A Remoldable and Degradable Bismaleimide Resin and Its Preparation Method

Abstract

The invention discloses a remodelable and degradable bismaleimide resin and a preparation method thereof, which is prepared by 4,4'-dithiodiphenylamine bismaleimide (AM), 4,4'-diallyloxydiphenyl disulfide (DS) and phenolphthalein polyaryletherketone. The bismaleimide resin prepared by the invention not only has excellent heat resistance, but also can be remodeled under hot pressing conditions; it can achieve faster degradation in conventional solvents, and the degradation solution can be evaporated of the solvent, heated and pressurized to achieve closed-loop recovery, which overcomes the shortcomings of bismaleimide resins containing reversible covalent bonds that are difficult to have high heat resistance, remodelability and degradability, and provides new resins and preparation strategies for achieving sustainable development of heat-resistant thermosetting resins.

Description

Technical Field

[0001] The present invention relates to a thermosetting resin and a preparation method thereof, and particularly to a remoldable and degradable bismaleimide resin and its preparation, remolding and degradation recycling methods, belonging to the field of functional polymer materials. Background Art

[0002] Bismaleimide (BMI) resin is a typical heat-resistant thermosetting resin and has been widely used in aerospace, transportation, information and other high-tech fields. As a thermosetting resin, it is difficult to repair and recycle due to the "insoluble and infusible" characteristics after curing. Therefore, in recent years, the research and development of remoldable and degradable thermosetting resins have attracted extensive attention. Through reversible covalent bond technology, the remolding and degradation of various thermosetting resins have been realized, but the related research on BMI resin is still in its infancy.

[0003] There are almost no reports on the simultaneous realization of degradation for the existing remoldable bismaleimide resins. The prior art discloses that a BMI resin prepared by copolymerizing an aryl allyl ether compound containing a disulfide bond with 4,4'-maleimidodiphenylmethane (BDM) cannot achieve degradation due to its high crosslinking density although it has reversible dynamic covalent bonds (see the literature: Study on High-Performance Intrinsic Flame-Retardant Bismaleimide Resin Containing Disulfide Bonds and Its Remolding Performance). The prior art uses BDM, 4-aminophenyl sulfide and aliphatic polyether diamine to copolymerize to obtain a remoldable BMI resin, and its remolding efficiency is only 8%, and there is no degradation report (see the literature: Reprocessable bismaleimide-diamine thermosets based on disulfide bonds).

[0004] The prior art CN118930851A prepared a BMI resin that can be degraded in an aqueous nitric acid solution by copolymerizing a triamine containing an acid-sensitive hexahydrotriazine ring structure, 2,2-bis[4-(4-aminophenoxy)phenyl]propane with BDM, but there is no remolding, and the resin preparation requires the use of solvents such as DMF. The prior art discloses the degradation of a BMI resin, which can only be completely degraded in a toluene solution containing an excessive amount of mercapto(dimethoxy)methylsilane (DP970) for 12 h (see the literature: Aging-Resistant, High-Strength, Reprocessable, and Recyclable Silicones through Dynamic Thiol-Maleimide Chemistry).

[0005] In summary, there are very few reports on remodelable and degradable bismaleimide resins in the prior art, and the BMI resins reported in the prior art are difficult to have high heat resistance, remodelability, and degradability. Therefore, the development of a new remodelable / degradable BMI resin with high heat resistance has great application value. Summary of the invention

[0006] In view of the deficiencies of the prior art, the present invention provides a remodelable and degradable bismaleimide resin with high heat resistance and a preparation method thereof.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows.

[0008] A remodelable and degradable bismaleimide resin is disclosed. The raw materials for preparing the remodelable and degradable bismaleimide resin include 4,4'-diallyloxydiphenyl disulfide, phenolphthalein polyaryletherketone and 4,4'-dithiodiphenylamine bismaleimide.

[0009] Preferably, the raw materials for preparing the remodelable and degradable bismaleimide resin of the present invention are 4,4'-diallyloxydiphenyl disulfide, phenolphthalein polyaryletherketone and 4,4'-dithiodiphenylamine bismaleimide.

[0010] In the present invention, the mass ratio of the monomer to the phenolphthalein polyaryletherketone is 1: (0.05-0.2); the monomer is 4,4'-diallyloxydiphenyl disulfide and 4,4'-dithiodiphenylamine bismaleimide, and the molar ratio of 4,4'-diallyloxydiphenyl disulfide to 4,4'-dithiodiphenylamine bismaleimide is (0.5-1):1.

[0011] Preferably, the molar ratio of 4,4'-diallyloxydiphenyl disulfide to 4,4'-dithiodiphenylamine bismaleimide is (0.6-0.9):1.

[0012] More preferably, the molar ratio of 4,4'-diallyloxydiphenyl disulfide to 4,4'-dithiodiphenylamine bismaleimide is (0.7-0.9):1; as an example, the molar ratio of 4,4'-diallyloxydiphenyl disulfide to 4,4'-dithiodiphenylamine bismaleimide is 0.8:1, 0.85:1, 0.86:1, 0.9:1, or any ratio within the range.

[0013] The invention discloses a method for preparing the above-mentioned remodelable and degradable bismaleimide resin, comprising the following steps: mixing the raw materials for preparing the remodelable and degradable bismaleimide resin, and then curing to obtain the remodelable and degradable bismaleimide resin.

[0014] In the present invention, phenolphthalein polyaryletherketone and 4,4'-diallyloxy diphenyl disulfide are mixed at 100 - 180 °C, then 4,4'-dithiobis (phenylamine) bismaleimide is added and mixed at 100 - 150 °C, and then cured to obtain a remoldable and degradable bismaleimide resin.

[0015] Preferably, phenolphthalein polyaryletherketone and 4,4'-diallyloxy diphenyl disulfide are mixed and stirred at 120 - 170 °C for 5 - 60 minutes, then 4,4'-dithiobis (phenylamine) bismaleimide is added and mixed and stirred at 110 - 140 °C for 5 - 45 minutes, and then cured to obtain a remoldable and degradable bismaleimide resin.

[0016] In the present invention, the curing temperature is 150 - 240 °C and the time is 8 - 15 hours, and the curing is carried out by stepwise heating. Preferably, when stepwise heating, the temperature difference between adjacent steps is 20 - 30 °C and the time is 1 - 3 hours.

[0017] The present invention discloses a preparation method of a remoldable and degradable bismaleimide resin prepolymer, which includes the following steps: mixing the raw materials for preparing the remoldable and degradable bismaleimide resin to obtain a remoldable and degradable bismaleimide resin prepolymer; the raw materials for preparing the remoldable and degradable bismaleimide resin include 4,4'-diallyloxy diphenyl disulfide, phenolphthalein polyaryletherketone, and 4,4'-dithiobis (phenylamine) bismaleimide. Preferably, the raw materials for preparing the remoldable and degradable bismaleimide resin are 4,4'-diallyloxy diphenyl disulfide, phenolphthalein polyaryletherketone, and 4,4'-dithiobis (phenylamine) bismaleimide.

[0018] The present invention discloses the application of the above-mentioned remoldable and degradable bismaleimide resin in the preparation or as a bismaleimide resin material. The bismaleimide resin material can be a bismaleimide resin material added with inorganic fillers, a bismaleimide resin material compounded with reinforcing materials, a bismaleimide resin material compounded with other resins, etc. The reinforcing materials include fiber materials, such as fibers or fiber fabrics (fiber cloth), etc.

[0019] The present invention discloses a remolding method of the above-mentioned remoldable and degradable bismaleimide resin, which includes the following steps: hot pressing the crushed remoldable and degradable bismaleimide resin to realize the remolding of the remoldable and degradable bismaleimide resin.

[0020] The present invention discloses a degradation method of the above-mentioned remoldable and degradable bismaleimide resin, which includes the following steps: placing the remoldable and degradable bismaleimide resin in a solvent to realize the degradation of the remoldable and degradable bismaleimide resin.

[0021] The invention discloses a method for recovering the remodelable and degradable bismaleimide resin, comprising the following steps: degrading the remodelable and degradable bismaleimide resin in a solvent, and then removing the solvent to achieve recovery of the remodelable and degradable bismaleimide resin.

[0022] Furthermore, the recovered resin can be used to prepare bismaleimide resin material through hot pressing.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention uses 4,4'-dithiodiphenylamine bismaleimide (AM), 4,4'-diallyloxydiphenyl disulfide (DS) and phenolphthalein polyaryletherketone as raw materials to prepare a BMI resin that is remodelable, degradable and highly heat-resistant (Tg is not less than 220°C).

[0025] 2. The bismaleimide resin prepared by the present invention has a large dynamic bond content, which helps the resin to be reshaped at a lower temperature, giving the BMI resin a reshapeable property and reducing resource waste.

[0026] 3. The BMI resin prepared by the present invention has strong segment mobility, is degradable and has improved degradation efficiency.

[0027] 4. The remodelable and degradable bismaleimide resin prepared by the present invention has high mechanical properties, which is manifested in high bending strength. This is not only due to the high mechanical properties of the BMI resin, but also because the presence of phenolphthalein polyaryletherketone makes the resin have both high rigidity and good toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the synthesis reaction formula and chemical structural formula of 4,4'-dithiodiphenylamine bismaleimide and 4,4'-diallyloxydiphenyl disulfide of the present invention.

[0029] Figure 2 The nuclear magnetic resonance hydrogen spectrum of 4,4'-dithiodiphenylamine bismaleimide of the present invention is ( 1 H NMR), carbon nuclear magnetic resonance spectroscopy ( 13 C NMR).

[0030] Figure 3 It is the mass spectrum of 4,4'-dithiodiphenylamine bismaleimide of the present invention.

[0031] Figure 4 The nuclear magnetic resonance hydrogen spectrum of 4,4'-diallyloxydiphenyl disulfide of the present invention is ( 1 H NMR), carbon nuclear magnetic resonance spectroscopy ( 13 C NMR).

[0032] Figure 5 It is the mass spectrum of 4,4'-diallyloxydiphenyl disulfide of the present invention.

[0033] Figure 6 This is the loss tangent (Tanδ)-temperature curve of the remodelable and degradable bismaleimide resin prepared in Examples 1-4 of the present invention, with a heating rate of 3°C / min and a frequency of 1 Hz.

[0034] Figure 7 This is the thermogravimetric (TGA) curve of the remodelable and degradable bismaleimide resin prepared in Example 1-4 of the present invention, with a heating rate of 10°C / min and nitrogen.

[0035] Figure 8 It is a bar graph of the bending strength of the remodelable and degradable bismaleimide resin prepared in Examples 1-4 of the present invention and Comparative Example 1.

[0036] Figure 9 1 is the stress relaxation curve of the remodelable and degradable bismaleimide resin prepared in Examples 1-4 of the present invention and Comparative Example 1.

[0037] Figure 10 This is a digital photo of the remodeling process of the remodelable and degradable bismaleimide resin prepared in Example 1 of the present invention.

[0038] Figure 11 It is a bar graph of the bending strength of the remodelable and degradable bismaleimide resin after remodeling prepared in Examples 1-4 of the present invention.

[0039] Figure 12 This is the thermal gravimetric loss (TGA) curve of the remodelable and degradable bismaleimide resin prepared in Example 1-4 of the present invention after remodeling, with a heating rate of 10°C / min and nitrogen.

[0040] Figure 13 These are digital photos of the remodelable and degradable bismaleimide resins prepared in Examples 1-4 of the present invention and Comparative Examples 1 and 2 before and after degradation.

[0041] Figure 14 FTIR spectra of the degradation residues of the bismaleimide resin prepared in Examples 1-4 of the present invention and phenolphthalein polyaryletherketone.

[0042] Figure 15 FTIR spectra of the bismaleimide resin and its degradation product (deBMI) prepared in Example 1 of the present invention.

[0043] Figure 16 This is a digital photo of the degradation and recovery of the bismaleimide resin prepared in Example 1 of the present invention.

[0044] Figure 17This is the loss tangent (Tanδ)-temperature curve of the bismaleimide resin degradation recovery resin (R-deBMI) prepared in Example 1 of the present invention, with a heating rate of 3°C / min and a frequency of 1 Hz. DETAILED DESCRIPTION

[0045] The present invention discloses a method for preparing the above-mentioned remodelable and degradable bismaleimide resin, comprising the following steps:

[0046] Using maleic anhydride and 4,4'-diaminodiphenyl disulfide as raw materials, 4,4'-dithiodiphenylamine bismaleimide (AM) was obtained through acylation reaction;

[0047] Using 3-bromopropylene and 4,4'-dihydroxydiphenyl disulfide as raw materials, 4,4'-diallyloxydiphenyl disulfide (DS) was obtained through substitution reaction;

[0048] 4,4'-diallyloxydiphenyl disulfide is mixed with phenolphthalein polyaryletherketone, and then 4,4'-dithiodiphenylamine bismaleimide is added and mixed, and then cured to obtain a remodelable and degradable bismaleimide resin.

[0049] In the above technical scheme, phenolphthalein polyaryletherketone and 4,4'-diallyloxydiphenyl disulfide are mixed and stirred at 140-150°C for 10-20 minutes, and then 4,4'-dithiodiphenylamine bismaleimide is added, mixed and stirred at 120-130°C for 10-25 minutes, and then cured to obtain a reshapeable and degradable bismaleimide resin.

[0050] In the above technical scheme, the mass ratio of the two monomers (4,4'-diallyloxydiphenyl disulfide and 4,4'-dithiodiphenylamine bismaleimide) to phenolphthalein polyaryletherketone is 1: (0.05-0.2); the temperature of the curing reaction is 150-240°C, the time is 10-12 hours, and the curing reaction adopts a step-by-step temperature increase.

[0051] The remodeling method of the remodelable and degradable bismaleimide resin of the present invention comprises the following steps: pressurizing and heating the crushed remodelable and degradable bismaleimide resin to complete the remodeling of the remodelable and degradable bismaleimide resin. Crushing is a conventional method, which can be mechanically crushed. For the present invention, the degraded resin can also be used, which is a technical effect that cannot be expected in the prior art.

[0052] The degradation method of the remodelable and degradable bismaleimide resin of the present invention comprises the following steps: placing the remodelable and degradable bismaleimide resin in a mixed solution of N,N-dimethylformamide (DMF) and β-mercaptoethanol to achieve its degradation.

[0053] The recycling method of the above-mentioned reshaping and degradable bismaleimide resin of the present invention includes the following steps: placing the reshaping and degradable bismaleimide resin in a mixed solution of N,N-dimethylformamide (DMF) and β-mercaptoethanol for degradation, removing the solvent from the obtained solution to obtain resin powder, and realizing the recycling of the reshaping and degradable bismaleimide resin.

[0054] Furthermore, heating and pressurizing the above-mentioned powder realizes the reshaping after the recycling of the reshaping and degradable bismaleimide resin.

[0055] Next, in combination with the drawings and embodiments, the technical solution of the present invention will be further described. The raw materials used in the present invention are existing products, and the specific preparation operations and performance tests are all conventional technologies.

[0056] Phenolphthalein polyaryletherketone (cPEK, number average molecular weight is 40,000), Xuzhou Aeronautical Materials Engineering Plastics Factory, and its chemical structural formula is as follows:

[0057] 。

[0058] Synthesis Example

[0059] Figure 1 is the synthesis reaction formula and chemical structural formula of 4,4'-dithiobis(phenylmaleimide) and 4,4'-diallyloxydiphenyl disulfide.

[0060] (1) Synthesis of 4,4'-dithiobis(phenylmaleimide)

[0061] At room temperature, maleic anhydride (6.33 g, 64.6 mmol) was dissolved in an acetone (80 mL) solution, stirred at room temperature under a nitrogen atmosphere, and a mixed solution of 4,4'-dithiobis(aniline) (8.01 g, 32.3 mmol) and acetone (120 mL) was added dropwise through a constant pressure funnel. After the addition was completed, it was stirred at room temperature for 4 h, then sodium acetate (2.525 g, 30.75 mmol) and acetic anhydride (25 mL) were added, and it was stirred in a nitrogen atmosphere at 85 °C for 4 h, then naturally cooled to room temperature, precipitated in cold water, filtered by suction, washed with 5% NaHCO3 solution, the solid obtained by suction filtration was dissolved in dichloromethane (DCM), washed with water 3 times, dried with anhydrous MgSO4, and the obtained brown product was concentrated by rotary evaporation to remove the solvent and dried conventionally to obtain a yellow powder, which is 4,4'-dithiobis(phenylmaleimide) (AM), Figure 2 is its nuclear magnetic resonance hydrogen spectrum ( 1 1H NMR) and nuclear magnetic resonance carbon spectrum ( 13 13C NMR), Figure 3 is its high-resolution mass spectrum.

[0062] In the 1The characteristic peaks of each H can be found in 1H NMR (CDCl3). Specifically, the characteristic peak at δ = 7.58 ppm corresponds to the 4 symmetric Hs on the benzene ring close to the imide ring, the characteristic peak at δ = 7.34 ppm corresponds to the 4 symmetric Hs on the benzene ring close to the disulfide bond, and the characteristic peak at δ = 6.83 ppm corresponds to the 4 symmetric Hs on the imide ring. For AM's 13 The chemical shifts in 13C NMR (CDCl3) also correspond one by one to the carbon atoms in AM. Specifically, the characteristic peak at δ = 169.23 ppm corresponds to the C in C=O, the characteristic peak at δ = 136.43 ppm corresponds to the C at the double bond in the bismaleimide ring, the characteristic peak at δ = 126.49 ppm corresponds to the C on the benzene ring connected to N, the characteristic peak at δ = 130.40 ppm corresponds to the C adjacent to the C on the benzene ring connected to S, the characteristic peak at δ = 127.98 ppm corresponds to the C on the benzene ring connected to S, and the characteristic peak at δ = 134.30 ppm corresponds to the C adjacent to the C on the benzene ring connected to N. The high-resolution mass spectrum of AM shows that the measured [M+H + is 409.0322, which is consistent with the theoretical value [M+H + (409.0126).

[0063] The above test results prove that 4,4'-dithiobis(phenylamine) bismaleimide (AM) has been successfully synthesized.

[0064] (2) Synthesis of 4,4'-diallyloxydiphenyl disulfide (DS)

[0065] At room temperature, 4,4'-dihydroxydiphenyl disulfide (15.02 g, 60 mmol), anhydrous K2CO3 (33.17 g, 240 mmol) and acetone (150 mL) were added to a 250 mL three-necked flask, stirred under a nitrogen atmosphere, and 3-bromopropene (21.78 g, 180 mmol) was added dropwise to the flask. After the addition was complete, the mixture was magnetically stirred at 50 °C for 12 h; then the solid insoluble matter was filtered off, and acetone and excess 3-bromopropene were removed by rotary evaporation to obtain a clear yellow oily liquid, which is 4,4'-diallyloxydiphenyl disulfide (DS); Figure 4 Shown are its nuclear magnetic resonance hydrogen spectrum ( 1 1H NMR) and nuclear magnetic resonance carbon spectrum ( 13 13C NMR), Figure 5 Shown is its high-resolution mass spectrum.

[0066] In the 1The characteristic peaks of each H can be found in the 1H NMR (CDCl3). Specifically, the characteristic peak at δ = 7.39 ppm corresponds to the H on the benzene ring close to S, the characteristic peak at δ = 6.85 ppm corresponds to the H on the benzene ring close to O, the characteristic peak at δ = 4.50 ppm corresponds to the H on the carbon connected to O, and the characteristic peaks at δ = 6.03 ppm, 5.42 ppm, and 5.29 ppm correspond to the H of =CH- and the two H of =CH2 on the allyl group respectively. In 13 the 13C NMR spectrum (CDCl3), the characteristic peak at δ = 157.87 ppm corresponds to the C adjacent to O on the benzene ring, the characteristic peak at δ = 131.87 ppm corresponds to the ortho-C of the C connected to S on the benzene ring, the characteristic peak at δ = 114.36 ppm corresponds to the ortho-C of the C connected to O on the benzene ring, the characteristic peak at δ = 131.48 ppm is the CH on the allyl group, the characteristic peak at δ = 116.89 ppm is the CH2 on the allyl group, the characteristic peak at δ = 127.55 ppm is the C adjacent to S on the benzene ring, and the characteristic peak at δ = 67.87 ppm is the C on the CH2 connected to O. The high-resolution mass spectrum of DS shows that the measured [M + H + is 331.0800, which is consistent with the theoretical value [M + H + (331.0646).

[0067] The above test results prove that 4,4'-diallyloxy diphenyl disulfide (DS) has been successfully synthesized.

[0068] Example 1 Preparation of Remoldable and Degradable Bismaleimide Resin

[0069] At 150 °C, 2 g of phenolphthalein polyaryletherketone was dissolved in 4.105 g of 4,4'-diallyloxy diphenyl disulfide, and stirred for 20 min. Then, 5.895 g of 4,4'-dithiobenzidine bismaleimide was added at 130 °C, and melt-prepolymerized at 130 °C for 20 min to obtain a prepolymer. The prepolymer was poured into a preheated conventional mold at 150 °C, vacuum degassed at 150 °C for 50 min, then transferred to an oven, cured according to the process of 150 °C / 2 h + 180 °C / 2 h + 200 °C / 2 h + 220 °C / 2 h, and post-treated at 240 °C for 4 h. Then, it was naturally cooled to room temperature and demolded to obtain a remoldable and degradable bismaleimide resin, denoted as 20cPEK-AD. The loss tangent (Tanδ)-temperature curve, thermogravimetric (TGA) curve, bending strength histogram, stress relaxation curve, digital photos of the remolding process, bending strength histogram after remolding, thermogravimetric (TGA) curve after remolding, digital photos before and after degradation, FTIR spectra of the degradation residue and phenolphthalein polyaryletherketone, FTIR spectra of the degraded and recycled solid (deBMI), digital photos of degradation and recycling, and loss tangent (Tanδ)-temperature curve of the degraded and recycled resin (R-deBMI) are respectively shown in Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11 , Figure 12 , Figure 13 , Figure 14 , Figure 15 , Figure 16 , Figure 17 .

[0070] Example 2 Preparation of Remoldable and Degradable Bismaleimide Resin

[0071] At 150 °C, 1.5 g of phenolphthalein polyaryletherketone was dissolved in 4.105 g of 4,4'-diallyloxydiphenyl disulfide, stirred for 20 min, then 5.895 g of 4,4'-dithiobenzanilide bismaleimide was added at 130 °C, and melt pre-polymerization was carried out at 130 °C for 20 min to obtain a prepolymer; the prepolymer was poured into a conventional mold preheated to 150 °C, vacuum degassed at 150 °C for 50 min and then transferred to an oven, cured according to the process of 150 °C / 2 h + 180 °C / 2 h + 200 °C / 2 h + 220 °C / 2 h, and post-treated at 240 °C for 4 h; then it was naturally cooled to room temperature and demolded to obtain a remoldable and degradable bismaleimide resin, denoted as 15cPEK-AD. The loss tangent (Tanδ)-temperature curve, thermogravimetric (TGA) curve, bending strength histogram, stress relaxation curve, bending strength histogram after remolding, thermogravimetric (TGA) curve after remolding, digital photos before and after degradation, and FTIR spectra of the degradation residue and phenolphthalein polyaryletherketone are respectively shown in Figure 6 and Figure 7 、 Figure 8 、 Figure 9 、 Figure 11 、 Figure 12 、 Figure 13 、 Figure 14 。

[0072] Example 3 Preparation of Remoldable and Degradable Bismaleimide Resin

[0073] At 150 °C, 1 g of phenolphthalein polyaryletherketone was dissolved in 4.105 g of 4,4'-diallyloxydiphenyl disulfide, stirred for 20 min, 5.895 g of 4,4'-dithiobenzanilide bismaleimide was added at 130 °C, and melt pre-polymerization was carried out at 130 °C for 20 min to obtain a prepolymer; the prepolymer was poured into a conventional mold preheated to 150 °C, vacuum degassed at 150 °C for 50 min and then transferred to an oven, cured according to the process of 150 °C / 2 h + 180 °C / 2 h + 200 °C / 2 h + 220 °C / 2 h, and post-treated at 240 °C for 4 h; then it was naturally cooled to room temperature and demolded to obtain a remoldable and degradable bismaleimide resin, denoted as 10cPEK-AD. The loss tangent (Tanδ)-temperature curve, thermogravimetric (TGA) curve, bending strength histogram, stress relaxation curve, bending strength histogram after remolding, thermogravimetric (TGA) curve after remolding, digital photos before and after degradation, and FTIR spectra of the degradation residue and phenolphthalein polyaryletherketone are respectively shown in Figure 6 、 Figure 7 、 Figure 8 、 Figure 9 、 Figure 11 、 Figure 12 、 Figure 13 、 Figure 14 。

[0074] Example 4 Preparation of Remoldable and Degradable Bismaleimide Resin

[0075] At 150 °C, 0.5 g of phenolphthalein polyaryletherketone was dissolved in 4.105 g of 4,4'-diallyloxydiphenyl disulfide, stirred for 20 min, and 5.895 g of 4,4'-dithiobis(aniline bismaleimide) was added at 130 °C. The mixture was pre-polymerized by melting at 130 °C for 20 min to obtain a prepolymer; the prepolymer was poured into a mold preheated to 150 °C, degassed under vacuum at 150 °C for 50 min, and then transferred to an oven. It was cured according to the process of 150 °C / 2 h + 180 °C / 2 h + 200 °C / 2 h + 220 °C / 2 h, and post-treated at 240 °C for 4 h; then it was naturally cooled to room temperature and demolded to obtain a remoldable and degradable bismaleimide resin, denoted as 5cPEK-AD. The loss tangent (Tanδ)-temperature curve, thermogravimetric (TGA) curve, bending strength histogram, stress relaxation curve, bending strength histogram after remolding, thermogravimetric (TGA) curve after remolding, digital photos before and after degradation, and FTIR spectra of the degradation residue and phenolphthalein polyaryletherketone are respectively shown in Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 11 , Figure 12 , Figure 13 , Figure 14 .

[0076] See Appendix Figure 6 , which is the loss tangent (Tanδ)-temperature curve of the remoldable and degradable bismaleimide resin prepared in Examples 1-4 of the present invention in an air atmosphere. The peak temperature of Tanδ is often used as the glass transition temperature (Tg). Generally speaking, Tg represents the upper limit temperature of the use of thermosetting resins. The higher Tg is, the better the heat resistance of the material. Each curve in the figure shows a "main peak + shoulder peak" shape because there are multiphase structures in their network structures. Through simulated peak deconvolution, it can be known that each resin has two Tgs, and the lower temperature Tg (Tg1) > 200 °C (Table 1). Compared with the prior art, the Tg of remoldable and degradable bismaleimide resins is generally lower than 180 °C. The remoldable and degradable bismaleimide resin described in the present invention has outstanding heat resistance.

[0077] See Appendix Figure 7 , which is the TGA curve (10 °C / min) of the remoldable and degradable bismaleimide resin prepared in Examples 1-4 of the present invention in a nitrogen atmosphere. The obtained initial thermal decomposition temperature (T di , the temperature at 5 wt% weight loss) is often used to evaluate the thermal stability of the resin. As can be seen from Table 1, with the increase of cPEK, the change of the resin is not significant, but they are all higher than T of Comparative Example 1di (300.8 °C), indicating that the present invention is beneficial to improving thermal stability.

[0078] Table 1 Heat resistance properties of the remoldable and degradable bismaleimide resins prepared in Examples 1-4

[0079]

[0080] Preparation of bismaleimide resin in Comparative Example 1

[0081] At 130 °C, 5.895 g of 4,4'-dithiobis(diphenylamine) bismaleimide was added to 4.105 g of 4,4'-diallyloxydiphenyl disulfide, and melt-prepolymerized for 20 min to obtain a prepolymer; the prepolymer was poured into a mold preheated to 150 °C, vacuum degassed at 150 °C for 50 min, then transferred to an oven, cured according to the process of 150 °C / 2 h + 180 °C / 2 h + 200 °C / 2 h + 220 °C / 2 h, and post-treated at 240 °C for 4 h; then cooled naturally to room temperature, demolded, to obtain a bismaleimide resin, denoted as AD. The bar chart of flexural strength, stress relaxation curve and digital photos before and after degradation are shown respectively in Figure 8 , Figure 9 , Figure 13 .

[0082] See Appendix Figure 8 , which is the bar chart of flexural strength of the remoldable and degradable bismaleimide resins prepared in Examples 1-4 of the present invention and the bismaleimide resin prepared in Comparative Example 1. Since flexural stress includes stresses such as bending, tension, compression and other forms, flexural strength reflects the comprehensive mechanical properties of the resin. It can be seen therefrom that the flexural strength of the remoldable and degradable bismaleimide resins prepared in Examples 1-4 is significantly higher than that of the bismaleimide resin prepared in Comparative Example 1, indicating that the resin of the present invention has both high rigidity and good toughness.

[0083] See Appendix Figure 9 , which is the stress relaxation curve of the remoldable and degradable bismaleimide resins prepared in Examples 1-4 of the present invention and the bismaleimide resin prepared in Comparative Example 1. It can be seen therefrom that, compared with Comparative Example 1, the remoldable and degradable bismaleimide resins prepared in Examples 1-4 can relax to 1 / e faster, indicating that the present invention enhances the segmental motion ability of the resin and promotes the disulfide bond exchange reaction.

[0084] Example 5 Remolding of the remoldable and degradable bismaleimide resin

[0085] See Appendix Figure 10, which is a digital photo of the remodeling process of the remodelable and degradable bismaleimide resin prepared in Example 1. The conventional crushed bismaleimide resin was hot pressed at a temperature of 240°C and a pressure of 20MPa for 2h; after natural cooling and demolding, the remodeled bismaleimide resin was obtained, which was recorded as rem-20cPEK-AD. The surface of the rem-20cPEK-AD resin block is smooth and free of cracks, indicating that the resin particles have undergone a dynamic reaction to reconnect the particles. This result fully proves that the bismaleimide resin prepared in Example 1 can be remodeled.

[0086] Referring to the above method, remodeling experiments were also carried out on the 15cPEK-AD, 10cPEK-AD and 5cPEK-AD resins prepared in Examples 2-4, and the obtained remodeled resins were respectively recorded as rem-15cPEK-AD, rem-10cPEK-AD and rem-5cPEK-AD.

[0087] See attached Figure 11 , which is a bar graph of the bending strength of rem-20cPEK-AD, rem-15cPEK-AD, rem-10cPEK-AD, and rem-5cPEK-AD, further illustrating that disulfide bond bismaleimide combined with phenolphthalein poly(aryletherketone) enhances the segment mobility of the resin and promotes the exchange reaction of disulfide bonds, thereby ensuring that the reshaped resin has high mechanical properties.

[0088] See attached Figure 12 , which are the TGA curves of rem-20cPEK-AD, rem-15cPEK-AD, rem-10cPEK-AD and rem-5cPEK-AD, from which the T di They are 307.9, 312.1, 308.1, and 309.5°C, respectively. By comparing with Table 1, it can be seen that the T di This indicates that the remodeling process does not deteriorate the thermal stability of the original resin.

[0089] Comparative Example 2 Preparation of 4,4'-diallyloxydiphenyl disulfide modified bismaleimide resin

[0090] 11.15 g (31.1 mmol) of N,N'-4,4'-diphenylmethane bismaleimide and 8.85 g (26.6 mmol) of 4,4'-diallyloxydiphenyl disulfide were mixed and melt-prepolymerized at 130°C for 20 min to obtain a clarified prepolymer; the prepolymer was poured into a mold preheated at 150°C, and after vacuum degassing at 150°C for 50 min, it was moved into an oven and cured according to the process of 150°C / 2h+180°C / 2h+200°C / 2h+220°C / 2h, and post-treated at 240°C for 4h; then it was naturally cooled to room temperature and demolded to obtain 4,4'-diallyloxydiphenyl disulfide modified bismaleimide resin, recorded as ABD.

[0091] Example 6 Degradation of remodelable and degradable bismaleimide resin

[0092] Place a small piece of resin (120-130 mg) into 10 mL of DMF / β-mercaptoethanol (volume ratio 2:1) mixed solution at 120°C with normal stirring. Figure 13 , which is a digital photo of the degradation of six resins, 20cPEK-AD (Example 1), 15cPEK-AD (Example 2), 10cPEK-AD (Example 3), 5cPEK-AD (Example 4), AD (Comparative Example 1), and ABD (Comparative Example 2) in a solvent. The BMI resin blocks prepared in Examples 1-4 have a faster degradation efficiency. The resin blocks completely disappear at 14min, 18min, 21min, and 22min, respectively. The color of the solution changes from colorless to yellow-brown, with a small amount of white flocs floating in it; the solution is filtered to obtain a clear solution A and white flocs B.

[0093] The white floccules B obtained in Examples 1 to 4 were washed and dried, and their FTIR spectra were consistent with those of phenolphthalein polyaryletherketone. Figure 14 , indicating that the white floccules B are phenolphthalein polyaryletherketone. Moreover, the white floccules B can be completely dissolved in dichloromethane at room temperature, indicating that the resin of the present invention can be completely degraded.

[0094] The clear solution A was evaporated at 150 °C to obtain a solid, which was then ground into a solid powder (denoted as deBMI) by conventional grinding.

[0095] See attached Figure 15 , which is the FTIR spectrum of the 20cPEK-AD resin and its deBMI prepared in Example 1 of the present invention. It can be seen from the infrared spectrum of deBMI at 2555cm -1 The -SH peak appears at , indicating that the disulfide bonds in the bismaleimide resin undergo an exchange reaction with the thiol in the solvent, proving that the 20cPEK-AD resin prepared in Example 1 is degraded in the above solution instead of being dissolved.

[0096] The above experiments prove that the BMI resins prepared in Examples 1-4 can be completely degraded in solution.

[0097] The AD resin block prepared in Comparative Example 1 completely disappeared at 65 min, and the color of the solvent changed from colorless to tawny, indicating that AD can also be degraded in the solvent, but the degradation efficiency is lower than that of the cPEK-AD series resins prepared in Examples 1-4, indicating that the present invention enhances the chain segment movement ability of the resin and improves the degradation efficiency.

[0098] The ABD resin block prepared in Comparative Example 2 showed no obvious change after 3 h, indicating that it is not degradable.

[0099] Combining the degradation results of Examples 1-4 and Comparative Example 1, it can be seen that the degradation of the BMI resin depends not only on the content of reversible dynamic bonds, but also on the chain segment movement ability.

[0100] See Appendix Figure 16 , which is a digital photo of the post-degradation molding recovery process of the 20cPEK-AD resin prepared in Example 1 of the present invention. The obtained solid powder deBMI was hot-pressed at a temperature of 220 °C and a pressure of 15 MPa for 2 h to obtain a molded recovered resin, denoted as R-deBMI. Its surface is smooth and free of cracks, indicating that dynamic disulfide bond exchange reactions occurred in the resin particles, thereby reconnecting the particles. This result fully proves that the bismaleimide resin prepared in the present invention can achieve molding recovery after solution degradation.

[0101] See Appendix Figure 17 , which is the loss tangent (Tanδ)-temperature curve of the resin R-deBMI obtained by molding recovery after degradation of the 20cPEK-AD resin prepared in Example 1 above. It can be seen from this that the Tg of R-deBMI is 250 °C, which is higher than the Tg value of existing remoldable and degradable bismaleimide resins.

[0102] Example 7 Preparation of Remoldable and Degradable Bismaleimide Resin

[0103] At 150 °C, 2 g of phenolphthalein polyaryletherketone was dissolved in 4.105 g of 4,4'-diallyloxy diphenyl disulfide, stirred for 20 min, 5.895 g of 4,4'-dithiobenzanilide bismaleimide was added at 130 °C, and melt pre-polymerization was carried out at 130 °C for 20 min to obtain a prepolymer; the prepolymer was poured into a mold preheated to 150 °C, vacuum degassed at 140 °C for 50 min and then transferred to an oven, cured according to the process of 150 °C / 2 h + 180 °C / 2 h + 200 °C / 2 h + 220 °C / 2 h, and post-treated at 240 °C for 4 h; after curing, it was naturally cooled to room temperature, demolded, and a remoldable and degradable bismaleimide resin was obtained.

[0104] Example 8 Preparation of Remoldable and Degradable Bismaleimide Resin

[0105] At 140 °C, 2 g of phenolphthalein polyaryletherketone was dissolved in 4.105 g of 4,4'-diallyloxy diphenyl disulfide, stirred for 20 min, 5.895 g of 4,4'-dithiobenzanilide bismaleimide was added at 130 °C, and melt pre-polymerization was carried out at 130 °C for 20 min to obtain a prepolymer; the prepolymer was poured into a mold preheated to 140 °C, vacuum degassed at 140 °C for 50 min and then transferred to an oven, cured according to the process of 150 °C / 2 h + 180 °C / 2 h + 200 °C / 2 h + 220 °C / 2 h, and post-treated at 240 °C for 4 h; then it was naturally cooled to room temperature, demolded, and a remoldable and degradable bismaleimide resin was obtained.

[0106] The applicant has previously disclosed the research on high-performance remoldable shape memory thermosetting resins, remoldable high-performance bismaleimide resin films, and high heat-resistant and high-strength recyclable thermosetting resins based on dynamic covalent bonds. Although some have remolding properties, they are all difficult to degrade in conventional solvents; the present invention discloses a remoldable and degradable bismaleimide resin, and its preparation method is through the copolymerization of 4,4'-dithiobenzanilide bismaleimide (AM), 4,4'-diallyloxy diphenyl disulfide (DS) and phenolphthalein polyaryletherketone. The bismaleimide resin prepared by the present invention not only has excellent heat resistance, but also can be remolded under hot pressing conditions; it can be completely degraded rapidly in a conventional solvent (a mixed solution of DMF / β-mercaptoethanol), and by evaporating the solvent from the degradation solution and heating and pressurizing, closed-loop recycling can be achieved, overcoming the deficiency that bismaleimide resins containing reversible covalent bonds are difficult to combine high heat resistance, remoldability and degradability, and providing a new resin and preparation strategy for the sustainable development of heat-resistant thermosetting resins.

Claims

1. A remodelable and degradable bismaleimide resin, characterized in that: The raw materials for preparing the remodelable and degradable bismaleimide resin include 4,4'-diallyloxydiphenyl disulfide, phenolphthalein polyaryletherketone, and 4,4'-dithiodiphenylamine bismaleimide.

2. The remodelable and degradable bismaleimide resin according to claim 1, characterized in that: The mass ratio of the monomer to the phenolphthalein polyaryletherketone is 1:(0.05-0.2); the monomer is 4,4'-diallyloxydiphenyl disulfide and 4,4'-dithiodiphenylamine bismaleimide, and the molar ratio of 4,4'-diallyloxydiphenyl disulfide to 4,4'-dithiodiphenylamine bismaleimide is (0.5-1):

1.

3. The method for preparing the remodelable and degradable bismaleimide resin according to claim 1, characterized in that: The method comprises the following steps: mixing the raw materials for preparing the remodelable and degradable bismaleimide resin, and then curing the mixture to obtain the remodelable and degradable bismaleimide resin.

4. The method for preparing the remodelable and degradable bismaleimide resin according to claim 3, characterized in that: Phenolphthalein polyaryletherketone and 4,4'-diallyloxydiphenyl disulfide are mixed at 100-180°C, and then 4,4'-dithiodiphenylamine bismaleimide is added, mixed at 100-150°C, and then cured to obtain a remodelable and degradable bismaleimide resin.

5. The method for preparing the remodelable and degradable bismaleimide resin according to claim 3, characterized in that: The curing temperature is 150-240°C, the time is 8-15 hours, and the curing adopts step-by-step temperature increase.

6. A method for preparing a remodelable and degradable bismaleimide resin prepolymer, characterized in that: The method comprises the following steps: mixing raw materials for preparing a remodelable and degradable bismaleimide resin to obtain a remodelable and degradable bismaleimide resin prepolymer; the raw materials for preparing the remodelable and degradable bismaleimide resin comprise 4,4'-diallyloxydiphenyl disulfide, phenolphthalein polyaryletherketone, and 4,4'-dithiodiphenylamine bismaleimide.

7. Use of the remodelable and degradable bismaleimide resin according to claim 1 in the preparation of or as a bismaleimide resin material.

8. The remodeling method of the remodelable and degradable bismaleimide resin according to claim 1, characterized in that: The method comprises the following steps: hot pressing the crushed remodelable and degradable bismaleimide resin to achieve the remodeling of the remodelable and degradable bismaleimide resin.

9. The method for degrading the remodelable and degradable bismaleimide resin according to claim 1, characterized in that: The method comprises the following steps: placing the remodelable and degradable bismaleimide resin in a solvent to achieve degradation of the remodelable and degradable bismaleimide resin.

10. The method for recycling the remodelable and degradable bismaleimide resin according to claim 1, characterized in that: The method comprises the following steps: placing the remodelable and degradable bismaleimide resin in a solvent for degradation, and then removing the solvent to achieve the recovery of the remodelable and degradable bismaleimide resin.

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