Remodelable and degradable bismaleimide resin and preparation method thereof

Abstract

The invention discloses a remodelable and degradable bismaleimide resin and a preparation method thereof, and the remodelable and degradable bismaleimide resin is prepared from 4, 4 '-dithio diphenylamine bismaleimide (AM), 4, 4'-diallyloxy diphenyl disulfide (DS) and phenolphthalein polyaryletherketone. The bismaleimide resin prepared by the preparation method disclosed by the invention not only has excellent heat resistance, but also can be remodeled under a hot-pressing condition; the bismaleimide resin containing the reversible covalent bond can be quickly degraded in a conventional solvent, and closed-loop recovery can be realized by evaporating the solvent from the degraded solution and heating and pressurizing, so that the defect that the bismaleimide resin containing the reversible covalent bond is difficult to have high heat resistance, remodeling and degradability at the same time is overcome, and a new resin and preparation strategy is provided for sustainable development of the heat-resistant thermosetting resin.

Description

Technical Field

[0001] The invention relates to a thermosetting resin and a preparation method thereof, in particular to a remodelable and degradable bismaleimide resin and a preparation, remodeling and degradation recovery method thereof, belonging to the field of functional polymer materials. Background Art

[0002] Bismaleimide (BMI) resin is a typical heat-resistant thermosetting resin, which has been widely used in cutting-edge technology fields such as aerospace, transportation, and information. As a thermosetting resin, BMI resin is difficult to repair and recycle after curing due to its "insoluble and infusible" characteristics. Therefore, the research and development of remodelable and degradable thermosetting resins has attracted widespread attention in recent years. Through reversible covalent bond technology, people have achieved the remodelability and degradability of various thermosetting resins, but the relevant research on BMI resin is still in its infancy.

[0003] There are almost no reports on remodelable bismaleimide resins that are also degradable. The prior art discloses a BMI resin obtained by copolymerizing an aryl allyl ether compound containing a disulfide bond with 4,4'-maleimidodiphenylmethane (BDM). Although the obtained BMI resin has a high crosslinking density and has reversible dynamic covalent bonds, it cannot be degraded (see the literature: Research on high-performance intrinsic flame-retardant bismaleimide resins containing disulfide bonds and their remodeling properties). The prior art uses BDM, 4-aminophenyl sulfide and aliphatic polyether diamine copolymerization to obtain a remodelable BMI resin, and its remodeling efficiency is only 8%, and there is no report of degradation (see the literature: Reprocessable bismaleimide-diamine thermosets based on disulfide bonds).

[0004] Prior art CN118930851A prepared a BMI resin degradable in aqueous nitric acid solution by copolymerizing triamine containing an acid-sensitive hexahydrotriazine ring structure, 2,2-bis[4-(4-aminophenoxy)phenyl]propane and BDM, but no remodeling was observed, and the resin preparation required the use of solvents such as DMF. Prior art discloses a degradation of BMI resin, which requires 12 hours in a toluene solution containing an excess of mercapto(dimethoxy)methylsilane (DP970) to achieve complete degradation (see reference: 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'-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.

[0015] Preferably, phenolphthalein polyaryletherketone and 4,4'-diallyloxydiphenyl disulfide are mixed and stirred at 120-170°C for 5-60 minutes, and then 4,4'-dithiodiphenylamine bismaleimide is added, mixed and stirred at 110-140°C for 5-45 minutes, and then cured to obtain a remodelable and degradable bismaleimide resin.

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

[0017] The invention discloses a method for preparing a remodelable and degradable bismaleimide resin prepolymer, comprising the following steps: mixing raw materials for preparing the 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 include 4,4'-diallyloxydiphenyl disulfide, phenolphthalein polyaryletherketone, and 4,4'-dithiodiphenylamine bismaleimide. Preferably, the raw materials for preparing the remodelable and degradable bismaleimide resin are 4,4'-diallyloxydiphenyl disulfide, phenolphthalein polyaryletherketone, and 4,4'-dithiodiphenylamine bismaleimide.

[0018] The present invention discloses the use of the above-mentioned remodelable and degradable bismaleimide resin in the preparation or as a bismaleimide resin material. The bismaleimide resin material can be a bismaleimide resin material with an inorganic filler added, a bismaleimide resin material composited with a reinforcing material, a bismaleimide resin material composited with other resins, etc. The reinforcing material includes a fiber material, such as fiber or fiber fabric (fiber cloth), etc.

[0019] The invention discloses a remodeling method of the remodelable and degradable bismaleimide resin, comprising the following steps: hot pressing the crushed remodelable and degradable bismaleimide resin to achieve the remodeling of the remodelable and degradable bismaleimide resin.

[0020] The invention discloses a degradation method of the remodelable and degradable bismaleimide resin, comprising the following steps: placing the remodelable and degradable bismaleimide resin in a solvent to achieve degradation of the remodelable 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: 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).

[0024] 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.

[0025] 3. The BMI resin prepared by the present invention has strong segment mobility, is degradable and has improved degradation efficiency.

[0026] 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

[0027] 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.

[0028] 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).

[0029] Figure 3 It is the mass spectrum of 4,4'-dithiodiphenylamine bismaleimide of the present invention.

[0030] 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).

[0031] Figure 5It is the mass spectrum of 4,4'-diallyloxydiphenyl disulfide of the present invention.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] Fig. 9 It is the stress relaxation curve of the remodelable and degradable bismaleimide resin prepared in Examples 1-4 of the present invention.

[0036] Fig.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.

[0037] Fig.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.

[0038] Fig.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.

[0039] Fig.13 These are digital photos of the remodelable and degradable bismaleimide resin prepared in Examples 1-4 of the present invention before and after degradation.

[0040] Fig.14 FTIR spectra of the degradation residues of the bismaleimide resin prepared in Examples 1-4 of the present invention and phenolphthalein polyaryletherketone.

[0041] Fig.15 FTIR spectra of the bismaleimide resin and its degradation product (deBMI) prepared in Example 1 of the present invention.

[0042] Fig.16 This is a digital photo of the degradation and recovery of the bismaleimide resin prepared in Example 1 of the present invention.

[0043] Fig.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

[0044] The present invention discloses a method for preparing the above-mentioned remodelable and degradable bismaleimide resin, comprising the following steps: Using maleic anhydride and 4,4'-diaminodiphenyl disulfide as raw materials, 4,4'-dithiodiphenylamine bismaleimide (AM) was obtained through acylation reaction; Using 3-bromopropylene and 4,4'-dihydroxydiphenyl disulfide as raw materials, 4,4'-diallyloxydiphenyl disulfide (DS) was obtained through substitution reaction; 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] The method for recovering the remodelable and degradable bismaleimide resin of the present invention comprises the following steps: degrading the remodelable and degradable bismaleimide resin in a mixed solution of N,N-dimethylformamide (DMF) and β-mercaptoethanol, removing the solvent from the obtained solution, obtaining resin powder, and realizing the recovery of the remodelable and degradable bismaleimide resin.

[0050] Furthermore, the powder is heated and pressurized again to achieve the remodeling of the remodelable and degradable bismaleimide resin after recovery.

[0051] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments. The raw materials used in the present invention are existing products, and the specific preparation operations and performance tests are all conventional techniques.

[0052] Phenolphthalein polyaryletherketone (cPEK, number average molecular weight is 40000), Xuzhou Aviation Material Engineering Plastics Factory, its chemical structure is as follows: .

[0053] Synthesis example FIG1 is a synthetic reaction formula and chemical structure formula of 4,4'-dithiodiphenylamine bismaleimide and 4,4'-diallyloxydiphenyl disulfide.

[0054] (1) Synthesis of 4,4'-dithiodiphenylamine bismaleimide At room temperature, maleic anhydride (6.33 g, 64.6 mmol) was dissolved in acetone (80 mL) solution, stirred at room temperature under nitrogen atmosphere, and a mixed solution of 4,4'-dithiodiphenylamine (8.01 g, 32.3 mmol) and acetone (120 mL) was added dropwise through a constant pressure funnel. After the addition was completed, the mixture was stirred at room temperature for 4 h, and then sodium acetate (2.525 g, 30.75 mmol) and acetic anhydride (25 mL) were added. The mixture was stirred at 85 ° C in nitrogen atmosphere for 4 h, and then naturally cooled to room temperature, precipitated in cold water, filtered, and 5% NaHCO 3 The solid obtained by filtration was dissolved in dichloromethane (DCM), washed with water three times, and then washed with anhydrous MgSO 4 The brown product was dried and the solvent was removed by rotary evaporation. The product was dried in a conventional manner to obtain a yellow powder, which was 4,4'-dithiodiphenylamine bismaleimide (AM). Figure 2 Its H NMR spectrum ( 1 H NMR) and hydrogen nuclear magnetic resonance spectroscopy ( 13 C NMR), Figure 3 This is its high-resolution mass spectrum.

[0055] In AM 1 H NMR (CDCl 3) can find the characteristic peak of each H. Specifically, the characteristic peak at δ = 7.58 ppm corresponds to the symmetrical 4 H on the benzene ring close to the imide ring, the characteristic peak at δ = 7.34 ppm corresponds to the symmetrical 4 H on the benzene ring close to the disulfide bond, and the characteristic peak at δ = 6.83 ppm corresponds to the symmetrical 4 H on the imide ring. AM 13 C NMR (CDCl 3 ) also correspond to the carbon atoms in AM. Specifically, the characteristic peak at δ=169.23ppm corresponds to the C on C=O, the characteristic peak at δ=136.43ppm corresponds to the C at the double bond on the bismaleimide ring, the characteristic peak at δ=126.49ppm corresponds to the C connected to N on the benzene ring, the characteristic peak at δ=130.40ppm corresponds to the C ortho-C connected to S on the benzene ring, the characteristic peak at δ=127.98ppm corresponds to the C connected to S on the benzene ring, and the characteristic peak at δ=134.30ppm corresponds to the C ortho-C connected to N in the benzene ring. The high-resolution mass spectrum of AM shows that the [M+H + ] is 409.0322, which is consistent with the theoretical value [M+H + ](409.0126).

[0056] The above test results prove that 4,4'-dithiodiphenylamine bismaleimide (AM) has been successfully synthesized.

[0057] (2) Synthesis of 4,4'-diallyloxydiphenyl disulfide (DS) At room temperature, 4,4'-dihydroxydiphenyl disulfide (15.02 g, 60 mmol), anhydrous K 2 CO 3 (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-bromopropylene (21.78 g, 180 mmol) was added dropwise to the flask. After the addition was completed, the reaction was continued at 50 ° C with magnetic stirring for 12 h; then the solid insoluble matter was filtered out, and the acetone and excess 3-bromopropylene were removed by rotary evaporation to obtain a clear yellow oily liquid, which was 4,4'-diallyloxydiphenyl disulfide (DS); Figure 4 Its H NMR spectrum ( 1 H NMR) and hydrogen nuclear magnetic resonance spectroscopy ( 13 C NMR), Figure 5 This is its high-resolution mass spectrum.

[0058] In DS 1 H NMR (CDCl 3) can be found in the characteristic peak of each H. Specifically, the characteristic peak at δ=7.39ppm corresponds to the H on the benzene ring close to S, the characteristic peak at δ=6.85ppm corresponds to the H on the benzene ring close to O, the characteristic peak at δ=4.50ppm corresponds to the H on the carbon connected to O, and the characteristic peaks at δ=6.03ppm, 5.42ppm and 5.29ppm correspond to the H of =CH- on the allyl group and =CH 2 The two Hs on 13 C NMR spectrum (CDCl 3 ), 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, and the characteristic peak at δ = 116.89 ppm is the CH on the allyl group. 2 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 CH connected to O. 2 The high-resolution mass spectrometry of DS showed that the [M+H + ] is 331.0800, which is consistent with the theoretical value [M+H + ](331.0646)is consistent.

[0059] The above test results prove that 4,4'-diallyloxydiphenyl disulfide (DS) has been successfully synthesized.

[0060] Example 1 Preparation of remodelable and degradable bismaleimide resin At 150°C, 2g of phenolphthalein polyaryletherketone was dissolved in 4.105g of 4,4'-diallyloxydiphenyl disulfide and stirred for 20min, and then 5.895g of 4,4'-dithiodiphenylamine bismaleimide was added at 130°C, and melt prepolymerized at 130°C for 20min to obtain a prepolymer; the prepolymer was poured into a conventional mold preheated at 150°C, and after vacuum degassing at 150°C for 50min, 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, demolded, and a reshapeable and degradable bismaleimide resin was obtained, which was recorded as 20cPEK-AD. Its loss tangent (Tanδ)-temperature curve, thermal gravimetric analysis (TGA) curve, bending strength bar graph, stress relaxation curve, digital photos of the reshaping process, bending strength bar graph after reshaping, thermal gravimetric analysis (TGA) curve after reshaping, digital photos before and after degradation, FTIR spectra of degradation residues and phenolphthalein poly(aryletherketone), FTIR spectrum of degradation-recovered solid (deBMI), degradation and recovery digital photos, and loss tangent (Tanδ)-temperature curve of degradation-recovered resin (R-deBMI) are respectively shown in Figure 6 , Figure 7 , Figure 8 , Fig. 9 , Fig.10 , Fig.11 , Fig.12 , Fig.13 , Fig.14 , Fig.15 , Fig.16 , Fig.17 .

[0061] Example 2 Preparation of remodelable and degradable bismaleimide resin At 150°C, 1.5g of phenolphthalein polyaryletherketone was dissolved in 4.105g of 4,4'-diallyloxydiphenyl disulfide and stirred for 20min, and then 5.895g of 4,4'-dithiodiphenylamine bismaleimide was added at 130°C, and melt prepolymerized at 130°C for 20min to obtain a prepolymer; the prepolymer was poured into a conventional mold preheated at 150°C, and after vacuum degassing at 150°C for 50min, 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, demolded, and a reshapeable and degradable bismaleimide resin was obtained, which was recorded as 15cPEK-AD. Its loss tangent (Tanδ)-temperature curve, thermal gravimetric analysis (TGA) curve, bending strength bar graph, stress relaxation curve, bending strength bar graph after remodeling, thermal gravimetric analysis (TGA) curve after remodeling, digital photos before and after degradation, and FTIR spectra of degradation residues and phenolphthalein poly(aryletherketone) are respectively shown in Figure 6 , Figure 7 , Figure 8 , Fig. 9 , Fig.11 , Fig.12 , Fig.13 , Fig.14 .

[0062] Example 3 Preparation of remodelable and degradable bismaleimide resin At 150°C, 1g of phenolphthalein polyaryletherketone was dissolved in 4.105g of 4,4'-diallyloxydiphenyl disulfide, stirred for 20min, and 5.895g of 4,4'-dithiodiphenylamine bismaleimide was added at 130°C, and melt prepolymerized at 130°C for 20min to obtain a prepolymer; the prepolymer was poured into a conventional mold preheated at 150°C, and after vacuum degassing at 150°C for 50min, 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, demolded, and a reshapeable and degradable bismaleimide resin was obtained, which was recorded as 10cPEK-AD. Its loss tangent (Tanδ)-temperature curve, thermal gravimetric analysis (TGA) curve, bending strength bar graph, stress relaxation curve, bending strength bar graph after remodeling, thermal gravimetric analysis (TGA) curve after remodeling, digital photos before and after degradation, and FTIR spectra of degradation residues and phenolphthalein poly(aryletherketone) are respectively shown in Figure 6 , Figure 7 , Figure 8 , Fig. 9 , Fig.11 , Fig.12 , Fig.13 , Fig.14 .

[0063] Example 4 Preparation of remodelable and degradable bismaleimide resin At 150°C, 0.5g of phenolphthalein polyaryletherketone was dissolved in 4.105g of 4,4'-diallyloxydiphenyl disulfide, stirred for 20min, and 5.895g of 4,4'-dithiodiphenylamine bismaleimide was added at 130°C, and melt prepolymerized at 130°C for 20min to obtain a prepolymer; the prepolymer was poured into a mold preheated at 150°C, and after vacuum degassing at 150°C for 50min, 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, demolded, and a reshapeable and degradable bismaleimide resin was obtained, which was recorded as 5cPEK-AD. Its loss tangent (Tanδ)-temperature curve, thermal gravimetric analysis (TGA) curve, bending strength bar graph, stress relaxation curve, bending strength bar graph after remodeling, thermal gravimetric analysis (TGA) curve after remodeling, digital photos before and after degradation, and FTIR spectra of degradation residues and phenolphthalein poly(aryletherketone) are respectively shown in Figure 6 , Figure 7 , Figure 8 , Fig. 9 , Fig.11 , Fig.12 , Fig.13 , Fig.14 .

[0064] See attached Figure 6 , which is the loss tangent (Tanδ)-temperature curve of the remodelable and degradable bismaleimide resin prepared in Examples 1-4 of the present invention in air atmosphere, where the peak temperature of Tanδ is often used as the glass transition temperature (Tg). Generally speaking, Tg represents the upper limit temperature of thermosetting resin. The higher the Tg, the better the heat resistance of the material. Each curve in the figure shows a peak shape of "main peak + shoulder peak" because there is a multiphase structure in their network structure. After simulating the peak separation, it can be seen that each resin has two Tgs, of which the lower temperature Tg (Tg 1 )>200℃ (Table 1). Compared with the prior art remodelable and degradable bismaleimide resin whose Tg is generally lower than 180℃, the remodelable and degradable bismaleimide resin of the present invention has outstanding heat resistance.

[0065] See attached Figure 7 , which is the TGA curve (10°C / min) of the remodelable and degradable bismaleimide resin prepared in Example 1-4 of the present invention under a nitrogen atmosphere, wherein the initial thermal decomposition temperature (T di , the temperature at which the weight loss is 5 wt% 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 large, but it is higher than the T of Comparative Example 1. di (300.8°C), indicating that the present invention is beneficial to improving thermal stability.

[0066] Table 1 Heat resistance of remodelable and degradable bismaleimide resin prepared in Examples 1-4

[0067] Comparative Example 1 Preparation of bismaleimide resin At 130°C, 5.895 g of 4,4'-dithiodiphenylamine 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 at 150°C, and after vacuum degassing at 150°C for 50 min, it was moved into an oven and cured according to a 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, demolded, and a bismaleimide resin was obtained, denoted as AD, and its bending strength bar graph, stress relaxation curve, and digital photos before and after degradation are respectively shown in Figure 8 , Fig. 9 , Fig.13 .

[0068] See attached Figure 8 , which is a bar graph of the bending strength of the remodelable and degradable bismaleimide resins prepared in Examples 1-4 of the present invention and the bismaleimide resin prepared in Comparative Example 1. Since bending stress includes bending, stretching, compression and other forms of stress, the bending strength reflects the comprehensive mechanical properties of the resin. It can be seen that the bending strength of the remodelable 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.

[0069] See attached Fig. 9 , which is the stress relaxation curve of the remodelable and degradable bismaleimide resin prepared in Examples 1-4 of the present invention and the bismaleimide resin prepared in Comparative Example 1. It can be seen that compared with Comparative Example 1, the remodelable and degradable bismaleimide resin prepared in Examples 1-4 can relax to 1 / e faster, indicating that the present invention enhances the segment mobility of the resin and promotes the exchange reaction of disulfide bonds.

[0070] Example 5 Remodeling of remodelable and degradable bismaleimide resin See attached Fig.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.

[0071] 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.

[0072] See attached Fig.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.

[0073] See attached Fig.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.

[0074] Comparative Example 2 Preparation of 4,4'-diallyloxydiphenyl disulfide modified bismaleimide resin 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.

[0075] Example 6 Degradation of remodelable and degradable bismaleimide resin 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. Fig.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.

[0076] 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. Fig.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.

[0077] 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.

[0078] See attached Fig.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.

[0079] The above experiments prove that the BMI resins prepared in Examples 1-4 can be completely degraded in solution.

[0080] The AD resin block prepared in Comparative Example 1 completely disappeared at 65 minutes, and the color of the solvent changed from colorless to yellow-brown, 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 mobility of the resin and improves the degradation efficiency.

[0081] The ABD resin block prepared in Comparative Example 2 showed no obvious changes after 3 hours, indicating that it is non-degradable.

[0082] Combining the degradation results of Examples 1-4 and Comparative Example 1, it can be seen that the degradation of BMI resin depends not only on the content of reversible dynamic bonds, but also on the mobility of the chain segments.

[0083] See attached Fig.16 , which is a digital photo of the compression molding recovery process of the 20cPEK-AD resin prepared in Example 1 of the present invention after degradation. The solid powder deBMI obtained above was hot pressed at a temperature of 220°C and a pressure of 15MPa for 2h to obtain a compression molding recovery resin, which was recorded as R-deBMI. Its surface was smooth and crack-free, indicating that the resin particles underwent a dynamic disulfide bond exchange reaction, thereby reconnecting the particles. This result fully proves that the bismaleimide resin prepared by the present invention can be recycled by compression molding after solution degradation.

[0084] See attached Fig.17 , which is the loss tangent (Tanδ)-temperature curve of the resin R-deBMI obtained by molding and recycling the 20cPEK-AD resin prepared in the above Example 1 after degradation. It can be seen that the Tg of R-deBMI is 250°C, which is higher than the Tg value of the existing remodelable and degradable bismaleimide resin.

[0085] Example 7 Preparation of remodelable and degradable bismaleimide resin At 150°C, 2g of phenolphthalein polyaryletherketone was dissolved in 4.105g of 4,4'-diallyloxydiphenyl disulfide, stirred for 20min, 5.895g of 4,4'-dithiodiphenylamine bismaleimide was added at 130°C, and melt prepolymerized at 130°C for 20min to obtain a prepolymer; the prepolymer was poured into a mold preheated at 150°C, and after vacuum degassing at 140°C for 50min, 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; after the curing was completed, it was naturally cooled to room temperature, demolded, and a reshapeable and degradable bismaleimide resin was obtained.

[0086] Example 8 Preparation of remodelable and degradable bismaleimide resin At 140°C, 2g of phenolphthalein polyaryletherketone was dissolved in 4.105g of 4,4'-diallyloxydiphenyl disulfide, and stirred for 20min. At 130°C, 5.895g of 4,4'-dithiodiphenylamine bismaleimide was added, and melt prepolymerization was carried out at 130°C for 20min to obtain a prepolymer. The prepolymer was poured into a mold preheated at 140°C, and after vacuum degassing at 140°C for 50min, 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, demolded, and a reshapeable and degradable bismaleimide resin was obtained.

[0087] The applicant has previously disclosed research on high-performance reshapeable shape memory thermosetting resins, reshapeable high-performance bismaleimide resin films, and high-heat-resistant, high-strength recyclable thermosetting resins based on dynamic covalent bonds. Although some of them have reshape properties, they are difficult to degrade in conventional solvents. The present invention discloses a reshapeable and degradable bismaleimide resin, the preparation method of which is through the blending and copolymerization of 4,4'-dithiodiphenylamine bismaleimide (AM), 4,4'-diallyloxydiphenyl disulfide (DS) and phenolphthalein polyaryletherketone. The bismaleimide resin prepared by the present invention not only has excellent heat resistance, but also can be reshaped under hot pressing conditions; it can achieve relatively fast and complete degradation in a conventional solvent (a mixed solution of DMF / β-mercaptoethanol), and the degradation solution is evaporated of the solvent, heated and pressurized to achieve closed-loop recovery, thereby overcoming the shortcomings of bismaleimide resins containing reversible covalent bonds that it is difficult to have high heat resistance, reshapeability and degradability at the same time, and providing new resins and preparation strategies for achieving 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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