Carbon fiber sizing agent composition suitable for thermoplastic resin, sized carbon fiber, carbon fiber sizing agent as well as preparation method and application of carbon fiber sizing agent

Abstract

The invention discloses a carbon fiber sizing agent composition suitable for thermoplastic resin, sized carbon fiber, a carbon fiber sizing agent as well as a preparation method and application of the carbon fiber sizing agent, belongs to the technical field of carbon fiber sizing agents, and solves the problem that a sizing agent in the prior art cannot meet excellent mechanical properties and high temperature resistance at the same time. The composition is prepared from the following components in parts by weight: 15 to 35 parts of modified polyaryletherketone resin matrix, 0.3 to 2 parts of neutralizer, 1 to 3 parts of emulsifier, 1.5 to 3 parts of defoaming agent and 57 to 80 parts of deionized water. The sizing agent containing the composition has good wettability and film-forming property on the surface of the carbon fiber, and meanwhile, the sizing agent is matched with other components with specific contents in the composition, so that the carbon fiber sizing agent containing the carbon fiber sizing agent composition has excellent heat resistance, can bear processing at the high temperature of 350 DEG C or above, and has good application prospects. And the composite material containing the sizing agent has excellent interlaminar shear strength.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber sizing agents, and particularly to a carbon fiber sizing agent composition suitable for thermoplastic resins, sized carbon fibers, carbon fiber sizing agents, their preparation methods and applications. Background Technology

[0002] Carbon fiber is a brittle material, requiring sizing during production to improve its wear resistance and bundle structure, while ensuring compatibility and compatibility with the resin matrix. Compared to thermosetting resin-based composites, PEEK resin-based composites have molding temperatures exceeding 350℃, high resin viscosity, and high surface inertness. Traditional epoxy resin-based carbon fiber sizing agents have a decomposition temperature of approximately 250℃, which cannot meet the high-temperature requirements for PEEK resin molding. Furthermore, the functional groups of epoxy resin cannot chemically react with PEEK, resulting in poor resin compatibility. Using epoxy resin-sizing for carbon fiber reinforced PEEK resin-based composites will lead to sizing agent decomposition and failure during high-temperature molding, resulting in weak interfacial strength in the molded composite. Therefore, developing carbon fiber sizing agents suitable for PEEK thermoplastic resin is extremely important and has been a research hotspot in recent years.

[0003] CN107383423A discloses a cyano-containing thermoplastic sizing agent for carbon fiber, its preparation method, and its application method. The method uses cyano-containing polyarylene ether resin as the main sizing agent to prepare the thermoplastic sizing agent. The sized carbon fiber has higher temperature resistance and improved interfacial shear strength between carbon fiber and thermoplastic resin. However, it does not reflect the mechanical properties of the sized carbon fiber. Furthermore, the method uses a solvent process, which is costly and poses environmental pollution and production safety hazards.

[0004] CN114960206A discloses a high-temperature resistant, water-soluble thermoplastic sizing agent for carbon fiber, its preparation method, and its application. The sizing agent exhibits a 5% mass loss at 440℃ and good temperature resistance. However, the interlaminar shear strength of its composite material is only 60MPa, which greatly limits its application range.

[0005] CN107385918A discloses an emulsion-type thermoplastic sizing agent for carbon fiber and its preparation method. A polyarylene ether containing a phenolphthalein structure with high temperature resistance is selected as the main sizing resin to prepare an emulsion-type thermoplastic sizing agent for carbon fiber. The interlaminar shear strength of the composite material can reach more than 80 MPa, but the temperature resistance is low, which limits its wide application in thermoplastic resins with high molding temperatures.

[0006] As can be seen from the above, existing carbon fiber sizing agents for thermoplastic resins cannot simultaneously meet the requirements of excellent mechanical properties and high-temperature resistance. In particular, they suffer from problems such as low interlaminar shear strength of composite materials, which greatly limits the application range of thermoplastic resin-based composite materials with high molding temperatures. Summary of the Invention

[0007] In view of the above, the present invention aims to provide a carbon fiber sizing agent composition, a carbon fiber sizing agent and its preparation method and application, sized carbon fiber and its application, to solve at least one of the following problems: (1) In the prior art, it is impossible to simultaneously guarantee the high temperature resistance of the carbon fiber sizing agent and the interlaminar shear strength of the composite material containing the carbon fiber sizing agent; (2) The carbon fiber sizing agent has poor stability and is prone to failure; (3) The preparation process of the carbon fiber sizing agent is complicated, costly and polluting, and poses safety problems.

[0008] The objective of this invention is mainly achieved through the following technical solutions:

[0009] The first aspect of the present invention provides a carbon fiber sizing agent composition, wherein, by weight, the sizing agent comprises: 15-35 parts by weight of a modified polyaryletherketone resin matrix, 0.3-2 parts by weight of a neutralizer, 1-3 parts by weight of an emulsifier, 1.5-3 parts by weight of a defoamer, and 57-80 parts by weight of deionized water.

[0010] Furthermore, the modified polyaryletherketone resin matrix is ​​selected from at least two polymers having the structures shown in Formula A, Formula B and Formula C;

[0011]

[0012] Further, in formula A, m and n are the average degree of polymerization, m≥0, n=1-50, M1 and M2 are each independently selected from alkali metals or alkaline earth metals, and R1, R2, R3 and R4 are each independently selected from C1-C4 alkyl groups.

[0013] Furthermore, in Equation B, m' and n' are the average degree of polymerization, m'≥0, n'=1-50, and z takes integers from 0 to 4.

[0014] Furthermore, in equation C, p is the average degree of polymerization, p = 1-10.

[0015] Furthermore, the neutralizing agent is selected from at least one of glycine, triethylamine, diethanolamine, triethanolamine, and dimethylethanolamine.

[0016] Furthermore, the emulsifier is at least one of a cationic surfactant, anionic surfactant, or nonionic surfactant.

[0017] Furthermore, the defoamer includes at least one of polyoxypropylene glycerol ether, polyoxyethylene polyoxypropylene ether, and methyl stearate.

[0018] A second aspect of the present invention provides a method for preparing a carbon fiber sizing agent, the method comprising:

[0019] S1. Dissolve the modified polyarylether ketone resin matrix in an organic solvent, add emulsifier and neutralizer, and stir for the first time to form an oil phase;

[0020] S2. Add the defoamer to the deionized water and stir for the second time to obtain the modified deionized water;

[0021] S3. Under the third stirring, the modified deionized water described in step S2 is slowly added dropwise to the oil phase in step S1 and mixed evenly to obtain the carbon fiber sizing agent.

[0022] Furthermore, the modified polyaryletherketone resin matrix is ​​selected from at least two polymers having the structures shown in Formula A, Formula B and Formula C;

[0023]

[0024] Further, in formula A, m and n are the average degree of polymerization, m≥0, n=1-50, M1 and M2 are each independently selected from alkali metals or alkaline earth metals, and R1, R2, R3 and R4 are each independently selected from C1-C4 alkyl groups.

[0025] Furthermore, in Equation B, m' and n' are the average degree of polymerization, m'≥0, n'=1-50, and z takes integers from 0 to 4.

[0026] Furthermore, in equation C, p is the average degree of polymerization, p = 1-10.

[0027] Furthermore, the neutralizing agent is selected from at least one of glycine, triethylamine, diethanolamine, triethanolamine, and dimethylethanolamine.

[0028] Furthermore, the emulsifier is at least one of a cationic surfactant, anionic surfactant, or nonionic surfactant.

[0029] Furthermore, the mass ratio of the modified polyaryletherketone resin matrix, emulsifier, neutralizer, and defoamer is 5-15:0.3-2:1-3:1.5-3.

[0030] Furthermore, the defoamer in the modified deionized water has a mass fraction of 2-4.5%.

[0031] Furthermore, in the sizing agent, the concentration of the polyaryletherketone resin matrix is ​​15-35 wt%.

[0032] Further, in step S1, the operating conditions for the first stirring include: a stirring temperature of 50-90℃, a stirring rate of 300-600 r / min, and a stirring time of 80 min-120 min.

[0033] Further, in step S2, the conditions for the second stirring include: a stirring temperature of 60-90℃, a stirring rate of 100-400 r / min, and a stirring time of 10 min-20 min.

[0034] Furthermore, in step S3, the dropping rate of the modified deionized water is 0.5-5 mL / min, and the dropping time is 30-90 min.

[0035] Furthermore, the conditions for the third stirring include: a stirring temperature of 50-80℃, a stirring rate of 1000-1800 r / min, and a stirring time of 10-20 min.

[0036] A third aspect of the present invention provides a carbon fiber sizing agent prepared by the preparation method described in the second aspect of the present invention.

[0037] A fourth aspect of the present invention provides a sized carbon fiber, the sized carbon fiber comprising carbon fiber and the carbon fiber sizing agent described in the third aspect of the present invention.

[0038] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0039] (1) The carbon fiber sizing agent composition provided by the present invention contains a specific amount of modified polyaryletherketone resin matrix, which has good water solubility and can improve its wettability and film-forming properties on the carbon fiber surface. At the same time, in combination with other components in a specific amount in the composition, the carbon fiber sizing agent containing the carbon fiber sizing agent composition has excellent heat resistance and can withstand high temperature (above 350°C) processing, ensuring that the sizing agent does not fail in the composite material molding process.

[0040] (2) The modified polyaryletherketone resin matrix contained in the carbon fiber sizing agent composition provided by the present invention has a similar molecular structure to the PEEK (polyether ether ketone) resin matrix, which is beneficial to the good compatibility and interlocking force between the sized carbon fiber and the PEEK resin. At the same time, it synergistically enhances the other components in the composition, significantly improving the interlaminar shear strength of the carbon fiber composite material, specifically, not less than 65 MPa, effectively improving its interfacial properties.

[0041] (3) The carbon fiber sizing agent preparation method provided by the present invention adopts a water-soluble emulsion process, which greatly reduces the use and volatilization of organic solvents and avoids the environmental pollution and safety hazards caused by the volatilization of a large amount of harmful solvents that may be generated by the traditional solvent-based sizing agent process.

[0042] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of what is particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0043] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0044] Figure 1 This is a droplet size distribution diagram of the carbon fiber sizing agent A1 prepared in Example 1 of the present invention;

[0045] Figure 2 Thermogravimetric curve of carbon fiber sizing agent A1 prepared in Example 1 of this invention;

[0046] Figure 3 The image shows the appearance of carbon fiber sizing agent A1 prepared in Example 1 of this invention after standing for 183 days.

[0047] Figure 4 The image shows the surface morphology of carbon fibers after sizing, prepared using the carbon fiber sizing agent prepared in Example 1 of this invention.

[0048] Figure 5 This is a scanning electron microscope image of the cross-section of the carbon fiber composite material containing the carbon fiber sizing agent prepared in Preparation Example 1 of the present invention. Detailed Implementation

[0049] The preferred preparation examples of the present invention will be described in detail below with reference to the accompanying drawings, which constitute a part of the present invention and, together with the preparation examples of the present invention, serve to illustrate the principles of the present invention.

[0050] The first aspect of the present invention provides a carbon fiber sizing agent composition, wherein, by weight, the sizing agent comprises: 15-35 parts by weight of a modified polyaryletherketone resin matrix, 0.3-2 parts by weight of a neutralizer, 1-3 parts by weight of an emulsifier, 1.5-3 parts by weight of a defoamer, and 57-80 parts by weight of deionized water.

[0051] In this invention, the composition contains a specific amount of modified polyaryletherketone resin matrix, which makes the carbon fiber sizing agent prepared from the composition have good water solubility and can exhibit good wettability and film-forming properties on the carbon fiber surface during the sizing process. At the same time, the other components contained in the composition can synergistically enhance the effect with the aforementioned specific amount of modified polyaryletherketone resin matrix, so that the carbon fiber sizing agent containing the carbon fiber sizing agent composition has excellent heat resistance and can withstand high temperature (above 350°C) processing, ensuring that the sizing agent does not fail in the composite material molding process.

[0052] It is understood that the sum of the contents of each component in the above composition is 100%.

[0053] In this invention, the inventors discovered through extensive research that only when the content of the modified polyaryletherketone resin matrix is ​​between 15 and 35 parts by weight can it synergistically interact with other components in specific amounts within the composition, ensuring the long-term storage stability of the sizing agent system prepared from this composition. If the content is less than 15 parts by weight, the effective component is too low, affecting the efficiency of subsequent preparations; if it is greater than 35 parts by weight, the system is prone to demulsification, affecting the storage stability of the sizing agent.

[0054] Specifically, the modified polyaryletherketone resin matrix comprises 15 parts by weight, 15.1 parts by weight, 15.2 parts by weight, 15.3 parts by weight, 15.4 parts by weight, 15.5 parts by weight, 15.8 parts by weight, 16 parts by weight, 16.5 parts by weight, 17 parts by weight, 17.5 parts by weight, 18 parts by weight, 18.5 parts by weight, 19 parts by weight, 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, and 25 parts by weight. The amounts are 25.5 parts by weight, 26 parts by weight, 26.5 parts by weight, 27 parts by weight, 27.5 parts by weight, 28 parts by weight, 28.5 parts by weight, 29 parts by weight, 29.5 parts by weight, 30 parts by weight, 30.5 parts by weight, 31 parts by weight, 31.5 parts by weight, 32 parts by weight, 32.5 parts by weight, 33 parts by weight, 34 parts by weight, 35 parts by weight, and any two of the above values, preferably 23-35 parts by weight.

[0055] Similarly, in the above-mentioned carbon fiber sizing agent composition, when the neutralizer is 0.3-2 parts by weight, the emulsifier is 1-3 parts by weight, the defoamer is 1.5-3 parts by weight, and the deionized water is 57-80 parts by weight, it can work synergistically with 15-35 parts by weight of the modified polyaryletherketone resin matrix to exert the best performance of each component.

[0056] Specifically, the content of the neutralizing agent is 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1 part by weight, 1.2 parts by weight, 1.5 parts by weight, 1.8 parts by weight, 2 parts by weight, and any two of the above values, preferably 0.4-1.5 parts by weight.

[0057] Specifically, the content of the emulsifier is 1 part by weight, 1.2 parts by weight, 1.5 parts by weight, 1.6 parts by weight, 1.8 parts by weight, 2 parts by weight, 2.1 parts by weight, 2.3 parts by weight, 2.5 parts by weight, 2.8 parts by weight, 3 parts by weight, and any two of the above values, preferably 1.8-2.8 parts by weight.

[0058] Specifically, the content of the defoamer is 1.5 parts by weight, 1.6 parts by weight, 1.8 parts by weight, 2 parts by weight, 2.1 parts by weight, 2.3 parts by weight, 2.5 parts by weight, 2.8 parts by weight, 3 parts by weight, and any two of the above values, preferably 1.5-2.1 parts by weight.

[0059] Specifically, the content of the deionized water is 57 parts by weight, 60 parts by weight, 63 parts by weight, 65 parts by weight, 68 parts by weight, 70 parts by weight, 73 parts by weight, 78 parts by weight, 80 parts by weight, or any two of the above values, preferably 57-68 parts by weight.

[0060] According to the present invention, the modified polyaryletherketone resin matrix is ​​selected from at least two polymers having the structures shown in Formula A, Formula B and Formula C;

[0061]

[0062]

[0063] Further, in formula A, m and n are the average degree of polymerization, m≥0, n=1-50, M1 and M2 are each independently selected from alkali metals or alkaline earth metals, and R1, R2, R3 and R4 are each independently selected from C1-C4 alkyl groups.

[0064] Furthermore, in Equation B, m' and n' are the average degree of polymerization, m'≥0, n'=1-50, and z takes integers from 0 to 4.

[0065] Furthermore, in equation C, p is the average degree of polymerization, p = 1-10.

[0066] In this invention, because the modified polyaryletherketone resin matrix contains a large number of rigid benzene ring structures, and the sulfonic acid alkali metal or sulfonic acid alkaline earth metal and amino structures contained in the molecular structures of Formula A and Formula B have good water solubility, the sizing agent prepared from the composition containing the modified polyaryletherketone resin matrix has excellent storage stability while improving the temperature resistance of the sizing agent. This avoids the organic solvent pollution, production safety and environmental problems caused by the use of solution-type sizing agents during subsequent carbon fiber sizing, and improves the comprehensive mechanical properties and temperature resistance of the subsequent composite material.

[0067] According to one embodiment of the present invention, the modified polyaryletherketone resin matrix is ​​a polymer with the structure shown in Formula A, and when m≥0 and n=1-50, it can effectively improve the temperature resistance of the subsequently prepared sizing agent and improve the wettability and film-forming properties of the sizing agent and carbon fiber during carbon fiber sizing.

[0068] According to a preferred embodiment of the present invention, the modified polyaryletherketone resin matrix is ​​a polymer with the structure shown in Formula A, where m = 1-10, n = 30-50, M1 and M2 are each independently Na, K, and Ca, and R1, R2, R3, and R4 are each independently selected from methyl or ethyl, preferably methyl.

[0069] It is understandable that M1 and M2 can be the same or different, but it is preferable that they are the same.

[0070] According to one embodiment of the present invention, the modified polyaryletherketone resin matrix is ​​a polymer with the structure shown in Formula B, and when m'≥0 and n'=1-50, it can effectively improve the temperature resistance of the subsequently prepared sizing agent and improve the wettability and film-forming properties of the sizing agent and carbon fiber during carbon fiber sizing.

[0071] According to a preferred embodiment of the present invention, the modified polyaryletherketone resin matrix is ​​a polymer with the structure shown in Formula B, where m' = 5-10, n' = 20-35, and z is an integer from 0 to 2.

[0072] According to one embodiment of the present invention, the modified polyaryletherketone resin matrix is ​​a polymer with the structure shown in Formula C, and p = 3-7 can effectively improve the compatibility between the sizing agent and the thermoplastic resin matrix.

[0073] In this invention, the inventors discovered that only when the modified polyaryletherketone resin matrix is ​​selected from at least two of the polymers having the structures shown in Formula A, Formula B and Formula C can it possess high temperature resistance, good film-forming properties and resin compatibility. If only one is selected, it will affect the overall performance of the sizing agent.

[0074] According to a particularly preferred embodiment of the present invention, when the modified polyaryletherketone resin matrix is ​​selected from polymers with the structure shown in Formula A and polymers with the structure shown in Formula C, and m = 2-8, n = 30-46, M1 and M2 are each independently Na, R1, R2, R3 and R4 are each independently selected from methyl, and p = 3-7.

[0075] Furthermore, when the mass ratio of the polymer with structure A to the polymer with structure C is 6-1:1, the sizing agent can improve the high-temperature resistance of the composite material while having good resin compatibility.

[0076] To achieve better technical results, the mass ratio of the polymer structure shown in Formula A to the polymer structure shown in Formula C is 4-6:1.

[0077] According to a particularly preferred embodiment of the present invention, when the modified polyaryletherketone resin matrix is ​​selected from the polymers with the structure shown in Formula B and the polymers with the structure shown in Formula C, and m' = 5-8, n' = 25-35, z is 0, and p = 3-7.

[0078] Furthermore, when the mass ratio of the polymer shown in Formula B to the polymer shown in Formula C is 6-1:1, the sizing agent can form a film on a carbon fiber surface with good properties and improve the high-temperature resistance of the composite material.

[0079] To achieve better technical results, the mass ratio of the polymer structure shown in Formula B to the polymer structure shown in Formula C is 4-6:1.

[0080] According to the present invention, the neutralizing agent is selected from at least one of aminoacetic acid, triethylamine, diethanolamine, triethanolamine and dimethylethanolamine, taking into account the synergistic effect with the above-mentioned modified polyaryletherketone resin matrix.

[0081] According to the present invention, the emulsifier is at least one of a cationic surfactant, anionic surfactant, or nonionic surfactant.

[0082] Specifically, the cationic surfactant includes hexadecyltrimethylammonium bromide, dodecyltrimethylammonium chloride, and tetradecyltrimethylammonium chloride, etc.

[0083] Specifically, the anionic surfactants include sodium dodecylbenzenesulfonate, sodium hexadecyl sulfonate, sodium dodecyl sulfate, and sodium lauryl sulfate, etc.

[0084] Specifically, the nonionic surfactants include Tween 80, Span 20, and polyethylene glycol stearate, etc.

[0085] In one possible design, the emulsifier is two or three of a cationic surfactant, anionic surfactant, or nonionic surfactant. For example, the emulsifier is anionic surfactant and nonionic surfactant in a mass ratio of 2-3:1.

[0086] Furthermore, to achieve better technical results, the emulsifier is preferably a mixture of sodium dodecylbenzenesulfonate and Tween 80. Preferably, the mass ratio of sodium dodecylbenzenesulfonate to Tween 80 is 2-3:1.

[0087] According to the present invention, the defoamer includes at least one of polyoxypropylene glycerol ether, polyoxyethylene polyoxypropylene ether, and methyl stearate.

[0088] In this invention, the neutralizer, emulsifier and defoamer are selected from the aforementioned categories. When their respective dosages are met, they can synergistically cooperate with a specific dosage of modified polyaryletherketone resin matrix to jointly improve the temperature resistance of the carbon fiber sizing agent prepared by the composition, while also improving the wettability and film-forming properties between the carbon fiber sizing agent and the carbon fiber.

[0089] A second aspect of the present invention provides a method for preparing a carbon fiber sizing agent, the method comprising:

[0090] S1. Dissolve the modified polyarylether ketone resin matrix in an organic solvent, add emulsifier and neutralizer, and stir for the first time to form an oil phase;

[0091] S2. Add the defoamer to the deionized water and stir for the second time to obtain the modified deionized water;

[0092] S3. Under the third stirring, the modified deionized water described in step S2 is slowly added dropwise to the oil phase in step S1 and mixed evenly to obtain the carbon fiber sizing agent.

[0093] In this invention, a modified polyaryletherketone resin matrix, emulsifier, and neutralizer are first mixed to form an oil phase. Then, a defoamer is added to deionized water to prepare modified deionized water. The defoamer can eliminate any air bubbles that may be present in the water beforehand and inhibit foam formation during subsequent mixing. If all components are mixed simultaneously, the foam will form a network structure, requiring a higher concentration of defoamer to penetrate the foam layer, which may affect the emulsion uniformity. By pre-dispersing the oil phase and pre-defoaming the aqueous phase, the emulsifier and the modified polyaryletherketone resin matrix synergistically enhance each other, forming a stable colloidal structure. This solves the dispersion problem of polyaryletherketone resin in aqueous systems and avoids the instability of sizing agents.

[0094] In this invention, the organic solvent includes CHCl3, dimethyl sulfoxide (DMSO), or tetrahydrofuran (THF), etc.

[0095] Consistent with the first aspect of the present invention, the modified polyaryletherketone resin matrix is ​​selected from at least two polymers having the structures shown in Formula A, Formula B and Formula C;

[0096]

[0097]

[0098] Further, in formula A, m and n are the average degree of polymerization, m≥0, n=1-50, M1 and M2 are each independently selected from alkali metals or alkaline earth metals, and R1, R2, R3 and R4 are each independently selected from C1-C4 alkyl groups.

[0099] Furthermore, in Equation B, m' and n' are the average degree of polymerization, m'≥0, n'=1-50, and z takes integers from 0 to 4.

[0100] Furthermore, in equation C, p is the average degree of polymerization, p = 1-10.

[0101] In this invention, the modified polyaryletherketone resin matrix satisfies the above-mentioned structure, contains a large number of rigid benzene ring structures, and has the characteristics of high temperature resistance. Moreover, the sulfonic acid alkali metal or sulfonic acid alkaline earth metal and amino structures contained in the molecular structures of Formula A and Formula B have good water solubility. The sizing agent prepared from the composition containing the modified polyaryletherketone resin matrix has excellent storage stability and improves the temperature resistance of the sizing agent. This avoids the organic solvent pollution, production safety and environmental problems caused by the use of solution-type sizing agents in subsequent carbon fiber sizing, and improves the mechanical properties and temperature resistance of the subsequently obtained composite material.

[0102] According to one embodiment of the present invention, the modified polyaryletherketone resin matrix is ​​a polymer with the structure shown in Formula A, and when m≥0 and n=1-50, it can effectively improve the temperature resistance of the subsequently prepared sizing agent and improve the wettability and film-forming properties of the sizing agent and carbon fiber during carbon fiber sizing.

[0103] According to a preferred embodiment of the present invention, the modified polyaryletherketone resin matrix is ​​a polymer with the structure shown in Formula A, where m = 1-10, n = 30-50, M1 and M2 are each independently Na, K, and Ca, and R1, R2, R3, and R4 are each independently selected from methyl or ethyl, preferably methyl.

[0104] It is understandable that M1 and M2 can be the same or different, but it is preferable that they are the same.

[0105] According to one embodiment of the present invention, the modified polyaryletherketone resin matrix is ​​a polymer with the structure shown in Formula B, and when m'≥0 and n'=1-50, it can effectively improve the temperature resistance of the subsequently prepared sizing agent and improve the wettability and film-forming properties of the sizing agent and carbon fiber during carbon fiber sizing.

[0106] According to a preferred embodiment of the present invention, the modified polyaryletherketone resin matrix is ​​a polymer with the structure shown in Formula B, where m' = 5-10, n' = 20-35, and z is an integer from 0 to 2.

[0107] According to one embodiment of the present invention, the modified polyaryletherketone resin matrix is ​​a polymer with the structure shown in Formula C, p = 3-7, which can effectively improve the compatibility between the sizing agent and the thermoplastic resin matrix.

[0108] In this invention, the inventors discovered that only when the modified polyaryletherketone resin matrix is ​​selected from at least two polymers having the structures shown in Formulas A, B, and C can it simultaneously possess high temperature resistance, good film-forming properties, and resin compatibility. Selecting only one polymer will affect the overall performance of the sizing agent.

[0109] According to a particularly preferred embodiment of the present invention, when the modified polyaryletherketone resin matrix is ​​selected from polymers with the structure shown in Formula A and polymers with the structure shown in Formula C, and m = 2-8, n = 30-46, M1 and M2 are each independently Na, R1, R2, R3 and R4 are each independently selected from methyl, and p = 3-7.

[0110] Furthermore, when the mass ratio of the polymer with structure A to the polymer with structure C is 6-1:1, the sizing agent can improve the high-temperature resistance of the composite material while having good resin compatibility.

[0111] To achieve better technical results, the mass ratio of the polymer structure shown in Formula A to the polymer structure shown in Formula C is 4-6:1.

[0112] According to a particularly preferred embodiment of the present invention, when the modified polyaryletherketone resin matrix is ​​selected from the polymers with the structure shown in Formula B and the polymers with the structure shown in Formula C, and m' = 5-8, n' = 25-35, z is 0, and p = 3-7.

[0113] Furthermore, when the mass ratio of the polymer shown in Formula B to the polymer shown in Formula C is 6-1:1, the sizing agent can form a film on a carbon fiber surface with good properties and improve the high-temperature resistance of the composite material.

[0114] To achieve better technical results, the mass ratio of the polymer structure shown in Formula B to the polymer structure shown in Formula C is 4-6:1.

[0115] According to the present invention, the neutralizing agent is selected from at least one of aminoacetic acid, triethylamine, diethanolamine, triethanolamine and dimethylethanolamine, taking into account the synergistic effect with the above-mentioned modified polyaryletherketone resin matrix.

[0116] According to the present invention, the emulsifier is at least one of a cationic surfactant, anionic surfactant, or nonionic surfactant.

[0117] Specifically, the cationic surfactant includes hexadecyltrimethylammonium bromide, dodecyltrimethylammonium chloride, and tetradecyltrimethylammonium chloride, etc.

[0118] Specifically, the anionic surfactants include sodium dodecylbenzenesulfonate, sodium hexadecyl sulfonate, sodium dodecyl sulfate, and sodium lauryl sulfate, etc.

[0119] Specifically, the nonionic surfactants include Tween 80, Span 20, and polyethylene glycol stearate, etc.

[0120] Furthermore, to achieve better technical results, the emulsifier is preferably a mixture of sodium dodecylbenzenesulfonate and Tween 80. Preferably, the mass ratio of sodium dodecylbenzenesulfonate to Tween 80 is 2-3:1.

[0121] According to the present invention, the defoamer includes at least one of polyoxypropylene glycerol ether, polyoxyethylene polyoxypropylene ether, and methyl stearate.

[0122] Specifically, the polyether polymer is selected from polyethylene glycol, polypropylene glycol, and polyoxyethylene polyoxypropylene glycerol ether, etc.

[0123] According to the present invention, the mass ratio of the modified polyaryletherketone resin matrix, neutralizer, emulsifier and defoamer is 15-35:0.3-2:1-3:1.5-3.

[0124] In this invention, the inventors discovered through extensive research that when the mass ratio of polyaryletherketone resin matrix, emulsifier, neutralizer, and defoamer meets the above-mentioned range, the resulting carbon fiber sizing agent can further exhibit good wettability, improve the long-term storage stability of the carbon fiber sizing agent, and withstand high-temperature processing above 350°C. Consequently, the carbon fiber composite material prepared subsequently exhibits excellent interfacial properties and comprehensive mechanical properties.

[0125] To achieve better technical results, the mass ratio of the modified polyaryletherketone resin matrix, neutralizer, emulsifier and defoamer is 23-35:0.4-1.5:1.8-2.8:1.5-2.1.

[0126] According to the present invention, a defoamer is added to deionized water to obtain modified deionized water, wherein the mass fraction of the defoamer in the modified deionized water is 2-4.5%. When this mass fraction range is met, air bubbles that may exist in the deionized water can be eliminated in advance, and foam formation can be suppressed during subsequent mixing, thereby improving the storage stability, wettability, and film-forming properties of the prepared sizing agent.

[0127] According to the present invention, considering both preparation efficiency and improved storage stability, the concentration of the polyaryletherketone resin matrix in the sizing agent is 15-35 wt%. This ensures the long-term storage stability of the sizing agent emulsion.

[0128] According to one embodiment of the present invention, in step S1, the operating conditions of the first stirring include: stirring temperature of 50-90℃, stirring rate of 300-600r / min, and stirring time of 80min-120min.

[0129] The inventors discovered through research that when the stirring temperature meets the above range, the stability of the carbon fiber sizing agent and a suitable particle size distribution range of the sizing agent can be guaranteed. If it is less than 50℃, the particle size of the sizing agent emulsion will be too large, resulting in poor subsequent carbon fiber sizing and large particles on the surface. If it is greater than 90℃, the stability of the emulsion will decrease and demulsification will easily occur. The preferred temperature is 65-80℃.

[0130] Furthermore, when the above stirring temperature is combined with the above stirring rate and stirring time, the sizing agent emulsion can achieve a particle size distribution within a suitable range and high stability.

[0131] According to one embodiment of the present invention, in step S2, the conditions for the second stirring include: a stirring temperature of 60-90°C, a stirring rate of 100-400 r / min, and a stirring time of 10 min-20 min.

[0132] According to one embodiment of the present invention, considering the need to improve emulsion preparation efficiency, emulsification effect and storage stability, in step S3, the dropping rate of the modified deionized water is 0.5-5 mL / min and the dropping time is 30-90 min.

[0133] In this invention, considering the preparation efficiency and storage stability of the prepared carbon fiber sizing agent, the dropping rate of the modified deionized water is 0.5-5 mL / min. If the dropping rate is less than 0.5 mL / min, the emulsifier will be excessively adsorbed and aggregated at the oil-water interface, resulting in a decrease in the effective concentration of the emulsifier, affecting the emulsification effect, and prolonging the emulsion preparation time, thus reducing production efficiency. If the dropping rate is greater than 5 mL / min, oil droplet aggregation and merging are likely to occur, thereby reducing the stability of the sizing agent. Furthermore, rapid water addition will cause the volume of the aqueous phase in the system to increase rapidly, and the oil phase will be divided into oil droplets of different sizes. During the emulsification process, it is difficult to achieve equilibrium between the aggregation and dispersion of oil droplets, resulting in a wider particle size distribution of the final carbon fiber sizing agent emulsion, which in turn leads to a decrease in the long-term storage stability of the carbon fiber sizing agent.

[0134] In this invention, the particle size distribution range of the carbon fiber sizing agent is 300-1500 nm.

[0135] In this invention, the long-term storage stability of the carbon fiber sizing agent is determined by static observation. If the sizing agent shows no demulsification or sedimentation within one month, it is considered to have good stability. If no demulsification or sedimentation occurs for more than three months, it proves that the carbon fiber sizing agent has excellent long-term storage stability.

[0136] According to one embodiment of the present invention, the conditions for the third stirring include: a stirring temperature of 50-80°C, a stirring rate of 1000-1800 r / min, and a stirring time of 10 min-20 min.

[0137] In this invention, the stirring rate of the third stirring is significantly higher than that of the first stirring, because the higher stirring speed allows the sizing agent components to be mixed more evenly.

[0138] A third aspect of the present invention provides a carbon fiber sizing agent prepared by the preparation method described in the second aspect of the present invention.

[0139] According to the present invention, the average particle size of the carbon fiber sizing agent is 400-1000 nm.

[0140] According to the present invention, the temperature at which the carbon fiber sizing agent loses 5% of its weight is ≥408°C.

[0141] According to the present invention, the viscosity of the carbon fiber sizing agent at 25°C is 1600-4500 mPa·s.

[0142] In this invention, the carbon fiber sizing agent meets the above-mentioned viscosity range, which can improve the wettability between the carbon fiber sizing agent and the carbon fiber.

[0143] A fourth aspect of the present invention provides a sized carbon fiber, the sized carbon fiber comprising carbon fiber and the carbon fiber sizing agent described in the third aspect of the present invention.

[0144] In this invention, the sized carbon fiber comprises the carbon fiber sizing agent described in the third aspect of this invention, thereby giving the sized carbon fiber excellent tensile strength, specifically, the tensile strength of the sized carbon fiber is not less than 5600 MPa.

[0145] In this invention, the preparation method of the sized carbon fiber can be carried out as follows: the carbon fiber sizing agent is placed in the sizing tank, and 12K specification T800H grade carbon fiber tow is passed through the sizing agent in the sizing tank at a speed of 8-10m / min for 50-80s. After that, it is dried in a drying oven at 120-140℃ for 20-30min, and then wound in a winding machine to obtain sized carbon fiber.

[0146] In this invention, the interlaminar shear strength of the carbon fiber composite material containing the carbon fiber sizing agent is 65-91.5 MPa.

[0147] The fifth aspect of the present invention provides the application of the carbon fiber sizing agent described in the third aspect of the present invention or the sizing carbon fiber provided in the fourth aspect of the present invention in carbon fiber composite materials.

[0148] In this invention, the carbon fiber composite material includes the carbon fiber sizing agent described in the third aspect of this invention or the sizing carbon fiber provided in the fourth aspect of this invention, and a resin matrix, wherein the resin matrix is ​​a resin matrix with a processing temperature between 350-380°C, particularly a PEEK resin matrix.

[0149] The advantages of precise control of process parameters in this invention will be demonstrated below through specific preparation examples and comparative preparation examples.

[0150] In the following preparation examples, comparative preparation examples, and application examples, the average particle size of the carbon fiber sizing agent was determined by a particle size analyzer.

[0151] The temperature resistance of carbon fiber sizing agent was determined by TGA thermogravimetric analyzer under nitrogen atmosphere, with the 5wt% weight loss temperature as the temperature resistance index.

[0152] The viscosity of the carbon fiber sizing agent was measured using a rotational viscometer;

[0153] Wettability was characterized by the dynamic contact angle between the sizing agent and the carbon fiber monofilament using a DCAT21 surface / interfacial tensiometer; the specific steps are as follows:

[0154] (1) Place the bare carbon fiber filaments after removing the sizing agent into an oven at 120°C and dry them. Then cut them into 20mm long segments. Randomly select 5 monofilaments and fix them with the clamps of the DCAT21 surface / interfacial tension meter. Maintain a 5mm gap between adjacent carbon fiber monofilaments and cut off the excess part so that the lengths exposed to the clamps are as equal as possible.

[0155] (2) Place the container containing the sizing agent liquid on the lifting platform of the DCAT21 surface / interfacial tension meter, install the clamps that fix the 5 carbon fiber monofilaments in the corresponding positions of the instrument, ensure that the carbon fiber monofilaments are vertical, set the depth of the carbon fiber monofilaments inserted into the sizing agent liquid to be 5mm, and the forward and backward wetting speeds are both 0.03mm / s.

[0156] (3) Start the measurement program. The DCAT21 surface / interface tension meter automatically controls the lifting platform to rise, so that the liquid surface gradually approaches the carbon fiber monofilament. When the carbon fiber monofilament comes into contact with the sizing agent liquid surface, the instrument's force sensor measures the wetting force based on the immersion depth and combines it with the carbon fiber monofilament diameter data. During the upward movement of the sample stage, the dynamic contact angle between the sizing agent and the carbon fiber monofilament in the wetting stage can be measured.

[0157] Film-forming properties were characterized by the surface morphology of carbon fibers after sizing, using a scanning electron microscope (SEM).

[0158] The tensile strength of sized carbon fiber was determined according to GB / T 26749 standard;

[0159] The interlaminar shear strength of carbon fiber composites was determined using a universal testing machine with a three-point bending method according to ASTM D2344.

[0160] The following preparation examples illustrate the preparation of carbon fiber sizing agents using carbon fiber sizing agent compositions. Preparation Example 1

[0161] S1: The polymer with the structure of formula A (m is 8, n is 46, M1 and M2 are Na, R1, R2, R3 and R4 are methyl) and the polymer with the structure of formula C (p is 7) are dissolved in CHCl3 organic solvent at a weight ratio of 1:1. Then, emulsifier and neutralizer are added to adjust the pH to 7. After that, the mixture is stirred at 80℃ and 600r / min for 100min to form an oil phase.

[0162] S2: Add the defoamer to the deionized water and stir for 15 minutes at 60℃ and 200r / min to obtain the modified deionized water;

[0163] S3: Add the modified deionized water obtained in S2 to the oil phase of S1 and stir. The dropping rate is 2.2 mL / min, the stirring rate is 1260 r / min, and the dropping time is 55 min to obtain carbon fiber sizing agent A1.

[0164] The components include, by weight, the polymers of formula A (denoted as formula A in Table 1) and formula C (denoted as formula C in Table 1), the total weight of the modified polyaryletherketone resin matrix, the emulsifier (Tween 80), the neutralizer (glycine), the defoamer (polyoxypropylene glycerol ether), and the deionized water, as well as, the concentration of the modified polyaryletherketone resin matrix in the sizing agent (denoted as concentration in Table 1). a See Table 1 for details.

[0165] The average particle size, temperature resistance, and viscosity of carbon fiber sizing agent A1 are detailed in Table 2.

[0166] Preparation Examples 2-16, Comparative Preparation Examples 1-4

[0167] The method of preparation example 1 is followed, except that carbon fiber sizing agents A2-A16 are prepared according to the formulations in Table 1.

[0168] In Preparation Example 11, Formula A was replaced with an equal mass of Formula B (the mass ratio of Formula B to Formula C was 6:1). In Formula B, m' was 8 and n' was 35.

[0169] In Preparation Example 12, Formula C was replaced with an equal mass of Formula B (the mass ratio of Formula A to Formula B was 6:1), in Formula B, m' was 8 and n' was 35;

[0170] In preparation example 13, p = 1 in formula C;

[0171] In Preparation Example 14, the emulsifier was a compound of sodium dodecylbenzenesulfonate and Tween 80 in a mass ratio of 2.5:1;

[0172] In preparation example 15, p = 50 in formula C.

[0173] The average particle size, temperature resistance, and viscosity of carbon fiber sizing agents A2-A14 and D1-D4 are detailed in Table 2.

[0174] Table 1

[0175]

[0176] Preparation Example 17

[0177] The method of Preparation Example 6 is the same, except that in step S1, the conditions for the first stirring include stirring at 40°C and 200 r / min for 100 min to form an oil phase.

[0178] Preparation Example 18

[0179] The method of Preparation Example 6 is the same, except that in step S3, the modified deionized water obtained in S2 is added to the oil phase in S1 and stirred. The dropping rate is 5.5 mL / min, the stirring rate is 900 r / min, and the dropping time is 22 min, so as to obtain carbon fiber sizing agent A18.

[0180] Comparative preparation example 5

[0181] The polymer with the structure of Formula A (same as in Preparation Example 6) and the polymer with the structure of Formula C (same as in Preparation Example 6) were dissolved in CHCl3 organic solvent at a weight ratio of 1:1. Then, an emulsifier and a neutralizing agent were added to adjust the pH to 7. Then, an antifoaming agent and deionized water were added. The mixture was then stirred at 80°C and 600 r / min for 100 min to obtain a mixture, which was denoted as D5.

[0182] Testing revealed that the prepared sizing agent exhibited significant foaming and poor emulsion uniformity.

[0183] Table 2

[0184]

[0185]

[0186] The results above show that the particle size distribution of preparations 4-6, 11, 12 and 14 is suitable, the sizing agent has high temperature resistance, the viscosity of the system is low and the dynamic contact angle is small, making them suitable for sizing agents to be applied to fibers.

[0187] Figure 1 To obtain the droplet size distribution diagram of the carbon fiber sizing agent A1 prepared in Example 1, from... Figure 1 As can be seen, the particle size of the sizing agent is concentrated between 300nm and 1500nm, with an average particle size of 697.3nm. The particle size is suitable for the subsequent carbon fiber sizing process.

[0188] Figure 2 To obtain the thermogravimetric analysis (TGA) diagram of the carbon fiber sizing agent A1 prepared in Example 1, from... Figure 2 As can be seen from the data, the temperature at which the sizing agent loses 5 wt% is 408℃, indicating that it has good high-temperature resistance and can meet the processing requirements of composite materials (carbon fiber reinforced thermoplastic PEEK resin-based composite materials).

[0189] Figure 3 The carbon fiber sizing agent A1 prepared in Example 1 was left to stand for more than 6 months. There was basically no demulsification or sedimentation, which shows that the carbon fiber sizing agent prepared by the present invention has excellent storage stability.

[0190] The following application examples illustrate the preparation of carbon fiber composite materials.

[0191] Application Example 1

[0192] a. The carbon fiber sizing agent prepared in Example 1 was placed in a sizing tank. A 12K T800H grade carbon fiber bundle was passed through the sizing agent in the sizing tank at a speed of 8m / min for 50s. After that, it was dried in a drying oven at 130℃ for 20min. The sizing carbon fiber was then wound in a winding machine to obtain sizing carbon fiber. The tensile properties of the obtained sizing carbon fiber were tested according to GB / T26749.

[0193] b. Lay the PEEK resin film on the metal mold, then lay the sized carbon fiber obtained in step a on the PEEK resin film, and place it in a hot press at 350°C for 10 minutes to obtain a single-layer prepreg. The volume ratio of the sized carbon fiber to the PEEK resin film is 3:2.

[0194] c. Lay up 30 layers of the single-layer prepreg from step b, and then place it in a hot press for hot pressing. The hot pressing process is as follows: temperature 350℃, pressure 4MPa, time 40min, to obtain carbon fiber composite material S1.

[0195] Figure 4 The image shows the surface morphology of the sized carbon fiber in Application Example 1. As can be seen from the image, the surface of the sized carbon fiber is uniform, delicate, and smooth, without obvious wrinkles, protrusions, or uneven areas. This indicates that there are no sizing agent particles on the carbon fiber surface, and the sizing agent is uniformly applied to the carbon fiber surface, resulting in good film formation.

[0196] Figure 5 The SEM image of the cross section of the composite material prepared in Example 1 shows that the carbon fiber and the thermoplastic PEEK resin are well bonded together, and there are no defects such as voids at the interface. This indicates that the presence of the sizing agent enhances the compatibility and bonding ability between the carbon fiber and the PEEK resin, thereby improving the interfacial properties of the composite material.

[0197] Application Example 2-18, Comparison with Application Example 1-6

[0198] Following the method of Application Example 1, except that the carbon fiber sizing agent A1 prepared in Preparation Example 1 was replaced with carbon fiber sizing agents A2-A14 prepared in Preparation Examples 2-14, carbon fiber sizing agents D1-D5 prepared in Comparative Preparation Examples 1-5, and epoxy resin sizing agent (domestic No. 4 sizing agent) to prepare carbon fiber composite materials S2-18 and DS1-DS6. During the preparation process, the tensile properties of the sizing carbon fibers prepared in Application Examples 2-18 and Comparative Application Examples 1-6 were tested respectively, and the results are shown in Table 3.

[0199] Table 3

[0200]

[0201]

[0202] The results in Tables 2 and 3 show that the application examples 1-18 that conform to the technical solution of the present invention have good technical effects. The sizing agent has good temperature resistance, specifically, not less than 378°C. At the same time, the composite material containing the sizing agent has good interlaminar shear strength, specifically, not less than 65MPa.

[0203] Furthermore, Application Examples 4-6, 11, 12 and Application Example 14, which satisfy the preferred embodiments of the present invention, achieve significantly better technical effects. The sizing agent obtained is resistant to a high temperature of at least 411°C, and the interlaminar shear strength of the composite material containing the sizing agent is not less than 85.1 MPa and reaches a maximum of 91.5 MPa.

[0204] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A carbon fiber sizing agent composition, characterized in that, The sizing agent comprises, by weight, 15-35 parts of modified polyaryletherketone resin matrix, 0.3-2 parts of neutralizer, 1-3 parts of emulsifier, 1.5-3 parts of defoamer and 57-80 parts of deionized water.

2. The carbon fiber sizing agent composition according to claim 1, characterized in that, The modified polyaryletherketone resin matrix is ​​selected from at least two polymers having the structures shown in Formula A, Formula B and Formula C; In Formula A, m and n are the average degree of polymerization, m≥0, n=1-50, M1 and M2 are each independently selected from alkali metals or alkaline earth metals, and R1, R2, R3 and R4 are each independently selected from C1-C4 alkyl groups. In Equation B, m' and n' are the average degree of polymerization, m' ≥ 0, n' = 1-50, and z takes integers from 0 to 4; In formula C, p is the average degree of polymerization, p = 1-10.

3. The carbon fiber sizing agent composition according to claim 1 or 2, characterized in that, The neutralizing agent is selected from at least one of glycine, triethylamine, diethanolamine, triethanolamine, and dimethylethanolamine; And / or, the emulsifier is at least one of a cationic surfactant, anionic surfactant, or nonionic surfactant; And / or, the defoamer includes at least one of polyoxypropylene glycerol ether, polyoxyethylene polyoxypropylene ether, and methyl stearate.

4. A method for preparing a carbon fiber sizing agent, characterized in that, The method includes: S1. Dissolve the modified polyarylether ketone resin matrix in an organic solvent, add emulsifier and neutralizer, and stir for the first time to form an oil phase; S2. Add the defoamer to the deionized water and stir for the second time to obtain the modified deionized water; S3. Under the third stirring, the modified deionized water described in step S2 is slowly added dropwise to the oil phase in step S1 and mixed evenly to obtain the carbon fiber sizing agent.

5. The preparation method according to claim 4, characterized in that, The modified polyaryletherketone resin matrix is ​​selected from at least two polymers having the structures shown in Formula A, Formula B and Formula C; In Formula A, m and n are the average degree of polymerization, m≥0, n=1-50, M1 and M2 are each independently selected from alkali metals or alkaline earth metals, and R1, R2, R3 and R4 are each independently selected from C1-C4 alkyl groups. In Equation B, m' and n' are the average degree of polymerization, m' ≥ 0, n' = 1-50, and z takes integers from 0 to 4; In formula C, p is the average degree of polymerization, p = 1-10; And / or, the neutralizing agent is selected from at least one of glycine, triethylamine, diethanolamine, triethanolamine, and dimethylethanolamine; And / or, the emulsifier is at least one of a cationic surfactant, anionic surfactant, or nonionic surfactant.

6. The preparation method according to claim 4 or 5, characterized in that, The mass ratio of the modified polyaryletherketone resin matrix, neutralizer, emulsifier, and defoamer is 15-35:0.3-2:1-3:1.5-3; And / or, in the modified deionized water, the mass fraction of the defoamer is 2-4.5%; And / or, in the sizing agent, the concentration of the polyaryletherketone resin matrix is ​​15-35 wt%.

7. The preparation method according to claim 4 or 5, characterized in that, In step S1, the operating conditions for the first stirring include: stirring temperature of 50-90℃, stirring speed of 300-600r / min, and stirring time of 80min-120min; And / or, in step S2, the conditions for the second stirring include: a stirring temperature of 60-90℃, a stirring rate of 100-400 r / min, and a stirring time of 10 min-20 min; And / or, in step S3, the dropping rate of the modified deionized water is 0.5-5 mL / min, and the dropping time is 30-90 min; And / or, the conditions for the third stirring include: a stirring temperature of 50-80℃, a stirring rate of 1000-1800 r / min, and a stirring time of 10 min-20 min.

8. A carbon fiber sizing agent prepared by any one of claims 4-7.

9. A type of sized carbon fiber, characterized in that, The sizing carbon fiber comprises carbon fiber and the carbon fiber sizing agent as described in claim 8.

10. The application of the carbon fiber sizing agent of claim 8 or the sizing carbon fiber of claim 9 in carbon fiber composite materials.

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