A cardanol aldehyde amine epoxy resin curing agent containing a tetrazole structure, and a preparation method and application thereof

Abstract

The present application relates to the technical field of epoxy coating, and particularly relates to a cashew phenolic aldehyde amine epoxy resin curing agent containing a tetrazole structure, a preparation method and application thereof. The cashew phenolic aldehyde amine epoxy resin curing agent containing a tetrazole structure provided by the present application contains primary amine, secondary amine and tertiary amine, which provides sufficient active hydrogen required for curing, further promotes ring-opening reaction, and greatly improves the curing speed; meanwhile, the tetrazole ring structure in the curing agent can improve the hardness of the cured product, and make up for the problem of low hardness caused by the 15-carbon long chain structure in cashew phenol. Therefore, the cashew phenolic aldehyde amine epoxy resin curing agent containing a tetrazole structure provided by the present application has the advantages of fast drying speed after being matched with epoxy resin, actual drying time less than 4h, strong impact resistance, positive and negative impact reaching 100cm, cross-hatch adhesion 0 level, flexibility 1mm, and hardness H level or above.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of epoxy coating, in particular to a cashew phenolic amine epoxy resin curing agent containing a tetrazole structure and a preparation method and application thereof. BACKGROUND

[0002] Cashew phenol is a green and environmentally friendly industrial raw material extracted from natural cashew nut shell oil. The presence of benzene ring structure makes it have excellent high temperature resistance. The C15 long straight chain containing unsaturated double bond between benzene rings can enhance the toughness of the system and provide excellent hydrophobicity and self-drying property. Because of its abundant source, low price, excellent performance and renewability, it has become a research hotspot in recent years.

[0003] Curing agent is one of the indispensable components in the use process of epoxy resin, and plays a very important role in the performance of epoxy resin cured product. Small molecule aliphatic curing agents such as ethylenediamine, diethylenetriamine and triethylenetetramine have the disadvantages of high toxicity, fast curing reaction, violent curing reaction with epoxy resin, short use period, etc., and the curing is limited by temperature and humidity conditions. Therefore, the synthesis of cashew phenolic amine curing agent with macromolecular chain structure and not easy to volatilize has become a market trend. After the cashew phenolic amine curing agent synthesized by Mannich reaction is matched with epoxy resin, it has the advantages of long pot life, low curing shrinkage, low toxicity and excellent mechanical properties. However, due to the small variety and simple structure of the raw material fatty amine in cashew phenolic amine, it gradually cannot meet the market demand for the comprehensive performance of cashew phenolic curing agent (such as excellent mechanical properties, adhesion and corrosion resistance, etc.), so it is imperative to develop a cashew phenolic amine epoxy curing agent with a new structure. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a cashew phenolic amine epoxy resin curing agent containing a tetrazole structure and a preparation method and application thereof. The cashew phenolic amine epoxy resin curing agent containing a tetrazole structure has excellent comprehensive performance (excellent adhesion, impact resistance, hardness and corrosion resistance).

[0005] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0006] The present application provides a cashew phenolic amine epoxy resin curing agent containing a tetrazole structure, which has a structure shown in formula 1 or formula 2:

[0007]

[0008] The present application also provides a preparation method of the cashew phenolic amine epoxy resin curing agent containing a tetrazole structure, which comprises the following steps:

[0009] The cashew phenol and tetrazole-5-acetylhydrazine are mixed in an inert atmosphere, then a formaldehyde monomer providing substance is added, a Mannich reaction and a dehydration reaction are sequentially carried out, then a promoter is added, and thus the cashew phenolic aldehyde amine epoxy resin curing agent with the tetrazole structure is obtained.

[0010] Preferably, the molar ratio of the formaldehyde monomers in the cashew phenol, tetrazole-5-acetylhydrazine and formaldehyde monomer providing substance is (1.0-1.2):(1.1-1.3):(1.4-1.6).

[0011] Preferably, the formaldehyde monomer providing substance comprises paraformaldehyde or a formaldehyde aqueous solution with a mass concentration of 37%.

[0012] Preferably, the mixing temperature is 90-100℃.

[0013] The temperature for adding the formaldehyde monomer providing substance is 75-90℃.

[0014] Preferably, the process of the Mannich reaction is: first reacting at a temperature of 100-105℃ for 1-2h, and then reacting at a temperature of 145-150℃ for 2.5-3.5h.

[0015] Preferably, the dehydration reaction is carried out at a temperature of 100-105℃, a vacuum degree of 2-3kPa and for a time of 40-50min.

[0016] Preferably, the promoter comprises one or two of 2,4,6-tris(dimethylaminomethyl)phenol, triethanolamine and N,N-dimethyl-1,3-propanediamine.

[0017] Preferably, the mass of the promoter is 2-4% of the total mass of the cashew phenol, tetrazole-5-acetylhydrazine and formaldehyde monomer providing substance.

[0018] The application further provides an application of the cashew phenolic aldehyde amine epoxy resin curing agent with the tetrazole structure in the coating field.

[0019] The application provides a cashew phenolic aldehyde amine epoxy resin curing agent with a tetrazole structure, which has a structure shown in Formula 1 or Formula 2.

[0020]

[0021] The tazarine structure-containing cashew phenolic amine epoxy resin curing agent provided by the present application contains primary amine, secondary amine and tertiary amine, which not only provides sufficient active hydrogen required for curing, but also further promotes ring-opening reaction, greatly improving the curing speed; meanwhile, the tazarine ring structure can improve the hardness of the cured product, making up for the low hardness caused by the 15-carbon long chain structure in cashew phenol. Therefore, the tazarine structure-containing cashew phenolic amine epoxy resin curing agent provided by the present application has fast drying speed after being matched with epoxy resin, and the actual drying time is less than 4 hours, and meanwhile, the impact resistance is strong, the positive and negative impact can reach 100 cm, the grid adhesion is 0 level, the flexibility is 1 mm, and the hardness is H level or above. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The infrared spectrum of the tazarine structure-containing cashew phenolic amine epoxy resin curing agent described in Example 1. DETAILED DESCRIPTION

[0023] The present application provides a tazarine structure-containing cashew phenolic amine epoxy resin curing agent, which has a structure shown in Formula 1 or Formula 2:

[0024]

[0025] The present application also provides a preparation method of the tazarine structure-containing cashew phenolic amine epoxy resin curing agent described in the above technical solution, which comprises the following steps:

[0026] In an inert atmosphere, cashew phenol and tazarine-5-acetylhydrazine are mixed, then a substance providing formaldehyde monomer is added, and then Mannich reaction and dehydration reaction are sequentially performed, and then a promoter is added to obtain the tazarine structure-containing cashew phenolic amine epoxy resin curing agent.

[0027] In the present application, all the raw materials for preparation are commercially available products well known to those skilled in the art, unless otherwise specified.

[0028] In the present application, the inert atmosphere is preferably a nitrogen atmosphere.

[0029] In the present application, the purity of the cashew phenol is preferably ≥ 90%.

[0030] In the present application, the molar ratio of the cashew phenol to tazarine-5-acetylhydrazine is preferably (1.0-1.2):(1.1-1.3), and more preferably (1.05-1.15):(1.15-1.25). In the examples of the present application, the molar ratio of the cashew phenol to tazarine-5-acetylhydrazine can be 1:1.1, 1:1.2, 1.2:1.3, 1.15:1.25 or 1.05:1.15.

[0031] In the present application, the temperature of the mixing is preferably 90 to 100°C, more preferably 92 to 98°C. In the embodiments of the present application, the temperature of the mixing can be 90°C, 100°C, 95°C, or 97°C. The present application does not have any particular limitation on the time of the mixing, and a time well known to those skilled in the art can be used as long as complete dissolution is ensured.

[0032] In the present application, the substance providing formaldehyde monomers preferably includes paraformaldehyde or a formaldehyde aqueous solution having a mass concentration of 37%. In the present application, the molar ratio of the cardanol to the formaldehyde monomers in the substance providing formaldehyde monomers is preferably (1.0 to 1.2):(1.4 to 1.6), more preferably (1.05 to 1.15):(1.45 to 1.55). In the embodiments of the present application, the kind of the substance providing formaldehyde monomers can be paraformaldehyde; the molar ratio of the cardanol to the formaldehyde monomers in the substance providing formaldehyde monomers can be 1.1:1.5, 1.2:1.6, 1.15:1.6, or 1.05:1.45.

[0033] In the present application, the temperature of adding the substance providing formaldehyde monomers is preferably 75 to 90°C.

[0034] In the present application, the process of adding the substance providing formaldehyde monomers is preferably batch addition, and the number of the batch addition is preferably 4.

[0035] In the present application, the process of the Mannich reaction is preferably first reacting at a temperature of 100 to 105°C for 1 to 2 h, and then reacting at a temperature of 145 to 150°C for 2.5 to 3.5 h; more preferably first reacting at a temperature of 101 to 103°C for 1 to 2 h, and then reacting at a temperature of 146 to 148°C for 2.8 to 3.2 h. In the embodiments of the present application, the temperature of the first step of the Mannich reaction can be 100°C, 105°C, 103°C, or 105°C, and the time can be 2 h, 1 h, 1.5 h, or 1.8 h; the temperature of the second step of the Mannich reaction can be 145°C, 146°C, 147°C, or 150°C, and the time can be 3 h, 3.5 h, or 2.5 h.

[0036] After the completion of the Mannich reaction, the present application further preferably includes cooling to the temperature of the dehydration reaction, and the present application does not have any particular limitation on the process of the cooling, and a process well known to those skilled in the art can be used as long as the temperature of the dehydration reaction is reached.

[0037] In the present application, the temperature of the dehydration reaction is preferably 100-105℃, more preferably 101-103℃; the vacuum degree is preferably 2-3kPa; and the time is preferably 40-50min, more preferably 43-46min. In the embodiments of the present application, the temperature of the dehydration reaction can be 100℃, 105℃ or 103℃, the vacuum degree can be 2-3kPa, and the time can be 50min, 40min or 45min.

[0038] In the present application, the temperature for adding the accelerator is preferably 65-70℃, more preferably 66-68℃; and the accelerator preferably includes one or two of 2,4,6-tris(dimethylaminomethyl)phenol, triethanolamine and N,N-dimethyl-1,3-propanediamine. When the accelerator is two of the above-mentioned specific choices, the present application does not have any special limitation on the ratio of the above-mentioned specific substances, and the mixing can be performed in any ratio. In the present application, the mass of the accelerator is preferably 2-4% of the total mass of the cardanol, tetrazole-5-acetylhydrazine and the substance providing the formaldehyde monomer. In the embodiments of the present application, the temperature for adding the accelerator can be 70℃, 69℃, 68℃ or 65℃; the type of the accelerator can be 2,4,6-tris(dimethylaminomethyl)phenol, triethanolamine, 2,4,6-tris(dimethylaminomethyl)phenol N,N-dimethyl-1,3-propanediamine with a mass ratio of 1:1, triethanolamine and N,N-dimethyl-1,3-propanediamine with a mass ratio of 1:1, or triethanolamine and 2,4,6-tris(dimethylaminomethyl)phenol with a mass ratio of 1:1; and the mass of the accelerator can be 2%, 2.5%, 3% or 4% of the total mass of the cardanol, tetrazole-5-acetylhydrazine and the substance providing the formaldehyde monomer.

[0039] The present application does not have any special limitation on the adding method of the accelerator, and the accelerator can be added by any adding method known to those skilled in the art.

[0040] After adding the accelerator, the present application further preferably includes stirring, and the temperature of the stirring is preferably 65-70℃ and the time is preferably 1-2h. In the embodiments of the present application, the temperature of the stirring can be 70℃, 69℃, 68℃ or 65℃, and the time can be 1.6h, 1h, 1.5h or 2h.

[0041] The present application further provides the use of the cardanol-aldehyde amine epoxy resin curing agent containing a tetrazole structure according to the above technical solution or the cardanol-aldehyde amine epoxy resin curing agent containing a tetrazole structure prepared by the preparation method according to the above technical solution in the field of coating. In the present application, the field of use is preferably the field of epoxy coating.

[0042] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative effort belong to the scope of the present application.

[0043] Example 1

[0044] Under an inert atmosphere (the type of inert atmosphere is N2), 302 g of cardanol (1 mol) and 156.2 g of tetrazole-5-acetylhydrazine (1.1 mol) were warmed to 90℃ and mixed until completely dissolved, cooled to 75℃, and 42 g of polyformaldehyde (molar amount of formaldehyde monomer: 1.4 mol) was added in batches (in 4 batches) while controlling the temperature at 75-90℃. After warming to 100℃ and reacting for 2 h, the temperature was increased to 145℃ and reacted for 3.5 h. After cooling to 100℃, vacuum dehydration was performed for 50 min after reducing the vacuum degree to 2-3 kPa. After cooling to 65℃, 10 g of accelerator 2,4,6-tris(dimethylaminomethyl)phenol was added, and the mixture was stirred for 2 h to obtain a cardanol-aldehyde amine epoxy resin curing agent containing a tetrazole structure;

[0045] Figure 1 The infrared spectrum of the cardanol-aldehyde amine epoxy resin curing agent containing a tetrazole structure described in Example 1 is shown in Figure 1 It can be seen from the figure that the peak at 3295 cm -1 is the stretching vibration peak of N-H in -NH2 in the raw material amine; the peak at 2927 cm -1 is the stretching vibration peak of -C-H in the alkyl chain at the tail of cardanol; the peaks at 1616 cm -1 and 1581 cm -1 are the absorption peaks of -N=N and -C=N structures in the monomer amine, respectively; the peak at 1456 cm -1 is the out-of-plane bending vibration of -C-H, indicating that the cardanol-aldehyde amine epoxy resin curing agent is successfully synthesized.

[0046] The viscosity test at 25℃ was carried out according to the Adhesive Viscosity Determination GB / T2794-1995, and the test result was: the viscosity was 18600 mPa·s, and the amine value was determined by the perchloric acid method to be 576.4 mg·KOH / g.

[0047] Example 2

[0048] Under inert atmosphere (the type of inert atmosphere is N2), 332.2 g of cardanol (1.1 mol) and 170.4 g of tetrazole-5-acetylhydrazine (1.2 mol) were mixed to complete dissolution at 100 ℃, cooled to 80 ℃, and 45 g of polyformaldehyde (molar amount of formaldehyde monomer: 1.5 mol) was added in batches (in 4 batches) at a temperature of 75-90 ℃. After being heated to 105 ℃ for 1 h and then heated to 150 ℃ for 2.5 h, the temperature was lowered to 105 ℃, and vacuum dehydration was performed at a vacuum degree of 2-3 kPa for 40 min. After being cooled to 70 ℃, 21.9 g of triethanolamine was added, and the mixture was stirred for 1 h to obtain a cardanol aldehyde amine epoxy resin curing agent containing a tetrazole structure;

[0049] The viscosity test at 25 ℃ was performed according to the Adhesive Viscosity Determination GB / T2794-1995, and the test result was that the viscosity was 17900 mPa·s, and the amine value was 570.7 mg·KOH / g determined by the perchloric acid method.

[0050] Example 3

[0051] Under inert atmosphere (the type of inert atmosphere is N2), 332.2 g of cardanol (1.1 mol) and 170.4 g of tetrazole-5-acetylhydrazine (1.2 mol) were mixed to complete dissolution at 100 ℃, cooled to 80 ℃, and 45 g of polyformaldehyde (molar amount of formaldehyde monomer: 1.5 mol) was added in batches (in 4 batches) at a temperature of 75-90 ℃. After being heated to 105 ℃ for 1 h and then heated to 150 ℃ for 2.5 h, the temperature was lowered to 105 ℃, and vacuum dehydration was performed at a vacuum degree of 2-3 kPa for 40 min. After being cooled to 70 ℃, 21.9 g of triethanolamine was added, and the mixture was stirred for 1 h to obtain a cardanol aldehyde amine epoxy resin curing agent containing a tetrazole structure;

[0052] The viscosity test at 25 ℃ was performed according to the Adhesive Viscosity Determination GB / T2794-1995, and the test result was that the viscosity was 17900 mPa·s, and the amine value was 570.7 mg·KOH / g determined by the perchloric acid method.

[0053] Example 4

[0054] Under inert atmosphere (the type of inert atmosphere is N2), 347.3 g of cardanol (1.15 mol) and 177.5 g of tetrazole-5-acetylhydrazine (1.25 mol) were mixed to complete dissolution at 97 ℃, cooled to 77 ℃, and 48 g of polyformaldehyde (molar amount of formaldehyde monomer: 1.6 mol) was added in batches (in 4 batches) at a temperature of 75-90 ℃. After being heated to 105 ℃ for 1.8 h and then heated to 146 ℃ for 3.5 h, the temperature was decreased to 105 ℃, and vacuum dehydration was performed at a vacuum degree of 2-3 kPa for 45 min. After being cooled to 69 ℃, 7.16 g of promoter triethanolamine and 7.16 g of N,N-dimethyl-1,3-propanediamine were added, and stirring and mixing were performed for 1.6 h to obtain a cardanol aldehyde amine epoxy resin curing agent containing a tetrazole structure;

[0055] Viscosity test at 25 ℃ was performed according to “Adhesive Viscosity Determination” GB / T2794-1995, and the test result was that the viscosity was 15500 mPa·s, and the amine value was 577.4 mg·KOH / g determined by using perchloric acid method.

[0056] Example 5

[0057] Under inert atmosphere (the type of inert atmosphere is N2), 347.3 g of cardanol (1.15 mol) and 177.5 g of tetrazole-5-acetylhydrazine (1.25 mol) were mixed to complete dissolution at 97 ℃, cooled to 77 ℃, and 48 g of polyformaldehyde (molar amount of formaldehyde monomer: 1.6 mol) was added in batches (in 4 batches) at a temperature of 75-90 ℃. After being heated to 105 ℃ for 1.8 h and then heated to 146 ℃ for 3.5 h, the temperature was decreased to 105 ℃, and vacuum dehydration was performed at a vacuum degree of 2-3 kPa for 45 min. After being cooled to 69 ℃, 7.16 g of promoter triethanolamine and 7.16 g of N,N-dimethyl-1,3-propanediamine were added, and stirring and mixing were performed for 1.6 h to obtain a cardanol aldehyde amine epoxy resin curing agent containing a tetrazole structure;

[0058] Viscosity test at 25 ℃ was performed according to “Adhesive Viscosity Determination” GB / T2794-1995, and the test result was that the viscosity was 15500 mPa·s, and the amine value was 577.4 mg·KOH / g determined by using perchloric acid method.

[0059] Test Example

[0060] The cashew phenolic aldehyde amine epoxy resin curing agent with tetrazole structure prepared in Examples 1-5 is mixed with epoxy resin E51 (1:1 according to active hydrogen equivalent), and a glass strip of 100 μm is prepared according to GN / T 13452.2-2008 "Determination of the film thickness of paint and varnish"; the dry time of the glass strip after curing for 12 h (film thickness of 100 μm) at 25°C in a constant temperature and humidity chamber is shown in Table 1:

[0061] Table 1 Varnish dry time of glass strip

[0062] Example 1 Example 2 Example 3 Example 4 Example 5 Gel time 1.3 0.9 1.1 1.1 1.4 Tack-free time 2.2 1.6 1.7 1.8 2.5 Through dry time 3.7 2.7 3.1 3.4 3.9

[0063] The cashew phenolic aldehyde amine epoxy resin curing agent with tetrazole structure prepared in Examples 1-5 is mixed with epoxy resin E51 (1:1 according to active hydrogen equivalent), and a glass strip of 100 μm is prepared according to GN / T 13452.2-2008 "Determination of the film thickness of paint and varnish"; the dry time of the glass strip after curing for 12 h (film thickness of 100 μm) at 25°C in a constant temperature and humidity chamber is shown in Table 1:

[0064] Table 2 Performance parameters of the cashew phenolic aldehyde amine epoxy resin curing agent with tetrazole structure in Examples 1-5

[0065] Test item Example 1 Example 2 Example 3 Example 4 Example 5 Film thickness, pm 25±2 25±2 25±2 25±2 25±2 Crosshatch adhesion 0 0 0 0 0 Pencil hardness 2H H 2H H 2H Impact resistance, cm 100 100 100 100 100 Flexibility, mm 1 1 1 1 1 Corrosion width after 1000 h, mm 0.77 0.63 0.71 0.68 0.81

[0066] As shown in Tables 1-2, the cashew phenolic aldehyde amine epoxy resin curing agent with tetrazole structure has a faster curing speed, which can shorten the construction period of downstream applications; at the same time, it has very excellent mechanical properties and corrosion resistance: the impact strength is 100 cm, the scribe adhesion is 0 level, the flexibility is 1 mm, the hardness is H level or above, and the average salt spray corrosion width is 0.72 mm after 1000 h; in summary, the cashew phenolic aldehyde amine epoxy resin curing agent with tetrazole structure is used with E51 epoxy resin, which has a fast curing speed and excellent mechanical properties.

[0067] The above merely describes the preferred embodiments of the present application, and does not limit the present application in any form. It should be noted that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a cashew phenol amine epoxy resin curing agent containing a tetrazolium structure, characterized in that, Includes the following steps: In an inert atmosphere, cashew phenol and tetrazolium-5-acetylhydrazine are mixed, and a substance providing formaldehyde monomer is added. After the Mannich reaction and dehydration reaction are carried out in sequence, an accelerator is added to obtain the cashew phenol aldehyde amine epoxy resin curing agent with the tetrazolium structure. The molar ratio of formaldehyde monomer in cashew phenol, tetrazolium-5-acetylhydrazine, and the substance providing formaldehyde monomer is (1.0-1.2):(1.1-1.3):(1.4-1.6); The Mannich reaction process is as follows: first, the reaction is carried out at a temperature of 100-105℃ for 1-2 hours, and then at a temperature of 145-150℃ for 2.5-3.5 hours. The process of adding the substance that provides formaldehyde monomers is to add it in batches, and the number of batches is 4.

2. The preparation method according to claim 1, characterized in that, The substance providing formaldehyde monomers includes paraformaldehyde or an aqueous solution of formaldehyde with a mass concentration of 37%.

3. The preparation method according to claim 1, characterized in that, The mixing temperature is 90–100°C; The temperature at which the formaldehyde monomer is added is 75–90°C.

4. The preparation method according to claim 1, characterized in that, The dehydration reaction is carried out at a temperature of 100–105°C, a vacuum of 2–3 kPa, and a time of 40–50 min.

5. The preparation method according to claim 1, characterized in that, The accelerator includes one or two of 2,4,6-tris(dimethylaminomethyl)phenol, triethanolamine, and N,N-dimethyl-1,3-propanediamine.

6. The preparation method according to claim 1 or 5, characterized in that, The mass of the accelerator is 2 to 4% of the total mass of the cashew phenol, tetrazolium-5-acetylhydrazine, and the substance providing the formaldehyde monomer.

7. A cashew phenol amine epoxy resin curing agent containing a tetrazolium structure, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 6.

8. The application of the cashew phenol aldehyde amine epoxy resin curing agent containing a tetrazolium structure prepared by the preparation method according to any one of claims 1 to 6, or the cashew phenol aldehyde amine epoxy resin curing agent containing a tetrazolium structure according to claim 7, in the field of coating.

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