Secondary sizing agent as well as preparation method and application thereof

Abstract

The invention provides a secondary sizing agent as well as a preparation method and application thereof. The secondary sizing agent comprises the following components: a main film-forming agent, an auxiliary film-forming agent, a lubricant, a silane coupling agent and water, wherein the main film-forming agent is an aqueous epoxy solution, the auxiliary film-forming agent comprises a low molecular weight epoxy emulsion and an aqueous polyurethane emulsion, and the lubricant comprises an organosilicon lubricant and an ionic lubricant. In the scheme, the secondary sizing agent formed by mixing the main film-forming agent, the auxiliary film-forming agent, the lubricant and the silane coupling agent with proper types and proper contents can endow the silicon carbide fiber with excellent wear resistance, folding resistance and mechanical properties. Compared with one-time sizing, the number of times of wear resistance of the fiber yarn is increased by more than 10 times, the yarn breaking rate in the fabric processing process is greatly reduced from 10% to 0.5%, the surface smoothness of the prepared fiber fabric is greatly improved, the performance of the composite material prepared through the impregnation method is integrally improved, the bending strength is obviously improved, and the performance requirement of the three-dimensional fabric can be completely met.

Description

Technical Field

[0001] The invention relates to the technical field of fiber sizing, and in particular to a secondary sizing agent and a preparation method and application thereof. Background Art

[0002] Silicon carbide fiber has excellent properties such as anti-oxidation, chemical corrosion resistance, high temperature resistance, high specific strength, and high specific modulus. It has always been used as a special structural reinforcement material in an emerging field and is widely used in the field of high-precision and cutting-edge technology. At present, after years of development, domestic silicon carbide fibers have certain flat fabric weaving properties. Flat fabrics woven from silicon carbide fibers have been used as substrates in various cutting-edge fields. Since silicon carbide fibers are brittle materials with low elongation at break and low elasticity, the silicon carbide fiber preforms used to reinforce composite materials are repeatedly stretched, rubbed, and bent during the weaving process, causing the fiber bundles to become fluffy, loose, or split, and the openings are unclear during weaving, which makes it difficult to interweave the fibers smoothly, seriously affecting the quality of the silicon carbide fiber preforms. Therefore, in order to achieve stable production of silicon carbide fiber preforms, manufacturers use sizing agents to treat the fibers to improve the processability of the fibers.

[0003] Due to the limitations of the silicon carbide fiber production process, one-time sizing can only form a protective film on the surface of a single fiber, and cannot protect the broken fibers inside the fiber and the entire fiber bundle. Moreover, compared with flat fabrics, three-dimensional fabrics are woven by interlacing yarns in multiple directions, and the existing fibers formed after one sizing cannot meet the performance requirements of three-dimensional fabrics.

[0004] Based on this, there is an urgent need to provide a secondary sizing agent and a preparation method and application thereof. Summary of the invention

[0005] The embodiment of the present invention provides a secondary sizing agent and a preparation method and application thereof, which can solve the problem that the traditional sizing agent cannot protect the broken fibers inside the fiber and the entire fiber bundle, so that the fibers formed after the first sizing cannot meet the performance requirements of the three-dimensional fabric.

[0006] In a first aspect, the present invention provides a secondary sizing agent, comprising the following components: a main film-forming agent, an auxiliary film-forming agent, a lubricant, a silane coupling agent and water; wherein the main film-forming agent is an aqueous epoxy solution, the molecular weight of the aqueous epoxy resin in the aqueous epoxy solution is less than 500, the auxiliary film-forming agent comprises a low molecular weight epoxy emulsion and an aqueous polyurethane emulsion, and the lubricant comprises a silicone lubricant and an ionic lubricant.

[0007] Preferably, the low molecular weight epoxy emulsion is a bisphenol A epoxy emulsion with an epoxy equivalent of less than 300.

[0008] Preferably, the contents of the components are as follows, by mass fraction: 2-3.5% of main film-forming agent, 0.35-2% of auxiliary film-forming agent, 0.8-2.2% of lubricant, 0.1-0.3% of silane coupling agent and 92.5-96% of water.

[0009] Preferably, the effective content of the aqueous epoxy solution is 50 wt %.

[0010] Preferably, the effective content of the low molecular weight epoxy emulsion is 60wt%, and the effective content of the aqueous polyurethane emulsion is 20wt%;

[0011] In the secondary sizing agent, the content of the low molecular weight epoxy emulsion is 0.25-1.5% by mass, and the content of the waterborne polyurethane emulsion is 0.1-0.5% by mass.

[0012] Preferably, the effective content of the silicone lubricant is 42wt%, and the effective content of the ionic lubricant is 90wt%;

[0013] In the secondary sizing agent, the content of the organic silicon lubricant is 0.5-1.2% by mass, and the content of the ionic lubricant is 0.3-1% by mass.

[0014] Preferably, the silane coupling agent is a silane coupling agent having at least two amino groups.

[0015] More preferably, the silane coupling agent is A-1120 or A-1280.

[0016] Preferably, the secondary sizing agent further comprises a spacer; wherein the spacer is boric acid.

[0017] More preferably, in the secondary sizing agent, the content of the spacer is 0.01-0.05% by mass.

[0018] In a second aspect, the present invention provides a method for preparing the secondary sizing agent described in any one of the first aspects above, the preparation method comprising: sequentially adding a main film-forming agent, an auxiliary film-forming agent, a lubricant, a silane coupling agent and a spacer into water and mixing them to obtain the secondary sizing agent.

[0019] In a third aspect, the present invention provides an application of the secondary sizing agent described in any one of the first aspects in modified silicon carbide fibers, characterized in that the silicon carbide fibers are obtained by one sizing, and the modified silicon carbide fibers are used to form three-dimensional fabrics.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] The secondary sizing agent of the present invention adopts a water-soluble epoxy solution with a molecular weight of less than 500 as a main film-forming agent. Due to its short molecular chain segment, it is easy to form a protective film with high viscosity on the fiber surface, so that the hairy fibers existing in the fiber when it leaves the factory can be attached to the fiber surface, and at the same time, the broken fibers existing in the fiber bundle can be better wrapped in the fiber bundle, so that they will not be exposed during the weaving process to cause yarn breakage; and a low-molecular-weight epoxy emulsion and an aqueous polyurethane emulsion are used as auxiliary film-forming agents. After the low-molecular-weight epoxy emulsion is compounded with the aqueous epoxy solution, on the one hand, the softness of the film formed on the fiber surface can be further improved, thereby improving the fiber's folding resistance; on the other hand, the two can be better cross-linked with each other under the action of a silane coupling agent, so as to continuously spread on the fiber surface to form a relatively dense network structure, thereby further enhancing the fiber's folding resistance and wear resistance. At the same time, the silane coupling agent can help the secondary sizing agent to form a good interface with the epoxy primary sizing agent that comes with the fiber when it leaves the factory, so as to prevent interface slippage during processing stress. The water-based polyurethane emulsion has a large molecular weight, a strong coating on the fiber yarn, and is an elastic film after film formation. This can prevent the fiber bundle surface from being too sticky, while improving the buffering performance of the protective film when the fiber bundle is bent, thereby further enhancing the folding resistance of the fiber bundle; coupled with the presence of silicone lubricants and ionic lubricants, the fiber surface has a certain lubricity, which can reduce the wear of the fiber surface during the secondary sizing process and the fabric weaving process. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] As mentioned above, in order to improve the processability of silicon carbide fibers, the fibers are sized by sizing agents in the related art. However, after sizing once, only a protective film can be formed on the surface of a single fiber, and the fibers used in production are a bundle of fibers, so it is impossible to protect the broken fibers inside the silicon carbide fibers and the entire fiber bundle. In order to improve the weaving performance of the fibers, the fibers need to be further sized for a second time to improve the wear resistance, folding resistance and other process properties of the fibers. However, there is currently little research on secondary sizing agents, and the fibers modified by sizing are currently mostly used for planar fabrics. Compared with planar fabrics, three-dimensional fabrics are interwoven by yarns in multiple different directions. In the overall structure of the fabric, there are different levels of differences between these yarns, and each layer has a complex structure. The fibers need to withstand a lot of traction, bending, friction and other process effects during the weaving process, and when the three-dimensional fabric is woven, the yarn bending angle is up to 120-150°, while the bending angle of the planar fabric weaving is generally 30-45°, so the existing fibers modified by secondary sizing cannot meet the performance requirements of three-dimensional fabrics.

[0024] Based on this, an embodiment of the present invention provides a secondary sizing agent, comprising the following components: a main film-forming agent, an auxiliary film-forming agent, a lubricant, a silane coupling agent and water; wherein the main film-forming agent is an aqueous epoxy solution, the molecular weight of the aqueous epoxy resin in the aqueous epoxy solution is less than 500, the auxiliary film-forming agent comprises a low molecular weight epoxy emulsion and an aqueous polyurethane emulsion, and the lubricant comprises a silicone lubricant and an ionic lubricant.

[0025] In the embodiment of the present invention, a small molecular weight water-soluble epoxy solution is used as the main film-forming agent. The film-forming agent can form a protective film with high viscosity on the fiber surface, so that the hairy fibers existing when the fibers leave the factory can be attached to the fiber surface, and at the same time, the broken fibers existing inside the fiber bundle can be better wrapped inside the fiber bundle, and will not be exposed during the weaving process to cause yarn breakage; and a low molecular weight epoxy emulsion and an aqueous polyurethane emulsion are used together as auxiliary film-forming agents. After the low molecular weight epoxy emulsion is compounded with the aqueous epoxy solution, on the one hand, the softness of the film formed on the fiber surface can be further improved, thereby improving the fiber's anti-bending property; on the other hand, the two can be better cross-linked with each other under the action of a silane coupling agent, so as to continuously spread on the fiber surface to form a relatively dense network structure, thereby further enhancing the fiber's anti-bending property and wear resistance. At the same time, the silane coupling agent can help the secondary sizing agent to form a better interface bonding with the epoxy primary sizing agent that comes with the fiber when it leaves the factory, thereby preventing interface slippage during processing stress. The water-based polyurethane emulsion has a large molecular weight, a strong coating on the fiber yarn, and is an elastic film after film formation. This can prevent the fiber bundle surface from being too sticky, while improving the buffering performance of the protective film when the fiber bundle is bent, thereby further enhancing the folding resistance of the fiber bundle; coupled with the presence of silicone lubricants and ionic lubricants, the fiber surface has a certain lubricity, which can reduce the wear of the fiber surface during the secondary sizing process and the fabric weaving process.

[0026] According to some preferred embodiments, the low molecular weight epoxy emulsion is a bisphenol A epoxy emulsion with an epoxy equivalent of less than 300.

[0027] In the embodiment of the present invention, a water-soluble epoxy solution with a molecular weight of less than 500 is firstly used as the main film-forming agent. Due to its short molecular chain segment, it is easy to form a surface film with high viscosity and certain rigidity on the fiber surface. The surface film can not only make the hair on the fiber surface and the broken fibers in the fiber bundle fit inside the fiber bundle, but also enhance the wear resistance of the fiber. Considering that the surface film has a certain rigidity and its folding resistance is relatively poor, a low molecular weight epoxy emulsion with an epoxy equivalent of less than 300 is further used in the embodiment of the present invention to be mixed with it. The low molecular weight epoxy emulsion has good flexibility. The surface film formed by the combination of the two is both rigid and flexible, so that the fiber has good wear resistance and folding resistance.

[0028] According to some preferred embodiments, the content of each component is as follows, by mass fraction: 2-3.5% of the main film-forming agent (for example, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2% or 3.5%), 0.35-2% of the auxiliary film-forming agent (for example, 0.35%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.5%, 1.8% or 2%), lubricant 0.8-2.2% (for example, it can be 0.8%, 0.9%, 1%, 1.2%, 1.5%, 1.8%, 2% or 2.2%), silane coupling agent 0.1-0.3% (0.1%, 0.15%, 0.2%, 0.25% or 0.3%) and water 92-96% (92%, 93%, 94%, 95% or 96%).

[0029] According to some preferred embodiments, the effective content of the aqueous epoxy solution is 50 wt %.

[0030] In the embodiment of the present invention, by controlling the content of each component in the secondary sizing agent within a reasonable range, not only can each component play its role, but also can produce a mutual synergistic effect between the components, so as to ensure that the fiber after the secondary sizing has excellent wear resistance, folding resistance, smoothness and overall mechanical properties. The experiment of the present invention confirms that the main film-forming agent and the auxiliary film-forming agent with appropriate content can ensure the good wear resistance and folding resistance of the fiber. For example, if the content of the main film-forming agent is too little, it is not conducive to ensuring the good wear resistance of the fiber, which is easy to cause yarn breakage during the weaving process; if the content of the main film-forming agent is too much, it is not only not conducive to ensuring the good wear resistance of the fiber, but it will greatly reduce the folding resistance of the fiber, and it will also cause the phenomenon of yarn breakage during the weaving process. If the content of the auxiliary film-forming agent is too low, it is not conducive to ensuring the good folding resistance of the fiber, and if the content of the auxiliary film-forming agent is too high, the wear resistance of the fiber will be reduced, and the fiber weaving process will easily produce a fluffing phenomenon, which makes the surface performance of the fiber poor. Moreover, the appropriate amount of lubricant can ensure the fiber has a certain lubricity on the basis of ensuring good wear resistance and folding resistance, which is conducive to reducing fiber wear and ensuring good fiber weaving processability. If the lubricant content is too much, the fiber will easily slip during the weaving process, increasing the difficulty of fiber weaving. At the same time, considering that the role of the silane coupling agent is to enhance the adhesion between the main film-forming agent and the auxiliary film-forming agent by chemical cross-linking, so that the main film-forming agent and the auxiliary film-forming agent form a denser network structure on the fiber surface, thereby further enhancing the mechanical properties of the fiber, therefore, the content of the silane coupling agent is mainly determined according to the content of the main film-forming agent and the auxiliary film-forming agent.

[0031] According to some preferred embodiments, the effective content of the low molecular weight epoxy emulsion is 60wt%, and the effective content of the aqueous polyurethane emulsion is 20wt%; in the secondary sizing agent, by mass fraction, the content of the low molecular weight epoxy emulsion is 0.25-1.5% (for example, it can be 0.25%, 0.3%, 0.5%, 0.8%, 1.0%, 1.2% or 1.5%), and the content of the aqueous polyurethane emulsion is 0.1-0.5% (for example, it can be 0.1%, 0.1%, 0.3%, 0.4% or 0.5%).

[0032] In the embodiment of the present invention, two different types of auxiliary film-forming agents are used and their contents are reasonably controlled, so that the two auxiliary film-forming agents can respectively enhance the folding resistance of the fiber to the greatest extent in different ways; for example, if the content of low molecular weight epoxy emulsion is too low, it is not conducive to significantly enhancing the folding resistance of the fiber, and if the content of low molecular weight epoxy emulsion is too high, the wear resistance of the fiber will be reduced, and fuzzing is likely to occur during the fiber weaving process. However, too low a content of water-based polyurethane emulsion is not conducive to enhancing the elasticity of the film formed on the fiber surface, and the cushioning performance of the protective film cannot be improved when the fiber bundle is bent.

[0033] According to some preferred embodiments, the effective content of the silicone lubricant is 42wt%, and the effective content of the ionic lubricant is 90wt%; in the secondary sizing agent, by mass fraction, the content of the silicone lubricant is 0.5-1.2% (for example, it can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0% or 1.2%), and the content of the ionic lubricant is 0.3-1% (for example, it can be 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1.0%).

[0034] In the embodiment of the present invention, two different types of wetting agents are used, and the contents of the two types of lubricants are reasonably controlled, so that the silicone lubricant and the ionic lubricant can lubricate the fiber surface and reduce wear in the wet state (during the secondary sizing process) and the dry state (during the fabric weaving process) respectively without affecting the softness of the fiber; the silicone lubricant can reduce the generation of lint on the fiber surface and improve the wear resistance of the fiber, and the ionic lubricant can greatly improve the smoothness of the fiber bundle surface.

[0035] At the same time, in the embodiment of the present invention, lubricants with smaller molecular weights are preferred during the lubricant screening process. For example, the silicone lubricant may be SE-2175, and the ionic lubricant may be 1160. The above-mentioned small molecule lubricants are not chemically combined with other components and are enriched on the fiber surface as water evaporates in the tunnel furnace. Therefore, they do not affect the bundling inside the fibers, and can be mixed with the film-forming agent on the surface of the fiber bundle to improve the smoothness of the fiber bundle surface, thereby further significantly improving the wear resistance of the fiber bundle.

[0036] According to some preferred embodiments, the silane coupling agent is a silane coupling agent with at least two amino groups; preferably, the silane coupling agent is A-1120 or A-1280.

[0037] In the embodiment of the present invention, the silane coupling agent is preferably a silane coupling agent with at least two amino groups, which is not only conducive to the effective combination of epoxy film-forming agents, ensuring the adhesion, softness and integrity of the fiber surface film, improving the bending performance, bundling and wear resistance of the fiber and providing a certain strength; but also can form a good interface with the epoxy primary sizing agent that comes with the fiber when it leaves the factory, prevent interface slip during processing and force, and ensure the stability of the production process; at the same time, it should be noted that the silane coupling agent should not have more than three amino groups. If the number of amino groups is too large, the molecular chain of the silane coupling agent will be larger, increasing the steric hindrance, which is not conducive to the effective combination between the epoxy components, and will cause moisture intrusion, thereby reducing the mechanical properties of the fiber.

[0038] According to some preferred embodiments, the secondary sizing agent also includes a spacer; wherein the spacer is boric acid; in the secondary sizing agent, the content of the spacer is 0.01-0.05% by mass (for example, it can be 0.01%, 0.02%, 0.03%, 0.04% or 0.05%).

[0039] Different from the traditional method of using boric acid as a pH regulator, in the embodiment of the present invention, an appropriate amount of boric acid is used as a spacer to form a secondary sizing agent together with other components. Boric acid can react with a silane coupling agent to generate siloxane oligomers that adhere to the surface of the silicon carbide fiber to form a strong coating with good weather resistance. This coating can effectively avoid the fuzzing phenomenon caused by excessive fiber adhesion caused by the main film-forming agent and the problem of insufficient smoothness caused by the silicone lubricant. At the same time, it can further increase the elasticity of the silicon carbide fiber surface.

[0040] An embodiment of the present invention also provides a method for preparing the secondary sizing agent described in any of the above items, the preparation method comprising: sequentially adding a main film-forming agent, an auxiliary film-forming agent, a lubricant, a silane coupling agent and a spacer into water and mixing them to obtain the secondary sizing agent.

[0041] In the embodiment of the present invention, the secondary sizing agent can be obtained by mixing and stirring the above components in a certain proportion at room temperature (such as 25° C.).

[0042] An embodiment of the present invention further provides a use of any of the secondary sizing agents described above in modified silicon carbide fibers, wherein the silicon carbide fibers are obtained by a single sizing process, and the modified silicon carbide fibers are used to form three-dimensional fabrics.

[0043] The secondary sizing agent obtained in the embodiment of the present invention is mainly used for secondary sizing modification of the existing silicon carbide fiber after the epoxy sizing agent is used once. The silicon carbide fiber after the secondary sizing has excellent wear resistance, folding resistance and mechanical properties. Specifically, compared with the primary sizing, the wear resistance of the fiber yarn is increased by more than 10 times, the yarn breakage rate during fabric processing is greatly reduced from 10% to 0.5%, the surface smoothness of the prepared fiber fabric is greatly improved, the overall performance of the composite material prepared by the impregnation method is improved, and the bending strength is significantly improved, which can fully meet the performance requirements of the three-dimensional fabric.

[0044] According to some specific embodiments, the fiber secondary sizing equipment is composed of a sizing tank, a tunnel furnace and a winding device. During the secondary sizing process, the silicon carbide fiber passes through the sizing tank containing the secondary sizing agent and then is dried in the tunnel furnace. Finally, the fiber is wound up using a special winding device to obtain the modified silicon carbide fiber. The winding speed can be 5 m / min and the drying temperature is 200°C.

[0045] It should be noted that the components in the embodiments of the present invention, such as the main film-forming agent, the auxiliary film-forming agent, etc., are not a single aqueous epoxy resin solution, but are relatively mature market products that can be purchased on the market.

[0046] In order to more clearly illustrate the technical solution and advantages of the present invention, a secondary sizing agent and a preparation method thereof are described in detail through several embodiments below;

[0047] In the following examples, the low molecular weight epoxy emulsion adopts NBR-210-50G bisphenol A epoxy emulsion of Nanjing Glass Fiber Research and Design Institute Co., Ltd., with an effective content of 50wt%; the low molecular weight waterborne epoxy solution adopts NBR-290 of Nanjing Glass Fiber Research and Design Institute Co., Ltd., with an effective content of 60wt%; the waterborne polyester polyurethane emulsion adopts U6 waterborne polyester polyurethane of Michelman Company, with an effective content of 20wt%. Coupling agents A-1120 and A-1280 are both provided by Momentive, with an effective content of 99wt%; the organosilicon lubricant is provided by Shanghai Fluorochemical Products Co., Ltd., with a trade name of SE-2175, with an effective content of 42wt%, and the ionic lubricant is provided by Guangzhou Kekai Company, with a trade name of 6760L, with an effective content of 90wt%.

[0048] Embodiment 1:

[0049] At room temperature (25°C), 3% of a main film-forming agent (aqueous epoxy solution NBR-290 with a molecular weight of less than 500), 1.5% of an auxiliary film-forming agent (1% of a low molecular weight epoxy emulsion NBR-210-50G and 0.5% of an aqueous polyurethane emulsion U6), 1% of a lubricant (0.7% of an organosilicon lubricant SE-2175 and 0.3% of an ionic lubricant 1160), 0.2% of a silane coupling agent A-1120 and 0.05% of a spacer were sequentially added to 94.25% of deionized water and stirred at 800 r / min for 30 min to obtain a secondary sizing agent.

[0050] Embodiment 2:

[0051] At room temperature (25°C), 2.5% of a main film-forming agent (aqueous epoxy solution NBR-290 with a molecular weight of less than 500), 2% of an auxiliary film-forming agent (1.5% of a low molecular weight epoxy emulsion NBR-210-50G and 0.5% of an aqueous polyurethane emulsion U6), 1% of a lubricant (0.7% of an organosilicon lubricant SE-2175 and 0.3% of an ionic lubricant 1160), 0.2% of a silane coupling agent A-1120 and 0.05% of a spacer were added to 94.25% of deionized water and stirred at 800 r / min for 30 min to obtain a secondary sizing agent.

[0052] Embodiment 3:

[0053] At room temperature (25°C), 3% of a main film-forming agent (aqueous epoxy solution NBR-290 with a molecular weight of less than 500), 1.5% of an auxiliary film-forming agent (1% of a low molecular weight epoxy emulsion NBR-210-50G and 0.5% of an aqueous polyurethane emulsion U6), 1.2% of a lubricant (0.5% of a silicone lubricant SE-2175 and 0.7% of an ionic lubricant 1160), 0.2% of a silane coupling agent A-1120 and 0.05% of a spacer were added to 94.05% of deionized water and stirred at 800 r / min for 30 min to obtain a secondary sizing agent.

[0054] Embodiment 4:

[0055] At room temperature (25°C), 3% of a main film-forming agent (aqueous epoxy solution NBR-290 with a molecular weight of less than 500), 1.5% of an auxiliary film-forming agent (1% of a low molecular weight epoxy emulsion NBR-210-50G and 0.5% of an aqueous polyurethane emulsion U6), 1% of a lubricant (0.7% of an organosilicon lubricant SE-2175 and 0.3% of an ionic lubricant 1160), and 0.2% of a silane coupling agent A-1120 were added to 94.3% of deionized water and stirred at 800 r / min for 30 minutes to obtain a secondary sizing agent.

[0056] Embodiment 5:

[0057] At room temperature (25°C), 4% of a main film-forming agent (aqueous epoxy solution NBR-290 with a molecular weight of less than 500), 1.5% of an auxiliary film-forming agent (1% of a low molecular weight epoxy emulsion NBR-210-50G and 0.5% of an aqueous polyurethane emulsion U6), 1% of a lubricant (0.7% of an organosilicon lubricant SE-2175 and 0.3% of an ionic lubricant 1160), 0.2% of a silane coupling agent A-1120 and 0.05% of a spacer were added to 93.25% of deionized water and stirred at 800 r / min for 30 min to obtain a secondary sizing agent.

[0058] Embodiment 6:

[0059] At room temperature (25°C), 3% of a main film-forming agent (aqueous epoxy solution NBR-290 with a molecular weight of less than 500), 2.5% of an auxiliary film-forming agent (2% of a low molecular weight epoxy emulsion NBR-210-50G and 0.5% of an aqueous polyurethane emulsion U6), 1% of a lubricant (0.7% of an organosilicon lubricant SE-2175 and 0.3% of an ionic lubricant 1160), 0.2% of a silane coupling agent A-1120 and 0.05% of a spacer were added to 93.25% of deionized water and stirred at 800 r / min for 30 min to obtain a secondary sizing agent.

[0060] Embodiment 7:

[0061] At room temperature (25°C), 3% of a main film-forming agent (aqueous epoxy solution NBR-290 with a molecular weight of less than 500), 1.5% of an auxiliary film-forming agent (1% of a low molecular weight epoxy emulsion NBR-210-50G and 0.5% of an aqueous polyurethane emulsion U6), 1.7% of a lubricant (0.7% of a silicone lubricant SE-2175 and 1% of an ionic lubricant 1160), 0.2% of a silane coupling agent A-1120 and 0.05% of a spacer were added to 93.55% of deionized water and stirred at 800 r / min for 30 min to obtain a secondary sizing agent.

[0062] Embodiment 8:

[0063] At room temperature (25°C), 3% of a main film-forming agent (aqueous epoxy solution NBR-290 with a molecular weight of less than 500), 1.5% of an auxiliary film-forming agent (1% of a low molecular weight epoxy emulsion NBR-210-50G and 0.5% of an aqueous polyurethane emulsion U6), 1% of a lubricant (0.7% of an organosilicon lubricant SE-2175 and 0.3% of an ionic lubricant 1160), 0.2% of a silane coupling agent A-1120 and 0.3% of a spacer were added to 94% of deionized water and stirred at 800 r / min for 30 minutes to obtain a secondary sizing agent.

[0064] Embodiment 9:

[0065] At room temperature (25°C), 3% of a main film-forming agent (aqueous epoxy solution NBR-290 with a molecular weight of less than 500), 1.5% of an auxiliary film-forming agent (1% of a low molecular weight epoxy emulsion NBR-210-50G and 0.5% of an aqueous polyurethane emulsion U6), 1% of a lubricant (0.7% of an organosilicon lubricant SE-2175 and 0.3% of an ionic lubricant 1160), 0.2% of a silane coupling agent A-1100 and 0.05% of a spacer were added to 94.25% of deionized water and stirred at 800 r / min for 30 min to obtain a secondary sizing agent.

[0066] Comparative Example 1

[0067] At room temperature (25°C), 3% of a main film-forming agent (aqueous epoxy solution NBR-290 with a molecular weight of less than 500), 1.5% of an auxiliary film-forming agent (a low molecular weight epoxy emulsion NBR-210-50G), 1% of a lubricant (0.7% of an organosilicon lubricant SE-2175 and 0.3% of an ionic lubricant 1160), 0.2% of a silane coupling agent A-1120 and 0.05% of a spacer were sequentially added to 94.25% of deionized water and stirred at 800 r / min for 30 minutes to obtain a secondary sizing agent.

[0068] Comparative Example 2

[0069] Comparative Example 2 is substantially the same as Example 1, except that the auxiliary film-forming agent contains only 1.5% of the aqueous polyurethane emulsion U6.

[0070] Comparative Example 3:

[0071] At room temperature (25°C), 3% of a main film-forming agent (aqueous epoxy solution NBR-290 with a molecular weight of less than 500), 1.5% of an auxiliary film-forming agent (1% of a low molecular weight epoxy emulsion NBR-210-50G and 0.5% of an aqueous polyurethane emulsion U6), 1% of a lubricant (0.7% of a silicone lubricant SE-2175 and 0.3% of an ionic lubricant 1160) and 0.05% of a spacer were sequentially added to 94.95% deionized water and stirred at 800 r / min for 30 min to obtain a secondary sizing agent.

[0072] Comparative Example 4:

[0073] At room temperature (25°C), 3% of a main film-forming agent (aqueous epoxy solution NBR-290 with a molecular weight of less than 500), 1.5% of an auxiliary film-forming agent (1% of a low molecular weight epoxy emulsion NBR-210-50G and 0.5% of an aqueous polyurethane emulsion U6), 1% of a lubricant (silicone lubricant SE-2175), 0.2% of a silane coupling agent A-1120 and 0.05% of a spacer were added to 94.25% of deionized water and stirred at 800 r / min for 30 minutes to obtain a secondary sizing agent.

[0074] Comparative Example 5:

[0075] At room temperature (25°C), 3% of a main film-forming agent (aqueous epoxy solution NBR-290 with a molecular weight of less than 500), 1.5% of an auxiliary film-forming agent (1% of a low molecular weight epoxy emulsion NBR-210-50G and 0.5% of an aqueous polyurethane emulsion U6), 1% of a lubricant (ionic lubricant 1160), 0.2% of a silane coupling agent A-1120 and 0.05% of a spacer were added to 94.25% of deionized water and stirred at 800 r / min for 30 minutes to obtain a secondary sizing agent.

[0076] Comparative Example 6:

[0077] At room temperature (25°C), 3% of a main film-forming agent (aqueous epoxy solution NBR-290 with a molecular weight of less than 500), 1.5% of an auxiliary film-forming agent (1% of a low molecular weight epoxy emulsion NBR-210-50G and 0.5% of an aqueous polyurethane emulsion U6), 1% of a mineral oil lubricant 7440 (provided by Shanghai Kekai Chemical Co., Ltd. under the trade name 7440, with an effective content of 40wt%), 0.2% of a silane coupling agent A-1120 and 0.05% of a spacer were added to 94.25% of deionized water and stirred at 800r / min for 30 minutes to obtain a secondary sizing agent.

[0078] The secondary sizing agents prepared in Examples 1 to 9 and Comparative Examples 1 to 6 were respectively placed in sizing tanks to perform secondary sizing on silicon carbide fibers (after primary sizing). After passing through the sizing tanks containing the secondary sizing agent, the fibers were dried in a tunnel furnace and wound up using a special winding device; wherein the winding speed was 5 m / min and the drying temperature was 200° C. Afterwards, the fibers after the secondary sizing were woven using a three-dimensional three-way fabric machine, and finally, a high-temperature impregnation method was used to prepare SiC / SiC ceramic-based composite materials, and the performance of the fibers after the secondary sizing and the obtained composite materials were tested, respectively. The test results are shown in Table 1.

[0079] Test method:

[0080] Dry yarn tensile strength: refer to GB / T7690.3 Test methods for reinforcing material yarns Part 3: Determination of fiber breaking force and breaking elongation.

[0081] Abrasion resistance test method: refer to ASTM D3885-2004 standard test method for abrasion resistance of textile fibers, and use Japan Daiei TM-200H yarn friction cohesion tester

[0082] Fabric yarn breakage rate test method: According to the designed process parameters, the total number of warp yarns and the total number of weft yarns in the weaving process can be calculated by the following formula: total number of warp yarns = number of rows × number of layers × number of warp yarn strands; total number of weft yarns = preform length × weft density × number of layers × number of weft yarn strands; total number of normal yarns = number of rows × number of normal yarn strands; according to the calculated number of warp yarns, weft yarns, normal yarns and statistical yarn breakage data, the yarn breakage rate is calculated according to the following formula:

[0083]

[0084] Test methods for mechanical properties of composite materials: flexural strength refers to the American standard ASTM C1341-18 "Standard test method for flexural properties of continuous fiber reinforced materials"; tensile strength refers to GJB 8736-2015 "Test method for tensile properties of continuous fiber reinforced ceramic matrix composites at room temperature"; compressive strength refers to GJB 8736-2015 "Test method for compression properties of continuous fiber reinforced ceramic matrix composites at room temperature".

[0085] Table 1

[0086]

[0087]

[0088] It can be seen from Table 1 that, compared with the comparative example, the silicon carbide fiber modified by the secondary sizing agent in the embodiment of the present invention has excellent wear resistance and folding resistance. At the same time, the silicon carbide fiber modified by the secondary sizing agent can meet the performance requirements of the three-dimensional fabric, and the composite material formed by the three-dimensional fabric has excellent mechanical properties.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A secondary sizing agent, characterized in that The invention comprises the following components: a main film-forming agent, an auxiliary film-forming agent, a lubricant, a silane coupling agent and water; wherein the main film-forming agent is an aqueous epoxy solution, the auxiliary film-forming agent comprises a low molecular weight epoxy emulsion and an aqueous polyurethane emulsion, and the lubricant comprises an organic silicon lubricant and an ionic lubricant.

2. The secondary sizing agent according to claim 1, characterized in that The molecular weight of the waterborne epoxy resin in the waterborne epoxy solution is less than 500, and the low molecular weight epoxy emulsion is a bisphenol A type epoxy emulsion with an epoxy equivalent of less than 300.

3. The secondary sizing agent according to claim 1 or 2, characterized in that Calculated by mass fraction, the contents of the components are as follows: 2-3.5% of the main film-forming agent, 0.35-2% of the auxiliary film-forming agent, 0.8-2.2% of the lubricant, 0.1-0.3% of the silane coupling agent and 92.5-96% of water.

4. The secondary sizing agent according to claim 3, characterized in that The effective content of the aqueous epoxy solution is 50 wt %.

5. The secondary sizing agent according to claim 3, characterized in that The effective content of the low molecular weight epoxy emulsion is 60wt%, and the effective content of the waterborne polyurethane emulsion is 20wt%; In the secondary sizing agent, the content of the low molecular weight epoxy emulsion is 0.25-1.5% by mass, and the content of the waterborne polyurethane emulsion is 0.1-0.5% by mass.

6. The secondary sizing agent according to claim 3, characterized in that The effective content of the silicone lubricant is 42wt%, and the effective content of the ionic lubricant is 90wt%; In the secondary sizing agent, the content of the organic silicon lubricant is 0.5-1.2% by mass, and the content of the ionic lubricant is 0.3-1% by mass.

7. The secondary sizing agent according to claim 1, characterized in that The silane coupling agent is a silane coupling agent with at least two amino groups; Preferably, the silane coupling agent is A-1120 or A-1280.

8. The secondary sizing agent according to claim 3, characterized in that The secondary sizing agent also includes a spacer; wherein the spacer is boric acid; Preferably, in the secondary sizing agent, the content of the spacer is 0.01-0.05% by mass.

9. A method for preparing a secondary sizing agent according to any one of claims 1 to 8, characterized in that: The preparation method comprises: sequentially adding a main film-forming agent, an auxiliary film-forming agent, a lubricant, a silane coupling agent and a spacer into water and mixing them evenly to obtain the secondary sizing agent.

10. Use of a secondary sizing agent according to any one of claims 1 to 8 in modified silicon carbide fiber, characterized in that: The silicon carbide fiber is obtained through one-time sizing, and the modified silicon carbide fiber is used for forming three-dimensional fabric.

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