Low-dielectric phosphorus-nitrogen synergistic flame retardant as well as preparation method and application thereof

Abstract

The invention discloses a low-dielectric phosphorus-nitrogen synergistic flame retardant as well as a preparation method and application thereof. The structural general formula of the low-dielectric phosphorus-nitrogen synergistic flame retardant provided by the invention is as shown in formula I: # imgabs0. The low-dielectric phosphorus-nitrogen synergistic flame retardant is a novel phosphorus-nitrogen-containing low-dielectric compound prepared by carrying out addition reaction on an organic phosphorus compound containing a P-H bond and a compound containing an isocyanate group. The compound has the characteristics of low dielectric constant, low dielectric loss and inhibition of dielectric property degradation of resin. Through a P-C-N direct-connected saturated covalent bond in a molecular structure, the bond energy of the covalent bond is relatively high, and the polarization effect is relatively weak, so that the compound has a lower dielectric constant and lower dielectric loss; meanwhile, the dielectric property degradation of the resin is inhibited through the synergistic effect of-NH-C = O and P = O; phosphorus and nitrogen elements in the molecular structure of the compound not only can independently play a flame-retardant role, but also can play a synergistic role at the same time, so that a common polymer material is endowed with excellent flame-retardant performance.

Description

Technical Field

[0001] The present invention belongs to the field of functional flame retardants, and particularly relates to a low-dielectric phosphorus-nitrogen synergistic flame retardant, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid popularization of 5G and 6G high-frequency and high-speed devices, the heat generated by electronic components during operation has increased significantly, and they are in a relatively high-temperature environment for a long time, which poses more stringent requirements on the comprehensive performance of packaging materials. Specifically, packaging materials need to have properties such as ultra-low dielectric loss, low dielectric constant, high flame retardancy, low thermal expansion coefficient, and high modulus. However, existing material systems are difficult to meet these requirements simultaneously in specific applications, restricting the further improvement of the performance of high-frequency and high-speed electronic devices.

[0003] In terms of flame retardancy, most of the flame retardants widely used in the current electronic packaging field are bromine-containing systems. However, these flame retardants will release corrosive gases such as hydrogen bromide at high temperatures, which not only reduces the heat resistance of the materials but also may cause environmental pollution and health risks. For example, bromine-containing flame retardants may generate harmful substances such as dioxins and dibenzofurans during combustion, and these substances have been proven to have carcinogenic risks, so the use of bromine-containing flame retardants is being gradually restricted. At the same time, although some halogen-free flame retardants can avoid the environmental and health hazards brought by bromine-containing flame retardants, their own dielectric loss is relatively high, and the polar molecular structure has an adverse effect on the dielectric properties of the materials. In addition, the synthesis processes of some halogen-free flame retardants are complex and the manufacturing costs are relatively high, which further restricts their practical popularization and application in the field of electronic packaging.

[0004] In terms of dielectric properties, although some material systems (such as hydrocarbon resins and modified polyphenylene ether-based composites) exhibit low dielectric loss and good dielectric properties under initial conditions, during high-temperature or long-term use, the matrix of these materials often contains unreacted double bonds. These unreacted chemical structures are vulnerable to oxidation attacks, resulting in a significant increase in the dielectric constant and dielectric loss of the materials, thereby causing deterioration of the dielectric properties, manifested as problems such as increased power consumption, accelerated material aging, and shortened service life of electronic components. To alleviate the deterioration of dielectric properties caused by oxidation, some studies have attempted to inhibit the oxidation reaction by adding hindered amine or hindered phenol antioxidants. However, these antioxidants usually interfere with the free radical curing reaction of polymers, reducing the crosslinking density of the materials, and further increasing the number of unreacted double bonds, exacerbating the oxidation and dielectric property deterioration of the materials. Therefore, there is an urgent need to develop innovative methods that can effectively inhibit the deterioration of the dielectric properties of matrix materials.

[0005] In summary, there is currently no flame retardant product on the market that can provide both high flame retardancy and low dielectric loss characteristics, and can effectively inhibit the deterioration of the dielectric properties of the matrix material. Developing a phosphorus-nitrogen synergistic flame retardant with low dielectric properties and capable of synergistically inhibiting the deterioration of the dielectric properties of materials has become an important direction to solve the above technical problems. Summary of the Invention

[0006] In view of this, the present invention provides a low-dielectric phosphorus-nitrogen synergistic flame retardant, its preparation method and application, aiming to solve the above technical problems and meet the requirements of the high-frequency electronic packaging field for the environmental protection, high flame retardancy, low dielectric loss and inhibition of dielectric property deterioration of the flame retardant.

[0007] A low-dielectric phosphorus-nitrogen synergistic flame retardant provided by the first aspect of the present invention has a general structural formula as shown in Formula I:

[0008]

[0009] A preparation method of the low-dielectric phosphorus-nitrogen synergistic flame retardant according to Formula I provided by the second aspect of the present invention, wherein the low-dielectric phosphorus-nitrogen synergistic flame retardant is synthesized by reacting an isocyanate group-containing compound (R1-NCO) with an organophosphorus compound containing a P-H bond (R2R3P(O)H), and the synthesis general formula is as shown in Formula II:

[0010]

[0011] Further, the isocyanate group-containing compound is an isocyanate group-containing compound with an R1 group, and the R1 group is selected from any one of a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, an arylalkyl group, an alkylaryl group, a heteroarylalkyl group, an alkylheteroaryl group, a substituted alkyl group, a substituted cycloalkyl group, a substituted aryl group, a substituted heteroaryl group, a substituted arylalkyl group, a substituted alkylaryl group, a substituted heteroarylalkyl group, a substituted alkylheteroaryl group; the substitution includes hydrogen atom substitution, heteroatom substitution or co-substitution of hydrogen atom and heteroatom.

[0012] Further, the isocyanate group-containing compound is preferably a diisocyanate, and the isocyanate group-containing compound is selected from at least one of hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane-4,4'-diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate and dicyclohexylmethane 4,4-diisocyanate.

[0013] Further, R2 and R3 in the organophosphorus compound containing a P-H bond are selected from at least one of an oxygen-substituted alkyl group, a methyl group, an ethyl group, a phenyl group, a substituted or unsubstituted heteroaryl group.

[0014] Further, the organophosphorus compound containing a P-H bond is selected from at least one of dimethyl phosphite, diethyl phosphite, diphenyl phosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, ethyl phenylphosphonite, and diphenylphosphine oxide, and the corresponding structures are shown as follows:

[0015]

[0016] Further, the reaction synthesis process includes the following steps: dissolving the isocyanate group-containing compound and the organophosphorus compound containing a P-H bond in an organic solvent, adding a catalyst after complete dissolution, reacting under heating conditions, and after the reaction is completed, the reaction solution is filtered and centrifuged to remove the organic solvent and unreacted impurities, and then dried to obtain the low dielectric phosphorus-nitrogen synergistic flame retardant.

[0017] In the above method, the molar ratio of the isocyanate group-containing compound to the organophosphorus compound containing a P-H bond is 1:(1-3); the molar ratio of the isocyanate group-containing compound to the catalyst is 1:(0.01-0.1); the amount of the organic solvent used is 5 to 50 times the mass of the isocyanate group-containing compound; the organic solvent includes at least one of N,N-dimethylformamide, dimethyl sulfoxide, dichloromethane, chloroform, ethanol, acetone, methyl ethyl ketone, tetrahydrofuran, and toluene; the catalyst is selected from at least one of triethylamine, potassium tert-butoxide, sodium methoxide, and anhydrous potassium carbonate; the reaction time is 5h to 75h; the reaction temperature is 35°C to 115°C.

[0018] Further, removing the unreacted impurities includes the following steps: washing the product formed by the reaction with a washing agent, and the washing agent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, dichloromethane, chloroform, tetrahydrofuran, ethanol, ethyl acetate, petroleum ether, and ether.

[0019] The flame retardant material proposed in the third aspect of the present invention, which uses the low dielectric phosphorus-nitrogen synergistic flame retardant shown in Formula I as a flame retardant component, the flame retardant material is selected from at least one of a flame retardant thermoplastic engineering material, a flame retardant thermosetting resin composition, a flame retardant encapsulation material, a flame retardant adhesive, a flame retardant laminate, and a flame retardant fiber reinforced material.

[0020] Further, the flame retardant thermosetting resin composition is selected from a composition formed by mixing and curing at least one of a thermosetting polyphenylene ether resin, a hydrocarbon resin, an epoxy resin, a benzoxazine, a bismaleimide, a phenolic resin, and a polyurethane and the low dielectric phosphorus-nitrogen synergistic flame retardant.

[0021] The application of the flame retardant material proposed in the fourth aspect of the present invention in the field of electronic packaging includes using the aforementioned flame retardant material as at least one of a copper clad laminate, a packaging carrier board, and an epoxy molding compound.

[0022] The present invention adopts the above technical solutions to achieve the following technical effects: A novel low-dielectric phosphorus-nitrogen synergistic flame retardant is prepared by using the addition reaction of an isocyanate group-containing compound and an organophosphorus compound containing a P-H bond. This flame retardant has the advantages of low dielectric constant, ultra-low dielectric loss, excellent flame retardancy, inhibition of dielectric property deterioration, cheap raw materials, and simple preparation method. Based on the electronic packaging substrate with this low-dielectric phosphorus-nitrogen synergistic flame retardant, during long-term high-temperature use, it has excellent flame retardancy, low dielectric loss, good dielectric stability, high thermal stability, and excellent characteristics of resisting dielectric property deterioration.

[0023] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the disclosure of the embodiments of the present invention. Brief Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained as these drawings.

[0025] Figure 1 It is the infrared spectrum schematic diagram of each substance when the reactants of the present invention are hexamethylene diisocyanate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and the product is the low-dielectric phosphorus-nitrogen synergistic flame retardant DH.

[0026] Figure 2 It is the 1H NMR spectrum of the low-dielectric phosphorus-nitrogen synergistic flame retardant DH of the present invention.

[0027] Figure 3 It is the aging test data graph of Examples 8-14 and Comparative Examples 1-3 of the present invention. Detailed Embodiments

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, other embodiments obtained by those of ordinary skill in the art without creative efforts all belong to the scope of protection of the present invention.

[0029] Using materials with low dielectric constants can improve the signal transmission speed of the materials, reduce the energy loss during signal propagation, thereby reducing the power consumption and heat generation of electronic components, and can also reduce the phase delay and distortion of signals during transmission, improving the integrity and accuracy of signal transmission. Especially when high-frequency and high-speed electronic components are operating, using electronic packaging materials with low dielectric constants and low dielectric losses can improve the heat dissipation effect of electronic components, and can also improve the protection performance of electronic components, enhancing the thermal stability and insulation performance of electronic components.

[0030] In view of this, the present invention aims to propose a low-dielectric phosphorus-nitrogen synergistic flame retardant with low dielectric properties, low dielectric loss, and high flame retardancy, so as to be used in combination with a resin matrix to form a flame-retardant material, and further used in electronic packaging, especially in high-frequency and high-speed electronic packaging, to enhance the thermal stability of the final packaging material, making the packaged components have high flame retardancy, low dielectric loss performance, and resistance to dielectric performance deterioration.

[0031] Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0032] A low-dielectric phosphorus-nitrogen synergistic flame retardant proposed by the present invention has a structural general formula as shown in Formula I:

[0033]

[0034] As can be seen from the above, from the above technical solutions, the low-dielectric phosphorus-nitrogen synergistic flame retardant proposed by the present invention has a covalent bond with a direct connection of P-C-N in its structure. The bond energy of each covalent bond in the whole structure is relatively high, and the polarity is relatively low, and the polarization effect is relatively weak. The low polarization characteristic makes the low-dielectric phosphorus-nitrogen synergistic flame retardant of the present invention have a lower dielectric constant and a lower dielectric loss. In addition, the main functional elements of the low-dielectric phosphorus-nitrogen synergistic flame retardant of the present invention do not contain bromine, and no toxic gas is released during the high-temperature decomposition process, and the environmental performance is good.

[0035] Also, because the P-C structural bond energy of the low-dielectric phosphorus-nitrogen synergistic flame retardant of the present invention is high and it decomposes slowly at high temperatures, and C can form a dense carbon layer after burning at high temperatures, and the carbon layer has good high-temperature resistance, therefore, the low-dielectric phosphorus-nitrogen synergistic flame retardant of the present invention has good thermal stability and a low thermal decomposition rate.

[0036] When the C-N bond in P-C-N breaks at high temperatures, nitrogen can be released, thereby diluting oxygen, making the low-dielectric phosphorus-nitrogen synergistic flame retardant of the present invention have good oxygen isolation performance and good flame retardant effect. In the present invention, P and N act synergistically to provide more excellent dielectric stability and flame retardant effect.

[0037] It is understandable that, compared with the bromine-containing flame retardants in the prior art, the low-dielectric phosphorus-nitrogen synergistic flame retardant of formula I in the present invention is not easily decomposed during long-term operation at high temperatures; it can also release nitrogen during the flame retardant process to reduce the oxygen content, and does not release corrosive gases such as hydrogen bromide or harmful substances such as dioxins, and has good environmental performance.

[0038] When traditional thermosetting resins based on double-bond free radical crosslinking are used as encapsulation materials, the dielectric constant and dielectric loss often increase significantly after high-temperature or long-term use, resulting in deterioration of dielectric properties and increased power consumption, thus limiting their application in the field of high-performance encapsulation. However, the low-dielectric phosphorus-nitrogen synergistic flame retardant with the structure of formula I in the present invention exhibits excellent thermal stability and a low thermal decomposition rate during high-temperature or long-term use. When this flame retardant is used in high-frequency encapsulation materials, it can significantly inhibit the deterioration of dielectric properties and exhibit excellent anti-aging performance, providing a more reliable solution for encapsulation materials in high-frequency and high-temperature environments.

[0039] Compared with the low-dielectric flame retardants with a structure having a stronger polarization effect in the prior art, the low-dielectric phosphorus-nitrogen synergistic flame retardant with a direct P-C-N connection in the present invention has a lower polarity, is not easily affected by the polarization effect, has good electrical insulation performance, a low dielectric constant, and relatively high structural stability.

[0040] The low-dielectric phosphorus-nitrogen synergistic flame retardant containing a P-C-N structure in the present invention is not only applicable to traditional free radical crosslinked thermosetting resin systems, but can also be extended to other polymer systems that require long-term stable dielectric properties, including various thermosetting resins and thermoplastic resins, and can effectively inhibit the deterioration of the dielectric properties of the resin.

[0041] Next, the preparation method of the low-dielectric phosphorus-nitrogen synergistic flame retardant in the foregoing examples of the present invention will be described.

[0042] According to the preparation method of the low-dielectric phosphorus-nitrogen synergistic flame retardant provided by the present invention, the low-dielectric phosphorus-nitrogen synergistic flame retardant is synthesized by reacting an isocyanate group-containing compound with an organophosphorus compound containing a P-H bond. That is to say, the C-N structure in the low-dielectric phosphorus-nitrogen synergistic flame retardant of formula I in the present invention is provided by the isocyanate group-containing compound, and the part with P=O in the present invention is provided by the organophosphorus compound containing a P-H bond. The C=N double bond of the isocyanate group-containing compound is opened, and the H on the P in the organophosphorus compound containing a P-H bond is transferred to the vicinity of the N of the isocyanate group-containing compound, and a covalent bond is formed between C and P.

[0043] The synthesis general formula of the isocyanate group-containing compound and the organophosphorus compound containing a P-H bond in the present invention is represented as formula II below:

[0044]

[0045] Among them, the isocyanate group-containing compound is an isocyanate group-containing compound having an R1 group, and the R1 group is selected from any one of a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, an arylalkyl group, an alkylaryl group, a heteroarylalkyl group, an alkylheteroaryl group, a substituted alkyl group, a substituted cycloalkyl group, a substituted aryl group, a substituted heteroaryl group, a substituted arylalkyl group, a substituted alkylaryl group, a substituted heteroarylalkyl group, and a substituted alkylheteroaryl group; wherein the substitution includes hydrogen atom substitution, heteroatom substitution, or co-substitution of a hydrogen atom and a heteroatom. Substituted products containing an isocyanate group in the substituent are preferred.

[0046] R2 and R3 in the organophosphorus compound containing a P-H bond are each independently selected from at least one of an oxygen-substituted alkyl group, a methyl group, an ethyl group, a phenyl group, and a substituted or unsubstituted heteroaryl group. Substituted products containing a benzene ring in the substituent are preferred.

[0047] It can be understood that for the preparation method of the low-dielectric phosphorus-nitrogen synergistic flame retardant proposed by the present invention, the preparation steps only require one step, the reactants required for the preparation are relatively simple, and the synthesis operation is easy to carry out.

[0048] In some embodiments of the present invention, the isocyanate group-containing compound (R1-N=C=O) is selected from at least one of hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane-4,4'-diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, and dicyclohexylmethane 4,4-diisocyanate. Among these substances, hexamethylene diisocyanate (also known as HDI) is usually a liquid. It has an isocyanate group at each end of its molecular chain, and the two isocyanate groups are connected by a hydrocarbon chain. Then, when polymerized with an organophosphorus compound containing a P-H bond, R1 on the low-dielectric phosphazene synergistic flame retardant is (-CH2-)6. Toluene diisocyanate (also known as TDI) is soluble in solvents such as acetone, ethyl acetate, and toluene. Its methylbenzene ring contains two molecules of isocyanate groups. Then, when polymerized with an organophosphorus compound containing a P-H bond, R1 on the low-dielectric phosphazene synergistic flame retardant is a phenyl group substituted by a methyl group. Diphenylmethane-4,4'-diisocyanate is soluble in benzene, toluene, chlorobenzene, nitrobenzene, acetone, ether, ethyl acetate, dioxane, etc. Each of the two benzene rings in its molecule is connected with an isocyanate group. Then, when polymerized with an organophosphorus compound containing a P-H bond, R1 on the low-dielectric phosphazene synergistic flame retardant is two phenyl groups connected by a methylene group. p-Phenylene diisocyanate (also known as PPDI) has an isocyanate group on each of the 1st and 4th Cs of its benzene ring. Then, when polymerized with an organophosphorus compound containing a P-H bond, R1 on the low-dielectric phosphazene synergistic flame retardant is a phenyl group. m-Phenylene diisocyanate has an isocyanate group on each of the 1st and 3rd Cs of its benzene ring. Then, when polymerized with an organophosphorus compound containing a P-H bond, R1 on the low-dielectric phosphazene synergistic flame retardant is a phenyl group. Dicyclohexylmethane 4,4-diisocyanate (also known as HMDI) has an isocyanate group on each of the two cycloalkyl groups connected by a methylene group. Then, when polymerized with an organophosphorus compound containing a P-H bond, R1 on the low-dielectric phosphazene synergistic flame retardant is two cyclohexyl groups connected by a methylene group. The low-dielectric phosphazene synergistic flame retardant of the present invention can be prepared by different types of isocyanate group-containing compounds with R1 groups, has strong adaptability, and can be flexibly applied to the improvement of the flame retardancy and dielectric properties of various polymer matrices.

[0049] It should be noted that the isocyanate group-containing compound of the present invention is not limited to the above compounds. Any compound that contains an isocyanate group, conforms to the types of substituents of R1 in the present invention, and can react with an organophosphorus compound containing a P-H bond should be within the protection scope of the present invention.

[0050] In some embodiments of the present invention, the organophosphorus compound containing a P-H bond is selected from at least one of dimethyl phosphite, diethyl phosphite, diphenyl phosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, ethyl phenylphosphonite, and diphenylphosphine oxide. Dimethyl phosphite and diphenyl phosphite are soluble in most organic solvents; diethyl phosphite is soluble in organic solvents such as alcohols and ethers; 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (also known as DOPO) is readily soluble in methanol, ethanol, chloroform, dimethylformamide, and dioxane; it is soluble in benzene; it is insoluble in water and hexane. Ethyl phenylphosphonite is soluble in many organic solvents such as ethers, alcohols, and ketones, but insoluble in water. Diphenylphosphine oxide is soluble in polar organic solvents such as alcohols, dimethylformamide, and dichloromethane. When dimethyl phosphite is polymerized with an isocyanate group-containing compound, both R2 and R3 on the low-dielectric phosphorus-nitrogen synergistic flame retardant are -O-CH3. When diethyl phosphite is polymerized with an isocyanate group-containing compound, both R2 and R3 on the low-dielectric phosphorus-nitrogen synergistic flame retardant are -O-CH2-CH3. When diphenyl phosphite is polymerized with an isocyanate group-containing compound, both R2 and R3 on the low-dielectric phosphorus-nitrogen synergistic flame retardant are phenyl groups connected to O. When 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is polymerized with an isocyanate group-containing compound, R2 and R3 on the low-dielectric phosphorus-nitrogen synergistic flame retardant together are a 9-oxaphenanthrene group. When ethyl phenylphosphonite is polymerized with an isocyanate group-containing compound, R2 and R3 on the low-dielectric phosphorus-nitrogen synergistic flame retardant are phenyl and -O-CH3 respectively; when diphenylphosphine oxide is polymerized with an isocyanate group-containing compound, both R2 and R3 on the low-dielectric phosphorus-nitrogen synergistic flame retardant are phenyl groups. The structural formulas of the above organophosphorus compounds containing a P-H bond are specifically shown as follows:

[0051]

[0052] It should be noted that the organophosphorus compound containing a P-H bond of the present invention may not be limited to the above several compounds. As long as it contains O=P-H and conforms to the types of R2 and R3 of the present invention and can react with an isocyanate group-containing compound, it should be within the protection scope of the present invention.

[0053] According to the preparation method of the low-dielectric phosphorus-nitrogen synergistic flame retardant of each of the foregoing examples proposed by the present invention, it includes the following steps: Dissolve the isocyanate group-containing compound and the organophosphorus compound containing a P-H bond in an organic solvent. After complete dissolution, add a catalyst and carry out the reaction under heating conditions. After the reaction is completed, the reaction solution is filtered and centrifuged to remove the organic solvent and unreacted impurities, and then dried to obtain the low-dielectric phosphorus-nitrogen synergistic flame retardant.

[0054] In some embodiments of the present invention, the molar ratio of the isocyanate group-containing compound to the organophosphorus compound containing a P-H bond depends on the content of isocyanate groups in the isocyanate group-containing compound, ensuring that the molar ratio of isocyanate groups to P-H bonds is 1:1. Then, the molar ratio of the isocyanate group-containing compound to the organophosphorus compound containing a P-H bond is usually 1:(1-3). For example, in specific examples, the molar ratio of the isocyanate group-containing compound to the organophosphorus compound containing a P-H bond is 1:1, 1:2, 1:3, etc. When the molar ratio of the two reactants is within the above range, the isocyanate group can fully react with P-H to form a covalent bond with a relatively high bond energy of C-N-P direct connection, and the polarization effect is relatively weak, so that the low-dielectric phosphorus-nitrogen synergistic flame retardant of the present invention has a lower dielectric constant and a lower dielectric loss.

[0055] For the isocyanate group-containing compound and the organophosphorus compound containing a P-H bond with a molar ratio of 1:1, phenyl isocyanate and dimethyl phosphite can be selected; for the isocyanate group-containing compound and the organophosphorus compound containing a P-H bond with a molar ratio of 1:3, triphenylmethane triisocyanate and diphenylphosphine oxide can be selected; for the isocyanate group-containing compound and the organophosphorus compound containing a P-H bond with a molar ratio of 1:2, p-phenylene diisocyanate and diethyl phosphite can be selected. In the present invention, the isocyanate group-containing compound and the organophosphorus compound containing a P-H bond with a molar ratio of 1:2 are mainly selected, that is, an isocyanate group-containing compound containing two isocyanate groups is used. The isocyanate group-containing compound (R1-N=C=O) can specifically be at least one of the aforementioned hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane-4,4'-diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, and dicyclohexylmethane 4,4-diisocyanate. By synthesizing with the above diisocyanate group-containing compound and the organophosphorus compound containing a P-H bond, the finally generated low-dielectric phosphorus-nitrogen synergistic flame retardant will retain the symmetric structure in the diisocyanate group-containing compound, which is beneficial to further reducing the dielectric loss of the molecular structure of the low-dielectric phosphorus-nitrogen synergistic flame retardant and improving the dielectric performance.

[0056] In some embodiments of the present invention, the molar ratio of the isocyanate group-containing compound to the catalyst is 1:(0.01-0.1). By adding an appropriate proportion of the catalyst, the reaction rate of the two reactants can be effectively increased, the activation energy required for the reaction can be reduced, so as to effectively shorten the reaction time required and improve the preparation efficiency of the low-dielectric phosphorus-nitrogen synergistic flame retardant. For example, in specific examples, the molar ratio of the isocyanate group-containing compound to the catalyst is 1:0.01, 1:0.02, 1:0.03, 1:0.05, 1:0.08, 1:0.1, etc. For example, in a further example, 1:0.01 to 1:0.05 is selected.

[0057] In some examples of the present invention, the catalyst is selected from at least one of triethylamine, potassium tert-butoxide, sodium methoxide, and anhydrous potassium carbonate, and the type of catalyst required can be selected according to the actual situation.

[0058] In some embodiments of the present invention, the amount of the organic solvent is 5 to 50 times the mass of the isocyanate group-containing compound. By adding an appropriate organic solvent, not only can the isocyanate group-containing compound and the organophosphorus compound containing a P-H bond be quickly dissolved and fully mixed, but also the two reactants can have appropriate concentrations, so that the reaction rate can be controlled within a certain range. In some specific examples, the amount of the organic solvent is controlled to be 5 times, 10 times, 15 times, 20 times, 25 times, 35 times, or 50 times the mass of the isocyanate group-containing compound. Further, the amount of the organic solvent is controlled to be 15 to 25 times the mass of the isocyanate group-containing compound.

[0059] In some examples, the organic solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, dichloromethane, chloroform, ethanol, acetone, methyl ethyl ketone, tetrahydrofuran, and toluene. The organic solvents in these examples not only have a certain solubility with the isocyanate group-containing compound, but also need to have a certain solubility with the organophosphorus compound containing a P-H bond, so that both reactants can be dissolved by the organic solvent to form a relatively uniform reaction system. When the reaction is completed, the organic solvent has good volatility. Therefore, it is convenient to remove the above-mentioned organic solvent to obtain the required reaction product, which is convenient for further treatment.

[0060] In some embodiments of the present invention, the reaction time is 5 h to 75 h. By controlling the reaction time within the above time range, the corresponding functional groups (-N=C=O) of the isocyanate group-containing compound and the corresponding functional groups (-PH-) of the organophosphorus compound containing a P-H bond can react sufficiently, and then the P-C-N directly connected low dielectric phosphorus-nitrogen synergistic flame retardant of the present invention can be generated. For example, in specific examples, the reaction time is 5 h, 8 h, 10 h, 15 h, 20 h, 25 h, 30 h, 40 h, 48 h, 50 h, 60 h, 70 h, 72 h, or 75 h, etc. For example, in specific examples, any reaction time from 8 h to 48 h is selected.

[0061] In some embodiments of the present invention, the reaction temperature is 35°C to 115°C. By controlling the reaction temperature within the above temperature range, the corresponding functional groups (-N=C=O) of the isocyanate group-containing compound and the corresponding functional groups (-PH-) of the organophosphorus compound containing a P-H bond can react efficiently, making the reaction efficiency higher. For example, in specific examples, the reaction temperature is 35°C, 40°C, 45°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 90°C, 100°C, 105°C, 115°C, etc. When the reaction is controlled at 35°C to 60°C, the reaction conditions are milder and the reaction is safer.

[0062] In some embodiments of the present invention, after removing the organic solvent, the product formed by the reaction is washed with a washing agent, and the washing agent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, dichloromethane, chloroform, tetrahydrofuran, ethanol, ethyl acetate, petroleum ether, and ether. The product after being washed with the organic solvent can remove the unreacted excess reactants, thereby improving the purity of the product, and further improving the purity of the obtained low-dielectric phosphorus-nitrogen synergistic flame retardant. The corresponding type of washing agent can be selected according to the type of reactants used.

[0063] Next, the application of the low-dielectric phosphorus-nitrogen synergistic flame retardant in the foregoing examples of the present invention will be described.

[0064] A flame retardant material according to the present invention, which uses the low-dielectric phosphorus-nitrogen synergistic flame retardant with the foregoing structural general formula as Formula I as a flame retardant component, and the flame retardant material is selected from at least one of a flame retardant thermoplastic engineering material, a flame retardant thermosetting resin composition, a flame retardant encapsulating material, a flame retardant adhesive, a flame retardant laminate, and a flame retardant fiber reinforced material.

[0065] As can be seen from the above, from the above technical solutions, the flame retardant material proposed by the present invention, due to being modified with the low-dielectric phosphorus-nitrogen synergistic flame retardant of the present invention as a flame retardant component, has a low dielectric constant, high flame retardancy, good electrical insulation performance, low dielectric loss during long-term use or high-temperature use, and high thermal stability. In addition, the flame retardant material also has a certain structural strength, can maintain a certain stability and durability in high-temperature, high-pressure, and corrosive environments, and the material can also evenly distribute the acting force when stressed.

[0066] In some embodiments of the present invention, the flame retardant thermosetting resin composition is formed by mixing and curing the low-dielectric phosphorus-nitrogen synergistic flame retardant as a flame retardant component and a thermosetting resin matrix, wherein the thermosetting resin matrix is selected from at least one of a thermosetting polyphenylene ether resin, a hydrocarbon resin, an epoxy resin, a benzoxazine, a bismaleimide, a phenolic resin, and a polyurethane. For example, in some examples, the thermosetting resin matrix includes a thermosetting polyphenylene ether resin and a hydrocarbon resin.

[0067] In other examples, the thermoplastic resin matrix can also be flame-retardant modified. The thermoplastic resin matrix can be thermoplastic resins such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, polyester, polyoxymethylene, polyamide, and polyphenylene ether. In other examples, the thermosetting resin matrix includes polystyrene-butadiene resin and terminal vinyl polyphenylene ether resin, and the mass ratio of the low-dielectric phosphorus-nitrogen synergistic flame retardant, polystyrene-butadiene resin, and terminal vinyl polyphenylene ether resin is (10-30):(17.5-22.5):(52.5-67.5).

[0068] For example, in specific examples, the mass ratio of the low-dielectric phosphorus-nitrogen synergistic flame retardant, polystyrene-butadiene resin, and terminal vinyl polyphenylene ether resin is 10:22.5:67.5, 20:20:60, or 30:17.5:52.5. When the mass of each substance is controlled within the above range, the surface of the synthesized flame-retardant material can be covered by more low-dielectric phosphorus-nitrogen synergistic flame retardants, improving the flame-retardant performance and anti-dielectric degradation performance of the flame-retardant material.

[0069] The application of the flame-retardant material of the present invention is described below.

[0070] An application of a flame-retardant material according to the present invention in the field of electronic packaging uses the flame-retardant material of any of the foregoing embodiments as at least one of a copper-clad laminate, a packaging carrier board, and an epoxy molding compound.

[0071] As can be seen from the above technical solutions, in the application of the flame-retardant material proposed by the present invention in the field of electronic packaging, during long-term high-temperature use, the power of each electronic component is relatively large. However, the copper-clad laminate, packaging carrier board, and epoxy molding compound of the present invention have excellent flame-retardant performance, low dielectric loss, good dielectric stability, high thermal stability, and excellent characteristics of anti-dielectric performance degradation. Therefore, the electronic components can maintain a long-term stable working efficiency in a high-temperature environment, are not easily affected by high temperature, and have a good effect of anti-dielectric performance degradation. During long-term use, the dielectric performance is stable, and the service life of the electronic components is extended. The materials used for the copper-clad laminate, packaging carrier board, and epoxy molding compound are safer, more environmentally friendly, and have excellent dielectric and flame-retardant properties, meeting the stringent requirements of high-frequency electronic devices.

[0072] Furthermore, the field of electronic packaging is a high-frequency and high-speed electronic packaging field.

[0073] The following specifically describes the low-dielectric phosphorus-nitrogen synergistic flame retardant and its preparation method, and the flame-retardant material and its preparation method of the present invention in conjunction with specific embodiments.

[0074] In the following examples, the performance of the prepared flame-retardant thermosetting resin composition is measured according to the following method (the test method is a conventional method unless otherwise specified):

[0075] 1) Flame retardancy test method (ASTM UL94): CZF-3 horizontal and vertical burning tester.

[0076] 2) Dielectric property test method (IPC-TM-650 2.5.5.15): Agilent ENA series network analyzer and QWED N1501Exx split-column dielectric resonator (10 GHz).

[0077] 3) Test method for resistance to dielectric property deterioration: High-temperature aging is carried out in an oven at 150 °C. After aging for different times, the samples of each example and comparative example are taken out, placed in a desiccator and cooled to room temperature, and then tested.

[0078] For the convenience of performance comparison, in the following specific examples, the organophosphorus compound containing a P-H bond mainly selects 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide as one of the reactants. Other types of organophosphorus compounds containing a P-H bond with equivalent functions should fall within the protection scope of the present invention.

[0079] Example 1

[0080] The isocyanate compound used in this example is hexamethylene diisocyanate (HDI), and the organophosphorus compound containing a P-H bond used is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO).

[0081] The specific preparation method is as follows: 8.4 g of hexamethylene diisocyanate and 21.6 g of DOPO are dissolved in 50 ml of tetrahydrofuran, and 0.15 g of catalyst - triethylamine is added. The mixture is heated and raised to the reflux temperature, and the reaction is stopped after 12 h. The solvent is removed by suction filtration, and the product is washed and dried with ethanol multiple times. The obtained white solid is the low-dielectric phosphorus-nitrogen synergistic flame retardant (DH), and the yield is 95%.

[0082] The reaction equation is as follows:

[0083]

[0084] As Figure 1 and Figure 2As shown in the figure, the reactants HDI and DOPO used in the present invention produce a low dielectric phosphorus-nitrogen synergistic flame retardant (DH) after the reaction. Through infrared spectroscopy analysis, it can be observed that the isocyanate group (1750 cm-1) in HDI and the P-H bond (2437 cm-1) in DOPO disappear after the reaction, and at the same time, -NHCO- amide groups are generated, and their characteristic absorption peaks appear at 3284 cm-1 and 1660 cm-1 respectively. In addition, the peak positions and integral areas of the 1H NMR spectrum correspond one by one to the structural characteristics of DH, further verifying the correct molecular structure of the product. In the product, some functional groups in the original reactants are retained, such as the P=O group and aromatic ring of DOPO, and at the same time, new -NHCO- amide functional groups are generated. This structural feature makes the product have a high purity and can be easily separated by organic solvents, facilitating subsequent processing and application. These results fully prove the successful synthesis of the phosphorus-nitrogen synergistic flame retardant and the rationality and correctness of its structure.

[0085] Example 2

[0086] In this example, the isocyanate compound used is diphenylmethane-4,4'-diisocyanate, and the organophosphorus compound containing a P-H bond used is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO).

[0087] The specific preparation method is as follows: Dissolve 12.5 g of diphenylmethane-4,4'-diisocyanate and 21.6 g of DOPO in 50 ml of tetrahydrofuran, add 0.17 g of catalyst - triethylamine, heat and raise the temperature to the reflux temperature, stop the reaction after 12 h, remove the solvent by suction filtration, and wash and dry with ethanol multiple times. The obtained white solid is the low dielectric phosphorus-nitrogen synergistic flame retardant (DM), and the yield is 98%.

[0088] The reaction equation is as follows:

[0089]

[0090] Example 3

[0091] In this example, the isocyanate compound used is isophorone diisocyanate, and the organophosphorus compound containing a P-H bond used is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO).

[0092] The specific preparation method is as follows: Dissolve 11.1 g of isophorone diisocyanate and 21.6 g of DOPO in 50 ml of tetrahydrofuran, add 0.16 g of catalyst - triethylamine, heat and raise the temperature to the reflux temperature, stop the reaction after 48 h, remove the solvent by suction filtration, wash with ethanol several times and dry. The obtained white solid is the low-dielectric phosphorus-nitrogen synergistic flame retardant (DI), and the yield is 85%.

[0093] The reaction equation is as follows:

[0094]

[0095] Example 4

[0096] In this example, the isocyanate compound used is m-phenylene diisocyanate, and the organophosphorus compound containing P-H bond used is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO).

[0097] The specific preparation method is as follows: Dissolve 8.0 g of m-phenylene diisocyanate and 21.6 g of DOPO in 50 ml of tetrahydrofuran, add 0.15 g of catalyst - triethylamine, heat and raise the temperature to the reflux temperature, stop the reaction after 12 h, remove the solvent by suction filtration, wash with ethanol several times and dry. The obtained white solid is the low-dielectric phosphorus-nitrogen synergistic flame retardant (D13), and the yield is 97%.

[0098] The reaction equation is as follows:

[0099]

[0100] Example 5

[0101] In this example, the isocyanate compound used is p-phenylene diisocyanate, and the organophosphorus compound containing P-H bond used is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO).

[0102] The specific preparation method is as follows: Dissolve 8.0 g of p-phenylene diisocyanate and 21.6 g of DOPO in 50 ml of tetrahydrofuran, add 0.15 g of catalyst - triethylamine, heat and raise the temperature to the reflux temperature, stop the reaction after 12 h, remove the solvent by suction filtration, wash with ethanol several times and dry. The obtained white solid is the low-dielectric phosphorus-nitrogen synergistic flame retardant (D14), and the yield is 97%.

[0103] The reaction equation is as follows:

[0104]

[0105] Example 6

[0106] In this embodiment, the isocyanate compound used is toluene diisocyanate, and the organophosphorus compound containing P-H bond used is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO).

[0107] The specific preparation method is as follows: Dissolve 8.7 g of toluene diisocyanate and 21.6 g of DOPO in 50 ml of tetrahydrofuran, add 0.15 g of catalyst - triethylamine, heat and raise the temperature to the reflux temperature, stop the reaction after 12 h, remove the solvent by suction filtration, wash with ethanol several times and dry. The obtained white solid is the low dielectric phosphorus-nitrogen synergistic flame retardant (D13C), and the yield is 90%.

[0108] The reaction equation is as follows:

[0109]

[0110] Example 7

[0111] In this embodiment, the isocyanate compound used is dicyclohexylmethane 4,4'-diisocyanate, and the organophosphorus compound containing P-H bond used is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). The specific preparation method is as follows: Dissolve 13.1 g of dicyclohexylmethane 4,4'-diisocyanate and 21.6 g of DOPO in 50 ml of tetrahydrofuran, add 0.15 g of catalyst - triethylamine, heat and raise the temperature to the reflux temperature, stop the reaction after 12 h, remove the solvent by suction filtration, wash with ethanol several times and dry. The obtained white solid is the low dielectric phosphorus-nitrogen synergistic flame retardant (DHM), and the yield is 90%.

[0112] The reaction equation is as follows:

[0113]

[0114] The reactants, organic solvents, catalysts and washing agents of the organophosphorus compounds containing P-H bonds in the above Examples 1-7 can all be replaced with other types within the protection scope of the present invention, which will not be elaborated here. For example, dimethyl phosphite with a molar ratio of 1:2 to toluene diisocyanate can also be selected; diethyl phosphite with a molar ratio of 1:2 to p-phenylene diisocyanate; diphenyl phosphite with a molar ratio of 1:2 to m-phenylene diisocyanate; dimethyl phosphite with a molar ratio of 1:2 to dicyclohexylmethane 4,4-diisocyanate; diphenylphosphine oxide with a molar ratio of 1:2 to dicyclohexylmethane 4,4-diisocyanate, etc. The above-listed are only examples and cannot exhaust all combinations, but substances that conform to the reactions of the present invention should be included within the protection scope of the present invention.

[0115] The low-dielectric phosphorus-nitrogen synergistic flame retardants obtained in Examples 1-7 were compounded with a thermosetting polyphenylene ether resin to obtain a flame-retardant thermosetting resin composition for the field of electronic packaging. The preparation method of the flame-retardant thermosetting resin composition in the following examples is as follows:

[0116] Step 1: According to the ratio, mix the thermosetting polyphenylene ether resin, hydrocarbon resin and toluene evenly to obtain a transparent brown solution.

[0117] Step 2: Mix the low-dielectric phosphorus-nitrogen synergistic flame retardant with toluene and ultrasonically obtain a suspension.

[0118] Step 3: Mix the above suspension evenly with the brown solution obtained in Step 1, add the initiator BIPB (bis(1-(tert-butylperoxy)-1-methylethyl)-benzene), stir evenly, and then pour the mixed solution into a tray. Drain part of the solvent at room temperature to obtain a mixture.

[0119] Step 4: Dry the above mixture in a vacuum oven at 60 °C and 5 mbar for 6 h, and grind and crush it to obtain a powdery resin mixture.

[0120] Step 5: Put the obtained resin mixture into a suitable mold for vacuum hot pressing to obtain the required sample.

[0121] Example 8

[0122] The flame-retardant thermosetting resin composition of this example, by mass, includes the following components: ① 7.5 g of polyphenylene ether resin (SABIC, SA9000); ② 2.5 g of hydrocarbon resin (CRAY VALLEY, Ricon 100); ③ 2 g of the low-dielectric phosphorus-nitrogen synergistic flame retardant DH in Example 1 above; ④ 0.075 g of initiator (Hunan Enpi, BIPB); ⑤ an appropriate amount of solvent (Shanghai Aladdin, toluene).

[0123] Example 9

[0124] The components and preparation method of the flame-retardant material in Example 8 are substantially the same, except that the low-dielectric phosphorus-nitrogen synergistic flame retardant DH is replaced with the low-dielectric phosphorus-nitrogen synergistic flame retardant DM.

[0125] Example 10

[0126] The components and preparation method of the flame-retardant material in Example 8 are substantially the same, except that the low-dielectric phosphorus-nitrogen synergistic flame retardant DH is replaced with the low-dielectric phosphorus-nitrogen synergistic flame retardant DI.

[0127] Example 11

[0128] It is substantially the same as the components and preparation method of the flame retardant material in Example 8, except that the low dielectric phosphorus-nitrogen synergistic flame retardant DH is replaced with the low dielectric phosphorus-nitrogen synergistic flame retardant D13.

[0129] Example 12

[0130] It is substantially the same as the components and preparation method of the flame retardant material in Example 8, except that the low dielectric phosphorus-nitrogen synergistic flame retardant DH is replaced with the low dielectric phosphorus-nitrogen synergistic flame retardant D14.

[0131] Example 13

[0132] It is substantially the same as the components and preparation method of the flame retardant material in Example 8, except that the low dielectric phosphorus-nitrogen synergistic flame retardant DH is replaced with the low dielectric phosphorus-nitrogen synergistic flame retardant D13C.

[0133] Example 14

[0134] It is substantially the same as the components and preparation method of the flame retardant material in Example 8, except that the low dielectric phosphorus-nitrogen synergistic flame retardant is replaced with the low dielectric phosphorus-nitrogen synergistic flame retardant DHM.

[0135] Comparative Example 1

[0136] It is substantially the same as the components and preparation method of the flame retardant material in Example 8, except that no flame retardant is added in this comparative example.

[0137] Comparative Example 2

[0138] It is substantially the same as the components and preparation method of the flame retardant material in Example 8, except that DOPO is used to replace the low dielectric phosphorus-nitrogen synergistic flame retardant DH.

[0139] Comparative Example 3

[0140] It is substantially the same as the components and preparation method of the flame retardant material in Example 8, except that the same mass of silica is used to replace the low dielectric phosphorus-nitrogen synergistic flame retardant DH.

[0141] Table 1 Test performance table of the flame retardant thermosetting resin compositions obtained in Examples 8-14 and Comparative Examples 1-3

[0142]

[0143] By comparing the results of Examples 8-14 and Comparative Examples 1-3, it can be seen that after adding the low dielectric phosphorus-nitrogen synergistic flame retardant shown in Formula I provided by the present invention to the thermosetting polyphenylene ether resin in a certain proportion, the thermosetting polyphenylene ether material can have very good flame retardant performance, and the flame retardant performance reaches UL94-V0.

[0144] By comparing the results of Examples 8-14 with those of Comparative Example 2, it can be seen that under the condition of the same content, the dielectric properties of the low-dielectric phosphorus-nitrogen synergistic flame retardant represented by Formula I provided by the present invention are significantly better than those of DOPO, especially the dielectric loss is significantly less than that of the modified thermosetting resin composition prepared by adding DOPO.

[0145] By comparing the results of Examples 8-14 with those of Comparative Example 3, it can be seen that under the condition of the same content, the dielectric constant of the flame-retardant thermosetting resin composition prepared by the low-dielectric phosphorus-nitrogen synergistic flame retardant represented by Formula I provided by the present invention is significantly lower than that of the thermosetting resin composition modified with silica, while the dielectric loss is comparable to that of the thermosetting resin composition modified with silica. It can be seen that the dielectric properties of the flame-retardant thermosetting resin composition prepared by adding the low-dielectric phosphorus-nitrogen synergistic flame retardant of the present invention are excellent.

[0146] By comparing the results of Examples 8-14 with those of Comparative Example 1 and Comparative Example 3, combined with Figure 3 the aging test result diagram, it can be seen that under the condition of the same content, for the flame-retardant thermosetting resin composition prepared by the low-dielectric phosphorus-nitrogen synergistic flame retardant represented by Formula I provided by the present invention, over time, its dielectric loss is significantly lower than that of the following several comparative compositions: the thermosetting resin composition without adding a flame retardant, the thermosetting resin composition modified with silica, and the thermosetting resin composition modified with DOPO. This result shows that the low-dielectric phosphorus-nitrogen synergistic flame retardant of the present invention can effectively inhibit the deterioration of the dielectric properties of thermosetting resins while improving the flame retardant performance, especially maintaining its excellent dielectric stability during the aging process. This advantage makes it have broad application prospects in high-frequency circuit materials and other fields with high requirements for dielectric properties. Under the condition of the same content, the phosphorus-nitrogen synergistic flame retardant represented by Formula I provided by the present invention can significantly inhibit the deterioration of the dielectric properties of thermosetting polyphenylene ether.

[0147] By comparing the results of Examples 8-14 with those of Comparative Example 2, combined with Figure 3 the aging test result diagram, it can be seen that under the condition of the same content, the low-dielectric phosphorus-nitrogen synergistic flame retardant represented by Formula I provided by the present invention can significantly inhibit the deterioration of its dielectric properties without reducing the glass transition temperature of thermosetting polyphenylene ether.

[0148] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A low dielectric phosphorus-nitrogen synergistic flame retardant, characterized in that: The general structural formula is shown in Formula I:

2. A method for preparing the low dielectric phosphorus-nitrogen synergistic flame retardant according to claim 1, characterized in that: The low dielectric phosphorus-nitrogen synergistic flame retardant is synthesized by reacting an isocyanate-containing compound with an organic phosphorus compound containing a PH bond, and the general synthesis formula is shown in Formula II:

3. The method for preparing the low dielectric phosphorus-nitrogen synergistic flame retardant according to claim 2, characterized in that: The isocyanate group-containing compound is an isocyanate group-containing R1 group, wherein the R1 group is selected from any one of a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, an arylalkyl group, an alkylaryl group, a heteroarylalkyl group, an alkylheteroaryl group, a substituted alkyl group, a substituted cycloalkyl group, a substituted aryl group, a substituted heteroaryl group, a substituted arylalkyl group, a substituted alkylaryl group, a substituted heteroarylalkyl group, and a substituted alkylheteroaryl group; and the substitution includes hydrogen atom substitution, heteroatom substitution, or hydrogen atom and heteroatom substitution.

4. The method for preparing the low dielectric phosphorus-nitrogen synergistic flame retardant according to claim 2, characterized in that: The organophosphorus compound containing a PH bond is selected from at least one of dimethyl phosphite, diethyl phosphite, diphenyl phosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, ethyl phenylphosphite and diphenylphosphine; the isocyanate group-containing compound is selected from at least one of hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane-4,4'-diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate and dicyclohexylmethane 4,4-diisocyanate.

5. The method for preparing the low dielectric phosphorus-nitrogen synergistic flame retardant according to claim 2, characterized in that: The reaction synthesis process includes the following steps: dissolving an isocyanate-containing compound and an organic phosphorus compound containing a PH bond in an organic solvent, adding a catalyst after they are completely dissolved, reacting under heating conditions, filtering and centrifuging the reaction solution after the reaction is completed to remove the organic solvent and unreacted impurities, and drying to obtain the low-dielectric phosphorus-nitrogen synergistic flame retardant.

6. The method for preparing the low dielectric phosphorus-nitrogen synergistic flame retardant according to claim 5, characterized in that: The molar ratio of the isocyanate group-containing compound to the PH bond-containing organic phosphorus compound is 1:(1-3); The molar ratio of the isocyanate group-containing compound to the catalyst is 1:(0.01-0.1); The amount of the organic solvent is 5 to 50 times the mass of the isocyanate-containing compound; The organic solvent includes at least one of N,N-dimethylformamide, dimethyl sulfoxide, dichloromethane, chloroform, ethanol, acetone, butanone, tetrahydrofuran, and toluene; The catalyst is selected from at least one of triethylamine, potassium tert-butoxide, sodium methoxide or anhydrous potassium carbonate; The reaction time is 5h~75h; The reaction temperature is 35°C to 115°C.

7. The method for preparing the low dielectric phosphorus-nitrogen synergistic flame retardant according to claim 5, characterized in that: Removing unreacted impurities includes the following steps: washing the product generated by the reaction with a lotion, wherein the lotion is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, dichloromethane, chloroform, tetrahydrofuran, ethanol, ethyl acetate, petroleum ether and ether.

8. A flame retardant material using the low dielectric phosphorus-nitrogen synergistic flame retardant according to claim 1 as a flame retardant component, characterized in that: The flame retardant material is selected from at least one of flame retardant thermoplastic engineering materials, flame retardant thermosetting resin compositions, flame retardant packaging materials, flame retardant adhesives, flame retardant laminates and flame retardant fiber reinforced materials.

9. The flame retardant material according to claim 8, characterized in that The flame retardant thermosetting resin composition comprises a composition obtained by mixing and curing at least one of thermosetting polyphenylene ether resin, hydrocarbon resin, epoxy resin, benzoxazine, bismaleimide, phenolic resin or polyurethane and a low dielectric phosphorus-nitrogen synergistic flame retardant.

10. Use of the flame retardant material according to claim 8 or 9 in the field of electronic packaging, characterized in that: The invention comprises using flame retardant materials to make at least one of the copper clad plate, the packaging carrier plate and the epoxy molding compound.

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