Low-viscosity trifunctional epoxy resin, preparation method and epoxy resin curing system

Abstract

The invention relates to the technical field of high-performance resin, in particular to low-viscosity three-functional-group epoxy resin, a preparation method and an epoxy resin curing system, the low-viscosity three-functional-group epoxy resin has a structure as shown in a formula 1, and the formula 1 is imgabs0 #, in the formula 1, R1 is methyl, and R2 is H or methyl. By optimizing the structural design of the product and combining the parameter condition control of the preparation process, the purity and the yield of the epoxy resin product are ensured, so that the epoxy resin product has obviously low viscosity and a wide processing window, and the application requirements are better met.

Description

Technical Field

[0001] The present invention relates to the technical field of high-performance resins, and specifically to a low-viscosity trifunctional epoxy resin, a preparation method, and an epoxy resin curing system. Background Art

[0002] With the rapid development of high-tech industries such as aerospace and electronic appliances, the demand for special epoxy resin materials shows a significant growth trend. Especially when manufacturing large components, epoxy resins are required to have low viscosity and a wide processing window to meet the requirements of the molding process. The chemical structure differences between epoxy resins and curing agents will directly affect the viscosity and processing window of their resin systems. Moreover, they also affect the mechanical properties, thermal properties, and chemical stability of their cured products. Triglycidyl aminophenol epoxy resin, as a high-performance epoxy resin for liquid molding, has advantages such as good wettability and high strength of its cured product, and is widely used in fields such as electronic adhesives and aerospace composite materials. N,N,O-triglycidyl-p-aminophenol (p-TGAP) has a relatively high viscosity, high reactivity, and a narrow processing window, which is not conducive to processing and limits its application. For example, Chinese Patent (authorized publication number CN101139327B) discloses a preparation method of aminophenol triglycidyl compound, with a yield of 95 - 98%, an epoxy value of 0.85 - 1.00, and a viscosity of about 2500 mPa·s. It has a relatively high viscosity and a narrow processing window, and cannot meet some special processing requirements. Summary of the Invention

[0003] To solve the above problems, in the first aspect of the present invention, a low-viscosity trifunctional epoxy resin is provided. By optimizing the product structure design and combining the control of preparation process parameters, the purity and yield of the epoxy resin product are ensured, and the epoxy resin product has significantly lower viscosity and a wide processing window, better meeting the application requirements.

[0004] On the one hand, the present invention provides a low-viscosity trifunctional epoxy resin having the structure shown in Formula 1,

[0005] Formula 1: wherein R1 is methyl, and R2 is H or methyl.

[0006] In one embodiment, the low-viscosity trifunctional epoxy resin at least comprises the following raw materials: methyl-substituted p-aminophenol, epichlorohydrin, a catalyst, and an aqueous alkali solution; the methyl-substituted p-aminophenol is 2,5-dimethyl-p-aminophenol or 2-methyl-p-aminophenol.

[0007] In one embodiment, the molar ratio of the methyl-substituted p-aminophenol, epichlorohydrin, and the catalyst is 1.00:(6.00 - 12.00):(0.04 - 0.10).

[0008] In one embodiment, the molar ratio of the methyl-substituted p-aminophenol, epichlorohydrin, and the catalyst is 1.00:(9.00 - 11.00):0.05.

[0009] In one embodiment, the catalyst is at least one of tetrabutylammonium bromide (TBAB), tetraethylammonium bromide, triethylbenzylammonium chloride (TEBAC), triethylbenzylammonium bromide, or trimethylbenzylammonium bromide.

[0010] In one embodiment, the aqueous alkali solution is a 20 - 40 wt% aqueous sodium hydroxide solution.

[0011] In one embodiment, the concentration of the aqueous sodium hydroxide solution can be 20 wt%, 25 wt%, 30 wt%, 35 wt%, or 40 wt%.

[0012] In one embodiment, the molar ratio of sodium hydroxide to the catalyst in the aqueous sodium hydroxide solution is (3.00 - 3.30):(0.04 - 0.10).

[0013] In one embodiment, the molar ratio of sodium hydroxide to the catalyst in the aqueous sodium hydroxide solution is (3.10 - 3.20):0.05.

[0014] In one embodiment, the low-viscosity trifunctional epoxy resin has the structure shown in Formula 2,

[0015] Formula 2: is N,N,O-triglycidyl-2,5-dimethyl-p-aminophenol (p-TGMAP-25M).

[0016] Through the design of the molecular structure of the epoxy resin, the present invention synthesizes Formula 1: N,N,O-triglycidyl-2-methyl-p-aminophenol (p-TGMAP-2M) and N,N,O-triglycidyl-2,5-dimethyl-p-aminophenol (p-TGMAP-25M), which have excellent processing properties, low viscosity, good storage stability, and their cured products exhibit excellent mechanical strength and thermal properties. They are suitable for liquid molding advanced composite materials and have broad application prospects in high-end manufacturing fields such as aerospace.

[0017] On the other hand, the present invention provides a method for preparing a low-viscosity trifunctional epoxy resin, which at least includes the following steps:

[0018] (1) Using methyl-substituted p-aminophenol and epichlorohydrin as raw materials, in the presence of a catalyst, controlling the temperature at 90 - 110 °C to carry out a ring-opening addition reaction for 6 - 12 h;

[0019] (2) After the ring-opening addition reaction is completed, an aqueous alkali solution is added, and a ring-closing reaction is carried out at 30-50 °C for 6-12 h. After post-treatment, a crude product is obtained, and the crude product is purified to obtain a low-viscosity trifunctional epoxy resin.

[0020] In one embodiment, the post-treatment includes the following steps: After the ring-closing reaction is completed, it is allowed to stand, and the upper organic phase product is obtained by liquid separation. The organic phase product is washed, filtered by suction, and rotary evaporated to obtain a crude product.

[0021] In one embodiment, the methyl-substituted p-aminophenol is 2,5-dimethyl-p-aminophenol, the temperature of the ring-opening addition reaction is 80 °C, and the time is 9 h; the temperature of the ring-closing reaction is 40 °C, and the time is 8-12 h.

[0022] In one embodiment, the methyl-substituted p-aminophenol is 2-methyl-p-aminophenol, the temperature of the ring-opening addition reaction is 80 °C, and the time is 9 h; the temperature of the ring-closing reaction is 40 °C, and the time is 6-10 h.

[0023] In one embodiment, the preparation method of the low-viscosity trifunctional epoxy resin includes at least the following steps: Using 2,5-dimethyl-p-aminophenol and epichlorohydrin as raw materials, in the presence of tetrabutylammonium bromide, controlling the temperature at 80 °C to carry out a ring-opening addition reaction for 9 h; adding a 20 wt% sodium hydroxide aqueous solution and carrying out a ring-closing reaction at 40 °C for 8-12 h; after the ring-closing reaction is completed, it is allowed to stand, and the upper organic phase product is obtained by liquid separation. The organic phase product is washed, filtered by suction, and rotary evaporated to obtain a crude product, and N,N,O-triglycidyl-2,5-dimethyl-p-aminophenol (p-TGMAP-25M) is obtained by purification.

[0024] In one embodiment, the molar ratio of 2,5-dimethyl-p-aminophenol, epichlorohydrin, tetrabutylammonium bromide, and sodium hydroxide is 1.00:10.00:0.05:3.20.

[0025] In one embodiment, the preparation method of the low-viscosity trifunctional epoxy resin includes at least the following steps: Using 2-methyl-p-aminophenol and epichlorohydrin as raw materials, in the presence of tetrabutylammonium bromide, controlling the temperature at 80 °C to carry out a ring-opening addition reaction for 8 h; adding a 20 wt% sodium hydroxide aqueous solution and carrying out a ring-closing reaction at 40 °C for 6-10 h; after the ring-closing reaction is completed, it is allowed to stand, and the upper organic phase product is obtained by liquid separation. The organic phase product is washed, filtered by suction, and rotary evaporated to obtain a crude product, and N,N,O-triglycidyl-2-methyl-p-aminophenol (p-TGMAP-2M) is obtained by purification.

[0026] In one embodiment, the molar ratio of 2-methyl-p-aminophenol, epichlorohydrin, tetrabutylammonium bromide, and sodium hydroxide is 1.00:10.00:0.05:3.20.

[0027] Furthermore, the present invention uses 2,5-dimethyl-p-aminophenol or 2-methyl-p-aminophenol and epichlorohydrin as raw materials. In the presence of a catalyst, through optimizing the preparation process, a crude product of low-viscosity trifunctional epoxy resin with a certain yield is prepared. Further, through purification by a chromatography column, a low-viscosity (<500 mPa·s) trifunctional epoxy resin with a purity of nearly 100.0% is obtained, which is suitable for liquid processing and molding. In particular, by separately controlling the ring-opening addition reaction conditions and the ring-closure reaction conditions of p-TGMAP-2M and p-TGMAP-25M, the yield of the crude product of low-viscosity trifunctional epoxy resin and the content of N,N,O-triglycidyl-2-methyl-p-aminophenol or N,N,O-triglycidyl-2,5-dimethyl-p-aminophenol in the crude product are ensured, facilitating subsequent purification and application.

[0028] The present invention controls the raw materials of 2,5-dimethyl-p-aminophenol and epichlorohydrin. In the presence of tetrabutylammonium bromide, the temperature is controlled at 80 °C for a ring-opening addition reaction for 9 h; then 20 wt% aqueous sodium hydroxide solution is added for a ring-closure reaction at 40 °C for 8 - 12 h, and the yield of the obtained crude product is 97.7 - 98.7%, and the purity is 75.0 - 80.8%.

[0029] The present invention controls the raw materials of 2-methyl-p-aminophenol and epichlorohydrin. In the presence of tetrabutylammonium bromide, the temperature is controlled at 80 °C for a ring-opening addition reaction for 8 h; 20 wt% aqueous sodium hydroxide solution is added for a ring-closure reaction at 40 °C for 6 - 10 h, and the yield of the obtained crude product is 95.0 - 95.8%, and the purity is 75.0 - 75.8%.

[0030] In one embodiment, the purification method includes at least purification by a chromatography column.

[0031] In one embodiment, the steps of purification by a chromatography column include: wet-packing the chromatography column with petroleum ether and silica gel powder; transferring the crude product into the chromatography column, waiting for it to flow to the silica gel layer, and adding anhydrous sodium sulfate as a buffer layer; continuously adding an eluent from the upper end of the chromatography column, and collecting the epoxy resin solution according to the results of thin-layer chromatography on a silica gel plate, and distilling off the solvent to obtain a low-viscosity trifunctional epoxy resin.

[0032] In one embodiment, the particle size of the silica gel powder can be 300 - 500 mesh.

[0033] In one embodiment, the particle size of the silica powder can be 300 mesh, 400 mesh, or 500 mesh.

[0034] In one embodiment, the thickness of the silica gel layer can be 15 - 25 cm.

[0035] In one embodiment, the thickness of the silica gel layer can be 15 cm, 18 cm, 20 cm, 22 cm, or 25 cm.

[0036] In one embodiment, the thickness of the buffer layer can be 2 - 4 cm.

[0037] In one embodiment, the thickness of the buffer layer can be 2 cm, 3 cm, or 4 cm.

[0038] In one embodiment, the developing agent is a combination of ethyl acetate and petroleum ether, and the volume ratio of ethyl acetate to petroleum ether is 1.0:(4.0 - 6.0).

[0039] In one embodiment, the volume ratio of ethyl acetate to petroleum ether can be 1.0:4.0, 1.0:5.0, or 1.0:6.0.

[0040] In one embodiment, the temperature of the distillation is 55 - 70 °C.

[0041] In one embodiment, the temperature of the distillation can be 55 °C, 60 °C, 65 °C, or 70 °C.

[0042] The third aspect of the present invention provides an epoxy resin curing system containing a low-viscosity trifunctional epoxy resin. The raw materials for preparation at least include: a low-viscosity trifunctional epoxy resin, a curing agent, and a solvent. The molar ratio of epoxy groups in the low-viscosity trifunctional epoxy resin to active hydrogens in the curing agent is (0.8 - 1.1):1.0.

[0043] In one embodiment, the molar ratio of epoxy groups in the low-viscosity trifunctional epoxy resin to active hydrogens in the curing agent is (0.9 - 1.0):1.0.

[0044] In one embodiment, the curing agent is selected from one or more of 4,4'-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA), 4,4'-methylenedianiline (DDM), 4,4'-methylenebis(2-ethylaniline) (MOEA), 4,4'-methylenebis(2-chloroaniline) (MOCA), or 4,4'-methylenebis(3-chloro-2,6-diethylaniline) (MOEA).

[0045] In one embodiment, the curing agent is 4,4'-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA).

[0046] In one embodiment, the solvent is tetrahydrofuran (THF).

[0047] In one embodiment, the method for preparing the epoxy resin curing system includes the following steps: dissolving a low-viscosity trifunctional epoxy resin and a curing agent in a solvent, ultrasonically mixing, removing the solvent and then adding it into a mold, placing it in a vacuum oven, evacuating to remove the air and residual solvent in the resin, curing under normal pressure, and naturally cooling to obtain the epoxy resin curing system.

[0048] In one embodiment, the time for ultrasonic mixing is 20 - 40 min.

[0049] In one embodiment, the time for ultrasonic mixing can be 20 min, 30 min, or 40 min.

[0050] In one embodiment, the temperature of the vacuum oven is set to 110 - 130 °C.

[0051] In one embodiment, the temperature for curing under normal pressure is 160 - 180 °C, and the time is 4 - 6 h.

[0052] In one embodiment, the temperature for curing under normal pressure can be 160 °C, 170 °C, or 180 °C.

[0053] In one embodiment, the time for curing under normal pressure can be 4 h, 5 h, or 6 h.

[0054] For the epoxy resin curing system provided by the present invention, by controlling the molar ratio of epoxy groups in the low-viscosity trifunctional epoxy resin to active hydrogens in the curing agent to be (0.8 - 1.1):1.0, the cured resin product has a flexural strength > 140 MPa, a flexural modulus > 3.50 GPa, a tensile strength > 60 MPa, a tensile modulus > 3.52 GPa, and a Tg > 140 °C.

[0055] Beneficial Effects

[0056] 1. The present invention provides a low-viscosity trifunctional epoxy resin, a preparation method, and an epoxy resin curing system. By optimizing the product structure design and combining the control of preparation process parameters, the purity and yield of the epoxy resin product are ensured, and the epoxy resin product has a significantly low viscosity and a wide processing window, better meeting the application requirements.

[0057] 2. By designing the molecular structure of epoxy resin, the present invention synthesizes Formula 1: N,N,O-triglycidyl-2-methyl-p-aminophenol (p-TGMAP-2M) and N,N,O-triglycidyl-2,5-dimethyl-p-aminophenol (p-TGMAP-25M), which have excellent processing properties, low viscosity, stable storage, and their cured products exhibit excellent mechanical strength and thermal properties. They are suitable for liquid molding advanced composites and have broad application prospects in high-end manufacturing fields such as aerospace.

[0058] 3. The present invention uses 2,5-dimethyl-p-aminophenol or 2-methyl-p-aminophenol and epichlorohydrin as raw materials, and under the condition of the presence of a catalyst, prepares a crude product of low-viscosity trifunctional epoxy resin with a certain yield through optimizing the preparation process, and further purifies it through a chromatography column to obtain a low-viscosity (<500 mPa·s) trifunctional epoxy resin with a purity of nearly 100.0%, which is suitable for liquid processing and molding.

[0059] 4. By respectively controlling the ring-opening addition reaction conditions and the ring-closure reaction conditions of p-TGMAP-2M and p-TGMAP-25M, the present invention ensures the yield of the crude product of low-viscosity trifunctional epoxy resin and the content of N,N,O-triglycidyl-2-methyl-p-aminophenol or N,N,O-triglycidyl-2,5-dimethyl-p-aminophenol in the crude product, which is convenient for subsequent purification and application.

[0060] 5. For the epoxy resin curing system provided by the present invention, by controlling the molar ratio of epoxy groups in the low-viscosity trifunctional epoxy resin to the active hydrogen in the curing agent to be (0.8 - 1.1):1.0, the cured resin product has a flexural strength > 140 MPa, a flexural modulus > 3.50 GPa, a tensile strength > 60 MPa, a tensile modulus > 3.52 GPa, and a Tg > 140 °C. Description of the Drawings

[0061] Figure 1 It is a rheological curve diagram of the epoxy resin curing system in Application Example 1.

[0062] Figure 2 It is a rheological curve diagram of the epoxy resin curing system in Application Example 2. Detailed Description of the Invention

[0063] Example 1

[0064] One aspect of Example 1 of the present invention provides a low-viscosity trifunctional epoxy resin with the structure shown in Formula 2,

[0065] Formula 2: It is N,N,O-triglycidyl-2,5-dimethyl-p-aminophenol (p-TGMAP-25M).

[0066] On the other hand, Example 1 of the present invention provides a method for preparing a low-viscosity trifunctional epoxy resin, comprising the following steps: adding 2,5-dimethyl-p-aminophenol, epichlorohydrin, and tetrabutylammonium bromide into a reaction vessel in sequence, passing N2 and stirring, and maintaining at 80 °C for 30 min to fully dissolve 2,5-dimethyl-p-aminophenol in epichlorohydrin, and controlling the temperature at 80 °C to carry out ring-opening addition reaction for 9 h; after the ring-opening addition reaction is completed, adding 20 wt% aqueous sodium hydroxide solution, passing N2 and stirring, and carrying out ring-closure reaction at 40 °C for 8 h; after the ring-closure reaction is completed, standing and separating to obtain the upper-layer organic phase product; washing the organic phase product 4 times with water and petroleum ether respectively, adding anhydrous sodium sulfate for water removal, filtering by suction, and rotary evaporating at 70 °C to obtain a crude product, and purifying to obtain N,N,O-triglycidyl-2,5-dimethyl-p-aminophenol (p-TGMAP-25M).

[0067] The molar ratio of the 2,5-dimethyl-p-aminophenol, epichlorohydrin, tetrabutylammonium bromide, and sodium hydroxide is 1.00:10.00:0.05:3.20.

[0068] The purification method is column chromatography purification, and the steps of the column chromatography purification include: wet-packing the column with petroleum ether and 300-mesh silica gel powder, and controlling the thickness of the silica gel layer to be 20 cm; moving the crude product into the column, waiting for it to flow to the silica gel layer, adding anhydrous sodium sulfate as a buffer layer, and the thickness of the buffer layer is 4 cm; preparing the developing agent according to the volume ratio of ethyl acetate:petroleum ether of 1.0:5.0; continuously adding the developing agent from the upper end of the column, and collecting the epoxy resin solution according to the results of thin-layer chromatography on a silica gel plate, and distilling at 60 °C to obtain N,N,O-triglycidyl-2,5-dimethyl-p-aminophenol (p-TGMAP-25M) with a purity of nearly 100.0%. Structure analysis: 1 H-NMR(CDCl3, TMS), δ(ppm): 6.61 - 7.00(s, Ar-H), 3.87 - 4.23(m, Ar-O-CH2-), 3.30 - 3.40(s, ), 3.07 - 3.24(m, Ar-N-CH2-), 2.95 - 3.07(s, ), 2.38 - 2.92(m, ), 2.10 - 2.37(s, Ar-CH3). The viscosity of p-TGMAP-25M is measured (at 25 °C, using a DV2TLV viscometer from Brookfield Company, USA, with a rotation speed of 95 r / min, the front end of the rotor is straight, 25 cm long and 12 cm wide) to be 315 mPa·s, and the epoxy equivalent is 116 g / eq.

[0069] Example 2

[0070] Example 2 of the present invention provides a low-viscosity trifunctional epoxy resin and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that the closed-loop reaction time is extended from 8 h to 10 h.

[0071] Example 3

[0072] Example 3 of the present invention provides a low-viscosity trifunctional epoxy resin and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that the closed-loop reaction time is extended from 8 h to 12 h.

[0073] Example 4

[0074] Example 4 of the present invention provides a low-viscosity trifunctional epoxy resin and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that the ring-opening addition reaction time is shortened from 9 h to 6 h.

[0075] Example 5

[0076] Example 5 of the present invention provides a low-viscosity trifunctional epoxy resin and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that the ring-opening addition reaction time is extended from 9 h to 12 h.

[0077] Example 6

[0078] On the one hand, Example 6 of the present invention provides a low-viscosity trifunctional epoxy resin having the structure shown in Formula 3,

[0079] Formula 3: is N,N,O-triglycidyl-2-methyl-p-aminophenol (p-TGMAP-2M).

[0080] On the other hand, Example 6 of the present invention provides a preparation method of a low-viscosity trifunctional epoxy resin, comprising the following steps: adding 2-methyl-p-aminophenol, epichlorohydrin, and tetrabutylammonium bromide into a reaction vessel in sequence, passing N2 and stirring, and maintaining at 80 °C for 30 min to fully dissolve 2-methyl-p-aminophenol in epichlorohydrin, controlling the temperature at 80 °C for a ring-opening addition reaction for 8 h; after the ring-opening addition reaction is completed, adding a 20 wt% aqueous sodium hydroxide solution, passing N2 and stirring, and carrying out a closed-loop reaction at 40 °C for 8 h; after the closed-loop reaction is completed, standing and separating to obtain an upper-layer organic phase product; washing the organic phase product 4 times with water and petroleum ether respectively, adding anhydrous sodium sulfate for water removal, filtering by suction, and rotary evaporating at 70 °C to obtain a crude product, and purifying to obtain N,N,O-triglycidyl-2-methyl-p-aminophenol (p-TGMAP-2M).

[0081] The molar ratio of the 2-methyl-p-aminophenol, epichlorohydrin, tetrabutylammonium bromide, and sodium hydroxide is 1.00:10.00:0.05:3.20.

[0082] The purification method is column chromatography purification. The steps of column chromatography purification include: wet-packing the chromatography column with petroleum ether and 300-mesh silica gel powder, controlling the thickness of the silica gel layer to be 20 cm; transferring the crude product into the chromatography column, waiting for it to flow to the silica gel layer, adding anhydrous sodium sulfate as a buffer layer, with the buffer layer thickness being 4 cm; preparing the developing agent according to the volume ratio of ethyl acetate: petroleum ether of 1.0:5.0; continuously adding the developing agent from the upper end of the chromatography column, collecting the epoxy resin solution according to the results of thin-layer chromatography on a silica gel plate, and distilling at 60 °C to obtain N,N,O-triglycidyl-2-methyl-p-aminophenol (p-TGMAP-2M) with a purity of 99.2%. Structure analysis: 1 H-NMR(CDCl3, TMS), δ(ppm): 6.57 - 6.80(s, Ar-H), 3.85 - 4.20(m, Ar-O-CH2-), 3.39 - 3.75(m, Ar-N-CH2-), 3.27 - 3.39(s, ), 3.07 - 3.20(s, ), 2.51 - 2.93(m, ), 2.18 - 2.28(s, Ar-CH3). The viscosity of p-TGMAP-2M was measured (at 25 °C, using a DV2TLV viscometer from Brookfield, USA, with a rotation speed of 32 r / min, the front end of the rotor being straight, 25 cm long and 12 cm wide) to be 477.5 mPa·s, and the epoxy equivalent was 102 g / eq.

[0083] Example 7

[0084] Example 7 of the present invention provides a low-viscosity trifunctional epoxy resin and its preparation method. The specific implementation manner is the same as that of Example 6, except that the closed-loop reaction time is reduced from 8 h to 6 h.

[0085] Example 8

[0086] Example 8 of the present invention provides a low-viscosity trifunctional epoxy resin and its preparation method. The specific implementation manner is the same as that of Example 6, except that the closed-loop reaction time is extended from 8 h to 10 h.

[0087] Example 9

[0088] Example 9 of the present invention provides a low-viscosity trifunctional epoxy resin and a preparation method thereof. The specific implementation manner is the same as that of Example 6, except that the ring-opening addition reaction time is extended from 8 h to 10 h.

[0089] Example 10

[0090] Example 10 of the present invention provides a low-viscosity trifunctional epoxy resin and a preparation method thereof. The specific implementation manner is the same as that of Example 6, except that the ring-opening addition reaction time is extended from 8 h to 12 h.

[0091] Comparative Example 1

[0092] Comparative Example 1 of the present invention provides an N,N,O-triglycidyl-3-methyl-p-aminophenol (p-TGMAP-3M) having the structure shown in Formula 4,

[0093] Formula 4:

[0094] The preparation method of the p-TGMAP-3M includes the following steps: 3-methyl-p-aminophenol, epichlorohydrin, and tetrabutylammonium bromide are successively added to a reaction vessel, N2 is introduced and stirred, and the mixture is maintained at 80 °C for 30 min to fully dissolve 3-methyl-p-aminophenol in epichlorohydrin. The ring-opening addition reaction is carried out at 80 °C for 8 h; after the ring-opening addition reaction is completed, a 20 wt% aqueous sodium hydroxide solution is added, N2 is introduced and stirred, and the ring-closing reaction is carried out at 40 °C for 8 h; after the ring-closing reaction is completed, the mixture is allowed to stand, and the upper organic phase product is separated by liquid separation; the organic phase product is washed 4 times with water and petroleum ether respectively, anhydrous sodium sulfate is added to remove water, suction filtration is carried out, and the crude product is obtained by rotary evaporation at 70 °C and purified to obtain p-TGMAP-3M.

[0095] The molar ratio of the 3-methyl-p-aminophenol, epichlorohydrin, tetrabutylammonium bromide, and sodium hydroxide is 1.00:10.00:0.05:3.20.

[0096] The purification method is column chromatography purification. The steps of column chromatography purification include: wet-packing the column with petroleum ether and 300-mesh silica gel powder, and controlling the thickness of the silica gel layer to be 20 cm; transferring the crude product into the column, waiting for it to flow to the silica gel layer, adding anhydrous sodium sulfate as a buffer layer, and the thickness of the buffer layer is 4 cm; preparing the eluent according to the volume ratio of ethyl acetate:petroleum ether of 1.0:5.0; continuously adding the eluent from the upper end of the column, and collecting the epoxy resin solution according to the results of thin-layer chromatography on a silica gel plate, and distilling at 60 °C to obtain p-TGMAP-3M with a purity of 99.2%. Structure analysis: 11H-NMR (CDCl3, TMS), δ (ppm): 6.65 - 7.20 (s, Ar-H), 3.80 - 4.25 (m, Ar-O-CH2-), 3.25 - 3.40 (s, ), 3.05 - 3.25 (m, Ar-N-CH2-), 2.95 - 3.05 (s, ), 2.38 - 2.92 (m, ), 2.25 - 2.38 (s, Ar-CH3). The viscosity of p-TGMAP-3M was measured (at 25 °C, using a DV2TLV viscometer from Brookfield, USA, with a rotation speed of 30 r / min, the front end of the rotor was straight, 25 cm long and 12 cm wide) to be 491.0 mPa·s, and the epoxy equivalent was 101 g / eq.

[0097] Comparative Example 2

[0098] Comparative Example 2 of the present invention provides an N,N,O-triglycidyl-p-aminophenol (AFG-90H), which is a product of Shanghai Huayi Resin Co., Ltd., with a purity of 98.5%, an epoxy equivalent of 95 - 105 g / eq, and a viscosity (at 25 °C, using a DV2TLV viscometer from Brookfield, USA, with a rotation speed of 23 r / min, the front end of the rotor was straight, 25 cm long and 12 cm wide) of 650 mPa·s. Its structure is as shown in Formula 5:

[0099] Formula 5:

[0100] Comparative Example 3

[0101] Comparative Example 3 of the present invention provides an N,N,O-triglycidyl-m-aminophenol (AFG-90MH), which is a product of Shanghai Huayi Resin Co., Ltd., with a purity of 96.4%, an epoxy equivalent of 95 - 105 g / eq, and a viscosity (at 25 °C, using a DV2TLV viscometer from Brookfield, USA, with a rotation speed of 6 r / min, the front end of the rotor was straight, 25 cm long and 12 cm wide) of 2550 mPa·s. Its structure is as shown in Formula 6:

[0102] Formula 6:

[0103] Comparative Example 4

[0104] Comparative Example 4 of the present invention provides a diglycidyl 4,5-epoxytetrahydrophthalate (TDE-85), which is a product of Shanghai Huayi Resin Co., Ltd. After purification, its purity is 89.9%, epoxy equivalent is 100 - 117 g / eq, viscosity (at 25°C, using a DV2TLV viscometer of Brookfield Company, USA, rotation speed 20 r / min, the front end of the rotor is straight, 25 cm long and 12 cm wide) is 750 mPa·s, and its structure is as shown in Formula 7:

[0105] Formula 7:

[0106] Application Example 1

[0107] Application Example 1 of the present invention provides an epoxy resin curing system containing p-TGMAP-25M. The preparation method includes the following steps: Add 62.51 g of 4,4'-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA) to 100 mL of tetrahydrofuran, pour it into a container containing 77.49 g of p-TGMAP-25M (Example 1), ultrasonically mix for 30 min, and after removing tetrahydrofuran, obtain an epoxy resin curing system containing p-TGMAP-25M, whose processing window is 25°C - 218°C.

[0108] Add the obtained epoxy resin curing system containing p-TGMAP-25M into a mold, place it in a vacuum oven at 120°C, evacuate to remove the air and residual solvent in the resin, cure at 160°C for 2 h, raise the temperature to 180°C and cure for 2 h, and then naturally cool to obtain a resin casting. At room temperature (25°C), the critical stress intensity factor (K IC ) of the casting is 1.55 MPa / m 1 / 2 , the flexural strength is 148 MPa, the flexural modulus is 3.55 GPa, the tensile strength is 68 MPa, and the tensile modulus is 3.52 GPa. The measured Tg is 142°C, and T d5 is 318°C.

[0109] Application Example 2

[0110] Application Example 2 of the present invention provides an epoxy resin curing system containing p-TGMAP-2M. The preparation method includes the following steps: Add 69.10 g of 4,4'-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA) to 100 mL of tetrahydrofuran, pour it into a container containing 70.89 g of p-TGMAP-2M (Example 6), ultrasonically mix for 30 min, and after removing tetrahydrofuran, obtain an epoxy resin curing system containing p-TGMAP-2M, whose processing window is 25°C - 203°C.

[0111] The obtained epoxy resin curing system containing p-TGMAP-2M was added into a mold and placed in a vacuum oven at 120 °C. Vacuum was applied to remove the air and residual solvent in the resin. It was cured at 160 °C for 2 h, then the temperature was raised to 180 °C and cured for 2 h, and then naturally cooled to obtain a resin casting. At room temperature (25 °C), the critical stress intensity factor (K IC ) of the casting was 1.32 MPa / m 1 / 2 , the flexural strength was 143 MPa, the flexural modulus was 3.66 GPa, the tensile strength was 63 MPa, and the tensile modulus was 3.53 GPa. The measured Tg was 155 °C, and T d5 was 309 °C.

[0112] Application Comparative Example 1

[0113] Application Comparative Example 1 of the present invention provides an epoxy resin curing system containing p-TGMAP-3M. The preparation method includes the following steps: 69.10 g of 4,4'-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA) was added to 100 mL of tetrahydrofuran, and then poured into a container containing 70.89 g of p-TGMAP-3M (Comparative Example 1). Ultrasonic mixing was carried out for 30 min. After removing tetrahydrofuran, an epoxy resin curing system containing p-TGMAP-3M was obtained, and its processing window was 25 °C - 211 °C.

[0114] The obtained epoxy resin curing system containing p-TGMAP-3M was added into a mold and placed in a vacuum oven at 120 °C. Vacuum was applied to remove the air and residual solvent in the resin. It was cured at 160 °C for 2 h, then the temperature was raised to 180 °C and cured for 2 h, and then naturally cooled to obtain a resin casting. At room temperature (25 °C), the critical stress intensity factor (K IC ) of the casting was 1.42 MPa / m 1 / 2 , the flexural strength was 135 MPa, the flexural modulus was 3.22 GPa, the tensile strength was 63 MPa, and the tensile modulus was 3.55 GPa. The measured Tg was 171 °C, and T d5 was 347 °C.

[0115] Application Comparative Example 2

[0116] Application Comparative Example 2 of the present invention provides an epoxy resin curing system containing AFG-90H. The preparation method includes the following steps: 70.79 g of 4,4'-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA) was added to 100 mL of tetrahydrofuran, and then poured into a container containing 69.21 g of AFG-90H (Comparative Example 2). Ultrasonic mixing was carried out for 30 min. After removing tetrahydrofuran, an epoxy resin curing system containing AFG-90H was obtained, and its processing window was 25 °C - 160 °C.

[0117] The obtained epoxy resin curing system containing AFG-90H was added into a mold and placed in a vacuum oven at 120 °C. Vacuum was applied to remove the air and residual solvents in the resin, cured at 160 °C for 2 h, heated to 180 °C and cured for 2 h, and then naturally cooled to obtain a resin casting. At room temperature (25 °C), the critical stress intensity factor (K IC ) of the casting was 2.22 MPa / m 1 / 2 , the flexural strength was 120 MPa, the flexural modulus was 2.44 GPa, the tensile strength was 76 MPa, and the tensile modulus was 3.55 GPa. The measured Tg was 198 °C, and T d5 was 357 °C.

[0118] Application Comparative Example 3

[0119] Application Comparative Example 3 of the present invention provides an epoxy resin curing system containing AFG-90MH. The preparation method includes the following steps: Add 70.79 g of 4,4'-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA) into 100 mL of tetrahydrofuran, pour it into a container containing 69.21 g of AFG-90MH (Comparative Example 3), ultrasonically mix for 30 min, and after removing tetrahydrofuran, an epoxy resin curing system containing AFG-90MH is obtained, and its processing window is 25 °C - 164 °C.

[0120] The obtained epoxy resin curing system containing AFG-90MH was added into a mold and placed in a vacuum oven at 120 °C. Vacuum was applied to remove the air and residual solvents in the resin, cured at 160 °C for 2 h, heated to 180 °C and cured for 2 h, and then naturally cooled to obtain a resin casting. At room temperature (25 °C), the critical stress intensity factor (K IC ) of the casting was 1.78 MPa / m 1 / 2 , the flexural strength was 148 MPa, the flexural modulus was 2.85 GPa, the tensile strength was 96 MPa, and the tensile modulus was 3.52 GPa. The measured Tg was 183 °C, and T d5 was 347 °C.

[0121] Application Comparative Example 4

[0122] Application Comparative Example 4 of the present invention provides an epoxy resin curing system containing TDE-85. The preparation method includes the following steps: Add 71.76 g of 4,4'-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA) into 100 mL of tetrahydrofuran, pour it into a container containing 68.23 g of TDE-85 (Comparative Example 4), ultrasonically mix for 30 min, and after removing tetrahydrofuran, an epoxy resin curing system containing TDE-85 is obtained, and its processing window is 25 °C - 114 °C.

[0123] The obtained epoxy resin curing system containing TDE-85 was added into a mold and placed in a vacuum oven at 120 °C. The vacuum was pumped to remove the air and residual solvents in the resin. It was cured at 160 °C for 2 h, then the temperature was raised to 180 °C and cured for 2 h, and finally cooled naturally to obtain a resin casting. At room temperature (25 °C), the critical stress intensity factor (K IC ) of the casting was 1.85 MPa / m 1 / 2 . The flexural strength was 101 MPa, the flexural modulus was 3.12 GPa, the tensile strength was 70 MPa, and the tensile modulus was 3.74 GPa. The measured Tg was 325 °C, and T d5 was 121 °C.

[0124] Performance Testing

[0125] 1. The yields and purities of the low-viscosity trifunctional epoxy resin crude products provided in the test examples were tested, and the results are shown in Table 1.

[0126] Table 1

[0127]

[0128] From the data in Table 1, it can be seen that by comprehensively regulating the ring-opening addition reaction time and the ring-closure reaction time, the crude product can have a high purity. Examples 1-3 have a higher purity compared to Examples 4-5, and Examples 6-8 have a higher purity compared to Examples 9-10.

[0129] 2. The rheological properties of the epoxy resin curing systems in Application Example 1 and Application Example 2 were tested. The rheological curves are shown in Figure 1 、 Figure 2 . By analyzing Figure 1 、 Figure 2 , it can be known that the processing window of the epoxy resin curing system of p-TGMAP-25M is 25 °C - 218 °C; the processing window of the epoxy resin curing system of p-TGMAP-2M-MCDEA is 25 °C - 203 °C.

Claims

1. A low-viscosity trifunctional epoxy resin, characterized in that, Having the structure shown in Formula 1, wherein R1 is methyl and R2 is H or methyl.

2. The low-viscosity trifunctional epoxy resin according to claim 1, wherein It at least includes the following raw materials: methyl-substituted p-aminophenol, epichlorohydrin, a catalyst, and an aqueous alkali solution; the methyl-substituted p-aminophenol is 2,5-dimethyl-p-aminophenol or 2-methyl-p-aminophenol.

3. The low-viscosity trifunctional epoxy resin according to claim 2, wherein The molar ratio of the methyl-substituted p-aminophenol, epichlorohydrin, and the catalyst is 1.00:(6.00 - 12.00):(0.04 - 0.10).

4. The low-viscosity trifunctional epoxy resin according to claim 2, wherein, The catalyst is at least one of tetrabutylammonium bromide, tetraethylammonium bromide, triethylbenzylammonium chloride, triethylbenzylammonium bromide, or trimethylbenzylammonium bromide.

5. A method for preparing a low-viscosity trifunctional epoxy resin according to any one of claims 1-4, characterized in that, It at least includes the following steps: (1) Using methyl-substituted p-aminophenol and epichlorohydrin as raw materials, in the presence of a catalyst, control the temperature at 90 - 110 °C for ring-opening addition reaction for 6 - 12 h; (2) After the ring-opening addition reaction, add an aqueous alkali solution and carry out a ring-closure reaction at 30 - 50 °C for 6 - 12 h. After post-treatment, a crude product is obtained, and the crude product is purified to obtain a low-viscosity trifunctional epoxy resin.

6. The preparation method of the low-viscosity trifunctional epoxy resin according to claim 5, characterized in that, The methyl-substituted p-aminophenol is 2,5-dimethyl-p-aminophenol, the temperature of the ring-opening addition reaction is 80 °C, and the time is 9 h; the temperature of the ring-closure reaction is 40 °C, and the time is 8 - 12 h.

7. The preparation method of the low-viscosity trifunctional epoxy resin according to claim 5, characterized in that, The methyl-substituted p-aminophenol is 2-methyl-p-aminophenol, the temperature of the ring-opening addition reaction is 80 °C, and the time is 9 h; the temperature of the ring-closure reaction is 40 °C, and the time is 6 - 10 h.

8. The preparation method of the low-viscosity trifunctional epoxy resin according to claim 5, characterized in that, The purification method at least includes column chromatography purification.

9. An epoxy resin curing system containing the low-viscosity trifunctional epoxy resin according to any one of claims 1 to 4, characterized in that, The preparation raw materials at least include: containing a low-viscosity trifunctional epoxy resin, a curing agent, and a solvent. The molar ratio of the epoxy groups in the low-viscosity trifunctional epoxy resin to the active hydrogens in the curing agent is (0.8 - 1.1):1.

0.

10. The epoxy resin curing system according to claim 9, characterized in that, The curing agent is selected from one or more of 4,4'-methylenebis(3-chloro-2,6-diethylaniline), 4,4'-methylenedianiline, 4,4'-methylenebis(2-ethylaniline), 4,4'-methylenebis(2-chloroaniline), or 4,4'-methylenebis(3-chloro-2,6-diethylaniline).

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