A high temperature resistant modified epoxy resin powder coating and preparation method thereof

Abstract

The present invention relates to the technical field of chemical coatings, specifically to a high-temperature-resistant modified epoxy resin powder coating and a preparation method thereof. The powder coating comprises the following raw materials, by weight: 42-44 parts of a modified epoxy resin, 19-21 parts of a curing agent, and 35-38 parts of a filler. The coating prepared by the present invention exhibits good heat resistance, corrosion resistance, and excellent mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical coatings, and in particular to a powder coating of a high-temperature-resistant modified epoxy resin and a preparation method thereof. Background Art

[0002] Epoxy resins possess excellent mechanical properties, chemical resistance, electrical insulation, and good adhesion, and are widely used in adhesives, coatings, and electronics. However, with technological advancements, the performance of epoxy resins has outstripped the demands of current applications, necessitating modifications such as utilizing reactive epoxy groups to react with other substances or blending with other resins to enhance the resulting epoxy resin's mechanical properties, high-temperature resistance, and corrosion resistance.

[0003] Patent CN103289502B discloses a corrosion-resistant epoxy resin coating, including component A and component B. Component A includes bisphenol epoxy resin, polyamide resin, E-44 epoxy resin, silane coupling agent, zeolite powder, sodium antimonate, modified bamboo powder, epoxy soybean oil, dibutyl ester, anti-settling agent, leveling agent, dispersant, and defoaming agent; component B includes: dihexyltriamine, hexamethylenediamine, butanol, and xylene. The coating obtained by limiting the weight ratio of component A to component B has high adhesion, good corrosion resistance, and excellent mechanical properties, but may have poor high temperature resistance, which limits its scope of application.

[0004] Patent CN103382354B discloses an anticorrosive and antibacterial phenolic epoxy resin powder coating, which includes the following raw materials: linear phenolic epoxy resin, semi-drying oil alkyd resin, filler, titanium dioxide, nano titanium dioxide, ammonium dihydrogen phosphate, 2-phenylimidazoline, polyacrylate-2-ethylhexyl leveling agent, 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethylene]-4,6-di-tert-pentylphenyl acrylate; the filler used is heavy calcium carbonate, talc or mica powder. The invention uses alkyd resin and linear phenolic epoxy resin as base materials. The coating obtained with the combined action of other additives has good anticorrosive and antibacterial properties and strong weather resistance and heat resistance. However, the filler of the invention is easy to agglomerate, which easily causes uneven dispersion and affects the mechanical properties of the coating.

[0005] Therefore, there is an urgent need on the market for a modified epoxy resin powder coating with good mechanical properties and high temperature resistance. Summary of the Invention

[0006] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a modified epoxy resin powder coating having good high temperature resistance, corrosion resistance and excellent mechanical properties.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] The first aspect of the present invention provides a high-temperature resistant modified epoxy resin powder coating, which comprises the following raw materials in parts by weight: 42-44 parts of modified epoxy resin, 19-21 parts of curing agent, and 35-38 parts of filler.

[0009] In some embodiments, the method for preparing the modified epoxy resin comprises the following steps:

[0010] A1. Ethylene was added to a reactor at a pressure of 2-3 MPa, and the reaction was carried out at 90-100° C. for 20-30 min. Then, azobisisobutyronitrile, allylthiourea, and 2,3,3,3-tetrafluoro-1-propene were added and the reaction was continued at 70-80° C. The number average molecular weight was monitored during the reaction to obtain a copolymer with a number average molecular weight of 600-800.

[0011] A2. Phenol was added to a reaction vessel and the temperature was raised to 55-65° C., followed by the addition of a 35-40 wt % formaldehyde aqueous solution and the copolymer with a number average molecular weight of 600-800 obtained in step A1. The mixture was ultrasonically reacted at 55-65° C. for 20-30 min with an ultrasonic power of 60-80 W. The pH was then adjusted to 2-3 with oxalic acid, and the temperature was raised to 85-95° C. with stirring for 2.5-3.5 h to obtain a modified phenolic resin. An epoxy resin was then added to the modified phenolic resin, and the reaction was continued with stirring for 30-45 min to obtain a modified epoxy resin.

[0012] Preferably, the mass ratio of the phenol, the 35-40 wt% formaldehyde aqueous solution and the copolymer with a number average molecular weight of 600-800 obtained in step A1 is (1-1.2):1:(1.3-1.5).

[0013] Epoxy resin has the advantages of high hardness, high bonding strength, and low volume shrinkage, and is widely used in the field of coatings. However, traditional epoxy resin has insufficient high temperature resistance and cannot meet the application requirements of high temperature environments. People in this field usually use phenolic resin to modify epoxy resin to improve the high temperature resistance of epoxy resin, but phenolic resin is relatively brittle. The present invention obtains modified phenolic resin by adding a copolymer during the preparation of phenolic resin. The modified epoxy resin obtained by modifying epoxy resin with modified phenolic resin has good high temperature resistance, corrosion resistance and excellent mechanical properties. This may be due to the addition of freely movable alkane chain segments in the copolymer, which reduces the π-π stacking of benzene rings in the phenolic resin chain segments and reduces brittleness. In addition, the copolymer contains a large number of fluorine atoms, has greater inertness and stronger electronegativity, and enhances the corrosion resistance of the modified epoxy resin. Moreover, the presence of thiourea increases the crosslinking degree and heat resistance of the epoxy resin to a certain extent, thereby further improving the high temperature resistance of the modified epoxy resin.

[0014] In some embodiments, the mass ratio of ethylene, allylthiourea and 2,3,3,3-tetrafluoro-1-propene is 1:(1.4-1.6):(1.2-1.3).

[0015] The invention increases the toughness of the modified phenolic resin by adjusting the mass ratio of ethylene, allylthiourea and 2,3,3,3-tetrafluoro-1-propylene without reducing the inherent properties of the phenolic resin.

[0016] In some embodiments, the mass ratio of the modified phenolic resin to the epoxy resin is (0.5-0.7):1.

[0017] The invention limits the mass ratio of the modified phenolic resin to the epoxy resin so that the modified phenolic resin modifies the epoxy resin, thereby improving the heat resistance of the epoxy resin and preventing the phenomenon of excessive crosslinking and reduction of the mechanical strength of the modified epoxy resin.

[0018] In some embodiments, the epoxy resin is E-44 bisphenol A epoxy resin.

[0019] In some embodiments, the curing agent is dapsone.

[0020] In some embodiments, the filler is barium sulfate, modified titanium dioxide, silicon carbide, and strontium sulfate, and the mass ratio of the four is (20-23): (9-11): (1-2): 1.

[0021] In some embodiments, the preparation method of the modified titanium dioxide comprises the following steps: adding titanium dioxide and γ-(methacryloyloxy)propyltrimethoxysilane to anhydrous ethanol and stirring at 50-60° C. for 2-3 hours, then adding undecane-10-en-1-ylphosphonic acid, filtering, washing, and drying to obtain modified titanium dioxide.

[0022] Adding titanium dioxide to the coating can increase the wear resistance and adhesion of the coating, but the dispersibility of titanium dioxide in the system is poor and it is easy to agglomerate, resulting in uneven adhesion between the coating and the substrate, and bubbles, shedding and other phenomena may occur. The present invention modifies titanium dioxide so that titanium dioxide can be evenly dispersed in the coating, while increasing the high temperature resistance and mechanical strength of the coating. This may be because the surface of the modified titanium dioxide has hydrophilic groups and long-chain hydrophobic groups, which enable it to be evenly dispersed during use of the coating. In addition, when the phosphonic acid group undergoes a condensation reaction under high temperature conditions, it is tightly attached to the resin, further increasing the high temperature resistance and wear resistance. In addition, the silicon-oxygen bond also further enhances the toughness of the coating.

[0023] In some embodiments, the mass ratio of titanium dioxide, γ-(methacryloyloxy)propyltrimethoxysilane and undec-10-en-1-ylphosphonic acid is 1:(0.4-0.6):(0.3-0.5).

[0024] The present invention increases the dispersibility of titanium dioxide by limiting the mass ratio of titanium dioxide, gamma-(methacryloyloxy)propyltrimethoxysilane and undec-10-en-1-ylphosphonic acid, while not affecting the leveling and stability of the coating.

[0025] The second aspect of the present invention provides a method for preparing a high-temperature resistant modified epoxy resin powder coating, comprising the following steps: adding modified epoxy resin, curing agent and filler into an extruder, extruding at 100-110°C, crushing, grinding and sieving to obtain a modified epoxy resin powder coating.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention modifies epoxy resin and titanium dioxide to obtain a powder coating having good high temperature resistance, corrosion resistance and excellent mechanical properties.

[0028] 2. The present invention obtains a modified phenolic resin by adding a copolymer during the preparation of a phenolic resin. The modified epoxy resin obtained by modifying the epoxy resin with the modified phenolic resin has good high temperature resistance, corrosion resistance and excellent mechanical properties. On the one hand, due to the addition of freely movable alkane segments in the copolymer, the π-π stacking of benzene rings in the phenolic resin segments is reduced, thereby reducing brittleness. In addition, the copolymer contains a large number of fluorine atoms, which have greater inertness and stronger electronegativity, thereby enhancing the corrosion resistance of the modified epoxy resin. Moreover, the presence of thiourea increases the crosslinking degree and heat resistance of the epoxy resin to a certain extent, thereby further improving the high temperature resistance of the modified epoxy resin.

[0029] 3. The present invention modifies titanium dioxide. The modified titanium dioxide has hydrophilic groups and long-chain hydrophobic groups on its surface, which enables it to be evenly dispersed during use in the coating. In addition, the phosphonic acid groups can undergo condensation reactions under high temperature conditions to make them tightly adhere to the resin, further increasing the high temperature resistance and wear resistance. In addition, the silicon-oxygen bonds also further enhance the toughness of the coating. DETAILED DESCRIPTION

[0030] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following examples and comparative examples are intended only to illustrate the present invention and are not intended to limit the present invention. Other combinations and various modifications within the scope of the present invention may be made without departing from the spirit or scope of the present invention.

[0031] In order to facilitate those skilled in the art to implement the present invention, some of the raw materials and manufacturers of the embodiments and comparative examples are described as follows:

[0032] The compounds and related reagents used in the following examples and comparative examples can be purchased from the market. Among them, E-44 and E51 bisphenol A epoxy resins were purchased from Jinan Qingtian Chemical Technology Co., Ltd.; titanium dioxide was purchased from Shanghai Yantai E-Commerce Co., Ltd. with the brand name GR8598.

[0033] Preparation Example 1

[0034] The preparation method of modified epoxy resin-1 comprises the following steps:

[0035] A1. 10 g of ethylene was added to a reactor at a pressure of 2.5 MPa and the reaction was carried out at 95° C. for 25 min. 0.1 g of azobisisobutyronitrile, 15 g of allylthiourea, and 12.5 g of 2,3,3,3-tetrafluoro-1-propene were then added and the reaction was continued at 75° C. The number average molecular weight was monitored during the reaction to obtain a copolymer with a number average molecular weight of 752.

[0036] A2. 11 g of phenol was added to a reaction vessel, and the temperature was raised to 60° C., followed by the addition of 10 g of a 37 wt % aqueous formaldehyde solution and 14 g of the copolymer obtained in step A1. The mixture was ultrasonically treated at 60° C. for 25 min at an ultrasonic power of 70 W. The pH was then adjusted to 3 with oxalic acid, and the mixture was heated to 90° C. and stirred for 3 h to obtain a modified phenolic resin. 10 g of E-44 bisphenol A epoxy resin was then added to 6 g of the modified phenolic resin, and the reaction was continued with stirring for 40 min to obtain a modified epoxy resin-1.

[0037] Preparation Example 2

[0038] The preparation method of modified epoxy resin-2 has the same specific steps as Preparation Example 1, except that the added amount of 2,3,3,3-tetrafluoro-1-propylene is 15g.

[0039] Preparation Example 3

[0040] The preparation method of modified epoxy resin-3 has the same specific steps as Preparation Example 1, except that the amount of allylthiourea added is 19 g.

[0041] Preparation Example 4

[0042] The preparation method of modified epoxy resin-4 has the same specific steps as Preparation Example 1, except that the amount of modified phenolic resin added is 9g.

[0043] Preparation Example 5

[0044] The preparation method of modified epoxy resin-5 has the same specific steps as Preparation Example 1, except that the epoxy resin used is E-51 bisphenol A type epoxy resin.

[0045] Preparation Example 6

[0046] The preparation method of modified epoxy resin-6 has the same specific steps as Preparation Example 1, except that no copolymer is added.

[0047] Preparation Example 7

[0048] The preparation method of modified titanium dioxide-1 includes the following steps: adding 10g of titanium dioxide and 5g of γ-(methacryloyloxy)propyltrimethoxysilane to 100ml of anhydrous ethanol and stirring at 55°C for 2.5h, then adding 4g of undecane-10-en-1-ylphosphonic acid, filtering, washing, and drying to obtain modified titanium dioxide-1.

[0049] Preparation Example 8

[0050] The preparation method of modified titanium dioxide-2 has the same specific steps as Preparation Example 7, except that the amount of undecane-10-en-1-ylphosphonic acid added is 6 g.

[0051] Example 1

[0052] A high-temperature resistant modified epoxy resin powder coating comprises the following raw materials, measured in parts by weight: 43 parts of modified epoxy resin-1, 20 parts of dapsone, and 36 parts of filler; the filler is barium sulfate, modified titanium dioxide-1, silicon carbide, and strontium sulfate, and the mass ratio of the four is 21:10:1.5:1.

[0053] The preparation method of the high-temperature resistant modified epoxy resin powder coating in this embodiment includes the following steps: adding modified epoxy resin-1, dapsone and filler into an extruder and extruding at 105°C, crushing, and grinding through a 200-mesh sieve to obtain a modified epoxy resin powder coating.

[0054] Example 2

[0055] A high-temperature resistant modified epoxy resin powder coating comprises the following raw materials, measured in parts by weight: 42 parts of modified epoxy resin-1, 19 parts of dapsone, and 35 parts of filler; the filler is barium sulfate, modified titanium dioxide-1, silicon carbide, and strontium sulfate, and the mass ratio of the four is 20:10:1:1.

[0056] The preparation method of the high-temperature resistant modified epoxy resin powder coating in this embodiment includes the following steps: adding modified epoxy resin-1, dapsone and filler into an extruder and extruding at 100°C, crushing, and grinding through a 200-mesh sieve to obtain a modified epoxy resin powder coating.

[0057] Example 3

[0058] A high-temperature resistant modified epoxy resin powder coating comprises the following raw materials, measured in parts by weight: 44 parts of modified epoxy resin-1, 21 parts of dapsone, and 38 parts of filler; the filler is barium sulfate, modified titanium dioxide-1, silicon carbide, and strontium sulfate, and the mass ratio of the four is 23:11:2:1.

[0059] The preparation method of the high-temperature resistant modified epoxy resin powder coating in this embodiment includes the following steps: adding modified epoxy resin-1, dapsone and filler into an extruder and extruding at 110°C, crushing, and grinding through a 200-mesh sieve to obtain a modified epoxy resin powder coating.

[0060] Example 4

[0061] A high-temperature resistant modified epoxy resin powder coating and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified epoxy resin-1 is replaced by modified epoxy resin-2.

[0062] Example 5

[0063] A high-temperature resistant modified epoxy resin powder coating and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified epoxy resin-1 is replaced by modified epoxy resin-3.

[0064] Example 6

[0065] A high-temperature resistant modified epoxy resin powder coating and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified epoxy resin-1 is replaced by modified epoxy resin-4.

[0066] Example 7

[0067] A high-temperature resistant modified epoxy resin powder coating and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified epoxy resin-1 is replaced by modified epoxy resin-5.

[0068] Example 8

[0069] A high-temperature resistant modified epoxy resin powder coating and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified epoxy resin-1 is replaced by modified epoxy resin-6.

[0070] Example 9

[0071] A high-temperature resistant modified epoxy resin powder coating and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified titanium dioxide-1 is replaced by modified titanium dioxide-2.

[0072] Comparative Example 1

[0073] A high-temperature resistant modified epoxy resin powder coating and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified titanium dioxide-1 is replaced by titanium dioxide.

[0074] Performance Testing

[0075] The modified epoxy resin powder coating obtained in each embodiment and comparative example was mixed with water in a coating to water mass ratio of 5:4, coated on a 155 mm × 70 mm × 0.20 mm tinplate with a thickness of 70 μm, and cured at 200° C. for 24 h to obtain a sample.

[0076] 1. Impact strength

[0077] According to the standard GB / T1732-2020, the impact strength of each sample was tested using a GS-CJQD impact strength testing machine.

[0078] 2. Neutral salt spray resistance

[0079] According to the standard GB / T1771-2007, observe the coating after 850 hours to see if it is normal (bubbling, shedding, cracking).

[0080] 3. High temperature resistance

[0081] According to GB / T1735-79 (89), the specimens were placed at 150±2℃ for 1h and the damage grade was evaluated according to the evaluation method of GB / T1766-2008.

[0082] The test results are shown in Table 1.

[0083] Table 1

[0084]

[0085] From the experimental data of Examples 1-3 in Table 1, it can be seen that the modified epoxy resin powder coating has good high temperature resistance, neutral salt spray resistance and impact resistance; compared with Example 1, it can be seen that the ratio of ethylene, allyl thiourea and 2,3,3,3-tetrafluoro-1-propylene is changed, resulting in reduced mechanical properties and impact resistance of the modified epoxy resin; compared with Example 1, it can be seen that the ratio of modified phenolic resin and epoxy resin is changed, and the performance of the coating is reduced; compared with Example 1, it can be seen that the ratio of epoxy resin is changed. The model change leads to changes in the mechanical properties of the modified epoxy resin and a decrease in the impact resistance of the coating; compared with Example 1, Example 8 shows that the ratio of titanium dioxide, γ-(methacryloyloxy)propyltrimethoxysilane and undec-10-en-1-phosphonic acid is changed, resulting in a decrease in the impact strength and salt spray resistance of the coating. Compared with Example 1, Example 9 shows that without adding the copolymer, the various properties of the coating are reduced; compared with Comparative Example 1 and Example 1, the impact resistance and heat resistance of the titanium dioxide coating directly used are reduced.

[0086] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A high temperature resistant modified epoxy resin powder coating, characterized in that: The composition comprises the following raw materials in parts by weight: 42-44 parts of modified epoxy resin, 19-21 parts of curing agent, and 35-38 parts of filler; The preparation method of the modified epoxy resin comprises the following steps: A1. Ethylene was added to a reactor at a pressure of 2-3 MPa, and the reaction was carried out at 90-100° C. for 20-30 min. Then, azobisisobutyronitrile, allylthiourea, and 2,3,3,3-tetrafluoro-1-propene were added and the reaction was continued at 70-80° C. The number average molecular weight was monitored during the reaction to obtain a copolymer with a number average molecular weight of 600-800. A2, phenol was added to a reaction vessel, and the temperature was raised to 55-65 ° C., followed by addition of 35-40 wt% formaldehyde aqueous solution and a copolymer with a number average molecular weight of 600-800 obtained in step A1, and ultrasonication was performed at 55-65 ° C. for 20-30 min with an ultrasonic power of 60-80 W. The pH was then adjusted to 2-3 with oxalic acid, and the temperature was raised to 85-95 ° C. and stirred for 2.5-3.5 h to obtain a modified phenolic resin. An epoxy resin was then added to the modified phenolic resin, and the stirring reaction was continued for 30-45 min to obtain a modified epoxy resin. The mass ratio of ethylene, allylthiourea and 2,3,3,3-tetrafluoro-1-propylene is 1:(1.4-1.6):(1.2-1.3); The mass ratio of the modified phenolic resin to the epoxy resin is (0.5-0.7):1; The epoxy resin is E-44 bisphenol A epoxy resin; The fillers are barium sulfate, modified titanium dioxide, silicon carbide, and strontium sulfate, and the mass ratio of the four is (20-23): (9-11): (1-2): 1; The preparation method of the modified titanium dioxide comprises the following steps: adding titanium dioxide and γ-(methacryloyloxy)propyltrimethoxysilane to anhydrous ethanol and stirring at 50-60° C. for 2-3 hours, then adding undec-10-en-1-ylphosphonic acid, filtering, washing, and drying to obtain the modified titanium dioxide; The mass ratio of the titanium dioxide, γ-(methacryloyloxy)propyltrimethoxysilane and undec-10-en-1-ylphosphonic acid is 1:(0.4-0.6):(0.3-0.5).

2. The high temperature resistant modified epoxy resin powder coating according to claim 1, characterized in that: The curing agent is dapsone.

3. A method for preparing a high temperature resistant modified epoxy resin powder coating according to any one of claims 1 to 2, characterized in that: The method comprises the following steps: adding modified epoxy resin, curing agent and filler into an extruder, extruding at 100-110 DEG C, crushing, grinding and screening to obtain modified epoxy resin powder coating.

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