Preparation method of flame retardant cyanate ester resin adhesive

Abstract

The invention discloses a method for preparing a flame-retardant cyanate ester resin adhesive. The method comprises the following steps: preparing a phosphorus-containing phenolic resin and a silicon-containing phenolic resin respectively, reacting the prepared phosphorus-containing cyanate ester resin with hydrogen bromide to obtain a phosphorus-containing cyanate ester resin and a silicon-containing cyanate ester resin respectively, and mixing the prepared phosphorus-containing cyanate ester resin with the silicon-containing cyanate ester resin to obtain a flame-retardant cyanate ester resin adhesive. The phenolic resin is modified by using a phosphate ester so that the phenolic resin can be connected using the phosphate ester as a connection point. This allows a dense carbon layer to be formed on the surface of the resin during combustion. This prevents further pyrolysis of the resin and prevents substances generated by thermal decomposition inside the resin from entering the gas phase and participating in combustion. The presence of silicon element can improve the stability of the formed carbon layer, increase the residual carbon content of the carbon layer at high temperature, and enhance the structural strength of the carbon layer, thereby effectively solving the problem that the carbon layer is easily broken when the phosphorus content of the resin is low, resulting in a decrease in the flame retardant effect.

Description

Technical Field

[0001] The invention relates to the technical field of polymer resin materials, in particular to a method for preparing a flame retardant cyanate ester resin adhesive. Background Art

[0002] Cyanate ester resin has good high temperature resistance and low dielectric properties, and is very suitable for use as an adhesive. In addition, the water absorption rate of cyanate ester resin is extremely low, usually less than 1.5%, which is very effective in improving the stability and reliability of adhesives in humid environments. It also has low curing absorption rate, low molding shrinkage rate, and good dimensional stability, which makes the strength of the bonding more reliable. Patent CN118725219A provides a phenolic cyanate ester resin, a preparation method and an application. The cyanate resin is prepared using phenolic resin and hydrogen bromide as raw materials. The obtained resin has the characteristics of high strength and high temperature resistance. However, as an organic material, its flame retardant properties cannot meet the growing flame retardant performance requirements of modern materials. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing a flame retardant cyanate ester resin adhesive with excellent flame retardant effect.

[0004] In order to solve the above technical problems, the present invention comprises the following steps:

[0005] S1 Introduction of phosphorus-containing flame retardant groups: 1-2.5 kg of phenolic resin and 3-7 mol of phosphate compound are mixed in a reaction solvent, hydrogen chloride is added as a catalyst, the mixture is reacted at a temperature range of 60°C-80°C for 1-2 hours, and distilled at 75-79°C under normal pressure for 0.5 hours. Dichloromethane is added to fully dissolve the mixture, and then toluene is added to fully dissolve the mixture. The solution is filtered and the solvent is evaporated to obtain a phosphorus-containing phenolic resin.

[0006] S2 introduction of silicon-containing flame retardant groups: 1-2.5 kg of phenolic resin and 2-4 mol of silanol compound are mixed in a reaction solvent, stirred and gradually heated to reflux of the solvent, reacted for 3-5 hours, and then added with dichloromethane to fully dissolve, and then added with butanone to fully dissolve, the solution is filtered, and the solvent is evaporated to obtain a silicon-containing phenolic resin;

[0007] Preparation of S3 cyanate resin: 1-2.5 kg of each of the phosphorus-containing phenolic resin prepared in S1 and the silicon-containing phenolic resin prepared in S2 are weighed and mixed with 10-30 mol of hydrogen bromide in a reaction solvent, a catalyst is added, and the mixture is reacted at a temperature range of 50-55° C. for 5-15 hours. Dichloromethane is added to fully dissolve the mixture, followed by butanone to fully dissolve the mixture. The solution is filtered and evaporated to remove the solvent, thereby preparing a phosphorus-containing cyanate resin and a silicon-containing cyanate resin, respectively.

[0008] S4 mixing: mixing the phosphorus-containing cyanate resin and the silicon-containing cyanate resin prepared in S3 to prepare a flame-retardant cyanate resin adhesive.

[0009] Preferably, the mass of the phenolic resin described in S1 is 2 kg, and the amount of the phosphate compound is 5 mol.

[0010] Preferably, the mass of the phenolic resin described in S2 is 2 kg, and the amount of the silanol compound is 3 mol.

[0011] Preferably, the phosphate compound described in S1 is triphenyl phosphate, tricresyl phosphate, isopropylated triphenyl phosphate, triethyl phosphate or BDP (bisphenol A-bis(diphenyl phosphate)).

[0012] Preferably, the silanol compound described in S2 is trimethylsilanol, triphenylsilanol, tripropylsilanol or polydimethylsiloxane.

[0013] Preferably, the catalyst described in S3 is trialkylamine or triethylamine.

[0014] Preferably, the mass ratio of the phosphorus-containing cyanate resin to the silicon-containing cyanate resin in S4 is 7:5.

[0015] The beneficial effects of the present invention are:

[0016] Modifying phenolic resins with phosphate esters allows them to be connected using the phosphate esters as connection points. This allows a dense carbon layer to form on the resin surface during combustion. This not only prevents further thermal decomposition of the resin, but also prevents substances produced by thermal decomposition within the resin from entering the gas phase and participating in combustion. The presence of silicon improves the stability of the formed carbon layer, increases the amount of residual carbon in the carbon layer at high temperatures, and enhances the structural strength of the carbon layer, effectively solving the problem of the carbon layer being easily broken and causing a decrease in flame retardancy when the resin has a low phosphorus content. The present invention improves the flame retardancy of cyanate ester resins through the synergistic effect of phosphorus and silicon, even when the phosphorus content of the reactive flame retardant is limited. DETAILED DESCRIPTION

[0017] Unless otherwise specified, the instruments, reagents, and materials used in the following examples are all conventional instruments, reagents, and materials available in the prior art and can be obtained through regular commercial channels. The experimental methods and detection methods used in the following examples are all conventional experimental methods and detection methods available in the prior art, unless otherwise specified.

[0018] The phenolic resin used in all the following specific examples and comparative examples is thermoplastic novolac resin, and has an average molecular weight of 650. In the present invention, fully dissolved means that the solvent is added during the stirring process until the solid phase no longer decreases.

[0019] Example 1:

[0020] S1 Introduction of phosphorus-containing flame retardant groups: 2 kg of phenolic resin and 5 mol of triphenyl phosphate were mixed in 10 L of butanone, hydrogen chloride was added to adjust the pH value to be within the range of 4.2-4.5, the reaction was carried out at a temperature range of 60°C-70°C for 2 h, and distilled at 75°C under normal pressure for 0.5 h. After adding dichloromethane to fully dissolve the mixture, toluene was added to fully dissolve the mixture, the solution was filtered, and the solvent was evaporated to obtain a phosphorus-containing phenolic resin.

[0021] S2 introduction of silicon-containing flame retardant groups: 2 kg of phenolic resin and 3 mol of trimethylsilanol were mixed in 10 L of acetone, stirred and gradually heated to reflux, reacted for 4 h, and then added with dichloromethane to fully dissolve, and then with butanone to fully dissolve, the solution was filtered, and the solvent was evaporated to obtain a silicon-containing phenolic resin;

[0022] Preparation of S3 cyanate resin: 1 kg of each of the phosphorus-containing phenolic resin prepared in S1 and the silicon-containing phenolic resin prepared in S2 was weighed and mixed with 15 mol of hydrogen bromide in 20 L of acetone. 0.5 mol of trialkylamine was added as a catalyst, and the mixture was reacted at 50°C for 6 h. Dichloromethane was added to fully dissolve the mixture, followed by butanone to fully dissolve the mixture. The solution was filtered and evaporated to remove the solvent, thereby preparing a phosphorus-containing cyanate resin and a silicon-containing cyanate resin, respectively.

[0023] S4 mixing: mixing the phosphorus-containing cyanate resin and the silicon-containing cyanate resin prepared in S3 at a mass ratio of 7:5 to prepare a flame-retardant cyanate resin adhesive.

[0024] The limiting oxygen index (LOI) of the flame retardant cyanate resin adhesive prepared by S4 was measured in accordance with GB / J2406.2-2009. The LOI of this embodiment was 37.2. The carbon residue rate and the 5% thermal weight loss temperature (T 5％ ), the carbon residue rate at 700℃ is 46.8%, T 5％ It is 383℃.

[0025] Example 2:

[0026] The difference from Example 1 is that tricresyl phosphate is used as the phosphate ester compound instead of triphenyl phosphate, and triphenylsilanol is used as the silanol compound instead of trimethylsilanol.

[0027] The flame retardant cyanate resin adhesive prepared in this embodiment has a LOI of 36.7, a carbon residue rate of 44.5% at 700°C, and a T 5％ It is 378℃.

[0028] Example 3:

[0029] The difference from Example 1 is that isopropylated triphenyl phosphate is used as the phosphate ester compound instead of triphenyl phosphate, and tripropylsilanol is used as the silanol compound instead of trimethylsilanol.

[0030] The flame retardant cyanate resin adhesive prepared in this embodiment has a LOI of 35.9, a carbon residue rate of 42.4% at 700°C, and a T 5％ It is 370℃.

[0031] Example 4:

[0032] The difference from Example 1 is that BDP is used as the phosphate compound instead of triphenyl phosphate, and polydimethylsiloxane is used as the silanol compound instead of trimethylsilanol.

[0033] The flame retardant cyanate resin adhesive prepared in this embodiment has a LOI of 35.1, a carbon residue rate of 44.6% at 700°C, and a T 5％ It is 354℃.

[0034] Example 5:

[0035] The difference from Example 1 is that S1 uses 1 kg of phenolic resin and 3 moles of triphenyl phosphate for reaction, and S2 uses 1 kg of phenolic resin and 2 moles of trimethylsilanol for reaction.

[0036] The flame retardant cyanate resin adhesive prepared in this embodiment has a LOI of 36.3, a carbon residue rate of 37.4% at 700°C, and a T 5％ It is 336℃.

[0037] Example 6:

[0038] The difference from Example 1 is that S1 uses 2.5 kg of phenolic resin and 7 mol of triphenyl phosphate for reaction, and S2 uses 2.5 kg of phenolic resin and 4 mol of trimethylsilanol for reaction.

[0039] The flame retardant cyanate resin adhesive prepared in this embodiment has a LOI of 36.5, a carbon residue rate of 38.4% at 700°C, and a T 5％ It is 374℃.

[0040] Example 7:

[0041] The difference from Example 1 is that, in S4, the phosphorus-containing cyanate resin and the silicon-containing cyanate resin are mixed in a mass ratio of 1:1.

[0042] The flame retardant cyanate resin adhesive prepared in this embodiment has a LOI of 33.6, a carbon residue rate of 36.8% at 700°C, and a T 5％ It is 367℃.

[0043] Example 8:

[0044] The difference from Example 1 is that, in S4, the phosphorus-containing cyanate resin and the silicon-containing cyanate resin are mixed in a mass ratio of 8:5.

[0045] The flame retardant cyanate resin adhesive prepared in this embodiment has a LOI of 36.0, a carbon residue rate of 38.8% at 700°C, and a T 5％ It is 342℃.

[0046] Comparative Example 1:

[0047] 2 kg of phenolic resin and 5 mol of triphenyl phosphate are mixed in 10 L of butanone, 1 mol of hydrogen chloride is added, the mixture is reacted in the temperature range of 60°C-70°C for 2 hours, distilled at 75°C under normal pressure for 0.5 hour, dichloromethane is added for full dissolution, toluene is added for full dissolution, the solution is filtered out, and the solution is evaporated to remove the solvent to obtain a phosphorus-containing phenolic resin; 1 kg of phosphorus-containing phenolic resin is mixed with 15 mol of hydrogen bromide in a reaction solvent, trialkylamine is added as a catalyst, the mixture is reacted in the temperature range of 50°C for 6 hours, dichloromethane is added for full dissolution, butanone is added for full dissolution, the solution is filtered out, and the solution is evaporated to remove the solvent to obtain a phosphorus-containing cyanate resin.

[0048] The phosphorus-containing cyanate resin prepared in this comparative example has a LOI of 33.5, a carbon residue rate of 29.5% at 700°C, and a T 5％ It is 284℃.

[0049] Comparative Example 2:

[0050] 2 kg of phenolic resin and 3 mol of trimethylsilanol were mixed in 10 L of acetone, stirred and gradually heated to solvent reflux, reacted for 4 h, added with dichloromethane to fully dissolve, then added with butanone to fully dissolve, filtered out the solution, evaporated the solution to remove the solvent, and prepared a silicon-containing phenolic resin; 1 kg of silicon-containing phenolic resin was mixed with 15 mol of hydrogen bromide in a reaction solvent, trialkylamine was added as a catalyst, reacted at a temperature range of 50°C for 6 h, added with dichloromethane to fully dissolve, then added with butanone to fully dissolve, filtered out the solution, evaporated the solution to remove the solvent, and prepared a silicon-containing cyanate resin.

[0051] The silicon cyanate resin prepared in this comparative example has a LOI of 32.4, a carbon residue rate of 33.6% at 700°C, and a T 5％ It is 276℃.

[0052] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a flame retardant cyanate ester resin adhesive, characterized in that: The following steps are involved: S1 Introduction of phosphorus-containing flame retardant groups: 1-2.5 kg of phenolic resin and 3-7 mol of phosphate compound are mixed in a reaction solvent, hydrogen chloride is added as a catalyst, the mixture is reacted at a temperature range of 60°C-80°C for 1-2 hours, and distilled at 75-79°C under normal pressure for 0.5 hours. Dichloromethane is added to fully dissolve the mixture, and then toluene is added to fully dissolve the mixture. The solution is filtered and the solvent is evaporated to obtain a phosphorus-containing phenolic resin. S2 introduction of silicon-containing flame retardant groups: 1-2.5 kg of phenolic resin and 2-4 mol of silanol compound are mixed in a reaction solvent, stirred and gradually heated to reflux of the solvent, reacted for 3-5 hours, and then added with dichloromethane to fully dissolve, and then added with butanone to fully dissolve, the solution is filtered, and the solvent is evaporated to obtain a silicon-containing phenolic resin; Preparation of S3 cyanate resin: 1-2.5 kg of each of the phosphorus-containing phenolic resin prepared in S1 and the silicon-containing phenolic resin prepared in S2 are weighed and mixed with 10-30 mol of hydrogen bromide in a reaction solvent, a catalyst is added, and the mixture is reacted at a temperature range of 50-55° C. for 5-15 hours. Dichloromethane is added to fully dissolve the mixture, followed by butanone to fully dissolve the mixture. The solution is filtered and evaporated to remove the solvent, thereby preparing a phosphorus-containing cyanate resin and a silicon-containing cyanate resin, respectively. S4 mixing: mixing the phosphorus-containing cyanate resin and the silicon-containing cyanate resin prepared in S3 to prepare a flame-retardant cyanate resin adhesive.

2. The method for preparing a flame retardant cyanate ester resin adhesive according to claim 1, wherein: The mass of the phenolic resin described in S1 is 2 kg, and the amount of the phosphate compound is 5 mol.

3. The method for preparing the flame retardant cyanate ester resin adhesive according to claim 1, wherein: The mass of the phenolic resin described in S2 is 2 kg, and the amount of the silanol compound is 3 mol.

4. The method for preparing a flame retardant cyanate ester resin adhesive according to claim 1, wherein: The phosphate compound described in S1 is triphenyl phosphate, tricresyl phosphate, isopropylated triphenyl phosphate, triethyl phosphate or BDP (bisphenol A-bis(diphenyl phosphate)).

5. The method for preparing the flame retardant cyanate ester resin adhesive according to claim 1, wherein: The silanol compound described in S2 is trimethylsilanol, triphenylsilanol or tripropylsilanol.

6. The method for preparing the flame retardant cyanate ester resin adhesive according to claim 1, wherein: The catalyst described in S3 is trialkylamine or triethylamine.