A sizing agent, and a method for preparing and using the same

Abstract

The application relates to a sizing agent and a preparation method and use method thereof, and belongs to the technical field of sizing agents. A sizing agent is composed of main sizing material and water, wherein the main sizing material comprises grafted polypropylene, a plasticizer, an emulsifier and a lubricant, and the grafted monomer of the grafted polypropylene comprises a polar monomer. The sizing agent takes the grafted polypropylene with the polar monomer as the main body of the sizing agent, thus containing polar and non-polar parts, so as to have good compatibility with a thermoplastic matrix resin, and can tightly combine carbon fibers and the thermoplastic matrix resin together, so as to enhance the mechanical properties of a thermoplastic resin-based carbon fiber composite material. The introduction of the plasticizer and the lubricant enables the carbon fiber tows to have good adhesion, proper hardness and good fiber opening property, and can better meet the production requirements and subsequent application of the carbon fibers.

Description

Technical Field

[0001] This application relates to the field of sizing agents, and particularly to a sizing agent and its preparation and application methods. Background Technology

[0002] Thermoplastic resin-based carbon fiber composites possess advantages such as light weight, good mechanical properties, and strong deformation resistance. Furthermore, the thermoplastic resin matrix facilitates the recycling and reuse of carbon fibers, aligning with environmentally friendly material themes and attracting increasing attention. However, thermoplastic resins lack active crosslinking groups, and their chemical structures differ significantly from traditional sizing agents. Therefore, traditional epoxy resin-based carbon fiber sizing agents are not suitable for thermoplastic resin-based composites. To improve the compatibility of sizing agents with thermoplastic resin-based composites, extensive research has been conducted on novel sizing agents for different thermoplastic resins (such as polyamide (PA), polyethersulfone (PES), polyetheretherketone (PEEK), and polycarbonate (PC)).

[0003] Patent CN114717851A proposes a carbon fiber sizing agent composed of a polyurethane compound, a compound containing at least two terminal isocyanates in its molecule, a nonionic surfactant, and a solvent. The bonding between the carbon fiber and the resin is significantly improved after sizing. However, this sizing agent is a solvent-based sizing agent, and the organic solvent is highly volatile during the sizing process, which will have an adverse effect on production personnel and the production environment.

[0004] Patent CN114960206A discloses a high-temperature resistant, water-soluble thermoplastic sizing agent for carbon fibers, comprising thermoplastic resin, organic solvent, salinizing solvent, and water. This sizing agent has excellent heat resistance and can significantly improve the interfacial bonding performance between carbon fibers and polyarylether ketone resins. However, it contains high-boiling-point solvents and requires high-temperature drying, which increases energy consumption. Otherwise, the solvent will evaporate at the molding temperature of the composite material, forming pore defects and affecting the high mechanical properties of the composite material.

[0005] Patent CN109722894A proposes a carbon fiber sizing agent comprising polyolefin resin powder, sodium polyacrylate, fatty alcohol polyvinyl ether, and deionized water. The preparation process of this sizing agent is simple, safe, environmentally friendly, and has low overall cost. However, this sizing agent requires the addition of a large number of stabilizing additives, which will weaken the mechanical properties of the composite material. Summary of the Invention

[0006] To address the shortcomings of existing technologies, one of the objectives of this application is to provide a sizing agent for bonding carbon fibers and thermoplastic matrix resins, thereby balancing the adhesiveness, safety, and stability of the sizing agent to a certain extent.

[0007] To achieve one of the above objectives, the technical solution adopted in this application is as follows:

[0008] A sizing agent, composed of a main sizing agent and water, wherein the main sizing agent includes grafted polypropylene, plasticizer, emulsifier and lubricant, wherein, by mass percentage, grafted polypropylene accounts for 50-90% of the main sizing agent, plasticizer accounts for 5-40% of the main sizing agent, emulsifier accounts for 0.05-3% of the main sizing agent, and lubricant accounts for 2-30% of the main sizing agent; the grafting monomers of the grafted polypropylene include polar monomers.

[0009] In this application, polar monomer-grafted polypropylene is used as the main sizing agent. On the one hand, the grafted polar groups interact with the oxygen-containing groups such as hydroxyl and carboxyl groups on the carbon fiber surface, forming a firmly bonded surface layer. On the other hand, the polypropylene polymer grafted with polar monomers contains both polar and non-polar portions (polypropylene), thus exhibiting good compatibility with thermoplastic matrix resins such as PA, PU, ​​PP, and ABS. This allows for the tight bonding of carbon fibers with the thermoplastic matrix resin, thereby enhancing the mechanical properties of the thermoplastic resin-based carbon fiber composite material. The introduction of plasticizers and lubricants ensures that the carbon fiber tow possesses good adhesion, appropriate hardness, and good fiber-opening ability, effectively meeting production requirements and subsequent applications of carbon fibers.

[0010] In some embodiments of this application, the main slurry comprises, by mass percentage, 60-86% grafted polypropylene, 10-28% plasticizer, 0.1-1.7% emulsifier, and 6-10% lubricant.

[0011] In some embodiments of this application, the grafted polypropylene includes one or more of maleic anhydride-grafted polypropylene, dibutyl maleic anhydride-grafted polypropylene, acrylic acid-grafted polypropylene, methyl methacrylate-grafted polypropylene, butyl acrylate-grafted polypropylene, acrylamide-grafted polypropylene, and vinyl acetate-grafted polypropylene. All of the above-mentioned grafted polypropylenes comprise both polar (grafting monomer) and non-polar (polypropylene) components. Therefore, the polypropylene polymer grafted with the polar monomer has good compatibility with the thermoplastic matrix resin, enabling it to tightly bond carbon fibers to the thermoplastic matrix resin, thereby enhancing the mechanical properties of the thermoplastic resin-based carbon fiber composite material.

[0012] In some embodiments of this application, the grafted polypropylene is maleic anhydride-grafted polypropylene and maleic anhydride dibutyl ester-grafted polypropylene.

[0013] In some embodiments of this application, the grafted polypropylene is maleic anhydride-grafted polypropylene.

[0014] In some embodiments of this application, the grafting rate of the grafted polypropylene is 0.5-2.0%. Grafted products within this range have high compatibility with thermoplastic matrix resins and are readily available; therefore, the grafting rate of 0.5-2.0% in this application is a suitable range.

[0015] In some embodiments of this application, the weight-average molecular weight of the grafted polypropylene is 10,000-40,000, preferably 15,000-25,000.

[0016] In some embodiments of this application, the plasticizer includes bisphenol A polyoxyethylene ether, with the molecular formula C 15 H 16 O2(C2H4O) n n = 2-3 or bisphenol A polyoxypropylene ether, with the molecular formula C 15 H 16 O2(C3H6O) n n = 2-3. The two plasticizers mentioned above can improve the flexibility of the coating film. By controlling their addition amount, appropriate hardness can be imparted to the sized carbon fiber, which is beneficial to the production and subsequent application of carbon fiber.

[0017] In some embodiments of this application, the lubricant includes one or more of polyethylene glycol monolaurate, polyethylene glycol stearate, polyethylene glycol monooctanoate, polyethylene glycol disilicate, polyethylene glycol fatty acid ester, polyethylene glycol monotetradecanoate, and polyethylene glycol dioctanoate. These lubricants can reduce surface friction of the carbon fibers and impart good fiber-opening properties in the sizing agent, allowing the composite matrix resin to fully impregnate the carbon fibers.

[0018] In some embodiments of this application, the lubricant is polyethylene glycol monolaurate. Polyethylene glycol monolaurate can effectively improve the fiber opening properties of carbon fibers.

[0019] In some embodiments of this application, the emulsifier includes one or more of dodecyltrimethylammonium chloride, polyvinyl alcohol, alkylphenol polyoxyethylene ether, sorbitan monostearate polyoxyethylene ether, fatty acid polyoxyethylene ether, and castor oil polyoxyethylene ether.

[0020] In some embodiments of this application, the emulsifier is dodecyltrimethylammonium chloride.

[0021] In some embodiments of this application, the emulsifiers are dodecylmethylammonium chloride and polyvinyl alcohol. The combination of these two emulsifiers provides better emulsification and results in a more stable emulsion; therefore, a combination of the two is chosen.

[0022] In some embodiments of this application, the mass ratio of dodecylmethylammonium chloride to polyvinyl alcohol is (1-2):1. A second objective of this application is to provide a method for preparing a sizing agent.

[0023] To achieve the second objective mentioned above, the technical solution adopted in this application is as follows:

[0024] A method for preparing a sizing agent, comprising:

[0025] S1. The grafted polypropylene is dissolved by heating with an organic solvent to obtain a polymer solution;

[0026] S2. Add emulsifier, plasticizer and lubricant to the polymer solution in step S1, and add water under stirring to emulsify and obtain emulsion;

[0027] S3. The emulsion in step S2 is subjected to vacuum evaporation to remove the organic solvent, thereby obtaining the sizing agent emulsion.

[0028] This preparation method uses an emulsion / solvent evaporation method to prepare sizing agents. The operation steps are simple, safe and environmentally friendly. The prepared sizing agent does not contain organic solvents and the emulsion has strong stability.

[0029] In some embodiments of this application, the organic solvent is toluene or xylene. Grafted polypropylene dissolves well in these two organic solvents.

[0030] In some embodiments of this application, the mass ratio of organic solvent to grafted polypropylene is (4-9):1. Within this range, the grafted polypropylene has high solubility, which facilitates the preparation of sizing agent emulsions.

[0031] In some embodiments of this application, step S2 includes: adding emulsifier, plasticizer and lubricant to the polymer solution in step S1, stirring at 200-600 r / min for 5-10 min, then controlling the rotation speed to 4000-10000 r / min, and adding water for emulsification.

[0032] In some embodiments of this application, the mass ratio of water to organic solvent is (1-2):1. Within this range, the stability of the emulsion can be improved, and the emulsion can be prevented from separating or coagulating.

[0033] In some embodiments of this application, step S3, the reduced pressure evaporation treatment, includes: stirring at 500-1000 r / min, with a pressure of -0.1-0 MPa, for 2-4 hours. The purpose of the reduced pressure evaporation treatment is to remove organic solvents from the sizing agent.

[0034] The third objective of this application is to provide a method for using a sizing agent.

[0035] To achieve the third objective mentioned above, the technical solution adopted in this application is as follows:

[0036] A method for using a sizing agent involves diluting the sizing agent to a concentration of 0.1-3% and applying the sizing agent to the surface of carbon fiber using an impregnation method. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0038] The following is a detailed description of a sizing agent according to an embodiment of this application, as well as its preparation and application methods.

[0039] A sizing agent is composed of a main sizing agent and water. The main sizing agent includes grafted polypropylene, plasticizer, emulsifier, and lubricant. By mass percentage, the grafted polypropylene accounts for 50-90% of the main sizing agent, the plasticizer accounts for 5-40% of the main sizing agent, the emulsifier accounts for 0.05-3% of the main sizing agent, and the lubricant accounts for 2-30% of the main sizing agent. The grafting monomers of the grafted polypropylene include polar monomers.

[0040] In this application, polar monomer-grafted polypropylene is used as the main sizing agent. On the one hand, the grafted polar groups interact with the oxygen-containing groups such as hydroxyl and carboxyl groups on the carbon fiber surface, forming a firmly bonded surface layer. On the other hand, the polypropylene polymer grafted with polar monomers contains both polar and non-polar portions (polypropylene), thus exhibiting good compatibility with thermoplastic matrix resins such as PA, PU, ​​PP, and ABS. This allows for a tight bond between the carbon fiber and the thermoplastic matrix resin, thereby enhancing the mechanical properties of the thermoplastic resin-based carbon fiber composite material. The introduction of plasticizers and lubricants ensures that the carbon fiber tow possesses good adhesion, appropriate hardness, and good fiber-opening ability, effectively meeting production requirements and subsequent applications of the carbon fiber.

[0041] In some embodiments, a sizing agent for bonding carbon fibers and a thermoplastic matrix resin is composed of a main sizing agent and water. The main sizing agent includes grafted polypropylene, a plasticizer, an emulsifier, and a lubricant, wherein, by mass percentage, the grafted polypropylene comprises 60-86% of the main sizing agent, the plasticizer comprises 10-28% of the main sizing agent, the emulsifier comprises 0.1-1.7% of the main sizing agent, and the lubricant comprises 6-10% of the main sizing agent.

[0042] In some embodiments, the grafted polypropylene includes one or more of maleic anhydride-grafted polypropylene, dibutyl maleic anhydride-grafted polypropylene, acrylic acid-grafted polypropylene, methyl methacrylate-grafted polypropylene, butyl acrylate-grafted polypropylene, acrylamide-grafted polypropylene, and vinyl acetate-grafted polypropylene. All of the above-mentioned grafted polypropylenes include both polar (grafting monomer) and non-polar (polypropylene) components. Therefore, the polypropylene polymer grafted with the polar monomer has good compatibility with the thermoplastic matrix resin, enabling it to tightly bond carbon fibers to the thermoplastic matrix resin, thereby enhancing the mechanical properties of the thermoplastic resin-based carbon fiber composite material.

[0043] In some embodiments, the grafted polypropylene is maleic anhydride-grafted polypropylene and maleic anhydride dibutyl ester-grafted polypropylene.

[0044] In some embodiments, the grafted polypropylene is maleic anhydride-grafted polypropylene.

[0045] In some embodiments, the grafting rate of the grafted polypropylene is 0.5-2.0%.

[0046] Grafting rate refers to the ratio of the amount of monomer or polymer grafted into the polymer backbone to the initial amount of polymer to be grafted. Grafted polypropylene with a grafting rate of 0.5-2.0% exhibits better adhesion to carbon fibers and imparts good wettability to the carbon fibers, enabling them to better contact the matrix resin and form a robust sizing layer. Therefore, the grafting rate of 1.0-2.0% in this application is a suitable range. Products within this grafting rate range have high compatibility with thermoplastic matrix resins and are relatively easy to obtain.

[0047] In some embodiments, the weight-average molecular weight of the grafted polypropylene is 10,000-40,000. This molecular weight range is advantageous for both emulsion preparation and film formation on the carbon fiber surface. Excessively high or low weight-average molecular weight of the grafted polypropylene will affect the fiber filament density and interlaminar shear strength after sizing.

[0048] In some embodiments, the weight-average molecular weight of the grafted polypropylene is 15,000-25,000.

[0049] In some embodiments, the plasticizer includes bisphenol A polyoxyethylene ether with the molecular formula C 15 H 16 O2(C2H4O) n n = 2-3 or bisphenol A polyoxypropylene ether, with the molecular formula C 15 H 16 O2(C3H6O) n , n = 2 - 3.

[0050] Bisphenol A polyoxyethylene ether and bisphenol A polyoxypropylene ether have good plasticizing effects, which can significantly improve the flexibility and ductility of the coating film. They can effectively reduce the hardness of sized carbon fibers, so as to facilitate carbon fiber production and subsequent applications. In addition, bisphenol A polyoxyethylene ether and bisphenol A polyoxypropylene ether are non-toxic, odorless and tasteless, and are relatively safe for human health and the environment, meeting environmental protection requirements.

[0051] In some embodiments, the lubricant includes one or more of polyethylene glycol monolaurate, polyethylene glycol stearate, polyethylene glycol monooctanoate, polyethylene glycol disilicate, polyethylene glycol fatty acid ester, polyethylene glycol monotetradecanoate, and polyethylene glycol dioctanoate.

[0052] The aforementioned lubricant can reduce surface friction of carbon fibers and impart good fiber opening properties in the sizing agent, so that the composite matrix resin can fully impregnate the carbon fibers.

[0053] In some embodiments, the lubricant is polyethylene glycol monolaurate.

[0054] Polyethylene glycol monolaurate possesses excellent lubricating properties, effectively reducing friction between carbon fibers and between carbon fibers and guide rollers. It also significantly improves the fiber-opening properties of carbon fibers and enhances the wetting of the carbon fibers by the matrix resin. Furthermore, polyethylene glycol monolaurate exhibits good thermal stability and compatibility, preventing phase separation or uneven dispersion, thus contributing to the maintenance of material uniformity and stability.

[0055] In some embodiments, the emulsifier includes one or more of dodecyltrimethylammonium chloride, polyvinyl alcohol, alkylphenol polyoxyethylene ether, sorbitan monostearate polyoxyethylene ether, fatty acid polyoxyethylene ether, and castor oil polyoxyethylene ether.

[0056] In some embodiments, the emulsifier is polyvinyl alcohol.

[0057] In some embodiments, the emulsifier is dodecylmethylammonium chloride and polyvinyl alcohol. Dodecylmethylammonium chloride is a cationic surfactant, while polyvinyl alcohol is a nonionic surfactant. The two have good compatibility, and their combination can provide excellent emulsification, effectively dispersing insoluble components into the continuous phase to form a stable emulsion.

[0058] In some embodiments, the mass ratio of dodecylmethylammonium chloride to polyvinyl alcohol is (1-2):1.

[0059] A method for preparing a sizing agent, comprising:

[0060] S1. The grafted polypropylene is dissolved by heating with an organic solvent to obtain a polymer solution;

[0061] S2. Add emulsifier, plasticizer and lubricant to the polymer solution in step S1, and add deionized water under stirring to emulsify and obtain emulsion;

[0062] S3. The emulsion in step S2 is subjected to vacuum evaporation to remove the organic solvent, thereby obtaining the sizing agent emulsion.

[0063] This preparation method uses an emulsion / solvent evaporation method to prepare sizing agents. The operation steps are simple, safe and environmentally friendly. The prepared sizing agent does not contain organic solvents and the emulsion has strong stability.

[0064] In some embodiments, the organic solvent is toluene or xylene. Grafted polypropylene is well soluble in both of these solvents.

[0065] In some embodiments, the mass ratio of organic solvent to grafted polypropylene is (4-9):1. As examples, the mass ratio of organic solvent to grafted polypropylene includes, but is not limited to, 4:1, 5:1, 6:1, 7:1, 8:1, and 9:1. The use of organic solvent can promote the dissolution of grafted polypropylene, facilitating its emulsification. Higher amounts of organic solvent improve the dissolution effect of polypropylene but hinder the removal of organic solvent from the sizing agent. Therefore, a mass ratio of organic solvent to grafted polypropylene of (4-9):1 is suitable in this application, as this range provides better dissolution of grafted polypropylene and facilitates the preparation of the sizing agent emulsion.

[0066] In some embodiments, step S2 includes: adding emulsifier, plasticizer, and lubricant to the polymer solution in step S1, stirring at 200-600 r / min for 5-10 min, then controlling the stirring speed at 4000-10000 r / min, and adding water for emulsification. First, the materials are mixed evenly under low-speed stirring conditions, and then emulsification is carried out under high-speed stirring conditions. Increasing the stirring speed tends to reduce the emulsion particle size, which is beneficial to emulsion stability.

[0067] In some embodiments, the mass ratio of water to organic solvent is (1-2):1. For example, the mass ratio of water to organic solvent includes, but is not limited to, 1:1, 1.5:1, and 2:1. Water is a major component of the sizing agent; an appropriate amount of water can promote the formation of a stable emulsion system by the emulsifier, resulting in better emulsification of the sizing agent. Too much or too little water may affect the emulsification performance of the emulsifier. Therefore, in this application, the mass ratio of water to organic solvent is (1-2):1. Within this range, the stability of the emulsion can be improved, preventing emulsion separation or coagulation.

[0068] In some embodiments, the emulsifier is first dissolved in water. Some emulsifiers are solid particles and need to be dissolved in deionized water first.

[0069] In some embodiments, step S3, the reduced pressure evaporation treatment includes: stirring at 500-1000 r / min, with a pressure of -0.1-0 MPa, for 2-4 hours. The reduced pressure evaporation treatment reduces the system pressure, thereby promoting the evaporation of organic solvents from the sizing agent at a relatively low temperature. The purpose of this process is to remove organic solvents from the sizing agent, ensuring a safe and environmentally friendly sizing process.

[0070] One method of using the above-mentioned sizing agent involves diluting the sizing agent to a concentration of 0.1-3% and applying the sizing agent to the surface of carbon fiber using an impregnation method.

[0071] If the concentration of the sizing agent is too low, the sizing agent content of the carbon fiber will be low, resulting in poor fiber bundle structure and excessive fuzz, which will not meet production requirements. If the concentration of the sizing agent is too high, the carbon fiber will be too stiff, with poor fiber opening ability, which is not conducive to subsequent applications. Therefore, the appropriate concentration of the sizing agent used in this application is 0.1-3%.

[0072] In some embodiments, the concentration of the sizing agent is 0.5-1.5% for sizing carbon fibers.

[0073] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0074] Example 1

[0075] (1) Add 69g of maleic anhydride-grafted polypropylene (grafting rate of 1.2% and weight average molecular weight of 20,000) into a closed reaction vessel and dissolve it in toluene at 90°C. The mass ratio of maleic anhydride-grafted polypropylene to toluene is 1:5, so that the maleic anhydride-grafted polypropylene is completely dissolved.

[0076] (2) Dissolve 0.5g of polyvinyl alcohol in deionized water, with a mass ratio of deionized water to toluene of 1:1; add 0.5g of dodecyltrimethylammonium chloride, 20g of bisphenol A polyoxyethylene ether and 10g of polyethylene glycol monolaurate to the maleic anhydride-grafted polypropylene solution in step (1) and mix evenly. Under stirring conditions of 4000-10000r / min, gradually add deionized water containing polyvinyl alcohol to the aforementioned maleic anhydride-grafted polypropylene solution for emulsification. After the deionized water containing polyvinyl alcohol is added, control the speed to 800r / min and stir for 5min to obtain an emulsion.

[0077] (3) The emulsion obtained in step (2) is stirred and evaporated for 3 hours under a pressure of -0.1 MPa, and then the emulsion is diluted to a concentration of 1% to obtain the sizing agent emulsion.

[0078] Example 2

[0079] This embodiment is basically the same as embodiment 1, except that in step (2), 20g of bisphenol A polyoxyethylene ether is replaced with 20g of bisphenol A polyoxypropylene ether.

[0080] Example 3

[0081] (1) Add 78g of maleic anhydride dibutyl ester grafted polypropylene (grafting rate of 1.5%, weight average molecular weight of 20000) into a closed reaction vessel and dissolve it in toluene at 90℃. The mass ratio of maleic anhydride dibutyl ester grafted polypropylene to toluene is 1:5, so that the maleic anhydride dibutyl ester grafted polypropylene is completely dissolved.

[0082] (2) Dissolve 2g of polyvinyl alcohol in deionized water and set aside; add 10g of bisphenol A polyoxyethylene ether and 10g of polyethylene glycol monolaurate to the maleic anhydride-grafted polypropylene solution in step (1) and mix evenly. Under stirring conditions of 4000-10000r / min, gradually add the deionized water containing polyvinyl alcohol to emulsify. The mass ratio of deionized water to xylene is 2:1. After the deionized water containing polyvinyl alcohol is added, control the speed to 800r / min and stir for 5min to obtain the emulsion.

[0083] (3) The emulsion obtained in step (2) is stirred and evaporated for 4 hours under a pressure of -0.1 MPa, and then the emulsion is diluted to a concentration of 0.8% to obtain the sizing agent emulsion.

[0084] Example 4

[0085] (1) Add 60g of maleic anhydride-grafted polypropylene (grafting rate of 1.2% and weight average molecular weight of 20,000) into a closed reaction vessel and dissolve it in xylene at 100℃. The mass ratio of maleic anhydride-grafted polypropylene to xylene is 1:7, so that the maleic anhydride-grafted polypropylene is completely dissolved.

[0086] (2) Add 1g dodecyltrimethylammonium chloride, 1g sorbitan monostearate polyoxyethylene ether, 28g bisphenol A polyoxyethylene ether and 10g polyethylene glycol monolaurate to the maleic anhydride grafted polypropylene solution in step (1) and mix evenly. Set aside for later use. Under stirring conditions of 4000-10000r / min, gradually add deionized water to emulsify. The mass ratio of deionized water to xylene is 1:1. After the deionized water is added, control the speed to 800r / min and stir for 5min to obtain the emulsion.

[0087] (3) The emulsion obtained in step (2) is stirred and evaporated for 3 hours under a pressure of -0.1 MPa, and then the emulsion is diluted to a concentration of 1.5% to obtain the sizing agent emulsion.

[0088] Example 5

[0089] (1) Add 70g of maleic anhydride-grafted polypropylene (grafting rate of 1.2% and weight average molecular weight of 20,000) into a closed reaction vessel and dissolve it in toluene at 90°C. The mass ratio of maleic anhydride-grafted polypropylene to toluene is 1:5, so that the maleic anhydride-grafted polypropylene is completely dissolved.

[0090] (2) Add 1g dodecyltrimethylammonium chloride, 1g sorbitan monostearate polyoxyethylene ether, 15g bisphenol A polyoxyethylene ether and 13g polyethylene glycol monolaurate to the maleic anhydride grafted polypropylene solution in step (1) and mix evenly. Set aside for later use. Under stirring conditions of 4000-10000r / min, gradually add deionized water to emulsify. The mass ratio of deionized water to toluene is 1:1. After the deionized water is added, control the speed to 800r / min and stir for 5min to obtain the emulsion.

[0091] (3) The emulsion obtained in step (2) is stirred and evaporated for 3 hours under a pressure of -0.1 MPa, and then the emulsion is diluted to a concentration of 1% to obtain the sizing agent emulsion.

[0092] Example 6

[0093] (1) Add 80g of maleic anhydride-grafted polypropylene (grafting rate of 1.2% and weight average molecular weight of 20,000) into a closed reaction vessel and dissolve it in toluene at 90°C. The mass ratio of maleic anhydride-grafted polypropylene to toluene is 1:5, so that the maleic anhydride-grafted polypropylene is completely dissolved.

[0094] (2) Add 1.5g dodecyltrimethylammonium chloride, 1.5g sorbitan monostearate polyoxyethylene ether, 10g bisphenol A polyoxypropylene ether and 7g polyethylene glycol monolaurate to maleic anhydride grafted polypropylene solution and mix evenly. Set aside for later use. Under stirring conditions of 4000-10000r / min, gradually add deionized water to emulsify. The mass ratio of deionized water to toluene is 1:1. After the deionized water is added, control the speed to 800r / min and stir for 5min to obtain emulsion.

[0095] (3) The emulsion obtained in step (2) is stirred and evaporated for 4 hours under a pressure of -0.1 MPa, and then the emulsion is diluted to a concentration of 1% to obtain the sizing agent emulsion.

[0096] Example 7

[0097] This embodiment is basically the same as embodiment 1, except that polyvinyl alcohol is not added in step (2).

[0098] Step (2) is as follows:

[0099] Add 1.0g dodecyltrimethylammonium chloride, 20g bisphenol A polyoxyethylene ether and 10g polyethylene glycol monolaurate to the maleic anhydride-grafted polypropylene solution in step (1) and mix evenly. Under stirring conditions of 4000-10000r / min, gradually add deionized water containing polyvinyl alcohol to the aforementioned maleic anhydride-grafted polypropylene solution for emulsification. After the deionized water containing polyvinyl alcohol is added, control the speed to 800r / min and stir for 5min to obtain an emulsion.

[0100] Example 8

[0101] This embodiment is basically the same as that of embodiment 1, except that dodecyltrimethylammonium chloride is not added in step (2).

[0102] Step (2) is as follows:

[0103] Dissolve 1.0g of polyvinyl alcohol in deionized water, with a mass ratio of deionized water to toluene of 1:1; add 20g of bisphenol A polyoxyethylene ether and 10g of polyethylene glycol monolaurate to the maleic anhydride-grafted polypropylene solution in step (1) and mix evenly. Under stirring conditions of 4000-10000r / min, gradually add deionized water containing polyvinyl alcohol to the aforementioned maleic anhydride-grafted polypropylene solution for emulsification. After the deionized water containing polyvinyl alcohol is added, control the stirring speed at 800r / min and stir for 5min to obtain an emulsion.

[0104] Example 9

[0105] This embodiment is basically the same as that of embodiment 1, except that in step (2), the emulsifier is a compound of dodecyltrimethylammonium chloride and sorbitan monostearate polyoxyethylene ether.

[0106] Step (2) is as follows:

[0107] Add 0.5g dodecyltrimethylammonium chloride, 0.5g sorbitan monostearate polyoxyethylene ether, 20g bisphenol A polyoxyethylene ether, and 10g polyethylene glycol monolaurate to the maleic anhydride-grafted polypropylene solution in step (1) and mix well. Under stirring conditions of 4000-10000r / min, gradually add deionized water containing polyvinyl alcohol to the aforementioned maleic anhydride-grafted polypropylene solution for emulsification. After the deionized water containing polyvinyl alcohol is added, control the stirring speed at 800r / min and stir for 5min to obtain an emulsion.

[0108] Example 10

[0109] This embodiment is basically the same as that of embodiment 1, except that in step (2), the emulsifier is a compound of polyvinyl alcohol and sorbitan monostearate polyoxyethylene ether.

[0110] Step (2) is as follows:

[0111] Dissolve 0.5g of polyvinyl alcohol in deionized water, with a mass ratio of deionized water to toluene of 1:1; add 0.5g of sorbitan monostearate polyoxyethylene ether, 20g of bisphenol A polyoxyethylene ether, and 10g of polyethylene glycol monolaurate to the maleic anhydride-grafted polypropylene solution in step (1) and mix evenly. Under stirring conditions of 4000-10000r / min, gradually add deionized water containing polyvinyl alcohol to the aforementioned maleic anhydride-grafted polypropylene solution for emulsification. After the deionized water containing polyvinyl alcohol is added, control the stirring speed at 800r / min and stir for 5min to obtain an emulsion.

[0112] Example 11

[0113] This embodiment is basically the same as Embodiment 1, except that the grafting rate of maleic anhydride-grafted polypropylene is 0.3%.

[0114] Example 12

[0115] This embodiment is basically the same as that in Embodiment 1, except that the weight-average molecular weight of the maleic anhydride-grafted polypropylene is 120,000.

[0116] Example 13

[0117] This embodiment is basically the same as that in Embodiment 1, except that the weight-average molecular weight of the maleic anhydride-grafted polypropylene is 9000.

[0118] Comparative Example 1

[0119] This embodiment is basically the same as that of embodiment 1, except that in step (3), the sizing agent is diluted to a concentration of 0.5% to obtain a sizing agent emulsion.

[0120] Comparative Example 2

[0121] This embodiment is basically the same as that of embodiment 1, except that in step (3), the sizing agent is diluted to a concentration of 3% to obtain a sizing agent emulsion.

[0122] Test case

[0123] In this experiment, the sizing agents prepared in Examples 1-13 and Comparative Examples 1-2 were applied to T700×12K carbon fiber bundles using the impregnation method. The bundles were then dried at 180°C. The emulsion properties of the sizing agent, the apparent properties of the sized carbon fibers, and the interlaminar shear strength of the sized carbon fibers / ABS resin were then tested.

[0124] Among them, (1) the particle size of the above sizing agent emulsion was tested using a laser particle size analyzer, the analyzer model being Microtrac S3500. The emulsion sample was automatically diluted to a suitable concentration for testing; (2) the above sizing agent emulsion was left to stand for 3 months to observe the stability of the emulsion. Emulsion without stratification and without sediment at the bottom was considered to have excellent stability, emulsion without stratification but with sediment at the bottom was considered to have good stability, and emulsion with stratification and sediment at the bottom was considered to have poor stability; (3) the filament weight, hardness, and fiber opening rate of the sized carbon fiber were determined according to the method of filament weight, hardness, and fiber opening rate in "Carbon Fiber and Graphite Fiber"; (5) the interlaminar shear strength was determined according to JC / T773—2010, and ABS resin was selected as the resin. The performance of the sizing agent emulsion, the filament weight, hardness, fiber opening rate of the sized carbon fiber, and the interlaminar shear strength test data of the sized carbon fiber / ABS resin are listed in Table 1.

[0125] Table 1

[0126]

[0127] As can be seen from Table 1, the sized carbon fibers prepared in the embodiments of this application not only have good adhesion, but also suitable hardness and good fiber opening properties. This sizing agent has strong stability and can be used in thermoplastic resin-based composite materials, enhancing the interfacial bonding strength between the thermoplastic resin and the carbon fiber.

[0128] Comparing Examples 1 and 7-10, it is evident that the sizing agent obtained by compounding dodecylmethylammonium chloride and polyvinyl alcohol as emulsifier exhibits the best stability. Comparing Examples 1 and Comparative Example 1, it is evident that a low grafting rate of maleic anhydride-grafted polypropylene significantly reduces the interlaminar shear strength of the fibers, thereby affecting the bonding between the carbon fibers and the thermoplastic resin after sizing. Comparing Examples 1, 11, and 12, it is evident that both excessively high and low weight-average molecular weights of the grafted polypropylene affect the fiber filament quantity and interlaminar shear strength after sizing. Comparing Examples 1, 11, and 2, it is evident that a low sizing agent emulsion concentration results in more carbon fiber filaments and lower interlaminar shear strength; a high sizing agent emulsion concentration results in greater carbon fiber stiffness, which is detrimental to matrix resin wetting and also leads to lower interlaminar shear strength.

[0129] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A sizing agent, characterized in that, Composed of a main slurry and water, the main slurry includes grafted polypropylene, plasticizer, emulsifier, and lubricant, with the following mass percentages: grafted polypropylene 50-90% of the main slurry, plasticizer 5-40% of the main slurry, emulsifier 0.05-3% of the main slurry, and lubricant 2-30% of the main slurry. The grafting monomers of the grafted polypropylene include polar monomers. The plasticizer includes bisphenol A polyoxyethylene ether with the molecular formula n=2-3. The emulsifier includes dodecyltrimethylammonium chloride and polyvinyl alcohol. The grafted polypropylene includes one or more of maleic anhydride grafted polypropylene, dibutyl maleic anhydride grafted polypropylene, acrylic acid grafted polypropylene, methyl methacrylate grafted polypropylene, butyl acrylate grafted polypropylene, acrylamide grafted polypropylene, and vinyl acetate grafted polypropylene.

2. The sizing agent according to claim 1, characterized in that, By mass percentage, the main component of the slurry is 60-86% grafted polypropylene, the main component of the slurry is 10-28% plasticizer, the main component of the slurry is 0.1-1.7% emulsifier, and the main component of the slurry is 6-10%.

3. The sizing agent according to claim 1, characterized in that, The grafted polypropylene is maleic anhydride-grafted polypropylene and maleic anhydride dibutyl ester-grafted polypropylene.

4. The sizing agent according to claim 1, characterized in that, The grafted polypropylene is maleic anhydride-grafted polypropylene.

5. The sizing agent according to any one of claims 1-4, characterized in that, The grafting rate of the grafted polypropylene is 0.5-2.0%.

6. The sizing agent according to claim 5, characterized in that, The weight-average molecular weight of the grafted polypropylene is 10,000-40,000.

7. The sizing agent according to claim 6, characterized in that, The grafted polypropylene has a weight-average molecular weight of 15,000-25,000.

8. The sizing agent according to any one of claims 1-4, characterized in that, The lubricant includes one or more of polyethylene glycol monolaurate, polyethylene glycol stearate, polyethylene glycol monooctanoate, polyethylene glycol disilicate, polyethylene glycol fatty acid ester, polyethylene glycol monotetradecanoate, and polyethylene glycol dioctanoate.

9. The sizing agent according to claim 8, characterized in that, The lubricant is polyethylene glycol monolaurate.

10. The sizing agent according to any one of claims 1-4, characterized in that... The mass ratio of the dodecyltrimethylammonium chloride to the polyvinyl alcohol is (1-2):

1.

11. A method for preparing a sizing agent as described in any one of claims 1-10, characterized in that, include: S1. Dissolve the grafted polypropylene in an organic solvent to obtain a polymer solution; S2. The emulsifier, the plasticizer and the lubricant are added to the polymer solution in step S1, and water is added under stirring to emulsify, thereby obtaining an emulsion; S3. The emulsion from step S2 is subjected to vacuum evaporation to remove the organic solvent, thereby obtaining the sizing agent.

12. The preparation method according to claim 11, characterized in that, The organic solvent is toluene or xylene.

13. The preparation method according to claim 12, characterized in that, The mass ratio of the organic solvent to the grafted polypropylene is (4-9):

1.

14. The preparation method according to any one of claims 11 to 13, characterized in that, Step S2 includes: adding emulsifier, plasticizer and lubricant to the polymer solution in step S1, stirring at 200-600 r / min for 5-10 min, then controlling the rotation speed at 4000-10000 r / min, and adding water for emulsification.

15. The preparation method according to claim 14, characterized in that, The mass ratio of water to organic solvent is (1-2):

1.

16. The preparation method according to any one of claims 11 to 13, characterized in that, In step S3, the reduced pressure volatilization treatment includes: stirring at 500-1000 r / min, with a pressure of -0.1-0 MPa, for 2-4 hours.

17. A method of using a sizing agent as described in any one of claims 1-10, characterized in that, The sizing agent is diluted to a concentration of 0.1-3%, and then applied to the carbon fiber surface using an impregnation method.

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