Preparation method of novel epoxy resin anticorrosive coating

Abstract

The present application belongs to the field of coating technology, and discloses a preparation method of a novel tough epoxy resin anticorrosive coating. A high-performance anticorrosive coating resistant to high-temperature salt mist is prepared by blending poly (phthalazinone ether) resin and epoxy resin in proportion and simultaneously compounding inorganic fillers of different particle sizes and different types under the action of a coupling agent. The addition of the inorganic fillers improves the strength of the coating and enhances the corrosion resistance of the coating in high-temperature, salt mist and other environments. The novel tough epoxy resin anticorrosive coating prepared by the preparation method has improved toughness, heat resistance and corrosion resistance of the epoxy resin coating while still maintaining the mechanical properties. Meanwhile, the preparation method is simple, the anticorrosive performance is superior, the application range is wide, and the novel tough epoxy resin anticorrosive coating has a broad application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of coating and relates to a preparation method of a high-temperature salt mist corrosion-resistant coating, in particular to a preparation method of an epoxy resin anticorrosion coating modified by heteronaphthalene diphenyl polyarylether. BACKGROUND

[0002] The epoxy resin-based coating has various excellent physical and chemical properties such as strong adhesion, excellent corrosion resistance, good thermal stability and electrical insulation, is compatible with various fillers and has low cost, and is widely applied to modern industry, construction, transportation, energy, ocean engineering, aerospace and the like. However, the cured epoxy resin has high crosslinking density, and the coating has defects such as brittleness, poor impact resistance and pores on the surface, which seriously affect the performance, so the research on the toughening modification of the epoxy resin is an innovative strategy that is widely concerned, and further promotes the wide application of the epoxy resin anticorrosion coating.

[0003] In general, thermoplastic resins are compatible with epoxy resins, and uncured epoxy resins can form a stable phase with thermoplastic resins, which are uniformly dispersed. During the curing process, the thermoplastic resin and the epoxy resin undergo phase separation, forming a two-phase structure. When the thermoplastic resin toughens the epoxy resin, it is often caused by the crack blocking (or bending) of the thermoplastic particles, the crack deflection or (and) disproportionation caused by the thermoplastic particles, the crack bridging effect of the thermoplastic particles, the shear band of the matrix, the large number of microcracks of the matrix, and the phase transition of the thermoplastic particles. These toughening mechanisms are closely related to the intrinsic properties of the system. According to Jiang M, Yong L, Cheng C, et al. Enhanced mechanical and thermal properties of monocomponent high performance epoxy resin by blending with hydroxyl terminated polyethersulfone [J]. Polymer Testing, 2018, 69: 302-309. The molecular structure of the hydroxyl-terminated polyether sulfone (PES) can improve the toughness of the epoxy resin. The fracture toughness and impact strength of the PES / EP modified mixture are increased by 32% and 9%, respectively, due to the formation of a bi-continuous structure by PES and epoxy resin, in which various toughening mechanisms such as microcracks, shear yielding, and crack pinning effect during crack propagation, bridging effect, etc. work together. Research has found that EP and PES have good dispersion compatibility and interfacial bonding ability, and the thermal stability of PES / EP blends has also been slightly improved. In addition, in order to overcome the shortcomings of pores and other defects on the surface of the epoxy resin coating, the method of modifying the epoxy resin with inorganic nano materials is used to improve the comprehensive performance of the epoxy resin-based coating. According to Zhang Rz, Wang Zyy, Wang Wb, et al. Preparation and performance of modified nano-Al2O3 / epoxy resin composite anticorrosion coating [J]. Corrosion and Protection, 2021, 42(5): 38-41. The use of silane coupling agent modified nano-Al2O3 particles in epoxy resin has prepared a modified nano-Al2O3 / epoxy resin composite anticorrosion coating. Research has found that the addition of 5% (mass fraction) of modified nano-Al2O3 particles in the epoxy resin can improve the hardness of the coating and significantly enhance the wear resistance of the coating. According to Xie F, Li Lj, Ma A, et al. Preparation and performance of modified epoxy resin marine anticorrosion coating [J]. Ship Science and Technology, 2022, 44(13): 90-95. The vanillin grafted chitosan and graphene modified epoxy resin coating can effectively improve the adhesion and weather resistance of the coating, and molecular dynamics simulation shows that the modified agent can effectively inhibit the diffusion of water molecules and improve the corrosion resistance of the coating.However, there are compatibility problems between the filler and the resin, and it is difficult for high-performance thermoplastic resin to be co-dissolved with epoxy resin in a solvent. Therefore, there is a great challenge to explore the coating formula with the best performance.

[0004] The strategy of the present application is to blend naphthalene-containing polyphenyl ether resin with epoxy resin in a certain proportion, and to prepare a high-performance corrosion-resistant coating resistant to high-temperature salt spray by compounding different particle sizes and different types of inorganic fillers under the action of a coupling agent. The polyarylether nitrile resin containing a phthalazinone structure has excellent heat resistance, mechanical properties and solubility, and can be blended with epoxy resin to achieve toughening modification by a solution method. Nano-filler blocks the pores between the molecular chains of the resin, preventing water molecules, oxygen molecules and other molecules from penetrating the coating, avoiding corrosion of the substrate, and achieving efficient corrosion protection of the high-performance coating. SUMMARY

[0005] The purpose of the present application is to develop an epoxy resin corrosion-resistant coating with strength and toughness. The present application provides a naphthalene-containing polyphenyl ether resin modified epoxy resin to improve the flexibility of the coating after curing. The addition of inorganic fillers improves the strength of the coating while enhancing the corrosion resistance of the coating in high-temperature, salt spray and other environments. While improving the toughness, heat resistance and corrosion resistance of the epoxy resin coating, its mechanical properties are still maintained.

[0006] Technical scheme of the present application:

[0007] A preparation method of a new type of tough epoxy resin corrosion-resistant coating, comprising the following steps:

[0008] (1) 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one, 4,4'-difluorobenzophenone and 2,6-difluorobenzonitrile are used as raw materials in a molar ratio of 2:1:1; K2CO3 is used as a catalyst in a molar ratio of 1:0.3:0.25, toluene is used as a water-carrying agent, and N-methyl pyrrolidone is used as a solvent, wherein the molar ratio of 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one to K2CO3 is 1:1; nucleophilic substitution polycondensation reaction is carried out, and a naphthalene-containing polyphenyl ether nitrile ketone PPENK is obtained, which is dried and stored;

[0009] (2) the E-51 resin with a molar ratio of 0.0076:0.29 is mixed with N,N-dimethylacetamide solvent and stirred, and after being fully dissolved, is sealed and stored as a mixed solution; the polyaryletherketone PPENK is added according to a mass ratio of 0.5:1 of polyaryletherketone PPENK to E-51 resin, and the curing agent 4,4'-diamino diphenyl sulfone, Al2O3, SiC, and aluminum tripolyphosphate are added according to a mass ratio of 1.4:1:2:1, wherein the mass ratio of E-51 resin to Al2O3 is 3:0.673; then, KH-560 in an amount of 1-1.5% of the E-51 resin is added, all the materials are added into a ball mill crucible, and the coating is uniformly dispersed by a ball mill to obtain a composite coating;

[0010] (3) taking tinplate and sandblasted steel as substrates, the tinplate is polished according to GB9271-2008, and the polished tinplate and the sandblasted steel plate are cleaned with anhydrous ethanol to remove surface oil stains, then a spray gun with a nozzle diameter of 2 μm is used to uniformly spray the composite coating on the substrates, after the coating surface is dry, secondary spraying is performed, and the desired thickness is obtained after repeated spraying, and then the coating is cured according to a time ratio of 90℃:150℃:180℃:230℃:280℃:300℃ of 1:1:1:3:1:0.5, after the curing is completed, the sample is taken out, placed in a ventilated environment, cooled to room temperature, and then sealed and stored.

[0011] The anti-corrosion coating prepared in the application has a flexibility of ≤0.5 mm, an impact strength of ≥100 cm, a pencil hardness of ≥7 HB, and provides a protection of more than 600 h to the substrate in a salt spray environment and more than 600 h in a high-temperature environment of 250℃.

[0012] The application has the advantages that compared with the prior art, the application develops a novel epoxy resin anti-corrosion coating with excellent flexibility, and through the addition of high-performance thermoplastic resin and inorganic fillers, the epoxy resin coating achieves the purposes of toughening and corrosion resistance, the preparation method is simple, the anti-corrosion performance is superior, the application range is wide, and the application has a broad application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 are SEM test results of various coating samples, wherein (a) is the comparative example 1, (b) is the example 2, (c) is the comparative example 1, (d) is the example 3, and (e) is the example 4.

[0014] Figure 2 are flexibility test results of the samples, wherein 1 is the comparative example 1, 2 is the example 2, 3 is the comparative example 1, 4 is the example 3, and 5 is the example 4.

[0015] Figure 3is the sample impact resistance test result, wherein 1 is Comparative Example 1; 2 is Example 2; 3 is Comparative Example 1; 4 is Example 3; 5 is Example 4.

[0016] Figure 4 is the sample thermal oxygen aging test result, (a1) is the digital photo of Comparative Example 1 before being put into the thermal oxygen aging box, (a2) is the digital photo of Comparative Example 1 after being put into the thermal oxygen aging box for 200 h, (a3) is the digital photo of Comparative Example 1 after being put into the thermal oxygen aging box for 600 h; (b1) is the digital photo of Example 2 before being put into the thermal oxygen aging box, (b2) is the digital photo of Example 2 after being put into the thermal oxygen aging box for 200 h, (b3) is the digital photo of Example 2 after being put into the thermal oxygen aging box for 600 h; (c1) is the digital photo of Example 1 before being put into the thermal oxygen aging box, (c2) is the digital photo of Example 1 after being put into the thermal oxygen aging box for 200 h, (c3) is the digital photo of Example 1 after being put into the thermal oxygen aging box for 600 h; (d1) is the digital photo of Example 3 before being put into the thermal oxygen aging box, (d2) is the digital photo of Example 3 after being put into the thermal oxygen aging box for 200 h, (d3) is the digital photo of Example 3 after being put into the thermal oxygen aging box for 600 h; (e1) is the digital photo of Example 4 before being put into the thermal oxygen aging box, (e2) is the digital photo of Example 4 after being put into the thermal oxygen aging box for 200 h, (e3) is the digital photo of Example 4 after being put into the thermal oxygen aging box for 600 h;

[0017] Figure 5are sample salt spray test results, wherein, (a1) is a digital photo of Comparative Example 1 before being put into a salt spray chamber, (a2) is a digital photo of Comparative Example 1 after being put into the salt spray chamber for 100 h, (a3) is a digital photo of Comparative Example 1 after being put into the salt spray chamber for 300 h, (a4) is a digital photo of Comparative Example 1 after being put into the salt spray chamber for 600 h; (b1) is a digital photo of Example 2 before being put into the salt spray chamber, (b2) is a digital photo of Example 2 after being put into the salt spray chamber for 100 h, (b3) is a digital photo of Example 2 after being put into the salt spray chamber for 300 h, (b4) is a digital photo of Example 2 after being put into the salt spray chamber for 600 h; (c1) is a digital photo of Example 1 before being put into the salt spray chamber, (c2) is a digital photo of Example 1 after being put into the salt spray chamber for 100 h, (c3) is a digital photo of Example 1 after being put into the salt spray chamber for 300 h, (c4) is a digital photo of Example 1 after being put into the salt spray chamber for 600 h; (d1) is a digital photo of Example 3 before being put into the salt spray chamber, (d2) is a digital photo of Example 3 after being put into the salt spray chamber for 100 h, (d3) is a digital photo of Example 3 after being put into the salt spray chamber for 300 h, (d4) is a digital photo of Example 3 after being put into the salt spray chamber for 600 h; (e1) is a digital photo of Example 4 before being put into the salt spray chamber, (e2) is a digital photo of Example 4 after being put into the salt spray chamber for 100 h, (e3) is a digital photo of Example 4 after being put into the salt spray chamber for 300 h, (e4) is a digital photo of Example 4 after being put into the salt spray chamber for 600 h;

[0018] Figure 6 are EIS test results of each coating sample, wherein, (a) is Comparative Example 1; (b) is Example 2; (c) is Example 1; (d) is Example 3; (e) is Example 4. DETAILED DESCRIPTION

[0019] The specific embodiments of the present application are further described below in conjunction with the accompanying drawings and technical solutions.

[0020] Example 1

[0021] The present embodiment provides a novel epoxy resin anticorrosive coating, and a preparation method thereof includes the following steps:

[0022] (1) In a three-necked flask equipped with mechanical stirring, nitrogen inlet and outlet, water separator and condenser, DHPZ 1 mol, 4,4'-difluorobenzophenone 1 mol, 2,6-difluorobenzonitrile 1 mol, anhydrous potassium carbonate 1 mol, N-methyl pyrrolidone (NMP) 0.3 mol, and toluene 0.25 mol were added. The nucleophilic substitution polycondensation reaction was carried out in a nitrogen environment. The temperature was controlled at 135°C, and the water was removed by azeotropic distillation for 4h; the temperature was increased to 165°C, and toluene was distilled off; the temperature was increased to 195°C, and the reaction was continued. After the viscosity of the reaction system did not increase significantly, the reaction was stopped, and a heteronaphthalene polyphenyl ether nitrile ketone PPENK was obtained, which was dried and stored.

[0023] (2) 3g of E-51 resin was mixed with 27ml of N,N-dimethylacetamide (DMAc) and stirred to dissolve completely, and then sealed and stored. According to the mass ratio of PPENK / E-51 of 0.5:1, 1.5g of PPENK was weighed, and 0.96g of 4,4'-diaminodiphenyl sulfone and 0.673g of Al2O3, 1.3461g of SiC, and 0.673g of aluminum tripolyphosphate were weighed. 40μL of KH-560 was added to the mixed solution using a pipette, and all the materials were added to a ball mill crucible, which was then placed in a ball mill to disperse the coating evenly, obtaining a composite coating.

[0024] (3) Taking tinplate and sandblasted steel as the substrate, the tinplate was polished according to GB9271-2008, and the polished tinplate and sandblasted steel plate were cleaned with anhydrous ethanol to remove surface oil stains. A spray gun with a nozzle diameter of 2μm was used to uniformly spray the coating on the substrate, and the solvent evaporation of the coating surface was observed. After the coating surface was dry to the touch, secondary spraying was performed, and the coating was cured according to the time ratio of 90°C:150°C:180°C:230°C:280°C:300°C of 1:1:1:3:1:0.5. After curing, the sample was taken out and placed in a ventilated environment to cool to room temperature, and then sealed and stored.

[0025] According to the actual filler dispersion and the corrosion protection effect of the coating, the best mass ratio of the coating formula resin is PPENK:E-51=0.5:1.

[0026] Comparative Example 1

[0027] The present comparative example provides a pure epoxy resin anticorrosive coating, and the preparation method thereof comprises the following steps:

[0028] (1) Take 3g E-51, and take 0.96g 4,4'-diamino diphenyl sulfone and 0.673g Al2O3, 1.3461g SiC, 0.673g aluminum tripolyphosphate, add 27ml DMAc, and add 40μL of KH-560 to the mixed solution with a pipette, add all materials to the ball mill crucible, and place it in the ball mill. After the coating is uniformly dispersed, the composite coating is obtained.

[0029] (2) Take the tinplate and sandblasted steel as the substrate, polish the tinplate according to GB9271-2008, and clean the polished tinplate and sandblasted steel plate with anhydrous ethanol to remove surface oil stains. Use a spray gun with a nozzle diameter of 2μm to uniformly spray the coating on the substrate, and observe the solvent evaporation of the coating surface. After the coating surface is dry, perform secondary spraying, and repeat the spraying for 3 times. According to the time ratio of 90℃: 150℃: 180℃: 230℃: 280℃: 300℃ as 1:1:1:3:1:0.5, the coating is cured. After curing, the sample is taken out and placed in a ventilated environment to cool to room temperature, and then sealed and stored.

[0030] Example 2

[0031] (1) Take 3g E-51, and take 0.96g 4,4'-diamino diphenyl sulfone and 0.673g Al2O3, 1.3461g SiC, 0.673g aluminum tripolyphosphate, add 27ml DMAc, and add 40μL of KH-560 to the mixed solution with a pipette, add all materials to the ball mill crucible, and place it in the ball mill. After the coating is uniformly dispersed, the composite coating is obtained.

[0032] (2) Take the tinplate and sandblasted steel as the substrate, polish the tinplate according to GB9271-2008, and clean the polished tinplate and sandblasted steel plate with anhydrous ethanol to remove surface oil stains. Use a spray gun with a nozzle diameter of 2μm to uniformly spray the coating on the substrate, and observe the solvent evaporation of the coating surface. After the coating surface is dry, perform secondary spraying, and repeat the spraying for 3 times. According to the time ratio of 90℃: 150℃: 180℃: 230℃: 280℃: 300℃ as 1:1:1:3:1:0.5, the coating is cured. After curing, the sample is taken out and placed in a ventilated environment to cool to room temperature, and then sealed and stored.

[0033] Example 3

[0034] (1) 3g PPENK resin was added to 3g E-51, and 0.9593g 4,4'-diamino diphenyl sulfone and 0.673g Al2O3, 1.3461g SiC, 0.673g aluminum tripolyphosphate were added, then 27ml DMAc was added, and 40μL of KH-560 was added to the mixed solution with a pipette, all materials were added to a ball mill crucible, and the coating was uniformly dispersed after being placed in a ball mill. The composite coating was obtained.

[0035] (2) Taking tinplate and sandblasted steel as the substrate, the tinplate was polished according to GB9271-2008, and the polished tinplate and sandblasted steel plate were cleaned with anhydrous ethanol to remove surface oil stains, then a spray gun with a nozzle diameter of 2μm was used to uniformly spray the coating on the substrate, and the solvent evaporation of the coating surface was observed. After the coating surface was tack-free, secondary spraying was carried out, and after repeated spraying for 3 times, the coating was cured according to the time ratio of 90℃: 150℃: 180℃: 230℃: 280℃: 300℃ as 1:1:1:3:1:0.5, and after curing, the sample was taken out and placed in a ventilated environment to cool to room temperature, and then sealed and stored.

[0036] Example 4

[0037] (1) 3g PPENK resin was added to 3g E-51, and 0.9593g 4,4'-diamino diphenyl sulfone and 0.673g Al2O3, 1.3461g SiC, 0.673g aluminum tripolyphosphate were added, then 27ml DMAc was added, and 40μL of KH-560 was added to the mixed solution with a pipette, all materials were added to a ball mill crucible, and the coating was uniformly dispersed after being placed in a ball mill. The composite coating was obtained.

[0038] (2) Taking tinplate and sandblasted steel as the substrate, the tinplate was polished according to GB9271-2008, and the polished tinplate and sandblasted steel plate were cleaned with anhydrous ethanol to remove surface oil stains, then a spray gun with a nozzle diameter of 2μm was used to uniformly spray the coating on the substrate, and the solvent evaporation of the coating surface was observed. After the coating surface was tack-free, secondary spraying was carried out, and after repeated spraying for 3 times, the coating was cured according to the time ratio of 90℃: 150℃: 180℃: 230℃: 280℃: 300℃ as 1:1:1:3:1:0.5, and after curing, the sample was taken out and placed in a ventilated environment to cool to room temperature, and then sealed and stored.

[0039] Application Example 1

[0040] It can be observed from the figures that the inorganic fillers, PPENK and E-51 mixed solution are well dispersed after ball milling, and the micron-sized aluminum tripolyphosphate and nano-sized Al2O3 and SiC500 are uniformly filled in the resin matrix. In Fig. b, it can be found that there are strip-shaped areas with less inorganic fillers, which is due to the shrinkage of E-51 during curing, causing the inorganic fillers to be pulled to the sides under stress and forming strip-shaped areas; in Fig. c, there are fewer strip-shaped areas and the fillers are uniformly dispersed, which is because the amount of PPENK added is increased, and the thermoplastic PPENK can toughen the epoxy resin through multiple effects such as nail anchor effect and bridging effect, thereby relieving the shrinkage of E-51 and reducing the internal stress. Compared with other samples, the inorganic filler density in Figs. d and e is lower, on the one hand because the proportion of inorganic fillers is diluted as the amount of PPENK added increases, and on the other hand because local inorganic fillers agglomerate, especially in Example 4, as can be seen from Fig. e, there is a large area of block structure, which is the agglomeration of inorganic fillers. The agglomeration phenomenon causes uneven dispersion in the coating, leading to poor structural stability of the coating and increased internal stress, which is more prone to generate pores or even channels, seriously affecting the various properties of the coating.

[0041] Application Example 2

[0042]

[0043] The comprehensive performance of Example 1 is the best, with a coating flexibility of ≤0.5 mm, an impact strength of ≥100 cm, a pencil hardness of ≥7 HB, and an adhesion of ≥20 MPa. The comparative example has poor flexibility, which is suspected to be due to the formation of cross or semi-cross structures between the thermoplastic PPENK and the thermosetting epoxy, which improves the flexibility of the coating; when a large amount of PPENK is added, the compatibility between the epoxy and the PPENK is poor, and local fillers agglomerate, plus the shrinkage of the epoxy under heat, which destroys the structural stability of the coating, leading to a decrease in the flexibility of the coating.

[0044] In Example 1, the impact resistance is best when the mass ratio of PPENK to E-51 is 1.5:3, because the thermoplastic resin PPENK is dispersed in the coating, and multiple mechanisms such as micro-crack, crack bridging, and thermoplastic particle phase transition work together, and the inorganic fillers and PPENK are complementary in shape, which can better fill the voids in the system, and the impact energy dispersion effect is better, thereby improving the impact toughness of the coating. However, adding too much PPENK will lead to a decrease in the impact resistance of the coating, which is due to the poor compatibility between PPENK and E-51 resin when the content of PPENK is too high, the agglomeration of inorganic fillers, and the uneven distribution of two-phase structure during curing, etc., which together increase the internal stress of the coating and reduce the impact resistance.

[0045] Application Example 3

[0046] It can be seen that Comparative Example 1 is partially blackened after 600h due to the addition of inorganic fillers only; and the composite coating of Example 1 and Example 3 after 600h at 250℃ has no obvious change. PPENK can improve the heat resistance of the epoxy coating, because PPENK also has a large number of benzene ring structures, and has good heat resistance, and can enhance the heat resistance after being blended with the epoxy resin. However, Example 2 and Example 4 are darkened after 600h, indicating that aging occurs, which can be due to the uneven dispersion of the PPENK and the epoxy resin during curing of the blended system, and the epoxy part is prone to aging, while the PPENK part has good heat resistance, resulting in darkening of the color.

[0047] Application Example 4

[0048] In order to test the corrosion resistance of the coating, the salt spray test was performed on each coating sample. According to the test results, Comparative Example 1 has improved corrosion resistance due to the addition of inorganic fillers, and the coating is partially corroded after 100h, with rust and a small amount of bubbles. It can be seen that the corrosion resistance of Examples 1, 2 and 3 is significantly enhanced after the addition of PPENK, and they can still maintain their original appearance after 100h of testing. Example 4 has poor corrosion resistance due to the poor compatibility of the added PPENK and E-51, and a small amount of rust spots appear on the surface of the coating. After 300h of salt spray testing, the surface of Comparative Example 1 is almost covered with rust; the surfaces of Examples 1 and 3 have no obvious change, indicating that the coating is completely uncorroded; the rust spots on the surfaces of Examples 2 and 4 increase, but there is no large area of rust, indicating that their corrosion resistance has also been improved. After 600h of salt spray testing, the rust spots on the surface of Comparative Example 1 deepen, indicating that corrosion is still continuing; the rust spots on the surface of Example 2 increase; only a small amount of rust spots appear on the surfaces of Examples 1 and 3, with no obvious corrosion phenomenon; the rust spots on the surface of Example 4 increase, but there is no obvious increase in rust.

[0049] Application Example 5

[0050]

[0051] The degree of scratching on the surface of each sample after 100,000 times of wiping with NMP solvent. Comparative Example 1 and Example 4 have slight traces, and have good solvent resistance; the other coating samples have no obvious traces, and have the best solvent resistance; it can be shown that the addition of PPENK to the epoxy coating can greatly improve the solvent resistance of the coating, because PPENK and inorganic fillers can well fill the pores of the coating, making the structure more dense, and the solvent less likely to penetrate the coating, thereby enhancing the solvent resistance. However, too much PPENK can result in poor solvent resistance, because the compatibility of PPENK and E-51 becomes poor, and the dispersion of PPENK and inorganic fillers becomes poor, resulting in agglomeration and poor solvent resistance.

[0052] Example 6

[0053] EIS test results of each coating sample immersed in 3.5% NaCl solution for different times. The initial resistance of Comparative Example 1 is high, and the resistance decreases slightly after 3 days of immersion, and can still be maintained at 10 5 Ω·cm 2 The above is because the inorganic filler is well dispersed in the epoxy resin, reducing the penetration of corrosion medium and improving the corrosion resistance of the coating. The initial resistance of Example 2 is significantly improved, indicating that PPENK can significantly improve the electrical insulation of the coating, but the resistance decreases rapidly with the immersion time, and even lower than Comparative Example 1 after 5 days of immersion, indicating that the addition of PPENK is not obvious when the amount of coating is less. The resistance of Example 1 can still be maintained at 10 9 Ω·cm 2 or so, without obvious decrease, indicating that PPENK can significantly enhance the permeability and corrosion resistance of the epoxy coating.

[0054] From the above analysis, it can be seen that the addition of PPENK can significantly enhance the corrosion resistance of the epoxy resin coating, and the corrosion resistance of the coating is the strongest when the mass ratio of PPENK / E-51 is 1.5:3, and the corrosion resistance is also improved when the amount of PPENK is less or too much, but the enhancement effect is weak due to the inhomogeneous two-phase structure caused by the poor compatibility and the small amount of PPENK.

Claims

1. A method for preparing a novel epoxy resin anticorrosive coating, characterized by, The steps are as follows: (1) 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one, 4,4'-difluorobenzophenone and 2,6-difluorobenzonitrile are used as raw materials; K2CO3 is used as a catalyst, toluene is used as a water-carrying agent, and N-methylpyrrolidone is used as a solvent; a nucleophilic substitution polycondensation reaction is carried out to obtain a heteronaphthalene biphenyl polyarylene ether nitrile ketone PPENK, which is dried and stored; (2) After the E-51 resin and N,N-dimethylacetamide solvent are mixed and stirred, they are fully dissolved and then sealed and stored as a mixed solution; the heteronaphthalene biphenyl polyarylene ether nitrile ketone PPENK and the curing agent 4,4'-diaminodiphenyl sulfone, Al2O3, SiC, aluminum tripolyphosphate are added, and then KH-560 is added; all the materials are put into a ball mill crucible, and then the coating is uniformly dispersed by a ball mill to obtain a composite coating; (3) The tinplate and sandblasted steel are used as substrates, the tinplate is polished according to GB9271-2008, and the polished tinplate and sandblasted steel plate are cleaned with anhydrous ethanol to remove surface oil stains; a spray gun with a nozzle diameter of 2 μm is used to uniformly spray the composite coating on the substrate; after the coating surface is dry, secondary spraying is carried out, and the required thickness is obtained after repeated spraying; the coating is cured, and after the curing is completed, the sample is taken out and placed in a ventilated environment to cool to room temperature, and then sealed and stored; In step (2), The molar ratio of E-51 resin to N,N-dimethylacetamide solvent is 0.0076:0.29; The mass ratio of heteronaphthalene biphenyl polyarylene ether nitrile ketone PPENK to E-51 resin is 0.5:1; The mass ratio of 4,4'-diaminodiphenyl sulfone, Al2O3, SiC, and aluminum tripolyphosphate is 1.4:1:2:1; The mass ratio of E-51 resin to Al2O3 is 3:0.673; The mass ratio of KH-560 to E-51 resin is 1-1.5%.

2. The preparation method of the novel tough epoxy resin anticorrosive coating layer according to claim 1, characterized in that, In step (1), The molar ratio of 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one, 4,4'-difluorobenzophenone and 2,6-difluorobenzonitrile is 2:1:1; The molar ratio of K2CO3, toluene and N-methylpyrrolidone is 1:0.3:0.25; The molar ratio of 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one to K2CO3 is 1:

1.

3. The preparation method of the novel tough epoxy resin anticorrosive coating layer according to claim 1, characterized in that, In step (3), The coating curing conditions are as follows: the temperature is 90℃, 150℃, 180℃, 230℃, 280℃ and 300℃, and the corresponding time ratio is 1:1:1:3:1:0.5, and the coating is cured in sequence by increasing the temperature.

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