A degradable bismaleimide thermosetting resin material and preparation method thereof

Abstract

The invention discloses a degradable bismaleimide thermosetting resin material and a preparation method thereof, and belongs to the technical field of thermosetting resin materials. The bismaleimide thermosetting resin of the present invention includes the following components: 1,3,5-tris (4-propionyl sulfide aniline) hexahydro-1,3,5-triazine, 2,2'-bis [4-(4-aminophenoxyphenyl)] propane, bismaleimide, and a bismaleimide thermosetting resin containing a hexahydrotriazine ring structure is prepared by solution polymerization and high-temperature curing. Acid-sensitive hexahydrotriazine ring structure is introduced into the bismaleimide structure to give it degradable performance. Compared with traditional thermosetting resins, the bismaleimide resin prepared by the present invention has degradability, can solve the environmental pollution problem caused by discarded thermosetting resins, and simultaneously achieves sustainable development. The thermosetting resin has great application prospects in aspects such as aviation materials and electronic devices.

Description

Technical Field

[0001] The present invention relates to the technical field of thermosetting resin materials, and in particular to a degradable bismaleimide thermosetting resin material containing a hexahydrotriazine ring structure and a preparation method thereof. Technical Background

[0002] Bismaleimide (BMI) is a bifunctional compound with maleimide as the terminal group in its molecular structure. It has excellent heat resistance, flame retardancy, and good dielectric properties and is widely used in advanced resin-based composites, high-temperature insulation materials, flame retardant materials, and high-temperature adhesives. However, due to its stable irreversible covalent cross-linked network, thermosetting BMI resins have good chemical and thermal stability. However, due to the difficulty of recycling, it can easily lead to waste of resources and even serious environmental pollution. To solve this problem, the introduction of a degradable hexahydrotriazine ring structure into its structure can make BMI resins degradable.

[0003] In recent years, bismaleimide (BMI) resins have been widely used in various fields such as aerospace, electronics, microelectronics, and defense due to their excellent heat resistance, moisture resistance, corrosion resistance, and good dielectric properties. However, due to the high curing temperature, high crosslink density, and strong molecular chain rigidity of bismaleimide (BMI), they cannot be melted or processed again, have poor toughness, and have low elongation at break. Therefore, toughening and modifying BMI resins while making them biodegradable is essential.

[0004] Therefore, to fundamentally address the difficulty of thermosetting resin degradation, researchers are exploring a more gentle chemical degradation approach, besides using harsh chemical conditions to break down the three-dimensional crosslinked network. This involves introducing reversible dynamic covalent bonds into the thermosetting resin structure. Dynamic covalent bonds include DA bonds, disulfide bonds, disulfide bonds, borate bonds, hexahydrotriazine bonds, imine bonds, and acetal bonds. These dynamic bonds render thermosetting resins biodegradable. Due to their highly crosslinked structure, thermosetting resins are difficult to decompose in nature, and discarded thermosetting resins can cause serious environmental pollution. Given these sustainability concerns, future thermosetting resins are expected to combine biodegradability with environmental friendliness. Therefore, the development of a biodegradable bismaleimide thermosetting resin is of great significance.

[0005] Because traditional bismaleimide thermosetting resins are infusible, their recycling is more difficult than that of linear polymer materials. To impart biodegradability and ecological sustainability to the material, the present invention modifies the bismaleimide resin with a triamine (PTHT) containing an acid-sensitive hexahydrotriazine ring structure. This unique structure allows for rapid decomposition under acidic conditions, thereby imparting biodegradability to the thermosetting bismaleimide resin. Summary of the Invention

[0006] The present invention aims to provide a degradable bismaleimide thermosetting resin material and a preparation method thereof. A method of introducing a reversible dynamic covalent bond hexahydrotriazine ring structure into the bismaleimide structure makes the prepared bismaleimide thermosetting resin material degradable, thereby solving the problems of harsh degradation conditions and difficult recycling of bismaleimide thermosetting resins. The material has a simple preparation method, good performance, and potential application value in fields such as electronic devices and the defense industry.

[0007] In order to achieve the technical objectives of the present invention, the specific technical solution is:

[0008] By synthesizing a triamine monomer and introducing a hexahydrotriazine ring structure, the polymer structure contains a reversible dynamic covalent bond; its heat resistance, degradability and mechanical properties are regulated by the group ratio of the three monomers. The synthetic reaction structure is as follows:

[0009]

[0010] The triamine monomer is a monomer containing an acid-sensitive hexahydrotriazine ring structure. The reaction structure diagram of its synthesis is as follows:

[0011]

[0012] The present invention also provides a method for preparing a degradable bismaleimide thermosetting resin material, comprising the following steps:

[0013] S1. Under a nitrogen atmosphere, a certain amount of bismaleimide was weighed, and then an aromatic diamine was dissolved in an organic solvent and added to the reaction system to carry out a Michael addition reaction. The mixture was polymerized at 130°C for 2 hours to obtain a synthesized linear oligomer.

[0014] S2. The linear oligomer of S1 is subjected to a bulk cross-linking reaction, a certain amount of triamine is weighed and dissolved in a solvent, and the mixture is added to the reaction system and the reaction is continued for 1 hour; after the reaction is completed, the reaction liquid is poured into a stainless steel spline mold coated with a release agent for leveling, and the mixture is placed in an oven for programmed temperature increase, and high-temperature curing is performed under a temperature increase program of 150°C / 2h+180°C / 2h+200°C / 2h+220°C / 2h+240°C / 4h to obtain a degradable bismaleimide thermosetting resin material.

[0015] Furthermore, the bismaleimide is N,N′-(4,4′-methylenediphenyl)bismaleimide.

[0016] Furthermore, the aromatic diamine includes one or more of 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl disulfide, 4,4'-diaminodiphenyl sulfide, and 4,4'-diaminodiphenylmethane.

[0017] Furthermore, the triamine includes a 1,3,5-tris(4-propionylthiophenylamino)hexahydro-1,3,5-triazine (PTHT) monomer, which contains an acid-sensitive hexahydrotriazine ring structure, and the NH2 in the structure undergoes a Michael addition reaction with the carbon-carbon double bond in bismaleimide.

[0018] Furthermore, the solvent includes one or more of NN-dimethylformamide, dimethylene sulfoxide, N-methylpyrrolidone, and NN-dimethylacetamide.

[0019] Furthermore, the degradable bismaleimide resin can be degraded in an acid-containing solution, and the acid substance includes one or more of nitric acid, sulfuric acid, hydrochloric acid, and phosphoric acid.

[0020] Furthermore, the high temperature curing procedure is 150°C / 2h+180°C / 2h+200°C / 2h+220°C / 2h+240°C / 4h.

[0021] Compared with the prior art, the present invention has the following technical advantages:

[0022] (1) The hexahydrotriazine ring structure is introduced into the bismaleimide structure of the present invention, which gives the thermosetting resin degradability and has very important reference significance for the construction of high-performance degradable thermosetting resin materials.

[0023] (2) The degradable thermosetting resin provided by the present invention has good thermal stability, and the initial thermal decomposition temperature is 357.7°C.

[0024] (3) The degradable bismaleimide thermosetting resin provided by the present invention has good mechanical properties and a tensile strength of 39.1-50.1 MPa.

[0025] (4) The resin material preparation method of the present invention is simple, efficient, and mild in conditions, and bismaleimide resin materials with different properties can be obtained by adjusting the ratio of monomers. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic structural diagram of the bismaleimide of the present invention.

[0027] Figure 2 It is the FTIR spectra of the raw material monomer of the present invention and bismaleimide with different monomer ratios.

[0028] Figure 3 It is the TGA curve of the bismaleimide prepared with different group ratios of the present invention.

[0029] Figure 4 It is the DSC curve diagram of the bismaleimide prepared with different group ratios of the present invention.

[0030] Figure 5 This is a digital diagram of the degradation of bismaleimide prepared with different group ratios in nitric acid solution. DETAILED DESCRIPTION

[0031] The present invention is further described in detail herein with reference to the following specific embodiments and accompanying drawings, and the present invention is not limited to the following implementation cases. Without departing from the idea and scope of the present invention, the advantages and all changes that can be thought of by relevant technicians in the field of polymer self-healing materials are included in the present invention, and the present invention covers all modifications, substitutions, equivalent methods and schemes within the idea and scope of the present invention as defined by the claims. The preparation process, reaction conditions, reagents, experimental methods, etc. for implementing the present invention, except for the contents specifically involved below, are all common knowledge and common sense in the field, and the present invention has no specific limiting content. In order to enable the public to better understand the present invention, some specific details are described in detail here. For those skilled in the art, the present invention can be fully understood without these details.

[0032] The reaction flow diagram of the degradable bismaleimide of the present invention is shown in the figure below:

[0033]

[0034] The following is further described through specific examples.

[0035] This study investigated the effects of adjusting the ratio of aromatic diamine to triamine by maintaining a fixed maleimide-to-amino ratio of 2:1 on the material's various properties. BMI-BAPP-PTHT-210 / 621 / 411 / 621 / 201 correspond to Examples 1, 2, 3, 4, and 5, respectively. See Table 1 for details.

[0036] Table 1 Design table of material dosage in different group ratios

[0037]

[0038] Example 1

[0039] A method for preparing a degradable bismaleimide thermosetting resin material comprises the following steps:

[0040] (1) N,N′-(4,4′-methylenediphenyl)bismaleimide (7.88 g, 22 mmol) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (4.51 g, 11 mmol) were placed in a three-necked flask with a mechanical stirrer. The mixture was heated to 130°C and stirred for 2 h. The viscosity of the system was adjusted with DMF.

[0041] (2) After the reaction is completed, the reaction solution is poured into a stainless steel sample mold coated with a release agent, and then placed in an oven for high-temperature curing at 150°C / 2h+180°C / 2h+200°C / 2h+220°C / 2h+240°C / 4h.

[0042] Example 2

[0043] A method for preparing a degradable bismaleimide thermosetting resin material comprises the following steps:

[0044] (1) Place N,N′-(4,4′-methylenediphenyl)bismaleimide (6.62 g, 18.5 mmol) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (2.53 g, 6.16 mmol) in a three-necked flask equipped with a mechanical stirrer. Heat to 130°C and stir for 2 h. Use DMF to adjust the viscosity of the system.

[0045] (2) 1,3,5-tris(4-propionylthiophenylamino)hexahydro-1,3,5-triazine (1.28 g, 2.05 mmol) was dissolved in DMF and added to (1) to continue the reaction. After the reaction was completed, the reaction solution was poured into a stainless steel sample mold coated with a release agent, and then placed in an oven for a procedure including 150℃ / 2h+180℃ / 2h+200℃ / 2h+220℃ / 2h+240℃ / 4h for high-temperature curing.

[0046] Example 3

[0047] A method for preparing a degradable bismaleimide thermosetting resin material comprises the following steps:

[0048] (1) Place N,N′-(4,4′-methylenediphenyl)bismaleimide (6.28 g, 17.5 mmol) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (1.80 g, 4.39 mmol) in a three-necked flask with a mechanical stirrer, heat to 130°C and stir for 2 h. Use DMF to adjust the viscosity of the system.

[0049] (2) 1,3,5-tris(4-propionylthiophenylamino)hexahydro-1,3,5-triazine (1.82 g, 2.91 mmol) was dissolved in DMF and added to (1) to continue the reaction. After the reaction was completed, the reaction solution was poured into a stainless steel sample mold coated with a release agent, and then placed in an oven for a procedure including 150℃ / 2h+180℃ / 2h+200℃ / 2h+220℃ / 2h+240℃ / 4h for high-temperature curing.

[0050] Example 4

[0051] A method for preparing a degradable bismaleimide thermosetting resin material comprises the following steps:

[0052] (1) Place N,N′-(4,4′-methylenediphenyl)bismaleimide (5.98 g, 16.7 mmol) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (1.14 g, 2.78 mmol) in a three-necked flask equipped with a mechanical stirrer. Heat to 130°C and stir for 2 h. Use DMF to adjust the viscosity of the system.

[0053] (2) 1,3,5-tris(4-propionylthiophenylamino)hexahydro-1,3,5-triazine (2.31 g, 3.70 mmol) was dissolved in DMF and added to (1) to continue the reaction. After the reaction was completed, the reaction solution was poured into a stainless steel sample mold coated with a release agent, and then placed in an oven for a procedure including 150℃ / 2h+180℃ / 2h+200℃ / 2h+220℃ / 2h+240℃ / 4h for high-temperature curing.

[0054] Example 5

[0055] A method for preparing a degradable bismaleimide thermosetting resin material comprises the following steps:

[0056] (1) Place N,N′-(4,4′-methylenediphenyl)bismaleimide (5.37 g, 15 mmol) and 1,3,5-tris(4-propionylthiophenylamino)hexahydro-1,3,5-triazine (3.12 g, 5 mmol) in a three-necked flask with a mechanical stirrer, heat to 130°C and stir for 2 h. Use DMF to adjust the viscosity of the system.

[0057] After the reaction is completed, the reaction liquid is poured into a stainless steel sample mold coated with a release agent, and then placed in an oven for high-temperature curing at 150°C / 2h+180°C / 2h+200°C / 2h+220°C / 2h+240°C / 4h.

[0058] Various performance tests were performed on Examples 1-5, and the results were as follows:

[0059] Table 2 shows the main performance indicators of Examples 1-5

[0060]

[0061] See Figure 1 The degradable bismaleimide resins prepared in Examples 1-5 contain a reversible, dynamically covalently bonded hexahydrotriazine ring within their structure. The acid sensitivity of the hexahydrotriazine ring enables the bismaleimide resins to degrade completely in acidic environments. The degradation performance, mechanical properties, and thermal stability of the bismaleimide resins can be adjusted by adjusting the ratio of maleimide groups to the amino groups in the aromatic diamine and triamine.

[0062] See Figure 2 The figure shows the three monomers BMI, BAPP, PTHT and bismaleimide resin cured products with different group ratios at 4000-600cm -1 FTIR spectrum in the range of BMI at 1142, 828 and 683 cm -1 The absorption bands of maleimide group are shown at 3411-3452 cm, which are attributed to maleimide CNC asymmetric stretching vibration, =CH out-of-plane bending and ring deformation. -1 、3337-3362cm -1 and 1597-1634cm -1 In the FTIR spectra of all cured products, the absorption bands characteristic of maleimide and primary amine are absent, and a very weak absorption band is caused by the relatively strong asymmetric stretching vibration (CNC) of succinimide, which is at 1167 cm -1These results indicate that the Michael addition of maleimide groups to primary amines proceeds almost completely at a 2:1 molar ratio of groups.

[0063] See Figure 3 As can be seen from the TGA curve, with the increase of PTHT content, the 5% thermal decomposition temperature and the maximum thermal decomposition temperature of BMI resin both decrease. The possible reasons include:

[0064] (1) After adding PTHT, the gel time of the reaction system becomes shorter, resulting in incomplete reaction between the groups. The residue content of the prepared BMI resin increases, affecting the thermal stability of the material.

[0065] (2) The PTHT structure contains unstable structures such as fatty chains. As the PTHT ratio increases, the content of thermally unstable groups in the polymer increases, resulting in a decrease in the thermal stability of the material.

[0066] See Figure 4 From the DSC curve, it can be seen that the glass transition temperature of BMI resin is g Between 197.8-221.6℃, when the PTHT content is 0, T g is 207.6℃. With the increase of PTHT content, T g The reason is that with the increase of PTHT content, the crosslinking density increases and the rigidity of the material becomes stronger. However, when the PTHT content accounts for 100% of -NH2 in the system, Tg decreases to 197.8℃. The reason is that PTHT is highly active. After adding more triamine, the gel time of the reaction system becomes shorter. There may be unreacted groups that make the reaction incomplete, which leads to a decrease in the rigidity of the material and Tg. g After the curing process, the BMI resins showed no obvious exothermic peaks, indicating that the resins were fully cured. BMI-BAPP-PTHT-201 exhibited an endothermic peak around 200°C, likely due to the endothermic transition of the bismaleimide resin from a glassy to rubbery state at this temperature.

[0067] See Figure 5 The degradation effect diagram of bismaleimide curing materials with different group ratios in nitric acid aqueous solution. The 210 curing product without PTHT is in the form of small fragments. After adding PTHT, the solid matter in the degradation product becomes less, and the degradation effect becomes more obvious with the increase of PTHT content. The reason is that PTHT contains acid-sensitive hexahydrotriazine ring structure. As its structure content increases, the degradation effect becomes more obvious.

[0068] The above is a further detailed description of the present invention in conjunction with specific / preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. Those skilled in the art of the art to which the present invention belongs may make several substitutions or modifications to the described embodiments without departing from the scope of the present invention, and such substitutions or modifications should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a degradable bismaleimide thermosetting resin material, characterized in that: The following steps are involved: (1) Under nitrogen atmosphere, a certain amount of bismaleimide is weighed, and then aromatic diamine is dissolved in an organic solvent and added to the reaction system to carry out Michael addition reaction; (2) Weigh a certain amount of triamine, dissolve it in a solvent, and add it to the reaction system to continue the reaction; the triamine is a monomer with a hexahydrotriazine ring structure, and the reaction structure diagram of its synthesis is as follows: After the reaction is completed, the reaction liquid is poured into a stainless steel sample mold coated with a release agent to be leveled, and then placed in an oven for programmed temperature rise and high-temperature curing to obtain a degradable bismaleimide thermosetting resin material; The bismaleimide described in step (1) is N,N′-(4,4′-methylenediphenyl)bismaleimide; The aromatic diamine described in step (1) is 2,2-bis[4-(4-aminophenoxy)phenyl]propane; The molar ratio of maleimide groups to amino groups in the monomer is 2:

1.

2. A method for preparing a degradable bismaleimide thermosetting resin material as claimed in claim 1, characterized in that: The reaction conditions described in step (1) are polymerization at 130°C for 2 h.

3. A method for preparing a degradable bismaleimide thermosetting resin material as claimed in claim 1, characterized in that: The solvent described in step (2) includes one or more of NN-dimethylformamide, dimethylene sulfoxide, N-methylpyrrolidone, and NN-dimethylacetamide.

4. A method for preparing a degradable bismaleimide thermosetting resin material as claimed in claim 1, characterized in that: In step (2), a certain amount of triamine was weighed and dissolved in a solvent, and then added to the reaction system and the reaction was continued for 1 hour.

5. The method for preparing a degradable bismaleimide thermosetting resin material according to claim 1, characterized in that: The high temperature curing procedure described in step (2) is 150°C / 2 h+180°C / 2 h+200°C / 2 h+220°C / 2 h+240°C / 4 h.

6. A degradable bismaleimide thermosetting resin material prepared by the method according to any one of claims 1 to 5.

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