A high-temperature resistant water-based sizing agent for carbon fiber, and its preparation method and application

Abstract

The present invention discloses a high-temperature resistant water-based sizing agent for carbon fiber, and its preparation method and application, which belong to the field of materials. The water-based sizing agent provided by the present invention includes a main sizing material and a functional additive; the main sizing material is a water-soluble polyamic acid salt; the functional additive is a water-soluble surfactant or epoxy resin; the mass of the functional additive accounts for 0 to 10% of the total mass of the main sizing material and the functional additive. The carbon fiber sized with the water-based sizing agent of the present invention has the advantages of good wear resistance and low fuzzing; at the same time, the sized carbon fiber has good temperature resistance, can withstand the processing temperature of thermosetting polyimide resin>350°C, and can be used to prepare high-performance polyimide composite materials.

Description

Technical Field

[0001] The present invention relates to the field of materials, and in particular to a high-temperature resistant water-based sizing agent for carbon fiber, a preparation method thereof, and an application thereof. Background Art

[0002] As an inorganic polymer specialty fiber, polyacrylonitrile carbon fiber is an ideal reinforcement for composite materials, boasting high specific strength and modulus. Carbon fiber also possesses electrical and thermal conductivity, high-temperature resistance, and corrosion resistance, making it valuable for applications in aerospace, transportation, energy, healthcare, and sporting goods.

[0003] Carbon fiber needs to be surface treated in practical applications. Because carbon fiber is a brittle material, it is easy to produce fuzz and single filament breakage due to mechanical friction during subsequent weaving and processing. The fiber strength is reduced, which also leads to a decline and stagnation in production and processing efficiency. In the process of preparing carbon fiber prepreg, the presence of fuzz also makes it difficult for the matrix resin to fully impregnate the carbon fiber, resulting in a large porosity in the prepared composite material, which affects the performance of the composite material. Usually, the surface of the carbon fiber is sizing treated to form a protective film on the surface of the carbon fiber, thereby improving the bundling and wear resistance of the carbon fiber bundle and reducing the amount of fiber fuzzing. At the same time, the slurry can constitute the interface layer of the composite material, increase the interfacial bonding effect of the composite material, and improve the performance of the composite material.

[0004] Traditional carbon fiber sizing agents use epoxy resin and polyurethane as sizing agents, and the sized carbon fibers are mainly used in epoxy resin composites for low-temperature use. However, when used in high-temperature resistant composite materials such as polyimide and polyetheretherketone, traditional sizing agents are prone to degradation at high processing temperatures (>300°C) and high operating temperatures, affecting the cross-sectional bonding of the composite materials, thereby reducing the mechanical properties of the composite materials at high temperatures. In recent years, researchers have begun to focus on the development of sizing agents suitable for high-temperature resistant carbon fiber composite materials. CN100999867A uses a mixture of thermoplastic polyimide and glycidyl ether to prepare an emulsion-type sizing agent. The sizing agent has good stability, and the carbon fibers after sizing have good wear resistance and strong interfacial adhesion with bismaleimide resins. However, JP2014125688 also uses a mixture of polyimide with hydroxyl or carboxyl groups and epoxy resins such as bisphenol A glycidyl ether and phenolic glycidyl ether to prepare a solvent-based sizing agent. After sizing, the carbon fibers have less thermal weight loss and high interfacial adhesion with the matrix resin. CN107022901A mixes polyamide-imide with epoxy resin to produce a water-based carbon fiber sizing agent. This sizing agent is suitable for the preparation of carbon fiber composites based on high-temperature-resistant resins such as polyetheretherketone, polyimide, and polyphenylene sulfide. However, the epoxy resin used in these sizing agents accounts for approximately 50% of the main sizing material, and a significant proportion of the sizing material degrades before reaching 200°C, failing to meet the processing and use requirements of high-temperature-resistant composite materials such as polyimide and polyetheretherketone.

[0005] Invention Disclosure

[0006] The present invention provides a high-temperature resistant water-based sizing agent for carbon fiber, a preparation method and an application thereof. The water-based sizing agent of the present invention has low cost, good temperature resistance, and can withstand the processing temperature of thermosetting polyimide resin greater than 350°C.

[0007] The present invention first provides a water-based sizing agent, comprising a main sizing material and a functional additive;

[0008] The main slurry is a water-soluble polyamic acid salt;

[0009] The functional additive is a water-soluble surfactant or an epoxy resin;

[0010] The mass of the functional additive accounts for 0 to 10% of the total mass of the main slurry and the functional additive; specifically, it can be 1% to 10%.

[0011] The above-mentioned aqueous sizing agent also includes water;

[0012] The solid content of the aqueous sizing agent is 0.5 wt% to 2 wt%, and can be specifically 1 wt%.

[0013] The solid content in the aqueous sizing agent refers to the percentage of the sum of the mass of the main slurry and the functional additives to the total mass of the sizing agent solution.

[0014] The above-mentioned aqueous sizing agent also includes a cosolvent, specifically triethylamine, which is used to help dissolve the main slurry; the mass ratio of water to triethylamine is 40 to 50:1, specifically 45 to 50:1.

[0015] In the above-mentioned aqueous sizing agent, when the functional additive is a water-soluble surfactant, the mass of the surfactant accounts for 1% to 10% of the total mass of the main slurry and the surfactant; specifically, it can be 1% or 9%;

[0016] When the functional additive is epoxy resin, the water-based sizing agent further comprises an emulsifier; the mass of the epoxy resin accounts for 2.5% to 10% of the total mass of the main slurry and the epoxy resin; specifically, it can be 2.5%, 5%, 7.5% or 10%;

[0017] The mass ratio of the epoxy resin to the emulsifier is 8:3 to 8:5;

[0018] Specifically, the emulsifier is at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

[0019] In the above-mentioned aqueous sizing agent, the water-soluble surfactant is at least one of a penetrant JFC-1, a cationic surfactant 31524 (cationic surfactant propylene bis (tetradecyl dimethyl ammonium chloride)) and polyethylene glycol monooleate;

[0020] The polyethylene glycol monooleate is polyethylene glycol 400 monooleate (PEG400MO) and / or polyethylene glycol 600 monooleate (PEG600MO);

[0021] The epoxy resin is at least one of E44 epoxy resin, E51 epoxy resin, AFG90 epoxy resin, AG80 epoxy resin and pentaerythritol tetraglycidyl ether.

[0022] In the above-mentioned aqueous sizing agent, the water-soluble polyamic acid salt is prepared by a method comprising the following steps: under nitrogen protection, dissolving an aromatic diamine in a protonic non-polar solvent, slowly adding a dianhydride, and conducting a condensation reaction to obtain a polyamic acid solution; then mixing the polyamic acid solution and a salt-forming agent to obtain the polyamic acid salt solution; pouring the polyamic acid salt solution into a precipitant to precipitate a polyamic acid salt solid, and drying the solid to obtain the water-soluble polyamic acid salt.

[0023] The above-mentioned aqueous sizing agent, wherein the dianhydride is added to a solution of an aromatic diamine at 0 to 35°C;

[0024] The polycondensation reaction is carried out under nitrogen protection and ice bath conditions; the polycondensation reaction time is 10 to 18 hours;

[0025] The precipitant is acetone;

[0026] The drying temperature is 30-80°C;

[0027] The aromatic diamine is at least one of 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 2,2'-bis[4-(4-aminophenoxyphenyl)]propane, 2,2'-bis[3-(3-aminobenzoyl)-4-hydroxyphenyl]hexafluoroisopropyl and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane;

[0028] The protic non-polar solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide;

[0029] The dianhydride is at least one of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride and 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride);

[0030] The salt-forming agent is at least one of dimethylethanolamine, ethanolamine, triethylamine and triethanolamine;

[0031] The molar ratio of the aromatic diamine to the dianhydride is 1:1;

[0032] The total mass of the aromatic diamine and the dianhydride accounts for 20% to 30% of the total mass of the aromatic diamine, the protic non-polar solvent and the dianhydride; specifically, it can be 30%;

[0033] The molar ratio of the salt-forming agent to the dianhydride is 2 to 4:1, and can be specifically 4:1.

[0034] The water-based sizing agent of the present invention has good heat resistance, and the sizing agent has a 5% thermal decomposition temperature of 410-491° C. in an air atmosphere.

[0035] The present invention also provides a method for preparing the above-mentioned aqueous sizing agent, which is method (1) or method (2):

[0036] The method (1) comprises the following steps: when the functional additive is a water-soluble surfactant, mixing the main slurry, triethylamine and water to prepare a polyamic acid salt aqueous solution; then adding the water-soluble surfactant to obtain the aqueous sizing agent;

[0037] The method (ii) comprises the following steps: when the functional additive is an epoxy resin, mixing the main slurry, triethylamine and water to prepare a polyamic acid salt aqueous solution; then adding an emulsifier to form a homogeneous aqueous solution; dissolving the epoxy resin in a low-boiling point organic solvent to prepare an epoxy resin organic solution; and dropwise adding the epoxy resin organic solution to the homogeneous aqueous solution under stirring, and continuing stirring to obtain the aqueous sizing agent.

[0038] In the above-mentioned preparation method (1), the water-soluble surfactant is added under a stirring rate of 200 to 300 r / min;

[0039] In method (2), the low boiling point organic solvent is at least one of acetone, dichloromethane and ethyl acetate;

[0040] In the epoxy resin organic solution, the mass percentage concentration of the epoxy resin is 6% to 10%, and specifically 8%;

[0041] The stirring speed is 12000-18000 r / min;

[0042] The stirring time is 1 to 2 hours;

[0043] The dropwise addition rate of the epoxy resin organic solution is 1-2 mL / min.

[0044] The present invention further provides the use of the aqueous sizing agent in carbon fiber surface modification.

[0045] The aqueous sizing agent is attached to the carbon fiber by an impregnation method for modification; specifically, the impregnation time is 10 to 30 seconds; after impregnation, the carbon fiber is heated by a hot roller and dried at 80 to 180° C. for 100 to 150 seconds.

[0046] The solid content of the aqueous sizing agent is 0.5-2 wt %; if the solid content of the sizing agent is less than 0.5 wt %, the sizing effect is poor and the carbon fiber is prone to hairiness; if the solid content of the sizing agent exceeds 2 wt %, the carbon fiber is too hard, affecting the processing performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Schematic diagram of the sizing and drying process of carbon fiber.

[0048] Figure 2 Schematic diagram of the method for determining the drape value of a carbon fiber bundle; in the figure, 1 is a fixing belt; 2 is a carbon fiber bundle; 3 is a 100g weight; 4 is a base; 5 is a carbon fiber bundle; 6 is a fixing belt; L is the horizontal distance between the end of the carbon fiber bundle and the base.

[0049] Figure 3 This is a schematic diagram of the carbon fiber fuzzing test; in the figure, 1 unwinding device; 2 guide ring; 3 guide rod; 4 guide and yarn spreading device; 5 height difference; 6 fuzz collection material; 7 loading block; 8 height adjustment device; 9 winding device.

[0050] Best Mode for Carrying Out the Invention

[0051] The present invention is described in further detail below in conjunction with specific embodiments. The examples provided are only for illustrating the present invention, not for limiting the scope of the invention. The experimental methods in the following examples are conventional methods unless otherwise specified. The materials, reagents, instruments, etc. used in the following examples are all commercially available unless otherwise specified. The quantitative tests in the following examples were performed in triplicate, and the results were averaged.

[0052] In the following examples, the carbon fiber used is GW800G-12K carbon fiber produced by Weihai Tuozhan Fiber Co., Ltd.

[0053] In the following examples, the method for sizing the carbon fibers and testing their performance after treatment is as follows:

[0054] 1. Method for sizing carbon fiber

[0055] The sizing and drying process of carbon fiber is as follows Figure 1 As shown in the figure, after the carbon fiber bare yarn is unrolled, it is fully impregnated with sizing agent in a glue tank for 10 seconds. It is then heated and dried in a hot oven at 130°C for 140 seconds, and finally rolled to obtain the sized carbon fiber.

[0056] 2. Sizing amount

[0057] The evaluation method of sizing rate is to take 1.0-1.5g of carbon fiber material and weigh it accurately (W i ), then Soxhlet extraction of the carbon fiber was performed with 400-450 mL of N-methylpyrrolidone for 4 hours, and then rinsed and soaked with acetone. The sample was placed in an oven at 110°C for drying, and the weight of the dried carbon fiber (W f ). The sizing amount is calculated according to the following formula.

[0058]

[0059] 3. Overhang value

[0060] Cut the effective length of 40cm of carbon fiber bundle, according to Figure 2 As shown in (a), one end is fixed vertically and a 100g weight is hung on the other end to correct the bending and twisting of the carbon fiber bundle and let it stand for 30 minutes. Then remove the weight and follow the Figure 2 As shown in (b) of the figure, a carbon fiber bundle is fixed to a horizontal rectangular base and secured with a fixing strap to a length of 25 cm. A support (not shown) maintains the bundle level with the base. After removing the support, the bundle bends downward due to its own weight. After standing for 2 minutes, the horizontal distance L is measured three times, and the average value is taken to obtain the drape value of the sized carbon fiber.

[0061] 4. Raising amount

[0062] The test method for carbon fiber fuzzing is based on GB / T 41956-2022. Figure 3 As shown in the figure, the carbon fiber passed through four guide rods at a rate of 15 m / min and then through two polyurethane foam sheets with a 100 g weight above the sponges. The run length was set to 50 m. The mass of the filaments collected on the polyurethane foam was weighed. The experiment was repeated three times for each sample, and the average value was taken.

[0063] 5. Thermogravimetric analysis

[0064] Thermogravimetric analysis was performed in accordance with GB / T 27761-2011. The sizing agent slurry was tested using a thermogravimetric analyzer, and the 5% thermal weight loss temperature was obtained based on the thermal weight loss curve.

[0065] Example 1

[0066] (1) Preparation of polyamic acid salt

[0067] Under nitrogen, 361.25g of 2,2'-bis[4-(4-aminophenoxyphenyl)]propane was dissolved in 500g of N,N-dimethylacetamide. 197.27g of 1,2,4,5-cyclohexanetetracarboxylic dianhydride was slowly added at room temperature (25-30°C) with stirring, followed by 803.21g of N,N-dimethylacetamide. The mixture was then stirred under nitrogen in an ice bath for 18 hours for a polycondensation reaction to produce a uniform, transparent polyamic acid solution. 356.20g of triethylamine was then added and stirred for 1 hour to produce a polyamic acid salt solution. The polyamic acid salt was then precipitated with sufficient acetone. The solid was then air-dried at 30°C for 6 hours.

[0068] (2) Sizing agent preparation

[0069] While stirring and heating at 40°C, 60g of polyamic acid salt solid was dissolved in 5811.88g of deionized water, and 128.12g of triethylamine was added to aid dissolution of the polyamic acid salt. After stirring for 3-4 hours, a homogeneous polyamic acid salt solution with a solid content of 1wt% was obtained, which was the sizing solution.

[0070] The sizing liquid in this embodiment is used to perform sizing treatment on carbon fibers on a carbon fiber production line, and then is heated and dried.

[0071] The processability of the sized fibers was evaluated, as shown in Table 1. As shown in Table 1, the carbon fiber sizing percentage was 0.77%, the 5% thermal decomposition temperature under nitrogen atmosphere was 491°C, the carbon fiber drape value was 74 mm, and the fuzz was 52.7 mg / 50 m.

[0072] Table 1 Carbon fiber properties prepared in Example 1

[0073] Test items Sizing amount (%) Overhang value (mm) Fuzzing amount (mg / 50m) <![CDATA[T d5 (℃)]]> Test results 0.77 74 52.7 491

[0074] Example 2

[0075] A modified polyimide sizing solution was prepared using the 1wt% sizing solution obtained in Example 1. 8000g of sizing solution was taken and 3.33g of sodium lauryl sulfate was dissolved in the sizing solution. 8.89g of E44 epoxy resin (6101 resin, Nantong Xingchen Synthetic Materials Co., Ltd.) was dissolved in 102.24g of dichloromethane. The sizing solution was stirred at a rate of 18000r / min using a homogenizer. The E44 epoxy resin solution was added dropwise to the sizing solution at a rate of 1-2mL / min. 774.54g of deionized water was added to obtain a modified sizing solution with a solid content of 1wt%. Then, stirring was continued at 18000r / min for 1 hour to obtain a uniform modified aqueous emulsion sizing agent with a main sizing material to epoxy resin mass ratio of 90 / 10.

[0076] The aqueous emulsion sizing agent in this example was used to size carbon fibers on a carbon fiber production line, followed by heat drying. The processability of the sized fibers was evaluated, as shown in Table 2. Due to the presence of a surfactant in the sizing agent, the wettability of the fibers was improved, and the carbon fiber sizing content increased to 1.02%. The 5% thermal decomposition temperature under nitrogen was 450°C, but the processability of the carbon fibers was relatively poor, with a drape value of 80 mm and a fuzzing rate of 86.4 mg / 50 m.

[0077] Table 2 Performance of carbon fiber prepared in Example 2

[0078] Test items Sizing amount (%) Overhang value (mm) Fuzzing amount (mg / 50m) <![CDATA[T d5 (℃)]]> Test results 1.02 80 86.4 450

[0079] Example 3

[0080] A modified polyimide sizing solution was prepared using the 1wt% sizing solution obtained in Example 1. 8000g of sizing solution was taken and 3.33g of sodium dodecylsulfonate was dissolved in the sizing solution. 8.89g of E51 epoxy resin (0164 resin, Nantong Xingchen Synthetic Materials Co., Ltd.) was dissolved in 102.24g of dichloromethane. The sizing solution was stirred at a rate of 18000r / min using a homogenizer. The E51 epoxy resin solution was added dropwise to the sizing solution at a rate of 1-2mL / min. 774.54g of deionized water was added to obtain a modified sizing solution with a solid content of 1wt%. Then, stirring was continued at 18000r / min for 1 hour to obtain a uniform modified aqueous emulsion sizing agent with a main sizing material to epoxy resin mass ratio of 90 / 10.

[0081] The aqueous emulsion sizing agent in this example was used to sizing carbon fibers on a carbon fiber production line, followed by heat drying. The processability of the sized fibers was evaluated, as shown in Table 3. The carbon fibers had a sizing content of 1.02%, a 5% thermal decomposition temperature of 420°C under a nitrogen atmosphere, a carbon fiber drape of 75 mm, and a fiber fuzz of 108.0 mg / 50 m.

[0082] Table 3 Carbon fiber properties prepared in Example 3

[0083] Test items Sizing amount (%) Overhang value (mm) Fuzzing amount (mg / 50m) <![CDATA[T d5 (℃)]]> Test results 1.02 75 108.0 420

[0084] Example 4

[0085] A modified polyimide sizing solution was prepared using the 1wt% sizing solution obtained in Example 1. 8000g of the sizing solution was taken and 3.33g of sodium lauryl sulfate was dissolved in the sizing solution. 8.89g of pentaerythritol tetraglycidyl ether (PB10597, Guangdong Wengjiang Chemical Reagent Co., Ltd.) was dissolved in 102.24g of ethyl acetate. The sizing solution was stirred at a rate of 18000r / min using a homogenizer. The pentaerythritol tetraglycidyl ether solution was added dropwise to the sizing solution at a rate of 1-2mL / min. 774.54 of deionized water was added to obtain a modified sizing solution with a solid content of 1wt%. Then, stirring was continued at 18000r / min for 1 hour to obtain a uniform modified aqueous emulsion sizing agent with a main sizing agent to epoxy resin mass ratio of 90 / 10.

[0086] The aqueous emulsion sizing agent in this example was used to size carbon fibers on a carbon fiber production line, followed by heat drying. The processability of the sized fibers was evaluated, as shown in Table 4. The carbon fibers had a sizing content of 0.98%, a 5% thermal decomposition temperature of 410°C under a nitrogen atmosphere, a carbon fiber drape of 42 mm, and a fiber fuzz of 91.3 mg / 50 m.

[0087] Table 4 Carbon fiber properties prepared in Example 4

[0088] Test items Sizing amount (%) Overhang value (mm) Fuzzing amount (mg / 50m) <![CDATA[T d5 (℃)]]> Test results 0.98 42 91.3 410

[0089] Example 5

[0090] A modified polyimide sizing solution was prepared using the 1wt% sizing solution obtained in Example 1. 8000g of sizing solution was taken, and 1.11g of sodium lauryl sulfate and 4.45g of sodium dodecylbenzene sulfonate were dissolved in the sizing solution. 8.89g of AG80 epoxy resin (Shanghai Huayi Resin Co., Ltd.) was dissolved in 102.24g of acetone. The sizing solution was stirred at a rate of 18000r / min using a homogenizer. The AG80 epoxy resin solution was added dropwise to the sizing solution at a rate of 1-2mL / min. 772.31g of deionized water was added to obtain a modified sizing solution with a corresponding solid content. Then, stirring was continued at 18000r / min for 1 hour to obtain a uniform modified aqueous emulsion sizing agent with a main sizing material and epoxy resin mass ratio of 90 / 10.

[0091] The aqueous emulsion sizing agent in this example was used to size carbon fibers on a carbon fiber production line, followed by heat drying. The processability of the sized fibers was evaluated, as shown in Table 5. The carbon fibers had a sizing content of 1.05%, a 5% thermal decomposition temperature under nitrogen of 435°C, a carbon fiber drape of 96 mm, and a fiber fuzz of 31.1 mg / 50 m.

[0092] Table 5 Carbon fiber properties prepared in Example 5

[0093] Test items Sizing amount (%) Overhang value (mm) Fuzzing amount (mg / 50m) <![CDATA[T d5 (℃)]]> Test results 1.05 96 31.1 435

[0094] Example 6

[0095] A modified polyimide sizing solution was prepared using the 1wt% sizing solution obtained in Example 1. 8000g of sizing solution was taken and 3.33g of sodium dodecylsulfonate was dissolved in the sizing solution. 8.89g of AFG90 epoxy resin (Shenzhen Jiadida New Materials Co., Ltd.) was dissolved in 102.24g of acetone. The sizing solution was stirred at a rate of 18000r / min using a homogenizer. The AFG90 epoxy resin solution was added dropwise to the sizing solution at a rate of 1-2mL / min. 774.54 of deionized water was added to obtain a modified sizing solution with a solid content of 1wt%. Then, stirring was continued at 18000r / min for 1 hour to obtain a uniform modified aqueous emulsion sizing agent with a main sizing agent to epoxy resin mass ratio of 90 / 10.

[0096] The aqueous emulsion sizing agent in this example was used to size carbon fibers on a carbon fiber production line, followed by heat drying. The processability of the sized fibers was evaluated, as shown in Table 6. The carbon fibers had a sizing content of 1.20%, a 5% thermal decomposition temperature of 466°C under a nitrogen atmosphere, a carbon fiber drape of 140 mm, and a fiber fuzz of 30.1 mg / 50 m.

[0097] Table 6 Carbon fiber properties prepared in Example 6

[0098] Test items Sizing amount (%) Overhang value (mm) Fuzzing amount (mg / 50m) <![CDATA[T d5 (℃)]]> Test results 1.20 140 30.1 466

[0099] Example 7

[0100] A modified polyimide sizing solution was prepared using the 1wt% sizing solution obtained in Example 1. 8000g of sizing solution was taken and 2.43g of sodium dodecyl sulfate was dissolved in the sizing solution. 6.49g of AFG90 epoxy resin was dissolved in 74.64g of acetone. The sizing solution was stirred at a rate of 18000r / min using a homogenizer. The AFG90 epoxy resin solution was added dropwise to the sizing solution at a rate of 1-2mL / min. 565.44g of deionized water was added to obtain a modified sizing solution with a solid content of 1wt%. Then, stirring was continued at 18000r / min for 1 hour to obtain a uniform modified aqueous emulsion sizing agent with a main sizing agent to epoxy resin mass ratio of 92.5 / 7.5.

[0101] The aqueous emulsion sizing agent in this example was used to sizing carbon fibers on a carbon fiber production line, followed by heat drying. The processability of the sized fibers was evaluated, as shown in Table 7. The carbon fibers had a sizing content of 1.10%, a 5% thermal decomposition temperature under nitrogen of 473°C, a carbon fiber drape of 132 mm, and a fiber fuzz of 31.9 mg / 50 m.

[0102] Table 7 Carbon fiber properties prepared in Example 7

[0103] Test items Sizing amount (%) Overhang value (mm) Fuzzing amount (mg / 50m) <![CDATA[T d5 (℃)]]> Test results 1.10 132 31.9 473

[0104] Example 8

[0105] A modified polyimide sizing solution was prepared using the 1wt% sizing solution obtained in Example 1. 8000g of sizing solution was taken and 1.58g of sodium dodecyl sulfate was dissolved in the sizing solution. 4.21g of AFG90 epoxy resin was dissolved in 48.42g of acetone. The sizing solution was stirred at a rate of 18000r / min using a homogenizer. The AFG90 epoxy resin solution was added dropwise to the sizing solution at a rate of 1-2mL / min. 371g of deionized water was added to obtain a modified sizing solution with a solid content of 1wt%. Then, stirring was continued at 18000r / min for 1 hour to obtain a uniform modified aqueous emulsion sizing agent with a mass ratio of the main sizing material to the epoxy resin of 95 / 5.

[0106] The emulsion sizing agent in this example was used to size carbon fibers on a carbon fiber production line, followed by heat drying. The processability of the sized fibers was evaluated, as shown in Table 8. The carbon fibers had a sizing content of 1.12%, a 5% thermal decomposition temperature of 480°C under a nitrogen atmosphere, a carbon fiber drape of 156 mm, and a fiber fuzz of 35.2 mg / 50 m.

[0107] Table 8 Carbon fiber properties prepared in Example 8

[0108] Test items Sizing amount (%) Overhang value (mm) Fuzzing amount (mg / 50m) <![CDATA[T d5 (℃)]]> Test results 1.12 156 35.2 480

[0109] Example 9

[0110] A modified polyimide sizing solution was prepared using the 1wt% sizing solution obtained in Example 1. 8000g of sizing solution was taken and 0.77g of sodium dodecyl sulfate was dissolved in the sizing solution. 2.05g of AFG90 epoxy resin was dissolved in 23.58g of acetone. The sizing solution was stirred at a rate of 18000r / min using a homogenizer. The AFG90 epoxy resin solution was added dropwise to the sizing solution at a rate of 1-2mL / min. 180.65g of deionized water was added to obtain a modified sizing solution with a solid content of 1wt%. Then, stirring was continued at 18000r / min for 1 hour to obtain a uniform modified aqueous emulsion sizing agent with a main sizing agent to epoxy resin mass ratio of 97.5 / 2.5.

[0111] The aqueous emulsion sizing agent in this example was used to size carbon fibers on a carbon fiber production line, followed by heat drying. The processability of the sized fibers was evaluated, as shown in Table 9. The carbon fibers had a sizing content of 1.16%, a 5% thermal decomposition temperature of 482°C under a nitrogen atmosphere, a carbon fiber drape of 144 mm, and a fiber fuzz of 31.1 mg / 50 m.

[0112] Table 9 Carbon fiber properties prepared in Example 9

[0113] Test items Sizing amount (%) Overhang value (mm) Fuzzing amount (mg / 50m) <![CDATA[T d5 (℃)]]> Test results 1.16 144 31.1 482

[0114] Example 10

[0115] A modified polyimide sizing solution was prepared using the 1 wt% sizing solution obtained in Example 1. 8000 g of the sizing solution was added with 0.8 g of alkylphenol polyoxyethylene ether (penetrant JFC-1, Hai'an Petrochemical Plant, Jiangsu Province) at a stirring rate of 200-300 r / min. 79.2 g of deionized water was then added and stirred until completely dissolved, forming a uniform modified sizing agent. The mass ratio of the main sizing agent to the aqueous surfactant was 100 / 1.

[0116] The modified sizing agent in this example was used to sizing carbon fibers on a carbon fiber production line, followed by heat drying. The processability of the sized fibers was evaluated, as shown in Table 10. The carbon fibers had a sizing content of 1.22%, a 5% thermal decomposition temperature of 447°C under a nitrogen atmosphere, a carbon fiber drape of 150 mm, and a fiber fuzz of 24.8 mg / 50 m.

[0117] Table 10 Carbon fiber properties prepared in Example 10

[0118] Test items Sizing amount (%) Overhang value (mm) Fuzzing amount (mg / 50m) <![CDATA[T d5 (℃)]]> Test results 1.22 150 24.8 447

[0119] Example 11

[0120] A modified polyimide sizing solution was prepared using the 1 wt% sizing solution obtained in Example 1. 8000 g of the sizing solution was added to the solution with 8 g of a cationic surfactant, propylene bis(tetradecyldimethylammonium chloride) (emulsifier 31524, Zhengzhou Yihe Fine Chemicals Co., Ltd.), at a stirring rate of 200-300 r / min. 792 g of deionized water was then added and stirred until completely dissolved to form a uniform modified sizing agent. The mass ratio of the main sizing solution to the aqueous surfactant was 10 / 1.

[0121] The modified sizing agent in this example was used to sizing carbon fibers on a carbon fiber production line, followed by heat drying. The processability of the sized fibers was evaluated, as shown in Table 11. The carbon fibers had a sizing content of 1.06%, a 5% thermal decomposition temperature of 476°C under a nitrogen atmosphere, a carbon fiber drape of 23 mm, and a fiber fuzz of 41.3 mg / 50 m.

[0122] Table 11 Carbon fiber properties prepared in Example 11

[0123] Test items Sizing amount (%) Overhang value (mm) Fuzzing amount (mg / 50m) <![CDATA[T d5 (℃)]]> Test results 1.06 23 41.3 476

[0124] Example 12

[0125] A modified polyimide sizing solution was prepared using the 1 wt% sizing solution obtained in Example 1. 8000 g of the sizing solution was added to 8 g of polyethylene glycol 400 monooleate (PEG400MO, Hai'an Petrochemical Plant, Jiangsu Province) at a stirring rate of 200-300 r / min. 792 g of deionized water was then added and stirred until completely dissolved to form a uniform modified sizing agent. The mass ratio of the main sizing agent to the aqueous surfactant was 10 / 1.

[0126] The modified sizing agent in this example was used to sizing carbon fibers on a carbon fiber production line, followed by heat drying. The processability of the sized fibers was evaluated, as shown in Table 12. The carbon fibers had a sizing content of 1.07%, a 5% thermal decomposition temperature of 483°C under a nitrogen atmosphere, a carbon fiber drape of 232 mm, and a fiber fuzz of 35.9 mg / 50 m.

[0127] Table 12 Carbon fiber properties prepared in Example 12

[0128] Test items Sizing amount (%) Overhang value (mm) Fuzzing amount (mg / 50m) <![CDATA[T d5 (℃)]]> Test results 1.07 232 35.9 483

[0129] Example 13

[0130] A modified polyimide sizing solution was prepared using the 1 wt% sizing solution obtained in Example 1. 8000 g of the sizing solution was added to 8 g of polyethylene glycol 600 monooleate (PEG600MO, Hai'an Petrochemical Plant, Jiangsu Province) at a stirring rate of 200-300 r / min. 792 g of deionized water was then added and stirred until completely dissolved to form a uniform modified sizing agent. The mass ratio of the main sizing agent to the aqueous surfactant was 100 / 1.

[0131] The modified sizing agent in this example was used to sizing carbon fibers on a carbon fiber production line, followed by heat drying. The processability of the sized fibers was evaluated, as shown in Table 13. The carbon fibers had a sizing content of 1.04%, a 5% thermal decomposition temperature of 439°C under a nitrogen atmosphere, a carbon fiber drape of 94 mm, and a fiber fuzz of 36.3 mg / 50 m.

[0132] Table 13 Carbon fiber properties prepared in Example 13

[0133] Test items Sizing amount (%) Overhang value (mm) Fuzzing amount (mg / 50m) <![CDATA[T d5 (℃)]]> Test results 1.04 94 36.3 439

[0134] Industrial Applications

[0135] The carbon fibers sized with the aqueous sizing agent of the present invention have good bundling, smoothness, and flexibility; the sized carbon fibers have the advantages of good wear resistance and low fuzzing; and the sized carbon fibers have good temperature resistance and can withstand the processing temperature of thermosetting polyimide resins greater than 350° C., thereby preparing high-performance polyimide composite materials.

Claims

1. A water-based sizing agent comprising a main sizing material and functional additives; The main slurry is a water-soluble polyamic acid salt; The functional additive is a water-soluble surfactant or an epoxy resin; When the functional additive is a water-soluble surfactant, the mass of the surfactant accounts for 1% to 10% of the total mass of the main slurry and the surfactant; When the functional additive is epoxy resin, the aqueous sizing agent further comprises an emulsifier; the mass of the epoxy resin accounts for 2.5% to 10% of the total mass of the main slurry and the epoxy resin; The mass ratio of the epoxy resin to the emulsifier is 8:3 to 8:5; The water-soluble surfactant is at least one of a penetrant JFC-1, a cationic surfactant 31524, and polyethylene glycol monooleate; The epoxy resin is AG80 epoxy resin and / or AFG90 epoxy resin.

2. The aqueous sizing agent according to claim 1, wherein: The aqueous sizing agent further comprises water; the solid content of the aqueous sizing agent is 0.5 wt% to 2 wt%; and / or The aqueous sizing agent further includes a cosolvent.

3. The aqueous sizing agent according to claim 2, wherein: The cosolvent is triethylamine; The mass ratio of water to triethylamine is 40-50:

1.

4. The aqueous sizing agent according to any one of claims 1 to 3, characterized in that: The emulsifier is at least one of sodium dodecyl sulfonate, sodium lauryl sulfate and sodium dodecylbenzene sulfonate.

5. The aqueous sizing agent according to any one of claims 1 to 3, characterized in that: The water-soluble polyamic acid salt is prepared by a method comprising the following steps: dissolving an aromatic diamine in a protic non-polar solvent under nitrogen protection, slowly adding a dianhydride, and performing a polycondensation reaction to obtain a polyamic acid solution; and then mixing the polyamic acid solution with a salt-forming agent to obtain the polyamic acid salt solution; The polyamic acid salt solution is poured into a precipitant to precipitate a polyamic acid salt solid, and the solid is dried to obtain the water-soluble polyamic acid salt.

6. The aqueous sizing agent according to claim 5, characterized in that: The dianhydride is added to a solution of aromatic diamine at 0-35°C; The polycondensation reaction is carried out under nitrogen protection and ice bath conditions; the polycondensation reaction time is 10 to 18 hours; The aromatic diamine is at least one of 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 2,2'-bis[4-(4-aminophenoxyphenyl)]propane, 2,2'-bis[3-(3-aminobenzoyl)-4-hydroxyphenyl]hexafluoroisopropyl and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane; The protic non-polar solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide; The dianhydride is at least one of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride and 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride); The salt-forming agent is at least one of dimethylethanolamine, ethanolamine, triethylamine and triethanolamine; The molar ratio of the aromatic diamine to the dianhydride is 1:1; The total mass of the aromatic diamine and dianhydride accounts for 20% to 30% of the total mass of the aromatic diamine, protic non-polar solvent and dianhydride; The molar ratio of the salt-forming agent to the dianhydride is 2-4:

1.

7. The method for preparing the aqueous sizing agent according to any one of claims 1 to 6, which is method (1) or method (2): The method (1) comprises the following steps: when the functional additive is a water-soluble surfactant, mixing the main slurry, triethylamine and water to prepare a polyamic acid salt aqueous solution; then adding the water-soluble surfactant to obtain the aqueous sizing agent; The method (ii) comprises the following steps: when the functional additive is an epoxy resin, mixing the main slurry, triethylamine and water to prepare a polyamic acid salt aqueous solution; then adding an emulsifier to form a homogeneous aqueous solution; dissolving the epoxy resin in a low-boiling point organic solvent to prepare an epoxy resin organic solution; and dropwise adding the epoxy resin organic solution to the homogeneous aqueous solution under stirring, and continuing stirring to obtain the water-based sizing agent.

8. The preparation method according to claim 7, characterized in that: In method (1), the water-soluble surfactant is added under a stirring rate of 200-300 r / min; In method (2), the low-boiling-point organic solvent is at least one of acetone, dichloromethane and ethyl acetate; In the epoxy resin organic solution, the mass percentage concentration of the epoxy resin is 6% to 10%; The stirring speed is 12000~18000r / min; The stirring time is 1 to 2 hours; The dropwise addition rate of the epoxy resin organic solution is 1-2 mL / min.

9. Use of the aqueous sizing agent according to any one of claims 1 to 6 in carbon fiber surface modification.

10. The use according to claim 9, characterized in that: The aqueous sizing agent is attached to the carbon fiber by an impregnation method to perform modification.

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