Toughening agent containing norbornane structure and its application in preparation of modified bismaleimide resin

Abstract

The application discloses a toughening agent containing norbornane structure and application thereof in preparation of modified bismaleimide resin. The toughening agent containing norbornane structure is obtained by introducing multiple high-reactivity double bonds on the norbornane structure, and the introduction of the stereofatty cyclic structure with a large free volume reduces the dipole density per unit area in the resin system. Meanwhile, the terpolymerization among the bismaleimide monomer, the diallyl bisphenol A and the toughening agent containing norbornane structure changes the crosslinking mode of the original bismaleimide monomer / diallyl bisphenol A system, so that the toughened bismaleimide resin has good dielectric properties and excellent toughness and heat resistance, and has a good application prospect in the field of electronic packaging materials.

Description

Technical Field

[0001] This invention belongs to the technical field of toughening and low dielectric modification of bismaleimide resins, specifically relating to a toughening agent containing a norbornene structure and its application in the preparation of modified bismaleimide resins. Background Technology

[0002] Bismaleimide resins possess excellent corrosion resistance, heat resistance, low moisture absorption, and flame retardancy, and have been widely used in the field of electronic packaging materials. However, as a thermosetting resin, bismaleimide resins have a high crosslinking density and regular molecular structure, resulting in poor impact toughness and high brittleness, which greatly reduces their applicability in microelectronics processing. Currently, commercially available bismaleimide resins are modified from bismaleimide resins using 2,2'-diallylbisphenol A as a toughening agent. Although their brittleness and processability have been improved to some extent, the introduced toughening agent reduces the thermal stability of the bismaleimide resin, increasing the risk of warpage during reflow soldering. Moreover, the dielectric properties of this type of bismaleimide resin are not particularly excellent. Therefore, further improving the toughness, heat resistance, and dielectric properties of the bismaleimide monomer / diallylbisphenol A system is crucial to determining its applicability in the electronic packaging field.

[0003] CN115028780A reports that the three-dimensional ring-structured POSS can form a nano-interface region at the interface with the polymer resin matrix, thereby simultaneously reducing the dielectric constant and dielectric loss of the composite material. However, POSS is an inorganic material, and its compatibility with the polymer matrix is ​​a difficult problem to solve. Summary of the Invention

[0004] This invention addresses the problems existing in the prior art by providing a toughening agent containing a norcamphene structure and its application in the preparation of modified bismaleimide resins. This invention bonds a cyclic imide and a highly active terminal double bond structure to both sides of a norcamphene, efficiently introducing the toughening agent with an aliphatic stereocyclic structure into the bismaleimide resin through similar compatibility and interfacial reaction. Modified bismaleimide resins with excellent toughness, dielectric properties, and heat resistance are prepared via ternary copolymerization.

[0005] The toughening agent of the present invention, containing a norbornene structure, has the structure shown in Formula I:

[0006]

[0007] R is selected from one of the highly reactive terminal double bond structures shown in Formula II, Formula III, and Formula IV:

[0008]

[0009] In this context, * indicates a connection point.

[0010] The toughening agent containing a norbornene structure of the present invention is prepared by a method comprising the following steps:

[0011] Step 1: At -5 to 5°C, bis(aminomethyl)norbornene and anhydride containing terminal double bonds are slowly added dropwise to the protic acid at a molar ratio of 1:(2 to 3). Subsequently, the reaction system is reacted at 0 to 30°C for 2 to 4 hours.

[0012] Step 2: Transfer the reaction system from Step 1 to a heating device and continue heating the reaction at 60-120°C for 5-10 hours. After the reaction is complete, remove the protic acid to obtain the toughening agent product.

[0013] In step 1, the acid anhydride containing terminal double bonds is selected from one of the acid anhydride compounds of formulas V, VI, and VII:

[0014]

[0015] In step 1, the protic acid is selected from hydrochloric acid, formic acid, glacial acetic acid, or nitric acid; slow addition means controlling the addition time to within 30 to 60 minutes.

[0016] In step 2, when the acid anhydride compound shown in formula VI or formula VII is used as the raw material, the reaction is carried out at 60-120°C for 5-10 hours. After the reaction is completed, the toughening agent can be obtained. When the acid anhydride compound shown in formula V is used as the raw material, the reaction is carried out at 60-120°C for 5-10 hours. The product obtained needs to be reacted with methyl allyl alcohol at 50-120°C for another 10-15 hours to obtain the toughening agent.

[0017] The application of the toughening agent containing the norbornene structure in this invention involves using the toughening agent as a modifier to modify the original bismaleimide monomer / diallyl bisphenol A system to obtain a modified bismaleimide resin. The specific method is as follows:

[0018] A toughening agent containing a norbornene structure was blended with the original bismaleimide monomer / diallyl bisphenol A system and prepolymerized at high temperature to obtain a bismaleimide prepolymer. The modified prepolymer was then cast into a mold for molding, and finally demolded to obtain the modified bismaleimide resin.

[0019] The bismaleimide monomer contains two maleimide groups and includes at least the chemical structure shown in Formula VIII:

[0020]

[0021] In formula VIII, R1 is an organic group having 6 to 20 carbon atoms and containing an aromatic ring structure.

[0022] During the preparation process, bismaleimide monomer, diallyl bisphenol A and toughening agent are mixed in a ratio of maleimide group to allyl double bond of 1:(0.5-2).

[0023] Furthermore, the molar ratio of diallyl bisphenol A to toughening agent is 4:1 to 1:1, preferably 1:1.

[0024] The reaction temperature of the prepolymerization reaction is 130-150℃, and the reaction time is 1-2 hours.

[0025] During the casting and molding process, a gradient heating and curing method is adopted. The heating program is set as follows: constant temperature at 145-155℃ for 1.5-2.5h, constant temperature at 175-185℃ for 1.5-2.5h, constant temperature at 195-205℃ for 1.5-2.5h, constant temperature at 225-225℃ for 3.5-4.5h, and constant temperature at 235-245℃ for 3.5-4.5h.

[0026] This invention selects compounds with aliphatic stereocyclic structures, such as norbornene, norbornene, and cyclopentadiene. Because they are organic compounds, they not only improve the dielectric properties of polymer resins but also exhibit excellent compatibility with most matrix resins, making them preferred for modifying the dielectric properties of polymer resins. The toughening agent of this invention possesses a large free-volume stereoaliphatic stereocyclic structure, which effectively reduces the dipole density per unit area in the resin system. Furthermore, the highly reactive terminal double bonds at both ends of the molecule can participate in the copolymerization of the original bismaleimide monomer / diallylbisphenol A system, resulting in toughened bismaleimide resins with good dielectric properties and excellent heat resistance, showing broad application prospects in the field of electronic packaging materials.

[0027] Compared with the prior art, the present invention has the following significant advantages:

[0028] (1) The toughening agent of the present invention improves the compatibility between the toughening agent and the bismaleimide resin by introducing multiple highly reactive terminal double bonds on norbornene, while changing the crosslinking mode of the bismaleimide monomer / diallyl bisphenol A system, thereby achieving the purpose of ternary copolymerization modification.

[0029] (2) The toughening agent of the present invention introduces a norbornene structure with a large free volume, which greatly reduces the concentration of dipoles in the resin per unit volume, so that the prepared modified bismaleimide resin has outstanding dielectric properties.

[0030] (3) The toughening agent of the present invention has a stable imide ring and aliphatic stereocyclic structure, which can significantly improve the heat resistance of bismaleimide resin.

[0031] (4) The toughening agent of the present invention is simple to prepare and easy to be applied on a large scale in industrial applications. Attached Figure Description

[0032] Figure 1 This is the 1H NMR spectrum of toughening agent C prepared in Example 3 of the present invention.

[0033] Figure 2 This is the infrared spectrum of toughening agent C prepared in Example 3 of the present invention.

[0034] Figure 3 These are impact strength diagrams of unnotched cantilever beam impacts on experimental samples 3-9 and control sample 1 of this invention.

[0035] Figure 4 The graphs show the changes in dielectric constant and dielectric loss as a function of frequency for experimental samples 3-9 and control sample 1 of this invention.

[0036] Figure 5 The graphs show the changes in storage modulus and tanδ as a function of temperature for experimental samples 3-9 and control sample 1 of this invention.

[0037] Figure 6 These are glass transition temperature diagrams of experimental samples 3-9 and control sample 1 of this invention. Detailed Implementation

[0038] The present invention will be further described below through preferred embodiments. The embodiments of the present invention are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0039] Example 1:

[0040] 1. Preparation of toughening agent A: 500 mL of glacial acetic acid was added to a three-necked flask and placed in an ice-water bath for 30 min; then 36.4 g of 4-chlorophthalic anhydride and 15.4 g of bis(aminomethyl)norbornene were slowly added to the above glacial acetic acid solution, stirred evenly, and reacted at room temperature for 4 h; then the above reaction system was transferred to an oil bath and refluxed at 120 °C for 6 h; after the reaction was completed, the glacial acetic acid was removed by rotary evaporation to obtain intermediate A1.

[0041] The above-mentioned 48.3g of intermediate A1 was dissolved in 500ml of tetrahydrofuran to form a homogeneous solution; 14.4g of methanallyl alcohol and 20.1g of triethylamine were mixed evenly and slowly added dropwise to the above solution; the reaction system was reacted at 70℃ for 12h, and after the reaction was completed, toughening agent A was obtained by rotary evaporation, extraction and drying, with the structure shown in formula IX below.

[0042]

[0043] 2. Preparation of modified bismaleimide resin: 21g of 2,2'-diallylbisphenol A and 37.9g ​​of toughening agent A were thoroughly mixed at 110℃, followed by the addition of 58g of 4,4'-bismaleimide diphenylmethane. The reaction system was prepolymerized at 130–150℃. When the viscosity of the system decreased and it turned a uniform reddish-brown color, the system was degassed using a vacuum pump until no bubbles were generated. The mixture was then transferred to a preheated mold. Curing was performed using the following temperature program: 145–155℃ for 1.5–2.5h, 175–185℃ for 1.5–2.5h, 195–205℃ for 1.5–2.5h, 225–225℃ for 3.5–4.5h, and 235–245℃ for 3.5–4.5h. The final cured product was defined as experimental sample 1.

[0044] Example 2:

[0045] 1. Preparation of toughening agent B: 500 ml of glacial acetic acid was added to a three-necked flask and placed in an ice-water bath for 30 min; then 28.0 g of allyl succinic anhydride and 15.4 g of bis(aminomethyl)norbornene were slowly added to the above glacial acetic acid solution, stirred evenly, and reacted at room temperature for 4 h; then the above reaction system was transferred to an oil bath and refluxed at 120 °C for 6 h; after the reaction was completed, the glacial acetic acid was removed by rotary evaporation to obtain toughening agent B, with the structure shown in Formula X below.

[0046]

[0047] 2. Preparation of modified bismaleimide resin: 21g of 2,2'-diallylbisphenol A and 27.1g of toughening agent B were thoroughly mixed at 110℃, followed by the addition of 58g of 4,4'-bismaleimide diphenylmethane. The reaction system was prepolymerized at 130–150℃. When the viscosity of the system decreased and it turned a uniform reddish-brown color, the system was degassed using a vacuum pump until no bubbles were generated. The mixture was then transferred to a preheated mold. Curing was performed using the following temperature program: 145–155℃ for 1.5–2.5h, 175–185℃ for 1.5–2.5h, 195–205℃ for 1.5–2.5h, 225–225℃ for 3.5–4.5h, and 235–245℃ for 3.5–4.5h. The final cured product was defined as experimental sample 2.

[0048] Example 3:

[0049] Preparation of toughening agent C: 500 ml of glacial acetic acid was added to a three-necked flask and placed in an ice-water bath for 30 min. Then, 32.8 g of norbornene and 15.4 g of bis(aminomethyl)norbornene were slowly added to the glacial acetic acid solution, stirred thoroughly, and reacted at room temperature for 4 h. The reaction system was then transferred to an oil bath and refluxed at 120 °C for 6 h. After the reaction was complete, the glacial acetic acid was removed by rotary evaporation to obtain toughening agent C, with the structure shown in formula XI below. 1 The H NMR and infrared spectra are as follows: Figure 1 and 2 As shown.

[0050]

[0051] Example 4:

[0052] 29.4 g of 2,2'-diallylbisphenol A and 17.9 g of toughening agent C were thoroughly mixed at 110 °C, followed by the addition of 58 g of 4,4'-bismaleimide diphenylmethane. The reaction system was prepolymerized at 130–150 °C. When the viscosity of the system decreased and it turned a uniform reddish-brown color, the system was degassed using a vacuum pump until no more bubbles were generated. The mixture was then transferred to a preheated mold. Curing was performed using the following temperature program: 145–155 °C for 1.5–2.5 h, 175–185 °C for 1.5–2.5 h, 195–205 °C for 1.5–2.5 h, 225–225 °C for 3.5–4.5 h, and 235–245 °C for 3.5–4.5 h. The final cured product was defined as Experimental Sample 3.

[0053] Example 5:

[0054] 25.2 g of 2,2'-diallylbisphenol A and 23.8 g of toughening agent C were thoroughly mixed at 110 °C, followed by the addition of 58 g of 4,4'-bismaleimide diphenylmethane. The reaction system was prepolymerized at 130–150 °C. When the viscosity of the system decreased and it turned a uniform reddish-brown color, the system was degassed using a vacuum pump until no more bubbles were generated. The mixture was then transferred to a preheated mold. Curing was performed using the following temperature program: 145–155 °C for 1.5–2.5 h, 175–185 °C for 1.5–2.5 h, 195–205 °C for 1.5–2.5 h, 225–225 °C for 3.5–4.5 h, and 235–245 °C for 3.5–4.5 h. The final cured product was defined as experimental sample 4.

[0055] Example 6:

[0056] 21.0 g of 2,2'-diallylbisphenol A and 29.8 g of toughening agent C were thoroughly mixed at 110 °C, followed by the addition of 58 g of 4,4'-bismaleimide diphenylmethane. The reaction system was prepolymerized at 130–150 °C. When the viscosity of the system decreased and it turned a uniform reddish-brown color, the system was degassed using a vacuum pump until no more bubbles were generated. The mixture was then transferred to a preheated mold. Curing was performed using the following temperature program: 145–155 °C for 1.5–2.5 h, 175–185 °C for 1.5–2.5 h, 195–205 °C for 1.5–2.5 h, 225–225 °C for 3.5–4.5 h, and 235–245 °C for 3.5–4.5 h. The final cured product was defined as Experimental Sample 5.

[0057] Example 7:

[0058] 16.8 g of 2,2'-diallylbisphenol A and 35.7 g of toughening agent C were thoroughly mixed at 110 °C, followed by the addition of 58 g of 4,4'-bismaleimide diphenylmethane. The reaction system was prepolymerized at 130–150 °C. When the viscosity of the system decreased and it turned a uniform reddish-brown color, the system was degassed using a vacuum pump until no more bubbles were generated. The mixture was then transferred to a preheated mold. Curing was performed using the following temperature program: 145–155 °C for 1.5–2.5 h, 175–185 °C for 1.5–2.5 h, 195–205 °C for 1.5–2.5 h, 225–225 °C for 3.5–4.5 h, and 235–245 °C for 3.5–4.5 h. The final cured product was defined as Experimental Sample 6.

[0059] Example 8:

[0060] 12.6 g of 2,2'-diallylbisphenol A and 41.7 g of toughening agent C were thoroughly mixed at 110 °C, followed by the addition of 58 g of 4,4'-bismaleimide diphenylmethane. The reaction system was prepolymerized at 130–150 °C. When the viscosity of the system decreased and it turned a uniform reddish-brown color, the system was degassed using a vacuum pump until no more bubbles were generated. The mixture was then transferred to a preheated mold. Curing was performed using the following temperature program: 145–155 °C for 1.5–2.5 h, 175–185 °C for 1.5–2.5 h, 195–205 °C for 1.5–2.5 h, 225–225 °C for 3.5–4.5 h, and 235–245 °C for 3.5–4.5 h. The final cured product was defined as experimental sample 7.

[0061] Example 9:

[0062] 8.4 g of 2,2'-diallylbisphenol A and 47.6 g of toughening agent C were thoroughly mixed at 110 °C, followed by the addition of 58 g of 4,4'-bismaleimide diphenylmethane. The reaction system was prepolymerized at 130–150 °C. When the viscosity of the system decreased and it turned a uniform reddish-brown color, the system was degassed using a vacuum pump until no more bubbles were generated. The mixture was then transferred to a preheated mold. Curing was performed using the following temperature program: 145–155 °C for 1.5–2.5 h, 175–185 °C for 1.5–2.5 h, 195–205 °C for 1.5–2.5 h, 225–225 °C for 3.5–4.5 h, and 235–245 °C for 3.5–4.5 h. The final cured product was defined as experimental sample 8.

[0063] Example 10:

[0064] 59.5 g of toughening agent C was thoroughly stirred at 110 °C, followed by the addition of 58 g of 4,4'-bismaleimide diphenylmethane. The reaction system was prepolymerized at 130–150 °C. When the viscosity of the system decreased and it turned a uniform reddish-brown color, the system was degassed using a vacuum pump until no more bubbles were generated. The mixture was then transferred to a preheated mold. Curing was performed using the following temperature program: 145–155 °C for 1.5–2.5 h, 175–185 °C for 1.5–2.5 h, 195–205 °C for 1.5–2.5 h, 225–225 °C for 3.5–4.5 h, and 235–245 °C for 3.5–4.5 h. The final cured product was defined as experimental sample 9. Comparative Example 1:

[0065] 42 g of 2,2'-diallylbisphenol A was thoroughly stirred at 110 °C, followed by the addition of 58 g of 4,4'-bismaleimide diphenylmethane. The reaction system was prepolymerized at 130–150 °C. When the viscosity of the system decreased and it turned a uniform reddish-brown color, the system was degassed using a vacuum pump until no more bubbles were generated. The mixture was then transferred to a preheated mold. Curing was performed using the following temperature program: 145–155 °C for 1.5–2.5 h, 175–185 °C for 1.5–2.5 h, 195–205 °C for 1.5–2.5 h, 225–225 °C for 3.5–4.5 h, and 235–245 °C for 3.5–4.5 h. The final cured product was defined as Comparative Sample 1.

[0066] The dielectric properties, impact strength, and glass transition temperature of the bismaleimide resins obtained in Examples 1-9 and Comparative Example 1 are shown in Table 1.

[0067] Table 1

[0068]

[0069] Although the molar ratio of diallyl bisphenol A to toughening agent in experimental samples 1, 2, and 5 was 1:1, the performance of these three samples varied significantly. Compared to control sample 1, the dielectric properties of all three samples were improved due to the introduction of the norbornene structure. The control sample, being unmodified, had a dielectric constant and dielectric loss as high as 3.16 and 0.01876, respectively, which does not meet the requirements for 5G communication. The dielectric constant and dielectric loss of experimental samples 1, 2, and 5 decreased sequentially, with experimental sample 5 reaching the lowest values ​​of 2.6 and 0.00926. Experimental sample 5 used toughening agent C containing three norbornene structures per molecule, so its overall improvement in dielectric properties was superior to that of toughening agents A and B derived from a single norbornene. Experimental samples 3–8 were all obtained by modifying toughening agent C, with molar ratios of diallyl bisphenol A to toughening agent of 7:3, 6:4, 5:5, 6:4, 7:3, and 8:2, respectively. Studies have found that as the content of toughening agent C increases, the dielectric properties and impact strength of the obtained bismaleimide resins show a trend of first increasing and then decreasing, with experimental sample 5 exhibiting the best performance. This phenomenon may be because diallyl bisphenol A also has the ability to improve toughness and dielectric properties. When the content of toughening agent C in the ternary system increases, the content of diallyl bisphenol A decreases. When the molar ratio of diallyl bisphenol A to toughening agent C increases to 1:1, the modified resin achieves optimal dielectric and toughness. However, when the content of toughening agent C continues to increase, the modified resin undergoes a change in crosslinking mode due to the decrease in diallyl bisphenol A content, leading to a gradual decrease in dielectric and toughness. Although experimental sample 9 exhibits excellent dielectric properties and toughness, the absence of diallyl bisphenol A leads to self-polymerization of toughening agent C. This results in glass transition temperatures of 181°C and 328°C for the toughening agent C / C and toughening agent C / bismaleimide monomer copolymer segments, respectively, in the modified bismaleimide resin. Therefore, in summary, the modified bismaleimide resin with the best dielectric properties, heat resistance, and toughness is obtained when the molar ratio of diallyl bisphenol A to toughening agent C is 1:1.

[0070] Table 2 provides the UL94 rating and Limiting Oxygen Index (LOI) of experimental samples 1–9 and control sample 1. Compared to control sample 1, experimental sample 1, due to the use of toughening agent A with a larger molecular weight, has a lower crosslinking density in the modified bismaleimide, resulting in lower flame retardancy and exhibiting a lower UL94 rating and LOI. Experimental sample 2, due to the use of toughening agent B with a smaller molecular weight, has a higher crosslinking density in the modified bismaleimide, resulting in higher flame retardancy and exhibiting a higher UL94 rating and LOI. Analysis of experimental samples 3–9 shows that, due to the special ternary copolymerization method, the LOI values ​​of experimental samples 3–5 exceed those of control sample 1. As the content of toughening agent C increases, the flame retardant performance of the material gradually decreases. This is likely due to the mismatch in the content of each component in the ternary system, leading to poor heat resistance of the crosslinked network.

[0071] Based on the results in Tables 1 and 2, it can be found that when the molar ratio of diallyl bisphenol A and toughening agent C is 1:1, the experimental sample 5 has the best dielectric properties, heat resistance and toughness, and its flame retardant properties are better than those of the unmodified control sample 1.

[0072] Table 2

[0073]

[0074] The above description is merely an embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be within the scope of protection of the present invention.

Claims

1. The application of a toughening agent containing a norbornene structure, characterized in that: The toughening agent containing the norbornene structure was used as a modifier to modify the bismaleimide monomer and diallyl bisphenol A system to obtain a modified bismaleimide resin. The toughening agent containing the norbornene structure is selected from compounds with the following structures: 、 ； The bismaleimide monomer contains two maleimide groups, selected from the chemical structure shown in Formula VIII: ； In formula VIII, R1 is an organic group having 6 to 20 carbon atoms and containing an aromatic ring structure; During the preparation process, the bismaleimide monomer, diallyl bisphenol A and toughening agent are mixed in a molar ratio of maleimide group to allyl double bond of 1:(0.5~2); the molar ratio of diallyl bisphenol A and toughening agent is 4:1 to 1:

1.

2. The application according to claim 1, characterized in that: A toughening agent containing a norbornene structure was blended with a bismaleimide monomer and a diallyl bisphenol A system and prepolymerized at high temperature to obtain a bismaleimide prepolymer. The modified prepolymer was then cast into a mold for molding and finally demolded to obtain a modified bismaleimide resin.

3. The application according to claim 1, characterized in that: The molar ratio of diallyl bisphenol A to toughening agent is 1:

1.

4. The application according to claim 2, characterized in that: The reaction temperature of the prepolymerization reaction is 130~150℃, and the reaction time is 1~2h.

5. The application according to claim 2, characterized in that: During the casting and molding process, a gradient heating and curing method is adopted. The heating program is set as follows: constant temperature at 145~155℃ for 1.5~2.5h, constant temperature at 175~185℃ for 1.5~2.5h, constant temperature at 195~205℃ for 1.5~2.5h, constant temperature at 225~225℃ for 3.5~4.5h, and constant temperature at 235~245℃ for 3.5~4.5h.

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