Carbon nanotube-modified vinyl carbon fiber sizing agent composition, preparation method therefor and use thereof

Abstract

Provided in the present invention are a carbon nanotube-modified vinyl carbon fiber sizing agent composition, a preparation method therefor and the use thereof. The carbon nanotube-modified vinyl carbon fiber sizing agent composition comprises isocyanate-modified vinyl resin prepolymer (film forming agent) and carbon nanotubes, each mol of the isocyanate-modified vinyl resin prepolymer containing 2-4 mol of ester groups, and the isocyanate-modified vinyl resin prepolymer having the structure represented by formula (IV). The sizing agent composition of the present invention is modified by the carbon nanotubes, thus effectively improving the interfacial performance of carbon fibers and a composite material matrix. The film forming agent has low density of ester groups, thus improving the hydrolysis resistance of the composite material, and further improving the resistance to medium corrosion. Polar groups of a molecular structure improve the adhesive force between the sizing agent and the carbon fibers. By means of the polyurethane-modified vinyl resin, in which two ends of a vinyl structure contain unsaturated carbon-carbon double bonds that can be cross-linked and cured with vinyl resin, the carbon fiber composite material is endowed with excellent mechanical properties and excellent fatigue resistance.

Description

A carbon nanotube-modified vinyl carbon fiber sizing agent composition, its preparation method and application Technical Field

[0001] This invention relates to the field of carbon fiber composite materials technology, and in particular to a carbon nanotube modified vinyl carbon fiber sizing agent composition and its preparation method. Background Technology

[0002] Carbon fiber composites are lightweight, high-strength, and highly designable, making them widely used in rail transportation, aerospace, marine vessels, wind power, and new energy fields. Organic fibers are prepared into precursor fibers through processes such as spinning, oiling, and heat setting, and then processed into carbon fibers through pre-oxidation, carbonization, and sizing. The sizing agent coats the surface of the carbon fibers, providing protection and imparting good processing properties. To improve the performance of carbon fiber composites, it is necessary to select a sizing agent type compatible with the resin matrix. Vinyl ester resins have advantages such as good resistance to seawater corrosion and salt spray, and their application is becoming increasingly widespread in marine vessels, offshore wind power, oil drilling platforms, and submarine cables. For vinyl ester resin-based carbon fiber composites, sizing agents containing unsaturated carbon-carbon double bonds must be selected.

[0003] CN112679717A discloses the preparation, product, and application of a multi-purpose self-emulsifying anionic unsaturated polyester carbon fiber sizing agent. It involves polymerization of dibasic fatty acids / or anhydrides, diol monomers, and maleic anhydride, followed by the addition of epoxy resin and a catalyst, and then carboxylation with anhydride to produce the self-emulsifying anionic polyester carbon fiber sizing agent. This type of sizing agent made from unsaturated polyester resin has the following disadvantages: (1) Unsaturated polyester resin is polymerized from diols and diacids, resulting in fewer polar groups on its surface, leading to poor interfacial performance between the sizing agent and carbon fiber; (2) The high proportion of unsaturated double bonds in the unsaturated polyester resin, with their rigid structure, results in poor wear resistance, affecting the carbon fiber weaving process. In addition, traditional unsaturated polyester resin uses a saturated dicarboxylic acid structure with a high proportion of benzene rings. The benzene rings are also rigid structures, which further reduces the wear resistance of carbon fibers. (3) During the synthesis of unsaturated polyester, diols and dicarboxylic acids undergo esterification to produce ester groups. The ester groups are prone to hydrolysis under acidic or alkaline conditions, resulting in poor resistance to seawater and chemical media corrosion, which limits the use of carbon fiber composite materials in marine environments. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a carbon nanotube-modified vinyl carbon fiber sizing agent composition and its preparation method, which features good interfacial performance with carbon fiber, high wear resistance, and low ester group density, and is suitable for carbon fiber vinyl resin composite materials used in the marine field.

[0005] To achieve the above-mentioned objective, a first aspect of the present invention provides a carbon nanotube-modified vinyl carbon fiber sizing agent composition, comprising an isocyanate-modified vinyl resin prepolymer and carbon nanotubes; each mol of the isocyanate-modified vinyl resin prepolymer contains 2 to 4 mol of ester groups; the isocyanate-modified vinyl resin prepolymer has a structure as shown in formula (Ⅳ):

[0006]

[0007] R4 is selected from the following structures:

[0008]

[0009] The R5 structure is as follows:

[0010]

[0011] R1 is H or CH3; n2 is any integer from 1 to 3;

[0012] R2 is H or CH3; n1 is any integer from 1 to 4;

[0013] R3 is selected from one or more of the following structures:

[0014]

[0015] n3 is any integer from 1 to 3.

[0016] Preferably, the isocyanate-modified vinyl resin prepolymer is obtained by reacting a vinyl resin prepolymer with unsaturated carbon-carbon double bonds at the end groups with a diisocyanate epoxy resin with isocyanate groups at the end groups; the diisocyanate epoxy resin molecules with isocyanate groups at the end groups do not contain benzene rings; the vinyl resin prepolymer with unsaturated carbon-carbon double bonds at the end groups includes tetrahydrofuran polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups and bisphenol A polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups; the tetrahydrofuran polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups does not contain benzene rings and has a linear structure within the chain segments; each mol of the isocyanate-modified vinyl resin prepolymer contains 2 to 4 mol or less of ester groups.

[0017] Preferably, the molar ratio of tetrahydrofuran polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups to bisphenol A polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups is 1:5 to 5:1. More preferably, the molar ratio of tetrahydrofuran polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups to bisphenol A polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups is 1:1 to 1:3.

[0018] Preferably, the tetrahydrofuran polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups has a structure as shown in formula (I):

[0019]

[0020] Wherein, R2 is H or CH3; n1 is any integer from 1 to 4. More preferably, R2 is CH3; n1 is 2.

[0021] Preferably, the tetrahydrofuran polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups is obtained by reacting tetrahydrofuran polyether epoxy resin with unsaturated monocarboxylic acids. More preferably, the tetrahydrofuran polyether epoxy resin is formed by etherification and cyclization reactions of tetrahydrofuran polyether, epichlorohydrin, and sodium hydroxide.

[0022] Preferably, the bisphenol A polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups has a structure as shown in formula (II):

[0023]

[0024] Wherein, R1 is H or CH3; n2 is any integer from 1 to 3. More preferably, R1 is CH3; n2 is 3.

[0025] Preferably, the bisphenol A polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups is obtained by reacting bisphenol A polyether epoxy resin with an unsaturated monocarboxylic acid. More preferably, the polyether groups in the bisphenol A polyether epoxy resin are ether bonds introduced by polypropylene glycol or polyethylene glycol.

[0026] Preferably, the diisocyanate epoxy resin with isocyanate end groups has a structure as shown in formula (Ⅲ):

[0027]

[0028] Wherein, R3 is selected from one or more of the following structures:

[0029] ;

[0030] n3 is any integer from 1 to 3.

[0031] Preferably, the diisocyanate epoxy resin with isocyanate end groups is obtained by ring-opening reaction of isocyanate and tetrahydrofuran polyether.

[0032] Preferably, the sizing agent composition is made from the following raw materials in weight percentages:

[0033]

[0034] More preferably, the sizing agent composition is made from the following raw materials in weight percentages:

[0035]

[0036] Preferably, the molecular weight of the tetrahydrofuran polyether epoxy resin is 800 to 1200;

[0037] Preferably, the molecular weight of the bisphenol A polyether epoxy resin is 500 to 700;

[0038] Preferably, the unsaturated monocarboxylic acid is selected from acrylic acid and / or methacrylic acid;

[0039] Preferably, the isocyanate is selected from one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate;

[0040] Preferably, the tetrahydrofuran polyether has a molecular weight of 200–800;

[0041] Preferably, the catalyst is selected from one or more of benzyltrimethylammonium chloride, triphenylphosphine, benzyltriethylammonium chloride, and benzyltriethylammonium bromide;

[0042] Preferably, the polymerization inhibitor is selected from one or more of hydroquinone, p-benzoquinone, tert-butylhydroquinone, 2,6-di-tert-butyl-4-cresol, methylhydroquinone, and p-hydroxyanisole.

[0043] Preferably, the carbon nanotubes are multi-walled carbon nanotubes with an outer diameter of 1–99 nm;

[0044] Preferably, the resistivity of deionized water is greater than 0.5 MΩ·cm;

[0045] Preferably, the emulsifier is an anionic emulsifier, selected from one or more of alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkyl sulfonates, alkylphenol polyoxyethylene ether sulfates, and arylalkylphenol polyoxyethylene ether sulfates.

[0046] A second aspect of the present invention provides a method for preparing the carbon nanotube-modified vinyl carbon fiber sizing agent composition described in the above-mentioned technical solution, comprising the following steps:

[0047] S1, mix tetrahydrofuran polyether epoxy resin, bisphenol A polyether epoxy resin, polymerization inhibitor and unsaturated monocarboxylic acid, add catalyst at 90℃~120℃, and continue to react until the acid value reaches 10±3mgKOH / g to obtain vinyl resin prepolymer with unsaturated carbon-carbon double bonds at the end group.

[0048] The vinyl resin prepolymers with unsaturated carbon-carbon double bonds at the end groups include tetrahydrofuran polyether vinyl resins with unsaturated carbon-carbon double bonds at the end groups and bisphenol A polyether vinyl resins with unsaturated carbon-carbon double bonds at the end groups.

[0049] S2, at 40℃~50℃, tetrahydrofuran polyether is added dropwise to isocyanate and the reaction is continued until the hydroxyl value is 0 mg KOH / g to obtain diisocyanate epoxy resin with isocyanate end group;

[0050] S3, add diisocyanate epoxy resin with isocyanate end group to vinyl resin prepolymer at 55℃~60℃, the isocyanate of the diisocyanate epoxy resin reacts with the hydroxyl group obtained by ring opening of the epoxy group in the vinyl resin prepolymer, and continue the reaction until the isocyanate is 0, to obtain isocyanate modified vinyl resin prepolymer.

[0051] S4, at 60-70℃, emulsifier, carbon nanotubes and water are added sequentially to isocyanate-modified vinyl resin prepolymer to obtain carbon nanotube-modified vinyl carbon fiber sizing agent.

[0052] There is no order restriction for steps S1 and S2.

[0053] Preferably, in step S1, the molar ratio of tetrahydrofuran polyether epoxy resin to bisphenol A polyether epoxy resin is 1:5 to 5:1; more preferably, the molar ratio of tetrahydrofuran polyether epoxy resin to bisphenol A polyether epoxy resin is 1:1 to 1:3.

[0054] Preferably, the tetrahydrofuran polyether epoxy resin is formed by etherification and cyclization reactions of tetrahydrofuran polyether, epichlorohydrin and sodium hydroxide, with a molecular weight of 400 to 1600.

[0055] Preferably, the polyether group in the bisphenol A polyether epoxy resin is an ether bond structure introduced by polypropylene glycol or polyethylene glycol, with a molecular weight of 250 to 750.

[0056] Preferably, the unsaturated monocarboxylic acid is selected from acrylic acid and / or methacrylic acid;

[0057] Preferably, the polymerization inhibitor is selected from one or more of hydroquinone, p-benzoquinone, tert-butylhydroquinone, 2,6-di-tert-butyl-4-methylphenol, methylhydroquinone, and p-hydroxyanisole.

[0058] Preferably, step S1 is as follows: Tetrahydrofuran polyether epoxy resin, bisphenol A polyether epoxy resin, polymerization inhibitor and unsaturated monocarboxylic acid are mixed and stirred for 10 to 15 minutes. A catalyst is added at 90°C, and the temperature is increased to 120°C at a rate of 6°C to 8°C / h. The reaction is continued until the acid value reaches 10 ± 3 mg KOH / g to obtain a vinyl resin prepolymer with unsaturated carbon-carbon double bonds at the end groups.

[0059] Preferably, the reaction temperature in step S2 is 45℃±2℃;

[0060] Preferably, the reaction temperature in step S3 is 60℃±2℃;

[0061] Preferably, the isocyanate is selected from one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate;

[0062] Preferably, the tetrahydrofuran polyether has a molecular weight of 200–800.

[0063] Preferably, the emulsifier is an anionic emulsifier, and the emulsifier is selected from one or more of alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkyl sulfonates, alkylphenol polyoxyethylene ether sulfates, and arylalkylphenol polyoxyethylene ether sulfates;

[0064] Preferably, the carbon nanotubes are multi-walled carbon nanotubes with an outer diameter of 1–99 nm;

[0065] Preferably, the resistivity of deionized water is greater than 0.5 MΩ·cm;

[0066] Preferably, the reaction temperature in step S4 is 65℃±2℃.

[0067] Preferably, step S4 is as follows: at 65℃±2℃, an emulsifier is added to the isocyanate-modified vinyl resin prepolymer, and the mixture is stirred for 10-15 minutes. Then, carbon nanotubes are added, and the mixture is stirred for another 10-15 minutes. Next, 30% by mass of deionized water is added, and the mixture is stirred for another 55-65 minutes. Finally, the remaining deionized water is added, and the mixture is stirred for another 55-65 minutes to obtain a carbon nanotube-modified vinyl carbon fiber sizing agent.

[0068] A third aspect of the present invention provides the application of the carbon nanotube-modified vinyl carbon fiber sizing agent composition described in the foregoing technical solutions or the carbon nanotube-modified vinyl carbon fiber sizing agent composition obtained by the preparation method described in the above technical solutions in the preparation of carbon fiber vinyl resin composite materials suitable for marine environments.

[0069] A fourth aspect of the present invention provides a carbon fiber vinyl resin composite material suitable for marine environments, comprising, from the inside out, carbon fibers, a carbon nanotube-modified vinyl carbon fiber sizing agent composition, and a vinyl resin matrix.

[0070] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0071] The carbon nanotube-modified vinyl carbon fiber sizing agent composition of this invention utilizes carbon nanotube modification, which effectively increases the interfacial properties between carbon fiber and the composite matrix. The isocyanate-modified vinyl resin prepolymer in the sizing agent acts as a film-forming agent, with a lower proportion of benzene rings and unsaturated double bonds compared to existing unsaturated polyesters. The tetrahydrofuran linear structure improves wear resistance. The low ester group density of the film-forming agent enhances the composite material's hydrolysis resistance and further improves its resistance to media corrosion. The presence of polar groups in the molecular structure improves the adhesion between the sizing agent and the carbon fiber. By modifying the vinyl resin with polyurethane, the vinyl structure contains unsaturated carbon-carbon double bonds at both ends, allowing for cross-linking and curing with the vinyl resin, imparting excellent mechanical properties to the carbon fiber composite material. The polyurethane structure also contributes to the composite material's excellent fatigue resistance. Specifically:

[0072] 1) Isocyanate-modified vinyl resin prepolymer is a polyurethane-modified vinyl resin structure with unsaturated carbon-carbon double bonds at both ends of the vinyl resin, which can crosslink and cure with the vinyl resin matrix, giving carbon fiber vinyl resin composites excellent mechanical properties; isocyanate-modified vinyl resin prepolymer is also modified with polyurethane structure, giving carbon fiber vinyl resin composites excellent fatigue resistance.

[0073] 2) This invention uses isocyanate-modified vinyl resin prepolymer as a film-forming agent. Each mol of the isocyanate-modified vinyl resin prepolymer contains less than 2 mol of ester groups. In contrast, the same molecular weight of the existing unsaturated polyester sizing agent contains 4 to 7 mol of ester groups. The ester group density in the film-forming agent is greatly reduced, making the sizing agent and the resulting carbon fiber vinyl resin composite material more resistant to hydrolysis and corrosion (such as seawater and chemical media corrosion).

[0074] In some preferred embodiments of the present invention, when the unsaturated monocarboxylic acid is methacrylic acid, the ester group of the film-forming agent is protected by the side chain methyl group, which can further improve the hydrolysis resistance and the resistance to seawater and chemical media corrosion.

[0075] 3) To address the issue of low surface energy of carbon fibers, this invention introduces polar groups such as ether bonds, hydroxyl groups, and isocyanate structures into the film-forming agent, thereby improving the adhesion between the sizing agent and the carbon fiber.

[0076] 4) The proportion of benzene rings and unsaturated double bonds in the film-forming agent is lower than that of unsaturated polyester, and the linear structure of tetrahydrofuran improves the wear resistance.

[0077] 5) In the sizing agent composition of the present invention, the isocyanate-modified vinyl resin prepolymer is attached to the outside of carbon nanotubes to form a film during preparation. The carbon nanotubes have an aspect ratio structure. When the isocyanate-modified vinyl resin prepolymer is uniformly wrapped around the carbon fiber surface, it can effectively increase the surface roughness and specific surface area of ​​the carbon fiber, thereby effectively increasing the interfacial properties between the carbon fiber and the composite matrix. Detailed Implementation

[0078] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0079] This invention provides a carbon nanotube-modified vinyl carbon fiber sizing agent composition, made from the following raw materials in weight percentages:

[0080]

[0081] In this invention, tetrahydrofuran polyether epoxy resin reacts with unsaturated monocarboxylic acid to generate tetrahydrofuran polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups, having the structure shown in formula (I):

[0082]

[0083] Where R2 is H or CH3; n1 is any integer from 1 to 4, such as 1, 2, 3, 4.

[0084] In this invention, the tetrahydrofuran polyether epoxy resin does not contain benzene rings and has a linear structure within its chain segments, thus improving wear resistance and flexibility. Preferably, the tetrahydrofuran polyether epoxy resin is formed by etherification and cyclization reactions of tetrahydrofuran polyether, epichlorohydrin, and sodium hydroxide, with a molecular weight of 400-1600. More preferably, the tetrahydrofuran polyether epoxy resin used in this invention has a molecular weight of 800-1200. In some specific embodiments of this invention, the tetrahydrofuran polyether epoxy resin is a (Ⅰ) compound of formula R2 being CH3 and n1 being 2, with a molecular weight of 1050. In this invention, the weight percentage content of the tetrahydrofuran polyether epoxy resin in the raw materials is preferably 12.0%-24.0%; in some specific embodiments of this invention, the weight percentage content of the tetrahydrofuran polyether epoxy resin is 20.38%, 23.72%, 23.61%, 12.84%, and 12.43%.

[0085] In this invention, the bisphenol A polyether epoxy resin reacts with an unsaturated monocarboxylic acid to generate a vinyl resin with unsaturated carbon-carbon double bonds at the end groups, having a structure as shown in formula (II):

[0086]

[0087] Wherein, R1 is H or CH3; n2 is any integer from 1 to 3. More preferably, R1 is CH3; n2 is 3.

[0088] In this invention, the bisphenol A polyether epoxy resin contains ether bonds, which are hydrophilic groups and can improve the emulsification effect of the polymer. Preferably, the polyether groups in the bisphenol A polyether epoxy resin are ether bonds introduced by polypropylene glycol or polyethylene glycol, with a molecular weight of 250-750. In some preferred embodiments of this invention, the bisphenol A polyether epoxy resin is a compound of formula (II) with R1 being CH3 and n2 being 3, and a molecular weight of 667. In this invention, the weight percentage content of bisphenol A polyether epoxy resin in the raw materials is preferably 12.0%-24.5%; in some specific embodiments of this invention, the weight percentage content of tetrahydrofuran polyether epoxy resin is 12.95%, 15.07%, 15%, 24.46%, and 23.68%.

[0089] In this invention, the unsaturated monocarboxylic acid is preferably selected from acrylic acid and / or methacrylic acid. In some preferred embodiments of this invention, the unsaturated monocarboxylic acid is methacrylic acid, and the ester group of the isocyanate-modified vinyl resin prepolymer (film-forming agent) prepared from methacrylic acid is protected by the side chain methyl group, which can further improve the hydrolysis resistance and the resistance to seawater and chemical media corrosion. In this invention, the weight percentage of the unsaturated monocarboxylic acid in the raw material is preferably 6.0% to 9.0%; in some specific embodiments of this invention, the weight percentage of the unsaturated monocarboxylic acid in the raw material is 6.68%, 7.77%, 7.73%, 8.41%, and 8.14%.

[0090] In this invention, the molar ratio of tetrahydrofuran polyether epoxy resin and bisphenol A polyether epoxy resin in the raw materials is preferably 1:5 to 5:1, more preferably 1:1 to 1:3; in some specific embodiments of this invention, the molar ratio of tetrahydrofuran polyether epoxy resin and bisphenol A polyether epoxy resin in the raw materials is 1:1 or 1:3. In this invention, the molar number of unsaturated monocarboxylic acids in the raw materials is the sum of the molar numbers of tetrahydrofuran polyether epoxy resin and bisphenol A polyether epoxy resin. Further, the molar ratio of tetrahydrofuran polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups and bisphenol A polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups obtained from the above-mentioned raw materials is 1:5 to 5:1. More preferably, the molar ratio of tetrahydrofuran polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups and bisphenol A polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups is 1:1 to 1:3. The two epoxy resins react with unsaturated monocarboxylic acids to generate vinyl resins with unsaturated carbon-carbon double bonds at the end groups. These resins can be cross-linked and cured with the composite matrix to improve interfacial properties. At the same time, the molecular structure does not contain unsaturated carbon-carbon double bonds, has a low ester group density, and exhibits good resistance to seawater and chemical media corrosion.

[0091] In this invention, tetrahydrofuran polyether epoxy resin and bisphenol A polyether epoxy resin react with the unsaturated monocarboxylic acid, respectively. The catalyst for the reaction is selected from one or more of benzyltrimethylammonium chloride, triphenylphosphine, benzyltriethylammonium chloride, and benzyltriethylammonium bromide; more preferably, the catalyst is triphenylphosphine. In this invention, the catalyst is preferably 0.24% to 0.25% by weight in the raw materials. A polymerization inhibitor may also be added to the above reaction. The polymerization inhibitor is preferably selected from one or more of hydroquinone, p-benzoquinone, tert-butylhydroquinone, 2,6-di-tert-butyl-4-cresol, methylhydroquinone, and p-hydroxyanisole; more preferably, the polymerization inhibitor is methylhydroquinone. In this invention, the polymerization inhibitor is preferably 0.02% to 0.03% by weight in the raw materials.

[0092] In this invention, the isocyanate reacts with tetrahydrofuran polyether to generate a diisocyanate epoxy resin with isocyanate end groups. The flexible segments and cyano groups further improve wear resistance and adhesion to carbon fibers. The diisocyanate epoxy resin with isocyanate end groups has the structure shown in formula (Ⅲ):

[0093]

[0094] Wherein, R3 is selected from one or more of the following structures:

[0095] ;

[0096] n3 is any integer from 1 to 3, such as 1, 2, 3.

[0097] In this invention, the molar ratio of isocyanate to tetrahydrofuran polyether is 2:1 to 5:1, and more preferably 2:1 to 3:1. In some preferred embodiments of this invention, the reaction of linear isocyanate with high isocyanate content (e.g., NCO content of 45% or more) with high molecular weight tetrahydrofuran polyether (e.g., molecular weight of 650 or more) can further improve the wear resistance of carbon fiber vinyl resin composites, indicating that reducing the content of benzene ring rigid structures can effectively improve wear resistance.

[0098] In this invention, the isocyanate is preferably one or more selected from toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate; more preferably, 4,4-diphenylmethane diisocyanate or hexamethylene diisocyanate. In this invention, the weight percentage of the isocyanate in the raw material is preferably 3.5% to 10.9%; in some specific embodiments of this invention, the weight percentage of the isocyanate in the raw material is 10.87%, 6.33%, 6.30%, 6.85%, or 3.98%.

[0099] In this invention, the structure of the tetrahydrofuran polyether is shown in the following formula, where n3 is any integer from 1 to 3, such as 1, 2, or 3. In this invention, the molecular weight of the tetrahydrofuran polyether is preferably 200 to 800; more preferably 250. In this invention, the weight percentage of the tetrahydrofuran polyether in the raw material is preferably 2.0% to 7.7%; in some specific embodiments of this invention, the weight percentage of the tetrahydrofuran polyether in the raw material is 4.85%, 2.82%, 2.81%, 3.06%, or 7.69%.

[0100]

[0101] In this invention, a diisocyanate epoxy resin with isocyanate end groups and a vinyl resin prepolymer with unsaturated carbon-carbon double bonds end groups are reacted, and the isocyanate reacts with the hydroxyl groups obtained after ring opening of the epoxy group to obtain an isocyanate-modified vinyl resin prepolymer.

[0102] In this invention, isocyanate-modified vinyl resin prepolymer is mixed with carbon nanotubes, and an emulsifier is added. The carbon nanotubes have a multi-walled structure, are regular hexagonal, with an outer diameter of several nanometers to tens of nanometers and a length reaching the micrometer level. The carbon fibers have a diameter of 5 to 10 micrometers. The carbon nanotubes are uniformly dispersed in the isocyanate-modified vinyl resin prepolymer, baked at high temperature to form a film, and then applied to the surface of the carbon fibers. The carbon nanotubes improve the surface roughness of the carbon fibers, increase the specific surface area, and thus improve the interfacial properties between the sizing agent and the carbon fibers and resin matrix. More preferably, the mass ratio of carbon nanotubes added is 0.5% to 1.5%, and in even more preferred embodiments, the addition amounts are 0.8% and 1.2%, respectively. In this invention, the carbon nanotubes are preferably Tube M204 carbon nanotubes.

[0103] In this invention, the resistivity of the deionized water is preferably greater than 0.5 MΩ·cm. The weight ratio of the deionized water in the raw materials is preferably 39.0% to 40.0%; in some specific embodiments of this invention, the weight ratio of deionized water in the raw materials is 39.80%, 39.92%, and 40.00%.

[0104] In this invention, the emulsifier is an anionic emulsifier, preferably selected from alkylbenzene sulfonate, alkylnaphthalene sulfonate, alkyl sulfonate, alkylphenol polyoxyethylene ether sulfate, and arylalkylphenol polyoxyethylene ether sulfate; preferably, the emulsifier is alkylphenol polyoxyethylene ether sulfate. In this invention, the weight ratio of the emulsifier in the raw materials is preferably 2.5% to 3.0%; in some specific embodiments of this invention, the weight ratio of the emulsifier in the raw materials is preferably 2.99% or 3%.

[0105] The present invention also provides a method for preparing the above-mentioned vinyl carbon fiber sizing agent composition, comprising the following steps:

[0106] S1. Tetrahydrofuran polyether epoxy resin and bisphenol A polyether epoxy resin are added to a reactor, along with a polymerization inhibitor and an unsaturated monocarboxylic acid. The mixture is stirred for 10–15 minutes, heated to 90±2℃, and a catalyst is added. The temperature is maintained at a rate of 6–8℃ / h and raised to 120±2℃. The reaction continues until the acid value reaches 10±3 mgKOH / g, yielding vinyl resin prepolymers with unsaturated double bonds at the ends. These prepolymers include tetrahydrofuran polyether vinyl resins with unsaturated carbon-carbon double bonds at the ends and bisphenol A polyether vinyl resins with unsaturated carbon-carbon double bonds at the ends.

[0107] Reaction 1a: Generates tetrahydrofuran polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups.

[0108]

[0109] Tetrahydrofuran polyether epoxy resin unsaturated monocarboxylic acid

[0110]

[0111] Where R2 is H or CH3; n1 is any integer from 1 to 4.

[0112] Reaction 1b: Generates bisphenol A polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups.

[0113]

[0114] Where R1 is H or CH3; n2 is any integer from 1 to 3.

[0115] S2, the isocyanate is added to another reactor, the temperature is raised to 45±2℃, tetrahydrofuran polyether is added dropwise, and the reaction is continued until the hydroxyl value is 0mgKOH / g, to obtain diisocyanate resin with isocyanate end groups.

[0116]

[0117] n3 = 1-3; R3 is one or more of the following structures:

[0118]

[0119] S3, the temperature of the reactor containing the vinyl resin prepolymer with unsaturated double bonds at the end group is reduced to 60±2℃, and the diisocyanate resin with isocyanate at the end group prepared in S2 is added into the reactor to continue the reaction until the isocyanate content is 0, and the isocyanate modified vinyl resin prepolymer is obtained.

[0120]

[0121] R4 and R5 are selected from one or both of the following structures:

[0122]

[0123] The structure of R6 is as follows:

[0124]

[0125] In step S4, the isocyanate-modified vinyl resin prepolymer prepared in step S3 is added to an emulsification reactor, heated to 65±2℃, an emulsifier is added, and the mixture is stirred for 10–15 minutes. Carbon nanotubes are then added, and the mixture is stirred for another 10–15 minutes. Deionized water is added dropwise while maintaining the reactor temperature at 65±5℃. When the deionized water content reaches 30%, the addition of deionized water is stopped, and the mixture is stirred for 60±5 minutes. The remaining deionized water is then added, and the mixture is stirred for another 60±5 minutes to obtain a carbon nanotube-modified vinyl carbon fiber sizing agent.

[0126] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but these should not be construed as limiting the scope of protection of the present invention. Experimental methods in the following embodiments without specific conditions are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials without specified synthesis methods are commercially available.

[0127] Example 1

[0128] 1050g of tetrahydrofuran polyether epoxy resin (1mol, molecular weight 1050g / mol) and 667g of bisphenol A polyether epoxy resin (1mol, molecular weight 667g / mol) were added to a reactor, along with 1.55g of methylhydroquinone and 344g of methacrylic acid (4mol). The mixture was stirred for 10–15 minutes, heated to 90±2℃, and then 12.9g of triphenylphosphine was added. The temperature was increased to 120±2℃ at a rate of 6–8℃ / h. The reaction was continued until the acid value reached 10±3mg KOH / g, yielding a vinyl resin prepolymer with unsaturated double bonds at the end groups.

[0129] 560g of 4,4-diphenylmethane diisocyanate (MM 103C, NCO content 29.0%-30.0%) was added to another reactor, heated to 45±2℃, and 250g of tetrahydrofuran polyether (1mol, molecular weight 250g / mol) was added dropwise. The reaction was continued until the hydroxyl value was 0mg KOH / g, to obtain a diisocyanate resin with isocyanate end groups.

[0130] The temperature of the reactor containing the vinyl resin prepolymer was lowered to 60±2℃, and the diisocyanate resin prepared in the previous step was added into the reactor to continue the reaction. The reaction temperature was controlled at 60±2℃ until the isocyanate content was 0, and the isocyanate modified vinyl resin prepolymer was obtained.

[0131] The vinyl resin prepolymer prepared in the previous step was added to an emulsification reactor, and the temperature was raised to 65±2℃. 154.6 g of alkylphenol polyoxyethylene ether sulfate emulsifier was added, and the mixture was stirred for 10–15 minutes. Then, 51.5 g of carbon nanotubes (TubeM204) was added, and stirring continued for 10–15 minutes. Deionized water was added dropwise, maintaining the reactor temperature at 65±5℃. When 618.3 g of deionized water was added, the addition was stopped, and the mixture was stirred for 60±5 minutes. Then, 1442.7 g of deionized water was added, and the mixture was stirred for 60±5 minutes to obtain a carbon nanotube-modified vinyl carbon fiber sizing agent.

[0132] Example 2

[0133] 1050 g of tetrahydrofuran polyether epoxy resin (1 mol, molecular weight 1050 g / mol) and 667 g of bisphenol A polyether epoxy resin (1 mol, molecular weight 667 g / mol) were added to a reactor, along with 1.32 g of methylhydroquinone and 344 g of methacrylic acid (4 mol). The mixture was stirred for 10–15 minutes, heated to 90 ± 2 °C, and then 11.1 g of triphenylphosphine was added. The temperature was increased to 120 ± 2 °C at a rate of 6–8 °C / h. The reaction was continued until the acid value reached 10 ± 3 mg KOH / g, yielding a vinyl resin prepolymer with unsaturated double bonds at the end groups.

[0134] 280g of 4,4-diphenylmethane diisocyanate (MM 103C, NCO content 29.0-30.0%) was added to another reactor, heated to 45±2℃, and 125g of tetrahydrofuran polyether (0.5mol, molecular weight 250g / mol) was added dropwise. The reaction was continued until the hydroxyl value was 0mg KOH / g, to obtain a diisocyanate resin with isocyanate end groups.

[0135] The temperature of the reactor containing the vinyl resin prepolymer was lowered to 60±2℃, and the diisocyanate resin prepared in the previous step was added into the reactor to continue the reaction. The reaction temperature was controlled at 60±2℃ until the isocyanate content was 0, and the isocyanate modified vinyl resin prepolymer was obtained.

[0136] The vinyl resin prepolymer prepared in the previous step was added to an emulsification reactor, and the temperature was raised to 65±2℃. 132.8 g of alkylphenol polyoxyethylene ether sulfate emulsifier was added, and the mixture was stirred for 10–15 minutes. Then, 44.2 g of carbon nanotubes (Tube M204) was added, and stirring continued for 10–15 minutes. Deionized water was added dropwise, maintaining the reactor temperature at 65±5℃. When 531.1 g of deionized water was added, the addition was stopped, and the mixture was stirred for 60±5 minutes. Then, 1239.2 g of deionized water was added, and the mixture was stirred for another 60±5 minutes to obtain the carbon nanotube-modified vinyl carbon fiber sizing agent.

[0137] Example 3

[0138] 1050g of tetrahydrofuran polyether epoxy resin (1mol, molecular weight 1050g / mol) and 667g of bisphenol A polyether epoxy resin (1mol, molecular weight 667g / mol) were added to a reactor, along with 1.32g of methylhydroquinone and 344g of methacrylic acid (4mol). The mixture was stirred for 10–15 minutes, heated to 90±2℃, and then 11.1g of triphenylphosphine was added. The temperature was increased to 120±2℃ at a rate of 6–8℃ / h. The reaction was continued until the acid value reached 10±3mg KOH / g, yielding a vinyl resin prepolymer with unsaturated double bonds at the end groups.

[0139] 280g of 4,4-diphenylmethane diisocyanate (MM 103C, NCO content 29.0-30.0%) was added to another reactor, heated to 45±2℃, and 125g of tetrahydrofuran polyether (0.5mol, molecular weight 250 g / mol) was added dropwise. The reaction was continued until the hydroxyl value was 0mg KOH / g, to obtain a diisocyanate resin with isocyanate end groups.

[0140] The temperature of the reactor containing the vinyl resin prepolymer was lowered to 60±2℃, and the diisocyanate resin prepared in the previous step was added into the reactor to continue the reaction. The reaction temperature was controlled at 60±2℃ until the isocyanate content was 0, and the isocyanate modified vinyl resin prepolymer was obtained.

[0141] The vinyl resin prepolymer prepared in the previous step was added to an emulsification reactor, and the temperature was raised to 65±2℃. 132.8g of alkylphenol polyoxyethylene ether sulfate emulsifier was added, and the mixture was stirred for 10–15 minutes. Then, 66.3g of carbon nanotubes (Tube M204) was added, and stirring continued for 10–15 minutes. Deionized water was added dropwise, maintaining the reactor temperature at 65±5℃. When 531.1g of deionized water was added, the addition was stopped, and the mixture was stirred for 60±5 minutes. Then, 1239.2g of deionized water was added, and the mixture was stirred for another 60±5 minutes to obtain the carbon nanotube-modified vinyl carbon fiber sizing agent.

[0142] The difference between Example 3 and Example 2 is that the proportion of carbon nanotubes is increased to 1.2%.

[0143] Example 4

[0144] 525 g of tetrahydrofuran polyether epoxy resin (0.5 mol, molecular weight 1050 g / mol) and 1000 g of bisphenol A polyether epoxy resin (1.5 mol, molecular weight 667 g / mol) were added to a reactor, along with 1.22 g of methylhydroquinone and 344 g of methacrylic acid (4 mol). The mixture was stirred for 10–15 minutes, heated to 90 ± 2 °C, and then 10.2 g of triphenylphosphine was added. The temperature was maintained at a rate of 6–8 °C / h and increased to 120 ± 2 °C. The reaction was continued until the acid value reached 10 ± 3 mg KOH / g, yielding a vinyl resin prepolymer with unsaturated double bonds at the end groups.

[0145] 280 g of 4,4-diphenylmethane diisocyanate (MM 103C, NCO content 29.0-30.0%) was added to another reactor, heated to 45±2℃, and 125 g of tetrahydrofuran polyether (0.5 mol, molecular weight 250 g / mol) was added dropwise. The reaction was continued until the hydroxyl value was 0 mg KOH / g, to obtain a diisocyanate resin with isocyanate end groups.

[0146] The temperature of the reactor containing the vinyl resin prepolymer was lowered to 60±2℃, and the diisocyanate resin prepared in the previous step was added into the reactor to continue the reaction. The reaction temperature was controlled at 60±2℃ until the isocyanate content was 0, and the isocyanate modified vinyl resin prepolymer was obtained.

[0147] The vinyl resin prepolymer prepared in the previous step was added to an emulsification reactor, and the temperature was raised to 65±2℃. 122,4-alkylphenol polyoxyethylene ether sulfate emulsifier was added, and the mixture was stirred for 10–15 minutes. Then, 48.9 g of carbon nanotubes (Tube M204) was added, and stirring continued for 10–15 minutes. Deionized water was added dropwise, maintaining the reactor temperature at 65±5℃. When 489.7 g of deionized water was added, the addition was stopped, and the mixture was stirred for 60±5 minutes. Then, 1142.7 g of deionized water was added, and the mixture was stirred for another 60±5 minutes to obtain a carbon nanotube-modified vinyl carbon fiber sizing agent.

[0148] The difference between Example 4 and Example 3 is that the molar ratio of tetrahydrofuran polyether epoxy resin and bisphenol A polyether epoxy resin is adjusted from 1:1 to 1:3.

[0149] Example 5

[0150] 525g of tetrahydrofuran polyether epoxy resin (0.5mol, molecular weight 1050g / mol) and 1000g of bisphenol A polyether epoxy resin (1.5mol, molecular weight 667g / mol) were added to a reactor, along with 1.27g of methylhydroquinone and 344g of methacrylic acid (4mol). The mixture was stirred for 10–15 minutes, heated to 90±2℃, and then 10.2g of triphenylphosphine was added. The temperature was maintained at a rate of 6–8℃ / h and increased to 120±2℃. The reaction was continued until the acid value reached 10±3mg KOH / g, yielding a vinyl resin prepolymer with unsaturated double bonds at the end groups.

[0151] 168g of hexamethylene diisocyanate (NCO content 49.0-50.0%) was added to another reactor, heated to 45±2℃, and 325g of tetrahydrofuran polyether (0.5mol, molecular weight 650g / mol) was added dropwise. The reaction was continued until the hydroxyl value was 0mg KOH / g, to obtain diisocyanate resin with isocyanate end groups.

[0152] The temperature of the reactor containing the vinyl resin prepolymer was lowered to 60±2℃, and the diisocyanate resin prepared in the previous step was added into the reactor to continue the reaction. The reaction temperature was controlled at 60±2℃ until the isocyanate content was 0, and the isocyanate modified vinyl resin prepolymer was obtained.

[0153] The vinyl resin prepolymer prepared in the previous step was added to an emulsification reactor, and the temperature was raised to 65±2℃. 126.7 g of alkylphenol polyoxyethylene ether sulfate emulsifier was added, and the mixture was stirred for 10–15 minutes. Then, 33.8 g of carbon nanotubes (Tube M204) was added, and stirring continued for 10–15 minutes. Deionized water was added dropwise, maintaining the reactor temperature at 65±5℃. When 506.9 g of deionized water was added, the addition was stopped, and the mixture was stirred for 60±5 minutes. Then, 1182.7 g of deionized water was added, and the mixture was stirred for another 60±5 minutes to obtain the carbon nanotube-modified vinyl carbon fiber sizing agent.

[0154] Comparative Example 1

[0155] 684 g of propylene glycol was added to a reaction vessel, and the temperature was raised to 100 ± 2 °C. 747 g of phthalic acid was added, and the mixture was stirred for 30 min. The temperature was then raised to 210 °C. The reaction was terminated when the acid value was less than 10 mg KOH / g. The temperature was lowered to 160 °C, and 432 g of maleic anhydride was added. The acid value reached 10-16 mg KOH / g, thus preparing an unsaturated polyester resin.

[0156] The unsaturated polyester resin prepared in the previous step was added to an emulsification reactor, and the temperature was raised to 65±2℃. 126.7g of alkylphenol polyoxyethylene ether sulfate emulsifier was added, and the mixture was stirred for 10–15 minutes. Then, 33.8g of carbon nanotubes (Tube M204) was added, and stirring continued for 10–15 minutes. Deionized water was added dropwise, maintaining the reactor temperature at 65±5℃. When 506.9g of deionized water was added, the addition was stopped, and the mixture was stirred for 60±5 minutes. Then, 1182.7g of deionized water was added, and the mixture was stirred for another 60±5 minutes to obtain a carbon nanotube-modified unsaturated polyester resin sizing agent.

[0157] Experimental Example

[0158] Carbon fibers were prepared using the carbon nanotube-modified vinyl carbon fiber sizing agent obtained in Examples 1-5 above, and carbon nanotube-modified unsaturated polyester resin sizing agent prepared in Comparative Example 1. Carbon fiber composite materials were then prepared using a pultrusion molding process. The carbon fiber abrasion resistance cycles, carbon fiber sizing amount, interlaminar shear strength of the carbon fiber composite short beam, and seawater retention rate were tested. The test results are shown in Table 1.

[0159] Carbon fiber preparation method: Carbon fiber is sized by winding it around a roller and entering a sizing tank, then baked in an oven at 150℃ to remove moisture, and finally rolled into carbon fiber. The sizing amount of carbon fiber is 1.2-1.5%.

[0160] The carbon fiber specification is: 12KT700 carbon fiber;

[0161] Pultrusion process for preparing carbon fiber composite materials: Carbon fibers pass through an impregnation tank into a mold containing epoxy vinyl ester resin. The mold has a cross-sectional size of 100mm*4mm and a length of 90cm. The three temperature zones are 120℃, 150℃, and 140℃, respectively. The carbon fiber composite material is then prepared by a traction machine.

[0162] The epoxy vinyl ester resin: MERICAN 30-900 epoxy vinyl ester resin

[0163] Carbon fiber abrasion resistance test: Referring to the reciprocating roller method of yarn abrasion test method FZT01058, a self-made abrasion resistance test instrument was used. The weight was 50g, the speed was 120r / min, and the instrument was covered with 600-grit sandpaper. The number of times the fiber broke was recorded as the number of abrasion resistance cycles.

[0164] The carbon fiber sizing amount test was conducted according to Appendix B of GB / T 26752-2011 Polyacrylonitrile Carbon Fiber: Test Method for Carbon Fiber Sizing Agent Content.

[0165] The interlaminar shear strength of carbon fiber composite short beams was determined according to ISO-14130.

[0166] Seawater (water) retention rate test for carbon fiber composite materials: Carbon fiber composite materials were prepared into bending specimens according to GB / T 1449-2005. A portion of these specimens were then placed in a reaction flask containing seawater at 98℃ and boiled for 2 hours. After removal, the specimens were allowed to cool naturally, and surface moisture was removed using absorbent paper. The specimens were then placed in a laboratory environment at 23±2℃ for 24 hours. The bending strength was then tested according to GB / T 1449-2005. The ratio of the bending strength after boiling to the bending strength before boiling is recorded as the seawater (water) retention rate of the carbon fiber composite material.

[0167] Table 1. Test results of Examples 1-5

[0168]

[0169] As shown in Table 1:

[0170] 1. Compared with Comparative Example 1, the carbon fiber composite materials prepared using the sizing agents of Examples 1-5 showed a significant improvement in abrasion resistance. The interlaminar shear strength of the carbon fiber composite materials prepared using the sizing agents of Examples 1-5 was also significantly improved compared with Comparative Example 1. The film-forming agent in Comparative Example 1 was an unsaturated polyester resin, which had a high proportion of unsaturated double bonds and benzene rings, resulting in poor abrasion resistance and thus a low abrasion resistance. Furthermore, although carbon nanotubes were used in the comparative examples, the unsaturated polyester resin lacked polar groups, leading to poor interfacial bonding with the fiber, and therefore a lower interlaminar shear strength compared to Examples 1-5.

[0171] 2. Example 5 uses linear hexamethylene diisocyanate diisocyanate and high molecular weight tetrahydrofuran polyether, which has the highest wear resistance, reaching 112 times, indicating that reducing the content of benzene ring rigid structure can further effectively improve the wear resistance.

[0172] 3. In Example 3, by increasing the carbon nanotube content, the interlaminar shear strength can be further improved. On this basis, increasing or decreasing the proportion of tetrahydrofuran polyether epoxy resin will reduce the interlaminar shear performance.

[0173] 4. Compared with the example, the boiling water retention rate of Comparative Example 1 decreased significantly. The main reason is that 1 mol of the sizing agent of Comparative Example 1 contains 10-12 mol of ester groups, while 1 mol of the example contains 2-4 mol of ester groups. The molecular weights of the two are similar, and the higher density of ester groups leads to a decrease in the boiling water retention rate.

[0174] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A carbon nanotube-modified vinyl carbon fiber sizing agent composition, characterized in that, It includes isocyanate-modified vinyl resin prepolymer and carbon nanotubes; each mol of the isocyanate-modified vinyl resin prepolymer contains 2 to 4 mol of ester groups; The isocyanate-modified vinyl resin prepolymer has the structure shown in formula (Ⅳ): ； R4 is selected from the following structures: ； The R5 structure is as follows: ； R1 is H or CH3; n2 is any integer from 1 to 3; R2 is H or CH3; n1 is any integer from 1 to 4; R3 is selected from one or more of the following structures: n3 is any integer from 1 to 3.

2. The carbon nanotube-modified vinyl carbon fiber sizing agent composition according to claim 1, characterized in that, The isocyanate-modified vinyl resin prepolymer is obtained by reacting a vinyl resin prepolymer with unsaturated carbon-carbon double bonds at the end with a diisocyanate epoxy resin with isocyanate groups at the end. Vinyl resin prepolymers with unsaturated carbon-carbon double bonds at the end groups include tetrahydrofuran polyether vinyl resins with unsaturated carbon-carbon double bonds at the end groups and bisphenol A polyether vinyl resins with unsaturated carbon-carbon double bonds at the end groups.

3. The carbon nanotube-modified vinyl carbon fiber sizing agent composition according to claim 2, characterized in that, The molar ratio of tetrahydrofuran polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups to bisphenol A polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups is 1:5 to 5:1; preferably, the molar ratio of tetrahydrofuran polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups to bisphenol A polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups is 1:1 to 1:

3.

4. The carbon nanotube-modified vinyl carbon fiber sizing agent composition according to claim 2, characterized in that, Tetrahydrofuran polyether vinyl resins with unsaturated carbon-carbon double bonds at the end groups have the structure shown in formula (I): ; Wherein, R2 is H or CH3; n1 is any integer from 1 to 4. Preferably, R2 is CH3; n1 is 2. Preferably, the tetrahydrofuran polyether vinyl resin with unsaturated carbon-carbon double bonds at the end is obtained by reacting tetrahydrofuran polyether epoxy resin with unsaturated monocarboxylic acid. More preferably, the tetrahydrofuran polyether epoxy resin is formed by etherification and cyclization reactions of tetrahydrofuran polyether, epichlorohydrin, and sodium hydroxide.

5. The carbon nanotube-modified vinyl carbon fiber sizing agent composition according to claim 2, characterized in that, Bisphenol A polyether vinyl resins with unsaturated carbon-carbon double bonds at the ends have the structure shown in formula (II): Wherein, R1 is H or CH3; n2 is any integer from 1 to 3. Preferably, R1 is CH3; n2 is 3. Preferably, the bisphenol A polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups is obtained by reacting bisphenol A polyether epoxy resin with unsaturated monocarboxylic acids. More preferably, the polyether groups in the bisphenol A polyether epoxy resin are ether bonds introduced by polypropylene glycol or polyethylene glycol.

6. The carbon nanotube-modified vinyl carbon fiber sizing agent composition according to claim 2, characterized in that, The diisocyanate epoxy resin with isocyanate end groups has a structure as shown in formula (Ⅲ): ; Wherein, R3 is selected from one or more of the following structures: ； n3 is any integer from 1 to 3. Preferably, the diisocyanate epoxy resin with isocyanate end groups is obtained by ring-opening reaction of isocyanate and tetrahydrofuran polyether.

7. The carbon nanotube-modified vinyl carbon fiber sizing agent composition according to any one of claims 1-6, characterized in that, The sizing agent composition is made from raw materials comprising the following weight percentages:

8. The carbon nanotube-modified vinyl carbon fiber sizing agent composition according to claim 7, characterized in that, The sizing agent composition is made from raw materials comprising the following weight percentages:

9. The carbon nanotube-modified vinyl carbon fiber sizing agent composition according to claim 7, characterized in that, The molecular weight of tetrahydrofuran polyether epoxy resin is 800-1200; And / or, the molecular weight of the bisphenol A polyether epoxy resin is 500 to 700; And / or, the unsaturated monocarboxylic acid is selected from acrylic acid and / or methacrylic acid; And / or, the isocyanate is selected from one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate; And / or, tetrahydrofuran polyether with a molecular weight of 200–800; And / or, the catalyst is selected from one or more of benzyltrimethylammonium chloride, triphenylphosphine, benzyltriethylammonium chloride, and benzyltriethylammonium bromide; And / or, the polymerization inhibitor is selected from one or more of hydroquinone, p-benzoquinone, tert-butylhydroquinone, 2,6-di-tert-butyl-4-methylphenol, methylhydroquinone, and p-hydroxyanisole; And / or, the carbon nanotubes are multi-walled carbon nanotubes with an outer diameter of 1–99 nm; And / or, the resistivity of deionized water is greater than 0.5 MΩ·cm; And / or, the emulsifier is an anionic emulsifier, selected from one or more of alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkyl sulfonates, alkylphenol polyoxyethylene ether sulfates, and arylalkylphenol polyoxyethylene ether sulfates.

10. A method for preparing a carbon nanotube-modified vinyl carbon fiber sizing agent composition according to any one of claims 1-9, characterized in that, Includes the following steps: S1, tetrahydrofuran polyether epoxy resin, bisphenol A polyether epoxy resin, polymerization inhibitor and unsaturated monocarboxylic acid are mixed, a catalyst is added at 90℃~120℃, and the reaction is continued until the acid value reaches 10±3mgKOH / g to obtain a vinyl resin prepolymer with unsaturated carbon-carbon double bonds at the end groups; the vinyl resin prepolymer with unsaturated carbon-carbon double bonds at the end groups includes tetrahydrofuran polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups and bisphenol A polyether vinyl resin with unsaturated carbon-carbon double bonds at the end groups. S2, at 40℃~50℃, tetrahydrofuran polyether is added dropwise to isocyanate and the reaction is continued until the hydroxyl value is 0mgKOH / g to obtain diisocyanate epoxy resin with isocyanate end group; S3, add diisocyanate epoxy resin with isocyanate end group to vinyl resin prepolymer at 55℃~60℃, the isocyanate of the diisocyanate epoxy resin reacts with the hydroxyl group obtained by ring opening of the epoxy group in the vinyl resin prepolymer, and continue the reaction until the isocyanate is 0, to obtain isocyanate modified vinyl resin prepolymer. S4, at 60-70℃, emulsifier, carbon nanotubes and water are added sequentially to isocyanate-modified vinyl resin prepolymer to obtain carbon nanotube-modified vinyl carbon fiber sizing agent. There is no order restriction for steps S1 and S2.

11. The preparation method according to claim 10, characterized in that, In step S1, the molar ratio of tetrahydrofuran polyether epoxy resin to bisphenol A polyether epoxy resin is 1:5 to 5:1; preferably, the molar ratio of tetrahydrofuran polyether epoxy resin to bisphenol A polyether epoxy resin is 1:1 to 1:

3. And / or, tetrahydrofuran polyether epoxy resin is formed by etherification and cyclization reaction of tetrahydrofuran polyether, epichlorohydrin and sodium hydroxide, with a molecular weight of 400 to 1600; And / or, the polyether groups in bisphenol A polyether epoxy resin are ether bonds introduced by polypropylene glycol or polyethylene glycol, with a molecular weight of 250 to 750; And / or, the unsaturated monocarboxylic acid is selected from acrylic acid and / or methacrylic acid; And / or, the polymerization inhibitor is selected from one or more of hydroquinone, p-benzoquinone, tert-butylhydroquinone, 2,6-di-tert-butyl-4-cresol, methylhydroquinone, and p-hydroxyanisole.

12. The preparation method according to claim 10 or 11, characterized in that, Step S1 is as follows: Tetrahydrofuran polyether epoxy resin, bisphenol A polyether epoxy resin, polymerization inhibitor and unsaturated monocarboxylic acid are mixed and stirred for 10 to 15 minutes. A catalyst is added at 90°C and the temperature is increased to 120°C at a rate of 6°C to 8°C / h. The reaction is continued until the acid value reaches 10±3 mgKOH / g, and a vinyl resin prepolymer with unsaturated carbon-carbon double bonds at the end is obtained.

13. The preparation method according to claim 10, characterized in that, The reaction temperature in step S2 is 45℃±2℃; And / or, the reaction temperature in step S3 is 60℃±2℃; And / or, the isocyanate is selected from one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate; And / or, the tetrahydrofuran polyether has a molecular weight of 200–800. And / or, the emulsifier is an anionic emulsifier, selected from one or more of alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkyl sulfonates, alkylphenol polyoxyethylene ether sulfates, and arylalkylphenol polyoxyethylene ether sulfates; And / or, the carbon nanotubes are multi-walled carbon nanotubes with an outer diameter of 1–99 nm; And / or, the resistivity of deionized water is greater than 0.5 MΩ·cm; And / or, the reaction temperature in step S4 is 65℃±2℃.

14. The preparation method according to claim 9 or 13, characterized in that, Step S4 is as follows: At 65℃±2℃, add emulsifier to isocyanate modified vinyl resin prepolymer, stir for 10-15 minutes, then add carbon nanotubes, continue stirring for 10-15 minutes, add 30% by mass of deionized water, continue stirring for 55-65 minutes, add the remaining deionized water, and continue stirring for 55-65 minutes to obtain carbon nanotube modified vinyl carbon fiber sizing agent.

15. The use of the carbon nanotube-modified vinyl carbon fiber sizing agent composition of claims 1-9 or the carbon nanotube-modified vinyl carbon fiber sizing agent composition obtained by the preparation method of claims 10-14 in the preparation of carbon fiber vinyl resin composite materials suitable for marine environments.

16. A carbon fiber vinyl resin composite material suitable for marine environments, characterized in that, From the inside out, it comprises carbon fiber, the carbon nanotube-modified vinyl carbon fiber sizing agent composition according to any one of claims 1-9, and a vinyl resin matrix.

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