A novel phosphorus-containing amine heat-resistant epoxy curing agent, a preparation method and application thereof

Abstract

The application provides a phosphorus-containing amine curing agent, which has a structure as shown in formula (I). The phosphorus-containing amine curing agent with a specific structure and composition is a long-chain phosphorus-containing amine heat-resistant epoxy curing agent. The application introduces nitrogen elements through isocyanate groups after the reaction of DOPO and isocyanate, and further introduces a bismaleimide structure, thereby obtaining a phosphorus-containing amine heat-resistant epoxy curing agent with excellent heat resistance and taking amine groups as active groups. The phosphorus in the curing agent is not easy to precipitate, and the curing agent has excellent compatibility with epoxy resins; meanwhile, the curing agent contains amine groups, and does not need to add amine curing agents additionally; and the nitrogen elements are fixed on long chains, are more stable, and have better compatibility. Further, the curing agent contains a maleimide group, so that the cured product has excellent heat resistance.

Description

Technical Field

[0001] This invention belongs to the technical field of epoxy resin flame retardant curing agents, and relates to a phosphorus-amine-containing curing agent, its preparation method and application, and in particular to a novel phosphorus-amine-containing heat-resistant epoxy curing agent, its preparation method and application. Background Technology

[0002] In traditional epoxy resin flame retardant technology, halogen compounds (tetrabromobisphenol A) are widely used in electronic materials requiring flame retardant properties due to their excellent flame retardancy. However, halogen flame retardants release corrosive, toxic, and carcinogenic substances such as hydrogen bromide, tetrabromodiphenyl dioxin, and tetrabromodiphenyl benzofuran during combustion, and have been gradually banned by environmental regulations. From an environmental perspective, phosphorus-based flame retardants are now the better choice in flame retardant systems.

[0003] Currently, phosphorus-based flame retardants mostly use phosphate esters or 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) compounds. When used as epoxy resin curing agents, they need to be supplemented with dicyandiamide curing agents to formulate the epoxy resin adhesive, resulting in a phosphorus-containing flame-retardant epoxy resin system. Furthermore, phenolic or modified phenolic resins are often reacted with DOPO or DOPO-like compounds to obtain hydroxyl-containing compounds. During curing, the hydroxyl groups act as active groups, reacting with the epoxy resin to form a network cross-linked resin. However, this approach can negatively impact the overall performance of the prepared epoxy resin material.

[0004] Therefore, finding a more suitable flame-retardant curing agent to further guarantee or improve the overall performance of epoxy resin materials has become one of the urgent problems to be solved by many leading researchers and scientific research enterprises in this field. Summary of the Invention

[0005] In view of this, the present invention provides a phosphorus-amine-containing curing agent, its preparation method, and its application, particularly a novel phosphorus-amine-containing heat-resistant epoxy curing agent. The phosphorus-amine-containing heat-resistant epoxy curing agent provided by the present invention uses amine groups as active groups, has a high nitrogen content, exhibits good synergistic flame-retardant effect with phosphorus, and possesses better compatibility and stability. Furthermore, it effectively improves heat resistance, further enhancing the overall performance of epoxy resin materials. Moreover, the preparation method is simple, the conditions are mild, and the controllability is good, making it more conducive to industrial-scale production and widespread application.

[0006] This invention provides a phosphorus-amine-containing curing agent having a structure as shown in formula (I):

[0007]

[0008] Wherein, R is selected from

[0009] R1 is selected from

[0010] R2 is selected from

[0011] Preferably, the phosphorus-amine curing agent includes a phosphorus-amine phenolic curing agent;

[0012] The active groups of the phosphorus-containing amine curing agent include amine groups;

[0013] The phosphorus-containing amine curing agent contains a bismaleimide structure.

[0014] Preferably, the phosphorus-amine curing agent is a curing agent used for epoxy resins;

[0015] When the phosphorus-containing amine curing agent is used for epoxy resin curing, there is no need to use other amine curing agents;

[0016] The phosphorus-containing amine curing agent is a phosphorus-containing amine curing agent with flame retardant effect.

[0017] Preferably, the flame retardant effect is a nitrogen-phosphorus synergistic flame retardant effect;

[0018] The ratio of the phosphorus-containing amine curing agent to the epoxy resin is (0.5-3.5):1;

[0019] The epoxy resin prepared by the phosphorus-amine curing agent has a Tg greater than 200℃.

[0020] The epoxy resin includes epoxy resin used in epoxy resin copper clad laminates.

[0021] This invention provides a method for preparing a phosphorus-amine curing agent, comprising the following steps:

[0022] 1) After mixing DOPO organic solution, catalyst, isocyanate and organic solvent, the reaction is carried out to obtain intermediate solution;

[0023] 2) The intermediate solution obtained in the above steps is reacted with diamine again to obtain the reaction solution;

[0024] 3) After refluxing the reaction solution obtained in the above steps with bismaleimide compounds, a phosphorus-amine curing agent is obtained.

[0025] Preferably, the solvent of the DOPO organic solution includes one or more of toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, and cyclohexanone;

[0026] The catalyst includes one or more of imidazole compounds, quaternary ammonium salt compounds, and triphenylphosphine compounds;

[0027] The isocyanate includes one or more of diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, phenyl diisocyanate, and isophorone diisocyanate;

[0028] The organic solvent includes one or more of toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, and cyclohexanone;

[0029] The molar ratio of DOPO to isocyanate is (0.8–1.2):1.

[0030] Preferably, the catalyst accounts for 0.05 wt% to 0.2 wt% of the total mass of the DOPO and isocyanate;

[0031] The reaction temperature is 150–190°C;

[0032] The reaction time is 2-3 hours;

[0033] The specific mixing method involves premixing the catalyst and isocyanate to obtain a solution, and then adding the DOPO organic solution dropwise into the solution for mixing.

[0034] The dripping time is 1–3 hours;

[0035] The temperature at which the drops are added is 150–190°C.

[0036] Preferably, the catalyst comprises tetrabutylammonium bromide;

[0037] The molar ratio of DOPO to diamine is (0.8–1.2):1;

[0038] The diamine includes one or more of phenylenediamine, 4,4'-diamino-3,3'-dimethylbiphenyl, diaminodiphenylmethane, diaminodiphenyl sulfone, bisphenol A type diether diamine, and 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane;

[0039] The temperature for the second reaction is 110–130°C;

[0040] The time for the second reaction is 4 to 6 hours.

[0041] Preferably, the molar ratio of DOPO to the bismaleimide compound is (0.8–1.2):1;

[0042] The bismaleimide compounds include one or more of the following: DDM-modified bismaleimide, DDS-modified bismaleimide, 4,4'-diamino-3,3'-dimethylbiphenyl-modified bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane-modified bismaleimide, and bisphenol A type diether diamine-modified bismaleimide.

[0043] The reflux reaction temperature is 110–140°C;

[0044] The reflux reaction time is 1–4 hours;

[0045] The reflux reaction is followed by a process of heating to remove the solvent and / or dissolving the solvent.

[0046] The present invention also provides the application of a phosphorus-amine curing agent as described in any one of the above technical solutions or a phosphorus-amine curing agent prepared by any one of the above technical solutions in the preparation of epoxy resin copper clad laminates.

[0047] This invention provides a phosphorus-containing amine curing agent having the structure shown in formula (I). Compared with the prior art, this invention addresses the problem of existing phosphorus-based flame retardant curing agents affecting the overall performance of epoxy resin systems. While it is possible to improve the flame retardant effect and maintain the overall performance of the epoxy resin system through nitrogen-phosphorus synergy (e.g., by adding Dicy, or, as in patent CN103755925, by reacting phenolic resin with DOPO after etherification to obtain a phosphorus-containing phenolic curing agent, with the addition of nitrogen-containing additives such as melamine or acetylguanidine during the reaction to introduce nitrogen), this invention argues that this method of introducing nitrogen by adding additional nitrogen compounds is not only cumbersome in process, but also limited in dosage, resulting in a low nitrogen content and limited improvement in overall performance. Furthermore, these small-molecule nitrogen compounds also have defects in compatibility and stability.

[0048] Based on this, the present invention specifically designs a phosphorus-amine curing agent with a specific structure and composition, which is a novel long-chain phosphorus-amine heat-resistant epoxy curing agent. The synthesized curing agent uses amine groups as active groups, has a high nitrogen content, and exhibits better synergistic flame-retardant effect with phosphorus. Moreover, nitrogen is located on the main chain of the long-chain curing agent, which has better compatibility and stability. At the same time, it contains maleimide groups, which give the cured product excellent heat resistance, further improving the overall performance of epoxy resin, such as heat resistance, during application.

[0049] This invention reacts isocyanate as an initial raw material with DOPO, making it easier for DOPO to bind within the resin to obtain a phosphorus-containing aldehyde compound. This compound then reacts with a diamine to obtain a phosphorus-containing amine curing agent. Finally, it reacts again with modified bismaleimide to obtain a heat-resistant curing agent containing phosphorus-amine and modified bismaleimide groups. This invention introduces nitrogen through isocyanate facilitation after the reaction of DOPO with isocyanate, and further introduces a bismaleimide structure, resulting in a phosphorus-containing amine heat-resistant epoxy curing agent with amine groups as active groups and excellent heat resistance. This invention changes the existing phosphorus-containing curing agents, which all use hydroxyl groups as active groups, by introducing amine groups as epoxy curing groups. Furthermore, the phosphorus in this curing agent is less prone to precipitation and has excellent compatibility with epoxy resins. Simultaneously, the presence of amine groups eliminates the need for additional amine curing agents during epoxy resin curing, and the nitrogen element is fixed on a long chain, making it more stable and improving compatibility. Furthermore, the presence of maleimide groups in this curing agent gives the cured product excellent heat resistance. This invention increases the proportion of nitrogen in nitrogen-phosphorus curing agents, resulting in a better synergistic effect of nitrogen and phosphorus in flame retardancy. This better achieves the flame retardant effect of nitrogen-phosphorus blending in epoxy curing systems. More importantly, the prepared epoxy resin system exhibits excellent performance in key properties such as solder resistance, peel strength, and thermal weight loss, especially in heat resistance, with a high glass transition temperature.

[0050] The phosphorus-amine heat-resistant epoxy curing agent provided by this invention uses amine groups as active groups, has a high nitrogen content, and exhibits good synergistic flame retardant effect with phosphorus. Moreover, when applied to epoxy resin systems, it significantly improves the heat resistance of the system and has excellent comprehensive properties such as solder resistance, peel strength, and thermal weight loss. At the same time, the preparation method is simple, the conditions are mild, and the controllability is good, which is more conducive to industrial-scale production and promotion.

[0051] Experimental results show that the phosphorus-amine-containing heat-resistant epoxy curing agent synthesized in this invention, when applied to epoxy resin copper-clad laminates, achieves a flame retardant effect reaching UL-94V-0 level. Furthermore, the main properties of the laminate, such as solder resistance, peel strength, and thermal weight loss, all meet or exceed the levels of commercially available products, especially the glass transition temperature T0. g ≥210℃. Detailed Implementation

[0052] To further understand the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0054] There are no particular restrictions on the purity of any of the raw materials used in this invention. However, it is preferred to use analytical grade or conventional purity in the field of epoxy resin curing agent preparation.

[0055] This invention provides a phosphorus-amine-containing curing agent having a structure as shown in formula (I):

[0056]

[0057] Wherein, R is selected from

[0058] R1 is selected from

[0059] R2 is selected from

[0060] In this invention, the phosphorus-amine curing agent preferably includes a phosphorus-amine phenolic curing agent.

[0061] In this invention, the active groups of the phosphorus-containing amine curing agent preferably include amine groups.

[0062] In this invention, the phosphorus-amine curing agent package preferably contains a bismaleimide structure.

[0063] In this invention, the phosphorus-amine curing agent is preferably a curing agent for epoxy resins.

[0064] In this invention, when the phosphorus-containing amine curing agent is used for epoxy resin curing, other amine curing agents may not be used.

[0065] In this invention, the phosphorus-amine curing agent is preferably a phosphorus-amine curing agent with flame retardant effect.

[0066] In this invention, the flame retardant effect is preferably a nitrogen-phosphorus synergistic flame retardant effect.

[0067] In this invention, the preferred ratio of the phosphorus-containing amine curing agent to the epoxy resin is (0.5–3.5):1, more preferably (1.0–3.0):1, and even more preferably (1.5–2.5):1. Specifically, in this invention, the amount of phosphorus-containing amine curing agent is preferably such that the phosphorus content of the system is 1.5 wt%–3.0 wt%, or 1.7 wt%–2.8 wt%, or 2.0 wt%–2.5 wt%. The system preferably includes epoxy resin, additives, and fillers, but excludes solvents, and excludes fibers relative to the final epoxy resin copper-clad laminate.

[0068] In this invention, the epoxy resin prepared by the phosphorus-amine curing agent preferably has a Tg greater than 200°C, more preferably greater than 210°C, and even more preferably greater than 220°C.

[0069] In this invention, the epoxy resin preferably includes epoxy resin used for epoxy resin copper clad laminates.

[0070] This invention provides a method for preparing a phosphorus-amine curing agent, comprising the following steps:

[0071] 1) After mixing DOPO organic solution, catalyst, isocyanate and organic solvent, the reaction is carried out to obtain intermediate solution;

[0072] 2) The intermediate solution obtained in the above steps is reacted with diamine again to obtain the reaction solution;

[0073] 3) After refluxing the reaction solution obtained in the above steps with bismaleimide compounds, a phosphorus-amine curing agent is obtained.

[0074] The present invention first mixes DOPO organic solution, catalyst, isocyanate and organic solvent and then reacts them to obtain intermediate solution.

[0075] In this invention, the solvent of the DOPO organic solution preferably includes one or more of toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, and cyclohexanone, more preferably toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, or cyclohexanone.

[0076] In this invention, the catalyst preferably includes one or more of imidazole compounds, quaternary ammonium salt compounds, and triphenylphosphine compounds, more preferably imidazole compounds, quaternary ammonium salt compounds, or triphenylphosphine compounds.

[0077] In this invention, the isocyanate preferably includes one or more of diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, phenyl dimethyl diisocyanate, and isophorone diisocyanate, more preferably diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, phenyl dimethyl diisocyanate, or isophorone diisocyanate.

[0078] In this invention, the organic solvent preferably includes one or more of toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, and cyclohexanone, more preferably toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, or cyclohexanone.

[0079] In this invention, the catalyst accounts for 0.05 wt% to 0.2 wt% of the total mass of DOPO and isocyanate, more preferably 0.08 wt% to 0.17 wt%, and even more preferably 0.11 wt% to 0.14 wt%.

[0080] In this invention, the molar ratio of DOPO to isocyanate is preferably (0.8-1.2):1, more preferably (0.85-1.15):1, more preferably (0.9-1.1):1, and even more preferably (0.95-1.05):1.

[0081] In this invention, the reaction temperature is preferably 150-190°C, more preferably 155-185°C, even more preferably 160-180°C, and even more preferably 165-175°C, thereby better suppressing isocyanate self-polymerization.

[0082] In this invention, the reaction time is preferably 2 to 3 hours, more preferably 2.2 to 2.8 hours, and even more preferably 2.4 to 2.6 hours.

[0083] In this invention, the preferred mixing method is to premix the catalyst and isocyanate to obtain a solution, and then add the DOPO organic solution dropwise to the solution for mixing.

[0084] In this invention, the dripping time is preferably 1 to 3 hours, more preferably 1.4 to 2.6 hours, and even more preferably 1.8 to 2.2 hours.

[0085] In this invention, the dropping is preferably performed at the reaction temperature. That is, the dropping temperature is preferably 150-190°C, more preferably 155-185°C, even more preferably 160-180°C, and even more preferably 165-175°C.

[0086] In this invention, the intermediate solution obtained in the above steps is reacted again with diamine to obtain a reaction solution.

[0087] In this invention, the diamine preferably includes one or more of phenylenediamine, 4,4'-diamino-3,3'-dimethylbiphenyl, diaminodiphenylmethane, diaminodiphenyl sulfone, bisphenol A type diether diamine, and 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, more preferably phenylenediamine, 4,4'-diamino-3,3'-dimethylbiphenyl, diaminodiphenylmethane (DDM), diaminodiphenyl sulfone (DDS), bisphenol A type diether diamine, or 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane.

[0088] In this invention, the molar ratio of DOPO to diamine is preferably (0.8-1.2):1, more preferably (0.85-1.15):1, even more preferably (0.9-1.1):1, and even more preferably (0.95-1.05):1.

[0089] In this invention, the temperature of the second reaction is preferably 110-130°C, more preferably 115-125°C, and even more preferably 119-121°C.

[0090] In this invention, the time for the second reaction is preferably 4 to 6 hours, more preferably 4.4 to 5.6 hours, and even more preferably 4.8 to 5.2 hours.

[0091] Finally, the reaction solution obtained in the above steps is refluxed with a bismaleimide compound to obtain a phosphorus-amine curing agent.

[0092] In this invention, the molar ratio of DOPO to the bismaleimide compound is preferably (0.8–1.2):1, more preferably (0.85–1.15):1, even more preferably (0.9–1.1):1, and even more preferably (0.95–1.05):1.

[0093] In this invention, the bismaleimide compounds preferably include one or more of the following: DDM-modified bismaleimide (DDM-BMI), DDS-modified bismaleimide (DDS-BMI), 4,4'-diamino-3,3'-dimethylbiphenyl-modified bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane-modified bismaleimide, and bisphenol A type diether diamine-modified bismaleimide; more preferably, they are DDM-modified bismaleimide, DDS-modified bismaleimide, 4,4'-diamino-3,3'-dimethylbiphenyl-modified bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane-modified bismaleimide, or bisphenol A type diether diamine-modified bismaleimide.

[0094] In this invention, the temperature of the reflux reaction is preferably 110-140°C, more preferably 115-135°C, and even more preferably 120-130°C.

[0095] In this invention, the reflux reaction time is preferably 1 to 4 hours, more preferably 1.5 to 3.5 hours, and even more preferably 2 to 3 hours.

[0096] In this invention, the reflux reaction preferably includes a step of heating to remove the solvent and / or dissolving, more preferably a step of heating to remove the solvent or dissolving.

[0097] To complete and refine the overall technical solution, this invention further ensures the structure and composition of the phosphoamine-containing curing agent, better improves its flame retardant properties, curing effect, and system stability, and further enhances the overall performance of the subsequent epoxy resin system, including its heat resistance. The preferred methods for preparing the aforementioned phosphoamine-containing curing agent and its preparation method are as follows:

[0098] The novel phosphorus-amine phenolic curing agent synthesized in this invention has an active group of amine and contains a bismaleimide structure.

[0099] 1. DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) reacts with isocyanate to give DOPO-R-CHO.

[0100] At a certain temperature, a DOPO / toluene solution is dropped into an isocyanate (or isocyanate solution) containing a catalyst.

[0101] Specifically, isocyanates include, but are not limited to, diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), naphthalene diisocyanate (NDI), hexamethylene diisocyanate (HDI), m-phenylenedimethyl isocyanate (XDI), and isophorone diisocyanate (IPDI), with MDI being preferred.

[0102] Specifically, catalysts commonly used include imidazole compounds, quaternary ammonium salts, and triphenylphosphine compounds, with tetrabutylammonium bromide being a preferred quaternary ammonium salt.

[0103] The reaction formulas for the above steps are shown below:

[0104]

[0105] 2. DOPO-R-CHO reacts with diamine to synthesize phosphorus-containing amine curing agents.

[0106] Specifically, the diamines include, but are not limited to, phenylenediamine, 4,4'-diamino-3,3'-dimethylbiphenyl, diaminodiphenylmethane (DDM), diaminodiphenyl sulfone (DDS), bisphenol A type diether diamine, and 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, more preferably 4,4'-diamino-3,3'-dimethylbiphenyl. Among these, amines with a methyl or ethyl group on the benzene ring contribute to improving the dielectric properties of the resin.

[0107] The reaction formulas for the above steps are shown below:

[0108]

[0109] 3. The introduction of bismaleimide (BMI) further increases the glass transition temperature of the cured resin, improving the heat resistance of the board. Bismaleimide can be DDM-BMI, DDS-BMI, or other bismaleimide compounds containing benzene rings or heterocycles.

[0110] The reaction formulas for the above steps are shown below:

[0111]

[0112] This invention provides the application of a phosphorus-amine curing agent as described in any one of the above technical solutions, or a phosphorus-amine curing agent prepared by any one of the above technical solutions, in the preparation of epoxy resin copper clad laminates.

[0113] This invention provides a halogen-free copper-clad laminate, comprising, by weight of raw materials:

[0114]

[0115] Specifically, the phosphorus-containing bismaleimide curing agent of the present invention is a phosphorus-containing bismaleimide curing agent having the structure shown in formula (I).

[0116] In this invention, the amount of epoxy resin added is 90 to 110 parts by weight, which can be 94 to 106 parts by weight, preferably 98 to 102 parts by weight.

[0117] In this invention, the amount of the phosphorus-containing bismaleimide curing agent added is 100-300 parts by weight, which can be 140-260 parts by weight, and preferably 180-220 parts by weight.

[0118] In this invention, the amount of the accelerator added is 0.5 to 5 parts by weight, which can be 1.5 to 4 parts by weight, and preferably 2.5 to 3 parts by weight.

[0119] In this invention, the amount of solvent added is 300-700 parts by weight, which can be 350-650 parts by weight, preferably 400-600 parts by weight, and more preferably 450-550 parts by weight.

[0120] In this invention, the amount of inorganic filler added is 150-400 parts by weight, which can be 200-350 parts by weight, and preferably 250-300 parts by weight.

[0121] In this invention, the molar ratio of active hydrogen (hydrogen atoms connected to N) to epoxy groups on the phosphorus-amine curing agent is preferably (0.95-1.2):1, more preferably (1.00-1.15):1, and even more preferably (1.05-1.10):1.

[0122] In this invention, the amount of accelerator is preferably 0.05wt% to 0.2wt% of the total weight of the resin system, more preferably 0.07wt% to 0.18wt%, and even more preferably 0.1wt% to 0.15wt%.

[0123] In this invention, the mass ratio of the inorganic filler to the resin system is preferably (0.2-0.4):1, more preferably (0.23-0.38):1, and even more preferably (0.25-0.35):1.

[0124] In this invention, the amount of solvent used is preferably such that the solid content of the raw material slurry is between 55% and 65%, more preferably 57% to 63%, and even more preferably 59% to 61%.

[0125] In this invention, the resin system preferably includes epoxy resin, additives (curing agent and accelerator) and filler, but excludes solvent. The final epoxy resin copper clad laminate does not include fibers, and the raw material slurry is the sum of the resin system and solvent.

[0126] In this invention, the epoxy resin preferably includes one or more of bisphenol A type epoxy resin, phenolic epoxy resin, o-cresol epoxy resin, bisphenol A phenolic epoxy resin, and bisphenol F epoxy resin, more preferably bisphenol A type epoxy resin, phenolic epoxy resin, o-cresol epoxy resin, bisphenol A phenolic epoxy resin, or bisphenol F epoxy resin. Specifically, the epoxy resin in this invention can be a phenolic epoxy resin.

[0127] In this invention, the accelerator preferably includes one or more of 2-methylimidazole, imidazole, 2-ethyl-4-methylimidazole and 2,4-dimethylimidazole, more preferably 2-methylimidazole, imidazole, 2-ethyl-4-methylimidazole or 2,4-dimethylimidazole.

[0128] In this invention, the solvent preferably includes one or more of DMF, cyclohexanone, acetone, butanone, and propylene glycol methyl ether, more preferably DMF, cyclohexanone, acetone, butanone, or propylene glycol methyl ether.

[0129] In this invention, the inorganic filler preferably includes one or more of silicon dioxide, silicon micro powder, mica powder, magnesium hydroxide, aluminum hydroxide, and magnesium hydroxide, and more preferably silicon dioxide, silicon micro powder, mica powder, magnesium hydroxide, aluminum hydroxide, or magnesium hydroxide.

[0130] In this invention, the phosphorus-containing bismaleimide curing agent preferably includes a phosphorus-containing phenolic curing agent.

[0131] In this invention, the active group of the phosphorus-containing bismaleimide curing agent preferably includes an amine group.

[0132] In this invention, the raw materials preferably also include glass fiber cloth.

[0133] In this invention, the phosphorus-containing bismaleimide curing agent preferably contains a bismaleimide structure.

[0134] In this invention, the phosphorus-containing bismaleimide curing agent is preferably a curing agent for epoxy resins.

[0135] In this invention, the raw materials preferably do not contain other amine curing agents.

[0136] In this invention, the Tg of the epoxy resin cured product prepared by the phosphorus-amine bismaleimide curing agent is preferably greater than 200°C, more preferably greater than 210°C, more preferably greater than 220°C, and more preferably greater than 230°C.

[0137] In this invention, the phosphorus-containing bismaleimide curing agent is preferably a phosphorus-containing bismaleimide curing agent with flame retardant effect.

[0138] In this invention, the flame retardant effect is preferably a nitrogen-phosphorus synergistic flame retardant effect.

[0139] The present invention describes a novel phosphorus-amine-containing heat-resistant epoxy curing agent, its preparation method, and its application. This invention specifically designs a phosphorus-amine-containing curing agent with a specific structure and composition, which is a novel long-chain phosphorus-amine-containing heat-resistant epoxy curing agent. The synthesized curing agent uses amine groups as active groups, has a high nitrogen content, and exhibits better synergistic flame-retardant effect with phosphorus. Furthermore, the nitrogen element, located on the main chain of the long-chain curing agent, demonstrates better compatibility and stability. Simultaneously, the presence of maleimide groups gives the cured product excellent heat resistance, further enhancing the overall performance of the epoxy resin in application, including its heat resistance.

[0140] This invention reacts isocyanate as an initial raw material with DOPO, making it easier for DOPO to bind within the resin to obtain a phosphorus-containing aldehyde compound. This compound then reacts with a diamine to obtain a phosphorus-containing amine curing agent. Finally, it reacts again with modified bismaleimide to obtain a heat-resistant curing agent containing phosphorus-amine and modified bismaleimide groups. This invention introduces nitrogen through isocyanate facilitation after the reaction of DOPO with isocyanate, and further introduces a bismaleimide structure, resulting in a phosphorus-containing amine heat-resistant epoxy curing agent with amine groups as active groups and excellent heat resistance. This invention changes the existing phosphorus-containing curing agents, which all use hydroxyl groups as active groups, by introducing amine groups as epoxy curing groups. Furthermore, the phosphorus in this curing agent is less prone to precipitation and has excellent compatibility with epoxy resins. Simultaneously, the presence of amine groups eliminates the need for additional amine curing agents during epoxy resin curing, and the nitrogen element is fixed on a long chain, making it more stable and improving compatibility. Furthermore, the presence of bismaleimide groups in this curing agent gives the cured product excellent heat resistance. This invention increases the proportion of nitrogen in nitrogen-phosphorus curing agents, resulting in a better synergistic effect of nitrogen and phosphorus in flame retardancy. This better achieves the flame retardant effect of nitrogen-phosphorus blending in epoxy curing systems. More importantly, the prepared epoxy resin system exhibits excellent performance in key properties such as solder resistance, peel strength, and thermal weight loss, especially in heat resistance, with a high glass transition temperature.

[0141] The phosphorus-amine heat-resistant epoxy curing agent provided by this invention uses amine groups as active groups, has a high nitrogen content, and exhibits good synergistic flame retardant effect with phosphorus. Moreover, when applied to epoxy resin systems, it significantly improves the heat resistance of the system and has excellent comprehensive properties such as solder resistance, peel strength, and thermal weight loss. At the same time, the preparation method is simple, the conditions are mild, and the controllability is good, which is more conducive to industrial-scale production and promotion.

[0142] Experimental results show that the phosphorus-amine-containing heat-resistant epoxy curing agent synthesized in this invention, when applied to epoxy resin copper-clad laminates, achieves a flame retardant effect reaching UL-94V-0 level. Furthermore, the main properties of the laminate, such as solder resistance, peel strength, and thermal weight loss, all meet or exceed the levels of commercially available products, especially the glass transition temperature T0. g ≥210℃.

[0143] To further illustrate the present invention, the following detailed description of a phosphorus-amine curing agent, its preparation method, and its application is provided in conjunction with embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are given only to further illustrate the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0144] Example 1

[0145] 216 g of DOPO (toluene solution) was added dropwise to 250 g of liquefied diphenylmethane diisocyanate (MDI) containing a catalyst at 170 °C for 1 hour. After the addition was complete, the reaction was continued for 2–3 hours. 197 g of 4,4'-diamino-3,3'-dimethylbiphenyl was added to the resulting product, and the mixture was refluxed at 115–125 °C for 4 hours. 358 g of DDM-BMI was added to the resulting reaction solution, and the mixture was refluxed at 120 °C for 4–5 hours. The temperature was then raised to 130 °C and atmospheric pressure to remove toluene. The mixture was then cooled to 100 °C and dissolved in cyclohexanone to obtain a curing agent (H-1) containing a bismaleimide structure.

[0146]

[0147] Phosphoamine curing agent containing a bismaleimide structure (H-1)

[0148] Example 2

[0149] 210g of naphthalene diisocyanate was added to a reaction flask and heated to melt. After complete melting, the catalyst was added and mixed thoroughly. 216g of DOPO / toluene solution was added dropwise over 1 hour at 170°C, and the reaction continued for 2-3 hours after the addition was complete. 406g of bisphenol A type diether diamine was added to the obtained product, and the mixture was refluxed at 115-125°C for 4 hours. 442g of DDM-BMI was added to the resulting reaction solution, and the mixture was refluxed at 120°C for 6-8 hours. The temperature was then raised to 130°C and atmospheric pressure to remove toluene. The mixture was then cooled to 100°C and cyclohexanone was added to dissolve the toluene, yielding a phosphorus-amine curing agent (H-2) containing a bismaleimide structure.

[0150]

[0151] Phosphoamine curing agent containing a bismaleimide structure (H-2)

[0152] Example 3

[0153] 210g of naphthalene diisocyanate was added to a reaction flask and heated to melt. After complete melting, the catalyst was added and mixed thoroughly. 216g of DOPO / toluene solution was added dropwise over 1 hour at 170°C, and the reaction continued for 2-3 hours after the addition was complete. 197g of 4,4'-diamino-3,3'-dimethylbiphenyl was added to the obtained product, and the mixture was refluxed at 115-125°C for 4 hours. 442g of DDM-BMI was added to the resulting reaction solution, and the mixture was refluxed at 120°C for 6-8 hours. The temperature was then raised to 130°C and atmospheric pressure to remove toluene. The mixture was then cooled to 100°C and cyclohexanone was added to dissolve the toluene, yielding a phosphorus-amine curing agent (H-3) containing a bismaleimide structure.

[0154]

[0155] Phosphoamine curing agent containing a bismaleimide structure (H-3)

[0156] Performance testing:

[0157] The three phosphorus-containing amine curing agents obtained in Examples 1, 2, and 3, the phosphorus-containing curing agent (Dow XZ-92741) of the comparative example, and the epoxy resin (a mixture of NPEL128 and NPPN638 in a mass ratio of 1:1) were mixed at an equivalent ratio of 1:1. 1000 ppm of curing accelerator (2-methylimidazole) and 50% of the resin weight of filler (aluminum hydroxide) were added. Then, solvent (toluene) was added until the solid content of the mixture was 60%. The mixture was stirred evenly to obtain the resin composition adhesive.

[0158] Next, the glass cloth is impregnated with the resin composition solution, and then the impregnated glass is placed in an oven at 150°C for 5 minutes to form a semi-cured sheet. Eight semi-cured sheets are stacked together, and an electrolytic copper foil is superimposed on each of the top and bottom sides. The sheets are then pressed in a vacuum hot press to obtain a copper-clad laminate under the following conditions: pressure of 25 kg / cm². 2 Press at 220℃ for 2 hours.

[0159] The copper-clad laminates prepared in the embodiments and comparative examples of the present invention were tested.

[0160] See Table 1, which shows the performance test results of the copper-clad laminates prepared in the embodiments and comparative examples of the present invention.

[0161] Table 1

[0162]

[0163] As shown in Table 1, the phosphorus-amine curing agent synthesized according to the method of this invention has the same excellent flame retardancy as commercially available phosphorus-amine curing agents, and both can reach the UL-94V-0 level. Moreover, the phosphorus-amine phenolic curing agent containing a bismaleimide structure has a much higher Tg after curing than conventional high Tg products, which can greatly improve the heat resistance of copper-clad laminates.

[0164] Interlayer bonding strength was tested according to the IPC-TM-650-2.4.8C method.

[0165] Thermogravimetric analysis (Td5%): The TGA test was performed according to the TGA test method specified in IPC-TM-650 2.4.24.6.

[0166] Solder resistance at 288℃ (after 2 hours in a PCT pressure cooker)

[0167] The testing method involves immersing the pressure cooker-tested sample in a 288°C soldering furnace and recording the time required for the sample to blister and delaminate. The evaluation can be concluded when the substrate has been in the soldering furnace for more than 5 minutes without blistering or delamination.

[0168] Glass transition temperature test:

[0169] A differential scanning calorimeter (DSC) was used, with a heating rate of 20 °C / min.

[0170] Flame retardancy test:

[0171] The flame retardancy of the sample was tested according to the UL-94 standard method.

[0172] The present invention provides a novel phosphorus-amine-containing heat-resistant epoxy curing agent, its preparation method, and its applications. Specific examples have been used to illustrate the principles and implementation methods of the invention. These examples are merely illustrative to aid in understanding the method and core ideas of the invention, including the best mode, and to enable any person skilled in the art to practice the invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A phosphorus-containing amine curing agent characterized by comprising, The curing agent has a structure as shown in formula (I): （I）； Wherein, R is selected from , , , , or ; R1 is selected from , , , , or ; R2 is selected from , , , or .

2. A method for preparing the phosphorus-containing amine curing agent as described in claim 1, characterized in that, Includes the following steps: 1) After mixing DOPO organic solution, catalyst, isocyanate and organic solvent, the reaction is carried out to obtain intermediate solution; 2) The intermediate solution obtained in the above steps is reacted with diamine again to obtain the reaction solution; 3) After refluxing the reaction solution obtained in the above steps with the bismaleimide compound, a phosphorus-containing amine curing agent is obtained.

3. The preparation method according to claim 2, characterized in that, The solvent for the DOPO organic solution is one or more of toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, and cyclohexanone; The catalyst is one or more of imidazole compounds, quaternary ammonium salt compounds, and triphenylphosphine compounds.

4. The preparation method according to claim 2, characterized in that, The isocyanate is one or more selected from diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, phenyl diisocyanate, and isophorone diisocyanate; The organic solvent is one or more selected from toluene, methyl isobutyl ketone, xylene, propylene glycol methyl ether, diethylene glycol dimethyl ether, and cyclohexanone; The molar ratio of DOPO to isocyanate is (0.8~1.2):

1.

5. The preparation method according to claim 2, characterized in that, The catalyst accounts for 0.05 wt% to 0.2 wt% of the total mass of DOPO and isocyanate. The reaction temperature is 150~190℃; The reaction time is 2-3 hours.

6. The preparation method according to claim 2, characterized in that, The specific mixing method involves premixing the catalyst and isocyanate to obtain a solution, and then adding the DOPO organic solution dropwise into the solution for mixing. The dripping time is 1-3 hours; The temperature at which the drops are added is 150~190℃.

7. The preparation method according to claim 2, characterized in that, The catalyst is tetrabutylammonium bromide; The molar ratio of DOPO to diamine is (0.8~1.2):1; The diamine is one or more of phenylenediamine, 4,4'-diamino-3,3'-dimethylbiphenyl, diaminodiphenylmethane, diaminodiphenyl sulfone, bisphenol A type diether diamine, and 3,3'-dimethyl-5,5'-diethyl-4,4'-diaminodiphenylmethane.

8. The preparation method according to claim 2, characterized in that, The temperature for the second reaction is 110~130℃; The time for the second reaction is 4 to 6 hours.

9. The preparation method according to claim 2, characterized in that, The molar ratio of DOPO to bismaleimide compounds is (0.8~1.2):1; The reflux reaction temperature is 110~140℃; The reflux reaction time is 1-4 hours; The reflux reaction is followed by a process of heating to remove the solvent and / or dissolving the solvent.

10. The application of the phosphorus-amine curing agent according to claim 1 or the phosphorus-amine curing agent prepared by any one of claims 2 to 9 in the preparation of epoxy resin copper clad laminates.

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