A kind of preparation method of modified cardanol aldehyde amine curing agent

Abstract

The invention discloses a preparation method of a modified cardanol phenol aldehyde amine curing agent, and relates to the technical field of epoxy curing agents. The invention comprises mixing bisphenol formed by the reaction of cardanol and phenol with sodium lignin sulfonate intercalated magnesium aluminum hydrotalcite, and reacting with polyamine and aldehyde compounds to obtain a modified cardanol phenol aldehyde amine curing agent, which can effectively improve the high and low temperature resistance, weather resistance and corrosion resistance of the curing agent, and is conducive to expanding the application scope of the cardanol phenol aldehyde amine curing agent in the field of epoxy coatings.

Description

Technical Field

[0001] The invention relates to the technical field of epoxy curing agents, and in particular to a method for preparing a modified cardanol aldehyde amine curing agent. Background Art

[0002] Epoxy coatings are coatings with epoxy resin as the main film-forming substance. They have excellent adhesion, wear resistance and corrosion resistance and are widely used in different fields such as construction, petrochemicals, ships, and wind power. Epoxy curing agents have the function of promoting cross-linking reactions between epoxy resin molecules to form a three-dimensional network structure and thus solidify, which has a key influence on the performance of epoxy coatings. Phenolic amine curing agents have the characteristics of low toxicity and low volatility and have been widely used in the field of epoxy coatings. However, epoxy coatings using phenolic amine curing agents often have the problem of poor toughness. Cardanol is a natural phenolic compound with an unsaturated C15 long side chain. It is an extract of cashew nut shell oil and belongs to a green renewable resource. The presence of fatty chains in the cardanol molecule gives it good flexibility. The cardanol amine curing agent synthesized with cardanol as a raw material can effectively improve the toughness of epoxy coatings. However, the cardanol amine curing agent has the problems of insufficient high and low temperature resistance and weather resistance, and its corrosion resistance is not ideal, and it is difficult to meet the use requirements in some high-standard applications. Summary of the invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a preparation method of a modified cashew phenol aldehyde amine curing agent.

[0004] The invention provides a preparation method of a modified cashew phenol aldehyde amine curing agent, comprising the following steps: mixing cashew phenol and phenol, keeping warm at 40-50 DEG C and stirring evenly, then adding an appropriate amount of acidic catalyst, keeping warm at 85-95 DEG C in a nitrogen atmosphere for reaction, cooling to 50-70 DEG C after the reaction, adding sodium lignin sulfonate intercalated magnesium aluminum hydrotalcite, dispersing evenly, adding polyamine, fully mixing, then adding aldehyde compounds, keeping warm at 70-90 DEG C for reaction, and removing water by reduced pressure distillation after the reaction to obtain the modified cashew phenol aldehyde amine curing agent; wherein the molar ratio of cashew phenol to phenol is 1:1-3, the ratio of the molar sum of cashew phenol and phenol to the molar sum of polyamine and aldehyde compounds is 1:1.5-2.5:1-2, and the mass of the sodium lignin sulfonate intercalated magnesium aluminum hydrotalcite is 2-5% of the mass sum of cashew phenol and phenol.

[0005] Preferably, the acidic catalyst is p-toluenesulfonic acid; and the ratio of the sum of the molar amounts of cardanol and phenol to the molar amount of the acidic catalyst is 1:0.01-0.05.

[0006] Preferably, in the preparation method of the modified cashew phenol aldehyde amine curing agent, the reaction is carried out at 85-95° C. under a nitrogen atmosphere for 1-3 hours.

[0007] Preferably, the preparation method of the sodium lignin sulfonate intercalated magnesium aluminum hydrotalcite comprises: adding nano magnesium aluminum hydrotalcite to a mixed solution of deionized water and anhydrous ethanol, stirring at 70-90°C for 1-3h, then adding sodium lignin sulfonate, adjusting the pH to 2-4, stirring at 70-90°C for 2-5h, then filtering, and drying to obtain the obtained product; the mass ratio of the nano magnesium aluminum hydrotalcite to the sodium lignin sulfonate is 1:0.1-0.2; the volume ratio of the deionized water to the anhydrous ethanol is 1:1-3.

[0008] Preferably, the particle size of the nano magnesium aluminum hydrotalcite is 50-500 nm.

[0009] In the present invention, the preparation method of the nano-magnesium aluminum hydrotalcite is not particularly limited, and a conventional preparation method can be used.

[0010] Preferably, in the preparation method of the modified cashew phenol aldehyde amine curing agent, the reaction is kept at 70-90° C. for 4-6 hours.

[0011] Preferably, the polyamine is at least one of ethylenediamine, diethylenetriamine and triethylenetetramine.

[0012] Preferably, the aldehyde compound is formaldehyde or paraformaldehyde.

[0013] A modified cardanol aldehyde amine curing agent is prepared by the preparation method.

[0014] The beneficial effects of the present invention are as follows:

[0015] The invention mixes bisphenol formed by the reaction of cardanol and phenol with an appropriate amount of sodium lignin sulfonate intercalated magnesium aluminum hydrotalcite, and then performs Mannich reaction with polyamine and aldehyde compounds to obtain a modified cardanol aldehyde amine curing agent, wherein the bisphenol obtained by the reaction of cardanol and phenol has good mechanical properties and thermal stability, and the surface of the magnesium aluminum hydrotalcite after sodium lignin sulfonate intercalation has a phenolic structure, which has high compatibility with phenols and can participate in the reaction with polyamine and aldehydes, so that the magnesium aluminum hydrotalcite with a nano-sized lamellar structure is introduced into the curing agent, which can effectively prevent the penetration of corrosive media, thereby improving corrosion resistance, and at the same time, the nano-sized lamellar structure has a limiting effect on the activity of the cardanol molecular chain, can reduce the thermal decomposition of the cardanol molecular chain, further improves the thermal stability of the cardanol aldehyde amine curing agent, and improves its cold and hot cycle resistance and weather resistance. In summary, the high and low temperature resistance, weather resistance and corrosion resistance of the modified cashew phenol aldehyde amine curing agent of the present invention have been significantly improved, and it has excellent adhesion and mechanical properties, which is conducive to expanding the application scope of cashew phenol aldehyde amine curing agent in the field of epoxy coatings. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is described in detail below through specific embodiments.

[0017] In the following examples and comparative examples:

[0018] The preparation method of nano magnesium aluminum hydrotalcite is:

[0019] (1) Prepare solution A: weigh 81.33 g MgSO4·7H2O and 41.55 g Al(NO3)3·9H2O into a beaker, add a small amount of water and stir thoroughly to dissolve, transfer to a 250 mL volumetric flask, dilute to volume and shake well, and set aside; (2) Prepare solution B (pH buffer): weigh approximately 35.44 g NaOH and 5.87 g anhydrous Na2CO3, respectively, place in a beaker, add a small amount of water and stir thoroughly to dissolve, transfer to a 250 mL volumetric flask, dilute to volume and shake well, Set aside; (3) Take two constant pressure dropping funnels and inject solution A and solution B respectively for set aside; (4) Add 200 mL of distilled water to a 1L three-necked flask, control the water temperature at 60°C, stir vigorously, and simultaneously add solution A and solution B to the flask dropwise. The addition is completed within 30 minutes. During the addition, the pH value of the solution in the flask is maintained at 11-12. Stirring is continued for 30 minutes. Then the temperature of the solution in the flask is raised to 80°C and kept warm for 8-18 hours. Cool to room temperature, repeatedly filter and wash the precipitate until it is neutral. The product is dried at 100°C for 12 hours to obtain nano-magnesium aluminum hydrotalcite with a particle size of 50-70 nm. Example 1

[0020] Preparation of modified cashew phenol aldehyde amine curing agent: 30.2g of cashew phenol (0.1mol) and 18.8g of phenol (0.2mol) were mixed, stirred evenly at 45°C, and then 0.86g of p-toluenesulfonic acid (0.005mol) was added, and the mixture was kept warm at 90°C for 2h under a nitrogen atmosphere. After the reaction, the mixture was cooled to 60°C, 1.5g of sodium lignin sulfonate intercalated magnesium aluminum hydrotalcite was added, and the mixture was evenly dispersed. Then 61.8g of diethylenetriamine (0.6mol) was added, and the mixture was fully mixed. Then, a formaldehyde aqueous solution with a mass concentration of 37% (containing 13.5g of formaldehyde, 0.45mol) was added, and the mixture was kept warm at 80°C for 5h. After the reaction, the water was removed by reduced pressure distillation to obtain the modified cashew phenol aldehyde amine curing agent.

[0021] The preparation method of sodium lignin sulfonate intercalated magnesium aluminum hydrotalcite is as follows: after 300 mL of deionized water and 600 mL of anhydrous ethanol are evenly mixed, 10 g of nano magnesium aluminum hydrotalcite is added to the obtained mixed solution, stirred at 80°C for 2 h, and then 1.5 g of sodium lignin sulfonate is added, the pH is adjusted to 3 with HCl, stirred at 80°C for 3 h, and then filtered and dried to obtain the obtained product. Example 2

[0022] Preparation of modified cashew phenol aldehyde amine curing agent: 30.2g of cashew phenol (0.1mol) and 9.4g of phenol (0.1mol) were mixed, stirred evenly at 40°C, and then 0.344g of p-toluenesulfonic acid (0.002mol) was added, and the mixture was kept warm at 85°C for 3h under a nitrogen atmosphere. After the reaction, the mixture was cooled to 50°C, 0.8g of sodium lignin sulfonate intercalated magnesium aluminum hydrotalcite was added, and the mixture was evenly dispersed. Then 43.8g of triethylenetetramine (0.3mol) was added, and the mixture was fully mixed. Then, a formaldehyde aqueous solution with a mass concentration of 37% (containing 6g of formaldehyde, 0.2mol) was added, and the mixture was kept warm at 70°C for 6h. After the reaction, the water was removed by reduced pressure distillation to obtain the modified cashew phenol aldehyde amine curing agent.

[0023] The preparation method of sodium lignin sulfonate intercalated magnesium aluminum hydrotalcite is as follows: after 300 mL of deionized water and 600 mL of anhydrous ethanol are evenly mixed, 10 g of nano magnesium aluminum hydrotalcite is added to the obtained mixed solution, stirred at 70°C for 3 h, and then 1 g of sodium lignin sulfonate is added, the pH is adjusted to 3 with HCl, stirred at 70°C for 5 h, and then filtered and dried to obtain the obtained product. Example 3

[0024] Preparation of modified cashew phenol aldehyde amine curing agent: 30.2g of cashew phenol (0.1mol) and 28.2g of phenol (0.3mol) were mixed, stirred evenly at 50°C, and then 3.44g of p-toluenesulfonic acid (0.02mol) was added, and the mixture was kept warm at 95°C for 1h under a nitrogen atmosphere. After the reaction, the mixture was cooled to 70°C, 2.9g of sodium lignin sulfonate intercalated magnesium aluminum hydrotalcite was added, and the mixture was evenly dispersed. Then 146g of triethylenetetramine (1mol) was added, and the mixture was fully mixed. Then, a formaldehyde aqueous solution with a mass concentration of 37% (containing 24g of formaldehyde, 0.8mol) was added, and the mixture was kept warm at 90°C for 4h. After the reaction, the water was removed by reduced pressure distillation to obtain the modified cashew phenol aldehyde amine curing agent.

[0025] The preparation method of sodium lignin sulfonate intercalated magnesium aluminum hydrotalcite is as follows: after 300 mL of deionized water and 600 mL of anhydrous ethanol are evenly mixed, 10 g of nano magnesium aluminum hydrotalcite is added to the obtained mixed solution, stirred at 90°C for 1 hour, and then 2 g of sodium lignin sulfonate is added, the pH is adjusted to 4 with glacial acetic acid, stirred at 90°C for 2 hours, and then filtered and dried to obtain the product.

[0026] Comparative Example 1

[0027] Preparation of modified cashew phenol aldehyde amine curing agent: 30.2g of cashew phenol (0.1mol) and 18.8g of phenol (0.2mol) were mixed, and the mixture was kept warm at 45°C and stirred evenly. Then, 0.86g of p-toluenesulfonic acid (0.005mol) was added, and the mixture was kept warm at 90°C for 2h under a nitrogen atmosphere. After the reaction, the mixture was cooled to 60°C, 61.8g of diethylenetriamine (0.6mol) was added, and the mixture was fully mixed. Then, a formaldehyde aqueous solution with a mass concentration of 37% (containing 13.5g of formaldehyde, 0.45mol) was added, and the mixture was kept warm at 80°C for 5h. After the reaction, the water was removed by reduced pressure distillation to obtain the modified cashew phenol aldehyde amine curing agent.

[0028] Comparative Example 2

[0029] Preparation of modified cashew phenol aldehyde amine curing agent: 30.2g of cashew phenol (0.1mol) and 18.8g of phenol (0.2mol) were mixed, and the mixture was kept warm at 45°C and stirred evenly. Then, 0.86g of p-toluenesulfonic acid (0.005mol) was added, and the mixture was kept warm at 90°C for 2h under a nitrogen atmosphere. After the reaction, the mixture was cooled to 60°C, 1.5g of magnesium aluminum hydrotalcite was added, and the mixture was dispersed evenly. Then, 61.8g of diethylenetriamine (0.6mol) was added, and the mixture was fully mixed. Then, a formaldehyde aqueous solution with a mass concentration of 37% (containing 13.5g of formaldehyde, 0.45mol) was added, and the mixture was kept warm at 80°C for 5h. After the reaction, the water was removed by reduced pressure distillation to obtain the modified cashew phenol aldehyde amine curing agent.

[0030] Comparative Example 3

[0031] Preparation of modified cashew phenol aldehyde amine curing agent: 30.2g of cashew phenol (0.1mol) and 18.8g of phenol (0.2mol) were mixed, and the mixture was kept warm at 45°C and stirred evenly. Then, 0.86g of p-toluenesulfonic acid (0.005mol) was added, and the mixture was kept warm at 90°C for 2h under a nitrogen atmosphere. After the reaction, the mixture was cooled to 60°C, 1.5g of sodium lignin sulfonate was added, and the mixture was dispersed evenly. Then, 61.8g of diethylenetriamine (0.6mol) was added, and the mixture was fully mixed. Then, a formaldehyde aqueous solution with a mass concentration of 37% (containing 13.5g of formaldehyde, 0.45mol) was added, and the mixture was kept warm at 80°C for 5h. After the reaction, the water was removed by reduced pressure distillation to obtain the modified cashew phenol aldehyde amine curing agent.

[0032] Test example

[0033] The epoxy resin E51 was mixed with the curing agents prepared in Example 1 and Comparative Examples 1 to 3 at a mass ratio of 100:30 to prepare epoxy coatings, and the obtained epoxy coatings were coated on the surface of the metal plate and cured at 25° C. to form a coating with a thickness of 35 to 40 μm. The coating properties were tested, and the test results are shown in Table 1:

[0034] Table 1

[0035]

[0036] Note: The test method for the resistance to cold and hot cycles is as follows: place the sample in a high and low temperature cycle test chamber at a temperature of 80°C and a relative humidity of 95%. After storing it for 4 hours at a temperature of 80°C and a relative humidity of 95%, first cool it down to -40°C at a rate of 1°C / min and keep it at a relative humidity of 95% for 4 hours, then heat it up to 80°C at a rate of 1°C / min and keep it at a relative humidity of 95% for 4 hours. This is one cycle. The paint film is qualified if it does not change color, bubble or crack.

[0037] It can be seen from the test results in Table 1 that the modified cardanolamine curing agent of Example 1 is compared with the phenolamine curing agent in Comparative Example 1 using phenol and cardanol synthesized bisphenol as raw materials. By adding an appropriate amount of sodium lignin sulfonate intercalated magnesium aluminum hydrotalcite, the corrosion resistance and weather resistance of the curing agent are significantly improved. This is because the surface of the magnesium aluminum hydrotalcite after sodium lignin sulfonate intercalation has a phenolic structure, which has high compatibility with phenols, and it can participate in the reaction with polyamines and aldehydes, so that the magnesium aluminum hydrotalcite with a nano-sized lamellar structure is introduced into the curing agent, which can effectively prevent the penetration of corrosive media, thereby improving the corrosion resistance. This nano-sized lamellar structure has a restrictive effect on the activity of the cardanol molecular chain, which can reduce the thermal decomposition of the cardanol molecular chain, thereby improving the thermal stability of the cardanol aldehyde amine curing agent and improving its resistance to cold and hot cycles and weather resistance; while in Comparative Example 2, only sodium lignin sulfonate was added, which did not significantly improve the corrosion resistance and weather resistance; in Comparative Example 3, only nano-magnesium-aluminum hydrotalcite was added, and since the direct addition of nano-magnesium-aluminum hydrotalcite was not compatible enough with other raw materials in the reaction system, the reaction effect and the dispersion uniformity of the reaction system were affected, resulting in its improvement effect on corrosion resistance and weather resistance being less than ideal compared with Example 1.

[0038] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a modified cardanol aldehyde amine curing agent, characterized in that: The following steps are involved: After mixing cardanol and phenol, keep them warm at 40-50°C and stir them uniformly, then add an appropriate amount of acidic catalyst, keep them warm at 85-95°C in a nitrogen atmosphere for reaction, cool to 50-70°C after the reaction, add sodium lignin sulfonate intercalated magnesium aluminum hydrotalcite, disperse them uniformly, add polyamine, mix them thoroughly, then add aldehyde compounds, keep them warm at 70-90°C for reaction, and remove water by reduced pressure distillation after the reaction to obtain; wherein the molar ratio of cardanol to phenol is 1:1-3, the ratio of the sum of the molar amounts of cardanol and phenol to the molar amounts of the polyamine and aldehyde compounds is 1:1.5-2.5:1-2, and the mass of the sodium lignin sulfonate intercalated magnesium aluminum hydrotalcite is 2-5% of the sum of the mass of cardanol and phenol.

2. The preparation method of the modified cardanol aldehyde amine curing agent according to claim 1, characterized in that, The acidic catalyst is p-toluenesulfonic acid; the ratio of the sum of the molar amounts of cardanol and phenol to the molar amount of the acidic catalyst is 1:0.01-0.

05.

3. The preparation method of the modified cardanol aldehyde amine curing agent according to claim 1, characterized in that, In a nitrogen atmosphere, the reaction was kept at 85-95°C for 1-3 hours.

4. The preparation method of the modified cardanol aldehyde amine curing agent according to claim 1, characterized in that, The preparation method of the sodium lignin sulfonate intercalated magnesium aluminum hydrotalcite comprises: adding nano magnesium aluminum hydrotalcite to a mixed solution of deionized water and anhydrous ethanol, stirring at 70-90°C for 1-3 hours, then adding sodium lignin sulfonate, adjusting the pH to 2-4, stirring at 70-90°C for 2-5 hours, then filtering, and drying to obtain the obtained product; the mass ratio of the nano magnesium aluminum hydrotalcite to the sodium lignin sulfonate is 1:0.1-0.2; and the volume ratio of the deionized water to the anhydrous ethanol is 1:1-3.

5. The preparation method of the modified cardanol aldehyde amine curing agent according to claim 4, characterized in that, The particle size of the nano magnesium aluminum hydrotalcite is 50-500 nm.

6. The method for preparing the modified cardanol aldehyde amine curing agent according to claim 1, characterized in that: Keep the reaction at 70-90℃ for 4-6 hours.

7. The method for preparing the modified cardanol aldehyde amine curing agent according to claim 1, characterized in that: The polyamine is at least one of ethylenediamine, diethylenetriamine and triethylenetetramine.

8. The method for preparing the modified cardanol aldehyde amine curing agent according to claim 1, characterized in that: The aldehyde compound is formaldehyde or paraformaldehyde.

9. A modified cardanol aldehyde amine curing agent, characterized in that, Prepared by the preparation method according to any one of claims 1 to 8.

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