases due to the lack of heat insulation from the aerogel. Comparative Example 7 removes maleic anhydride-grafted polypropylene resin from the flour, resulting in a near loss of adhesion between the surface layer and the intermediate layer.

[0137] Table 2 shows the performance comparison between the various embodiments. It can be seen that: in Example 2, increasing the content of silicone resin in the base powder improved the temperature resistance of the base powder. After high temperature and high pressure test, the adhesion between the bottom layer and the steel pipe remained basically unchanged; in Example 3, reducing the content of aerogel powder reduced the heat insulation effect of the intermediate layer. After high temperature and high pressure test, the adhesion between the bottom layer and the metal decreased; in Example 4, reducing the content of polyvinylidene chloride weakened the barrier effect of the coating and increased the distilled water absorption rate of the coating. After high temperature and high pressure test, the adhesion between the bottom layer and the steel pipe decreased, and the adhesion between the bottom layer and the intermediate layer, and between the intermediate layer and the top layer also decreased.

[0138] As can be seen from the data in the embodiments, the anti-corrosion and heat-insulating powder material of the present invention has excellent water resistance and high temperature resistance. During the transportation of high temperature water, it can prevent water from penetrating the coating, increase the anti-corrosion ability of the steel pipe, and further extend the service life of the heat-insulating pipe.

[0139] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A corrosion-resistant and heat-insulating powder coating, characterized in that, The coating consists of a base coat, an intermediate coat, and a top coat. The base coat comprises the following raw materials in parts by weight: 40-60 parts bisphenol A epoxy resin, 10-15 parts curing agent, 0.5-2 parts accelerator, 1-5 parts thermoplastic elastomer, 5-20 parts silicone resin, 1-2 parts coupling agent, 10-20 parts filler, 0.5-1 part leveling agent, 0.5-1 part defoamer, and 1-5 parts pigment. The intermediate coat comprises the following raw materials in parts by weight: 30-40 parts maleic anhydride-grafted polypropylene resin, 30-60 parts aerogel powder, and 5-2 parts hollow ceramic microspheres. The coating consists of the following components by weight: 0 parts polyvinylidene chloride resin, 1-15 parts foaming agent, 1-5 parts thermoplastic elastomer, 5-10 parts silicone resin, and 0.2-1 parts antioxidant; the topcoat is composed of the following raw materials: 50-70 parts polyvinylidene chloride resin, 0.5-2 parts heat stabilizer, 20-40 parts maleic anhydride-grafted polypropylene resin, 1-10 parts pigments and fillers, and 0.2-1 parts antioxidant; the aerogel powder is a hydrophobic silica aerogel powder; the aerogel powder has a particle size of 150-200 mesh and a micropore size of 20-50 nm; the hollow ceramic microspheres have a particle size of 50-200 mesh.

2. The anti-corrosion and heat-insulating powder coating as described in claim 1, characterized in that, The bisphenol A type epoxy resin has a softening point of 90-130℃ and includes one or more of one-step epoxy resin and two-step epoxy resin; the thermoplastic elastomer includes one or more of polyolefin thermoplastic elastomers; the curing agent includes one or more of phenolic curing agents and amine curing agents; the maleic anhydride grafted polypropylene resin includes one or more of maleic anhydride grafted polypropylene resins with a melt index of 1-40 g / 10 min.

3. The anti-corrosion and heat-insulating powder coating as described in claim 1, characterized in that, The accelerator includes one or more of 2-methylimidazole, 2-isopropylimidazole, and 2-phenylimidazole; the defoamer in the primer includes benzoin; the leveling agent includes one or more acrylate products; the foaming agent includes one or more of azodicarbonamide, 4,4-oxobis(benzenesulfonyl)aminourea, and p-toluenesulfonyl)aminourea; and the antioxidant includes one or more of hindered phenolic antioxidants, phosphite antioxidants, thioester antioxidants, and amine antioxidants.

4. The anti-corrosion and heat-insulating powder coating as described in claim 1, characterized in that, The filler includes one or more of nano-barium sulfate, nano-calcium carbonate, nano-silica powder, nano-wollastonite powder, nano-feldspar powder, and mica powder; the heat stabilizer includes one or more of calcium-zinc stabilizer and rare earth stabilizer; the pigments include one or more of titanium dioxide, phthalocyanine blue, phthalocyanine green, medium chrome yellow, permanent red, permanent violet, ultramarine, nano-barium sulfate, nano-silica powder, and nano-calcium carbonate; the pigments in the undercoat include one or more of titanium dioxide, phthalocyanine blue, phthalocyanine green, medium chrome yellow, permanent red, permanent violet, and ultramarine.

5. A method for preparing an anti-corrosion and thermal insulation powder coating as described in any one of claims 1-4, comprising the following steps: S1. Mix the raw materials of the base coat evenly, extrude using a twin-screw extruder, then crush into sheets, and finally grind and pass through a 60-180 mesh sieve to obtain the base coat; S2. Mix the raw materials of the intermediate coat evenly, melt extrude using a twin-screw extruder, granulate to obtain granules, and grind the granules and pass through a 40-100 mesh sieve to obtain the intermediate coat; S3. Mix the raw materials of the top coat evenly, melt extrude using a twin-screw extruder, granulate to obtain granules, and grind the granules and pass through a 40-100 mesh sieve to obtain the top coat.

6. The method for preparing the anti-corrosion and heat-insulating powder coating as described in claim 5, characterized in that, In S3, the pelletizing method is underwater pelletizing.

7. A thermal insulation pipe whose raw material includes the anti-corrosion and thermal insulation powder coating as described in any one of claims 1-4, characterized in that: The inner wall of the pipe is coated with a base layer, an intermediate layer is coated with the base layer, and a top layer is coated with the intermediate layer. The base layer is prepared from the base coating, the intermediate layer is prepared from the intermediate coating, and the top layer is prepared from the top coating.

8. The insulated pipe as described in claim 7, characterized in that: The pipeline is a steel pipe.

9. A method for preparing an insulated pipe as described in any one of claims 7-8, characterized in that, Includes the following steps: S4. After preheating and derusting the pipe, heat it and spray the base coat and intermediate coat onto the inner wall of the steel pipe in sequence; S5. Keep the pipe rotating and send it into the heating furnace to heat it, so that the base coat can be cured and the intermediate coat can be foamed; S6. After removing the pipe from the heating furnace, spray the top coat onto the inner wall; S7. Keep the pipe rotating and send it into the heating furnace to heat it, so that the top coat can melt and flow smoothly, completing the inner wall treatment.

10. The method for preparing the insulated pipe as described in claim 9, characterized in that, In S4, the steel pipe is preheated and derusted before being heated to 170-200 ℃; in S4, the thickness of the base coat is 150-300 μm; in S4, the thickness of the intermediate coat is 150-300 μm; in S5, the heating temperature is 200-230 ℃, and the holding time is 10-30 min; in S6, the pipe temperature is maintained at 190-210 ℃, during which the top coat is sprayed on the inner wall; in S6, the thickness of the top coat is 200-300 μm; in S7, the heating temperature is 200-230 ℃, and the holding time is 10-30 min.

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