Aqueous polyurethane and indigo-based aqueous polyurethane sizing agent, preparation method and application

Abstract

The present application provides aqueous polyurethane and indigo-based aqueous polyurethane sizing agent, and preparation method and application. The aqueous polyurethane has the following structure: the indigo-based aqueous polyurethane sizing agent comprises main agent resin, auxiliary agent, indigo-based dye and water, wherein the main agent resin comprises aqueous polyurethane and epoxy resin, and the auxiliary agent comprises plasticizer and surfactant. The sizing agent has good affinity with the indigo-based dye, and has good compatibility with the thermosetting and thermoplastic resin matrix, and can simultaneously play the roles of improving the surface activity of carbon fiber, enhancing the mechanical properties of carbon fiber, and strengthening the bonding strength between carbon fiber and resin matrix.

Description

Technical Field

[0001] This invention relates to the field of fiber manufacturing, specifically to a waterborne polyurethane and its preparation method, an indigo-based waterborne polyurethane sizing agent, and the preparation method and application of the indigo-based waterborne polyurethane sizing agent. Background Technology

[0002] Carbon fiber is a high-strength, high-modulus fiber with a carbon content of over 90%. Its raw materials are derived from acrylic and viscose fibers, and it possesses properties such as high temperature resistance, friction resistance, electrical conductivity, thermal conductivity, and corrosion resistance. Carbon fiber reinforced polymer (CFRP) composites are made using carbon fiber or fiber fabrics as reinforcement and resin, ceramics, metals, or rubber as the matrix. Carbon fiber can be combined with polyurethane to prepare carbon fiber / polyurethane composites, as carbon fiber significantly improves the mechanical and heat resistance properties of the composite. Polyurethane, short for polyurethane ester, possesses high mechanical strength, high wear resistance, and chemical inertness, and is widely used in defense and civilian industries.

[0003] Waterborne polyurethane has been a research hotspot in recent years. Introducing hydrophilic chain extenders into the main chain of waterborne polyurethane through chemical means allows functional groups containing carboxyl, sulfonic acid, or amino groups to be attached to the polyurethane molecular chain, thereby giving the polyurethane chain segments ionizable functional groups. Patent CN102786651A discloses a waterborne polyurethane binder, a waterborne polyurethane composite binder, and a preparation method. The patent describes the reaction of diisocyanate, polypropylene glycol, ethylenediamine, and a hydrophilic chain extender, followed by the use of a neutralizing agent to prepare the waterborne polyurethane. This waterborne polyurethane binder features high solids content, low viscosity, and pH stability, and also exhibits excellent static stability, centrifugal stability, and thermal stability. The preparation method is simple and convenient.

[0004] Currently, the most common method for waterborne polyurethane is the neutralizing agent treatment. This method causes carboxyl groups to form salts, thereby giving the waterborne polyurethane good solubility. The resulting waterborne polyurethane can be combined with epoxy resin to prepare sizing agents and can also act as an interface layer between carbon fibers and polyurethane. However, this type of sizing agent cannot fully emulsify some non-polar molecules. Therefore, it is essential to modify the waterborne polyurethane to improve its surface activity.

[0005] Indigo is a water-soluble non-azo colorant. Indigo dyes are among the oldest known pigments and are widely used in the food, pharmaceutical, and dyeing industries. As a vat dye, indigo has poor water solubility. In factory dyeing applications, it needs to be treated with reducing agents and other auxiliaries to convert it into a leuco form before dyeing can proceed. Patent CN105463730A discloses a method for dyeing indigo denim. The patent describes a dye solution prepared from indigo, sodium hydrosulfite, and caustic soda, followed by dyeing processes including dye reduction, chromosome staining, leuco oxidation, and post-dyeing treatment. This series of processes is complex and has certain requirements regarding the type of fiber, making it unsuitable for fibers with fewer surface-active groups, such as carbon fiber. Therefore, designing a sizing agent suitable for dyeing carbon fiber is a highly significant undertaking. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention first provides a waterborne polyurethane, and then mixes the waterborne polyurethane, epoxy resin, and indigo dyes to prepare an indigo-based waterborne polyurethane sizing agent. The main component of the waterborne polyurethane in this sizing agent has an adjustable configuration, good affinity with indigo dyes, and good composite properties with polyurethane and epoxy resin, showing promising application prospects in the field of composite material preparation.

[0007] One objective of this invention is to provide an aqueous polyurethane having the structure shown in formula (I):

[0008]

[0009] Where m is 1 to 10; n is 1 to 10; o is 1 to 10;

[0010] Where R1 is

[0011] R2 is

[0012]

[0013]

[0014] R3 is

[0015] R4 is

[0016] R5 is -SO3 - Na + ,

[0017] R6 is

[0018] R7 is NH(C2H5)3, NH4, Na, K.

[0019] In the above-described technical solution, R2 in the general formula (I) is arranged alternately with R1, R3, and R4. R1, R3, and R4 can be in any order, such as R2-R1-R2-R3-R2-R4-R2, R2-R1-R2-R4-R2-R3-R2, etc.; R5 seals R2.

[0020] The second objective of this invention is to provide a method for preparing the waterborne polyurethane, comprising first performing a prepolymerization reaction of polyether and diisocyanate, then adding a chain extender to perform a chain extension reaction, using an end-capping agent for end-capping, adding ethanol for further end-capping, then adding a modifier for modification, and finally adding a neutralizing agent for salt formation to obtain the waterborne polyurethane.

[0021] The diisocyanate is preferably at least one selected from toluene diisocyanate, terephthalic diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dimethylbiphenyl diisocyanate, dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate.

[0022] The polyether is preferably at least one of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran.

[0023] The molecular weight of the polyether is preferably between 200 and 6000.

[0024] The chain extender is preferably at least one of dimethylolbutyric acid and dimethylolpropionic acid.

[0025] The capping agent is preferably at least one of sodium bisulfite and methyl ethyl ketone oxime.

[0026] The modifier is preferably at least one of dimethylaminochloroethane, diethylaminochloroethane, 2-chloro-1-(dimethylamino)propane, and 3-(dimethylamino)chloropropane.

[0027] The neutralizing agent is preferably at least one of triethylamine, ammonia, sodium hydroxide, and potassium hydroxide.

[0028] The mass ratio of polyether to diisocyanate is (0.07 to 20):1, for example, 0.07:1, 0.1:1, 0.5:1, 1:1, 5:1, 10:1, 15:1, 20:1, etc., and the prepolymerization reaction is preferably carried out at 70 to 90°C for 1 to 3 hours.

[0029] The mass ratio of the chain extender to the diisocyanate is (0.05 to 0.6):1, for example, it can be 0.05:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, etc., and the chain extension reaction is preferably carried out at 50 to 70°C for 4 to 8 hours.

[0030] The mass ratio of the capping agent to the diisocyanate is (0.1 to 0.6):1, for example, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, etc., and the capping reaction is preferably carried out at 20 to 30°C for 0.5 to 2 hours.

[0031] The mass ratio of ethanol to diisocyanate is (0.3–3):1, for example, 0.3:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, etc., and the end-capping reaction is preferably carried out at 20–30°C for 0.5–2 hours. After the reaction is completed, steps such as removing ethanol and washing with solvents such as acetone can be performed.

[0032] The mass ratio of the modifier to the diisocyanate is (0.05–0.7):1, for example, 0.05:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, etc., and the modification reaction is preferably carried out at 20–30°C for 4–8 hours. After the reaction is completed, a step to remove acetone and hydrogen chloride can be performed.

[0033] The mass ratio of neutralizing agent to diisocyanate is (0.006–0.4):1, for example, 0.006:1, 0.01:1, 0.05:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, etc., and the salt-forming reaction is preferably carried out at 20–30°C for 0.2–2 hours. This neutralization reaction can be carried out in a solvent such as acetone.

[0034] A third objective of this invention is to provide an aqueous polyurethane obtained by the aforementioned preparation method.

[0035] The fourth objective of this invention is to provide an indigo-based waterborne polyurethane sizing agent, comprising a main resin, an indigo dye, an auxiliary agent, and water; wherein the main resin comprises the waterborne polyurethane and an epoxy resin, and the auxiliary agent comprises a plasticizer and a surfactant.

[0036] The waterborne polyurethane has the structure shown in general formula (I).

[0037] The epoxy resin is preferably at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin.

[0038] The indigo dye is preferably at least one of indigo, bromoindigo, and indigo carmine.

[0039] The surfactant is preferably at least one of oleic acid, potassium oleate, and sodium oleate.

[0040] The plasticizer is preferably at least one of dioctyl adipate, diisononyl phthalate, dioctyl phthalate, and dioctyl sebacate.

[0041] The mass ratio of epoxy resin, indigo dye, surfactant, plasticizer, water, and waterborne polyurethane is (0.02-4):(0.000002-0.06):(0.002-0.7):(0.003-0.9):(0.36-90):1, preferably (0.05-3):(0.00005-0.012):(0.01-0.4):(0.01-0.5):(0.9-36):1.

[0042] The fifth objective of this invention is to provide a method for preparing the sizing agent, which involves mixing raw materials including a main resin, an auxiliary agent, and an indigo dye, diluting the mixed raw material system with water to a solid content of 10-50 wt%, and emulsifying to obtain the sizing agent.

[0043] The emulsification conditions were 3000–11000 rpm for 0.2–2 hours.

[0044] In the preferred method for preparing the sizing agent, waterborne polyurethane, indigo dyes, and epoxy resins are added to a reactor at 20–30°C and stirred for 0.2–1 hour. Surfactants and plasticizers are then added to the reactor, and water is added to dilute the mixture to a solid content of 10%–50%. The mixture is then emulsified at 3000–11000 rpm for 0.2–2 hours to obtain the indigo-based waterborne polyurethane sizing agent.

[0045] The sizing agent described in this invention has good affinity with indigo dyes and can effectively improve the processing performance of carbon fibers. This invention can be applied to different types of resin matrices by changing the structure and component ratio of the resin in the sizing agent main agent.

[0046] The sixth objective of this invention is to provide the application of the indigo-based waterborne polyurethane sizing agent or the sizing agent obtained by the preparation method in carbon fiber composite materials.

[0047] The sizing agent described in this invention has good affinity with indigo dyes, can impart certain coloring properties to carbon fibers, and can improve the interfacial properties between carbon fibers and epoxy and polyurethane resin matrices.

[0048] The indigo-based waterborne polyurethane sizing agent is diluted to 1-3% and used on the carbon fiber production line for sizing treatment of carbon fibers. The fibers are then dried at 110-160°C and collected.

[0049] The indigo-based waterborne polyurethane sizing agent of the present invention has a moderate sizing amount (0.6-1.5%), low saturated water absorption rate (<0.1%), moderate interlaminar shear strength (70-110MPa), controllable particle size (50-500nm), and good stability (>6 months).

[0050] This invention relates to an indigo-based waterborne polyurethane sizing agent. This sizing agent exhibits good affinity with indigo dyes and good compatibility with both thermosetting and thermoplastic resin matrices. It simultaneously enhances the surface activity of carbon fibers, strengthens their mechanical properties, and improves the bond strength between the carbon fibers and the resin matrix. This sizing agent imparts good coloring performance, sufficient bundle aggregation, and low sizing adhesion to carbon fibers. The process of this invention is simple, has good repeatability, and can meet market demand for indigo-based sizing agents.

[0051] The features of this invention are:

[0052] (1) The waterborne polyurethane in the main agent introduces carboxyl groups into the polyurethane main chain. Modifiers such as dimethylaminochloroethane are used to modify some of the carboxyl groups to improve the affinity of polyurethane to non-polar substances. Neutralizing agents are used to neutralize the remaining carboxyl groups to form salts, so that polyurethane has a better affinity to polar substances. Because waterborne polyurethane has good amphiphilicity, it can form a stable emulsion with indigo dyes and resins.

[0053] (2) The use of indigo dyes and water-based polyurethane in proportion can reduce the amount of indigo dyes used, and the production method is simple and reduces production costs.

[0054] (3) The epoxy resin, surfactant and plasticizer can be adjusted according to the sizing agent. The molecular weight of polyether, the type of surfactant and the variety of plasticizer can be adjusted according to the usage conditions. The particle size of the sizing agent emulsion can be designed according to the usage environment, thereby improving the sizing performance. Detailed Implementation

[0055] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0056] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0057] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0058] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0059] According to a preferred embodiment of the present invention, the preparation method of the indigo-based waterborne polyurethane sizing agent may include the following steps:

[0060] Step a) Under a nitrogen atmosphere at room temperature, add polyether to the reactor at a mass ratio of 0.07:1 to 20:1, based on the amount of diisocyanate added. React at 70-90°C for 1-3 hours, then cool to 50-70°C. Add chain extender to the reactor at a mass ratio of 0.05:1 to 0.6:1, based on the amount of diisocyanate added. React for 4-8 hours, then cool to 20-30°C. Add end-capping agent to the reactor at a mass ratio of 0.1:1 to 0.6:1, based on the amount of diisocyanate added. React for 0.5-2 hours, then add ethanol to diisocyanate at a mass ratio of 0.07:1 to 20:1. The ratio of ethanol to diisocyanate is 0.3:1 to 3:1. After reacting for 0.5 to 2 hours, the ethanol is removed by vacuum distillation. The mass ratio of acetone to diisocyanate is 2:1 to 20:1. After stirring for 1 to 2 hours, the mixture is filtered, and the filtrate is collected and placed in the reactor. The modifier is added to the reactor at a mass ratio of 0.05:1 to 0.7:1. After reacting for 4 to 8 hours, the neutralizer and diisocyanate are added to the reactor at a mass ratio of 0.006:1 to 0.4:1. After stirring for 4 to 8 hours, an aqueous polyurethane solution is obtained.

[0061] Step b) At 20–30°C, based on the amount of waterborne polyurethane added, according to the mass ratio of indigo dye to waterborne polyurethane of 0.000002:1–0.06:1 and the mass ratio of epoxy resin to waterborne polyurethane of 0.02:1–4:1, waterborne polyurethane, indigo dye, and epoxy resin are added to the reactor and stirred for 0.2–1 hour. Based on the amount of waterborne polyurethane added, according to the mass ratio of surfactant to waterborne polyurethane of 0.002:1–0.7:1, the mass ratio of plasticizer to waterborne polyurethane of 0.003:1–0.9:1 and the mass ratio of water to waterborne polyurethane of 0.36:1–90:1, surfactant, plasticizer, and water are added to the reactor. Water is added to dilute the mixture to a solid content of 10%–50%, and emulsification is carried out at 3000–11000 rpm for 0.2–2 hours to obtain an indigo-based waterborne polyurethane sizing agent.

[0062] Test method:

[0063] The sizing amount and saturated water absorption rate of the sized carbon fiber were tested. The interlaminar shear strength (ILSS) test was conducted according to JC / T773-2010. The resin used in the ILSS test was polyurethane, and the raw materials were toluene diisocyanate and polyethylene glycol.

[0064] Example 1:

[0065] Under a nitrogen atmosphere at room temperature, 6.96 g of toluene diisocyanate and 20 g of polyethylene glycol (MW2000) were added to a reactor. After reacting at 80°C for 1 hour, the temperature was lowered to 60°C, and 2.68 g of dimethylolpropionic acid was added. After reacting for 5 hours, the temperature was lowered to 25°C, and 2.5 g of sodium bisulfite was added. After reacting for 1 hour, 10 g of ethanol was added, and the mixture was stirred for 0.5 hours. The ethanol was removed by vacuum distillation, and 50 g of acetone was added. The mixture was filtered, and the filtrate was collected and placed in a reactor. 1.44 g of dimethylaminochloroethane was added to the reactor, and the mixture was reacted for 6 hours. Then, 1.01 g of triethylamine was added, and the mixture was reacted for 1 hour to obtain 77.63 g of an aqueous polyurethane solution.

[0066] At 25°C, 77.63g of waterborne polyurethane solution, 0.03g of indigo and 13.6g of bisphenol A epoxy resin (618) were added to a reactor and stirred for 0.5 hours. Then, 2.44g of sodium oleate and 2.96g of dioctyl adipate were added, and water was added to dilute the mixture to a solid content of 20%. The mixture was emulsified at 7000rpm for 1 hour to obtain 233.3g of indigo waterborne polyurethane sizing agent.

[0067] The indigo waterborne polyurethane sizing agent prepared in Example 1 was diluted to 1.5% and used for sizing carbon fibers on a carbon fiber production line. The fibers were dried at 120°C and then wound up. The sizing amount of the carbon fibers after sizing was 1.2%, the saturated water absorption rate was 0.08%, and the ILSS was 81 MPa.

[0068] Example 2:

[0069] Under a nitrogen atmosphere at room temperature, 6.96 g of toluene diisocyanate and 20 g of polyethylene glycol (MW2000) were added to a reactor. After reacting at 80°C for 1 hour, the temperature was lowered to 60°C, and 2.68 g of dimethylolpropionic acid was added. After reacting for 5 hours, the temperature was lowered to 25°C, and 2.5 g of sodium bisulfite was added. After reacting for 1 hour, 10 g of ethanol was added, and the mixture was stirred for 0.5 hours. The ethanol was removed by vacuum distillation, and 50 g of acetone was added. The mixture was filtered, and the filtrate was collected and placed in a reactor. 1.44 g of dimethylaminochloroethane was added to the reactor, and the mixture was reacted for 6 hours. Then, 1.01 g of triethylamine was added, and the mixture was reacted for 1 hour to obtain 77.63 g of an aqueous polyurethane solution.

[0070] At 25°C, 77.63g of waterborne polyurethane solution, 0.03g of bromoindigo and 13.6g of bisphenol A epoxy resin (618) were added to a reactor and stirred for 0.5 hours. Then, 2.44g of sodium oleate and 2.96g of dioctyl adipate were added, and water was added to dilute the mixture to a solid content of 20%. The mixture was emulsified at 7000 rpm for 1 hour to obtain 233.3g of bromoindigo waterborne polyurethane sizing agent.

[0071] The bromoindigo-based waterborne polyurethane sizing agent prepared in Example 2 was diluted to 1.5% and used for sizing carbon fibers on a carbon fiber production line. The fibers were then dried at 120°C and wound up. The sizing adhesion of the carbon fibers after sizing was 1.1%, the saturated water absorption rate was 0.07%, and the ILSS was 80 MPa.

[0072] Example 3:

[0073] Under a nitrogen atmosphere at room temperature, 6.96 g of toluene diisocyanate and 20 g of polyethylene glycol (MW2000) were added to a reactor. After reacting at 80°C for 1 hour, the temperature was lowered to 60°C, and 2.96 g of dimethylolbutyric acid was added. After reacting for 5 hours, the temperature was lowered to 25°C, and 2.5 g of sodium bisulfite was added. After reacting for 1 hour, 10 g of ethanol was added, and the mixture was stirred for 0.5 hours. The ethanol was removed by vacuum distillation, and 50 g of acetone was added. The mixture was filtered, and the filtrate was collected and placed in a reactor. 1.44 g of dimethylaminochloroethane was added to the reactor, and the mixture was reacted for 6 hours. Then, 1.01 g of triethylamine was added, and the mixture was reacted for 1 hour to obtain 77.91 g of an aqueous polyurethane solution.

[0074] At 25°C, 77.91g of waterborne polyurethane solution, 0.03g of indigo and 13.6g of bisphenol A epoxy resin (618) were added to a reactor and stirred for 0.5 hours. Then, 2.44g of sodium oleate and 2.96g of dioctyl adipate were added, and water was added to dilute the mixture to a solid content of 20%. The mixture was emulsified at 7000rpm for 1 hour to obtain 234.7g of indigo waterborne polyurethane sizing agent.

[0075] The indigo waterborne polyurethane sizing agent prepared in Example 3 was diluted to 1.5% and used for sizing carbon fibers on a carbon fiber production line. The fibers were then dried at 120°C and wound up. The sizing adhesion of the carbon fibers after sizing was 1.3%, the saturated water absorption rate was 0.09%, and the ILSS was 83 MPa.

[0076] Example 4:

[0077] Under a nitrogen atmosphere at room temperature, 6.96 g of toluene diisocyanate and 20 g of polyethylene glycol (MW2000) were added to a reactor. After reacting at 80°C for 1 hour, the temperature was lowered to 60°C, and 2.68 g of dimethylolpropionic acid was added. After reacting for 5 hours, the temperature was lowered to 25°C, and 2.09 g of methyl ethyl ketone oxime was added. After reacting for 1 hour, 10 g of ethanol was added, and the mixture was stirred for 0.5 hours. The ethanol was removed by vacuum distillation, and 50 g of acetone was added. The mixture was filtered, and the filtrate was collected and placed in a reactor. 1.44 g of dimethylaminochloroethane was added to the reactor, and the mixture was reacted for 6 hours. Then, 1.01 g of triethylamine was added, and the mixture was reacted for 1 hour to obtain 77.22 g of an aqueous polyurethane solution.

[0078] At 25°C, 77.22g of waterborne polyurethane solution, 0.03g of indigo and 13.6g of bisphenol A epoxy resin (618) were added to a reactor and stirred for 0.5 hours. Then, 2.44g of sodium oleate and 2.96g of dioctyl adipate were added, and water was added to dilute the mixture to a solid content of 20%. The mixture was emulsified at 7000rpm for 1 hour to obtain 231.25g of indigo waterborne polyurethane sizing agent.

[0079] The indigo waterborne polyurethane sizing agent prepared in Example 4 was diluted to 1.5% and used for sizing carbon fibers on a carbon fiber production line. The fibers were then dried at 120°C and wound into fibers. The sizing adhesion of the carbon fibers after sizing was 1.1%, the saturated water absorption rate was 0.07%, and the ILSS was 85 MPa.

[0080] Example 5:

[0081] Under a nitrogen atmosphere at room temperature, 6.96 g of toluene diisocyanate and 20 g of polyethylene glycol (MW2000) were added to a reactor. After reacting at 80°C for 1 hour, the temperature was lowered to 60°C, and 2.68 g of dimethylolpropionic acid was added. After reacting for 5 hours, the temperature was lowered to 25°C, and 2.5 g of sodium bisulfite was added. After reacting for 1 hour, 10 g of ethanol was added, and the mixture was stirred for 0.5 hours. The ethanol was removed by vacuum distillation, and 50 g of acetone was added. The mixture was filtered, and the filtrate was collected and placed in a reactor. 1.44 g of dimethylaminochloroethane was added to the reactor, and the mixture was reacted for 6 hours. Then, 1.01 g of triethylamine was added, and the mixture was reacted for 1 hour to obtain 77.63 g of an aqueous polyurethane solution.

[0082] At 25°C, 77.63g of waterborne polyurethane solution, 0.03g of indigo and 10.2g of bisphenol A epoxy resin (618) were added to a reactor and stirred for 0.5 hours. Then, 2.44g of sodium oleate and 2.96g of dioctyl adipate were added, and water was added to dilute the mixture to a solid content of 20%. The mixture was emulsified at 7000rpm for 1 hour to obtain 216.3g of indigo waterborne polyurethane sizing agent.

[0083] The indigo waterborne polyurethane sizing agent prepared in Example 5 was diluted to 1.5% and used for sizing carbon fibers on a carbon fiber production line. The fibers were then dried at 120°C and wound up. The sizing adhesion of the carbon fibers after sizing was 1.1%, the saturated water absorption rate was 0.07%, and the ILSS was 82 MPa.

[0084] Comparative Example 1:

[0085] Under a nitrogen atmosphere at room temperature, 6.96 g of toluene diisocyanate and 20 g of polyethylene glycol (MW2000) were added to a reactor. After reacting at 80°C for 1 hour, the temperature was lowered to 60°C, and 2.68 g of dimethylolpropionic acid was added. After reacting for 5 hours, the temperature was lowered to 25°C, and 2.5 g of sodium bisulfite was added. After reacting for 1 hour, 10 g of ethanol was added, and the mixture was stirred for 0.5 hours. The ethanol was removed by vacuum distillation, and 50 g of acetone was added. The mixture was filtered, and the filtrate was collected and placed in a reactor. 1.44 g of dimethylaminochloroethane was added to the reactor, and the mixture was reacted for 6 hours. Then, 1.01 g of triethylamine was added, and the mixture was reacted for 1 hour to obtain 77.63 g of an aqueous polyurethane solution.

[0086] At 25°C, 77.63g of waterborne polyurethane and 13.6g of bisphenol A epoxy resin (618) were added to a reactor and stirred for 0.5 hours. Then, 2.44g of sodium oleate and 2.96g of dioctyl adipate were added, and the mixture was diluted with water to a solid content of 20%. The mixture was emulsified at 7000rpm for 1 hour to obtain 233.15g of waterborne polyurethane sizing agent.

[0087] The aqueous polyurethane sizing agent prepared in this comparative example was diluted to 1.5% and used on a carbon fiber production line for sizing treatment of carbon fibers. The fibers were then dried at 120°C and wound into fibers. The sizing adhesion of the carbon fibers after sizing was 1.1%, the saturated water absorption rate was 0.07%, and the ILSS was 75 MPa.

[0088] Comparative Example 2:

[0089] Under a nitrogen atmosphere at room temperature, 6.96 g of toluene diisocyanate and 20 g of polyethylene glycol (MW2000) were added to a reactor. After reacting at 80°C for 1 hour, the temperature was lowered to 60°C, and 2.68 g of dimethylolpropionic acid was added. After reacting for 5 hours, the temperature was lowered to 25°C, and 2.5 g of sodium bisulfite was added. After reacting for 1 hour, 10 g of ethanol was added, and the mixture was stirred for 0.5 hours. The ethanol was removed by vacuum distillation, and 50 g of acetone was added. The mixture was filtered, and the filtrate was collected and placed in a reactor. Then, 2.02 g of triethylamine was added, and the mixture was reacted for 1 hour to obtain 77.2 g of an aqueous polyurethane solution.

[0090] At 25°C, 77.2g of waterborne polyurethane solution, 0.03g of indigo, and 13.6g of bisphenol A epoxy resin (618) were added to a reactor and stirred for 0.5 hours. Then, 2.44g of sodium oleate and 2.96g of dioctyl adipate were added, and water was added to dilute the mixture to a solid content of 20%. The mixture was emulsified at 7000 rpm for 1 hour to obtain 231g of indigo waterborne polyurethane sizing agent. The obtained sizing agent settled within one day and could not be used.

Claims

1. A waterborne polyurethane having the structure shown in formula (I): （I）， Where m is 1~10; n is 1~10; o is 1~10; Where R1 is , ,or ; R2 is , , , , , ,or ; R3 is ,or ; R4 is ,or ; R5 is ,or ; R6 is , , ,or ; R7 is , , Na, or K.

2. The waterborne polyurethane according to claim 1, characterized in that: In equation (I), R2 is arranged alternately with R1, R3, and R4, and R1, R3, and R4 are in any order. R5 closes R2.

3. A method for preparing waterborne polyurethane according to claim 1 or 2, comprising firstly, prepolymerizing polyether and diisocyanate, then adding a chain extender for chain extension, using an end-capping agent for end-capping, adding ethanol for further end-capping, then adding a modifier for modification, and finally adding a neutralizing agent for salt formation to obtain the waterborne polyurethane.

4. The preparation method according to claim 3, characterized in that: The diisocyanate is at least one selected from toluene diisocyanate, terephthalic diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dimethylbiphenyl diisocyanate, dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate; and / or, The polyether is at least one selected from polyethylene glycol, polypropylene glycol, and polytetrahydrofuran; and / or The chain extender is at least one of dimethylolbutyric acid and dimethylolpropionic acid; and / or... The capping agent is at least one of sodium bisulfite and methyl ethyl ketone oxime; and / or The modifier is at least one selected from dimethylaminochloroethane, diethylaminochloroethane, 2-chloro-1-(dimethylamino)propane, and 3-(dimethylamino)chloropropane; and / or, The neutralizing agent is at least one of triethylamine, ammonia, sodium hydroxide, and potassium hydroxide.

5. The preparation method according to claim 4, characterized in that: The polyether has a molecular weight of 200 to 6000.

6. The preparation method according to claim 3, characterized in that: The mass ratio of the polyether to diisocyanate is (0.07~20):1, and the reaction temperature of the prepolymerization reaction is 70~90℃; and / or, The mass ratio of the chain extender to the diisocyanate is (0.05~0.6):1, and the reaction temperature of the chain extension reaction is 50~70℃; and / or, The mass ratio of the capping agent to the diisocyanate is (0.1~0.6):1; the capping reaction temperature is 20~30℃; and / or, The mass ratio of ethanol to diisocyanate is (0.3~3):1, and the end-capping reaction temperature is 20~30℃; and / or, The mass ratio of the modifier to the diisocyanate is (0.05~0.7):1, and the reaction temperature of the modification reaction is 20~30℃; and / or, The mass ratio of the neutralizing agent to the diisocyanate is (0.006~0.4):1, and the reaction temperature for the salt formation reaction is 20~30℃.

7. An indigo-based waterborne polyurethane sizing agent, comprising a main resin, auxiliaries, indigo dyes, and water; wherein, The main resin includes the waterborne polyurethane and epoxy resin according to any one of claims 1 and 2, the auxiliary agents include plasticizers and surfactants, and the epoxy resin is at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin.

8. The sizing agent according to claim 7, characterized in that: The indigo dye is at least one of indigo, bromoindigo, and indigo carmine; and / or, The surfactant is at least one selected from oleic acid, potassium oleate, and sodium oleate; and / or, The plasticizer is at least one of dioctyl adipate, diisononyl phthalate, dioctyl phthalate, and dioctyl sebacate.

9. The sizing agent according to claim 7, characterized in that: The mass ratio of epoxy resin, indigo dyes, surfactants, plasticizers, water, and waterborne polyurethane is (0.02~4): (0.000002~0.06): (0.002~0.7): (0.003~0.9): (0.36~90):

1.

10. The sizing agent according to claim 9, characterized in that: The mass ratio of epoxy resin, indigo dyes, surfactants, plasticizers, water, and waterborne polyurethane is (0.05~3):(0.00005~0.012):(0.01~0.4):(0.01~0.5):(0.9~36):

1.

11. A method for preparing a sizing agent according to any one of claims 7 to 10, comprising mixing raw materials including a main resin, an auxiliary agent and an indigo dye, diluting with water to a solid content of 10 to 50 wt%, and emulsifying to obtain the sizing agent.

12. The preparation method according to claim 11, characterized in that: The emulsification conditions are 3000~11000 rpm for 0.2~2 hours.

13. The application of the sizing agent according to any one of claims 7 to 10 or the sizing agent obtained by the preparation method according to any one of claims 11 to 12 in carbon fiber composite materials.

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