Aqueous epoxy resin and a method for producing the same, aqueous epoxy resin sizing agent and a method for producing and using the same

Abstract

The application belongs to the technical field of carbon fiber preparation, and relates to a water-based epoxy resin and a preparation method thereof, a water-based epoxy resin sizing agent and a preparation method and application thereof. The water-based epoxy resin is obtained by reacting N,N-bis(2-hydroxypropyl)succinamic acid with a terminal carboxyl group and diisopropanolamine modified epoxy resin with a terminal hydroxyl group. The water-based epoxy resin sizing agent is obtained by mixing the water-based epoxy resin and water. The application is to apply the water-based epoxy resin sizing agent to the sizing treatment of carbon fibers. The application does not need additional catalysts, complex emulsification steps and additives, and the process is simple.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of carbon fiber preparation, and relates to a water-based epoxy resin and a preparation method thereof, a water-based epoxy resin sizing agent and a preparation method and application thereof. BACKGROUND

[0002] Carbon fibers have excellent properties, including high specific strength, high specific modulus, excellent thermal stability, etc., and are widely used in the form of composite materials in the fields of automobiles, buildings, aerospace, etc. However, due to the high-temperature carbonization and graphitization steps in the preparation process of carbon fibers, the surface thereof is a kind of chemically inert, non-polar low-surface-energy surface, which greatly limits the bonding performance of carbon fibers and resin matrix, so that the potential performance of carbon fiber reinforced resin matrix composite materials cannot be fully utilized. Therefore, it is necessary to modify the surface of carbon fibers to improve the bonding ability thereof with resin, and the sizing agent method is one of the surface modification methods. The sizing agent can not only improve the bunching and processability of carbon fibers, but also improve the adhesion between carbon fibers and matrix resin, thereby enhancing the performance of the final composite material product.

[0003] Sizing agents are mainly divided into solvent-based sizing agents and water-based sizing agents. Solvent-based sizing agents usually contain organic solvents such as acetone and tetrahydrofuran, which have adverse effects on the health of production personnel and the environment. Nowadays, solvent-based sizing agents have been gradually replaced by water-based sizing agents.

[0004] Water emulsion type sizing agent is a kind of water-based sizing agent, which is generally prepared by adding emulsifiers and water to hydrophobic resin through mechanical method or phase inversion method to form an emulsion. For example, patent application CN113818250A discloses a sizing agent for carbon fibers, in which bisphenol A type epoxy resin is mixed with polyol and catalyst to prepare hyperbranched prepolymer, and the hyperbranched prepolymer is compounded with emulsifier, dispersant and water to prepare carbon fiber sizing agent. Patent CN109881486B discloses a preparation method of hyperbranched emulsifier, in which long-chain polyol, multifunctional modifier and epoxy compound are reacted under certain catalyst and temperature conditions to obtain emulsifier with hyperbranched structure, and then the emulsifier is wrapped on the surface of epoxy resin oil droplets by phase inversion method to prepare water-based sizing agent emulsion. Patent application CN109868654A discloses an easily emulsified water-based epoxy sizing agent and a preparation method thereof, in which hyperbranched emulsifier is first synthesized by long-chain polyol, multifunctional modifier, epoxy compound and catalyst; then epoxy resin is uniformly mixed with the hyperbranched emulsifier (material A), and auxiliary emulsifier and dispersant are dissolved in deionized water (material B); material B is slowly added to material A in a high-speed shearing emulsifier to perform phase inversion emulsification, thereby obtaining water-based epoxy sizing agent. In the above three patents or patent applications, the preparation process of the sizing agent is relatively complex, and various additives (emulsifiers, auxiliary agents) are introduced in the preparation process, which may deteriorate the final performance of the composite material.

[0005] Patent CN104448245B discloses a preparation method of hyperbranched epoxy emulsion, a polyamine is reacted with an epoxy resin to synthesize a hyperbranched epoxy resin; the hyperbranched epoxy resin is reacted with a hydrophilic polyether under the action of a catalyst to obtain a hydrophilic modified hyperbranched epoxy resin; and deionized water is added to the hydrophilic modified hyperbranched epoxy resin, and a hyperbranched epoxy emulsion is prepared by shearing and stirring. The patent needs to add a catalyst in the second modification, and the residual catalyst may affect the storage stability of the emulsion or the performance of the final coating. At the same time, the hydrophilic modified hyperbranched epoxy resin is heated to 60 DEG C, and 50% of deionized water of the mass of the hydrophilic modified hyperbranched epoxy resin is added and stirred uniformly, then the temperature is lowered to 40 DEG C, and then 1-1.5 times of deionized water of the mass of the hydrophilic modified hyperbranched epoxy resin is added to the mixed system and stirred or subjected to high shear to prepare the hyperbranched epoxy emulsion. The preparation steps are very complex, and the temperature needs to be controlled, the deionized water needs to be added in batches, and high shear operation needs to be performed.

[0006] In summary, the existing preparation technologies of waterborne epoxy resin carbon fiber sizing agent generally have defects such as dependence on catalyst, need for complex phase inversion / emulsification steps, introduction of additives, or complicated process, and it is difficult to simultaneously meet the needs of process simplicity, emulsion stability, and interface enhancement performance of the composite material. Therefore, it is of great significance to develop a sizing agent without additional catalyst, without complex emulsification process, and with excellent performance. SUMMARY

[0007] The purpose of the present application is to solve the problems existing in the prior art, and to provide a waterborne epoxy resin and a preparation method thereof, a waterborne epoxy resin sizing agent and a preparation method and application thereof.

[0008] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0009] A preparation method of a waterborne epoxy resin, in which a carboxyl group-containing N,N-bis(2-hydroxypropyl)succinamic acid with a molar ratio of 4-8:1 is reacted with a diisopropanolamine modified epoxy resin with a hydroxyl group as a terminal group at 110-150 DEG C for 4-8 h to obtain the waterborne epoxy resin, wherein the structural formula of the N,N-bis(2-hydroxypropyl)succinamic acid is as follows:

[0010] .

[0011] The application does not need to add catalyst for preparing the water-based epoxy resin, because the esterification reaction between the N,N-bis(2-hydroxypropyl)succinamic acid with carboxyl end group and the diisopropanolamine modified epoxy resin with hydroxyl end group is used in the application, and the N,N-bis(2-hydroxypropyl)succinamic acid itself can bring acidity to the system, catalyze the esterification reaction, and no additional catalyst needs to be added compared with the ring-opening reaction of the hydroxyl group and the epoxy group in the prior art.

[0012] The water-based epoxy resin prepared by the application is composed of the epoxy resin and the hyperbranched segment (formed by the dehydration condensation reaction of the N,N-bis(2-hydroxypropyl)succinamic acid) connected thereto, and the water-based epoxy resin has excellent water solubility because:

[0013] (1) The molar ratio of the N,N-bis(2-hydroxypropyl)succinamic acid with carboxyl end group and the diisopropanolamine modified epoxy resin with hydroxyl end group is appropriate, so that the grafting rate of the hyperbranched segment in the water-based epoxy resin is between 5% and 25%. If the grafting rate is too low, the hydrophilicity of the water-based epoxy resin is insufficient, and it is difficult to form a stable emulsion in water. If the grafting rate is too high, the hydrophilicity of the water-based epoxy resin is too strong, which can seriously damage the water resistance and chemical resistance of the cured film.

[0014] (2) The temperature (110-150°C) and time (4-8h) of the hyperbranched modification are appropriate, so that the branching degree of the hyperbranched segment in the water-based epoxy resin is between 0.4 and 0.8. If the branching degree is too low, the molecular structure of the hyperbranched segment is close to that of a linear polymer, and the advantages of the hyperbranched structure cannot be fully utilized. If the branching degree is too high, the molecular structure of the hyperbranched segment can be too rigid, and the compatibility with the epoxy resin is poor.

[0015] As a preferred technical solution:

[0016] The preparation method of the water-based epoxy resin as described above does not contain catalyst in the reaction system, and the catalyst is not a necessary substance in the application. If the catalyst is added, the water-based epoxy resin can be more efficiently prepared, but the residual catalyst can affect the performance of the subsequent product.

[0017] The preparation method of the water-based epoxy resin as described above has the following specific steps:

[0018] (a) Dissolve succinic anhydride and diisopropanolamine in a third solvent (N,N-dimethylformamide or N,N-dimethylacetamide), keep a constant stirring rate (500-700r / min), and react at 60-90°C for 1-4h. After the reaction is completed, cool to room temperature to discharge, and obtain the system A containing N,N-bis(2-hydroxypropyl)succinamic acid;

[0019] In the process, the lone pair of electrons on the amino nitrogen atom of diisopropanolamine attacks one carbonyl carbon atom of succinic anhydride, leading to the breaking of the anhydride bond, the opening of the five-membered ring, and the generation of N,N-bis(2-hydroxypropyl)succinamic acid;

[0020] (b) adding the diisopropanolamine solution dropwise into the epoxy resin solution, keeping a constant stirring rate (500-700 r / min), and reacting at 70-100 ℃ for 2-5 h to obtain a system B containing diisopropanolamine-modified epoxy resin;

[0021] In the process, the amino group of diisopropanolamine reacts with the epoxy group of the epoxy resin to generate diisopropanolamine-modified epoxy resin.

[0022] (c) adding the system A dropwise into the system B, controlling the molar ratio of N,N-bis(2-hydroxypropyl)succinamic acid in the system A to diisopropanolamine-modified epoxy resin in the system B to be 4-8:1, keeping a constant stirring rate (500-700 r / min), and reacting at 110-150 ℃ for 4-8 h, and then removing the solvent by reduced pressure distillation (temperature: 60-90 ℃, time: 30-60 min) to obtain the waterborne epoxy resin.

[0023] The preparation reaction equation of the waterborne epoxy resin is shown in Figure 2 .

[0024] The preparation method of the waterborne epoxy resin described above, in step (a), the mass ratio of succinic anhydride to diisopropanolamine is 1:1.33-2.

[0025] The preparation method of the waterborne epoxy resin described above, in step (a), the mass-volume ratio of succinic anhydride to the third solvent is 3.75-10.00 g:25 mL; in step (b), the diisopropanolamine solution is obtained by dissolving diisopropanolamine in the first solvent (N,N-dimethylformamide or N,N-dimethylacetamide), the epoxy resin solution is obtained by dissolving the epoxy resin in the second solvent (N,N-dimethylformamide or N,N-dimethylacetamide), the mass-volume ratio of diisopropanolamine to the first solvent is 1.66-6.66 g:10-20 mL, the mass-volume ratio of the epoxy resin to the second solvent is 4.90-11.75 g:10 mL, and the volume ratio of the epoxy resin solution to the diisopropanolamine solution is 1:1-2.

[0026] The preparation method of the waterborne epoxy resin described above, the epoxy resin is one or more of epoxy resin E51, epoxy resin E44, epoxy resin E20, and epoxy resin E12.

[0027] The preparation method of the water-based epoxy resin as described above, in step (b), the epoxy resin solution is heated to 70-100℃ first, and then the diisopropanolamine solution is added dropwise into the epoxy resin solution.

[0028] The preparation method of the water-based epoxy resin as described above, in step (c), system B is heated to 110-150℃ first, and then system A is added dropwise into system B.

[0029] The application further provides a water-based epoxy resin prepared by the preparation method of the water-based epoxy resin as described above.

[0030] The application further provides a preparation method of a water-based epoxy resin sizing agent, wherein the water-based epoxy resin as described above is added into water, and stirred at a stirring speed of 500-700 r / min until completely dissolved (the time consumption is 15-30 min), and the water-based epoxy resin sizing agent is obtained.

[0031] Since the water-based epoxy resin has excellent water solubility, the water-based epoxy resin sizing agent can be prepared by directly dissolving in a certain amount of water under low-speed stirring without emulsification.

[0032] As a preferred technical solution,

[0033] The preparation method of the water-based epoxy resin sizing agent as described above, the mass ratio of the water-based epoxy resin to water is 0.1-2.5:100.

[0034] The application further provides a water-based epoxy resin sizing agent prepared by the preparation method of the water-based epoxy resin sizing agent as described above; the water-based epoxy resin sizing agent is not stratified after standing for 1 month at 15-30℃, and is not stratified after centrifugation for 30 min at a rotation speed of 3000 r / min, so that the water-based epoxy resin sizing agent has good storage stability and mechanical stability.

[0035] The application further provides an application of the water-based epoxy resin sizing agent as described above, which is used for sizing treatment of carbon fibers.

[0036] Beneficial effects:

[0037] (1) The water-based epoxy resin prepared by the application does not need to add an additional catalyst, and the influence of residual catalyst on the performance of subsequent products can be avoided, and the problem that the catalyst is relied on in the prior art and the catalyst residue easily affects the storage stability of the emulsion or the performance of the final coating is solved.

[0038] (2) The water-based epoxy resin sizing agent prepared by the method of the present application does not need an emulsification step, and does not need to introduce additives such as emulsifiers and dispersants, thereby solving the problems of the prior art, i.e. the need for a complex phase inversion / emulsification step and the introduction of additives which may deteriorate the final performance of the composite material.

[0039] (3) The overall process of the present application is simple, thereby solving the problem of the prior art that the preparation process is complicated; the preparation steps of the water-based epoxy resin are clear, and do not need complex temperature control operations; the preparation of the sizing agent only needs to be stirred and dissolved, and does not need complex operations such as batch water addition and high shear, thereby simplifying the overall process. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 Fig. 1 is a scanning electron microscope image of carbon fibers which have not been subjected to sizing treatment, and Fig. 2 is a scanning electron microscope image of carbon fibers which have been subjected to sizing treatment by the water-based epoxy resin sizing agent of Example 7;

[0041] Figure 2 Fig. 3 is a preparation reaction equation of the water-based epoxy resin. DETAILED DESCRIPTION

[0042] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and are not used to limit the scope of the present application. Furthermore, it should be understood that after reading the content taught by the present application, those skilled in the art can make various modifications or changes to the present application, and these equivalent forms also fall within the scope defined by the claims of the present application.

[0043] In order to ensure that the properties of the substances used in the embodiments are fully disclosed, the manufacturer information of the substances is written in the present application; in addition, the products of other manufacturers which meet the definition of the present application can also be applicable.

[0044] The following are the test methods of the relevant performance indicators in each embodiment:

[0045] Interface shear strength: a composite material interface performance evaluation device (MODEL HM410, Japan) is used for testing, and the sample needs to be prepared in advance before testing: the single filament of the sample to be tested is fixed on the iron sheet matched with the instrument, a acupuncture needle is used to dip a small amount of epoxy resin system (consisting of epoxy resin E51, triethylene tetramine and acetone with a mass ratio of 10:1:3; the manufacturer of the epoxy resin is Hangzhou Wuhuihang Adhesive Co., Ltd.), and the resin microspheres are formed on the surface of the sample by gently scraping, and then the sample is placed in an oven and cured at 120°C for 3h to obtain the experimental sample; during the test, the microspheres with a diameter of 40-60μm are selected, the fiber diameter and the microsphere embedding length are measured; the distance between the upper and lower blades is adjusted to be greater than the diameter of the single filament and less than the height of the microspheres; the single filament is moved to the left at a speed of 0.12mm / min until the resin microspheres are stripped from the fiber, and the maximum force value is recorded, and the interface shear strength (τ) is calculated according to the formula: In the formula, τ is the interfacial shear strength, with units of MPa; Fmax is the maximum force value, with units of N; d is the fiber diameter, with units of mm; and L is the microsphere embedding length, with units of mm. The test results are averaged from no less than 20 times.

[0046] Example 1

[0047] A preparation method of an aqueous epoxy resin sizing agent, and the specific steps are as follows:

[0048] (1) Preparation of materials;

[0049] The first solvent, the second solvent and the third solvent are all N,N-dimethylacetamide;

[0050] Diisopropanolamine;

[0051] Epoxy resin: epoxy resin E51, manufacturer: Hangzhou Wuhaihang Adhesive Co., Ltd.;

[0052] Succinic anhydride;

[0053] Water;

[0054] (2) Preparation of diisopropanolamine solution and epoxy resin solution;

[0055] The diisopropanolamine solution is obtained by dissolving diisopropanolamine in the first solvent, and the mass-volume ratio of diisopropanolamine to the first solvent is 3.33g:15mL; the epoxy resin solution is obtained by dissolving epoxy resin in the second solvent, and the mass-volume ratio of epoxy resin to the second solvent is 4.90g:10mL;

[0056] (3) Preparation of aqueous epoxy resin;

[0057] (a) Dissolve succinic anhydride and diisopropanolamine in the third solvent, keep the stirring rate at 600r / min, and react at 70℃ for 2h, then cool to room temperature after reaction, and discharge to obtain system A containing N,N-bis(2-hydroxypropyl) succinamide acid; wherein the mass ratio of succinic anhydride to diisopropanolamine is 1:1.33, and the mass-volume ratio of succinic anhydride to the third solvent is 10g:25mL;

[0058] (b) First, heat the epoxy resin solution to 80℃, then add the diisopropanolamine solution dropwise into the epoxy resin solution, keep the stirring rate at 600r / min, and react for 3h to obtain system B containing diisopropanolamine modified epoxy resin, wherein the volume ratio of the epoxy resin solution to the diisopropanolamine solution is 1:1.5;

[0059] (c) first heat system B to 120℃, then add system A drop by drop into system B, control the molar ratio of N,N-bis(2-hydroxypropyl)succinamic acid in system A and diisopropanolamine modified epoxy resin in system B as 8:1, keep the stirring rate as 600r / min, react for 5h, remove all the solvent, then the water-based epoxy resin is obtained;

[0060] (4) preparation of water-based epoxy resin sizing agent;

[0061] Add the water-based epoxy resin into water, stir at the stirring rate of 600r / min until completely dissolved, then the water-based epoxy resin sizing agent is obtained; wherein the mass ratio of water-based epoxy resin and water is 0.5:100.

[0062] The finally prepared water-based epoxy resin sizing agent is not stratified at 15-30℃ for 1 month, and is not stratified at the centrifugal speed of 3000r / min for 30min.

[0063] Example 2

[0064] A preparation method of a water-based epoxy resin sizing agent, the specific steps are as follows:

[0065] (1) preparation of materials;

[0066] The first solvent, the second solvent and the third solvent are all N,N-dimethylacetamide;

[0067] Diisopropanolamine;

[0068] Epoxy resin: epoxy resin E44, manufacturer is Hangzhou Wuhuihang Adhesive Co., Ltd.;

[0069] Butanedioic anhydride;

[0070] Water;

[0071] (2) preparation of diisopropanolamine solution and epoxy resin solution;

[0072] The diisopropanolamine solution is obtained by dissolving diisopropanolamine in the first solvent, and the mass volume ratio of diisopropanolamine and the first solvent is 6.66g:20mL; the epoxy resin solution is obtained by dissolving epoxy resin in the second solvent, and the mass volume ratio of epoxy resin and the second solvent is 11.75g:10mL;

[0073] (3) preparation of water-based epoxy resin;

[0074] (a) Succinic anhydride and diisopropanolamine are dissolved in a third solvent, the stirring rate is kept at 500 r / min, and the reaction is carried out at 60℃ for 4h. After the reaction is completed, the temperature is cooled to room temperature, and the product is discharged. System A containing N,N-bis(2-hydroxypropyl)succinamic acid is obtained. The mass ratio of succinic anhydride to diisopropanolamine is 1:1.53, and the mass-volume ratio of succinic anhydride to the third solvent is 10g:25mL;

[0075] (b) The epoxy resin solution is first heated to 70℃, and then the diisopropanolamine solution is added dropwise into the epoxy resin solution, the stirring rate is kept at 500 r / min, and the reaction is carried out for 5h. System B containing diisopropanolamine modified epoxy resin is obtained. The volume ratio of the epoxy resin solution to the diisopropanolamine solution is 1:2;

[0076] (c) System B is first heated to 110℃, and then system A is added dropwise into system B. The molar ratio of N,N-bis(2-hydroxypropyl)succinamic acid in system A to diisopropanolamine modified epoxy resin in system B is controlled to be 4:1, the stirring rate is kept at 500 r / min, and the reaction is carried out for 8h. After all the solvents are removed, the water-based epoxy resin is obtained;

[0077] (4) Preparation of a water-based epoxy resin sizing agent;

[0078] The water-based epoxy resin is added into water, and stirred at a stirring rate of 500 r / min until it is completely dissolved. The water-based epoxy resin sizing agent is obtained. The mass ratio of the water-based epoxy resin to water is 0.1:100.

[0079] The finally prepared water-based epoxy resin sizing agent is placed at 15-30℃ for 1 month without stratification, and centrifuged at a rotation speed of 3000 r / min for 30min without stratification.

[0080] Example 3

[0081] A preparation method of a water-based epoxy resin sizing agent is provided, and the specific steps are as follows:

[0082] (1) Preparation of materials;

[0083] The first solvent, the second solvent, and the third solvent are all N,N-dimethylformamide;

[0084] Diisopropanolamine;

[0085] Epoxy resin: Epoxy resin E20, manufacturer: Jiangsu Sanmu Group Co., Ltd.;

[0086] Succinic anhydride;

[0087] Water;

[0088] (2) Preparation of diisopropanolamine solution and epoxy resin solution;

[0089] The diisopropanolamine solution is obtained by dissolving diisopropanolamine in the first solvent, and the mass-volume ratio of diisopropanolamine to the first solvent is 1.66 g:10 mL; the epoxy resin solution is obtained by dissolving epoxy resin in the second solvent, and the mass-volume ratio of epoxy resin to the second solvent is 6.25 g:10 mL;

[0090] (3) Preparation of the waterborne epoxy resin;

[0091] (a) Dissolve succinic anhydride and diisopropanolamine in the third solvent, keep the stirring rate at 650 r / min, and react at 80℃ for 3 h. After the reaction is completed, cool to room temperature and discharge to obtain system A containing N,N-bis(2-hydroxypropyl)succinamide acid; wherein the mass ratio of succinic anhydride to diisopropanolamine is 1:1.83, and the mass-volume ratio of succinic anhydride to the third solvent is 3.75 g:25 mL;

[0092] (b) First heat the epoxy resin solution to 90℃, then add the diisopropanolamine solution dropwise into the epoxy resin solution, keep the stirring rate at 650 r / min, and react for 4 h to obtain system B containing diisopropanolamine modified epoxy resin, wherein the volume ratio of the epoxy resin solution to the diisopropanolamine solution is 1:1;

[0093] (c) First heat system B to 130℃, then add system A dropwise into system B, control the molar ratio of N,N-bis(2-hydroxypropyl)succinamide acid in system A to diisopropanolamine modified epoxy resin in system B to be 6:1, keep the stirring rate at 650 r / min, and react for 6 h to remove all solvents to obtain the waterborne epoxy resin;

[0094] (4) Preparation of the waterborne epoxy resin sizing agent;

[0095] Add the waterborne epoxy resin into water, and stir at a stirring rate of 700 r / min until completely dissolved to obtain the waterborne epoxy resin sizing agent; wherein the mass ratio of the waterborne epoxy resin to water is 2.5:100.

[0096] The finally prepared waterborne epoxy resin sizing agent is not stratified after standing at 15-30℃ for 1 month, and is not stratified after centrifugation at a rotation speed of 3000 r / min for 30 min.

[0097] Example 4

[0098] A preparation method of a waterborne epoxy resin sizing agent, the specific steps are as follows:

[0099] (1) Preparation of materials;

[0100] The first solvent, the second solvent, and the third solvent are all N,N-dimethylformamide;

[0101] Diisopropanolamine;

[0102] Epoxy resin: Epoxy resin E12, manufacturer Jiangsu Sanmu Group Co., Ltd.;

[0103] Succinic anhydride;

[0104] Water;

[0105] (2) Diisopropanolamine solution and epoxy resin solution are prepared;

[0106] The diisopropanolamine solution is obtained by dissolving diisopropanolamine in a first solvent, and the mass-volume ratio of diisopropanolamine to the first solvent is 1.66 g:10 mL; the epoxy resin solution is obtained by dissolving epoxy resin in a second solvent, and the mass-volume ratio of epoxy resin to the second solvent is 10.63 g:10 mL;

[0107] (3) Waterborne epoxy resin is prepared;

[0108] (a) Succinic anhydride and diisopropanolamine are dissolved in a third solvent, the stirring rate is kept at 700 r / min, and the reaction is carried out at 90℃ for 1 h; after the reaction is completed, the temperature is cooled to room temperature, and the product is discharged, to obtain system A containing N,N-bis(2-hydroxypropyl)succinamic acid; wherein the mass ratio of succinic anhydride to diisopropanolamine is 1:2, and the mass-volume ratio of succinic anhydride to the third solvent is 4.38 g:25 mL;

[0109] (b) The epoxy resin solution is heated to 100℃, and then the diisopropanolamine solution is added dropwise into the epoxy resin solution, the stirring rate is kept at 700 r / min, and the reaction is carried out for 2 h, to obtain system B containing diisopropanolamine modified epoxy resin; wherein the volume ratio of the epoxy resin solution to the diisopropanolamine solution is 1:1;

[0110] (c) System B is heated to 150℃, and then system A is added dropwise into system B, the molar ratio of N,N-bis(2-hydroxypropyl)succinamic acid in system A to diisopropanolamine modified epoxy resin in system B is controlled to be 7:1, the stirring rate is kept at 700 r / min, and the reaction is carried out for 4 h; after all the solvents are removed, a waterborne epoxy resin is obtained;

[0111] (4) Waterborne epoxy resin sizing agent is prepared;

[0112] The waterborne epoxy resin is added into water, and stirred at a stirring rate of 650 r / min until completely dissolved, to obtain a waterborne epoxy resin sizing agent; wherein the mass ratio of the waterborne epoxy resin to water is 1.5:100.

[0113] The prepared water-based epoxy resin sizing agent is not stratified at 15-30 DEG C for 1 month and is not stratified at a centrifugal speed of 3000 r / min for 30 min.

[0114] Example 5

[0115] The preparation method of the water-based epoxy resin sizing agent is different from that of Example 5 only in that, in step (2), the mass-volume ratio of diisopropanolamine to the first solvent is 6.66 g:15 mL; and the mass-volume ratio of the epoxy resin to the second solvent is 9.8 g:10 mL.

[0116] The prepared water-based epoxy resin sizing agent is not stratified at 15-30 DEG C for 1 month and is not stratified at a centrifugal speed of 3000 r / min for 30 min.

[0117] Example 6

[0118] The preparation method of the water-based epoxy resin sizing agent is different from that of Example 5 only in that, in step (c), the reaction time is 8 h.

[0119] The prepared water-based epoxy resin sizing agent is not stratified at 15-30 DEG C for 1 month and is not stratified at a centrifugal speed of 3000 r / min for 30 min.

[0120] The prepared water-based epoxy resin sizing agent can be applied to the sizing treatment of carbon fibers.

[0121] Example 7

[0122] The preparation method of the water-based epoxy resin sizing agent is different from that of Example 5 only in that, in step (4), the mass ratio of the water-based epoxy resin to water is 1.5:100.

[0123] The prepared water-based epoxy resin sizing agent is not stratified at 15-30 DEG C for 1 month and is not stratified at a centrifugal speed of 3000 r / min for 30 min.

[0124] The water-based epoxy resin in each of the examples is respectively added into water and stirred for 30 min to obtain a sample solution with a concentration of 1 mg / mL, and an Anton Paar nanoparticle size meter and a Zeta potential analyzer are used for testing, and the average particle sizes of the sample solutions corresponding to the modified epoxy resins in Examples 1-7 are 102 nm, 70 nm, 85 nm, 90 nm, 64 nm, 67 nm and 64 nm respectively. Therefore, it can be deduced that the average particle size of the prepared water-based epoxy resin sizing agent is small, which is beneficial to the infiltration on the surface of carbon fibers.

[0125] The sizing agents prepared in Examples 1-7 are respectively used for carbon fibers (manufactured by Jiangsu Hengshen Co., Ltd., and the article number is HF40), and a scanning electron microscope is used for observation.Figure 1 After the sizing treatment (the carbon fiber is soaked in the water-based epoxy resin sizing agent at room temperature for 5 min, then taken out and placed in an oven at 100 DEG C for 3 h to obtain the sized carbon fiber) of the sizing agent in the examples (a1) and (a2) and (b1) and (b2), the interfacial shear strength of the obtained sized carbon fiber and the epoxy resin is shown in Table 1. From Table 1, it can be seen that the interfacial properties of the carbon fiber sized by the sizing agent of each example are obviously improved relative to the carbon fiber without sizing treatment, indicating that the water-based epoxy resin sizing agent prepared by the present application can effectively improve the wettability and adhesion of the carbon fiber surface, fully verifying the effectiveness of the sizing agent in improving the interfacial properties of the carbon fiber composite material. Among them, the scanning electron microscope of the carbon fiber sized by the water-based epoxy resin sizing agent of Example 7 is as shown in Figure 1 Comparative Figure 1 As can be seen from the examples (a1) and (a2), (b1) and (b2), the surface of the unsized carbon fiber is very smooth, with slight grooves along the fiber axis; the surface of the sized carbon fiber becomes uneven, forming a dense sizing layer.

[0126] Table 1:

[0127] Sample Interfacial shear strength of carbon fiber with epoxy resin (MPa) Example 1 44.33 Example 2 40.55 Example 3 50.60 Example 4 46.58 Example 5 46.27 Example 6 44.97 Example 7 52.30 Carbon fiber without sizing treatment 34.75 .

Claims

1. A method for preparing an aqueous epoxy resin, characterized by, Reacting carboxyl group-containing N,N-bis(2-hydroxypropyl)succinamic acid with a molar ratio of 4-8:1 and diisopropanolamine modified epoxy resin with a hydroxyl end group at 110-150 DEG C for 4-8 h, to obtain the water-based epoxy resin, wherein the structural formula of N,N-bis(2-hydroxypropyl)succinamic acid is as follows: 。 2. The method for preparing an aqueous epoxy resin according to claim 1, characterized in that, The reaction system does not contain a catalyst.

3. The method for preparing an aqueous epoxy resin according to claim 1, characterized in that, The specific steps are as follows: (a) Dissolving succinic anhydride and diisopropanolamine in a third solvent, keeping a constant stirring rate, and reacting at 60-90 DEG C for 1-4 h; after the reaction is completed, cooling to room temperature to discharge, to obtain system A containing N,N-bis(2-hydroxypropyl)succinamic acid; (b) Adding diisopropanolamine solution dropwise into epoxy resin solution, keeping a constant stirring rate, and reacting at 70-100 DEG C for 2-5 h, to obtain system B containing diisopropanolamine modified epoxy resin; (c) Adding system A dropwise into system B, controlling the molar ratio of N,N-bis(2-hydroxypropyl)succinamic acid in system A and diisopropanolamine modified epoxy resin in system B to be 4-8:1, keeping a constant stirring rate, and reacting at 110-150 DEG C for 4-8 h, to remove the solvent, to obtain the water-based epoxy resin.

4. The method for preparing an aqueous epoxy resin according to claim 3, characterized in that, In step (a), the mass ratio of succinic anhydride to diisopropanolamine is 1:1.33-2.

5. The method for preparing an aqueous epoxy resin according to claim 3, characterized in that, In step (a), the mass-volume ratio of succinic anhydride to the third solvent is 3.75-10.00 g:25 mL; in step (b), the diisopropanolamine solution is obtained by dissolving diisopropanolamine in a first solvent, and the epoxy resin solution is obtained by dissolving epoxy resin in a second solvent; the mass-volume ratio of diisopropanolamine to the first solvent is 1.66-6.66 g:10-20 mL, the mass-volume ratio of epoxy resin to the second solvent is 4.90-11.75 g:10 mL, and the volume ratio of the epoxy resin solution to the diisopropanolamine solution is 1:1-2.

6. An aqueous epoxy resin, characterized by The water-based epoxy resin is prepared by using the preparation method of the water-based epoxy resin according to any one of claims 1-5.

7. A method for preparing an aqueous epoxy sizing agent, characterized by, The water-based epoxy resin is added into water, and stirred at a stirring rate of 500-700 r / min until completely dissolved, to obtain the water-based epoxy resin sizing agent.

8. The method for preparing an aqueous epoxy resin sizing agent according to claim 7, characterized in that, The mass ratio of the water-based epoxy resin to water is 0.1-2.5:

100.

9. An aqueous epoxy sizing agent, characterized by, The water-based epoxy resin sizing agent is prepared by using the preparation method of the water-based epoxy resin sizing agent according to claim 7 or 8; the water-based epoxy resin sizing agent is not stratified after standing at 15-30 DEG C for 1 month, and is not stratified after centrifugation at a rotation speed of 3000 r / min for 30 min.

10. Use of an aqueous epoxy resin sizing agent according to claim 9, characterized in that, The sizing treatment is used for carbon fibers.

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