Sizing agent, modified large tow carbon fiber and preparation method thereof

Abstract

The invention discloses a sizing agent, a modified large tow carbon fiber and a preparation method thereof. The raw material composition of the sizing agent of the present invention includes bisphenol F epoxy resin, polyethyleneimine, a surfactant and water; wherein the content of the bisphenol F epoxy resin is 40-80%; the content of the polyethyleneimine is 10-50%; the content of the surfactant is 5-15%; the percentage is the percentage of the sum of the mass of the bisphenol F epoxy resin, the polyethyleneimine and the surfactant. The sizing agent of the present invention has a simple composition, a small content of surfactant, good stability, and can effectively improve the moisture resistance of large tow carbon fiber. The modified large tow carbon fiber obtained using the sizing agent of the present invention has good bundling, low hair content, and excellent wear resistance.

Description

Technical Field

[0001] The invention relates to a sizing agent, modified large-tow carbon fiber and a preparation method thereof. Background Art

[0002] Carbon fiber and composite materials have developed rapidly in recent years. They are one of the key basic materials for promoting the upgrading of my country's aerospace and national defense military equipment. They also have broad application prospects in civil engineering, construction, new energy vehicles and other civilian fields. With the gradual maturity of carbon fiber industry technology and the actual needs of the market, the application demand for large-tow carbon fiber is more urgent. Compared with small-tow carbon fiber, 48K and above large-tow carbon fiber has higher production efficiency, higher processing efficiency in the preparation of composite materials, and significantly reduced overall cost. However, due to the sharp increase in the number of monofilaments in the tow, it is easy to cause many problems such as uneven carbonization, large fluctuations in CV value, and a large amount of hair. Large-tow fibers are often used in high-pressure gas cylinders, industrial pipelines and other fields. The winding process under high tension is adopted. If there are too many carbon fiber hairs and the friction between the passing device is too large, the fiber will be entangled and broken, resulting in strength loss and composite defects, which seriously affects work efficiency and product reliability. Therefore, fiber fuzziness and wear resistance have become important technical issues that limit the large-scale application of large-tow carbon fiber.

[0003] Carbon fiber sizing is one of the commonly used methods to improve the processing performance of carbon fiber. Patent 202210818663.9 discloses a method for preparing a water-soluble polyimide sizing agent for large-tow carbon fiber precursor. Diamine and dianhydride monomers with isomeric structures are selected as synthetic monomers, and the polyamic acid group is modified by an aqueous solution of triethylamine or N,N-dimethylethanolamine to prepare a water-soluble polyimide sizing agent. However, the preparation process of this method is complicated and the processing time is too long. It is difficult to meet the requirements of safety, economy and continuous production, and there is no report on the improvement of the process performance of sizing large-tow carbon fiber.

[0004] Patent 202210671676.8 discloses a water-based epoxy resin sizing agent for large-tow carbon fiber and its preparation method, including modified epoxy resin, water-based polyurethane, neutralizer, defoamer, leveling agent, sizing agent, wetting agent, deionized water, etc., which can improve the sizing and processing performance of large-tow fibers, but the preparation of modified epoxy resin has high requirements and requires a large amount of organic solvents, which makes engineering applications difficult.

[0005] Therefore, there is an urgent need to provide a sizing agent, a modified large-tow carbon fiber and a preparation method thereof, which can reduce the use of organic solvents and improve the sizing and processing properties of large-tow fibers. Summary of the invention

[0006] In order to overcome the defects of the sizing agent in the prior art that the formula is complicated, the preparation process of the sizing agent is complicated, and a large amount of organic solvent is consumed, the present invention discloses a sizing agent, a modified large tow carbon fiber and a preparation method thereof. The sizing agent of the present invention has a simple composition, a small content of surfactant, good stability, and can effectively improve the moisture resistance of the modified large tow carbon fiber. The sizing agent of the present invention is simple to prepare and does not require an organic solvent. Under such a premise, the modified large tow carbon fiber prepared using the sizing agent of the present invention has good bundling, low hair content, and excellent wear resistance.

[0007] The inventors of the present invention have found that by using a sizing agent composed of a specific epoxy resin and polyethyleneimine and performing a drying and curing treatment at a specific temperature, the degree of reaction between the sizing agent and the large-tow carbon fiber can be controlled, thereby effectively controlling the fuzziness of the large-tow carbon fiber and improving the wear resistance of the large-tow carbon fiber. In practical applications, the modified large-tow carbon fiber prepared by the sizing agent of the present invention has good compatibility and bonding ability with the composite matrix.

[0008] The present invention provides a sizing agent, the raw material composition of which includes bisphenol F epoxy resin, polyethyleneimine, surfactant and water;

[0009] Wherein, the content of the bisphenol F epoxy resin is 40-80%;

[0010] The content of polyethyleneimine is 10-50%;

[0011] The content of the surfactant is 5-15%; the percentage is the percentage of the sum of the masses of the bisphenol F epoxy resin, the polyethyleneimine and the surfactant.

[0012] In the present invention, the bisphenol F epoxy resin can be a conventional bisphenol F epoxy resin in the art. The bisphenol F epoxy resin is also commonly known as bisphenol F diglycidyl ether, or BPF resin for short, and is prepared by reacting phenol with formaldehyde under acidic catalysis to generate bisphenol F, which is then polycondensed with epichlorohydrin in the presence of sodium hydroxide.

[0013] In the present invention, the epoxy equivalent of the bisphenol F epoxy resin may be 160-1000 g / eq, more preferably 160-500 g / eq, for example 170 g / eq, 180 g / eq or 475 g / eq.

[0014] In the present invention, the content of the bisphenol F epoxy resin is preferably 45-80%, more preferably 45-70%, for example 50%, 60% or 65%.

[0015] In the present invention, the amount of water added can be selected according to actual conditions, and the amount of water added is preferably 20-50%, where the percentage is the total mass percentage of the raw material composition of the sizing agent. When the amount of water added is within the above range, the sizing agent can be stably stored and is also convenient for transportation.

[0016] In the present invention, the sizing agent can be diluted according to actual needs before use, usually diluted to a solid content of 1-5%, that is, the amount of water added to the sizing agent is 95%-99%. The solid content refers to the percentage of the bisphenol F epoxy resin, the polyethyleneimine and the surfactant in the sizing agent to the total mass of the raw material composition of the sizing agent.

[0017] In the present invention, the polyethyleneimine can be conventional polyethyleneimine in the art, preferably polyethyleneimine terminated with ethylenediamine.

[0018] In the present invention, the content of the polyethyleneimine is preferably 20-50%, more preferably 20-40%, for example 30%.

[0019] In the present invention, the weight average molecular weight of the polyethyleneimine may be 500-2500, preferably 800-2000, more preferably 800-1800, for example 1500.

[0020] In the present invention, the surfactant may be a conventional surfactant in the art, preferably one or more of a cationic surfactant, an anionic surfactant and a nonionic surfactant, for example, a nonionic surfactant.

[0021] Wherein, the nonionic surfactant is selected from one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, fatty amine polyoxyethylene ether and block polyoxyethylene-polyoxypropylene ether, preferably fatty alcohol polyoxyethylene ether, more preferably C16-C18 fatty alcohol polyoxyethylene ether.

[0022] Wherein, the general formula of the C16-C18 fatty alcohol polyoxyethylene ether is RO(CH 2 CH 2 O) n H, wherein n is the degree of polymerization, and C16-C18 represents that the carbon chain length of R is 16 to 18. The C16-C18 fatty alcohol polyoxyethylene ether is called leveling agent O or leveling agent O.

[0023] Wherein, the described Peregal O is preferably one or more of Peregal O-8, Peregal O-10, Peregal O-15, Peregal O-20 and Peregal O-30. The 8, 10, 15, 20 or 30 in the described Peregal O corresponds to the polymerization degree n of the polyoxyethylene ether in the general formula of C16-C18 fatty alcohol polyoxyethylene ether.

[0024] In the present invention, the content of the surfactant is preferably 5-10%.

[0025] In a specific embodiment of the present invention, the raw material composition of the sizing agent includes 60% of the bisphenol F epoxy resin, 30% of the polyethyleneimine, 10% of the surfactant and water; the epoxy equivalent of the bisphenol F epoxy resin is 170g / eq; the weight average molecular weight of the polyethyleneimine is 800; and the surfactant is Peregal O-20.

[0026] In a specific embodiment of the present invention, the raw material composition of the sizing agent includes 45% of the bisphenol F epoxy resin, 50% of the polyethyleneimine, 5% of the surfactant and water; the epoxy equivalent of the bisphenol F epoxy resin is 170g / eq; the weight average molecular weight of the polyethyleneimine is 1800; and the surfactant is peregal O-15.

[0027] In a specific embodiment of the present invention, the raw material composition of the sizing agent includes 50% of the bisphenol F epoxy resin, 10% of the polyethyleneimine, 10% of the surfactant and water; the epoxy equivalent of the bisphenol F epoxy resin is 180g / eq; the weight average molecular weight of the polyethyleneimine is 1500; and the surfactant is peregal O-8.

[0028] In a specific embodiment of the present invention, the raw material composition of the sizing agent includes 80% of the bisphenol F epoxy resin, 10% of the polyethyleneimine, 10% of the surfactant and water; the epoxy equivalent of the bisphenol F epoxy resin is 180g / eq; the weight average molecular weight of the polyethyleneimine is 1800; and the surfactant is peregal O-20.

[0029] In a specific embodiment of the present invention, the raw material composition of the sizing agent includes 70% of the bisphenol F epoxy resin, 20% of the polyethyleneimine, 10% of the surfactant and water; the epoxy equivalent of the bisphenol F epoxy resin is 475g / eq; the weight average molecular weight of the polyethyleneimine is 800; and the surfactant is peregal O-10.

[0030] In a specific embodiment of the present invention, the raw material composition of the sizing agent includes 65% of the bisphenol F epoxy resin, 30% of the polyethyleneimine, 15% of the surfactant and water; the epoxy equivalent of the bisphenol F epoxy resin is 475g / eq; the weight average molecular weight of the polyethyleneimine is 1500; and the surfactant is Peregal O-30.

[0031] The present invention also provides a method for preparing a sizing agent, which comprises the following steps: mixing the raw material composition of the sizing agent as mentioned above.

[0032] In the present invention, the method for preparing the sizing agent preferably comprises the following steps: heating a mixture containing the bisphenol F epoxy resin, the polyethyleneimine and the surfactant, and then adding water for emulsification.

[0033] The preparation method of the mixture preferably comprises the following steps: uniformly mixing the bisphenol F epoxy resin, the polyethyleneimine and the surfactant to obtain the mixture.

[0034] The temperature of the heating may be a temperature conventionally used in the art for preparing sizing agents, such as 80°C.

[0035] The emulsification may be carried out by conventional methods in the art, preferably including the following steps: water is gradually dripped into the mixture for emulsification. The degree of emulsification may be selected according to actual conditions.

[0036] In the present invention, stirring can be used during the heating process, and the purpose of the stirring is to make the raw materials mixed uniformly and heated uniformly.

[0037] The present invention also provides a sizing agent, which is prepared by the above-mentioned preparation method of the sizing agent.

[0038] The present invention also provides a method for preparing modified large-tow carbon fiber, which comprises the following steps: sizing and drying and curing the large-tow carbon fiber; the sizing agent used in the sizing is as described above; and the drying and curing temperature is 100-170°C.

[0039] In the present invention, the large-tow carbon fiber generally refers to a carbon fiber bundle having 48,000 or more carbon fibers.

[0040] In the present invention, the number of the large tow carbon fibers is preferably 48K, 50K or 60K.

[0041] In the present invention, the large tow carbon fiber may be conventional in the art, and is preferably polyacrylonitrile-based carbon fiber.

[0042] In a preferred embodiment of the present invention, the large-tow carbon fiber is 48K polyacrylonitrile-based carbon fiber, 50K polyacrylonitrile-based carbon fiber or 60K polyacrylonitrile-based carbon fiber, wherein "48K" means that the number of carbon fibers is 48,000, and "50K" and "60K" are the same.

[0043] Those skilled in the art are aware that sizing refers to the process of applying a sizing agent to the surface of large tow carbon fibers.

[0044] In the present invention, the sizing can be performed by conventional sizing methods in the art, and the sizing method is preferably a dipping method, a transfer method or a spraying method, such as a dipping method.

[0045] The impregnation time and impregnation temperature of the impregnation method may be conventional in the art.

[0046] In the present invention, in the sizing, the amount of the sizing agent can be selected according to actual conditions, preferably 0.3-5%, more preferably 1.0-1.31%, for example 1.05%, 1.10%, 1.13%, 1.15%, or 1.22%, where the percentage is the mass percentage of the sizing agent to the large tow carbon fiber.

[0047] In the present invention, the drying and curing temperature is preferably 120-150°C, such as 135°C.

[0048] In the present invention, the drying and curing time can be selected according to actual conditions.

[0049] In the present invention, the drying and curing can be carried out by conventional drying and curing methods in the art, preferably hot air drying, hot roller drying, infrared drying or microwave drying, such as hot air drying.

[0050] The hot air drying may be carried out using conventional devices in the art, such as a hot air oven.

[0051] The present invention also provides a modified large-tow carbon fiber, which is prepared by the preparation method of the modified large-tow carbon fiber as described above.

[0052] Those skilled in the art are aware that the drying and curing refers to an irreversible change process of the large-tow carbon fiber after sizing at a certain temperature, and the change process usually involves chemical reactions such as condensation, ring closure, addition or catalysis. Therefore, after sizing and drying and curing, the water in the sizing agent will evaporate, and what remains on the surface of the large-tow carbon fiber is the remaining components in the sizing agent other than water. The remaining components will exist in the modified large-tow carbon fiber in two forms, one of which is attached to the modified large-tow carbon fiber by chemically reacting with the large-tow carbon fiber, and the other is not reacting with the large-tow carbon fiber and only coating the surface of the modified large-tow carbon fiber.

[0053] In the present invention, the modified large tow carbon fiber preferably satisfies S 1 -S 2 The value is 0.2-0.6%, preferably 0.3-0.5%;

[0054] Among them, S 1represents the total sizing amount; the total sizing amount refers to the percentage of the total mass of the remaining components of the sizing agent in the modified large tow carbon fiber to the mass of the modified large tow carbon fiber, and the total mass of the remaining components of the sizing agent includes the mass of the remaining components of the sizing agent that react with the large tow carbon fiber and the mass of the remaining components of the sizing agent that do not react with the large tow carbon fiber; S 2 Represents the unreacted sizing amount; the unreacted sizing amount refers to the percentage of the mass of the remaining components of the sizing agent that have not reacted with the large tow carbon fiber in the modified large tow carbon fiber to the mass of the modified large tow carbon fiber.

[0055] In the present invention, the S 1 -S 2 The value of S can reflect the extent of the reaction between the sizing agent and the surface of the large tow carbon fiber. 1 -S 2 If the value of S is too high, it means that the chemical reaction between the sizing agent components and between the sizing agent and the surface of the large tow carbon fiber is excessive, and the obtained modified large tow carbon fiber material will harden, which will be detrimental to the subsequent use of the material. 1 -S 2 The value of is too low, indicating that the degree of chemical reaction between the sizing agent components and between the sizing agent and the surface of the large tow carbon fiber is low. At this time, the sizing agent cannot improve the performance of the large tow carbon fiber. Therefore, it is necessary to control the degree of chemical reaction between the sizing agent components and between the sizing agent and the surface of the large tow carbon fiber, that is, the S 1 -S 2 The value should be controlled within a certain range to ensure that the modified large-tow carbon fiber has better performance.

[0056] In the present invention, the S 1 and S 2 It can be measured by conventional methods in the art. Preferably, the S 1 It is measured by high temperature decomposition method. 2 It is measured using the Soxhlet extraction method. Those skilled in the art know that the high temperature decomposition method can more accurately calculate the total sizing amount in the modified large tow carbon fiber based on the mass change of the test sample before and after thermal decomposition; the Soxhlet extraction method can calculate the unreacted sizing amount in the large tow carbon fiber that has not reacted with the large tow carbon fiber based on the mass change of the test sample before and after extraction, stripping and extraction. On the basis of conforming to the common sense in the field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0057] The reagents and raw materials used in the present invention are commercially available.

[0058] The positive and progressive effects of the present invention are:

[0059] (1) The raw material composition of the sizing agent of the present invention is simple, and the preparation of the sizing agent is also relatively simple. No organic solvent is required, and the raw materials only need to be physically mixed. This is simple and easy to implement, and meets the requirements of the project for environmental protection, economy and continuity.

[0060] (2) The sizing agent prepared by the present invention has stable performance and low surfactant content, and the moisture resistance of the composite material finally prepared is enhanced.

[0061] (3) The modified large-tow carbon fiber prepared by the sizing agent of the present invention has good bundling properties, low fuzz content, and excellent wear resistance, which can meet the requirements of subsequent processing techniques such as weaving, and has excellent bonding properties with the composite matrix in practical applications. DETAILED DESCRIPTION

[0062] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0063] The total sizing amount S in the present invention is 1 , unreacted sizing amount S 2 , hair quantity, abrasion resistance times and interlaminar shear strength are tested using the following methods.

[0064] Total sizing amount S 1 : High temperature decomposition method, for specific determination, please refer to "GBT 29761-2013 Method C for determination of carbon fiber sizing agent content" for determination.

[0065] Unreacted sizing amount S 2 : Soxhlet extraction method, specific determination can be made by referring to "GBT 29761-2013 Method A for determination of carbon fiber sizing agent content".

[0066] Hair amount: The polyurethane hair amount adsorption method is used to make the fiber pass through a polyurethane sponge block under a certain pressure to collect the fiber hair amount within a certain length. The pressure is 200g and the length is 10m. The mass difference before and after the polyurethane sponge is the hair amount of the modified large-tow carbon fiber.

[0067] Abrasion times: The yarn friction method is used to rub the fiber through the surface of a chrome-plated stainless steel roller. The diameter of the steel roller is 3mm and the angle is 120°. The abrasion times when the modified large tow carbon fiber breaks are measured.

[0068] Interlaminar shear strength: Determined in accordance with “JC 20773-1996 Test method for interlaminar shear strength of unidirectional fiber reinforced plastics”.

[0069] Examples 1-6 and Comparative Examples 1-5

[0070] (1) Preparation of sizing agent: bisphenol F epoxy resin, polyethyleneimine and surfactant bisphenol A O were placed in a flask, heated to 80° C., stirred continuously and 4900 g of deionized water was gradually added dropwise. After emulsification, an aqueous emulsion sizing agent was prepared. The specific types and amounts of bisphenol F epoxy resin, polyethyleneimine and bisphenol A O are shown in Table 1.

[0071] (2) Preparation of modified large-tow carbon fiber: The sizing agent prepared in step (1) is transferred to a sizing tank, and the unsized 48K polyacrylonitrile-based carbon fiber is immersed in the above sizing tank for immersion sizing. The sized 48K polyacrylonitrile-based carbon fiber is placed in a hot air oven for drying and curing, and then wound to obtain the modified large-tow carbon fiber. The preparation conditions and related performance test results of the modified large-tow carbon fiber are shown in Table 2.

[0072] Comparative Example 6

[0073] The unsized 48K large tow carbon fiber was impregnated and sized with the commonly used KTM-1 epoxy emulsion sizing agent (bisphenol A epoxy resin type), with a total sizing amount of 1.2%. The drying and curing steps were the same as in Example 1, wherein the drying and curing temperature was 150°C. The relevant performance test results are shown in Table 2.

[0074] Table 1 Specific types and amounts of each component of sizing agent

[0075]

[0076] Table 2 Preparation conditions and related performance test results of modified large tow carbon fiber

[0077]

[0078]

[0079] As shown in Table 2, the amount of hairy fibers in the modified large tow carbon fibers prepared by the sizing agents prepared in Examples 1-6 of the present invention is relatively low, ranging from 2.3 to 4.5 mg; the sizing agents are relatively stable after sizing, and S 1 -S 2 The value is between 0.21-0.53%; the wear resistance is good, the wear times are between 493-618; the interlaminar shear strength is also significantly improved, between 85.6-88.3Mpa.

[0080] It can be seen from Example 1 and Comparative Example 1 that the drying and curing temperature of the modified large tow carbon fiber prepared in Comparative Example 1 is higher than 170°C, and the S 1 -S 2The value is 0.72%, and the amount of hair is 8.8 mg, which is higher than that of Example 1. Moreover, the wear resistance number of the modified large tow carbon fiber obtained in Comparative Example 1 is 388, and the interlaminar shear strength is only 75.1 MPa, which are lower than those of Example 1. This is because the drying and curing temperature of Comparative Example 1 is too high, resulting in excessive chemical reaction between the sizing agent components and between the sizing agent and the surface of the large tow carbon fiber, causing partial fiber stiffening and hardening, thereby increasing the amount of hair in the obtained modified large tow carbon fiber, deteriorating the wear resistance, and significantly reducing the mechanical strength.

[0081] It can be seen from Example 1 and Comparative Example 2 that the drying and curing temperature in the preparation of the modified large tow carbon fiber in Comparative Example 2 is lower than 100°C, and the S 1 -S 2 The value is 0.02, which is much lower than that in Example 1. The amount of hair of the modified large tow carbon fiber obtained in Comparative Example 2 is 11.9 mg, which is much higher than that in Example 1. Moreover, the wear resistance of the modified large tow carbon fiber obtained in Comparative Example 2 is 278, and the interlaminar shear strength is only 76.5 MPa, which is also lower than that in Example 1, indicating that the wear resistance and interlaminar shear strength of the modified large tow carbon fiber obtained in Comparative Example 2 are worse than those in Example 1. This is because the drying and curing temperature of Comparative Example 2 is too low, and the drying and reaction are insufficient, so there is almost no difference between the total amount of sizing and the unreacted sizing, and the improvement effect is not achieved. The obtained modified large tow carbon fiber has poor hair control and wear resistance.

[0082] It can be seen from Example 1 and Comparative Example 3 that the amount of hair in the modified large tow carbon fiber prepared in Comparative Example 3 is 10.3 mg, which is much higher than that in Example 1, and the wear resistance number of the modified large tow carbon fiber prepared in Comparative Example 3 is 354, and the interlaminar shear strength is 83.2 MPa, which are lower than those in Example 1. This is because the amount of epoxy resin in the sizing agent used in Comparative Example 3 is too small, resulting in poor bonding ability between carbon fiber tows in the prepared modified large tow carbon fiber.

[0083] It can be seen from Example 1 and Comparative Example 4 that the amount of hair of the modified large tow carbon fiber prepared in Comparative Example 4 is 14.6 mg, which is much higher than that in Example 1, and the wear resistance number of the modified large tow carbon fiber prepared in Comparative Example 4 is 245, and the interlaminar shear strength is 75.2 MPa, which are lower than those in Example 1. This is because no polyethyleneimine component is added to the sizing agent used in Comparative Example 4, and during the drying and curing process, the sizing agent cannot effectively react with the surface of the large tow carbon fiber, so the amount of hair and wear resistance of the prepared modified large tow carbon fiber are poor.

[0084] It can be seen from Example 1 and Comparative Example 5 that the amount of hair of the modified large tow carbon fiber prepared in Comparative Example 5 is 13.8 mg, which is much higher than that in Example 1, and the wear resistance number of the modified large tow carbon fiber prepared in Comparative Example 5 is 325, and the interlaminar shear strength is 74.3 MPa, which is significantly lower than that in Example 1. This is because the amount of polyethyleneimine in the sizing agent used in Comparative Example 5 is too high, and during the drying and curing process, the chemical reaction between the sizing agent components and the sizing agent and the surface of the large tow carbon fiber is excessive, so the prepared modified large tow carbon fiber has poor hair amount and wear resistance, and the interlaminar shear strength is significantly reduced.

[0085] Comparative Example 6 is a modified large-tow carbon fiber prepared by using KTM-1 epoxy emulsion sizing agent, and the amount of fuzz is 15.5 mg, which is much higher than Examples 1-6 of the present invention. The wear resistance of the modified large-tow carbon fiber prepared in Comparative Example 6 is only 266, and the interlaminar shear strength is only 73.5 MPa, which is much lower than Examples 1-6 of the present invention. This indicates that the performance of the modified large-tow carbon fiber prepared in Comparative Example 6 is not as good as that of Examples 1-6 of the present invention.

[0086] From the above, we can see that when S 1 -S 2 When the value is between 0.2-0.6%, especially between 0.3-0.5%, the process performance of the modified large-tow carbon fiber obtained is better.

[0087] The above results show that the amount of fuzz in the modified large-tow carbon fiber prepared by the sizing agent of the present invention is greatly reduced, the wear resistance times are significantly improved, and the interlaminar shear strength is also significantly improved, which indicates that the process performance of the modified large-tow carbon fiber prepared by the sizing agent of the present invention has been effectively improved, and the interface bonding ability between the sizing agent and the large-tow carbon fiber is strong.

[0088] Although the preferred embodiments of the present invention have been disclosed as above, they are not intended to limit the content of the present invention. Anyone familiar with this art can make various changes and modifications without departing from the main spirit and content of the present invention. Therefore, the protection scope of the invention should be based on the actual scope of the claims of the patent application. Therefore, the present invention is not limited to the above embodiments, and any equivalent changes, simple modifications and modifications made within the scope of the present invention still belong to the scope of the present invention.

Claims

1. A sizing agent, It is characterized in that The invention comprises bisphenol F epoxy resin, polyethyleneimine, surfactant and water; the weight average molecular weight of the polyethyleneimine is 800-1800; Among them, the content of the bisphenol F epoxy resin is 40-80%; the content of the polyethyleneimine is 10-50%; the content of the surfactant is 5-15%; the percentage is the percentage of the sum of the masses of the bisphenol F epoxy resin, the polyethyleneimine and the surfactant.

2. The sizing agent according to claim 1, It is characterized in that The content of the bisphenol F epoxy resin is 45-80%; And / or, the content of polyethyleneimine is 20-50%; And / or, the content of the surfactant is 5-10%; And / or, the amount of water added is 20-50%, which is the percentage of the total mass of the sizing agent.

3. The sizing agent according to claim 2, It is characterized in that The content of the bisphenol F epoxy resin is 45-70%; And / or, the content of polyethyleneimine is 20-40%.

4. The sizing agent according to claim 3, It is characterized in that The content of the bisphenol F epoxy resin is 50%, 60% or 65%; And / or, the content of polyethyleneimine is 30%.

5. The sizing agent according to claim 1, It is characterized in that The bisphenol F epoxy resin has an epoxy equivalent of 160-1000 g / eq; And / or, the polyethyleneimine is polyethyleneimine terminated with ethylenediamine.

6. The sizing agent according to claim 5, It is characterized in that The bisphenol F epoxy resin has an epoxy equivalent of 160-500 g / eq.

7. The sizing agent according to claim 6, It is characterized in that The epoxy equivalent of the bisphenol F epoxy resin is 170 g / eq, 180 g / eq or 475 g / eq.

8. The sizing agent according to claim 1, It is characterized in that The weight average molecular weight of the polyethyleneimine is 1500.

9. The sizing agent according to claim 1, It is characterized in that The surfactant is one or more of a cationic surfactant, an anionic surfactant and a nonionic surfactant.

10. The sizing agent according to claim 9, It is characterized in that The surfactant is a nonionic surfactant.

11. The sizing agent according to claim 10, It is characterized in that The nonionic surfactant includes one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, fatty amine polyoxyethylene ether and block polyoxyethylene-polyoxypropylene ether.

12. The sizing agent according to claim 11, It is characterized in that The nonionic surfactant is fatty alcohol polyoxyethylene ether.

13. The sizing agent according to claim 12, It is characterized in that The nonionic surfactant is C16-C18 fatty alcohol polyoxyethylene ether.

14. The sizing agent according to claim 12, It is characterized in that The fatty alcohol polyoxyethylene ether is one or more of Peregal O-8, Peregal O-10, Peregal O-15, Peregal O-20 and Peregal O-30.

15. A method for preparing a sizing agent according to any one of claims 1 to 14, It is characterized in that The method comprises mixing the raw material composition of the sizing agent.

16. The method for preparing a sizing agent according to claim 15, It is characterized in that The method comprises the following steps: heating a mixture containing the bisphenol F epoxy resin, the polyethyleneimine and the surfactant, and then adding water for emulsification.

17. A sizing agent, It is characterized in that The sizing agent is prepared by the preparation method of the sizing agent according to claim 15 or 16.

18. A method for preparing modified large tow carbon fiber, It is characterized in that It includes: Sizing and drying of large tow carbon fibers; The sizing agent used in the sizing is the sizing agent described in any one of claims 1 to 14 and 17; The drying and curing temperature is 100-170°C.

19. The method for preparing the modified large-tow carbon fiber according to claim 18, It is characterized in that The sizing method is dipping, transfer or spraying; And / or, the drying and curing temperature is 120-150°C; And / or, the drying and curing method is hot air drying, hot roller drying, infrared drying or microwave drying.

20. The method for preparing the modified large-tow carbon fiber according to claim 19, It is characterized in that The drying and curing temperature is 135°C.

21. A modified large tow carbon fiber, It is characterized in that It is prepared by the method for preparing modified large-tow carbon fiber as described in claim 18 or 19.

22. The modified large-tow carbon fiber according to claim 21, It is characterized in that The modified large tow carbon fiber satisfies S 1 -S 2 The value of S is 0.2-0.6%; 1 Indicates the total sizing amount, S 2 Indicates the amount of unreacted sizing.

23. The modified large-tow carbon fiber according to claim 22, It is characterized in that The modified large tow carbon fiber satisfies S 1 -S 2 The value is 0.3-0.5%.

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