Pitch-based carbon fiber sizing agent and method for preparing the same

Abstract

The application belongs to the technical field of carbon fiber sizing agent, and discloses a pitch-based carbon fiber sizing agent and a preparation method thereof. The sizing agent is prepared by using epoxy resin and modified epoxy resin as main sizing agents, adding emulsifiers, antioxidants, lubricants and penetrants as auxiliary sizing agents, and adding deionized water, and adopting phase transfer emulsification to obtain a water-based epoxy resin pitch-based carbon fiber sizing agent. The prepared sizing agent is used for sizing pitch-based carbon fibers, and solves a series of problems such as fiber bundle surface oxidation, poor wear resistance and easy generation of filament bundles, and low resin combination strength.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of carbon fiber sizing agent, and relates to a pitch-based carbon fiber sizing agent and a preparation method thereof. BACKGROUND

[0002] Carbon fiber is a new type of fiber material with a carbon content of more than 90%, high strength and high modulus, which is obtained by stacking organic fibers such as flaky graphite microcrystals along the fiber axis direction, and then carbonizing and graphitizing the microcrystalline material. Carbon fiber is flexible on the outside and rigid on the inside, and its mass is lighter than that of aluminum, but its strength is higher than that of steel, and it also has corrosion resistance, and is an important material in national defense and civil use.

[0003] The simple process of the carbon fiber material preparation process includes raw material processing, spinning, pre-oxidation, carbonization, graphitization, surface treatment, sizing and the like. The fiber tows obtained in this way are combined with the corresponding resin to obtain high-performance carbon fiber composite materials. In the preparation of composite materials, the fiber tows are usually arranged in a certain direction or pre-woven, and then impregnated with resin, and the composite material is obtained after the resin is cured.

[0004] Carbon fiber is a brittle material itself, and in the production process of the raw yarn, the friction between the fiber yarn and the equipment or the friction inside the fiber tow will cause the fiber single yarn to break, and the broken yarn is prone to occur. In order to protect the fiber tow, sizing treatment needs to be performed on the carbon fiber, so that the sizing agent forms a thin film on the surface of the fiber, which prevents the surface of the fiber from being oxidized and reduces the generation of loose yarn.

[0005] In carbon fiber reinforced matrix composite materials, the real interface between carbon fiber and resin is a transition layer mainly composed of sizing agent. The sizing agent connects carbon fiber and matrix resin, so that the two become a whole that bears external force. When the interface connection is good, the shear strain through the interface can effectively transfer the load, thereby greatly improving the ability of the composite material to withstand external force.

[0006] In the field of carbon fiber composite materials, different application directions require the use of different composite materials, and different composite materials use different resins, and their performances are different. As the connecting interface between fiber and resin, the carbon fiber sizing agent must be suitable for the corresponding fiber and the corresponding resin.

[0007] The existing asphalt-based sizing agent is a sizing agent for PAN-based carbon fibers, and the asphalt-based carbon fiber sizing agent is still in the research and development stage, but the PAN-based carbon fiber is a carbon fiber obtained by carbonization below 1700 DEG C, and some active groups such as CN- and oxygen-containing groups are still left on the fiber surface, so the surface activity is high, the asphalt-based carbon fiber is a graphitic fiber after graphitization at 2500-2800 DEG C, and there is almost no active group on the surface except carbon, so it is of great significance to research and develop a special sizing agent based on the inert surface of the asphalt-based carbon fiber. SUMMARY

[0008] In order to overcome the shortcomings of the prior art, the present application provides an asphalt-based carbon fiber sizing agent and a preparation method thereof, which uses epoxy resin and modified epoxy resin as the main sizing agent, and adds emulsifier, antioxidant, lubricant and penetrant as the auxiliary sizing agent, and is prepared into a water-based epoxy resin asphalt-based carbon fiber sizing agent by phase transfer emulsification method. The prepared sizing agent is used for sizing the asphalt-based carbon fiber, and solves a series of problems such as fiber bundle surface oxidation, poor wear resistance, easy generation of filament bundle and low resin combination strength.

[0009] The above object of the present application is achieved by the following technical scheme:

[0010] An asphalt-based carbon fiber sizing agent, which comprises a main sizing agent and an auxiliary sizing agent, uses epoxy resin and modified epoxy resin as the main sizing agent, and uses emulsifier, antioxidant, lubricant and penetrant (mass ratio: 10:0.3:0.4:2) as the auxiliary sizing agent, and is prepared with deionized water; the mass ratio of the epoxy resin and the modified epoxy resin is 2:1-4:1.

[0011] The epoxy resin is bisphenol A epoxy resin. The modified epoxy resin is bisphenol A polyoxyethylene ether.

[0012] Further, the bisphenol A epoxy resin comprises solid bisphenol A epoxy resin and liquid bisphenol A epoxy resin, and the mass ratio of the solid bisphenol A epoxy resin and the liquid bisphenol A epoxy resin is 3:1-6:1.

[0013] Further, the auxiliary sizing agent is not more than 20-25% of the mass of the main sizing agent. Preferably, the auxiliary sizing agent is not more than 20% of the mass of the main sizing agent.

[0014] Further, the emulsifier comprises anionic surfactant and non-ionic surfactant (mass ratio: 5:2-7:2), the anionic surfactant is ammonium sulfate ester salt compound, and the non-ionic surfactant is polyoxyethylene alkyl ether.

[0015] Further, the antioxidant is phenyl beta-aniline, the lubricant is butyl stearate, and the penetrant is fatty alcohol polyoxyethylene ether.

[0016] The preparation method of the pitch-based carbon fiber sizing agent is as follows: the final use form of the pitch-based carbon fiber sizing agent is a water-based emulsion, and the water-based emulsion can be prepared by a phase transfer emulsification method. First, an epoxy resin and a modified epoxy resin are respectively added into an emulsifier to prepare emulsions, then the two emulsions are mixed, and other sizing auxiliaries and deionized water are added to obtain an emulsion type sizing agent.

[0017] The application of the pitch-based carbon fiber sizing agent prepared by the preparation method in fiber sizing is as follows: when the pitch-based carbon fiber sizing agent is sized, an infiltration method is adopted, that is, under the traction of drafting, the carbon fiber tows pass through a sizing tank, so that the sizing agent is attached to the surface of the fiber tows, and then the sizing agent is dried by means of a blowing drying oven.

[0018] The beneficial effects of the present application compared with the prior art are as follows:

[0019] The present application increases an oxyethylene water-soluble group in the molecular structure of the modified epoxy resin to form an amphoteric compound, one end of which is combined with the epoxy resin through a bisphenol group, and the other end is combined with the hydrogen bond in water through an oxyethylene group, so that the surface energy of the epoxy resin in the aqueous solution is reduced, the spreading property of the epoxy resin on the surface of the fiber is increased, the uniformity of the sizing agent on the surface of the fiber is improved, the problems of easy oxidation of the carbon fiber tows, poor wear resistance and easy generation of hair are solved, and the bonding strength between the fiber and the resin is effectively increased. DETAILED DESCRIPTION

[0020] The present application will be described in detail below through specific examples, but the protection scope of the present application is not limited. Unless otherwise specified, the experimental methods used in the present application are conventional methods, and the experimental apparatus, materials and reagents used can be obtained from commercial channels.

[0021] Example 1

[0022] The epoxy resin E20, the epoxy resin E-51, the bisphenol A polyoxyethylene ether BPE-06, the anionic surfactant Nikon 707-SF and the nonionic surfactant NP-10 are added into a high-shear emulsifier at a mass ratio of 15:5:10:5:2, and emulsified at a speed of 15000 revolutions per minute for 30 minutes to prepare a water emulsion solution. Then, 0.3wt% of the antioxidant phenyl beta-aniline, 0.4wt% of the lubricant butyl stearate and 0.3wt% of the antioxidant fatty alcohol polyoxyethylene ether are added to obtain a sizing agent with a solid content of 38wt%.

[0023] The sizing agent obtained in Example 1 above was diluted to a solid content of 2 wt%, placed in a sizing tank, and used to size carbon fibers having a single filament count of 3K, which were then dried. The dried fibers were measured for hairiness, tensile strength, tensile modulus, and interfacial shear strength. The results are shown in Table 1.

[0024] Example 2

[0025] Epoxy resin E20, epoxy resin E-51, bisphenol A polyoxyethylene ether BPE-06, anionic surfactant Nikon 707-SF, and nonionic surfactant NP-10 were added to a high-shear emulsifier at a mass ratio of 25:5:10:5:2, and emulsified for 30 minutes at a rotation speed of 15,000 rpm to prepare an aqueous emulsion. Then, 0.3 wt% of the antioxidant phenyl β-naphthylamine, 0.4 wt% of the lubricant butyl stearate, and 0.3 wt% of the antioxidant fatty alcohol polyoxyethylene ether were added to prepare a sizing agent having a total solid content of 48 wt%.

[0026] The sizing agent obtained in Example 2 above was diluted to a solid content of 2 wt%, placed in a sizing tank, and used to size carbon fibers having a single filament count of 3K, which were then dried. The dried fibers were measured for hairiness, tensile strength, tensile modulus, and interfacial shear strength. The results are shown in Table 1.

[0027] Example 3

[0028] Epoxy resin E20, epoxy resin E-51, bisphenol A polyoxyethylene ether BPE-06, anionic surfactant Nikon 707-SF, and nonionic surfactant NP-10 were added to a high-shear emulsifier at a mass ratio of 25:5:10:5:2, and emulsified for 30 minutes at a rotation speed of 15,000 rpm to prepare an aqueous emulsion. Then, 0.3 wt% of the antioxidant phenyl β-naphthylamine, 0.4 wt% of the lubricant butyl stearate, and 0.3 wt% of the antioxidant fatty alcohol polyoxyethylene ether were added to prepare a sizing agent having a total solid content of 48 wt%.

[0029] The sizing agent obtained in Example 3 above was diluted to a solid content of 2 wt%, placed in a sizing tank, and used to size carbon fibers having a single filament count of 3K, which were then dried. The dried fibers were measured for hairiness, tensile strength, tensile modulus, and interfacial shear strength. The results are shown in Table 1.

[0030] Comparative Example 1

[0031] The epoxy resin E20, epoxy resin E-51, anionic surfactant Nikon 707-SF, nonionic surfactant NP-10, according to the mass ratio of 25:5:5:2, prepared into water-based emulsion, the method described above, add high shear emulsifier, speed 15000 revolutions per minute, emulsified for 30 minutes, prepared into water emulsion, then add 0.3wt% antioxidant phenyl beta-aniline, 0.4wt% lubricant butyl stearate, 0.3wt% antioxidant fatty alcohol polyoxyethylene ether prepared to get the total solid content of 38wt% sizing agent.

[0032] The sizing agent obtained above is diluted to a solid content of 2wt%, placed in a sizing tank, and used to size carbon fibers with a single filament count of 3K. The dried fibers are then measured for their hair weight, tensile strength, tensile modulus, and interfacial shear strength. The results are shown in Table 1.

[0033] Comparative Example 2

[0034] The commercially available epoxy resin sizing agent (A) is diluted to a solid content of 2wt%, placed in a sizing tank, and used to size carbon fibers with a single filament count of 3K. The dried fibers are then measured for their hair weight, tensile strength, tensile modulus, and interfacial shear strength. The results are shown in Table 1.

[0035] Comparative Example 3

[0036] The commercially available epoxy resin sizing agent (B) is diluted to a solid content of 2wt%, placed in a sizing tank, and used to size carbon fibers with a single filament count of 3K. The dried fibers are then measured for their hair weight, tensile strength, tensile modulus, and interfacial shear strength. The results are shown in Table 1.

[0037] Comparative Example 4

[0038] The carbon fiber raw yarn with a single filament count of 3K is measured for its hair weight, tensile strength, tensile modulus, and interfacial shear strength. The results are shown in Table 1.

[0039] Table 1 Test Results

[0040]

[0041] From the lint amount results of Example 1, Example 2, Example 3 and Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, it can be seen that the sizing agent provided by the present application can greatly reduce the lint amount of the fiber, and at the same time improve the interfacial shear strength of the fiber, which also indicates that the sizing agent provided by the present application enhances the composite effect of the resin matrix and the carbon fiber; from the results of Example 1, Example 2 and Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 in Table 1, it can be seen that the lint amount and interfacial shear strength data of the sizing agent provided by the present application are much better than those of the sizing agent without adding the modified bisphenol A polyoxyethylene ether BPE-06 formulation. From the results of Example 1, Example 2 in Table 1, it can be seen that the optimal content of the total solid content of the sizing agent is below 38%, and a higher solid content will increase the relative lint amount, but the interfacial shear strength increases with the increase of the total solid content.

[0042] The above-described embodiments are merely preferred embodiments of the present application and are not all the embodiments that can be implemented by the present application. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present application should be considered to be included in the scope of protection of the claims of the present application.

Claims

1. A method for preparing a pitch-based carbon fiber sizing agent, characterized in that, Epoxy resin E20, epoxy resin E-51, bisphenol A polyoxyethylene ether BPE-06, anionic surfactant Nikon 707-SF, and nonionic surfactant NP-10 were added to a high-shear emulsifier at a mass ratio of 15:5:10:5:2 and emulsified for 30 minutes at 15,000 rpm to prepare an aqueous emulsion solution. Then, 0.3 wt% of antioxidant phenyl β-aniline, 0.4 wt% lubricant butyl stearate, and 0.3 wt% fatty alcohol polyoxyethylene ether were added to obtain a sizing agent with a solid content of 38 wt%.

2. A method for preparing a pitch-based carbon fiber sizing agent, characterized in that, Epoxy resin E20, epoxy resin E-51, bisphenol A polyoxyethylene ether BPE-06, anionic surfactant Nikon 707-SF, and nonionic surfactant NP-10 were added to a high-shear emulsifier at a mass ratio of 25:5:10:5:2 and emulsified for 30 minutes at 15,000 rpm to prepare an aqueous emulsion solution. Then, 0.3 wt% of antioxidant phenyl β-aniline, 0.4 wt% lubricant butyl stearate, and 0.3 wt% fatty alcohol polyoxyethylene ether were added to prepare a sizing agent with a total solids content of 48 wt%.

3. A method for preparing an asphalt-based carbon fiber sizing agent, characterized in that, Epoxy resin E20, epoxy resin E-51, bisphenol A polyoxyethylene ether BPE-06, anionic surfactant Nikon 707-SF, and nonionic surfactant NP-10 were added to a high-shear emulsifier at a mass ratio of 35:5:10:5:2 and emulsified for 30 minutes at 15,000 rpm to prepare an aqueous emulsion solution. Then, 0.3 wt% of antioxidant phenyl β-aniline, 0.4 wt% lubricant butyl stearate, and 0.3 wt% fatty alcohol polyoxyethylene ether were added to prepare a sizing agent with a total solids content of 58 wt%.

4. The application of the pitch-based carbon fiber sizing agent prepared by the preparation method according to any one of claims 1-3 in fiber sizing.

5. The application as described in claim 4, characterized in that, The sizing agent was diluted to a solid content of 2 wt% and placed in a sizing tank to sizing carbon fibers with a single filament number of 3K.

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