High-temperature-resistant modified epoxy resin powder coating and preparation method thereof

Abstract

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

Description

Technical Field

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

[0002] Epoxy resin has excellent mechanical properties, chemical corrosion resistance, electrical insulation and good adhesion, and is widely used in adhesives, coatings, and electronics. With the development of technology, the performance of epoxy resin can no longer meet the needs of applications, and some modification methods are usually required, such as using reactive epoxy groups to react with other substances, or blending with other resins, so that the epoxy resin obtained has good mechanical properties, high temperature resistance, corrosion resistance and other advantages.

[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, defoaming agent; component B includes: dihexyltriamine, hexamethylenediamine, butanol, 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, limiting 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, talcum powder or mica powder. The invention uses alkyd resin and linear phenolic epoxy resin as base materials. The coating obtained under the joint action of other additives has good anticorrosive and antibacterial properties and strong weather resistance and heat resistance, but 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 in 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 is added into a reactor at a pressure of 2-3 MPa, and the reaction is carried out at 90-100° C. for 20-30 min. Then, azobisisobutyronitrile, allylthiourea and 2,3,3,3-tetrafluoro-1-propylene are added and the reaction is continued at 70-80° C. During the reaction, the number average molecular weight is monitored to obtain a copolymer with a number average molecular weight of 600-800.

[0011] A2, adding phenol to a reaction container, heating to 55-65° C., then adding 35-40wt% formaldehyde aqueous solution and the copolymer with a number average molecular weight of 600-800 obtained in step A1, ultrasonicating at 55-65° C. for 20-30 min, with an ultrasonic power of 60-80 W, then adjusting the pH to 2-3 with oxalic acid, heating to 85-95° C. and stirring for reaction for 2.5-3.5 h to obtain a modified phenolic resin, then adding epoxy resin to the modified phenolic resin, and continuing to stir and react 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, low volume shrinkage, etc., and is widely used in the field of coatings. However, traditional epoxy resin has insufficient high temperature resistance and cannot meet the application of high temperature environment. 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 copolymer during the preparation process 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 segments in the copolymer, which reduces the π-π stacking of benzene rings in the phenolic resin segment 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, so that the high temperature resistance of the modified epoxy resin is further improved.

[0014] In some embodiments, the mass ratio of ethylene, allylthiourea and 2,3,3,3-tetrafluoro-1-propylene 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 performance 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 reducing 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 the like 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 enables it to be evenly dispersed during the 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 invention increases the dispersibility of titanium dioxide by limiting the mass ratio of titanium dioxide, gamma-(methacryloyloxy)propyltrimethoxysilane and undecane-10-ene-1-ylphosphonic acid, while not affecting the leveling property 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 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 amount of fluorine atoms, which has 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, and the surface of the modified titanium dioxide has hydrophilic groups and long-chain hydrophobic groups, so that it can be evenly dispersed during the use of the coating. In addition, the phosphonic acid groups can undergo condensation reactions under high temperature conditions to make them tightly attached 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 only used to illustrate the present invention and are not intended to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed 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 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 all be purchased from the market, among which 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 a brand name of 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 into the reactor at a pressure of 2.5 MPa and reacted at 95° C. for 25 min. Then, 0.1 g of azobisisobutyronitrile, 15 g of allylthiourea and 12.5 g of 2,3,3,3-tetrafluoro-1-propylene were added and the reaction was continued at 75° C. During the reaction, the number average molecular weight was monitored to obtain a copolymer with a number average molecular weight of 752.

[0036] A2, 11g of phenol was added to a reaction container, the temperature was raised to 60°C, and then 10g of 37wt% formaldehyde aqueous solution and 14g of the copolymer obtained in step A1 were added, and ultrasonic treatment was performed at 60°C for 25min with an ultrasonic power of 70W. Then, the pH was adjusted to 3 with oxalic acid, the temperature was raised to 90°C and stirred for reaction for 3h to obtain a modified phenolic resin, and then 10g of E-44 bisphenol A epoxy resin was added to 6g of the modified phenolic resin, and the stirring reaction was continued for 40min 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 15 g.

[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 titanium dioxide and 5g γ-(methacryloyloxy)propyltrimethoxysilane into 100ml anhydrous ethanol and stirring at 55°C for 2.5h, then adding 4g 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 added amount of undecane-10-en-1-ylphosphonic acid 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 comprises the following steps: adding modified epoxy resin-1, dapsone and filler into an extruder, extruding at 105° C., crushing, grinding and passing 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 comprises the following steps: adding modified epoxy resin-1, dapsone and filler into an extruder, extruding at 100° C., crushing, grinding and passing 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 comprises the following steps: adding modified epoxy resin-1, dapsone and filler into an extruder, extruding at 110° C., crushing, grinding and passing 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 manner 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 manner 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 manner 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 manner 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 manner 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 manner 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 mass ratio of 5:4, coated on a tinplate of 155 mm×70 mm×0.20 mm 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 whether the coating is normal (bubbling, shedding, cracking) after 850 hours.

[0080] 3. High temperature resistance

[0081] According to GB / T1735-79 (89), place the sample at 150±2℃ for 1h and judge according to the evaluation method of failure size grade in GB / T1766-2008.

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

[0083] Table 1

[0084]

[0085] It can be seen from the experimental data of Examples 1-3 in Table 1 that the modified epoxy resin powder coating has good high temperature resistance, neutral salt spray resistance and impact resistance; it can be seen from the comparison between Examples 4 and 5 and Example 1 that the change in the ratio of ethylene, allyl thiourea and 2,3,3,3-tetrafluoro-1-propylene leads to a decrease in the mechanical properties and impact resistance of the modified epoxy resin; it can be seen from the comparison between Example 6 and Example 1 that the change in the ratio of the modified phenolic resin and the epoxy resin leads to a decrease in the various properties of the coating; it can be seen from the comparison between Example 7 and Example 1 that the epoxy resin 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; by comparing Example 8 with Example 1, it can be seen that the change in the ratio of titanium dioxide, γ-(methacryloyloxy)propyltrimethoxysilane and undecane-10-ene-1-phosphonic acid leads to a decrease in the impact strength and salt spray resistance of the coating; by comparing Example 9 with Example 1, it can be seen that without adding the copolymer, the various properties of the coating are all decreased; by comparing Comparative Example 1 with Example 1, it can be seen that the impact resistance and heat resistance of the titanium dioxide coating directly used are both decreased.

[0086] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this 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 modification, equivalent change and modification 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 still fall 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.

2. The high temperature resistant modified epoxy resin powder coating according to claim 1, characterized in that: The preparation method of the modified epoxy resin comprises the following steps: A1. Ethylene is added into a reactor at a pressure of 2-3 MPa, and the reaction is carried out at 90-100° C. for 20-30 min. Then, azobisisobutyronitrile, allylthiourea and 2,3,3,3-tetrafluoro-1-propylene are added and the reaction is continued at 70-80° C. During the reaction, the number average molecular weight is monitored to obtain a copolymer with a number average molecular weight of 600-800. A2, adding phenol to a reaction container, heating to 55-65° C., then adding 35-40wt% formaldehyde aqueous solution and the copolymer with a number average molecular weight of 600-800 obtained in step A1, ultrasonicating at 55-65° C. for 20-30 min, with an ultrasonic power of 60-80 W, then adjusting the pH to 2-3 with oxalic acid, heating to 85-95° C. and stirring for reaction for 2.5-3.5 h to obtain a modified phenolic resin, then adding epoxy resin to the modified phenolic resin, and continuing to stir and react for 30-45 min to obtain a modified epoxy resin.

3. The high temperature resistant modified epoxy resin powder coating according to claim 2, characterized in that: The mass ratio of ethylene, allylthiourea and 2,3,3,3-tetrafluoro-1-propylene is 1:(1.4-1.6):(1.2-1.3).

4. The high temperature resistant modified epoxy resin powder coating according to claim 2, characterized in that: The mass ratio of the modified phenolic resin to the epoxy resin is (0.5-0.7):

1.

5. The high temperature resistant modified epoxy resin powder coating according to claim 2, characterized in that: The epoxy resin is E-44 bisphenol A type epoxy resin.

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

7. The high temperature resistant modified epoxy resin powder coating according to claim 1, characterized in that: 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.

8. The high temperature resistant modified epoxy resin powder coating according to claim 7, characterized in that: The preparation method of the modified titanium dioxide comprises the following steps: adding titanium dioxide and γ-(methacryloyloxy)propyltrimethoxysilane into 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 the modified titanium dioxide.

9. The high temperature resistant modified epoxy resin powder coating according to claim 8, characterized in that: 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).

10. A method for preparing a high temperature resistant modified epoxy resin powder coating according to any one of claims 1 to 9, 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 sieving to obtain modified epoxy resin powder coating.

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