Cyanate resin curing agent, single-component latent cyanate resin and preparation methods of cyanate resin curing agent and single-component latent cyanate resin

Abstract

The invention relates to a cyanate resin curing agent, single-component latent cyanate resin and a preparation method, and belongs to the technical field of resin curing agents. The cyanate ester resin curing agent is prepared by carrying out a coordination reaction on a carboxyl-containing aromatic compound and a rare earth metal salt in a low-boiling-point solvent and a catalyst under the conditions of high temperature and high pressure; and further mixing the cyanate resin curing agent with the cyanate resin to obtain the room single-component latent cyanate resin. The cyanate resin curing agent provided by the invention has good compatibility with cyanate resin, the curing temperature and the curing time of the cyanate resin can be remarkably reduced, and the curing degree is remarkably improved. The single-component latent cyanate ester resin provided by the invention can be stored at room temperature for more than 5 days, and can be quickly cured at the temperature of 100-140 DEG C for 2 hours; therefore, the technical problem that manufacturability and medium-temperature and short-time curing of single-component cyanate ester resin cannot be achieved at the same time is solved.

Description

Technical Field

[0001] The present invention relates to a resin curing agent, and more particularly to a cyanate resin curing agent, a single-component latent cyanate resin and a preparation method thereof. Background Art

[0002] Cyanate resin is a kind of phenol derivative, which has multiple cyanate groups in its molecular structure, and the general structural formula is NCO-R-OCN. According to the different R groups in the structural formula of cyanate resin, cyanate resin usually includes phenolic type, bisphenol A type cyanate resin, etc. The cured cyanate resin has very excellent heat resistance, dielectric properties, mechanical properties, low water absorption and good processing properties. Cyanate ester-based composite materials can better meet the requirements of aerospace equipment for the use of resin materials. Its application field has been continuously broadened and widely used in aerospace, military industry, electronics industry, and civilian products, such as mechanical structural parts, wave-transmitting materials and high-frequency circuit board manufacturing. In terms of aviation materials, cyanate resin has been used as a structural material for radomes and satellite panels.

[0003] The characteristics of cyanate ester resin curing reaction are high curing temperature and long curing time. In the absence of curing agent, it is generally necessary to cure at a higher temperature (above 200°C) for a longer time (more than 7 hours) to obtain a larger degree of curing crosslinking. However, high temperature and long curing reaction often cause more residual stress inside the reactant, resulting in poor service stability of the material, thus hindering the development and large-scale application of cyanate ester resin and related materials.

[0004] Rare earth metals, also known as rare earth elements, are the general term for 17 elements in the scandium, yttrium, and lanthanide series in the IIIB group of the periodic table. Rare earth metal salts act as a catalyst to form a complex, bringing three active -OCN groups together. Under the action of the catalyst or autocatalysis, the difunctional cyanate ester is trimerized into a ring to form a trifunctional prepolymer. The trifunctional prepolymer continues to react, and as the molecular weight increases, it eventually forms a three-dimensional network structure with high density and high cross-linking degree. However, most rare earth metal salts have poor solubility in molten cyanate resins, which will lead to local explosion and low degree of curing after the rare earth metal salts are added to the cyanate resin. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a cyanate resin curing agent prepared by reacting a carboxyl-containing aromatic compound with a rare earth metal salt, a single-component latent cyanate resin and a preparation method.

[0006] The present invention has found through experimental research that the rare earth metal and the carboxyl-containing aromatic compound are reacted to form a rare earth metal complex, that is, the cyanate resin curing agent provided by the present invention, which can significantly improve the solubility of the rare earth metal salt in the molten cyanate resin. In addition, the cyanate resin curing agent provided by the present invention has good storage stability after being mixed with the cyanate resin, can significantly reduce the curing temperature of the cyanate resin, and can significantly improve the curing degree of the cyanate resin.

[0007] One of the purposes of the present invention is to provide a method for preparing a cyanate ester resin curing agent.

[0008] The preparation method of the cyanate resin curing agent comprises the following steps: a carboxyl-containing aromatic compound and a rare earth metal salt are subjected to coordination reaction in the presence of a low boiling point solvent, a catalyst and high temperature and high pressure conditions; the low boiling point solvent refers to a solvent with a boiling point of ≤160°C, preferably a low boiling point polar solvent.

[0009] In order to further obtain a cyanate resin curing agent with better performance, the materials used in the above preparation method, the weight ratio of the materials, and the reaction conditions are limited as follows:

[0010] The carboxyl-containing aromatic compound is one or more of trimesic acid, terephthalic acid, p-nitrobenzoic acid, 2,4-dichlorobenzoic acid, benzoic acid and 2-aminoterephthalic acid.

[0011] The rare earth metal salt is one or more of gadolinium trichloride, holmium acetate hydrate, lanthanum fluoride, ytterbium trichloride, cerium oxalate, lanthanum oxalate and erbium trichloride hexahydrate.

[0012] The low boiling point solvent is one or more of water, methanol, ethanol and N,N-dimethylformamide.

[0013] The catalyst is a strong acid or a medium-strong acid, preferably one or more of perchloric acid, hydroiodic acid, sulfuric acid, hydrobromic acid, hydrochloric acid, nitric acid and iodic acid.

[0014] The weight ratio of the rare earth metal salt to the carboxyl-containing aromatic compound is 3-8:10, preferably 5-6:10. In some embodiments of the present invention, the weight ratio of the rare earth metal salt to the carboxyl-containing aromatic compound is 5.5:10.

[0015] The weight ratio of the low boiling point solvent to the carboxyl-containing aromatic compound is 4-8:10, preferably 5-7:10. In some embodiments of the present invention, the weight ratio of the low boiling point solvent to the carboxyl-containing aromatic compound is 6:10.

[0016] The weight ratio of the catalyst to the carboxyl-containing aromatic compound is 0.1-0.6:10, preferably 0.2-0.4:10. In some embodiments of the present invention, the weight ratio of the catalyst to the carboxyl-containing aromatic compound is 0.35:10.

[0017] The high pressure condition is 0.15MPa-0.3MPa, preferably 0.2MPa-0.25MPa.

[0018] The high temperature condition is 80° C.-140° C., preferably 100° C.-120° C. In some embodiments of the present invention, the high temperature condition is 110° C.

[0019] Specifically, the preparation method of the cyanate ester resin curing agent may include the following steps: uniformly mixing the carboxyl-containing aromatic compound, rare earth metal salt, low boiling point solvent and catalyst, reacting under high temperature and high pressure conditions for more than 24 hours, and then washing and drying the product to obtain the cyanate ester resin curing agent.

[0020] In some embodiments of the present invention, the method for preparing the cyanate ester resin curing agent comprises:

[0021] Step 1, weighing raw materials in proportion, wherein the raw materials are carboxyl aromatic compounds, rare earth metal salts, low boiling point solvents and catalysts;

[0022] Step 2, add the raw materials weighed in proportion into a beaker and stir evenly, then transfer them to a hydrothermal kettle, heat to 80-140°C, and react at 0.15-0.3Mpa for more than 24 hours;

[0023] Step 3, washing the product in the hydrothermal kettle with water until the pH of the product is neutral, and drying it at 60° C. for 12 hours to obtain a cyanate resin curing agent.

[0024] The second object of the present invention is to provide a cyanate ester resin curing agent. The cyanate ester resin curing agent is prepared by the preparation method of the cyanate ester resin curing agent.

[0025] The cyanate resin curing agent prepared by the preparation method of the cyanate resin curing agent has a clear and stable crystal structure, and also has the characteristics of strong coordination, high electron hole defects and high polarity. Therefore, the cyanate resin curing agent has good compatibility with the cyanate resin, and the cyanate resin curing agent can be mixed with the cyanate resin to obtain a single-component cyanate resin; and the strong coordination and stable crystal form of the cyanate resin curing agent can ensure that the single-component cyanate resin maintains excellent storage stability at room temperature. The cyanate resin can also significantly reduce the curing temperature and curing time of the cyanate resin, and significantly improve the degree of curing.

[0026] The third object of the present invention is to provide a one-component latent cyanate resin, which comprises a cyanate resin and the cyanate resin curing agent as described above.

[0027] The weight ratio of the cyanate resin curing agent to the cyanate resin is 0.2-0.8:10, preferably 0.4-0.6:10. In some embodiments of the present invention, the weight ratio of the cyanate resin curing agent to the cyanate resin is 0.5:10.

[0028] Wherein, the cyanate resin is one or more of bisphenol A cyanate, phenolic cyanate and modified cyanate. The bisphenol A cyanate can be any existing bisphenol A cyanate. The phenolic cyanate can be any existing phenolic cyanate. The modified cyanate can be any existing modified cyanate.

[0029] The single-component latent cyanate resin provided by the present invention maintains excellent single-component storage stability of the cyanate resin at room temperature through the strong coordination and stable crystal form of the cyanate resin curing agent, and the room temperature storage stability is more than 5 days. The cyanate resin curing agent in the single-component latent cyanate resin dissociates and crystallizes and melts at high temperature to release active hydrogen and rare earth metal ions, thereby achieving rapid curing of the single-component latent cyanate resin, thereby breaking through the technical difficulty that the processability and medium-temperature short-time curing of the single-component cyanate resin cannot be achieved at the same time.

[0030] A fourth object of the present invention is to provide a method for preparing the above-mentioned one-component latent cyanate ester resin, wherein the method comprises mixing the cyanate ester resin and the cyanate ester resin curing agent.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention prepares a cyanate resin curing agent having good compatibility with cyanate resin and good stability by reacting a carboxyl-containing aromatic compound with a rare earth metal salt. The cyanate resin curing agent is further mixed with the cyanate resin to obtain a single-component latent cyanate resin having good room temperature stability, low curing temperature, low curing time and good curing degree.

[0033] The single-component latent cyanate resin provided by the present invention has a room temperature storage life of more than 5 days and can be quickly cured within 2 hours at a temperature of 100° C.-140° C.

[0034] In the present invention, unless otherwise specified, the water is deionized water. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a scanning electron microscope image of the cyanate resin curing agent prepared in Example 1 of the present invention;

[0036] Figure 2 is a transmission electron microscope image of the cyanate resin curing agent prepared in Example 1 of the present invention;

[0037] Figure 3 is a viscosity variation curve of the single-component latent cyanate ester resin prepared in Example 1 of the present invention over time;

[0038] Figure 4 3 is the reaction exothermic curve of the single-component latent cyanate ester resin prepared in Example 1 of the present invention; wherein the abscissa is time and the ordinate is heat flow. DETAILED DESCRIPTION

[0039] The present invention is described in detail below in conjunction with specific drawings and embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.

[0040] All reagents used were commercially available products.

[0041] Example 1

[0042] Step 1, weigh the raw materials in proportion: 11.5 parts by weight of erbium trichloride hexahydrate, 10 parts by weight of trimesic acid, 0.9 parts by weight of 0.1 mol / L perchloric acid and 6 parts by weight of methanol.

[0043] Step 2: Add the raw materials weighed in proportion into a beaker and stir evenly, then transfer them to a hydrothermal kettle, heat to 110° C., and react at 0.25 MPa for 24 hours.

[0044] Step 3, washing the product in the hydrothermal autoclave with deionized water until the pH of the product is neutral, and drying at 60° C. for 12 hours; thus, a latent cyanate resin curing agent is obtained.

[0045] Step 4: Mix 0.5 parts by weight of the cyanate resin curing agent prepared in step 3 with 10 parts by weight of bisphenol A type cyanate resin to prepare a single-component latent cyanate resin.

[0046] The cyanate resin curing agent prepared in this example was scanned by electron microscope to obtain the following Figure 1 The cyanate resin curing agent prepared in this example was tested by transmission electron microscopy, and the following results were obtained: Figure 2 The transmission electron microscope image shown. Figure 1 and Figure 2It can be concluded that the prepared cyanate ester resin curing agent has a regular polyhedral structure and high crystallinity, can protect the lone pair electron orbitals of the cyanate ester resin, and can form a stable coordination bond with the cyanate ester resin; therefore, after the prepared cyanate ester resin curing agent is mixed with the cyanate ester resin, the storage stability can be maintained at room temperature.

[0047] The viscosity of the single-component latent cyanate ester resin prepared in this embodiment was tested with a rotational viscometer; the test conditions were 25°C and a shear rate of 1s -1 ; Obtain the viscosity variation curve over time, such as Figure 3 shown. Figure 3 It is illustrated that the one-component latent cyanate ester resin prepared in this example has good room temperature storage stability (≥5 days), and there is no viscosity increase due to polymerization after being placed at room temperature for 5 days.

[0048] like Figure 4 As shown, the heat flow variation of the single-component latent cyanate ester resin prepared in this embodiment over time was tested by differential scanning calorimetry; the test conditions were 110°C, the test time was 600 minutes, the test atmosphere was nitrogen, and the reaction exothermic curve was obtained. It can react rapidly in the initial stage of the reaction (20 minutes), and a complete exothermic peak appears. The reaction exothermic is complete, which shows that the single-component latent cyanate ester resin prepared in this embodiment has a good degree of curing and a low reaction temperature. It also proves that the cyanate ester resin prepared in this embodiment has good room temperature storage stability, which can effectively reduce the reaction temperature and increase the degree of reaction.

[0049] Example 2

[0050] Step 1, weigh the raw materials in proportion: 10 parts by weight of lanthanum oxalate, 10 parts by weight of p-nitrobenzoic acid, 0.7 parts by weight of 0.1 mol / L hydrobromic acid and 13 parts by weight of deionized water.

[0051] Step 2: Add the raw materials weighed in proportion into a beaker and stir evenly, then transfer them to a hydrothermal kettle, heat to 140° C., and react at 0.3 MPa for 24 hours.

[0052] Step 3, washing the product in the hydrothermal autoclave with deionized water until the pH of the product is neutral, and drying at 60° C. for 12 hours; thus, a latent cyanate resin curing agent is obtained.

[0053] Step 4: Mix 0.2 parts by weight of the cyanate resin curing agent prepared in step 3 with 10 parts by weight of phenolic cyanate resin to prepare a single-component latent cyanate resin.

[0054] Example 3

[0055] Step 1, weigh the raw materials in proportion, 11 parts by weight of cerium oxalate, 10 parts by weight of 2-aminoterephthalic acid, 0.6 parts by weight of 0.1 mol / L hydrochloric acid and 3.2 parts by weight of ethanol.

[0056] Step 2: Add the raw materials weighed in proportion into a beaker and stir evenly, then transfer them to a hydrothermal kettle, heat to 80° C., and react at 0.15 MPa for 24 hours.

[0057] Step 3, washing the product in the hydrothermal autoclave with deionized water until the pH of the product is neutral, and drying at 60° C. for 12 h to obtain a latent cyanate ester resin curing agent.

[0058] Step 4: 0.8 parts by weight of the latent cyanate resin curing agent prepared in step 3 is mixed with 10 parts by weight of the modified cyanate resin to prepare a single-component latent cyanate resin.

[0059] Example 4

[0060] Step 1, weigh the raw materials in proportion: 8 parts by weight of gadolinium trichloride, 10 parts by weight of terephthalic acid, 0.1 parts by weight of 0.1 mol / L hydroiodic acid and 6 parts by weight of deionized water.

[0061] Step 2: Add the raw materials weighed in proportion into a beaker and stir evenly, then transfer them to a hydrothermal kettle, heat to 100° C., and react at 0.4 MPa for 24 hours.

[0062] Step 3, washing the product in the hydrothermal autoclave with deionized water until the pH of the product is neutral, and drying at 60° C. for 12 hours; thus, a latent cyanate resin curing agent is obtained.

[0063] Step 4: Mix 0.2 parts by weight of the cyanate resin curing agent prepared in step 3 with 10 parts by weight of phenolic cyanate resin to prepare a single-component latent cyanate resin.

[0064] The cyanate resin curing agent prepared in this example was tested by transmission electron microscopy, scanning electron microscopy, differential scanning calorimetry and rotational viscometer. The results showed that this example had low curing temperature, fast curing time, high degree of curing, high storage stability and excellent mechanical properties of the cured product.

[0065] Example 5

[0066] Step 1, weigh the raw materials in proportion: 8 parts by weight of hydrated holmium acetate, 10 parts by weight of 2,4-dichlorobenzoic acid, 0.1 parts by weight of 0.1 mol / L nitric acid and 6 parts by weight of N,N-dimethylformamide.

[0067] Step 2: Add the raw materials weighed in proportion into a beaker and stir evenly, then transfer them to a hydrothermal kettle, heat to 100° C., and react at 0.4 MPa for 24 hours.

[0068] Step 3, washing the product in the hydrothermal autoclave with deionized water until the pH of the product is neutral, and drying at 60° C. for 12 hours; thus, a latent cyanate resin curing agent is obtained.

[0069] Step 4: Mix 0.2 parts by weight of the cyanate resin curing agent prepared in step 3 with 10 parts by weight of phenolic cyanate resin to prepare a single-component latent cyanate resin.

[0070] The cyanate resin curing agent prepared in this example was tested by transmission electron microscopy, scanning electron microscopy, differential scanning calorimetry and rotational viscometer. The results showed that this example had low curing temperature, fast curing time, high degree of curing, high storage stability and excellent mechanical properties of the cured product.

[0071] Example 6

[0072] Step 1, weigh the raw materials in proportion: 8 parts by weight of hydrated lanthanum fluoride, 10 parts by weight of benzoic acid, 0.1 parts by weight of 0.1 mol / L sulfuric acid and 6 parts by weight of N,N-dimethylformamide.

[0073] Step 2: Add the raw materials weighed in proportion into a beaker and stir evenly, then transfer them to a hydrothermal kettle, heat to 100° C., and react at 0.4 MPa for 24 hours.

[0074] Step 3, washing the product in the hydrothermal autoclave with deionized water until the pH of the product is neutral, and drying at 60° C. for 12 hours; thus, a latent cyanate resin curing agent is obtained.

[0075] Step 4: Mix 0.2 parts by weight of the cyanate resin curing agent prepared in step 3 with 10 parts by weight of phenolic cyanate resin to prepare a single-component latent cyanate resin.

[0076] The cyanate resin curing agent prepared in this example was tested by transmission electron microscopy, scanning electron microscopy, differential scanning calorimetry and rotational viscometer. The results showed that this example had low curing temperature, fast curing time, high degree of curing, high storage stability and excellent mechanical properties of the cured product.

[0077] Example 7

[0078] Step 1, weigh the raw materials in proportion: 8 parts by weight of ytterbium trichloride, 10 parts by weight of benzoic acid, 0.1 parts by weight of 0.1 mol / L iodic acid and 6 parts by weight of N,N-dimethylformamide.

[0079] Step 2: Add the raw materials weighed in proportion into a beaker and stir evenly, then transfer them to a hydrothermal kettle, heat to 100° C., and react at 0.4 MPa for 24 hours.

[0080] Step 3, washing the product in the hydrothermal autoclave with deionized water until the pH of the product is neutral, and drying at 60° C. for 12 hours; thus, a latent cyanate resin curing agent is obtained.

[0081] Step 4: Mix 0.2 parts by weight of the cyanate resin curing agent prepared in step 3 with 10 parts by weight of phenolic cyanate resin to prepare a single-component latent cyanate resin.

[0082] The cyanate resin curing agent prepared in this example was tested by transmission electron microscopy, scanning electron microscopy, differential scanning calorimetry and rotational viscometer. The results showed that this example had low curing temperature, fast curing time, high degree of curing, high storage stability and excellent mechanical properties of the cured product.

Claims

1. A method for preparing a cyanate resin curing agent, characterized in that: The preparation method comprises the following steps: a carboxyl-containing aromatic compound and a rare earth metal salt are subjected to coordination reaction in the presence of a low boiling point solvent, a catalyst and high temperature and high pressure conditions; the low boiling point solvent refers to a solvent with a boiling point of ≤160°C, preferably a low boiling point polar solvent.

2. The preparation method according to claim 1, characterized in that The carboxyl-containing aromatic compound is one or more of trimesic acid, terephthalic acid, p-nitrobenzoic acid, 2,4-dichlorobenzoic acid, benzoic acid and 2-aminoterephthalic acid; or / and, The rare earth metal salt is one or more of gadolinium trichloride, holmium acetate hydrate, lanthanum fluoride, ytterbium trichloride, cerium oxalate, lanthanum oxalate and erbium trichloride hexahydrate; or / and, The low boiling point solvent is one or more of water, methanol, ethanol and N,N-dimethylformamide; or / and, The catalyst is a strong acid or a medium-strong acid, preferably one or more of perchloric acid, hydroiodic acid, sulfuric acid, hydrobromic acid, hydrochloric acid, nitric acid and iodic acid.

3. The preparation method according to claim 1, characterized in that: The weight ratio of the rare earth metal salt to the carboxyl-containing aromatic compound is 7-15:10, preferably 10-12:10; The weight ratio of the low boiling point solvent to the carboxyl-containing aromatic compound is 2.5-13:10, preferably 5-7:10; The weight ratio of the catalyst to the carboxyl-containing aromatic compound is 0.1-1.5:10, preferably 0.2-0.4:

10.

4. The preparation method according to claim 1, characterized in that: The high pressure condition is 0.15MPa-0.3MPa, preferably 0.2MPa-0.25MPa; or / and, The high temperature condition is 80°C-140°C, preferably 100°C-120°C.

5. The preparation method according to claim 1, characterized in that: The preparation method comprises the following steps: uniformly mixing the carboxyl-containing aromatic compound, rare earth metal salt, low boiling point solvent and catalyst, reacting for more than 24 hours under high temperature and high pressure conditions, and then washing and drying the product to obtain the cyanate resin curing agent.

6. A cyanate resin curing agent, characterized in that: The cyanate resin curing agent is prepared by the preparation method according to any one of claims 1 to 5.

7. A one-component latent cyanate resin, characterized in that: The one-component latent cyanate resin comprises a cyanate resin and the cyanate resin curing agent as claimed in claim 6.

8. The one-component latent cyanate ester resin according to claim 7, characterized in that: The weight ratio of the cyanate resin curing agent to the cyanate resin is 0.2-0.8:10, preferably 0.4-0.6:

10.

9. The one-component latent cyanate ester resin according to claim 7, characterized in that: The cyanate ester resin is one or more of bisphenol A cyanate ester, phenolic cyanate ester and modified cyanate ester.

10. A method for preparing a single-component latent cyanate ester resin as claimed in claim 7, 8 or 9, characterized in that: The preparation method includes mixing the cyanate resin and the cyanate resin curing agent.

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