NL2031236B1

NL2031236B1 - Tung oil-based modified amine curing agent and preparation method and use thereof

Info

Publication number: NL2031236B1
Application number: NL2031236A
Authority: NL
Inventors: Li Mei; Li Shouhai; Zhang Yan; Chen Yao; Ding Haiyang; Yang Xiaohua; Zhu Jinhua; Xia Jianling
Original assignee: Inst Chemical Ind Forest Products Caf
Priority date: 2021-04-08
Filing date: 2022-03-10
Publication date: 2023-07-10
Also published as: CN113265038B; NL2031236A; CN113265038A

Abstract

Tung oil-based modified amine curing agent and preparation method and use thereof A tung oil-based modified amine curing agent and a preparation method and use thereof. Methyl 5 eleostearate, phenol and a catalyst are added into a reaction vessel, in a state of continuously introducing nitrogen the mixture is stirred and heated for a reaction, the reaction is cooled, washed and allowed to stand, and an upper brown viscous liquid is dried with anhydrous sodium sulfate to obtain a tung oil-derived phenolic adduct; the tung oil-derived phenolic adduct and polyamine are added into a reaction vessel, and mixed and stirred uniformly, an aldehyde is dropwise added, and 10 after the dropwise addition is completed, the mixture is heated for a reaction, and then reduced-pressure distillation is performed to remove the generated water, to obtain a tung oil-based lVlannich base curing agent; and in a stirring state, polyamine is further dropwise added to the tung oil-based lVlannich base curing agent, the mixture is heated and refluxed and then subjected to an amidation reaction, and when no water or free amine is distilled out, the heating is 15 stopped, and the remainder is cooled to room temperature to obtain a dark brown viscous tung oil-based modified amine curing agent. The active cross-linking points of a curing reaction of the tung oil-based modified amine curing agent are distributed more extensively and uniformly, and a better balance can be achieved between the hardness and flexibility of a coating, so that the coating is tougher.

Description

TUNG OIL-BASED MODIFIED AMINE CURING AGENT AND PREPARATION METHOD AND USE

THEREOF

TECHNICAL FIELD

[0001] The present invention belongs to the field of thermosetting resin materials, and in particular to a tung oil-based modified amine curing agent and a preparation method and use thereof.

BACKGROUND

[0002] An epoxy resin/curing agent system has good processability, and the cured epoxy products have high bonding strength due to the polar groups such as epoxy groups, hydroxyl groups, ester bonds, amine bonds and ester bonds that have great activity as well as their own strong cohesion. In addition, the cured epoxy products can be used as casting materials, laminating materials, adhesives, coatings and the like because of good dimensional stability, low shrinkage, good electrical insulating properties, high mechanical strength, good solvent resistance, etc. A curing agent plays a decisive role in the performance of an epoxy resin anticorrosive coating, and thus it is essential to select a proper curing agent. A polyamide curing agent and epoxy resin can be cured into a film at room temperature, and the film has good corrosion resistance, flexibility and recoatability; a cardanol-Mannich amide curing agent has low viscosity and good low-temperature curing property, and a film thereof has good water resistance; and the two are now extensively used in epoxy anticorrosive coatings. However, in recent years, corrosion of lots of equipment in the severe environment of high salt fog and high humidity and heat in marine areas reflects prevailing shortcomings of high brittleness and poor impact toughness of traditional epoxy anticorrosive coatings. In long-term use, under the impact of aging, alternate changes in temperature and alternate changes in humidity, microcracks are prone to occur in materials which lead to problems such as decrease in shock resistance and permeation of corrosive media, and thus the use of the polyamide curing agent and the cardanol-Mannich amide curing agent is gradually restricted. In addition, a general toughening means directly causes a decrease in the strength of the cured epoxy resin and the resistance to media such as oil. Therefore, it is of great significance to develop a curing agent with high corrosion resistance and high impact toughness for epoxy resin. From design of a molecular structure, this study synthesizes a novel tung oil-based modified amine curing agent integrating the good flexibility and corrosion resistance of the polyamide curing agent and the good low-temperature curing property and water resistance of the cardanol-Mannich amide curing agent, for use in the field of epoxy anticorrosive coatings.

SUMMARY

[0003] Technical problems to be solved: The present invention provides a tung oil-based modified amine curing agent and a preparation method and use thereof. Through design of the molecular structure, the molecular structure of the tung oil-based modified amine curing agent has both a flexible structure of a long carbon chain of tung oil and active groups such as phenolic hydroxyl, secondary amino and primary amino of Mannich amide and a polar amide group of polyamide, so that a cured epoxy coating integrates the good flexibility and corrosion resistance of polyamide and the low-temperature curing property and good water resistance of cardanol-Mannich amide and can be used as an anticorrosive coating. Compared with a polyamide curing agent and a cardanol-Mannich amide curing agent, the active cross-linking points of a curing reaction of the tung oil-based modified amine curing agent are distributed more extensively and uniformly, and a better balance can be achieved between the hardness and flexibility of a coating so that the coating is tougher. In addition, a problem of poorer corrosion resistance of the polyamide curing agent and the cardanol-Mannich amide curing agent caused by simple physical mixing can be avoided. An idea and approach are provided for deep processing of a bio-based material of tung oil, and the application area of the tung oil can be widened while the added value thereof is increased.

[0004] Technical solution: A method for preparing a tung oil-based modified amine curing agent, comprising the following steps according to the following proportions: Step 1: 0.5 mol of methyl eleostearate, 0.51-0.55 mol of phenol and 0.3-0.4 wt.% of a catalyst based on the methyl eleostearate are added into a reaction vessel; in a state of continuously introducing nitrogen, the mixture is stirred and heated to 90-120°C, and continuously reacted for 2-3 hours at the temperature; the reaction is naturally cooled to room temperature, washed by adding 5 wt.% of an aqueous solution of NaOH and a saturated saline solution sequentially, and allowed to stand and layered for 3 times; and an upper brown viscous liquid is obtained and dried with anhydrous sodium sulfate to obtain a tung oil-derived phenolic adduct; Step 2: 0.4-0.5 mol of the tung oil-derived phenolic adduct and 0.4-0.5 mol of polyamine are added into a reaction vessel, and mixed and stirred uniformly; 0.4-0.5 mol of an aldehyde is dropwise added while the temperature is controlled at or below 60°C; after the dropwise addition is completed, the mixture is heated to 85-95°C, and reacted for 3-4 hours; and then reduced-pressure distillation is performed to remove the generated water, to obtain a tung oil-based Mannich base curing agent; and Step 3: in a stirring state, 0.44-0.55 mol of polyamine is further dropwise added to the tung oil-based Mannich base curing agent; the mixture is heated to 135-145°C, refluxed and held for 1-2 hours, then heated to 180-190°C for an amidation reaction and held for 1-2 hours, and finally, held for 1-1.5 hours at 0.67-1.33 kPa; and when no water or free amine is distilled out, the heating is stopped, and the remainder is cooled to room temperature to obtain a dark brown viscous tung oil-based modified amine curing agent.

[0005] In Step 1, the phenol is any one selected from phenol, cresol, p-tert-butylphenol, bisphenol A and maleimide phenol.

[0006] In Step 1, the catalyst is any one selected from AlCl3, p-toluenesulfonic acid and

H3POs.

[0007] In Step 2, the polyamine is at least one selected from hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, m-xylylenediamine and 1,3-cyclohexyldimethylamine.

[0008] In Step 2, the aldehyde is at least one selected from formaldehyde, n-butylaldehyde, iso-butyraldehyde, furfural and benzaldehyde.

[0009] In Step 3, the polyamine is at least one selected from hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, m-xylylenediamine, 4,4’-diaminodicyclohexyl methane and 1,3-cyclohexyldimethylamine.

[0010] A tung oil-based modified amine curing agent prepared by the method.

[0011] Use of the tung oil-based modified amine curing agent in preparing an epoxy anticorrosive coating.

[0012] Beneficial effects: The tung oil-based modified amine curing agent has good compatibility with epoxy resin and a moderate reaction speed. The molecular structure of the tung oil-based modified amine curing agent has both a flexible structure of a long carbon chain of tung oil and active groups such as phenolic hydroxyl, secondary amino and primary amino of Mannich amide and a polar amide group of polyamide, so that a cured epoxy coating integrates the good flexibility and corrosion resistance of polyamide and the low-temperature curing property and good water resistance of cardanol-Mannich amide. Compared with a polyamide curing agent and a cardanol-Mannich amide curing agent, the active cross-linking points of a curing reaction of the tung oil-based modified amine curing agent are distributed more extensively and uniformly, and a better balance can be achieved between the hardness and flexibility of a coating; and the prepared epoxy anticorrosive coating is tougher and has good adhesion and good resistance to water, oil, humidity and heat, and salt fog.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] Parts not mentioned herein are all the same as the prior art or can be implemented with the prior art. Provided below are preferred embodiments of the present invention, but the present invention is not limited to the embodiments below, and slight improvements to the embodiments will also be deemed to be within the protection scope of the present invention.

[0014] Example 1

[0015] Step 1: 146 g of methyl eleostearate, 51.7 g of phenol and 0.438 g of p-toluenesulfonic acid were added into a 500 mL four-necked round-bottom flask; in a state of continuously introducing nitrogen, the mixture was stirred and heated to 90-120°C, and continuously reacted for 2-3 hours at the temperature; the reaction was naturally cooled to room temperature, washed by adding 5 wt.% of an aqueous solution of NaOH and a saturated saline solution sequentially, and allowed to stand and layered for 3 times; and an upper brown viscous liquid was dried with anhydrous sodium sulfate to obtain 189.3 g of a methyl eleostearate-phenol adduct.

[0016] Step 2: 154.4 g of the methyl eleostearate-phenol adduct and 46.4 g of hexamethylenediamine were added into a 500 mL three-necked round-bottom flask, and mixed and stirred uniformly; then, 32.4 g of 37 wt.% of an aqueous solution of formaldehyde was dropwise added while the temperature was controlled at or below 60°C; after the dropwise addition was completed, the mixture was heated to 85-95°C and reacted for 3-4 hours; and then reduced-pressure distillation was performed to remove the generated water to obtain 203.2 g of a tung oil-based Mannich base curing agent. 5 [0017] Step 3: In a stirring state, 51.04 g of hexamethylenediamine was further dropwise added into the three-necked round-bottom flask in Step 2; the mixture was heated to 135-145°C, refluxed and held for 1-2 hours, then heated to 180-190°C for an amidation reaction and held for 1-2 hours, and finally, held for 1-1.5 hours at 0.67-1.33 kPa; and when no water or free amine was distilled out, the heating was stopped, and the remainder was cooled to room temperature to obtain 235.2 g of a dark brown viscous tung oil-based modified amine curing agent.

[0018] Example 2

[0019] Step 1: 146 g of methyl eleostearate, 59.4 g of cresol and 0.438 g of H3PO4 were added into a 500 mL four-necked round-bottom flask; in a state of continuously introducing nitrogen, the mixture was stirred and heated to 90-120°C, and continuously reacted for 2-3 hours at the temperature; the reaction was naturally cooled to room temperature, washed by adding 5 wt.% of an aqueous solution of NaOH and a saturated saline solution sequentially, and allowed to stand and layered for 3 times; and an upper brown viscous liquid was dried with anhydrous sodium sulfate to obtain 197.6 g of a methyl eleostearate-cresol adduct.

[0020] Step 2: 160.0 g of the methyl eleostearate-cresol adduct and 41.2 g of diethylenetriamine were added into a 500 mL three-necked round-bottom flask, and mixed and stirred uniformly; then, 28.8 g of n-butylaldehyde was dropwise added while the temperature was controlled at or below 60°C; after the dropwise addition was completed, the mixture was heated to 85-95°C and reacted for 3-4 hours; and then reduced-pressure distillation was performed to remove the generated water to obtain 219.3 g of a tung oil-based Mannich base curing agent.

[0021] Step 3: In a stirring state, 59.84 g of m-xylylenediamine was further dropwise added into the three-necked round-bottom flask in Step 2; the mixture was heated to 135-145°C, refluxed and held for 1-2 hours, then heated to 180-190°C for an amidation reaction and held for 1-2 hours, and finally, held for 1-1.5 hours at 0.67-1.33 kPa; and when no water or free amine was distilled out, the heating was stopped, and the remainder was cooled to room temperature to obtain 261.2 gofa dark brown viscous tung oil-based modified amine curing agent.

[0022] Example 3

[0023] Step 1: 146 g of methyl eleostearate, 82.5 g of p-tert-butylphenol and 0.438 g of AlCl; were added into a 500 mL four-necked round-bottom flask; in a state of continuously introducing nitrogen, the mixture was stirred and heated to 90-120°C, and continuously reacted for 2-3 hours at the temperature; the reaction was naturally cooled to room temperature, washed by adding 5 wt. % of an aqueous solution of NaOH and a saturated saline solution sequentially, and allowed to stand and layered for 3 times; and an upper brown viscous liquid was dried with anhydrous sodium sulfate to obtain 217.6 g of a methyl eleostearate-p-tert-butylphenol adduct.

[0024] Step 2: 176.8 g of the methyl eleostearate-p-tert-butylphenol adduct and 58.4 g of triethylenetetramine were added into a 500 mL three-necked round-bottom flask, and mixed and stirred uniformly; then, 28.8 g of isobutyraldehyde was dropwise added while the temperature was controlled at or below 60°C; after the dropwise addition was completed, the mixture was heated to 85-95°C and reacted for 3-4 hours; and then reduced-pressure distillation was performed to remove the generated water to obtain 250.2 g of a tung oil-based Mannich base curing agent.

[0025] Step 3: In a stirring state, 59.84 g of m-xylylenediamine was further dropwise added into the three-necked round-bottom flask in Step 2; the mixture was heated to 135-145°C, refluxed and held for 1-2 hours, then heated to 180-190°C for an amidation reaction and held for 1-2 hours, and finally, held for 1-1.5 hours at 0.67-1.33 kPa; and when no water or free amine was distilled out, the heating was stopped, and the remainder was cooled to room temperature to obtain 261.2 g ofa dark brown viscous tung oil-based modified amine curing agent.

[0026] Example 4

[0027] Step 1: 146 g of methyl eleostearate, 125.4 g of bisphenol A and 0.438 g of AICl3 were added into a 500 mL four-necked round-bottom flask; in a state of continuously introducing nitrogen, the mixture was stirred and heated to 90-120°C, and continuously reacted for 2-3 hours at the temperature; the reaction was naturally cooled to room temperature, washed by adding 5 wt.% of an aqueous solution of NaOH and a saturated saline solution sequentially, and allowed to stand and layered for 3 times; and an upper brown viscous liquid was dried with anhydrous sodium sulfate to obtain 252.6 g of a methyl eleostearate-bisphenol A adduct.

[0028] Step 2: 208 g of the methyl eleostearate-bisphenol A adduct and 75.6 g of tetraethylenepentamine were added into a 500 mL three-necked round-bottom flask, and mixed and stirred uniformly; then, 38.4 g of furfural was dropwise added while the temperature was controlled at or below 60°C; after the dropwise addition was completed, the mixture was heated to 85-95°C and reacted for 3-4 hours; and then reduced-pressure distillation was performed to remove the generated water to obtain 306.8 g of a tung oil-based Mannich base curing agent.

[0029] Step 3: In a stirring state, 62.48 g of 1,3-cyclohexanedimethanamine was further dropwise added into the three-necked round-bottom flask in Step 2; the mixture was heated to 135-145°C, refluxed and held for 1-2 hours, then heated to 180-190°C for an amidation reaction and held for 1-2 hours, and finally, held for 1-1.5 hours at 0.67-1.33 kPa; and when no water or free amine was distilled out, the heating was stopped, and the remainder was cooled to room temperature to obtain 352.8 g of a dark brown viscous tung oil-based modified amine curing agent.

[0030] Example 5

[0031] Step 1: 146 g of methyl eleostearate, 51.7 g of phenol and 0.438 g of p-toluenesulfonic acid were added into a 500 mL four-necked round-bottom flask; in a state of continuously introducing nitrogen, the mixture was stirred and heated to 90-120°C, and continuously reacted for 2-3 hours at the temperature; the reaction was naturally cooled to room temperature, washed by adding 5 wt.% of an aqueous solution of NaOH and a saturated saline solution sequentially, and allowed to stand and layered for 3 times; and an upper brown viscous liquid was dried with anhydrous sodium sulfate to obtain 189.3 g of a methyl eleostearate-phenol adduct.

[0032] Step 2: 1544 g of the methyl eleostearate-phenol adduct and 75.6 g of tetraethylenepentamine were added into a 500 mL three-necked round-bottom flask, and mixed and stirred uniformly; then, 42.4 g of benzaldehyde was dropwise added while the temperature was controlled at or below 60°C; after the dropwise addition was completed, the mixture was heated to 85-95°C and reacted for 3-4 hours; and then reduced-pressure distillation was performed to remove the generated water to obtain 261.3 g of a tung oil-based Mannich base curing agent.

[0033] Step 3: In a stirring state, 92.4 g of 4,4-diaminodicyclohexyl methane was further dropwise added into the three-necked round-bottom flask in Step 2; the mixture was heated to 135-145°C, refluxed and held for 1-2 hours, then heated to 180-190°C for an amidation reaction and held for 1-2 hours, and finally, held for 1-1.5 hours at 0.67-1.33 kPa; and when no water or free amine was distilled out, the heating was stopped, and the remainder was cooled to room temperature to obtain 330.2 g of a dark brown viscous tung oil-based modified amine curing agent.

[0034] Example 6

[0035] Step 1: 146 g of methyl eleostearate and 94.5 g of maleimide phenol were added into a 500 mL four-necked round-bottom flask; in a state of continuously introducing nitrogen, the mixture was stirred and heated to 150-160°C, and continuously reacted for 2-3 hours at the temperature; the reaction was naturally cooled to room temperature, washed by adding 5 wt.% of an agueous solution of NaOH and a saturated saline solution sequentially, and allowed to stand and layered for 3 times; and an upper brown viscous liquid was dried with anhydrous sodium sulfate to obtain 237.9 g of a methyl eleostearate-maleimide phenol adduct.

[0036] Step 2: 192.4 g of the methyl eleostearate-maleimide phenol adduct and 58.4 g of triethylenetetramine were added into a 500 mL three-necked round-bottom flask, and mixed and stirred uniformly; then, 32.4 g of 37 wt.% of an aqueous solution of formaldehyde was dropwise added while the temperature was controlled at or below 60°C; after the dropwise addition was completed, the mixture was heated to 85-95°C and reacted for 3-4 hours; and then reduced-pressure distillation was performed to remove the generated water to obtain 251.8 g of a tung oil-based Mannich base curing agent.

[0037] Step 3: In a stirring state, 62.48 g of 1,3-cyclohexanedimethanamine was further dropwise added into the three-necked round-bottom flask in Step 2; the mixture was heated to 135-145°C, refluxed and held for 1-2 hours, then heated to 180-190°C for an amidation reaction and held for 1-2 hours, and finally, held for 1-1.5 hours at 0.67-1.33 kPa; and when no water or free amine was distilled out, the heating was stopped, and the remainder was cooled to room temperature to obtain 296.1 g of a dark brown viscous tung oil-based modified amine curing agent.

[0038] Example 7

[0039] Step 1: 146 g of methyl eleostearate, 51.7 g of phenol and 0.438 g of p-toluenesuifonic acid were added into a 500 mL four-necked round-bottom flask; in a state of continuously introducing nitrogen, the mixture was stirred and heated to 90-120°C, and continuously reacted for 2-3 hours at the temperature; the reaction was naturally cooled to room temperature, washed by adding 5 wt.% of an aqueous solution of NaOH and a saturated saline solution sequentially, and allowed to stand and layered for 3 times; and an upper brown viscous liquid was dried with anhydrous sodium sulfate to obtain 189.3 g of a methyl eleostearate-phenol adduct.

[0040] Step 2: 154.4 g of the methyl eleostearate-phenol adduct and 54.4 g of m-xylylenediamine were added into a 500 mL three-necked round-bottom flask, and mixed and stirred uniformly; then, 42.4 g of benzaldehyde was dropwise added while the temperature was controlled at or below 60°C; after the dropwise addition was completed, the mixture was heated to 85-95°C and reacted for 3-4 hours; and then reduced-pressure distillation was performed to remove the generated water to obtain 240.2 g of a tung oil-based Mannich base curing agent.

[0041] Step 3: In a stirring state, 83.16 g of tetraethylenepentamine was further dropwise added into the three-necked round-bottom flask in Step 2; the mixture was heated to 135-145°C, refluxed and held for 1-2 hours, then heated to 180-190°C for an amidation reaction and held for 1-2 hours, and finally, held for 1-1.5 hours at 0.67-1.33 kPa; and when no water or free amine was distilled out, the heating was stopped, and the remainder was cooled to room temperature to obtain 301.2 g of a dark brown viscous tung oil-based modified amine curing agent.

[0042] Example 8

[0043] Preparation of a resin A component: 50 parts of epoxy resin E51, 27.4 parts of epoxy resin E20, 15 parts of epoxy modified carboxyl-terminated nitrile butadiene rubber, 5 parts of epoxy diluent AGE, 2 parts of a coupling agent KH560, 0.2 part of a leveling agent AFCONA3034, 0.2 part of an antifoaming agent BYK530, 0.2 part of a wetting dispersant BYK903 and an appropriate amount of talc powder, mica powder and zinc phosphate were added into a plastic tank, and dispersed at a high speed until the system was uniform.

[0044] Example 9

[0045] The tung oil-based modified amine curing agent obtained in Example 1 and the resin

A component were weighed in an equivalence ratio and mixed and stirred uniformly; and the mixture was applied to a tinplate sheet with a film applicator, where the film thickness was 50 um, and the curing conditions were: room temperature/24 h + 80°C/3 h.

[0046] The test results are shown in Table 1 and Table 2.

[0047] Example 10

[0048] The tung oil-based modified amine curing agent obtained in Example 6 and the resin

A component were weighed in an equivalence ratio and mixed and stirred uniformly; and the mixture was applied to a tinplate sheet with a film applicator, where the film thickness was 50 um,

and the curing conditions were: room temperature/24 h + 80°C/3 h.

[0049] The test results are shown in Table 1 and Table 2.

[0050] Comparative example 1

[0051] A cardanol-Mannich amide curing agent and the resin A component were weighed in an equivalence ratio and mixed and stirred uniformly; and the mixture was applied to a tinplate sheet with a film applicator, where the film thickness was 50 um, and the curing conditions were: room temperature/24 h + 80°C/3 h.

[0052] The test results are shown in table 1 and table 2.

[0053] Table 1 Comparison of Mechanical Properties of Films of Examples and Comparative

Example

[0054]

TT Comparative example 1 Example 9 Example 10

Adhesion/MPa 22-25 21-25 21-25

Gloss (varnish) Excellent Excellent

Impact flexibility/em | 70 | 8 | 74

Flexibility/cm

Pencil hardness/H

Low-temperature The film has tiny cracks | The film has no cracks |The film has no cracks flexibility (-55+2°C, 2 h) and does not fall off. and does not fall off. | and does not fall off.

Resistance to heat The film has tiny cracks | The film has no cracks |The film has no cracks {15043 °C, 4 h) and does not fall off. and does not fall off. | and does not fall off.

Impact resistance/cm

[0055] Table 2 Comparison of Corrosion Resistance of Films of Examples and Comparative

Example

[0056]

Comparative example 1 Example 9 Example 10

Resistance to jet fuel {168 5 4 h} hardness/H

Resistance to humidity and heat (47+1°C) No rust, no bubble and |No rust, no bubble and|No rust, no bubble and

Relative humidity no color change no color change no color change (9612%), 1,000 h

Resistance to salt fog No rust, no bubble and [No rust, no bubble and|No rust, no bubble and 1,500 h no color change no color change no color change

Resistance to salt fog Unilateral maximum 3 | Unilateral maximum 3 | Unilateral maximum 3 1,500 h cross corrosion | mm, bilateral maximum mm, bilateral mm, bilateral width 5mm maximum 5 mm maximum 5 mm esl ance ose The film blisters slightly | The film does not The film does not ubricat ) “7 7 | and does not fall off. blister or fall off. blister or fall off. h ratte ot (6623 °C 34 The film blisters slightly | The film does not The film does not varauic h = and does not fall off. | blister or fall off blister or fall off.

Resistance to butanone |The coating does not fall| The coating does not | The coating does not wiping off. fall off. fall off.

Resistance to water {deionized water, 7 days, 4 5 5 hardness)/H

Claims

CONCLUSIONS

A method for preparing a modified amine curing agent based on tung oil, comprising the following steps and in the following proportions: step 1: 0.5 mol methyl eleostearate, 0.51-0.55 mol phenol and 0.3-0 .4 wt% of a catalyst based on the methyl eleostarate are added into a reaction vessel; in a state of continuous nitrogen supply, the mixture is stirred and heated to 90-120°C, and reacts continuously at that temperature for two to three hours; the reaction is naturally cooled to room temperature, washed by adding sequentially 5 wt% of an aqueous solution of NaOH and a saturated saline solution, and allowed to stand three times so that it can be layered; and an upper brown viscous liquid is obtained and dried with anhydrous sodium sulfate to obtain a tung oil-derived phenol adduct; step 2: 0.4-0.5 mol of the tung oil-derived phenol adduct and 0.4-0.5 mol of polyamine are added into a reaction vessel, mixing and stirring uniformly; 0.4-0.5 mol of an aldehyde is added dropwise while maintaining the temperature at or below 60°C; after the dropwise addition is complete, the mixture is heated to 85-95°C and allowed to react for three to four hours; and then it is distilled under reduced pressure to remove the generated water, to obtain a Mannich-based tung oil hardening agent; and step 3: while stirring, 0.44-0.55 mol of polyamine is further added dropwise to the tung oil-based Mannich-based hardener; the mixture is heated to 135-145°C, refluxed and held for one to two hours, then heated to 180-190°C for an amidation reaction and held for one to two hours, and finally at 0.67-1.0 to one and a half hours held at 1.33 kPa; and when no more water or free amine is distilled, the heating is discontinued and the residue cooled to room temperature to yield a dark brown viscous tung oil based modified amine curing agent.

The method for preparing a tung oil-based modified amine curing agent according to claim 1, wherein in step 1, the phenol is selected from phenol, cresol, p-tert-butylphenol, bisphenol A and maleimidephenol.

The method for preparing a tung oil-based modified amine curing agent according to claim 1, wherein in step 1 the catalyst is selected from AlCl 5 , p-toluene sulfonic acid and H 3 POa.

The method for preparing a tung oil-based modified amine curing agent according to claim 1, wherein in step 2, the polyamine is at least one selected from hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, m-xylylenediamine and 1,3-cyclohexyldimethylamine.

5. Method for preparing a tung oil-based modified amine curing agent! according to claim 1, wherein in step 2 the aldehyde is at least one selected from formaldehyde, n-butylaldehyde, iso-butyraldehyde, furfural and benzaldehyde.

6. Method for preparing a tung oil-based modified amine curing agent! according to claim 1, wherein in step 3 the polyamine is at least one selected from hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, mexylylenediamine, 4,4'-diaminodicyclohexylimethane and 1,3-cyclohexyldimethylamine.

A tung oil based modified amine curing agent prepared by the method of any one of claims 1 to 6.

Use of the tung oil based modified amine curing agent of claim 7 in preparing an epoxy anticorrosive coating.