Preparation method and application of thermoplastic epoxy resin

Abstract

The invention provides a preparation method and application of thermoplastic epoxy resin, and belongs to the technical field of high-performance materials. In the presence of an amine catalyst, the mass fraction of solute is controlled to be 50-70%, a compound A and a compound B are subjected to ring-opening linear polymerization in a solvent to obtain the thermoplastic epoxy resin, the compound A is an epoxy compound containing two epoxy groups, the structure of the compound B contains at least two reactive hydrogen, and the molar ratio of the compound A to the compound B is 1: (0.7-1). The reaction process is effectively controlled by regulating and controlling the solute mass fraction of the reaction system, so that the reaction selectivity is remarkably improved. The thermoplastic epoxy resin which has a linear structure, high molecular weight, uniform distribution, high strength, high toughness and transparency is successfully prepared by the method. The defects that the reaction activity is uncontrollable, a large number of branched chain structures are easily generated and gelation exists in the later stage of the reaction when thermoplastic epoxy resin is prepared through an existing in-situ polymerization reaction are effectively overcome.

Description

Technical Field

[0001] This application relates to a method for preparing thermoplastic epoxy resin and its application, belonging to the field of high-performance materials technology. Background Technology

[0002] Thermoplastic epoxy polymers are long-chain macromolecular thermoplastic polymers obtained through stepwise polymerization reactions of bifunctional epoxy resins and amines or phenolic compounds with two active hydrogen atoms. They possess melting and dissolving properties and, compared to traditional thermosetting epoxy resins, exhibit superior strength, toughness, processability, and adhesive properties. Compared to the dynamic covalent bonds in self-healing Vitrimer resins, whose melting process involves only physical changes, the melt processing of thermoplastic epoxy resins does not involve the breaking and recombination of chemical bonds, thus resulting in higher long-term environmental stability.

[0003] Traditional solvent-free polymerization methods use alkali metal compounds to catalyze the polymerization of bifunctional epoxy compounds and bifunctional phenolic compounds, which easily leads to product gelation. To address this issue, phosphorus-based compounds (such as triphenylphosphine) and imidazole-based compounds are introduced as selective catalysts to catalyze the reaction between epoxy groups and phenolic hydroxyl groups, while inhibiting reactions between epoxy groups and between epoxy groups and alcohol hydroxyl groups. However, these accelerators result in excessively fast reaction rates and are prone to generating branched structures. Furthermore, the products often exhibit orange to red hues, which limits the application of thermoplastic epoxy resins. Summary of the Invention

[0004] In view of this, this application provides a method for preparing thermoplastic epoxy resin, which controls the reaction rate by adjusting the mass fraction of solute, making the solution polymerization reaction more inclined to form linear polymers, thus solving the problem that the products of existing in-situ polymerization reactions are prone to gelation due to excessively fast reaction rates, and obtaining a transparent thermoplastic epoxy resin with high strength and high toughness.

[0005] Specifically, this application is implemented through the following scheme: A method for preparing a thermoplastic epoxy resin involves ring-opening linear polymerization of compound A and compound B in a solvent in the presence of an amine catalyst to obtain the thermoplastic epoxy resin. Compound A is an epoxy compound containing two epoxy groups. The structure of compound B contains at least two active hydrogen atoms. The molar ratio of compound A to compound B is 1:0.7~1.4.

[0006] Furthermore, as a preferred option: The compound A is at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, and alicyclic epoxy resin having a bilaterally symmetrical structure.

[0007] Compound B contains two hydroxyl groups and / or one amine group, with structural formulas satisfying nHO—R—OH and nR—NH2. Compound B is a bifunctional phenol, alcohol, or amine compound.

[0008] The amine catalyst accounts for 1-10% of the total reactants (compound A and compound B) by mass, and is selected as 3%.

[0009] The amine catalyst is at least one of triethylenetetramine, diethylenetrimine, tetraethylenepentamine, divinylpropylamine, montananediamine, N-aminoethylpiperazine, m-phenylenediamine, m-phenylenediamine, and dicyandiamide.

[0010] The solvent is one of acetone, methanol, n-hexane, and ethanol.

[0011] The reaction temperature for the ring-opening linear polymerization is 90~150 ℃, and the reaction time is 0.5~24 h.

[0012] The above preparation method can also be specifically expressed as the following process: Step 1: Weigh out compound A and pre-dissolve it in a solvent; Step 2: Weigh out compound B and pre-dissolve it in a solvent; Step 3: Weigh the amine catalyst and dissolve it in a solvent; Step 4: Add the solutions obtained in steps 1, 2, and 3 to three-necked flasks equipped with reflux condenser and mechanical stirrer for reaction. Step 5: Pour the high-viscosity liquid obtained from the reaction into a solvent and ultrasonically wash it until the supernatant of the epoxy resin solvent mixture is transparent and colorless; Step 6: Spread the washed product evenly (about 1-2 mm thick), dry it, and then apply it to the thermoplastic epoxy resin.

[0013] In the above process, based on the amount of solvent and compounds A, B, and amine catalysts added in steps one, two, and three, the solute mass fraction (W), i.e., the monomer concentration, is calculated: The monomer mass refers to the total mass of compound A, compound B, and the amine catalyst, while the solvent mass refers to the sum of the masses of solvents added in steps one, two, and three. In the preparation process, the preferred solute mass fraction is 50-70%, with 50-65% being more ideal.

[0014] An application of the thermoplastic epoxy resin prepared by the above method involves pulverizing the thermoplastic epoxy resin to obtain thermoplastic epoxy resin particles, dissolving the thermoplastic epoxy resin particles in N,N-dimethylacetamide using a solvent method, and then coating them onto a reinforcing material to obtain a prepreg.

[0015] The reinforcing material is any one of glass fiber, carbon fiber, or aramid fiber, and its addition amount is 50-70% of the mass of the thermoplastic epoxy resin.

[0016] The above-mentioned prepregs are used to obtain thermoplastic epoxy resin composite materials by vacuum bag pressing, molding or autoclave molding. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the TPE reaction process; Figure 2 TPE that has been partially dried; Figure 3 These are dried TPE granules; Figure 4 Infrared spectrum of TPE; Figure 5 The NMR spectrum of TPE. Detailed Implementation

[0018] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the technical solutions of this application will be further described in detail below with reference to specific examples in the embodiments of this application. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit the technical solutions of this application. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] Furthermore, the terms "A," "B," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features. "Multiple" means two or more, unless otherwise explicitly defined.

[0020] In the following examples, component A is bisphenol A type epoxy resin, component B is bisphenol A, component C is triethanolamine, and component D is N,N dimethylamide.

[0021] Example 1

[0022] This embodiment provides a method for preparing a thermoplastic epoxy resin (TPE) with a solute mass fraction, i.e., a monomer concentration of 50%, combined with... Figure 1 The steps are as follows: Step 1: Weigh 50 g of bisphenol A diglycidyl ether (DGEBA, component A) and 30 g of bisphenol A (BPA, component B) in a molar ratio of 1:0.7, and then weigh 0.24 g of triethanolamine (TEOA, component C).

[0023] Step 2: Dissolve the above three components separately in the solvent N,N dimethylamide (DMF), wherein the total mass of N,N dimethylamide is 80 g.

[0024] Step 3: Add the pre-dissolved component A from Step 2 into a three-necked flask equipped with reflux condenser and mechanical stirrer. Place the three-necked flask in an oil bath at a temperature of 60 °C and a stirring speed of 300 r / min for pre-dissolution.

[0025] Step 4: After stirring for 10 minutes, add the pre-dissolved component B and pre-dissolve it under the conditions of an oil bath temperature of 60℃ and a mechanical stirrer stirring speed of 300r / min.

[0026] Step 5: After stirring for 10 minutes, add the pre-dissolved component C. Pre-dissolve the component under the conditions of an oil bath temperature of 60 ℃ and a mechanical stirrer stirring speed of 300 r / min.

[0027] Step 6: After stirring for 10 minutes, raise the temperature to the reaction temperature of 150 °C and react for 8 hours.

[0028] Step 7: Pour the high-viscosity liquid obtained in Step 6 into methanol and ultrasonically wash it 2-3 times until the supernatant of the epoxy resin-methanol mixture is clear and colorless. The purpose is to remove unreacted monomer molecules and residual solvent, replacing them with a small amount of methanol to facilitate subsequent drying.

[0029] Step 8: Spread the cleaned product from Step 7 into a film approximately 1-2 mm thick. Figure 2 (Left side of the middle section) is placed in a drying oven for drying. The drying oven temperature is 100 ℃, and the drying time is 12 h.

[0030] Step nine, dry the product completely in step eight ( Figure 2 Middle right picture Figure 3 (Middle left image) The material was pulverized into granules using a mechanical pulverizer and then further dried in a vacuum oven at 100℃ for 24 hours. The final product was white thermoplastic epoxy resin granules. Figure 3 (The image in the middle right corner), denoted as TPE.

[0031] Example 2

[0032] This embodiment provides a method for preparing a thermoplastic epoxy resin with a solute mass fraction of 55%, which is the same as that in Example 1, except that: component A is bisphenol F type epoxy resin, component B is ethylene glycol, the molar ratio of component A to component B is 1:0.9, and in step two, the total mass of N,N dimethylamide is 65 g.

[0033] Example 3

[0034] This embodiment provides a method for preparing a thermoplastic epoxy resin with a solute mass fraction of 60%, which is the same as that in Example 1, except that: component A is bisphenol S type epoxy resin, component B is aniline, the molar ratio of component A to component B is 1:1, and in step two, the total mass of N,N dimethylamide is 53 g.

[0035] Example 4

[0036] This embodiment provides a method for preparing a thermoplastic epoxy resin with a solute mass fraction of 65%, which is the same as that in Example 1, except that: component A is hydrogenated bisphenol A type epoxy resin, component B is ethylene glycol, the molar ratio of component A to component B is 1:1.2, and in step two, the total mass of N,N dimethylamide is 43 g.

[0037] Example 5

[0038] This embodiment provides a method for preparing a thermoplastic epoxy resin with a solute mass fraction of 70%, which is the same as that in Example 1, except that: component A is bisphenol A type epoxy resin, component B is ethylene glycol, the molar ratio of component A to component B is 1:1.4, and in step two, the total mass of N,N dimethylamide is 34 g.

[0039] The thermoplastic epoxy resins obtained in Examples 1-5 were subjected to performance testing. The molecular weight and molecular weight distribution of TPE were tested according to ASTM D4001-13 "Standard Test Method for Molecular Weight and Distribution of Polymers (GPC Method)", the tensile properties of TPE were tested according to ASTM D638-22, and the flexural properties of TPE were tested according to ASTM D790-22. The fracture toughness of TPE was calculated by integrating the stress-strain curves. The results are shown in Table 1.

[0040] Table 1: Effect of different solute mass fractions on product properties Molecular weight (Mw) Molecular weight distribution (PDI) Tensile strength (MPa) Elongation at break (%) Bending strength (MPa) <![CDATA[Fracture toughness (MJ / m 3 )]]> Example 1 30761 1.73 60.1 20.1 143 10.99 Example 2 30052 1.98 62.1 59.7 144 25.64 Example 3 34695 1.57 60.2 27.3 157 10.26 Example 4 32229 1.63 65.3 20.2 169 10.60 Example 5 43078 1.29 63.1 39.1 185 8.55 Common thermosetting epoxy resin - - 54.9 6.5 - 1.89 .

[0041] As shown in Table 1, the tensile properties gradually increased with the increase of the solution mass fraction (W), from 60.1 MPa to 65.3 MPa, an increase of 8.6%. The tensile properties began to decrease when the solid content increased to 70%. Regarding the elongation at break, the thermoplastic epoxy resin under all conditions exhibited an elongation at break of over 20%, with the highest reaching 59.7% in Example 2. The fracture toughness was as high as 25 MJ / m. 3The above demonstrates excellent toughness. Its flexural strength also gradually increases with increasing solute mass fraction, from 143 MPa to 185 MPa, an increase of 29.4%, showing a significant improvement. Compared to ordinary thermosetting epoxy resins (cured using bisphenol A type epoxy resin and DETDA curing agent at 45℃ / 1h, 100℃ / 2h), the thermoplastic epoxy resin of this invention exhibits superior toughness.

[0042] The increased mechanical properties and excellent toughness mentioned above are mainly due to the larger molecular weight. The increase in molecular weight can effectively increase the entanglement molecular weight, thereby effectively preventing crack propagation and thus improving the mechanical properties to a certain extent.

[0043] To verify the linear structure of TPE, Fourier infrared spectroscopy and NMR analysis were performed on each example. The infrared spectra are shown below. Figure 4 It can be seen that under the conditions of each embodiment, the epoxy groups of the TPE synthesized at different solute mass fractions have completely disappeared, and a large number of hydroxyl groups have been generated.

[0044] and Figure 5 The NMR spectrum of TPE shows the linear structure of TPE (since each example corresponds to the same linear structure, only Example 1 is used as an example here), and the peak positions of each proton are marked in the figure, and the specific assignments are as follows: [δ, ppm] = 1.72 (g:-CH3), 2.45 (DMSO solvent peak), 3.8, 4.07 (d, d ' 3.90 (e:-CH2), 5.38 (c:-OH), 6.83 and 7.09 (a, b: benzene ring). Both infrared and nuclear magnetic resonance spectra indicate that the epoxy resin and bisphenol A underwent ring-opening polymerization.

[0045] Application Examples

[0046] The thermoplastic epoxy resin particles prepared in Examples 1-5 are used to prepare composite materials. The specific steps are as follows: the method of preimpregnating the reinforcing material with epoxy resin is not particularly limited, and can be a conventional method in the art, such as solution method or hot melt adhesive film method to prepare epoxy resin preimpregnate. The method of curing the epoxy preimpregnate of the present invention to obtain composite materials is not limited, for example, vacuum bag pressing, molding method or autoclave molding method, etc.

[0047] Using the thermoplastic epoxy resin obtained in Example 1 as raw material, a prepreg was prepared by solution method, and then a composite material was prepared by compression molding method.

[0048] S1, dissolve the thermoplastic epoxy resin particles with a mass fraction (W=50%) of the solution prepared in Example 1 in N,N dimethylamide solvent at a weight ratio of 1:1, heat and stir to obtain a colorless, viscous mixed liquid.

[0049] S2, the mixed liquid is uniformly coated onto the reinforcing fiber to obtain a prepreg. The reinforcing material is any one of glass fiber, carbon fiber, or aramid fiber. In this embodiment, glass fiber is used as an example. Its addition amount is 50% of the mass of thermoplastic epoxy resin particles. The tensile strength of the prepared thermoplastic composite material can reach 680 MPa and the flexural strength can reach 702 MPa.

[0050] S3. Place the prepreg in a forced-air drying oven and dry it to remove the solvent to obtain the finished prepreg.

[0051] S4. The prepreg is molded using a molding machine under specific temperature, pressure, and time conditions to obtain a thermoplastic epoxy resin composite material. The temperature is 240℃-300℃, the pressure is 0.5MPa-20MPa, and the time is 0.5-10h.

[0052] Comparative Example

[0053] The setup for this comparative example is the same as that for the application example, except that: in S1, a conventional thermoplastic epoxy resin, PKHH (molecular weight 36000 g / mol), is used from Huntsman Corporation of the United States.

[0054] The performance of the composite material in this application example was tested and compared with that prepared using conventional epoxy resin. The results are as follows: The thermoplastic epoxy resin carbon fiber composite material prepared in the application example has a tensile strength of up to 704 MPa and a flexural strength of up to 711 MPa. The tensile strength of the comparative example is up to 507 MPa and the flexural strength is up to 436 MPa.

[0055] The above-described embodiments are merely illustrative of several feasible implementations of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention, nor are the embodiments intended to limit the scope of protection in the claims of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention. All equivalent implementations or changes that do not depart from the present invention should be included in the technology of the present invention.

Claims

1. A method for preparing a thermoplastic epoxy resin, characterized in that: In the presence of an amine catalyst, with the solute mass fraction controlled at 50-70%, compound A and compound B undergo ring-opening linear polymerization in a solvent to obtain a thermoplastic epoxy resin. Compound A is an epoxy compound containing two epoxy groups. The structure of compound B contains at least two active hydrogen atoms. The molar ratio of compound A to compound B is 1:0.7~1.

4.

2. The method for preparing a thermoplastic epoxy resin according to claim 1, characterized in that: The compound A is at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, and alicyclic epoxy resin having a bilaterally symmetrical structure.

3. The method for preparing a thermoplastic epoxy resin according to claim 1, characterized in that: The structure of compound B contains two hydroxyl groups and / or one amine group, and its structural formula satisfies nHO—R—OH, nR—NH2.

4. The method for preparing a thermoplastic epoxy resin according to claim 1, characterized in that: The amine catalyst accounts for 1-10% of the total reactants by mass.

5. The method for preparing a thermoplastic epoxy resin according to claim 1, characterized in that: The amine catalyst is at least one of triethylenetetramine, diethylenetrimine, tetraethylenepentamine, divinylpropylamine, montananediamine, N-aminoethylpiperazine, m-phenylenediamine, m-phenylenediamine, and dicyandiamide.

6. The method for preparing a thermoplastic epoxy resin according to claim 1, characterized in that: The solvent is one of acetone, methanol, n-hexane, and ethanol.

7. The method for preparing a thermoplastic epoxy resin according to claim 1, characterized in that: The reaction temperature for ring-opening linear polymerization is 90~150 ℃, and the reaction time is 0.5~24 h.

8. A method for preparing a thermoplastic epoxy resin according to any one of claims 1 to 7, characterized in that: The solute mass fraction for ring-opening linear polymerization is 50-60%.

9. An application of a thermoplastic epoxy resin prepared by the method of claim 1, characterized in that: A prepreg is prepared by dissolving thermoplastic epoxy resin particles in N,N-dimethylacetamide using a solvent method, and then coating the prepreg onto a reinforcing material. The reinforcing material is any one of glass fiber, carbon fiber, or aramid fiber, and its addition amount is 50-70% of the mass of the thermoplastic epoxy resin.

10. The application according to claim 9, characterized in that: The prepreg is used to obtain thermoplastic epoxy resin composite materials through vacuum bag pressing, molding or autoclave molding.

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