Active ester curing agent with imine bond, preparation method and application thereof

Abstract

The present invention relates to the field of polymer materials, and discloses an active ester curing agent with an imine bond, a preparation method thereof, and an application thereof. An active ester curing agent containing an imine bond, the chemical structural formula of which is shown in Formula I and Formula II. The preparation method of the curing agent is as follows: hydroxybenzaldehyde, 4-aminophenol or a diamine substance, and an organic solvent are mixed and reacted, an acid binding agent is added, the temperature is lowered to 5-10°C, an acyl chloride is added and the reaction is continued to obtain an active ester containing one or two imine bonds. By introducing an imine bond structure, the present invention gives epoxy resin the ability of secondary processing and solvent recovery, can solve the problems of epoxy resin waste polluting the environment and wasting resources, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and in particular to an active ester curing agent with an imine bond, a preparation method and an application thereof. Background Art

[0002] Conventional epoxy resin curing agents, such as amines and anhydrides, will inevitably produce secondary hydroxyl groups during the reaction with epoxy resin, making the overall polarity of the material higher, which will affect the dielectric properties and hygroscopicity of the epoxy resin.

[0003] Nowadays, thermosetting resins are widely used. When damaged or discarded, these resins cause environmental pollution and waste resources. In the field of electronic appliances, a large amount of epoxy resin is still discarded and difficult to recycle. By introducing reversible covalent bonds into the polymer network, such as imine bonds (CN108129638A) and disulfide bonds (CN108250412A), the polymer molecular network structure can be transformed by exchanging reversible bonds, giving thermosetting resins the ability to be recycled and reprocessed. However, there is currently no research combining active ester curing with reversible covalent bonds. Summary of the Invention

[0004] In order to overcome the above-mentioned defects and shortcomings in the prior art, the primary purpose of the present invention is to provide an active ester curing agent containing an imine bond.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned active ester curing agent containing an imine bond.

[0006] Another object of the present invention is to provide an application of the above-mentioned active ester curing agent containing an imine bond.

[0007] Another object of the present invention is to provide a resin composition containing the above-mentioned active ester curing agent with an imine bond.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] The present invention provides an active ester curing agent containing an imine bond and a method for preparing the same. After curing the epoxy resin, the imine bond in its structure imparts reprocessability, recyclability, and biodegradability. At high temperatures, the epoxy resin can be remolded by hot pressing; using solvents containing amines, the epoxy resin can be recovered and subsequently remolded; and the epoxy resin can also be degraded under acidic conditions.

[0010] An active ester curing agent containing an imine bond, the chemical structure of which is as follows:

[0011]

[0012] Wherein, R1 is methyl or phenyl, R2 is -C2H4, -C4H8, -C 10 H 20 、-C 12 H 24 One of , n is an integer from 1 to 5.

[0013] Preferably, the chemical structural formula of the curing agent is as follows:

[0014]

[0015]

[0016] Preferably, the chemical structural formula of the curing agent is as follows:

[0017]

[0018] A method for preparing an active ester curing agent containing an imine bond, wherein the method for preparing the curing agent represented by formula I is as follows:

[0019] The active ester curing agent containing an imine bond is obtained by mixing hydroxybenzaldehyde, 4-aminophenol and an organic solvent, adding an acid binding agent, cooling to 5-10°C, adding an acyl chloride and continuing the reaction, collecting the precipitate, washing and drying it;

[0020] The preparation method of the curing agent shown in Formula II is as follows:

[0021] Hydroxybenzaldehyde, diamine substances and organic solvents are mixed for reaction, an acid binding agent is added, the temperature is lowered to 5-10°C, acyl chloride is added to continue the reaction, and the precipitate is collected, washed and dried to obtain an active ester curing agent containing two imine bonds.

[0022] Preferably, the hydroxybenzaldehyde is one of 3-hydroxybenzaldehyde, p-hydroxybenzaldehyde, and 3,4-dihydroxybenzaldehyde;

[0023] The diamine substance is one of ethylenediamine, butylenediamine, p-phenylenediamine, m-phenylenediamine and o-phenylenediamine.

[0024] Preferably, the molar ratio of the hydroxybenzaldehyde substance to 4-aminophenol is 1:0.8-1.2, more preferably 1:0.95-1.05;

[0025] The molar ratio of the diamine substance to the hydroxybenzaldehyde substance is 1:2-10, more preferably 1:2.

[0026] Preferably, the reaction temperature is 25-50°C, the mixing reaction time is 0.1-10h, and the continued reaction time is 0.5-50h;

[0027] The acid binding agent is one of triethylamine, N,N-diisopropylethylamine, pyridine and potassium carbonate. The molar ratio of the acid binding agent to the acyl chloride is 1-10:1, more preferably 1-2:1.

[0028] Preferably, the organic solvent is one of tetrahydrofuran, dioxane, ether, acetone, butanone, and N,N-dimethylformamide, and the mass ratio of the organic solvent to the hydroxybenzaldehyde substance is 1 to 100:1;

[0029] The acyl chloride is acetyl chloride or benzoyl chloride.

[0030] More preferably, the chemical structural formula of the curing agent is as follows:

[0031]

[0032] The preparation method is as follows:

[0033] Dissolve 0.1-0.2 mol of 4-aminophenol and 0.1-0.2 mol of 3,4-dihydroxybenzaldehyde in 200-400 ml of tetrahydrofuran, react at 25°C for 1-3 hours, add 0.3-0.5 mol of triethylamine, cool to 5°C, add 0.3-0.5 mol of acetyl chloride dropwise, react for 2-4 hours, collect the precipitate, wash and dry to obtain the above-mentioned active ester curing agent.

[0034] Application of the active ester curing agent containing imine bonds in epoxy resin curing, recovery, reprocessing and solvent recovery.

[0035] A resin composition comprising the following components by weight:

[0036] Epoxy resin: 100 parts;

[0037] Active ester curing agent: 50-150 parts;

[0038] Catalyst: 0.5-1 part;

[0039] The epoxy resin is a DGEBA type epoxy resin:

[0040] The catalyst is 4-dimethylaminopyridine;

[0041] The active ester curing agent is the active ester curing agent according to any one of claims 1 to 3.

[0042] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0043] 1. The present invention introduces an imine bond structure to endow epoxy resin with the ability of secondary processing and solvent recovery, thereby solving the problems of epoxy resin waste polluting the environment and wasting resources.

[0044] 2. The present invention utilizes an active ester curing mechanism to prepare an epoxy resin having a lower dielectric constant and dielectric loss, and a lower water absorption rate, and can be applied to electronic and electrical materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the active ester curing agent containing an imine bond prepared in Example 1;

[0046] Figure 2 This is the carbon NMR spectrum of the active ester curing agent containing an imine bond prepared in Example 1;

[0047] Figure 3 This is the DSC curve of the active ester curing agent containing an imine bond prepared in Example 1 (melting point is marked);

[0048] Figure 4 The dielectric properties of epoxy resin used in this application example are shown in Figure 2 (dielectric constant: upper black curve, dielectric loss: lower red curve);

[0049] Figure 5 An example of epoxy resin reprocessing and solvent recovery, including original resin fragments (top left), resin after hot pressing (top right), resin dissolved in ethylenediamine in N,N-dimethylformamide (bottom left), and resin remolded using a solvent method (bottom right).

[0050] Figure 6 The tensile curves of the application example resin (original sample: black curve, hot pressing sample: red curve, solvent method re-molding sample: blue curve). DETAILED DESCRIPTION

[0051] The present invention will be described in further detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto. For process parameters not particularly noted, conventional techniques may be used.

[0052] In the following examples, H NMR 1 H-NMR and C-spectroscopy 13 C-NMR was measured using a Bruker instrument at 400 MHz, with deuterated chloroform (CDCl3) as the solvent. DSC (differential scanning calorimetry) curves were measured using a Mettler Toledo instrument. Dielectric properties were measured using an Agilent 4294a impedance analyzer at a frequency of 40 Hz to 10 MHz.

[0053] Application Example The tensile properties are tested by a domestic universal testing machine.

[0054] Example 1

[0055] Dissolve 10.9g (0.1mol) of 4-aminophenol and 13.8g (0.1mol) of 3,4-dihydroxybenzaldehyde in 200ml of tetrahydrofuran and allow to react at 25°C for 1h. This process involves the amino group reacting with the aldehyde group to form an imine bond. Add 31g (0.3mol) of triethylamine, cool to 5°C, and then dropwise add 23.6g (0.3mol) of acetyl chloride. Allow to react for 2h. This process involves the acyl chloride reacting with the phenolic hydroxyl group to form an ester group, or active ester. After the reaction is complete, pour the mixture into water and collect the precipitate. Wash twice and then dry to obtain an active ester containing an imine bond, the structural formula of which is shown in Formula I-1 below, with a yield of 50% and a melting point of 98°C. 1 H-NMR and 13 C-NMR Figure 1 、 Figure 2 As shown, the data is as follows.

[0056] 1 H NMR (400MHz, CDCl3) δ8.38 (s, 1H), 7.79 (d, J=2.0Hz, 1H), 7.74 (dd, J=8.3, 2.0Hz, 1 H), 7.30 (d, J=8.3Hz, 1H), 7.24-7.16 (m, 2H), 7.15-7.07 (m, 2H), 2.34-2.28 (m, 9H).

[0057] 13 C NMR (100MHz, CDCl3) δ169.58, 168.15, 167.94, 158.24, 149.13, 148.96, 144.51, 142.54 , 134.87, 127.35, 124.26, 123.80, 123.21, 122.25, 121.79, 77.26, 21.13, 20.68, 20.61.

[0058]

[0059] Example 2

[0060] Dissolve 10.9g (0.1mol) of 4-aminophenol and 12.2g (0.1mol) of 4-hydroxybenzaldehyde in 200ml of tetrahydrofuran and react at 25°C for 1h. Add 20.5g (0.2mol) of triethylamine, cool to 5°C, and then dropwise add 15.7g (0.2mol) of acetyl chloride and react for 2h. After the reaction is complete, pour the mixture into water and collect the precipitate. Wash twice and dry to obtain an active ester containing an imine bond, with the structural formula shown in Formula I-2 below, in a 50% yield.

[0061]

[0062] Example 3

[0063] Dissolve 10.9 g (0.1 mol) of 4-aminophenol and 12.2 g (0.1 mol) of 4-hydroxybenzaldehyde in 200 ml of tetrahydrofuran and react at 25°C for 1 hour. Add 20.5 g (0.2 mol) of triethylamine, cool to 5°C, and then dropwise add 28 g (0.2 mol) of benzoyl chloride. React for 2 hours. After the reaction is complete, pour the mixture into water and collect the precipitate.

[0064] After washing twice and drying, an active ester containing an imine bond is obtained, the structural formula of which is shown in Formula I-3 below, with a yield of 50%.

[0065]

[0066] Example 4

[0067] Dissolve 6g (0.1mol) of ethylenediamine and 24.4g (0.2mol) of 4-hydroxybenzaldehyde in 200ml of tetrahydrofuran and react at 25°C for 1h. Add 20.5g (0.2mol) of triethylamine, cool to 5°C, and then add 15.7g (0.2mol) of acetyl chloride dropwise for 2h. After the reaction is complete, pour the mixture into water and collect the precipitate. Wash twice and dry to obtain an active ester containing an imine bond, with the structural formula shown below in Formula II-1, in a 50% yield.

[0068]

[0069] Example 5

[0070] Dissolve 6g (0.1mol) of ethylenediamine and 24.4g (0.2mol) of 4-hydroxybenzaldehyde in 200ml of tetrahydrofuran and react at 25°C for 1h. Add 20.5g (0.2mol) of triethylamine, cool to 5°C, and then dropwise add 28g (0.2mol) of benzoyl chloride. React for 2h. After the reaction is complete, pour the mixture into water and collect the precipitate. Wash twice and dry to obtain an active ester containing an imine bond, with the structural formula shown in Formula II-2 below, in a 50% yield.

[0071]

[0072] Example 6

[0073] Dissolve 6g (0.1mol) of ethylenediamine and 27.6g (0.2mol) of 3,4-dihydroxybenzaldehyde in 200ml of tetrahydrofuran and react at 25°C for 1h. Add 41g (0.4mol) of triethylamine, cool to 5°C, and then dropwise add 31.5g (0.4mol) of acetyl chloride and react for 2h. After the reaction is complete, pour the mixture into water and collect the precipitate. Wash twice and dry to obtain an active ester containing an imine bond, with the structural formula shown in Formula II-3 below, and a yield of 50%.

[0074]

[0075] Example 7

[0076] Dissolve 10.8g (0.1mol) of o-phenylenediamine and 24.4g (0.2mol) of 4-hydroxybenzaldehyde in 200ml of tetrahydrofuran and react at 25°C for 1h. Add 20.5g (0.2mol) of triethylamine, cool to 5°C, and then dropwise add 28g (0.2mol) of benzoyl chloride and react for 2h. After the reaction is complete, pour the mixture into water and collect the precipitate. Wash twice and dry to obtain an active ester containing an imine bond, with the structural formula shown in Formula II-4 below, in a 50% yield.

[0077]

[0078] Application Examples

[0079] 2.1 g of the active ester containing an imine bond prepared in Example 1 and 3 g of commercially available bisphenol A glycidyl ether (DGEBA type epoxy resin) were heated and mixed uniformly, and then 0.5 wt% of bisphenol A glycidyl ether catalyst 4-dimethylaminopyridine was added and mixed uniformly. The mixture was cured at 130° C. for 4 h and at 150° C. for 2 h to obtain an epoxy cured product. Figure 4 As shown in FIG. 3 , the dielectric constant of the epoxy resin at a frequency of 10 MHz is 3.37, the dielectric loss is 0.013, and the 24-hour water absorption rate of the epoxy resin is 0.25 wt %. Figure 5 The upper left is the resin fragment before hot pressing. Figure 5 The upper right shows the resin after hot pressing. After the resin is cut into pieces, it can be re-molded by hot pressing at 150°C for 1 hour in a hot press. The presence of the imine bond in the active ester curing agent gives the resin the ability to be processed again.

[0080] In addition, the epoxy cured product can be dissolved in N, N-dimethylformamide containing 0.1 mol / L ethylenediamine. After removing the ethylenediamine and N, N-dimethylformamide in a 90°C oven, it can be molded again. Figure 5 After dissolving the resin fragment shown in the upper left corner, the following Figure 5 The lower left side shows a uniform solution, which is reshaped by solvent method. Figure 5Shown below right. Figure 6 The tensile strength of the resins formed by hot pressing and solvent remolding is compared to the original resin's tensile strength. The original resin has a tensile strength of 69 MPa. Hot pressing has minimal impact on tensile properties, achieving a tensile strength of 69 MPa, with only a slight decrease in elongation at break. Solvent remolding does affect the resin's tensile properties to a moderate 58 MPa, but still reaches 84% ​​of the original resin's tensile strength.

[0081] Comparative Example 1

[0082] Unlike the application example, the epoxy resin was cured by adding an anhydride curing agent, methyl nadic anhydride, at 110°C for 4 hours and then at 150°C for 2 hours. The epoxy resin exhibited a high 24-hour water absorption rate of 0.57 wt%, 2.4 times that of an active ester-cured resin. Furthermore, the epoxy resin could not be reshaped by hot pressing or dissolved in solvents, making it unrecyclable.

[0083] Comparative Example 2

[0084] Unlike the application example, the epoxy resin was cured by adding an amine curing agent, 4,4-diaminodiphenylmethane, at 110°C for 4 hours and then at 150°C for 2 hours. The 24-hour water absorption of this epoxy resin was 0.45 wt%, significantly higher than that of the active ester-cured resin. Similarly, this epoxy resin could not be reshaped by hot pressing or dissolved in solvents, making it unrecyclable.

[0085] Table 1

[0086] Application Examples Comparative Example 1 Comparative Example 2 24h water absorption 0.25wt% 0.57wt% 0.45wt%

[0087] The above is a detailed description of the present invention in combination with embodiments, but the implementation methods of the present invention are not limited to the above embodiments. Any other changes, replacements, combination simplifications, etc. made under the core guiding idea of ​​the patent of the present invention are included in the scope of protection of the patent of the present invention.

Claims

1. An active ester curing agent containing an imine bond, characterized in that The chemical structure is as follows: 。 2. A method for preparing the active ester curing agent containing an imine bond according to claim 1, characterized in that: The preparation method of the curing agent is as follows: Hydroxybenzaldehyde, 4-aminophenol and an organic solvent are mixed and reacted, an acid binding agent is added, the temperature is lowered to 5-10°C, and an acyl chloride is added to continue the reaction to obtain an active ester curing agent containing an imine bond.

3. The preparation method according to claim 2, characterized in that The hydroxybenzaldehyde is 3,4-dihydroxybenzaldehyde.

4. The preparation method according to claim 2, characterized in that The molar ratio of the hydroxybenzaldehyde to 4-aminophenol is 1:0.8-1.

2.

5. The preparation method according to claim 2, characterized in that The reaction temperature is 25-50°C, the mixing reaction time is 0.1-10h, and the continued reaction time is 0.5-50h; The acid binding agent is one of triethylamine, N,N-diisopropylethylamine, pyridine and potassium carbonate, and the molar ratio of the acid binding agent to the acyl chloride is 1-10:

1.

6. The preparation method according to claim 2, characterized in that The organic solvent is one of tetrahydrofuran, dioxane, ether, acetone, butanone, and N,N-dimethylformamide, and the mass ratio of the organic solvent to the hydroxybenzaldehyde substance is 1 to 100:1; The acyl chloride is acetyl chloride.

7. Use of the active ester curing agent containing an imine bond according to claim 1 in epoxy resin curing, recovery, reprocessing and solvent recovery.

8. A resin composition, characterized in that By weight, it includes the following components: Epoxy resin: 100 parts; Active ester curing agent: 50~150 parts; Catalyst: 0.5~1 part; The epoxy resin is a DGEBA type epoxy resin: The catalyst is 4-dimethylaminopyridine; Wherein, the active ester curing agent is the active ester curing agent according to claim 1.

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