Phosphorus-nitrogen type flame-retardant curing agent, preparation method thereof and application of phosphorus-nitrogen type flame-retardant curing agent in electronic-grade flame-retardant epoxy resin composition

Abstract

The invention provides a phosphorus-nitrogen type flame-retardant curing agent, a preparation method thereof and application of the phosphorus-nitrogen type flame-retardant curing agent in an electronic-grade flame-retardant epoxy resin composition, and belongs to the technical field of preparation of intrinsic flame-retardant curing agents. Aiming at the problems of precipitation, low flame-retardant efficiency, halogen-containing toxicity and the like of the existing epoxy resin flame retardant, phytic acid and urea react to generate a phosphorus-containing intermediate, and the phosphorus-nitrogen type flame-retardant curing agent is prepared by bonding the phosphorus-containing intermediate with an amino compound. According to the curing agent, a phosphorus-nitrogen synergistic flame-retardant group is introduced and is chemically crosslinked with epoxy resin to form an intrinsic flame-retardant system, so that the defect of migration and precipitation of a traditional additive is overcome. When the epoxy resin composition is applied to an electronic-grade epoxy resin composition, the limit oxygen index of the material can reach 31.7% or above, the UL-94 reaches the V-0 grade, and the thermal stratification time T288 is prolonged to 100 minutes or above. Through molecular structure design, the obtained electronic-grade flame-retardant epoxy resin is excellent in performance and high in reliability. And the product is simple in preparation method, wide in synthesized monomer source, excellent in performance, halogen-free and environment-friendly, and has a good application prospect in the fields of 5G, new energy, electric automobiles and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of intrinsic flame retardant curing agents, and relates to a phosphorus-nitrogen type flame retardant curing agent, a preparation method thereof, and an application in an electronic-grade flame retardant epoxy resin composition. Background Art

[0002] The explosive growth of new energy vehicles, 5G communications, and consumer electronics has promoted the evolution of electronic components towards high integration and high power density. Especially in the field of new energy vehicles, core components such as battery packs, motors, and electronic control systems face the risk of fire caused by high temperature and short circuits during operation. If the flame retardant performance of the encapsulation material is insufficient, the fire will spread rapidly and release highly toxic smoke, seriously threatening the safety of drivers and passengers and the integrity of equipment. Therefore, the development of electronic packaging materials with both high flame retardancy and process adaptability has become an industry necessity.

[0003] Epoxy resin has long dominated the field of electronic packaging materials due to its excellent mechanical properties, electrical insulation properties, and chemical corrosion resistance. However, its inherent defects are significant: prominent flammability: the limiting oxygen index (LOI) is only about 23%, and it burns violently under high temperature or open flame, releasing a large amount of heat and toxic smoke; high environmental risk: traditional halogen flame retardant systems (such as decabromodiphenyl ether) need to add 20 - 30wt% to meet the standard, but carcinogenic substances such as dioxins and hydrogen halides are produced during combustion, violating environmental protection regulations such as EU RoHS; deterioration of process performance: high addition amounts lead to a sharp increase in the viscosity of the material, a decrease in flow filling performance, and it is difficult to meet the strict requirements of micro-gap filling for precision electronic packaging.

[0004] Although halogen-free flame retardants such as phosphorus-based and nitrogen-based can avoid halogen pollution, there are still problems of imbalance between efficiency and performance: insufficient flame retardant efficiency: a relatively high addition amount (>15wt%) is required to reach the UL94 V-0 level, resulting in a significant decrease in the mechanical strength and heat resistance of the material; poor interfacial compatibility: physical blending easily causes phase separation, affecting the dielectric property uniformity of epoxy resin and making it difficult to meet the requirements of high-frequency electronic devices. Currently, flame retardant groups such as phosphorus and silicon can be introduced into the epoxy backbone through chemical modification, which can improve the charring property and LOI value. To improve the safety of electronic products and ensure the safety of personnel and the integrity of equipment under extreme conditions such as fire, it is very necessary to carry out flame retardant modification on epoxy resin electronic adhesives. Summary of the Invention

[0005] In view of this, the present invention constructs a phosphorus-nitrogen chemical bonding structure, utilizes the dual flame retardant synergistic effect of the gas phase mechanism (releasing inert gas) and the condensed phase mechanism (promoting the formation of a dense carbon layer); embeds the flame retardant unit into the curing agent molecular chain, and simultaneously realizes flame retardant functionalization and network crosslinking during the curing reaction, avoiding the performance deterioration caused by physical addition.

[0006] The object of the present invention is to provide a phosphorus-nitrogen type flame retardant curing agent, the second object is to provide a preparation method of the phosphorus-nitrogen type flame retardant curing agent, and the third object is the application of the phosphorus-nitrogen type flame retardant curing agent in an electronic grade flame retardant epoxy resin composition.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a phosphorus-nitrogen type flame retardant curing agent, and the phosphorus-nitrogen type flame retardant curing agent is a compound of structural formula I, and the structural formula I is:

[0009] ,

[0010] wherein R1 to R 10 is a compound of structural formula II including 0 to 6 numbers, and the rest is NH4 + ; the structural formula II is: R 11 , R 12 are simultaneously any one of methyl, ethyl or isopropyl;

[0011] Furthermore, for the preparation method of the phosphorus-nitrogen type flame retardant curing agent, the preparation method includes the following steps:

[0012] (1) Dissolve phytic acid and urea in water, place them in a reaction kettle, heat and then carry out condensation reflux reaction, and obtain an intermediate of structural formula III after purification and drying;

[0013] (2) Add HY-2NH2 into a flask equipped with a condensation device, add an organic solvent to dissolve it, add the intermediate for reaction after heating and dissolving, remove the solvent and then carry out vacuum heating and drying to obtain the phosphorus-nitrogen type flame retardant curing agent.

[0014] The structural formula III is: wherein R 13 to R 24 include 2 to 8 numbers of H + , and the rest is NH4 + ;

[0015] The structural formula of HY-2NH2 is: R 11 , R 12 are simultaneously any one of methyl, ethyl or isopropyl;

[0016] Preferably, in step (1), the molar ratio of phytic acid to urea is 1:1 to 7;

[0017] In step (1), the heating and then condensation reflux specifically is: heating to 60 to 150 °C, and carrying out condensation reflux reaction for 20 to 200 min;

[0018] In step (1), the organic solvent is any one of toluene, xylene, tetrahydrofuran, acetone, ethanol or isopropanol;

[0019] Preferably, in step (2), the molar ratio of HY-2NH2 to the intermediate is 2-7:1

[0020] In step (2), the temperature for heating and dissolving is 30°C to 100°C;

[0021] In step (2), the temperature when the intermediate is added is 25°C to 150°C, and the reaction time is 1h to 10h;

[0022] Preferably, in step (2), the reduced-pressure heating and drying is specifically carried out at a temperature of 90°C to 180°C and a negative pressure of 0.01 - 0.1 MPa;

[0023] Furthermore, the application of the phosphazene-based flame retardant curing agent in the preparation of an electronic-grade flame retardant epoxy resin composition;

[0024] Furthermore, the present invention also provides an electronic-grade flame retardant epoxy resin composition. By weight, the electronic-grade flame retardant epoxy resin composition comprises 60 - 100 parts of an electronic-grade epoxy resin, 10 - 50 parts of a curing agent mixture containing the phosphazene-based flame retardant curing agent as claimed in claim 1, and 0.1 - 3 parts of a curing accelerator;

[0025] Preferably, the electronic-grade epoxy resin includes at least one of an electronic-grade bisphenol A epoxy resin, a phenolic epoxy resin, an o-cresol novolac epoxy resin or a hydrogenated bisphenol A epoxy resin;

[0026] The curing accelerator is at least one of triphenylphosphine, boron trifluoride ethylamine complex, 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, triethylenetetramine triethylamine, triethanolamine, o-hydroxybenzyldimethylamine, 4-nonylphenol, N-aminoethylpiperazine or ethyl levulinate;

[0027] Preferably, the curing agent mixture further includes any one or several of 4,4'-diaminodiphenylmethane, benzyldimethylamine, m-phenylenediamine, N,N-dimethylbenzylamine, 4,4'-diaminodiphenyl sulfone, adipic dihydrazide, salicylic hydrazide, succinic hydrazide, phthalic anhydride, methylhexahydrophthalic anhydride, trimellitic anhydride, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-tolylimidazole, 2-phenyl-4-methylimidazole, dicyandiamide, o-tolylbiguanide, p-tolylbiguanide, polyhexamethylenebiguanide or N-methylpiperazine;

[0028] Furthermore, the preparation method of the electronic-grade flame retardant epoxy resin composition includes the following steps:

[0029] Under a nitrogen atmosphere, a curing agent mixture containing the phosphorus-nitrogen flame retardant curing agent is added to a reactor, stirred and dissolved, and then an electronic-grade epoxy resin and a curing accelerator are added in sequence. After mixing and stirring, the mixture is vacuumed and vented, and placed in a mold for curing to obtain an electronic-grade flame retardant epoxy resin composition.

[0030] The beneficial effects of the present invention are:

[0031] Through structural innovation, the curing agent of this invention directly embeds a phosphorus-containing bio-based polyamine into the epoxy resin backbone, achieving intrinsic fixation of the flame retardant element. This overcomes the migration and precipitation issues associated with the uneven physical dispersion of traditional additive flame retardants. Furthermore, the phosphorus-nitrogen synergistic flame retardancy mechanism significantly improves flame retardancy, achieving an oxygen index of 34%. At high temperatures, the curing agent self-crosslinks to form a dense carbon layer, inhibiting the diffusion of heat and combustible gases.

[0032] Environmental friendliness and raw material compatibility: Utilizing bio-based raw materials and a halogen-free design, the product complies with RoHS and REACH regulations. Bio-based raw materials account for >30% of the product, resulting in a 20-30% reduction in carbon emissions over its lifecycle compared to petrochemical-based flame retardants. All synthetic monomers are commercially available, widely available, and compatible with existing industrial systems.

[0033] The electronic-grade flame-retardant epoxy resin obtained through molecular structure design has excellent performance and high reliability. The product is also simple to prepare, uses a wide range of synthetic monomers, and has excellent performance, is halogen-free, and is environmentally friendly. It has promising application prospects in fields such as 5G, new energy, and electric vehicles.

[0034] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings.

[0036] Figure 1 The SEM morphology of carbon residue on the specimen after vertical burning test (UL-94) (Comparative Example 5, ×500, ×2000; Example 7, ×500, ×2000);

[0037] Figure 2 This is the TG curve of Example 7 under nitrogen atmosphere. DETAILED DESCRIPTION

[0038] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0039] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as limiting the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0040] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0041] The structural formula I of the phosphorus-nitrogen type flame retardant curing agent of the present invention is: ,

[0042] Among them, R1 to R 10 includes 2 to 6 numbers of compounds with structural formula II, and the rest are NH4 + ; the structural formula II is: R 11 , R 12 are both any one of methyl, ethyl or isopropyl at the same time; the compound with structural formula III is: Among them, R 13 to R 24 includes 2 to 6 numbers of H + , and the rest are NH4 + .

[0043] Example 1

[0044] A phosphorus-nitrogen type flame retardant curing agent (PA-2NH2), and the specific preparation method is as follows:

[0045] (1) Dissolve phytic acid and urea in water according to a molar ratio of 1:5, place them in a reaction kettle, heat to 100 °C, carry out a condensation reflux reaction for 100 min, purify with toluene and dry to obtain an intermediate of structural formula Ⅳ;

[0046] The structural formula Ⅳ is:

[0047] (2) The structural formula of HY-2NH2 is as follows:

[0048]

[0049] Mix HY-2NH2 and the intermediate of structural formula Ⅳ at a molar ratio of 2:1, add them to a flask equipped with a condensation device, add toluene to dissolve, heat to 50 °C and stir to dissolve, continue to heat to 100 °C and then add the intermediate to react for 5 h, remove the solvent and then carry out vacuum heating and drying (dry at a temperature of 90 °C to 180 °C and a negative pressure of 0.01 - 0.1 MPa), and then the phosphorus-nitrogen type flame retardant curing agent (PA-2NH2) can be obtained, and its structural formula is:

[0050]

[0051] Example 2

[0052] An electronic-grade flame retardant epoxy resin composition, and the specific preparation method is as follows:

[0053] Under a nitrogen atmosphere, add 27.11 parts of 4,4'-diaminodiphenyl sulfone (DDS) and 0.78 parts of the phosphorus-nitrogen type flame retardant curing agent (PA-2NH2) prepared in Example 1 above to a reactor, stir at 170 °C until DDS and PA-2NH2 are completely dissolved, then add 100 parts of bisphenol A epoxy resin (DGEBA) and 0.5 part of o-hydroxybenzyl dimethylamine (DMP-10) as a curing accelerator, mix and stir evenly to obtain a mixture, evacuate for 15 min to exhaust air, and then pour it into a polytetrafluoroethylene mold while it is hot. First, cure at 120 °C for 2 h, and then cure at 180 °C for 2 h to obtain the electronic-grade flame retardant epoxy resin composition.

[0054] Example 3

[0055] A phosphorus-nitrogen type flame retardant curing agent (PA-3NH2), and the specific preparation method is as follows:

[0056] (1) Dissolve phytic acid and urea in water according to a molar ratio of 1:4, place them in a reaction kettle, heat to 100 °C, carry out a condensation reflux reaction for 100 min, purify with toluene and dry to obtain an intermediate of structural formula Ⅴ,

[0057] The structural formula Ⅴ is as follows:

[0058] (2) The structural formula of HY-2NH2 is:

[0059] Mix HY-2NH2 and the intermediate of structural formula Ⅴ at a molar ratio of 2:1, add them to a flask equipped with a condensing device, dissolve with toluene, heat to 50 °C and stir to dissolve, continue to heat to 100 °C and then add the intermediate for reaction for 5 h. After removing the solvent, carry out vacuum heating and drying (dry at a temperature of 90 °C to 180 °C and a negative pressure of 0.01 - 0.1 MPa), then the phosphorus-nitrogen type flame retardant curing agent (PA-3NH2) can be obtained, and its structural formula is:

[0060]

[0061] Example 4

[0062] An electronic-grade flame retardant epoxy resin composition, and the specific preparation method is as follows:

[0063] Under a nitrogen atmosphere, add 27.11 parts of 4,4'-diaminodiphenyl sulfone (DDS) and 0.78 parts of the phosphorus-nitrogen type flame retardant curing agent (PA-3NH2) prepared in Example 3 above to a reactor, stir at 170 °C until DDS and PA-3NH2 are completely dissolved, then add 100 parts of bisphenol A epoxy resin (DGEBA) and 0.5 part of o-hydroxybenzyl dimethylamine (DMP-10) as a curing accelerator, mix and stir evenly to obtain a mixture, evacuate for 15 min to exhaust air, and then pour it into a polytetrafluoroethylene mold while it is hot. First cure at 120 °C for 2 h, and then cure at 180 °C for 2 h to obtain the electronic-grade flame retardant epoxy resin composition.

[0064] Example 5

[0065] A phosphorus-nitrogen type flame retardant curing agent (PA-4NH2), and the specific preparation method is as follows:

[0066] (1) Dissolve phytic acid and urea at a molar ratio of 1:3 in water, place them in a reaction kettle, heat to 100 °C, carry out condensation reflux reaction for 100 min, purify with toluene and dry to obtain the intermediate of structural formula Ⅵ,

[0067] The structural formula Ⅵ is as follows:

[0068]

[0069] (2) The structural formula of HY-2NH2 is:

[0070] The molar ratio of HY-2NH2 to the intermediate of Structural Formula VI is 2:5. Add them to a flask equipped with a condensing device, dissolve them with toluene, heat to 50 °C and stir to dissolve. Then continue heating to 100 °C, add the intermediate and react for 5 h. After removing the solvent, carry out drying under reduced pressure and heating (dry at a temperature of 90 °C to 180 °C and a negative pressure of 0.01 - 0.1 MPa), and the phosphazene-based flame retardant curing agent (PA-4NH2) can be obtained. Its structural formula is:

[0071]

[0072] Example 6

[0073] An electronic-grade flame-retardant epoxy resin composition, and its specific preparation method is as follows:

[0074] Under a nitrogen atmosphere, add 27.11 parts of 4,4'-diaminodiphenyl sulfone (DDS) and 0.78 parts of the phosphazene-based flame retardant curing agent (PA-4NH2) prepared in Example 5 above to a reactor. Stir at 170 °C until DDS and PA-4NH2 are completely dissolved. Then add 100 parts of bisphenol A epoxy resin (DGEBA) and 0.5 parts of o-hydroxybenzyl dimethylamine (DMP-10) as a curing accelerator, mix and stir evenly to obtain a mixture. After evacuating for 15 min to remove air, pour the hot mixture into a polytetrafluoroethylene mold, cure at 120 °C for 2 h first, and then cure at 180 °C for 2 h to obtain the electronic-grade flame-retardant epoxy resin composition.

[0075] Example 7

[0076] A flame-retardant phosphorus-containing epoxy resin material, and its specific preparation method is as follows:

[0077] Under a nitrogen atmosphere, add 26.75 parts of 4,4'-diaminodiphenyl sulfone (DDS) and 2.37 parts of the phosphazene-based flame retardant curing agent (PA-3NH2) prepared in Example 3 above to a reactor. Stir at 170 °C until DDS and PA-3NH2 are completely dissolved. Then add 100 parts of bisphenol A epoxy resin (DGEBA) and 0.5 parts of o-hydroxybenzyl dimethylamine (DMP-10) as a curing accelerator, mix and stir evenly to obtain a mixture. After evacuating for 15 min to remove air, pour the hot mixture into a polytetrafluoroethylene mold, cure at 120 °C for 2 h first, and then cure at 180 °C for 2 h to obtain the electronic-grade flame-retardant epoxy resin composition.

[0078] Example 8

[0079] An electronic-grade flame-retardant epoxy resin composition, and its specific preparation method is as follows:

[0080] Under a nitrogen atmosphere, 26.39 parts of 4,4'-diaminodiphenyl sulfone (DDS) and 3.99 parts of the phosphorus-nitrogen type flame retardant curing agent (PA-3NH2) prepared in Example 3 above were added to a reactor. The mixture was stirred at 170 °C until DDS and PA-3NH2 were completely dissolved. Then, 100 parts of bisphenol A epoxy resin (DGEBA) and 0.5 part of o-hydroxybenzyldimethylamine (DMP-10) were added as a curing accelerator. The mixture was stirred evenly to obtain a mixture. After evacuating for 15 min to remove air, the mixture was poured into a polytetrafluoroethylene mold while it was still hot. It was first cured at 120 °C for 2 h and then cured at 180 °C for 2 h to obtain an electronic-grade flame retardant epoxy resin composition.

[0081] Example 9

[0082] A flame retardant phosphorus-containing epoxy resin material, and the specific preparation method is as follows:

[0083] Under a nitrogen atmosphere, 25.45 parts of 4,4'-diaminodiphenyl sulfone (DDS) and 8.24 parts of the phosphorus-nitrogen type flame retardant curing agent (PA-3NH2) prepared in Example 3 above were added to a reactor. The mixture was stirred at 170 °C until DDS and PA-3NH2 were completely dissolved. Then, 100 parts of bisphenol A epoxy resin (DGEBA) and 0.5 part of o-hydroxybenzyldimethylamine (DMP-10) were added as a curing accelerator. The mixture was stirred evenly to obtain a mixture. After evacuating for 15 min to remove air, the mixture was poured into a polytetrafluoroethylene mold while it was still hot. It was first cured at 120 °C for 2 h and then cured at 180 °C for 2 h to obtain an electronic-grade flame retardant epoxy resin composition.

[0084] Comparative Example 1

[0085] An electronic-grade flame retardant epoxy resin composition, and the specific preparation method is as follows:

[0086] Under a nitrogen atmosphere, 28.55 parts of 4,4'-diaminodiphenyl sulfone (DDS) were added to a reactor and stirred evenly at 170 °C. Then, 100 parts of bisphenol A epoxy resin (DGEBA) and 0.5 part of o-hydroxybenzyldimethylamine (DMP-10) were added as a curing accelerator. The mixture was stirred evenly to obtain a mixture. After evacuating for 15 min to remove air, the mixture was poured into a polytetrafluoroethylene mold while it was still hot. It was first cured at 120 °C for 2 h and then cured at 180 °C for 2 h to obtain an electronic-grade flame retardant epoxy resin composition.

[0087] Comparative Example 2

[0088] An electronic-grade flame retardant epoxy resin composition, and the specific preparation method is as follows:

[0089] Under a nitrogen atmosphere, 28.55 parts of 4,4'-diaminodiphenyl sulfone (DDS) and 8.24 parts of HY-2NH2 were added to a reactor and stirred evenly at 170 °C. Then, 100 parts of bisphenol A epoxy resin (DGEBA) and 0.5 part of o-hydroxybenzyldimethylamine (DMP-10) were added as a curing accelerator according to the formulation amount, and the mixture was stirred evenly to obtain a mixture. After evacuating for 15 min to exhaust air, it was poured into a polytetrafluoroethylene mold while it was still hot. It was first cured at 120 °C for 2 h and then cured at 180 °C for 2 h to obtain an electronic-grade flame-retardant epoxy resin composition.

[0090] Comparative Example 3

[0091] An electronic-grade flame-retardant epoxy resin composition, and the specific preparation method is as follows:

[0092] Under a nitrogen atmosphere, 28.55 parts of 4,4'-diaminodiphenyl sulfone (DDS) and 8.24 parts of Intermediate Ⅳ were added to a reactor and stirred evenly at 170 °C. Then, 100 parts of bisphenol A epoxy resin (DGEBA) and 0.5 part of o-hydroxybenzyldimethylamine (DMP-10) were added as a curing accelerator according to the formulation amount, and the mixture was stirred evenly to obtain a mixture. After evacuating for 15 min to exhaust air, it was poured into a polytetrafluoroethylene mold while it was still hot. It was first cured at 120 °C for 2 h and then cured at 180 °C for 2 h to obtain an electronic-grade flame-retardant epoxy resin composition.

[0093] Comparative Example 4

[0094] An electronic-grade flame-retardant epoxy resin composition, and the specific preparation method is as follows:

[0095] Under a nitrogen atmosphere, 28.55 parts of 4,4'-diaminodiphenyl sulfone (DDS) and 8.24 parts of Intermediate Ⅴ were added to a reactor and stirred evenly at 170 °C. Then, 100 parts of bisphenol A epoxy resin (DGEBA) and 0.5 part of o-hydroxybenzyldimethylamine (DMP-10) were added as a curing accelerator according to the formulation amount, and the mixture was stirred evenly to obtain a mixture. After evacuating for 15 min to exhaust air, it was poured into a polytetrafluoroethylene mold while it was still hot. It was first cured at 120 °C for 2 h and then cured at 180 °C for 2 h to obtain an electronic-grade flame-retardant epoxy resin composition.

[0096] Comparative Example 5

[0097] An electronic-grade flame-retardant epoxy resin composition, and the specific preparation method is as follows:

[0098] Under a nitrogen atmosphere, 28.55 parts of 4,4'-diaminodiphenyl sulfone (DDS) and 8.24 parts of intermediate VI were added to a reactor and stirred evenly at 170 °C. Then, 100 parts of bisphenol A epoxy resin (DGEBA) and 0.5 part of o-hydroxybenzyldimethylamine (DMP-10) were added as a curing accelerator according to the formulation amount, and the mixture was stirred evenly to obtain a mixture. After evacuating for 15 minutes to exhaust gas, it was poured into a polytetrafluoroethylene mold while it was still hot. It was first cured at 120 °C for 2 h and then cured at 180 °C for 2 h to obtain an electronic-grade flame-retardant epoxy resin composition.

[0099] Comparative Example 6

[0100] An electronic-grade flame-retardant epoxy resin composition, and the specific preparation method is as follows:

[0101] Under a nitrogen atmosphere, 28.55 parts of 4,4'-diaminodiphenyl sulfone (DDS) and 12.9 parts of traditional flame retardant ammonium polyphosphate (APP) were added to a reactor and stirred evenly at 170 °C. Then, 100 parts of bisphenol A epoxy resin (DGEBA) and 0.5 part of o-hydroxybenzyldimethylamine (DMP-10) were added as a curing accelerator according to the formulation amount, and the mixture was stirred evenly to obtain a mixture. After evacuating for 15 minutes to exhaust gas, it was poured into a polytetrafluoroethylene mold while it was still hot. It was first cured at 120 °C for 2 h and then cured at 180 °C for 2 h to obtain an electronic-grade flame-retardant epoxy resin composition.

[0102] Comparative Example 7

[0103] A flame-retardant phosphorus-containing epoxy resin material, and the specific preparation method is as follows:

[0104] Under a nitrogen atmosphere, 25.45 parts of 4,4'-diaminodiphenyl sulfone (DDS), 2.06 parts of intermediate V, and 6.18 parts of HY-2NH2 were added to a reactor and stirred evenly at 170 °C. Then, 100 parts of bisphenol A epoxy resin (DGEBA) and 0.5 part of o-hydroxybenzyldimethylamine (DMP-10) were added as a curing accelerator, and the mixture was stirred evenly to obtain a mixture. After evacuating for 15 minutes to exhaust gas, it was poured into a polytetrafluoroethylene mold while it was still hot. It was first cured at 120 °C for 2 h and then cured at 180 °C for 2 h to obtain an electronic-grade flame-retardant epoxy resin composition.

[0105] Performance test of Example 10

[0106] The above various flame-retardant phosphorus-containing epoxy resin materials were subjected to a flame-retardant performance test, and the results are shown in Tables 1 and 2.

[0107] Table 1 Flame-retardant performance test results of different flame-retardant phosphorus-containing epoxy resin materials

[0108]

[0109] Table 2 Test Results of Electronic Grade Flame Retardant Epoxy Resin Composition

[0110]

[0111] The flame retardant effect of the intumescent flame retardant system is closely related to the morphology of the surface carbon layer. The denser and more continuous the carbon layer is, the better it can play the role of heat insulation and oxygen isolation, and the shorter the extinguishing time of the sample will be. Figure 1 It is the SEM morphology diagram of the residual carbon after the vertical burning test of the sample (Comparative Example 5, ×500, ×2000; Example 7, ×500, ×2000). The carbon layer formed in Comparative Example 5 is loose and porous, while the surface carbon layer of Example 7 is relatively dense and continuous; and smaller pores will be formed on the surface, indicating an obvious gas-phase flame retardant phenomenon. The dense and continuous carbon layer can effectively inhibit the entry of oxygen and the escape of combustible gases. At the same time, due to the low thermal conductivity of the carbon layer, it can also effectively block the heat of the external flame, thus achieving excellent flame retardant effect.

[0112] As can be seen from Table 1 and Table 2, the novel phosphorus-nitrogen type flame retardant curing agent of the present invention is used to prepare an electronic-grade flame retardant epoxy resin composition with good flame retardant performance. From Comparative Example 1, it can be seen that the electronic-grade flame retardant epoxy resin composition without the addition of the phosphorus-nitrogen type flame retardant curing agent is prone to dripping and can be ignited (glass transition temperature is 173 °C, thermal decomposition temperature is 365 °C, thermal delamination time T260 is 120 °C, thermal delamination time T288 is 60 °C), while the electronic-grade flame retardant epoxy resin composition with a phosphorus content ≥ 0.1% after adding the phosphorus-nitrogen type flame retardant curing agent is not prone to dripping and cannot be ignited (glass transition temperature is 162-178 °C, thermal decomposition temperature is 351-369 °C, thermal delamination time T260 is above 140 °C, thermal delamination time T288 is above 68 °C). By precisely controlling the addition amount of PA-3NH2 (0.78-8.24 phr), the present invention significantly reduces the phosphorus consumption compared with the traditional APP flame retardant (12.9 phr is required to reach a phosphorus content of 2.8%). In Example 4, the technical effect is achieved when only 0.78 phr of PA-3NH2 is added, while 28.55 phr is required in the traditional APP system. The electronic-grade flame retardant epoxy resin composition prepared by using the novel phosphorus-nitrogen type flame retardant curing agent of the present invention has good flame retardant performance. As shown in the data in Table 2, it has the characteristics of low phosphorus and high efficiency: the LOI of the PA-3NH2 system reaches 31.5 ± 0.1% at a phosphorus content of 0.1%, far exceeding that of Comparative Example 2 (23.7 ± 0.1%), and passes the UL94 V-0 certification (t1 / t2 time ≤ 3.6 s, no dripping); it has the advantage of thermal reliability and high temperature stability. As shown in the data in Table 3: the T288 delamination time of the PA-3NH2 system reaches 73 ± 1 min (phosphorus content of 0.1%), which is 128% higher than that of the traditional flame retardant ammonium polyphosphate in Comparative Example 5 (21 ± 1 min). This shows that using the phosphorus-nitrogen type flame retardant curing agent prepared by the present invention to prepare the electronic-grade flame retardant epoxy resin composition can reduce the amount of flame retardant in the electronic-grade flame retardant epoxy resin composition and does not affect the corresponding performance.

[0113] The mechanism by which the electronic-grade flame retardant epoxy resin composition can be flame retarded by using the phosphorus-nitrogen type flame retardant curing agent of the present invention is as follows:

[0114]

[0115] Wherein It means:

[0116]

[0117] In summary, the present invention discloses a phosphorus-nitrogen type flame retardant curing agent, which has the following advantages: directly connecting a phosphorus-containing bio-based polyamine to the molecular chain of the material, improving the flame retardant efficiency, eliminating the problem of flame retardant precipitation, and being able to enhance the flame retardant performance and the thermal delamination time of the electronic adhesive. In addition, the phosphorus-nitrogen type flame retardant curing agent can react with thermosetting resins such as epoxy resin and phenolic resin, efficiently retard fire, can self-crosslink and expand into carbon, and crosslink with the pyrolysis small molecules of the polymer material at high temperature to generate a carbon layer with high thermal stability, belonging to intrinsic flame retardancy. The phosphorus-nitrogen type flame retardant curing agent of the present invention is halogen-free and environmentally friendly, and the synthetic monomers are widely sourced.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. Phosphorus-nitrogen type flame retardant curing agent, characterized in that: The phosphorus-nitrogen type flame retardant curing agent is a compound of structural formula I, and the structural formula I is: ， wherein R1 to R 10 is a compound of Structural Formula II containing 0 to 6 numbers, and the rest is NH4 + ; the Structural Formula II is: wherein R 11 , R 12 are simultaneously any one of methyl, ethyl or isopropyl.

2. The preparation method of the phosphazene-based flame retardant curing agent according to claim 1, characterized in that, The preparation method includes the following steps: (1) Dissolve phytic acid and urea in water, place them in a reaction kettle, heat and then carry out condensation reflux for reaction, and obtain the intermediate of structural formula III after purification and drying; (2) Add HY-2NH2 into a flask equipped with a condensation device, dissolve it with an organic solvent, add the intermediate for reaction after heating and dissolving, remove the solvent and then carry out drying under reduced pressure and heating to obtain the phosphorus-nitrogen type flame retardant curing agent. The structural formula Ⅲ is as follows: Wherein R 13 ~R 24 includes 2 to 8 H atoms + , and the rest are NH4 + ; The structural formula of HY-2NH2 is as follows: R 11 and R 12 are each independently any one of methyl, ethyl or isopropyl.

3. The preparation method according to claim 2, characterized in that: In step (1), the molar ratio of phytic acid to urea is 1:1 to 7.

4. The preparation method according to claim 2, characterized in that: In step (1), the specific operation of heating and then carrying out condensation reflux is: heat to 60-150 °C and carry out condensation reflux reaction for 20-200 min.

5. The preparation method according to claim 2, wherein: In step (1), the organic solvent is any one of toluene, xylene, tetrahydrofuran, acetone, ethanol or isopropanol.

6. The preparation method according to claim 2, characterized in that: In step (2), the molar ratio of HY-2NH2 to the intermediate is 2-7:

1.

7. The preparation method according to claim 2, characterized in that: In step (2), the temperature of heating and dissolving is 30 °C to 100 °C.

8. The preparation method according to claim 2, characterized in that: In step (2), the temperature when adding the intermediate is 25 °C to 150 °C, and the reaction time is 1 h to 10 h.

9. The preparation method according to claim 2, characterized in that: In step (2), the specific operation of drying under reduced pressure and heating is: carry out drying under a negative pressure of 0.01-0.1 MPa at a temperature of 90 °C to 180 °C.

10. Use of the phosphorus-nitrogen type flame retardant curing agent according to claim 1 in the preparation of an electronic grade flame retardant epoxy resin composition.

11. An electronic-grade flame-retardant epoxy resin composition, characterized in that: By weight, the electronic grade flame retardant epoxy resin composition includes 60-100 parts of electronic grade epoxy resin, 10-50 parts of a curing agent mixture containing the phosphorus-nitrogen type flame retardant curing agent according to claim 1, and 0.1-3 parts of a curing accelerator.

12. The electronic-grade flame-retardant epoxy resin composition according to claim 11, wherein: The electronic grade epoxy resin includes at least one of electronic grade bisphenol A epoxy resin, phenolic epoxy resin, o-cresol novolac epoxy resin or hydrogenated bisphenol A epoxy resin.

13. The electronic-grade flame-retardant epoxy resin composition according to claim 11, wherein: The curing accelerator is at least one of triphenylphosphine, boron trifluoride ethylamine complex, 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, triethylenetetramine triethylamine, triethanolamine, o-hydroxybenzyldimethylamine, 4-nonylphenol, N-aminoethylpiperazine or ethyl levulinate.

14. The electronic-grade flame-retardant epoxy resin composition according to claim 11, wherein: The curing agent mixture further includes any one or several of 4,4'-diaminodiphenylmethane, benzyldimethylamine, m-phenylenediamine, N,N-dimethylbenzylamine, 4,4'-diaminodiphenylsulfone, adipic dihydrazide, salicylic hydrazide, succinic hydrazide, phthalic anhydride, methylhexahydrophthalic anhydride, trimellitic anhydride, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-tolylimidazole, 2-phenyl-4-methylimidazole, dicyandiamide, o-tolylbiguanide, p-tolylbiguanide, polyhexamethylenebiguanide or N-methylpiperazine.

15. The preparation method of the electronic-grade flame-retardant epoxy resin composition according to claim 11, characterized in that, The preparation method includes the following steps: Under a nitrogen atmosphere, add the curing agent mixture containing the phosphorus-nitrogen type flame retardant curing agent according to claim 14 into a reactor, stir and dissolve it, then sequentially add the electronic grade epoxy resin and the curing accelerator, mix and stir, evacuate and exhaust, and place it in a mold for curing to obtain the electronic grade flame retardant epoxy resin composition.

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