High-temperature-resistant self-emulsifying water-soluble epoxy resin-based carbon fiber sizing agent and preparation method thereof

Abstract

The application discloses a high-temperature-resistant self-emulsifying water-soluble epoxy resin-based carbon fiber sizing agent and a preparation method thereof. The sizing agent is prepared from the following components in a mass percentage: 10-40% of in-situ blended phosphatized modified water-soluble bisphenol A type epoxy resin; 3-5% of polyether non-ionic emulsifier; 1-5% of fatty acid ester smooth agent; not more than 1% of other additives; and the balance of deionized water. The other additives are at least one of an antioxidant and a defoaming agent. The sizing agent has excellent surface activity and good wettability, and can form a uniform film on the surface of the carbon fiber. The sized carbon fiber has good smoothness and bundle property, and moderate stiffness, which is beneficial to processing and molding. After sizing, the surface free energy of the carbon fiber is increased, and the content of active reaction groups such as oxygen elements is increased, which is beneficial to the rapid wetting and sufficient infiltration of the matrix resin on the surface of the carbon fiber during the molding process of the composite material, and improves the interfacial bonding property and interfacial shear strength of the carbon fiber epoxy resin composite material.

Description

Technical Field

[0001] This invention relates to the field of water-soluble epoxy resin and carbon fiber sizing agent technology, specifically to a high-temperature resistant, self-emulsifying, water-soluble epoxy resin-based carbon fiber sizing agent and its preparation method. Background Technology

[0002] Sizing is one of the essential technical keys in the development, production, and application of carbon fiber and its composites. Sizing agents are generally textile auxiliaries composed of polymer resin as the main body and various other functional components. In the formulation of sizing agents, the polymer or its modified resin is the main film-forming agent, supplemented with appropriate amounts of smoothing agents, softeners, defoamers, and other functional components, which are dispersed, emulsified, or dissolved in organic solvents or water to prepare the product.

[0003] Currently available carbon fiber sizing agents are mainly classified into three categories: solvent-based sizing agents, emulsion-based sizing agents, and water-soluble sizing agents. Solvent-based sizing agents have been gradually replaced by emulsion-based sizing agents due to issues such as solvent evaporation, environmental pollution, and resin residue. However, emulsion-based sizing agents also have drawbacks: the emulsification and compounding of resins require the addition of large amounts of small-molecule surfactants or co-solvents, which also poses environmental problems. Furthermore, they are prone to demulsification, release of effective components, and poor high-temperature stability during storage and use. More importantly, the presence of large amounts of small-molecule organic substances such as emulsifiers under stress and high-temperature environments can easily lead to localized weak layers and stress defects in the sizing film on the carbon fiber surface during curing and the diffusion and migration of low-surface-energy substances such as surfactants. Additionally, small-molecule surfactants have poor heat resistance and are easily oxidized and degraded at high temperatures, resulting in poor interfacial bonding between the matrix resin and the carbon fiber reinforcing material. Although water-soluble sizing agents are uniform, stable, and have superior performance, the high technical barrier of water-based modification of polymer resins, coupled with the fact that carbon fiber sizing agent formulations and processes are key technologies and core secrets of carbon fiber manufacturers, has resulted in a lack of substantial technical reports to date. Therefore, the development and application research of high-quality water-soluble sizing agents is still in its early stages.

[0004] In recent years, the development and application of polymer-based carbon fiber composites in cutting-edge fields such as aerospace, national defense, high-speed rail and ships, and energy materials have developed rapidly. With the development and application of advanced polymer-based carbon fiber composites, the problem of insufficient high-temperature resistance of carbon fiber sizing agents has become increasingly prominent.

[0005] Epoxy resin possesses excellent adhesion, strong bonding, high mechanical properties, chemical resistance, and electrical insulation. Its molecular structure contains hydroxyl, ether, and epoxy groups, giving it high reactivity. It is currently the primary matrix resin material for preparing polymer-based carbon fiber composites and the preferred sizing agent for producing carbon fibers used in this type of composite. However, because conventional epoxy resin is insoluble in water, it cannot be directly used for sizing carbon fibers. Carbon fiber manufacturers typically prepare epoxy resin as solvent-based, emulsion-based, or water-soluble sizing agents for later use.

[0006] The fastest decomposition temperature of epoxy resin-based sizing agents currently used in industrial carbon fiber production is generally around 200℃, which meets the requirements of general carbon fiber composite material processing and application environments. However, in high-temperature processing or working environments requiring high-temperature resistance, sizing agents with poor heat resistance are prone to thermal decomposition. The residual or escaped small molecules from high-temperature carbonization and pyrolysis can cause localized degradation and stress defects in the material interface layer, affecting the overall mechanical properties of the composite material. Therefore, it is necessary to develop high-temperature resistant sizing agents that are compatible with the high-temperature working environments of epoxy resin matrices.

[0007] With increasing awareness of environmental protection and the need for the development of advanced high-performance epoxy resin-based composite materials, solvent-based epoxy resin sizing agents, emulsion-based epoxy resin sizing agents, and conventional water-based sizing agents can no longer meet the needs of the development of high-performance composite materials.

[0008] Therefore, modifying epoxy resin to significantly improve the comprehensive properties of epoxy resin-based carbon fiber sizing agents, such as water solubility, heat resistance, and adhesion, without or with minimal use of surfactants, is a core technical problem urgently needing to be solved in this field. Furthermore, epoxy resin sizing agents must possess certain fluidity, low viscosity, and low surface tension to ensure rapid wetting, uniform spreading, and film formation on the carbon fiber surface. Simultaneously, they must provide a certain degree of smoothness, softness, stiffness, and film strength to facilitate carbon fiber winding, unwinding, and subsequent processing and molding, reducing carbon fiber breakage, splintering, and fuzzing, thereby improving carbon fiber yield and product quality.

[0009] In addition, high-performance epoxy resin-based carbon fiber sizing agents also require a certain increase in the content of oxygen elements and active reactive groups on the carbon fiber surface to improve the wettability, reactivity, and interfacial adhesion of the epoxy resin matrix to the carbon fiber surface, thereby improving the overall mechanical properties of the carbon fiber composite material.

[0010] Furthermore, high-performance epoxy resin-based carbon fiber composites also require the sizing agent to have good high-temperature resistance, so that the carbon fiber composites can have good interfacial adhesion and high interfacial shear strength in harsh working environments such as high temperature. Summary of the Invention

[0011] To address the shortcomings of existing technologies, the technical problem this invention aims to solve is to provide a high-temperature resistant, self-emulsifying, water-soluble epoxy resin-based carbon fiber sizing agent and its preparation method. The sizing agent of this invention features high-temperature resistance, self-emulsification, and miscibility with water in any ratio, exhibiting good stability. The sizing agent possesses excellent surface activity and good wettability, enabling it to form a uniform film on the carbon fiber surface. After sizing, the carbon fibers exhibit good smoothness and bundle structure, with moderate stiffness, which is beneficial for processing and molding. Sizing increases the surface free energy and the content of active reactive groups such as oxygen on the carbon fibers, which facilitates rapid wetting and full impregnation of the carbon fiber surface by the matrix resin during the composite material molding process, thereby improving the interfacial bonding performance and interfacial shear strength of the carbon fiber epoxy resin composite material.

[0012] To achieve the above objectives, the technical solution of this invention is as follows:

[0013] In a first aspect, the present invention provides a high-temperature resistant, self-emulsifying, water-soluble epoxy resin-based carbon fiber sizing agent, wherein the sizing agent has the following composition by mass percentage:

[0014]

[0015] The other additives are at least one of antioxidants and defoamers.

[0016] The in-situ blended phosphorylation modified water-soluble bisphenol A type epoxy resin includes two epoxy resins: a low epoxy value high molecular weight epoxy resin and a high epoxy value low molecular weight epoxy resin. The epoxy values ​​of the two selected epoxy resins differ by 15-30 mmol / g. During preparation, the two epoxy resins are mixed and dissolved evenly, and then phosphoric acid is added in batches. After the addition is complete, the reaction continues for 1-3 hours. Then, the temperature is raised and deionized water is added in batches to maximize the formation of monophosphate esters. Finally, potassium hydroxide aqueous solution is added in batches to ensure a complete reaction, and the pH of the solution is controlled to be 7-9 after the reaction.

[0017] The molar ratio of phosphoric acid to the total epoxy value of the epoxy resin is 1:(0.5-1.5), the mass ratio of deionized water to phosphoric acid is (1.5-2.5):1, the mass ratio of potassium hydroxide to phosphoric acid is 1:(1-1.1), and the mass concentration of the potassium hydroxide aqueous solution is 20%-30%.

[0018] The low epoxy value high molecular weight epoxy resin is at least one of E20 and E-35, and the high epoxy value low molecular weight epoxy resin is at least one of E-42 and E44; the mixing ratio of the low epoxy value high molecular weight epoxy resin and the high epoxy value low molecular weight epoxy resin is arbitrary, and they are dissolved separately in acetone and then mixed together.

[0019] The polyether-based nonionic emulsifier is at least one of polyoxyethylene ether, polyoxyethylene ester, or polyoxyethylene polyol ester; the EO addition number of the polyether-based nonionic emulsifier is 3-40, preferably at least one of lauryl alcohol, 1214 alcohol, 1618 alcohol, oleyl alcohol, lauric acid, palmitic acid, stearic acid, oleic acid, ricinoleic acid, fatty acid glycerides, or fatty acid sorbitol esters.

[0020] The polyether nonionic emulsifier is at least one of the following: higher fatty alcohols, higher fatty acids, ethoxylated polymers of fatty acid polyol esters or their ethoxylated-propoxylated random or block copolyethers, with an EO addition number of 9-40.

[0021] The higher fatty alcohol is at least one of lauryl alcohol, 1214 alcohol, 1618 alcohol, and oleyl alcohol, and the higher fatty acid is at least one of lauric acid, palmitic acid, stearic acid, oleic acid, and ricinoleic acid.

[0022] The fatty acid ester smoothing agent is one or more of higher fatty alcohols, fatty acid monoesters or diesters, and fatty acid polyol esters; the polyol is at least one of pentaerythritol, sorbitol, glycerol, or polyethylene glycol.

[0023] The total mass percentage of the polyether nonionic emulsifier and fatty acid ester smoother shall not exceed 10%.

[0024] The residual weight loss of the sizing agent at 400°C is more than 30%, preferably 50-70%.

[0025] Secondly, the present invention provides a method for preparing the above-mentioned high-temperature resistant self-emulsifying water-soluble epoxy resin-based carbon fiber sizing agent, the preparation method comprising the following steps:

[0026] Step 1: Preparation of high-temperature resistant, self-emulsifying, water-soluble epoxy resin using in-situ blending phosphorylation modification technology:

[0027] A mixture of two epoxy resins with different epoxy values ​​was dissolved evenly in acetone and added to a reactor. Phosphoric acid was then added in batches. After the addition was complete, the phosphorylation reaction temperature was controlled between 30-70℃, and the reaction was carried out for 1-3 hours. The temperature was then raised to 75℃, and deionized water was added in batches. After the addition was complete, a hydrolysis reaction was carried out for 1.5-3 hours. Subsequently, potassium hydroxide aqueous solution was added in batches. After the addition was complete, the neutralization reaction temperature was controlled between 80-90℃, and the reaction was carried out for another 1.5-3 hours. After the reaction was completed, the mixture was cooled and discharged to obtain in-situ blended phosphorylated modified water-soluble bisphenol A type epoxy resin.

[0028] Step 2: Formulation of the sizing agent:

[0029] In situ blended phosphorylated modified water-soluble bisphenol A epoxy resin, polyether nonionic emulsifier, fatty acid ester smoother and other additives are precisely metered and added to deionized water, dispersed at high speed of 5000-20000 rpm for 30-120 min, cooled to room temperature and discharged, which is the high-temperature resistant self-emulsifying water-soluble epoxy resin-based carbon fiber sizing agent.

[0030] The phosphoric acid is fed in 6-9 batches. When feeding, the next batch should be fed only after the previous batch has completely reacted. The molar ratio of phosphoric acid to epoxy is 1:(1-1.2). The phosphorylation reaction temperature is 40-55℃ and the reaction time is 2.5h.

[0031] The deionized water is added in batches of 5-10; the mass ratio of deionized water to phosphoric acid is (2-2.5):1; the hydrolysis reaction time is 2 hours.

[0032] The potassium hydroxide aqueous solution is added in batches of 5-10; the neutralization reaction temperature is 80-90℃, and the reaction time is 2h.

[0033] The average particle size of the in-situ blended phosphorylation modified water-soluble bisphenol A type epoxy resin is no greater than 20 nm, and the performance indicators of the aqueous solution of the in-situ blended phosphorylation modified water-soluble bisphenol A type epoxy resin are as follows:

[0034] 1) Stability: The 1% emulsion remained stable without stratification after centrifugation at 4000 rpm for 30 minutes; the finished product remained stable without stratification for 6 months.

[0035] 2) Surface activity: 1% emulsion at 25℃, surface tension is 46-50 mN / m;

[0036] The performance indicators of the high-temperature resistant, self-emulsifying, water-soluble epoxy resin-based carbon fiber sizing agent are as follows:

[0037] (1) The solid content is adjusted within the range of 15-50%;

[0038] (2) Water solubility: It has self-emulsifying properties, good water solubility, small particle size, and can be miscible with water in any proportion to prepare a uniform, transparent colloidal solution or milky white emulsion with blue fluorescence.

[0039] (3) pH value: 1% emulsion, 25℃, pH value is 7-9;

[0040] (4) Surface activity: 1% emulsion, 25℃, surface tension is 25-35mN / m;

[0041] (5) Viscosity: 1% emulsion, 25℃, viscosity <10cp;

[0042] (6) Stability: 1% emulsion is stable without separation after 48 hours; finished product is stable without separation after 180 days.

[0043] Thirdly, this invention also protects a carbon fiber, which is sized using the sizing agent described above or the sizing agent obtained by the preparation method described above, wherein the surface oxygen content after sizing is above 19%, and the surface free energy of the sized carbon fiber is greater than 40 mJ / m. 2 Its surface energy is close to that of epoxy resin, which is beneficial for the wetting and bonding of the matrix resin to the carbon fiber surface during the molding of epoxy resin-based carbon fiber composites, thereby improving interfacial adhesion and interlaminar shear strength.

[0044] Fourthly, the present invention provides an application in which the sizing agent described above or the sizing agent obtained by the preparation method is used for sizing in the manufacture of composite materials.

[0045] Compared with the prior art, the beneficial effects of the present invention are:

[0046] Compared with traditional solvent-based epoxy resin sizing agents and emulsion-based epoxy resin sizing agents, the high-temperature resistant, self-emulsifying, water-soluble epoxy resin-based carbon fiber sizing agent of this invention exhibits superior performance:

[0047] (1) Good water solubility. It has the characteristic of self-emulsification and can be miscible with water in any proportion;

[0048] (2) Good stability. A 1% concentration sizing agent emulsion remained stable and did not separate after centrifugation at 4000 rpm for 30 min; the average particle size was small and the distribution was narrow, reaching the level of a colloidal solution; the finished sizing agent remained homogeneous and stable for 6 months;

[0049] (3) After sizing, the surface free energy of carbon fiber is moderate, which is conducive to the wetting and impregnation of carbon fiber by epoxy resin. Carbon fiber has good smoothness, bundling, stiffness and softness, and good processability.

[0050] (4) The low amount of surfactant in the sizing agent formulation reduces the possible high-temperature oxidative degradation, weak layer and stress defects of carbon fiber sizing film and composite material interface layer.

[0051] (5) The main film-forming agent is a blended composite modified epoxy resin phosphate ester prepared by in-situ phosphorylation technology. The modified epoxy resin phosphate ester prepared by in-situ blending technology overcomes the shortcomings of the single polymer component and endows the sizing agent with excellent comprehensive properties.

[0052] In-situ blending and phosphorylation modification of epoxy resins with different epoxy values ​​can complement each other, regulate each other, and achieve synergistic enhancement effects. Epoxy resins with high epoxy values ​​have a high content of active epoxy groups and good reactivity, resulting in a high phosphate ester conversion rate during phosphorylation. However, the reaction is intense and difficult to control. Resins with low epoxy values ​​have high molecular weight, high cohesive energy, and good film-forming and mechanical properties. However, due to their low epoxy values, they have low reactivity when reacting with phosphoric acid, resulting in a low degree of phosphate ester conversion during phosphorylation. The introduction of hydrophilic groups is also more difficult, and the product is solid at room temperature and requires heating to dissolve in water.

[0053] The phosphorylated resin obtained by in-situ blending modification has undergone sufficient in-situ mixing in the dissolution, melting, and dispersion stages at the beginning of the reaction. The macromolecular chains are fully diffused and fused together, becoming one during the phosphorylation, hydrolysis, and neutralization processes. The degree of reaction is relatively uniform, which is conducive to the retention of some epoxy groups in high epoxy value resins and the full phosphorylation reaction of low epoxy value resins. After the reaction products are fully fused, the modified resin formed has self-emulsifying properties, good water solubility, uniform and stable solution, small particle size, and significantly improved mechanical properties and high temperature resistance. This is beneficial for obtaining carbon fiber sizing agents with better overall performance.

[0054] (6) The carbon fiber sizing agent of the present invention also has the advantages of high temperature resistance, low toxicity, environmental protection, no odor and convenient use. Attached Figure Description

[0055] Figure 1 The images show the morphology of the carbon fiber surface before and after treatment with emulsions of different concentrations of carbon fiber sizing agent in Example 1 of this invention, where (a) is a sizing agent concentration of 0.5%; (b) is a sizing agent concentration of 1%; and (c) is a sizing agent concentration of 2%.

[0056] Figure 2 The particle size distribution diagrams of the in-situ blended phosphorylated modified water-soluble bisphenol A epoxy resin and the 1% emulsion of high-temperature resistant waterborne carbon fiber sizing agent prepared in Example 2 of the present invention are shown, wherein (a) is the particle size distribution diagram of the 1% emulsion of in-situ blended bisphenol A epoxy resin phosphate ester, and (b) is the particle size distribution diagram of the 1% emulsion of high-temperature resistant waterborne carbon fiber sizing agent.

[0057] Figure 3 This is a thermogravimetric analysis curve for Example 1.

[0058] Figure 4 This is a thermogravimetric analysis curve for Example 2.

[0059] Figure 5 This is a thermogravimetric analysis curve for Example 3. Detailed Implementation

[0060] The present invention will be further explained below with reference to the embodiments and accompanying drawings, but the present invention is not intended to limit the scope of protection of this application.

[0061] This invention uses high-temperature resistant, self-emulsifying, water-soluble bisphenol A epoxy resin phosphate salt, modified by in-situ blending technology, as the main component, and adds a small amount of surfactants, additives, etc. to prepare a sizing agent of appropriate concentration.

[0062] The high-temperature resistant, self-emulsifying, water-soluble epoxy resin-based carbon fiber sizing agent of this invention has the following composition by weight percentage:

[0063]

[0064] The sum of the percentages of the above components is 100% by weight.

[0065] The in-situ blended phosphorylation modified water-soluble bisphenol A type epoxy resin is obtained by in-situ blending and phosphorylation modification of any two of bisphenol A epoxy resins E-20, E-35, E-42, and E-44 in any proportion, and has the characteristics of self-emulsification, good water solubility, and high temperature resistance. The in-situ blended phosphorylation modified water-soluble bisphenol A type epoxy resin includes two epoxy resins: a low epoxy value high molecular weight epoxy resin and a high epoxy value low molecular weight epoxy resin, with the epoxy values ​​of the two selected epoxy resins differing by 15-30 mmol / g.

[0066] The low epoxy value high molecular weight epoxy resin can be at least one of E20, E-35, etc., and the high epoxy value low molecular weight epoxy resin can be at least one of E-42, E44, etc.; the mixing ratio of the low epoxy value high molecular weight epoxy resin and the high epoxy value low molecular weight epoxy resin is arbitrary, and they are dissolved separately with acetone and then mixed together.

[0067] The polyether-based nonionic emulsifier is at least one of the following: higher fatty alcohols, higher fatty acids, ethoxylated polymers of fatty acid polyol esters, or their ethoxylated-propoxylated random or block coethers, with an EO addition number (ethylene oxide addition number) of 9-40; furthermore, the higher fatty alcohol is at least one of lauryl alcohol, 1214 alcohol, 1618 alcohol, oleyl alcohol, etc., and the higher fatty acid is at least one of lauric acid, palmitic acid, stearic acid, oleic acid, ricinoleic acid, etc.

[0068] The fatty acid ester smoothing agent is one or more of higher fatty alcohols, fatty acid monoesters or diesters, and fatty acid polyol esters. Further, the fatty acids and fatty alcohols are as described above, and the polyol is at least one of pentaerythritol, sorbitol, glycerol, and polyethylene glycol.

[0069] The other additives are at least one of defoamers and antioxidants. The emulsifiers and smoothers selected in the sizing agent formulation may be specifically chosen based on their heat resistance and foaming properties, and their mass percentage shall not exceed 1%.

[0070] Furthermore, the total mass percentage of the polyether nonionic emulsifier and the fatty acid ester smoother does not exceed 10%.

[0071] The preparation method of the sizing agent consists of two steps, as follows:

[0072] Step 1: Preparation of high-temperature resistant, self-emulsifying, water-soluble epoxy resin using in-situ blending and phosphorylation modification technology.

[0073] A mixture of acetone solutions of two epoxy resins with different epoxy values ​​was added to a reactor. The mixture was heated and stirred until homogeneous, then heating was stopped, stirring continued, and the mixture was aged for 1-2 hours. Phosphoric acid was then added in batches at 30°C. After the addition was complete, the reaction temperature was controlled between 30-70°C, and the reaction was allowed to proceed for 1-3 hours. The conversion rate of phosphate ester increased with increasing reaction time. The temperature was then raised to 75°C, and deionized water was added in batches. After the addition was complete, a hydrolysis reaction was carried out for 1.5-3 hours. Subsequently, potassium hydroxide aqueous solution was added in batches. After the addition was complete, the temperature was controlled between 80-90°C, and the reaction continued for 1.5-3 hours. After the reaction was completed, the mixture was cooled and discharged to obtain the target product—in-situ blended phosphorylated modified water-soluble bisphenol A type epoxy resin.

[0074] The two epoxy resins with different epoxy values ​​are a mixture of any two of bisphenol A epoxy resins E-44, E-42, E-35, and E-20, and the mixing ratio can be any ratio.

[0075] The phosphoric acid is fed in 6-9 batches. When feeding, the next batch should be fed only after the previous batch has basically reacted completely. The molar ratio of phosphoric acid to epoxy is 1:(0.5-1.5), preferably 1:(1-1.2). The phosphorylation reaction temperature is 30-70℃, preferably 40-55℃, and the reaction time is preferably 2.5h.

[0076] The batches of deionized water fed are 5-10; the mass ratio of deionized water to phosphoric acid is (1.5-2.5):1, preferably (2-2.5):1; the hydrolysis reaction time is preferably 2 hours.

[0077] The potassium hydroxide aqueous solution is fed in batches of 5-10; the mass ratio of potassium hydroxide to phosphoric acid is 1:(1-1.1); the concentration of potassium hydroxide solution is 20%-30%; the neutralization reaction temperature is 80-90℃, and the reaction time is preferably 2h.

[0078] The in-situ blended phosphorylation modified water-soluble bisphenol A epoxy resin has a pH value of 7-9, excellent water solubility, and extremely small emulsion particle size, ranging from tens to hundreds of nanometers; a 1% emulsion remains stable and does not separate after centrifugation at 4000 rpm for 30 minutes; and a 1% emulsion has a surface tension of 46-50 mN / m at 25°C.

[0079] The high-temperature resistant in-situ blended phosphorylation modified water-soluble bisphenol A epoxy resin prepared by the method of the present invention is a latex-like substance with excellent self-emulsifying properties. It can be miscible with water in any proportion to obtain a uniform, stable, blue fluorescent hydrosol with small particle size and an average particle size of no more than 20 nm.

[0080] Step 2: Formulation of the sizing agent:

[0081] In situ blended phosphorylated modified water-soluble bisphenol A epoxy resin, polyether nonionic emulsifier, fatty acid ester smoother and other additives are precisely metered and added to deionized water, dispersed at high speed of 5000-20000 rpm for 30-120 min, cooled to room temperature and discharged, which is the high-temperature resistant self-emulsifying water-soluble epoxy resin-based carbon fiber sizing agent.

[0082] The high-temperature resistant, self-emulsifying, water-soluble epoxy resin-based carbon fiber sizing agent of the present invention also has the following characteristics:

[0083] (7) The solid content can be adjusted within the range of 15-50%. According to the carbon fiber sizing process and performance requirements, the proportion range of each functional component in the sizing agent formulation can be adjusted to obtain a finished sizing agent with suitable viscosity and good wetting properties.

[0084] (8) Water solubility: The sizing agent prepared by the present invention has self-emulsifying properties, good water solubility, and small particle size. It can be miscible with water in any proportion to obtain a uniform, transparent colloidal solution with blue fluorescence or a milky white emulsion. When the sizing agent of the present invention is prepared into aqueous dispersions of different concentrations, the color changes from grayish semi-transparent (particle size of about ten nanometers) to a colloidal solution with blue fluorescence. As the solid content further increases, it gradually becomes a milky white emulsion.

[0085] (9) pH value: 1% emulsion, 25℃, pH value is 7-9.

[0086] (10) Surface activity: 1% emulsion, 25℃, surface tension is 25-35mN / m.

[0087] (11) Viscosity: 1% emulsion, 25℃, viscosity <10cp.

[0088] (12) Stability: 1% emulsion is stable without separation after 48 hours; finished product is stable without separation after 180 days.

[0089] The high-temperature resistant, self-emulsifying, water-soluble epoxy resin-based carbon fiber sizing agent of the present invention has a residual weight loss of more than 30% at 400℃, preferably 50-70%; and the surface oxygen content of the carbon fiber after sizing is more than 19%.

[0090] In the following examples, the phosphoric acid used was concentrated phosphoric acid with a mass concentration of 85%, and the KOH aqueous solution used was KOH aqueous solution with a mass concentration of 30%.

[0091] Example 1

[0092] Step 1: Add 20g of epoxy resin E-20 and 20ml of acetone to a four-necked flask (equipped with a thermometer and condenser), heat to 50℃, and stir to dissolve. Add 80g of epoxy resin E44 and 40ml of acetone to a beaker, stir until homogeneous, and then pour into the four-necked flask. Add phosphoric acid in 6 portions, with a molar ratio of phosphoric acid to epoxy resin of 1:1.2. After the addition is complete, maintain the reaction temperature at 40℃ for 2.5 hours. Then heat to 75℃ and add deionized water in 8 portions, with a mass ratio of deionized water to phosphoric acid of 2.5:1, for 2 hours. Finally, heat to 80℃ and add 30wt% KOH aqueous solution in 8 portions for neutralization, with a mass ratio of potassium hydroxide to phosphoric acid of 1:1, for 2 hours. After the reaction, the pH of the solution is 8.2. The product obtained is the in-situ blended phosphoric acid modified water-soluble bisphenol A type epoxy resin. The product contains 42% by mass of potassium phosphate salt of phosphoric acid-modified blended epoxy resin. Dissolving the potassium phosphate salt of phosphoric acid-modified blended epoxy resin obtained in this example in deionized water yields an in-situ blended phosphorylated modified water-soluble bisphenol A type epoxy resin emulsion.

[0093] Step 2: Add 14.47g of in-situ blended phosphorylated modified water-soluble bisphenol A epoxy resin, 3g of polyether nonionic surfactant, and 0.03g of other additives to 12.5g of deionized water, and disperse at room temperature and 15000rpm for 30min to obtain a high-temperature resistant self-emulsifying water-soluble epoxy resin-based carbon fiber sizing agent with a solid content of 30%.

[0094] This sizing agent has excellent high-temperature resistance, with the fastest decomposition temperature at 365℃, a residual weight loss of 64.74% at 400℃, 34.96% at 500℃, and 28.26% at 600℃.

[0095] The surface morphology of carbon fibers after sizing with different concentrations of sizing solution is as follows: Figure 1 As shown.

[0096] At 25℃, the surface tension of the sizing agent was measured to be 31.6 mN / m (1% emulsion). After sizing with a 2% concentration of sizing agent, a uniform and dense film was formed on the carbon fiber surface, with an sizing agent adhesion of 1.07%. The film exhibited high strength, and the carbon fiber after sizing showed abrasion resistance greater than 1000 cycles, a stiffness of 9.5 cm, and a surface oxygen content of 23.7%. The interlaminar shear strength increased from 67.4 MPa (without sizing) to 87.1 MPa, an increase of 29.2%. The surface energy of the carbon fiber increased to 49.53 mJ / m after sizing. 2 The surface energy of unsized carbon fiber is 38.08 mJ / m. 2 Compared to the previous method, this improvement is significant and facilitates the wetting and spreading of the matrix epoxy resin on the carbon fiber surface during the preparation of composite materials, thereby enhancing the interfacial adhesion and interfacial shear strength of the composite materials.

[0097] Example 2

[0098] Step 1: Add 50g of epoxy resin E-20 and 30ml of acetone to a four-necked flask (equipped with a thermometer and condenser), heat to 50℃, and stir to dissolve. Add 50g of epoxy resin E44 and 30ml of acetone to a beaker, stir until homogeneous, and then pour into the four-necked flask. Add phosphoric acid in 6 portions, with a molar ratio of phosphoric acid to epoxy resin of 1:1.2. After the addition is complete, maintain the reaction temperature at 40℃ for 3 hours. Then heat to 75℃ and add deionized water in 8 portions, with a mass ratio of deionized water to phosphoric acid of 2.5:1, for 2 hours. Finally, heat to 80℃ and add 30wt% KOH aqueous solution in 8 portions for neutralization, with a mass ratio of potassium hydroxide to phosphoric acid of 1:1, for 2 hours. The pH of the product after the reaction is complete is 8.56. This product is the in-situ blended phosphoric acid modified water-soluble bisphenol A type epoxy resin. The product has a mass concentration of 49%. The potassium phosphate salt of the phosphoric acid-modified blended epoxy resin obtained in this example is dissolved in deionized water to obtain an in-situ blended phosphorylated modified water-soluble bisphenol A type epoxy resin emulsion.

[0099] Step 2: 32.68g of in-situ blended phosphorylated modified water-soluble bisphenol A epoxy resin, 4.17g of polyoxyethylene nonionic surfactant, and 0.5g of other additives were added to 13.1g of deionized water. The mixture was dispersed at room temperature and 10,000 rpm for 20 minutes under high-speed shearing to obtain a high-temperature resistant, self-emulsifying, water-soluble epoxy resin-based carbon fiber sizing agent with a solid content of 41%. At 25℃, the surface tension of this sizing agent was measured to be 34.52 mN / m (1% emulsion). After sizing carbon fibers with 1% of the sizing agent, the resulting CF exhibited abrasion resistance greater than 1000 cycles, an interlaminar shear strength of 83.5 MPa, a stiffness of 10 cm, a surface oxygen content of 21.9%, and a surface energy of 46.06 mJ / m. 2The nonpolar surface energy component is 16.43 mJ / m. 2 The polar surface energy component is 29.63 mJ / m 2 .

[0100] This sizing agent has excellent high-temperature resistance, with the fastest decomposition temperature at 366℃, a residual weight loss of 59.34% at 400℃, 34.22% at 500℃, and 25.58% at 600℃.

[0101] Example 3

[0102] Step 1: Add 80g of epoxy resin E-20 and 40ml of acetone to a four-necked flask (equipped with a thermometer and condenser), heat to 50℃, and stir to dissolve. Add 20g of epoxy resin E42 and 20ml of acetone to a beaker, stir until well mixed, and then pour into the four-necked flask. Add phosphoric acid in 5 portions, with a molar ratio of phosphoric acid to epoxy resin of 1:1.15. After the addition is complete, maintain the reaction temperature at 60℃ for 2 hours. Then heat to 75℃ and add deionized water in 8 portions, with a mass ratio of deionized water to phosphoric acid of 2:1, for 2 hours each time. Finally, the temperature was raised to 80℃, and 30wt% KOH solution was added in eight portions for neutralization. The mass ratio of potassium hydroxide to phosphoric acid was 1:1.05, and the reaction time was 2 hours. After the reaction, the pH of the solution was 9.0. The obtained product was soluble in deionized water, and this product is the in-situ blended phosphoric acid modified water-soluble bisphenol A type epoxy resin. The mass concentration of potassium phosphate ester in the phosphoric acid modified blended epoxy resin in this product was 57%. The potassium phosphate ester obtained from this example was dissolved in deionized water to obtain the in-situ blended phosphoric acid modified water-soluble bisphenol A type epoxy resin emulsion.

[0103] 30.98g of in-situ blended phosphorylated modified water-soluble bisphenol A epoxy resin, 4.17g of polyoxyethylene nonionic surfactant, and 0.05g of other additives were added to 14.8g of deionized water and dispersed at room temperature and 10,000 rpm for 30 min under high-speed shear for 30 min to obtain a water-based high-performance sizing agent with a solid content of 43%. At 25℃, the surface tension of this sizing agent was measured to be 32.13 mN / m (1%). After sizing carbon fibers with 1% of the sizing agent, the resulting CF fibers exhibited abrasion resistance greater than 1000 cycles, an interlaminar shear strength of 79.2 MPa, a stiffness of 8 cm, a surface oxygen content of 19.5%, and a surface energy of 45.27 mJ / m. 2 The nonpolar surface energy component is 16.88 mJ / m. 2 The polar surface energy component is 28.39 mJ / m 2 .

[0104] This sizing agent has excellent high-temperature resistance. The decomposition temperature at 5% is 213℃, the fastest decomposition temperature is 343℃, the residual weight loss at 400℃ is 64.78%, the residual weight loss at 500℃ is 29.34%, and the residual weight loss at 600℃ is 19.60%.

[0105] The epoxy resin conversion rate described in the above embodiments is 40%-70%, and the solid content of the sizing agent is 15-50%. Using the preparation method of this invention, different types of in-situ blended epoxy resin phosphate salts can be prepared. By changing the epoxy value, mixing ratio, reaction temperature, reaction time, and feed ratio of the epoxy resin, high-temperature resistant, self-emulsifying, water-soluble, in-situ blended modified bisphenol A epoxy resin phosphates with different conversion rates, mass concentrations, pH values, particle sizes, and surface activities can be obtained. Using the prepared in-situ blended phosphorylated modified water-soluble bisphenol A epoxy resin as the main body, and adding the surfactants, additives, and other functional components described in this invention, the target sizing agent can be obtained.

[0106] The above description is only a preferred embodiment of the present invention. Any changes, substitutions or reorganizations that can be easily obtained by combining them within the scope of the technology disclosed in the present invention should be covered within the protection scope of the present invention.

[0107] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A high-temperature resistant, self-emulsifying, water-soluble epoxy resin-based carbon fiber sizing agent, characterized in that, The sizing agent has the following composition by mass percentage: In-situ blending of phosphorylated modified water-soluble bisphenol A type epoxy resin (10-40%); 3-5% polyether nonionic emulsifier; Fatty acid ester smoothing agents 1-5%; Other additives shall not exceed 1%; Deionized water balance; The other additives are at least one of antioxidants and defoamers; The in-situ blended phosphorylation modified water-soluble bisphenol A type epoxy resin includes two epoxy resins: a low epoxy value high molecular weight epoxy resin and a high epoxy value low molecular weight epoxy resin. The low epoxy value high molecular weight epoxy resin is E20, and the high epoxy value low molecular weight epoxy resin is at least one of E-42 and E44. During preparation, the two epoxy resins are mixed and dissolved evenly, and then phosphoric acid is added in batches. After the addition is complete, the reaction continues for 1-3 hours. Then, the temperature is raised, and deionized water is added in batches to form a monophosphate ester. Finally, potassium hydroxide aqueous solution is added in batches, allowing the reaction to proceed fully, and the pH of the solution is controlled to be 7-9 after the reaction. The molar ratio of phosphoric acid to the total epoxy value of the epoxy resin is 1:(0.5-1.5), the mass ratio of deionized water to phosphoric acid is (1.5-2.5):1, the mass ratio of potassium hydroxide to phosphoric acid is 1:(1-1.1), and the mass concentration of the potassium hydroxide aqueous solution is 20%-30%.

2. The sizing agent according to claim 1, characterized in that, When mixing the low-epoxy-value high-molecular-weight epoxy resin and the high-epoxy-value low-molecular-weight epoxy resin, they are dissolved separately in acetone before being mixed together.

3. The sizing agent according to claim 1, characterized in that, The polyether-based nonionic emulsifier is at least one of polyoxyethylene ether, polyoxyethylene ester, and polyoxyethylene polyol ester; the EO addition number of the polyether-based nonionic emulsifier is 3-40; or, the polyether-based nonionic emulsifier is at least one of higher fatty alcohols, higher fatty acids, ethoxylated polymers of fatty acid polyol esters, or ethoxylated-propoxylated random or block coethers thereof, and its EO addition number is 9-40.

4. The sizing agent according to claim 3, characterized in that, The higher fatty alcohol is at least one of lauryl alcohol, 1214 alcohol, 1618 alcohol, and oleyl alcohol, and the higher fatty acid is at least one of lauric acid, palmitic acid, stearic acid, oleic acid, and ricinoleic acid. The fatty acid ester smoothing agent is one or more of higher fatty alcohols, fatty acid monoesters or dieesters and fatty acid polyol esters; the polyol is at least one of pentaerythritol, sorbitol, glycerol or polyethylene glycol. The total mass percentage of the polyether nonionic emulsifier and fatty acid ester smoother shall not exceed 10%.

5. The sizing agent according to claim 1, characterized in that, The residual weight loss of the sizing agent at 400℃ is more than 30%.

6. The sizing agent according to claim 5, characterized in that, The residual weight loss of the sizing agent at 400℃ is 50-70%.

7. A method for preparing a high-temperature resistant, self-emulsifying, water-soluble epoxy resin-based carbon fiber sizing agent, characterized in that, The preparation method includes the following steps: Step 1: Preparation of high-temperature resistant, self-emulsifying, water-soluble epoxy resin using in-situ blending and phosphorylation modification technology. A mixture of two epoxy resins with different epoxy values ​​was dissolved evenly in acetone and added to a reactor. Phosphoric acid was then added in batches. After the addition was complete, the phosphorylation reaction temperature was controlled between 30-70℃, and the reaction was allowed to proceed for 1-3 hours. The temperature was then raised to 75℃, and deionized water was added in batches. After the addition was complete, a hydrolysis reaction was carried out for 1.5-3 hours. Subsequently, potassium hydroxide aqueous solution was added in batches. After the addition was complete, the neutralization reaction temperature was controlled between 80-90℃, and the reaction was allowed to continue for 1.5-3 hours. The reaction was allowed to proceed until the pH of the solution was controlled to be 7-9. After the reaction was completed, the solution was cooled and discharged to obtain in-situ blended phosphorylated modified water-soluble bisphenol A type epoxy resin. The two epoxy resins with different epoxy values ​​were a low-epoxy-value high-molecular-weight epoxy resin and a high-epoxy-value low-molecular-weight epoxy resin. The low-epoxy-value high-molecular-weight epoxy resin was E20, and the high-epoxy-value low-molecular-weight epoxy resin was at least one of E-42 and E44. The molar ratio of phosphoric acid to the total epoxy value of epoxy resin is 1:(0.5-1.5), the mass ratio of deionized water to phosphoric acid is (1.5-2.5):1, the mass ratio of potassium hydroxide to phosphoric acid is 1:(1-1.1), and the mass concentration of potassium hydroxide aqueous solution is 20%-30%. Step 2: Formulation of the sizing agent: In situ blended phosphorylated modified water-soluble bisphenol A epoxy resin, polyether nonionic emulsifier, fatty acid ester smoother and other additives are precisely metered and added to deionized water, dispersed at high speed of 5000-20000 rpm for 30-120 min, cooled to room temperature and discharged, which is the high-temperature resistant self-emulsifying water-soluble epoxy resin-based carbon fiber sizing agent.

8. The preparation method according to claim 7, characterized in that, The phosphoric acid is fed in 6-9 batches. When feeding, the next batch should be fed only after the previous batch has completely reacted. The molar ratio of phosphoric acid to epoxy is 1:(1-1.2). The phosphorylation reaction temperature is 40-55℃ and the reaction time is 2.5h. The deionized water is added in batches of 5-10; the mass ratio of deionized water to phosphoric acid is (2-2.5):1; the hydrolysis reaction time is 2 hours. The potassium hydroxide aqueous solution is added in batches of 5-10; the neutralization reaction temperature is 80-90℃, and the reaction time is 2h.

9. The preparation method according to claim 7, characterized in that, The average particle size of the in-situ blended phosphorylation modified water-soluble bisphenol A type epoxy resin is no greater than 20 nm, and the performance indicators of the aqueous solution of the in-situ blended phosphorylation modified water-soluble bisphenol A type epoxy resin are as follows: 1) Stability: The 1% emulsion remained stable without stratification after centrifugation at 4000 rpm for 30 minutes; the finished product remained stable without stratification for 6 months. 2) Surface activity: 1% emulsion at 25℃, surface tension is 46-50 mN / m; The performance indicators of the high-temperature resistant, self-emulsifying, water-soluble epoxy resin-based carbon fiber sizing agent are as follows: (1) The solid content is adjusted within the range of 15-50%; (2) Water solubility: It has self-emulsifying properties, good water solubility, small particle size, and can be miscible with water in any proportion to prepare a uniform, transparent colloidal solution or milky white emulsion with blue fluorescence. (3) pH value: 1% emulsion, 25℃, pH value is 7-9; (4) Surface activity: 1% emulsion, 25℃, surface tension is 25-35mN / m; (5) Viscosity: 1% emulsion, 25℃, viscosity <10cp; (6) Stability: 1% emulsion is stable without separation after 48 hours; finished product is stable without separation after 180 days.

10. A carbon fiber, characterized in that, The carbon fibers are sized using the sizing agent according to any one of claims 1-6 or the sizing agent obtained by any one of the preparation methods according to claims 7-9. After sizing, the surface oxygen content of the carbon fibers is greater than 19%, and the surface free energy of the sized carbon fibers is greater than 40 mJ / m. 2 .

11. An application characterized in that, The sizing agent described in any one of claims 1-6 or the sizing agent obtained by any one of the preparation methods described in claims 7-9 is used for sizing in the manufacture of composite materials.

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