Heat-resistant coating for inner wall of pipeline and preparation method thereof

Abstract

The application discloses a heat-resistant coating for pipeline inner wall and a preparation method thereof and belongs to the technical field of pipeline protection. The heat-resistant coating comprises the following raw materials in parts by weight: 85-97 parts of bisphenol F type epoxy resin, 7-17 parts of heat-resistant additive, 0-7 parts of pigment, 3-5 parts of curing agent, 8-12 parts of heat-resistant filler and 2-4 parts of processing additive. The prepared coating is an environment-friendly coating and has excellent environment-friendly property; the coating takes the bisphenol F type epoxy resin as a matrix, and thus the coating is endowed with certain flexibility; the heat-resistant filler has better compatibility with the matrix, and thus the heat-resistant performance of the coating is enhanced; the heat-resistant additive can synergize with the heat-resistant filler, greatly enhances the heat-resistant performance of the material, and further improves the flame retardance and flexibility of the coating; in conclusion, the prepared heat-resistant coating has excellent heat-resistant performance, flame retardance and flexibility, is environment-friendly, and has important application value in the field of pipeline protection.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of pipeline protection, and particularly relates to a heat-resistant coating for the inner wall of a pipeline and a preparation method thereof. BACKGROUND

[0002] In the field of industrial production and energy transmission, pipeline systems, as the core carriers for fluid medium transportation, have long been subjected to multiple tests of high temperature, high pressure, corrosive medium and complex mechanical stress. In particular, in high-temperature operating environments such as petroleum chemical industry, thermal power generation and metallurgical manufacturing, the protection of the inner wall of the pipeline directly affects the safety and service life of the system. Although traditional pipeline materials such as carbon steel and alloy steel have certain mechanical strength, they are prone to problems such as oxidation corrosion, material creep and structural failure in long-term high-temperature environments. To solve this contradiction, surface protection technology has become a key breakthrough, and heat-resistant coatings have gradually become a research hotspot in the field of industrial pipeline protection due to their convenient construction and significant protection effect.

[0003] Existing pipeline inner wall protection technologies mainly rely on metal plating, ceramic lining or organic coating. Although metal plating can improve the surface hardness, it has the risk of interface peeling caused by the difference in thermal expansion coefficient, and is prone to grain boundary oxidation at high temperatures. Although ceramic lining technology has excellent high-temperature resistance, its brittle nature can cause stress concentration and cracking, and the complex construction process limits its application in complex pipeline systems. Organic coatings have good adhesion and certain high-temperature resistance and are often used in the field of industrial pipeline protection.

[0004] Traditional solvent-based organic coatings contain a large amount of volatile organic compounds, causing environmental pollution during production and construction. The development of environmentally friendly coatings has broad market prospects. Environmentally friendly coatings include water-based coatings, high-solid coatings, powder coatings, solvent-free coatings and radiation-cured coatings. Among them, powder coatings are solid powder synthetic resin coatings composed of solid resins, pigments, fillers and additives. Unlike ordinary solvent-based coatings and water-based coatings, the dispersion medium of powder coatings is not solvent or water, but air. It has the characteristics of no solvent pollution, 100% film formation and low energy consumption. It has a wide application in the field of pipeline protection coatings. However, the solid resin in powder coatings usually uses epoxy resin. Although epoxy resin has certain heat resistance, it will undergo thermal aging and cause the coating to blister or even fall off when used in high-temperature environments for a long time. In addition, epoxy resin is an organic material with high flammability, which has certain safety hazards. Therefore, there is an urgent need to invent a coating with heat resistance and flame retardance to meet the higher requirements of the pipeline protection field. SUMMARY

[0005] The present application aims to overcome the defects of the prior art and provides a heat-resistant coating for the inner wall of a pipeline and a preparation method thereof.

[0006] The object of the present application can be achieved by the following technical solutions:

[0007] A preparation method of a heat-resistant coating for pipeline inner wall, comprising the following steps:

[0008] The bisphenol F type epoxy resin is placed in a drying oven for drying, and then is stirred with heat-resistant additives, pigments, curing agents, heat-resistant fillers and processing aids in a mixer to obtain a mixture, the mixture is added into a double-screw extruder for melt extrusion and tabletting, and then is crushed and ground to obtain the heat-resistant coating for pipeline inner wall.

[0009] Further, the raw materials are as follows in terms of weight percentage: 85-97 parts of bisphenol F type epoxy resin, 7-17 parts of heat-resistant additives, 0-7 parts of pigments, 3-5 parts of curing agents, 8-12 parts of heat-resistant fillers and 2-4 parts of processing aids.

[0010] Further, the drying condition is 70-80℃, and the time is 12-24h.

[0011] Further, the stirring condition is a stirring speed of 300-600r / min and a stirring time of 10-20min.

[0012] Further, the curing agent is dicyandiamide.

[0013] Further, the processing aid is one of magnesium stearate, white paraffin and polyethylene wax.

[0014] The bisphenol F type epoxy resin has higher flexibility than bisphenol A type epoxy resin, the prepared coating is an environmentally-friendly powder coating, does not contain organic solvents, has low VOC content and has excellent environmental friendliness.

[0015] Further, the heat-resistant filler is prepared by the following steps:

[0016] A1, boron nitride is added into a concentrated nitric acid solution, stirred at 80℃ for 2h to remove surface impurities and introduce hydroxyl groups, centrifuged and washed to neutral, and vacuum dried to obtain pretreated boron nitride;

[0017] A2, silane coupling agent KH-560 is mixed with an ethanol aqueous solution (volume ratio of ethanol / water 4:1), hydrochloric acid solution is added dropwise to adjust the pH of the system to 4-5, stirring is continued at room temperature for 15min, then pretreated boron nitride is added into the solution, mechanical stirring is carried out at 55℃ in a constant temperature water bath for 8h, the reaction is completed, centrifugal separation is carried out, the product is washed with anhydrous ethanol for multiple times, and finally dried in a vacuum drying oven and ground into powder to obtain the heat-resistant filler.

[0018] Further, the ratio of the amount of boron nitride to the amount of concentrated nitric acid solution in step A1 is 1g:20mL.

[0019] Further, the ratio of the amount of silane coupling agent KH-560, the aqueous ethanol solution, and the pretreated boron nitride in step A2 is 9.7 g: 50 mL: 1 g.

[0020] After the pretreatment, the boron nitride has a large number of hydroxyl groups on the surface, which can react with the hydrolyzed silane coupling agent KH-560 to modify the boron nitride. The modified boron nitride has improved hydrophobicity and compatibility with the epoxy resin matrix. In addition, the boron nitride has excellent heat resistance, so it can be used as a heat-resistant filler to significantly improve the heat resistance of the coating.

[0021] Further, the heat-resistant additive is prepared by the following steps:

[0022] Step 1: 3-amino-5-methylisoxazole, N,N-diisopropylethylamine, and diethyleneglycol dimethyl ether are added to a three-necked flask equipped with a thermometer, a spherical condenser, and a magnetic stirrer. After uniform stirring, ethenyltrichlorosilane is added dropwise, with the temperature controlled to not exceed 20°C during the process. After the addition is complete, the temperature is heated to 90°C and maintained constant. The reaction is refluxed for 8 hours. After the reaction is complete, part of the solvent is removed by vacuum distillation, and then purified by silica gel column chromatography (eluent: petroleum ether and ethyl acetate, volume ratio 4:1). The eluent is removed by rotary evaporation to obtain the intermediate product.

[0023] Under the catalysis of N,N-diisopropylethylamine, 3-amino-5-methylisoxazole reacts with ethenyltrichlorosilane, and the molar ratio of the two is adjusted to approximately 3:1 (3-amino-5-methylisoxazole is slightly excessive). This allows the three chlorine groups on the ethenyltrichlorosilane to participate in the reaction, resulting in the intermediate product. The reaction process is as follows:

[0024]

[0025] Step 2: The intermediate product, azobisisobutyronitrile, 1-decanethiol, and diethyleneglycol dimethyl ether are added to a three-necked flask equipped with a thermometer, a spherical condenser, and a magnetic stirrer. After uniform stirring, the temperature is heated to 80°C and maintained constant. The reaction is stirred for 5 hours. After the reaction is complete, filtration is performed, and part of the solvent is removed by vacuum distillation. Then, the product is purified by silica gel column chromatography (eluent: petroleum ether and ethyl acetate, volume ratio 5:1). The eluent is removed by rotary evaporation to obtain the heat-resistant additive.

[0026] Under the catalysis of azobisisobutyronitrile, the unsaturated carbon-carbon double bond in the intermediate product molecule undergoes a thiol-ene click reaction with the mercaptan in the 1-decanethiol molecule, resulting in the heat-resistant additive. The specific reaction process is as follows:

[0027]

[0028] The prepared heat-resistant auxiliary molecule contains an isoxazole ring structure, which is a five-membered heterocyclic ring. This special structure can disperse electron density through conjugation effect, reduce the reactivity of the ring, thereby improve the thermal stability, and the introduction of three isoxazole ring structures makes the thermal stability stronger, which can greatly enhance the heat resistance of the epoxy resin matrix. In addition, the auxiliary molecule also contains Si-N flame-retardant components, which are more likely to form a dense Si-C or Si-Si crosslinking network during combustion, and the flame-retardant performance is better than that of the traditional silicon-oxygen system. Moreover, Si-N is a covalent bond, which can also improve the heat resistance of the matrix to a certain extent. Furthermore, the auxiliary molecule contains sulfur elements, which can form a stable carbon layer rich in C-S bonds during combustion, and can play a synergistic effect with Si-N flame-retardant components to greatly enhance the flame-retardant performance of the matrix. Finally, the heat-resistant auxiliary molecule contains a long carbon chain structure. Because the long carbon chain has a long chain segment and high internal rotation freedom, it has good flexibility. It can not only toughen the matrix, but also penetrate into the macromolecular chains of the matrix, thereby improving the migration resistance of the small molecule heat-resistant auxiliary.

[0029] Further, the amount ratio of 3-amino-5-methylisoxazole, N,N-diisopropylethylamine, diethyleneglycol dimethyl ether and ethylene trichlorosilane in step 1 is 31.7g:0.2g:120mL:16.1g.

[0030] Further, the amount ratio of the intermediate product, azobisisobutyronitrile, 1-decanethiol and diethyleneglycol dimethyl ether in step 2 is 34.6g:0.3g:17.4g:100mL.

[0031] The beneficial effects of the present application are as follows:

[0032] 1. The heat-resistant coating prepared by the present application is an environmentally friendly powder coating, which has excellent environmental friendliness.

[0033] 2. The coating uses bisphenol F type epoxy resin as the matrix, which gives the coating certain flexibility.

[0034] 3. The added heat-resistant filler is modified boron nitride, which has better compatibility with the matrix than ordinary boron nitride, and can greatly enhance the heat resistance of the coating.

[0035] 4. The heat-resistant auxiliary agent is prepared by two-step reaction, and the heat-resistant auxiliary agent molecule contains multiple functional groups, which can play a synergistic effect with the heat-resistant filler to greatly enhance the heat resistance of the material. In addition, the heat-resistant auxiliary agent can also improve the flame retardance and flexibility of the coating.

[0036] In summary, the heat-resistant coating prepared by the present application has excellent heat resistance, flame retardance and flexibility, and is environmentally friendly, which has important application value in the field of pipeline protection. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0038] Embodiment one

[0039] Preparation of heat-resistant auxiliary agent:

[0040] Step 1, 31.7 g of 3-amino-5-methylisoxazole, 0.2 g of N,N-diisopropylethylamine and 120 mL of diethylene glycol dimethyl ether were added to a three-necked flask equipped with a thermometer, a spherical condenser and an electromagnetic stirrer, and after uniform magnetic stirring, 16.1 g of ethylene trichlorosilane was added dropwise, the temperature was controlled to be not more than 20 DEG C during the dropwise addition, after the dropwise addition was completed, heating was performed to 90 DEG C, the temperature was maintained to be constant, reflux reaction was performed for 8 h, after the reaction was completed, part of the solvent was removed by distillation under reduced pressure, and then the intermediate product was purified by silica gel column chromatography (eluent: petroleum ether and ethyl acetate, volume ratio 4:1), and the eluent was removed by rotary evaporation to obtain the intermediate product.

[0041] Step 2, 34.6 g of the intermediate product, 0.3 g of azobisdimethyl isobutyronitrile, 17.4 g of 1-decanethiol and 100 mL of diethylene glycol dimethyl ether were added to a three-necked flask equipped with a thermometer, a spherical condenser and an electromagnetic stirrer, after uniform stirring, heating was performed to 80 DEG C, and the temperature of the reaction system was maintained to be constant, stirring reaction was performed for 5 h, after the reaction was completed, filtration was performed, part of the solvent was removed by distillation under reduced pressure, and then the heat-resistant auxiliary agent was purified by silica gel column chromatography (eluent: petroleum ether and ethyl acetate, volume ratio 5:1), and the eluent was removed by rotary evaporation to obtain the heat-resistant auxiliary agent.

[0042] Embodiment two

[0043] Preparation of heat-resistant auxiliary agent:

[0044] Step 1, 63.4 g of 3-amino-5-methylisoxazole, 0.4 g of N,N-diisopropylethylamine and 240 mL of diethylene glycol dimethyl ether were added to a three-necked flask equipped with a thermometer, a spherical condenser and an electromagnetic stirrer, and after uniform magnetic stirring, 32.2 g of ethylene trichlorosilane was added dropwise, the temperature was controlled to be not more than 20 DEG C during the dropwise addition, after the dropwise addition was completed, heating was performed to 90 DEG C, the temperature was maintained to be constant, reflux reaction was performed for 8 h, after the reaction was completed, part of the solvent was removed by distillation under reduced pressure, and then the intermediate product was purified by silica gel column chromatography (eluent: petroleum ether and ethyl acetate, volume ratio 4:1), and the eluent was removed by rotary evaporation to obtain the intermediate product.

[0045] Step 2, 69.2 g of the intermediate product, 0.6 g of azobisisobutyronitrile, 34.8 g of 1-decanethiol and 200 mL of diethylene glycol dimethyl ether were added into a three-necked flask equipped with a thermometer, a spherical condenser and an electromagnetic stirrer, the mixture was stirred uniformly, heated to 80°C and the temperature of the reaction system was maintained, the stirring reaction was carried out for 5 h, the reaction was completed, filtration was carried out, part of the solvent was removed by reduced pressure distillation, and then the silica gel column chromatography was used for purification (the eluent was petroleum ether and ethyl acetate, and the volume ratio was 5:1), and the eluent was removed by rotary evaporation to obtain the heat-resistant auxiliary agent.

[0046] Example Three

[0047] Preparation of heat-resistant filler:

[0048] A1, 1 g of boron nitride was added into 20 mL of concentrated nitric acid solution (concentration of 68%), stirred at 80°C for 2 h, removed surface impurities and introduced hydroxyl, washed to neutral by centrifugation, and vacuum dried to obtain pretreated boron nitride;

[0049] A2, 9.7 g of silane coupling agent KH-560 was mixed with 50 mL of ethanol aqueous solution (volume ratio of ethanol / water was 4:1), hydrochloric acid solution with a mass fraction of 8% was added dropwise, the pH of the system was adjusted to 4, and stirring was continuously carried out at room temperature for 15 min, then 1 g of pretreated boron nitride was added into the solution, mechanical stirring was carried out at a constant temperature water bath of 55°C for 8 h, the reaction was completed, centrifugal separation was carried out, washed with anhydrous ethanol for multiple times, and finally dried in a vacuum drying box and ground into powder to obtain the heat-resistant filler.

[0050] Example Four

[0051] Preparation of heat-resistant filler:

[0052] A1, 2 g of boron nitride was added into 40 mL of concentrated nitric acid solution (concentration of 68%), stirred at 80°C for 2 h, removed surface impurities and introduced hydroxyl, washed to neutral by centrifugation, and vacuum dried to obtain pretreated boron nitride;

[0053] A2, 19.4 g of silane coupling agent KH-560 was mixed with 100 mL of ethanol aqueous solution (volume ratio of ethanol / water was 4:1), hydrochloric acid solution with a mass fraction of 8% was added dropwise, the pH of the system was adjusted to 5, and stirring was continuously carried out at room temperature for 15 min, then 1 g of pretreated boron nitride was added into the solution, mechanical stirring was carried out at a constant temperature water bath of 55°C for 8 h, the reaction was completed, centrifugal separation was carried out, washed with anhydrous ethanol for multiple times, and finally dried in a vacuum drying box and ground into powder to obtain the heat-resistant filler.

[0054] Example Five

[0055] The 85 g of bisphenol F type epoxy resin was dried in a drying oven at 70 °C for 12 h, and then mixed with 7 g of the heat-resistant additive prepared in Example 1, 3 g of dicyandiamide, 8 g of the heat-resistant filler prepared in Example 3, and 2 g of magnesium stearate in a mixer at a rotating speed of 300 r / min for 10 min to obtain a mixture. The mixture was added into a twin-screw extruder for melt extrusion and tabletting, and then crushed and ground to obtain a heat-resistant coating for the inner wall of a pipeline.

[0056] Example 6

[0057] The 91 g of bisphenol F type epoxy resin was dried in a drying oven at 80 °C for 24 h, and then mixed with 12 g of the heat-resistant additive prepared in Example 2, 3 g of phthalocyanine green, 4 g of dicyandiamide, 10 g of the heat-resistant filler prepared in Example 4, and 3 g of white paraffin in a mixer at a rotating speed of 600 r / min for 20 min to obtain a mixture. The mixture was added into a twin-screw extruder for melt extrusion and tabletting, and then crushed and ground to obtain a heat-resistant coating for the inner wall of a pipeline.

[0058] Example 7

[0059] The 97 g of bisphenol F type epoxy resin was dried in a drying oven at 80 °C for 24 h, and then mixed with 17 g of the heat-resistant additive prepared in Example 2, 7 g of phthalocyanine blue, 5 g of dicyandiamide, 12 g of the heat-resistant filler prepared in Example 4, and 4 g of polyethylene wax in a mixer at a rotating speed of 600 r / min for 20 min to obtain a mixture. The mixture was added into a twin-screw extruder for melt extrusion and tabletting, and then crushed and ground to obtain a heat-resistant coating for the inner wall of a pipeline.

[0060] Comparative Example 1

[0061] A commercially available heat stabilizer was used to replace the heat-resistant additive in Example 7, and the remaining steps were the same as those in Example 7 to obtain a coating.

[0062] Comparative Example 2

[0063] A common boron nitride was used to replace the heat-resistant filler in Example 7, and the remaining steps were the same as those in Example 7 to obtain a coating.

[0064] Comparative Example 3

[0065] A commercially available epoxy resin powder coating was used.

[0066] Examples 5, 6, 7, Comparative Examples 1, 2, and 3 were subjected to the following performance tests according to different test standards:

[0067] The adhesion was determined by using the national standard GB / T 1720 “Paint film adhesion determination method”;

[0068] The national standard GB 12441 "facing type fire retardant coating" is used to determine the burning resistance time and mass loss of the sample;

[0069] The national standard GB / T 1732 "determination of impact resistance of paint film" is used to determine the impact resistance;

[0070] The national standard GB / T 1735 "determination of heat resistance of color paint and varnish" is used to determine the adhesion (GB / T 1720) of the sample after standing for 6h under the environment of 220℃.

[0071] The measured results are shown in the following table:

[0072]

[0073] From the above table, it can be seen that the heat resistance, flame resistance and flexibility of the heat-resistant coating prepared in the embodiment of the application are higher than those of the comparative examples, and therefore the application has important application value in the field of pipeline protection.

[0074] In the description of the specification, the description of the reference terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are contained in at least one embodiment or example of the application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0075] The above content is only an example and description of the application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, which should all belong to the protection scope of the application.

Claims

1. A heat-resistant coating for the inner wall of a pipe, characterized by, The raw materials include the following weight parts: 85-97 parts of bisphenol F type epoxy resin, 7-17 parts of heat-resistant additive, 0-7 parts of pigment, 3-5 parts of curing agent, 8-12 parts of heat-resistant filler, and 2-4 parts of processing aid; The heat-resistant additive is prepared by the following steps: Step 1: 3-amino-5-methylisoxazole, N,N-diisopropylethylamine and diethylene glycol dimethyl ether are added into a flask, and then ethenyltrichlorosilane is added dropwise under magnetic stirring. After the dropwise addition is completed, the mixture is heated to 90 DEG C and refluxed for 8 hours. After the reaction is completed, an intermediate product is obtained. Step 2: The intermediate product, azobisisobutyronitrile, 1-decanethiol and diethylene glycol dimethyl ether are added into a flask, and then the mixture is heated to 80 DEG C and stirred for 5 hours. After the reaction is completed, a heat-resistant additive is obtained. The heat-resistant filler is prepared by the following steps: A1: Boron nitride is added into a concentrated nitric acid solution, and stirred at 80 DEG C for 2 hours. After centrifugal washing and drying, pretreated boron nitride is obtained. A2: Silane coupling agent KH-560 is mixed with an ethanol aqueous solution, and the pH of the system is adjusted to 4-5. The mixture is continuously stirred at room temperature for 15 minutes, and then the pretreated boron nitride is added. The mixture is stirred at 55 DEG C for 8 hours. After the reaction is completed, the mixture is centrifuged, dried and ground into powder to obtain a heat-resistant filler.

2. The heat-resistant paint for the inner wall of a pipe according to claim 1, characterized by, The amount ratio of 3-amino-5-methylisoxazole, N,N-diisopropylethylamine, diethylene glycol dimethyl ether and ethenyltrichlorosilane in step 1 is 31.7g:0.2g:120mL:16.1g.

3. The heat-resistant coating for the inner wall of a pipe according to claim 1, characterized by The amount ratio of the intermediate product, azobisisobutyronitrile, 1-decanethiol and diethylene glycol dimethyl ether in step 2 is 34.6g:0.3g:17.4g:100mL.

4. The heat-resistant coating for the inner wall of a pipe according to claim 1, characterized by The amount ratio of boron nitride and concentrated nitric acid solution in step A1 is 1g:20mL.

5. The heat resistant coating for the inner wall of a pipe according to claim 1, wherein The amount ratio of silane coupling agent KH-560, ethanol aqueous solution and pretreated boron nitride in step A2 is 9.7g:50mL:1g.

6. The method for preparing a heat-resistant coating for the inner wall of a pipe according to claim 1, characterized in that, The following steps are included: The bisphenol F type epoxy resin is dried in a drying oven, and then mixed with the heat-resistant additive, pigment, curing agent, heat-resistant filler and processing aid in a mixer to obtain a mixture. The mixture is melt-extruded and pressed into a sheet in a twin-screw extruder, and then crushed and ground to obtain a heat-resistant coating for the inner wall of a pipeline.

7. The method for preparing a heat-resistant coating for the inner wall of a pipe according to claim 6, characterized in that, The processing aid is one of magnesium stearate, white paraffin and polyethylene wax.

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