Cyanate resin composition, preparation method thereof and flame-retardant resin

Abstract

The invention provides a cyanate ester resin composition, a preparation method thereof and flame-retardant resin. The preparation method comprises the following steps: S1, carrying out first mixing on a cyanate ester monomer and a modified cyanate ester monomer to obtain a mixed monomer; s2, carrying out polymerization reaction on the mixed monomer to obtain a prepolymer; s3, carrying out second mixing on the prepolymer and epoxy resin to obtain a cyanate ester resin composition; the structure of the modified cyanate ester monomer comprises phosphino and phenyl. Phenyl and phosphino are introduced into a cyanate ester resin composition system through the modified cyanate ester monomer, the obtained cyanate ester resin is endowed with excellent flame retardant property, meanwhile, triazine cyclization of cyanate ester groups is catalyzed by electron-withdrawing P = O groups, so that the curing activation energy of the cyanate ester resin is reduced, the curing temperature moves towards the low-temperature direction, and the curing performance of the cyanate ester resin is improved. Therefore, the curing temperature is reduced.

Description

Technical Field

[0001] The present invention relates to the field of cyanate resins, and in particular to a cyanate resin composition, a preparation method thereof, and a flame retardant resin. Background Art

[0002] Cyanate ester resins, due to their unique triazine ring structure, possess excellent mechanical properties, weather resistance, and high heat resistance. Furthermore, the high crosslink density and resistance to polarization of cyanate esters give them unique low dielectric constant and dielectric loss characteristics over a wide frequency range. With the development and popularization of high-frequency communication technologies in electronic circuit boards and aerospace, high-quality, high-performance cyanate esters have gradually replaced epoxy resins in recent years and become the new darling of the electronic communications field. However, as a thermosetting resin, cyanate esters, while offering excellent performance, suffer from poor flame retardancy, limiting their development and application in the field of electronic communications. When flame-retardant modification is applied to cyanate ester resins, additive flame retardants and monofunctional flame retardants tend to increase the polarity of the crosslinked network, leading to an increase in the dielectric constant.

[0003] Phosphorus-based flame retardants, with their unique flame retardant mechanism, have become a major alternative to halogen flame retardants. Existing technologies typically use phosphorus-based flame retardants as additives to enhance the flame retardancy of cyanate ester resins. However, phosphorus-based flame retardants, when compounded with resins, typically have a negative impact on the mechanical and thermal properties of polymer resins.

[0004] Based on this, how to provide a cyanate resin composition with intrinsic flame retardancy and obtain a resin with good comprehensive performance and flame retardancy after polymerization and curing is one of the technical problems that need to be solved in this field. Summary of the Invention

[0005] The main purpose of the present invention is to provide a cyanate ester resin composition, a preparation method thereof and a flame retardant resin, so as to solve the problem that the cyanate ester resin in the prior art cannot have excellent flame retardancy, mechanical properties, processability and heat resistance.

[0006] To achieve the above-mentioned object, the first aspect of the present invention provides a method for preparing a cyanate ester resin composition, comprising: step S1, first mixing a cyanate ester monomer and a modified cyanate ester monomer to obtain a mixed monomer; step S2, subjecting the mixed monomer to a polymerization reaction to obtain a prepolymer; and step S3, second mixing the prepolymer with an epoxy resin to obtain a resin composition; the structure of the modified cyanate ester monomer includes a phosphine group and a phenyl group.

[0007] Furthermore, the modified cyanate ester monomer has a structure shown in Formula I:

[0008]

[0009] Furthermore, the preparation method of the modified cyanate ester monomer includes: adding a cyanogen halide and a bisphenol phenyl phosphine oxide to a solvent, mixing to obtain a mixed solution; adding an organic base to the mixed solution for reaction to obtain a modified cyanate ester monomer; the bisphenol phenyl phosphine oxide has a structure shown in Formula II:

[0010]

[0011] Furthermore, the molar ratio of the cyanogen halide to the bisphenol phenylphosphine oxide is (1.8-2.2):1; and / or the molar ratio of the organic base to the cyanogen halide is (1.8-2):1; preferably, the cyanogen halide is selected from one or more of cyanogen fluoride, cyanogen chloride and cyanogen bromide; preferably, the organic base is selected from one or more of triethylamine, diethylamine, trimethylamine and N,N-dimethylphenethylamine.

[0012] Furthermore, the weight ratio of the cyanate ester monomer, the modified cyanate ester monomer and the epoxy resin is 100:(2-20):(2-20).

[0013] Furthermore, in step S1, the temperature of the first mixing is 90°C to 130°C; and / or, in step S2, the temperature of the polymerization reaction is 150°C to 180°C; and / or, in step S3, the temperature of the second mixing is 90°C to 130°C; preferably, the time for the first mixing, the polymerization reaction and the second mixing is each independently 0.1h to 2h.

[0014] Furthermore, the cyanate monomer is selected from one or more of bisphenol A cyanate, tetramethyl bisphenol F cyanate, bisphenol E cyanate, bisphenol M cyanate, 4,4'-oxybisphenyl cyanate, bis(4-cyanate)sulfane and 4,4'-(1,3-hexafluoropropane-2,2-substituted)bisphenyl cyanate.

[0015] Furthermore, the epoxy resin is selected from one or more of bisphenol A epoxy resin E-51, bisphenol A epoxy resin E-54, bisphenol A epoxy resin E-44, novolac epoxy resin E-44, novolac epoxy resin E-46 and bisphenol S epoxy resin.

[0016] A second aspect of the present invention provides a cyanate ester resin composition, which is prepared by the above-mentioned method for preparing a cyanate ester resin composition.

[0017] A third aspect of the present invention provides a flame-retardant resin obtained by sequentially subjecting the above-mentioned cyanate resin composition to vacuum degassing and thermal curing. Preferably, the vacuum degassing temperature is 80°C to 100°C for 1 to 3 hours; preferably, the thermal curing comprises a first-stage curing, a second-stage curing, and a third-stage curing performed sequentially; more preferably, the first-stage curing temperature is 110°C to 150°C for 1 to 3 hours; the second-stage curing temperature is 150°C to 210°C for 1 to 4 hours; and the third-stage curing temperature is 190°C to 250°C for 2 to 6 hours.

[0018] The present invention utilizes a modified cyanate ester monomer to introduce phenyl and phosphine groups into the cyanate ester resin composition, imparting excellent flame retardancy to the resulting cyanate ester resin. Simultaneously, the electron-withdrawing P=O group catalyzes the triazine ring formation of the cyanate ester group, thereby reducing the resin's curing activation energy and shifting the curing temperature toward lower temperatures. This unique structure also imparts excellent thermal and mechanical properties to the polymerized resin, along with superior oxidative stability and a high glass transition temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0020] Figure 1 This is the infrared spectrum of the flame retardant resin obtained in Example 1. DETAILED DESCRIPTION

[0021] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0022] As described in the background art, existing cyanate resins have the problem of not being able to simultaneously achieve excellent flame retardancy, mechanical properties, processability, and heat resistance. To address the above technical issues, the first aspect of the present invention provides a method for preparing a cyanate resin composition, comprising: step S1, first mixing a cyanate ester monomer and a modified cyanate ester monomer to obtain a mixed monomer; step S2, subjecting the mixed monomer to a polymerization reaction to obtain a prepolymer; and step S3, second mixing the prepolymer with an epoxy resin to obtain a resin composition; the modified cyanate ester monomer comprises a phosphine group and a phenyl group in its structure.

[0023] The present invention prepolymerizes a modified cyanate monomer containing a phosphino group and a phenyl group with an unmodified cyanate monomer, and then mixes the resulting prepolymer with an epoxy resin, successfully introducing the phosphino group and the phenyl group into the main chain structure of the cyanate resin composition. The modified cyanate monomer comprises a cyanate group (-OCN) structure and a triphenylphosphine oxide structure, and is combined with a conventional cyanate monomer and an epoxy resin system to obtain a polymeric resin, thereby imparting flame retardant properties to the polymeric resin. Due to the triazine structure of the aromatic heterocycle, the polymeric resin not only has excellent high glass transition temperature and low dielectric constant, but also, the cyanate monomer that can participate in the reaction is different from an additive flame retardant and can maintain the mechanical properties of the cyanate resin. At the same time, the highly polar PO group also catalyzes the triazine ring formation of the cyanate group, which can effectively improve the curing reaction activity, reduce the curing reaction temperature, and also exhibit useful mechanical properties and chemical stability after curing.

[0024] Furthermore, the modified cyanate ester monomer has a structure shown in Formula I:

[0025]

[0026] That is, the modified cyanate monomer is bis(4,4-phenoxycyanate)triphenylphosphine oxide, whose structure contains a cyanate group (-OCN) structure, a triphenylphosphine oxide structure, and a biphenyl structural fragment. Compared with other phosphine-containing cyanate monomers, this compound can undergo polymerization reactions more efficiently and obtain a more stable polymer product, thus exhibiting superior flame retardancy. Compared with bis(4-cyanate phenyl)phenylphosphine oxide, which is more similar to it in structure, this monomer is a non-crystalline solid and has better compatibility with the cyanate resin system. The connection of aromatic ether can also moderately improve the toughness of the resin and lower the softening point. At the same time, the modified cyanate monomer has a glass transition temperature significantly higher than that of bis(4-cyanate phenyl)phenylphosphine oxide. In addition, the preparation of bis(4-cyanate phenyl)phenylphosphine oxide commonly used in the art is affected by the stronger electron-withdrawing force of the P=O group, and its conversion yield is significantly lower than that of the modified cyanate monomer.

[0027] In several typical embodiments, the preparation method of the modified cyanate ester monomer includes: adding a cyanogen halide and a bisphenol phenylphosphine oxide to a solvent, mixing to obtain a mixed solution; adding an organic base to the mixed solution for reaction to obtain a modified cyanate ester monomer; the bisphenol phenylphosphine oxide has a structure shown in Formula II:

[0028]

[0029] The preparation method of the modified cyanate ester monomer provided by the present invention is to carry out a substitution reaction of raw materials including bisphenol phenylphosphine oxide and cyanogen halide at low temperature to obtain a product system of (-)phenylphosphine oxide containing a cyanate group; through a simple acyl reaction, the (-OCN) structure and the structure of triphenylphosphine oxide are combined in one molecule, thereby preparing a modified cyanate ester monomer that can participate in the cyanate ester curing reaction. Specifically, the bisphenol phenylphosphine oxide is dissolved in acetone under a nitrogen environment, and the reaction temperature is maintained at -20°C to -10°C to reduce the poor effect caused by excessive intensity and absorption of reaction heat in the subsequent reaction process. Thereafter, the cyanogen halide is added to the bisphenol phenylphosphine oxide under mechanical stirring. During this process, the cyanate ester monomer begins to form, which can further react with any phenol to form imidocarbonate. In order to suppress this side reaction, the reaction temperature is optimized as described above to effectively reduce impurities. The organic base is then slowly added dropwise, and the reaction temperature is adjusted to room temperature after the reaction is completed in 3 to 5 hours. More preferably, in order to improve the purity of the obtained monomer, the reaction mixture is filtered to separate the salt, and the solvent is removed by vacuum to finally obtain a solid product.

[0030] Furthermore, in the preparation process of the above-mentioned modified monomer, in order to improve the modification effect and yield, and at the same time improve the purity of the obtained modified cyanate ester monomer, so as to enhance the flame retardant effect of the final cyanate ester resin, the inventors have preferably selected, through a large number of experiments, a molar ratio of cyanogen halide to bisphenol phenylphosphine oxide of (1.8 to 2.2):1; and / or a molar ratio of organic base to cyanogen halide of (1.8 to 2):1; preferably, the cyanogen halide is selected from one or more of cyanogen fluoride, cyanogen chloride and cyanogen bromide; preferably, the organic base is selected from one or more of triethylamine, diethylamine, trimethylamine and N,N-dimethylphenethylamine.

[0031] In several typical embodiments, in order to comprehensively optimize the mechanical properties and heat resistance of the obtained resin composition after curing, the weight ratio of the cyanate ester monomer, the modified cyanate ester monomer and the epoxy resin is 100:(2-20):(2-20).

[0032] In the process of forming the resin composition, the inventors, after extensive experiments, preferably determine that in step S1, the temperature of the first mixing is 90°C to 130°C, so that the modified cyanate ester monomer and the unmodified cyanate ester monomer can be mixed more evenly. And / or, to achieve a better prepolymerization effect, the temperature of the polymerization reaction in step S2 is preferably 150°C to 180°C. And / or, the temperature of the second mixing in step S3 is preferably 90°C to 130°C, so that the obtained prepolymer and epoxy resin are mixed more evenly, thereby improving the subsequent curing effect. And more preferably, the time for the first mixing, polymerization reaction, and second mixing is each independently 0.1h to 2h.

[0033] In several typical embodiments, the cyanate monomer is selected from one or more of bisphenol A cyanate, tetramethyl bisphenol F cyanate, bisphenol E cyanate, bisphenol M cyanate, 4,4'-oxybisphenyl cyanate, bis(4-cyanate)sulfane, and 4,4'-(1,3-hexafluoropropane-2,2-substituted)bisphenyl cyanate. The structure of each cyanate is:

[0034] Bisphenol A cyanate:

[0035] Tetramethyl bisphenol F cyanate:

[0036] Bisphenol E cyanate:

[0037] Bisphenol M cyanate:

[0038] 4,4'-oxybis(phenylcyanate):

[0039] Bis(4-cyanate)sulfane:

[0040] 4,4'-(1,3-hexafluoropropane-2,2-substituted)bis(phenylcyanate):

[0041] After extensive experiments, the inventors have optimized the above-mentioned cyanate ester monomers so as to better cooperate with the modified cyanate ester monomers and significantly improve the various properties of the resulting cyanate ester resin composition after curing.

[0042] Furthermore, the epoxy resin is selected from one or more of bisphenol A epoxy resin E-51, bisphenol A epoxy resin E-54, bisphenol A epoxy resin E-44, novolac epoxy resin E-44, novolac epoxy resin E-46, and bisphenol S epoxy resin. Cyanate esters and epoxy resins are difficult to undergo a curing reaction alone without a catalyst and a curing agent. However, when a mixture of cyanate esters and the aforementioned epoxy resins, which the inventors have selected through extensive experiments, is used to perform a curing reaction, a small amount of cyanate ester can promote the curing reaction of the epoxy resin, while an even smaller amount of epoxy resin can also promote the curing reaction of the cyanate ester. In other words, when the cyanate ester prepolymer and the epoxy resin undergo a curing reaction, the aforementioned epoxy resin and the resulting modified cyanate ester prepolymer have a more significant mutual catalytic effect, thereby further improving the overall performance of the resulting cyanate ester resin after curing.

[0043] A second aspect of the present invention provides a cyanate ester resin composition, which is prepared by the above-mentioned method for preparing a cyanate ester resin composition. The obtained cyanate ester resin composition has good stability and thermal properties, and has lower activation energy during curing.

[0044] The third aspect of the present invention provides a flame retardant resin, which is obtained by vacuum degassing and heat curing the above resin composition in sequence. The polymer resin obtained by curing the above resin composition contains a regular triazine ring structure, which makes the polymer resin have good thermal and mechanical properties, and has excellent oxidative stability and a high glass transition temperature. The addition of phosphorus-containing groups gives the cyanate ester resin flame retardant properties. At the same time, the electron-withdrawing P=O group catalyzes the triazine ring formation of the cyanate group, so that the curing activation energy of the resin is reduced, and the curing temperature moves toward low temperature, thereby lowering the curing temperature.

[0045] Furthermore, in order to optimize the structural continuity of the obtained cyanate ester resin and improve its various properties, the vacuum defoaming temperature is preferably 80° C. to 100° C. and the time is 1 h to 3 h.

[0046] In several typical embodiments, thermal curing includes a first-stage curing, a second-stage curing, and a third-stage curing performed sequentially to improve the mechanical and thermal properties of the resulting resin based on reaction kinetics. In several more typical embodiments, the temperature of the first stage curing is 110°C to 150°C, and the time is 1h to 3h; the temperature of the second stage curing is 150°C to 210°C, and the time is 1h to 4h; the temperature of the third stage curing is 190°C to 250°C, and the time is 2h to 6h. After a large number of experiments, the inventors have optimized the process conditions of the above three-stage thermal curing, thereby further improving production efficiency, while eliminating the thermal stress of the resin during the thermal curing process, and improving its various performances.

[0047] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0048] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0049] Example 1

[0050] A method for preparing a flame retardant resin:

[0051] 1. Preparation of modified cyanate monomer: 49.4 g of bis(4,4-p-oxyphenol)triphenylphosphine oxide was dissolved in 500 ml of acetone under a nitrogen atmosphere, and the reaction temperature was maintained at -20°C; 21.6 g of cyanogen bromide was added to the solution (the molar ratio of cyanogen bromide to bis(4,4-p-oxyphenol)triphenylphosphine oxide was 2.12:1), and the mixture was stirred with a mechanical stirrer, and the temperature was maintained during the reaction; 40.5 g of triethylamine was slowly added dropwise (the molar ratio of triethylamine to the previously added cyanogen bromide was 1.99:1), and the reaction temperature was adjusted to room temperature after 4 hours; the reaction mixture was filtered to separate the salt, and the solvent was removed by vacuum to obtain a solid product.

[0052] 2. Preparation of a cyanate ester resin composition: 100 g of bisphenol A cyanate ester monomer and 10 g of the modified cyanate ester monomer obtained above were heated and melted at 100°C with stirring for 30 minutes. The temperature was then raised to 160°C and reacted for 1 hour to obtain a modified cyanate ester resin prepolymer. Subsequently, 10 g of bisphenol A epoxy resin E-51 was added at 100°C and heated with stirring for 30 minutes to obtain a modified cyanate ester resin mixture.

[0053] 3. Curing to obtain flame retardant resin: Pour the modified cyanate ester mixture into the mold, remove bubbles in vacuum at 90℃ for 3h, and cure the modified cyanate ester resin mixture according to the curing process of 120℃ / 2h+200℃ / 2h+240℃ / 3h. After complete curing, the flame retardant resin is obtained. Its infrared spectrum is shown in Figure 1 shown.

[0054] Example 2

[0055] A method for preparing a flame retardant resin:

[0056] The only difference between this embodiment and embodiment 1 is that in the preparation of the cyanate ester resin composition, the mass of the modified cyanate ester monomer is 15 g instead of 10 g, that is, the weight ratio of the cyanate ester monomer, the modified cyanate ester monomer and the epoxy resin is 100:15:10.

[0057] Example 3

[0058] A method for preparing a flame retardant resin:

[0059] The only difference between this embodiment and embodiment 1 is that in the preparation of the cyanate ester resin composition, the mass of the bisphenol A epoxy resin E-51 is 20 g instead of 10 g, that is, the weight ratio of the cyanate ester monomer to the modified cyanate ester monomer is 100:10:20.

[0060] Example 4

[0061] A method for preparing a flame retardant resin:

[0062] This example differs from Example 1 only in that the temperature and time conditions in each step of preparing the cyanate ester resin composition are different. Specifically, 100 g of bisphenol A cyanate ester monomer and 10 g of modified cyanate ester monomer were melted and stirred at 120°C for 20 minutes. The temperature was then raised to 180°C and allowed to react for 0.5 hours to obtain a modified cyanate ester resin prepolymer. Subsequently, 10 g of bisphenol A epoxy resin E-51 was added at 120°C and heated and stirred for 20 minutes to obtain a modified cyanate ester resin mixture.

[0063] Example 5

[0064] A method for preparing a flame retardant resin:

[0065] The only difference between this embodiment and embodiment 1 is that the thermal curing process is different during the curing process to obtain the flame retardant resin. Specifically, the thermal curing process of this embodiment is: 130°C / 2h+190°C / 3h+220°C / 4h.

[0066] Example 6

[0067] A method for preparing a flame retardant resin:

[0068] The only difference between this embodiment and embodiment 1 is that the vacuum degassing conditions are different during the curing process to obtain the flame retardant resin. Specifically, the vacuum degassing conditions of this embodiment are: 100° C., 1 h.

[0069] Example 7

[0070] A method for preparing a flame retardant resin:

[0071] The only difference between this embodiment and embodiment 1 is that in the preparation of the cyanate ester resin composition, the bisphenol A epoxy resin E-51 is replaced by an equal weight of novolac epoxy resin E-46.

[0072] Example 8

[0073] A method for preparing a flame retardant resin:

[0074] The only difference between this embodiment and embodiment 1 is that in the preparation of the cyanate ester resin composition, the bisphenol A cyanate ester monomer is replaced by an equal weight of tetramethyl bisphenol F cyanate ester monomer.

[0075] Example 9

[0076] A method for preparing a flame retardant resin:

[0077] The only difference between this embodiment and embodiment 1 is that in the preparation of the cyanate ester resin composition, 100 g of bisphenol A cyanate monomer is replaced with 50 g of tetramethyl bisphenol F cyanate monomer and 50 g of bisphenol A cyanate monomer; and 10 g of bisphenol A epoxy resin E-51 is replaced with 5 g of novolac epoxy resin E-46 and 5 g of bisphenol A epoxy resin E-51.

[0078] Example 10

[0079] A method for preparing a flame retardant resin:

[0080] The only difference between this embodiment and embodiment 1 is that a cyanate ester monomer having the following structure is selected to replace the modified cyanate ester monomer in embodiment 1. The cyanate ester monomer also contains a phenyl group and a phosphine group.

[0081]

[0082] The instability of this structure makes it easy for side reactions to occur during the preparation process and subsequent polymerization.

[0083] Example 11

[0084] A method for preparing a flame retardant resin:

[0085] This example differs from Example 1 only in that the temperature and time conditions in each step of preparing the cyanate ester resin composition are different. Specifically, 100 g of bisphenol A cyanate ester monomer and 10 g of the modified cyanate ester monomer obtained above were heated, melted, and stirred at 80°C for 30 minutes. The temperature was then raised to 185°C and allowed to react for 1 hour to obtain a modified cyanate ester resin prepolymer. Subsequently, 10 g of bisphenol A epoxy resin E-51 was added at 80°C, and the mixture was heated and stirred for 30 minutes to obtain a modified cyanate ester resin mixture.

[0086] Example 12

[0087] A method for preparing a flame retardant resin:

[0088] This example differs from Example 1 only in that the temperature and time conditions in each step of preparing the cyanate ester resin composition are different. Specifically, 100 g of bisphenol A cyanate ester monomer and 10 g of the modified cyanate ester monomer obtained above were heated to melt and stirred at 150°C for 30 minutes. The temperature was then raised to 130°C and allowed to react for 1 hour to obtain a modified cyanate ester resin prepolymer. Subsequently, 10 g of bisphenol A epoxy resin E-51 was added at 150°C and heated and stirred for 30 minutes to obtain a modified cyanate ester resin mixture.

[0089] Example 13

[0090] A method for preparing a flame retardant resin:

[0091] The only difference between this embodiment and Example 1 is that the process of curing to obtain the flame retardant resin is different. Specifically, the modified cyanate ester mixture is poured into a mold, vacuum defoamed at 70°C for 4 hours, and cured according to a curing process of 100°C / 4 hours + 230°C / 0.5 hours + 180°C / 7 hours to obtain the flame retardant resin after complete curing.

[0092] Example 14

[0093] A method for preparing a flame retardant resin:

[0094] The only difference between this embodiment and Example 1 is that the process of curing to obtain the flame retardant resin is different. Specifically, the modified cyanate ester mixture is poured into a mold, vacuum defoamed at 160°C for 0.5h, and cured according to a curing process of 160°C / 0.5h+140°C / 5h+260°C1h to obtain the flame retardant resin after complete curing.

[0095] Comparative Example 1

[0096] A method for preparing a flame retardant resin:

[0097] This comparative example differs from Example 1 only in the preparation method of the cyanate ester resin composition. Specifically, 110 g of a modified cyanate ester monomer was melted and stirred at 100°C for 30 minutes. The temperature was then raised to 160°C and the reaction was allowed to proceed for 1 hour to obtain a modified cyanate ester resin prepolymer. Subsequently, 10 g of bisphenol A epoxy resin E-51 was added at 100°C and heated and stirred for 30 minutes to obtain a modified cyanate ester resin mixture.

[0098] That is, no cyanate monomer is added.

[0099] Comparative Example 2

[0100] A method for preparing a flame retardant resin:

[0101] The only difference between this comparative example and Example 1 is that the preparation method of the cyanate ester resin composition is different. Specifically, 100 g of bisphenol A cyanate ester monomer and 10 g of modified cyanate ester monomer are heated, melted and stirred at 100° C. for 30 minutes, the temperature is raised to 160° C., and the reaction is carried out for 1 hour to obtain a modified cyanate ester resin prepolymer, which is directly used as a modified cyanate ester resin mixture.

[0102] That is, no epoxy resin was added.

[0103] Comparative Example 3

[0104] A method for preparing a flame retardant resin:

[0105] This comparative example differs from Example 1 only in the preparation method of the cyanate ester resin composition. Specifically, 100 g of bisphenol A cyanate ester monomer and 10 g of bisphenol phenylphosphine oxide were heated and melted at 100°C with stirring for 30 minutes. The temperature was then raised to 160°C and reacted for 1 hour to obtain a modified cyanate ester resin prepolymer. Subsequently, 10 g of bisphenol A epoxy resin E-51 was added at 100°C and heated and stirred for 30 minutes to obtain a modified cyanate ester resin mixture.

[0106] That is, instead of pre-preparing a modified cyanate ester monomer, the modified bisphenol phenylphosphine oxide, used as a flame retardant, is directly mixed with the cyanate ester monomer and pre-polymerized. The resulting cured flame-retardant resin, while exhibiting good flame retardancy and glass transition temperature, and low dielectric loss, suffers from poor mechanical properties, making it difficult to meet application requirements.

[0107] Comparative Example 4

[0108] A method for preparing a flame retardant resin:

[0109] The only difference between this comparative example and Example 1 is that the preparation method of the cyanate ester resin composition is different. Specifically, 100 g of bisphenol A cyanate ester monomer and 10 g of the modified cyanate ester monomer obtained above were heated, melted and stirred at 100° C. for 30 minutes, and 10 g of bisphenol A epoxy resin E-51 was directly added to the mixed system of the two at 100° C., and heated and stirred for 30 minutes to obtain a modified cyanate ester resin mixture.

[0110] That is, the modified cyanate ester monomer and the cyanate ester monomer are not formed into a prepolymer.

[0111] Test Method

[0112] Thermogravimetric analysis (TGA) is used to measure the mass change of a substance as temperature changes. It uses a thermogravimetric analyzer (TGA). In a TGA experiment, a sample is typically heated to a certain temperature range. By monitoring the change in mass, information about the sample's thermal decomposition, dehydration, oxidation, and other reaction processes can be obtained.

[0113] Limiting Oxygen Index: The limiting oxygen index refers to the volume fraction of oxygen in a polymer in a mixture of oxygen and nitrogen that is just sufficient to support combustion. Tested in accordance with GB / T 2406-93, Test Method for Combustion Performance of Plastics.

[0114] Dielectric constant: Prepare samples according to the dimensional requirements of the resonant cavity method specimens, and measure the dielectric constant of the laminate at 8-12 GHz according to GB / T 35679.

[0115] Dielectric loss: measured using an AET microwave (high frequency) dielectric constant tester.

[0116] Tensile strength: tested in accordance with GB / T 2567-2021 Test method for properties of resin castings.

[0117] Elongation at break: Tested in accordance with GB / T 2567-2021 Test method for properties of resin castings.

[0118] The cured flame retardant resins obtained in each embodiment and comparative example were prepared into sizes as follows:

[0119] Thermal weight loss temperature: 2~5mg;

[0120] Limiting oxygen index: 80mm*10mm*4mm;

[0121] Dielectric constant, dielectric loss: 22.86mm*10.16mm, thickness: 2.5±0.5mm;

[0122] Tensile strength and elongation at break: Sample strips with a middle parallel section length and width of 60 mm*10±0.2 mm and a thickness of 4±0.2 mm were subjected to the above tests. The results are shown in Table 1.

[0123] Table 1

[0124]

[0125] From the above description, it can be seen that the cyanate ester resin prepared in the above-mentioned embodiment of the present invention contains the structure of triphenylphosphine oxide. When it is in a cyanate ester-epoxy compound system, due to the unique polymerization activity of the cyanate ester resin, the polymerized resin not only has excellent processing properties, good thermal properties and mechanical properties, but also has excellent oxidative stability, flame retardancy and a high glass transition temperature.

[0126] Specifically, the addition of the modified cyanate ester monomer effectively improves the flame retardancy and thermal weight loss temperature of the cyanate ester resin. At the same time, the unique structure of the cyanate ester resin maintains the low dielectric constant and low dielectric loss of the original resin. Due to the aromatic ether connection structure of the modified cyanate ester monomer, the tensile strength and elongation at break are slightly increased.

[0127] It should be noted that the terms "first," "second," and the like in the specification and claims of this application are used to distinguish similar objects, and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the application described herein can, for example, be implemented in an order other than that described herein.

[0128] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a cyanate ester resin composition, characterized in that: The preparation method comprises: Step S1, first mixing a cyanate ester monomer and a modified cyanate ester monomer to obtain a mixed monomer; Step S2, the mixed monomers are subjected to polymerization reaction to obtain a prepolymer; Step S3, performing a second mixing of the prepolymer and the epoxy resin to obtain the cyanate ester resin composition; The structure of the modified cyanate ester monomer includes a phosphine group and a phenyl group.

2. The method for preparing a cyanate ester resin composition according to claim 1, wherein The modified cyanate ester monomer has a structure shown in Formula I:

3. The method for preparing the cyanate ester resin composition according to claim 1 or 2, wherein: The preparation method of the modified cyanate ester monomer comprises: adding cyanogen halide and bisphenol phenylphosphine oxide into a solvent and mixing them to obtain a mixed solution; adding an organic base to the mixed solution to react and obtain the modified cyanate ester monomer; The bisphenol phenylphosphine oxide has a structure shown in Formula II:

4. The method for preparing the cyanate ester resin composition according to claim 3, wherein The molar ratio of the cyanogen halide to the bisphenol phenylphosphine oxide is (1.8-2.2):1; and / or the molar ratio of the organic base to the cyanogen halide is (1.8-2):1; Preferably, the cyanogen halide is selected from one or more of cyanogen fluoride, cyanogen chloride and cyanogen bromide; Preferably, the organic base is selected from one or more of triethylamine, diethylamine, trimethylamine and N,N-dimethylphenethylamine.

5. The method for preparing a cyanate ester resin composition according to any one of claims 1 to 4, characterized in that: The weight ratio of the cyanate monomer, the modified cyanate monomer and the epoxy resin is 100:(2-20):(2-20).

6. The method for preparing a cyanate ester resin composition according to any one of claims 1 to 5, characterized in that: In step S1, the temperature of the first mixing is 90°C to 130°C; and / or, In step S2, the polymerization reaction temperature is 150° C. to 180° C.; and / or, In step S3, the temperature of the second mixing is 90°C to 130°C; Preferably, the time for the first mixing, the polymerization reaction and the second mixing is independently 0.1 h to 2 h.

7. The method for preparing a cyanate ester resin composition according to any one of claims 1 to 6, characterized in that: The cyanate monomer is selected from one or more of bisphenol A cyanate, tetramethyl bisphenol F cyanate, bisphenol E cyanate, bisphenol M cyanate, 4,4'-oxybisphenyl cyanate, bis(4-cyanate)sulfane and 4,4'-(1,3-hexafluoropropane-2,2-substituted)bisphenyl cyanate.

8. The method for preparing a cyanate ester resin composition according to any one of claims 1 to 7, characterized in that: The epoxy resin is selected from one or more of bisphenol A epoxy resin E-51, bisphenol A epoxy resin E-54, bisphenol A epoxy resin E-44, novolac epoxy resin E-44, novolac epoxy resin E-46 and bisphenol S epoxy resin.

9. A cyanate resin composition, characterized in that The cyanate ester resin composition is prepared by the preparation method of the cyanate ester resin composition according to any one of claims 1 to 8.

10. A flame retardant resin, characterized in that: The flame retardant resin is obtained by sequentially subjecting the cyanate resin composition according to claim 9 to vacuum degassing and thermal curing; Preferably, the vacuum degassing temperature is 80°C to 100°C, and the time is 1h to 3h; Preferably, the thermal curing includes one-stage curing, two-stage curing and three-stage curing performed sequentially; More preferably, the temperature of the first stage curing is 110°C to 150°C, and the time is 1h to 3h; the temperature of the second stage curing is 150°C to 210°C, and the time is 1h to 4h; the temperature of the third stage curing is 190°C to 250°C, and the time is 2h to 6h.

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