Sizing agent without organic solvent and preparation method thereof

Abstract

The invention provides an organic solvent-free sizing agent and a preparation method thereof, and the organic solvent-free sizing agent comprises the following components in parts by weight: 40-50 parts of dimer acid modified epoxy resin, 5-8 parts of polyethylene glycol modified epoxy resin, 0.01-0.3 part of a leveling agent and the balance of water, wherein in the dimer acid modified epoxy resin, the epoxy equivalent is 450 to 550 g / eq; in the polyethylene glycol modified epoxy resin, the molar ratio of polyethylene glycol to epoxy resin is (1-2): (1-2). According to the sizing agent, the bio-based modified epoxy resin is used as a main component of the sizing agent, and auxiliary components such as the flatting agent are added, so that the sizing agent has excellent flexibility and adhesiveness, a layer of uniform and compact film can be formed on the surface of the carbon fiber, and the interface bonding strength between the carbon fiber and a matrix material is enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of carbon fiber composite materials, and in particular to a sizing agent free of organic solvents and a preparation method thereof. Background Art

[0002] In the preparation process of carbon fiber composite materials, the use of sizing agent is crucial to the interfacial bonding performance between carbon fiber and matrix material. Waterborne epoxy emulsion is widely used as sizing agent in the preparation process of carbon fiber composite materials. However, although waterborne epoxy emulsion has shown its obvious advantages as a sizing agent, it still faces some problems in practical application.

[0003] First, the wettability of the traditional water-based epoxy emulsion sizing agent on the surface of carbon fiber is still insufficient, which affects the interfacial bonding strength between the carbon fiber and the matrix material. Patent CN118087258A discloses a sizing agent and a preparation method thereof and carbon fiber. The patent discloses a sizing agent, including a matrix, an additive, a smoothing agent and an emulsifier. The matrix includes a variety of modified epoxy resins and amide compounds, the additives include a variety of amine compounds, and the smoothing agent and emulsifier also contain a variety of compounds to improve the interfacial bonding strength between the carbon fiber and the resin matrix. Although the sizing agent of the patent is designed to improve the interfacial bonding strength, although the addition of amide compounds increases the flexibility of the sizing agent, the compatibility with carbon fiber may decrease, and there may also be problems of high cost or complicated preparation process, which may limit its wide application in industrial production. In addition, patent CN202110961619.9 discloses a sizing agent for carbon fiber, a preparation method thereof and a composite material. The patent discloses a sizing agent, including a hyperbranched prepolymer, an emulsifier, a dispersant and water, wherein the hyperbranched prepolymer is prepared by a specific chemical reaction to improve the interface performance between carbon fiber and resin. The sizing agent of the patent is optimized for the interface performance, but the synthesis of the hyperbranched prepolymer may involve complex chemical reactions and precise control, which may increase the difficulty and cost of production.

[0004] Secondly, in products where water-based epoxy emulsion is used as a sizing agent, due to the high viscosity of bisphenol A epoxy resin itself, at least 7% of organic solvent is required for processing, which is still a problem that needs to be solved for environmental protection. Moreover, during the construction stage, the use of water-based epoxy emulsion containing organic solvents as a sizing agent not only increases the construction cost, but also may pose a potential threat to the health of construction workers. Therefore, finding more environmentally friendly and low-cost alternatives has become a research hotspot in the industry. Summary of the invention

[0005] In view of the defects in the prior art, the object of the present invention is to provide a sizing agent without organic solvent and a preparation method thereof.

[0006] According to one aspect of the present invention, there is provided a sizing agent that does not contain an organic solvent. The sizing agent comprises the following components, calculated by weight: 40 to 50 parts of a dimer acid-modified epoxy resin, 5 to 8 parts of a polyethylene glycol-modified epoxy resin, 0.01 to 0.3 parts of a leveling agent, and the remainder of water; wherein:

[0007] In the dimer acid modified epoxy resin, the epoxy equivalent is 450 to 550 g / eq;

[0008] In the polyethylene glycol-modified epoxy resin, the molar ratio of polyethylene glycol to epoxy resin is (1-2): (1-2).

[0009] Optionally, in the polyethylene glycol-modified epoxy resin, the molecular weight of the epoxy resin is 360-900, and the molecular weight of the polyethylene glycol is 2000-6000.

[0010] Optionally, the polyethylene glycol-modified epoxy resin is prepared by a method comprising:

[0011] mixing polyethylene glycol and an accelerator to obtain a mixture;

[0012] mixing the epoxy resin and the diluent to obtain a mixed solution;

[0013] adding the mixed liquid into the mixture, heating and stirring;

[0014] After the reaction is completed, water is added to dilute the mixture and distilled until the solid content reaches 50%, thereby obtaining a polyethylene glycol-modified epoxy resin.

[0015] Optionally, the accelerator is any one of boron trifluoride ethyl ether, boron trifluoride ethylamine, ethyltriphenylphosphonium bromide and tetrabutylammonium bromide, or a mixture of two or more thereof.

[0016] Optionally, the dimer acid-modified epoxy resin includes E51 epoxy resin, bisphenol A epoxy resin and dimer acid, and the mass ratio of the three is (55-80):(4-14):(4-14).

[0017] Optionally, the dimer acid-modified epoxy resin is prepared by a method comprising:

[0018] The epoxy resin and dimer acid are mixed uniformly, a catalyst is added under heating conditions, the reaction is carried out at a constant temperature until the epoxy equivalent is 450-550 g / eq, the reaction is stopped by cooling, and the dimer acid-modified epoxy resin is obtained.

[0019] Optionally, the catalyst is tetrabutylammonium bromide and / or ethyltriphenylphosphonium bromide.

[0020] Optionally, the leveling agent is any one of BYK-306, BYK-307, BYK-333, BYK-346, BYK-348 and BYK-349, or a mixture of two or more thereof.

[0021] Optionally, the viscosity of the sizing agent is 2500-3500 mPa·s, and the particle size D90 of the sizing agent is less than 0.9 μm.

[0022] According to another aspect of the present invention, there is provided a method for preparing the above-mentioned sizing agent free of organic solvent, the method comprising:

[0023] Under the condition of temperature of 40-55° C., the dimer acid modified epoxy resin and the polyethylene glycol modified epoxy resin are stirred and mixed uniformly;

[0024] Add water under stirring to reduce the viscosity of the system to the target viscosity;

[0025] A leveling agent is added and stirred evenly to obtain a sizing agent free of organic solvents.

[0026] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0027] 1. The organic solvent-free sizing agent provided by the present invention has a bio-based modified epoxy resin (dimer acid modified epoxy resin) as a main component, and is added with auxiliary components such as a leveling agent to have excellent flexibility and adhesion, and can form a uniform and dense film on the surface of the carbon fiber, thereby enhancing the interface bonding strength between the carbon fiber and the matrix material;

[0028] 2. The sizing agent provided by the present invention does not contain organic solvents, thus avoiding the environmental pollution and human health hazards that may be caused by traditional sizing agents during preparation and use, and can be widely used in the preparation of carbon fiber composite materials, including but not limited to aerospace, automobile manufacturing, sporting goods and other fields;

[0029] 3. The present invention adopts polyethylene glycol-modified epoxy resin to uniformly disperse dimer acid-modified epoxy resin and polyethylene glycol-modified epoxy resin in water to form a sizing agent with excellent particle size, thereby effectively improving the wettability and interface bonding performance of carbon fiber;

[0030] 4. By using the solvent-free sizing agent provided by the present invention, the interface bonding performance and mechanical properties of carbon fiber composite materials can be effectively improved, the production cost can be reduced, and the application and development of carbon fiber composite materials in various fields can be promoted. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0032] Figure 1 The figure is a schematic flow chart of a method for preparing a sizing agent free of organic solvents in one embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0034] The embodiment of the present invention provides a sizing agent that does not contain an organic solvent. The sizing agent includes the following components, calculated by weight: 40 to 50 parts of dimer acid-modified epoxy resin, 5 to 8 parts of polyethylene glycol-modified epoxy resin, 0.01 to 0.3 parts of leveling agent, and water balance; wherein: in the dimer acid-modified epoxy resin, the epoxy equivalent is 450 to 550 g / eq; in the polyethylene glycol-modified epoxy resin, the molar ratio of polyethylene glycol to epoxy resin is (1 to 2): (1 to 2), preferably, the molar ratio of polyethylene glycol to epoxy resin is 1: 1. Thus, a polyethylene glycol-modified epoxy resin with a large relative molecular weight can be prepared to achieve a better particle size standard.

[0035] In the embodiment of the present invention, epoxy equivalent refers to the number of moles of epoxy groups contained in each gram of epoxy resin. When the epoxy equivalent is within the range of 450 to 550 g / eq, the viscosity of the epoxy resin in the sizing agent formulation can be moderate, which is beneficial to the construction and use of the sizing agent. The sizing agent formed by the epoxy resin within this range has a low viscosity and is easy to coat and impregnate, thereby improving production efficiency and product uniformity; at the same time, it can provide a higher cross-linking density, enhance the strength and toughness of the material, thereby improving the impact resistance and wear resistance of the sizing agent, and ensuring the stability and durability of the final product in the application.

[0036] In some embodiments, in the polyethylene glycol-modified epoxy resin, the molecular weight of the epoxy resin is 360 to 900, and the molecular weight of the polyethylene glycol is 2000 to 6000. After being modified with polyethylene glycol, the epoxy resin with a molecular weight of 360 to 900 can provide an appropriate balance of hydrophilicity and hydrophobicity, which enables the modified epoxy resin to effectively reduce surface tension, increase its effectiveness as a surfactant, and enhance its activity and stability at the interface. The molecular weight of polyethylene glycol (PEG) is 2000 to 6000, which can provide a higher hydrophilicity, help the modified epoxy resin maintain good solubility and dispersibility in aqueous solution, and make it perform well as a surfactant in a water-based system; and form a stable hydrophobic segment in the modified epoxy resin, enhance the stability of the epoxy resin at the interface, and improve its surface activity and interfacial stability.

[0037] In some embodiments, the preparation method of the above-mentioned polyethylene glycol-modified epoxy resin includes: mixing polyethylene glycol and a promoter to obtain a mixture; mixing an epoxy resin and a diluent to obtain a mixed liquid; adding the mixed liquid to the mixture, heating and stirring; after the reaction is completed, diluting with water, and distilling to a solid content of 50% to obtain a polyethylene glycol-modified epoxy resin.

[0038] Exemplarily, the preparation method of polyethylene glycol-modified epoxy resin is as follows: under nitrogen protection, polyethylene glycol is put into a kettle and heated to 110-130°C; water is removed by vacuum, a promoter is added, and the temperature is maintained at 90-110°C, and then epoxy resin and diluent are put into another dropping kettle, mixed, heated and stirred evenly; the mixture is added dropwise to the polyethylene glycol mixture, and the dropping time is within 20-40 minutes. After the dropping is completed, stirring and reacting at 95-110°C for 40 minutes; after the reaction is completed, water is added to dilute it to a solid content of 50%, and then it is distilled under reduced pressure; after all the diluent is distilled out, water is continued to be added to dilute it to a solid content of 50%, thereby obtaining polyethylene glycol-modified epoxy resin.

[0039] In some preferred embodiments, the accelerator is any one of boron trifluoride ethyl ether, boron trifluoride ethylamine, ethyl triphenylphosphonium bromide and tetrabutylammonium bromide, or a mixture of two or more thereof, to promote the reaction between epoxy groups and hydroxyl groups. The amount of the diluent added is 12-15% of the total weight of the polyethylene glycol and the epoxy resin, and the amount of the diluent added is the minimum amount of diluent added to ensure the maximum molecular weight of the polyethylene glycol-modified epoxy resin, that is, using more diluent cannot produce a resin with a larger molecular weight.

[0040] In some embodiments, the dimer acid modified epoxy resin includes E51 epoxy resin, bisphenol A epoxy resin and dimer acid, and the mass ratio of the three is (55-80): (4-14): (4-14). The amount of dimer acid added can reach the viscosity value of emulsification. If more dimer acid is added, the particle size of the sizing agent will be significantly reduced.

[0041] E51 epoxy resin is a liquid bisphenol A epoxy resin with excellent mechanical properties, bonding properties, chemical stability and low viscosity; while bisphenol A epoxy resin is a high-performance solid epoxy resin with high glass transition temperature, excellent mechanical strength and rigidity. By adjusting the ratio of E51 epoxy resin and bisphenol A epoxy resin, a good balance between low viscosity and high mechanical properties can be achieved. The lower viscosity of E51 epoxy resin can improve mixing and coating properties, while bisphenol A epoxy resin provides high strength and rigidity; this allows the epoxy resin to have good fluidity during processing, and will not affect the mechanical properties after curing due to too low viscosity, improving the operability of the resin and facilitating its application in various process flows.

[0042] In some embodiments, the preparation method of the dimer acid-modified epoxy resin includes: mixing the epoxy resin and the dimer acid evenly, adding a catalyst under heating conditions, reacting at a constant temperature until the epoxy equivalent is 450 to 550 g / eq, cooling to stop the reaction, and obtaining the dimer acid-modified epoxy resin.

[0043] Exemplarily, the preparation method of dimer acid modified epoxy resin includes: mixing E51 epoxy resin, bisphenol A epoxy resin, and dimer acid uniformly, heating to 80-140°C, adding a catalyst, heating to 140-190°C, reacting at a constant temperature until the epoxy equivalent of the system is 450-550, and then cooling to below 100°C to obtain a light yellow dimer acid modified epoxy resin.

[0044] In some embodiments, the catalyst is tetrabutylammonium bromide and / or ethyltriphenylphosphonium bromide, which can promote faster and more complete reaction of E51 epoxy resin with bisphenol A epoxy resin and dimer acid.

[0045] In some embodiments, the leveling agent is any one of BYK-306, BYK-307, BYK-333, BYK-346, BYK-348 and BYK-349, or a mixture of two or more thereof, so as to increase the surface energy of the sizing agent.

[0046] The sizing agent in the above embodiment of the present invention has a viscosity of 2500-3500 mPa·s due to the interaction between the components, and the particle size D90 (D90 means that 90% of the particles in the sizing agent are smaller than 0.9 microns) of the sizing agent is lower than 0.9 μm.

[0047] Reference Figure 1 As shown, another embodiment of the present invention provides a method for preparing the above-mentioned sizing agent without organic solvent, comprising the following steps:

[0048] S1. Stir and mix the dimer acid-modified epoxy resin and the polyethylene glycol-modified epoxy resin evenly at a temperature of 40 to 55° C.;

[0049] S2. Add water under stirring to reduce the viscosity of the system to a target viscosity; specifically, the target viscosity is 2500-3500 mPa·s; preferably, add the water in the formula dropwise within 5 hours at a temperature of 40-55° C.;

[0050] S3, adding a leveling agent, stirring evenly, and obtaining a sizing agent free of organic solvents.

[0051] In step S1, the temperature is set so that the emulsified viscosity of the epoxy resin can reach the optimal range. If it is lower than 40°C, the viscosity is too high and the emulsification step cannot be carried out; if it is higher than 55°C, the shear force in the emulsification stage will be low and a better particle size cannot be obtained.

[0052] In the sizing agent preparation method of the above embodiment of the present invention, since the dimer acid-modified epoxy resin is the main part, it needs to be added first, and the polyethylene glycol-modified epoxy resin is a hydrophilic group and needs to be added before the step of adding water. By adding water at a certain speed within a certain period of time, a higher shear force is achieved during the emulsification process of adding water, forming a sizing agent with a target viscosity and excellent particle size.

[0053] In the above-mentioned embodiment of the present invention, since the epoxy resin is modified by dimer acid, the viscosity of the epoxy resin is significantly reduced by adding dimer acid, so that the viscosity requirement of processing can be achieved without adding organic solvents in the subsequent process; and oleic acid and the like are introduced into the epoxy resin by chemical methods to prepare dimer acid-modified epoxy resin, which also significantly enhances the wettability of the sizing agent on the surface of the carbon fiber; in addition, by using polyethylene glycol to modify the epoxy resin, the modified epoxy resin can be evenly dispersed in water to form a sizing agent with excellent particle size, which effectively improves the wettability and interface bonding performance of the carbon fiber.

[0054] The scheme of the present application will be explained below in conjunction with specific embodiments and comparative examples. It will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If no specific technology or conditions are indicated in the embodiments, the technology or conditions described in the literature in this area or the product specification are carried out. The reagents used or the instruments that do not indicate the manufacturer are all conventional products that can be obtained through commercial channels.

[0055] The materials used in the following examples are as follows:

[0056] Leveling agent: BYK-333; BYK Chemical;

[0057] Polyethylene glycol: polyethylene glycol PEG4000, molecular weight 4000; polyethylene glycol PEG2000, molecular weight; polyethylene glycol PEG6000, molecular weight; Lotte, South Korea;

[0058] Bisphenol A epoxy resin: molecular weight 380;

[0059] E51 epoxy resin: Nanya resin;

[0060] The diluent is acetone; Sinopharm reagent;

[0061] The accelerator is boron trifluoride etherate; Sinopharm reagent;

[0062] The catalyst is ethyltriphenylphosphonium bromide; Sinopharm reagent;

[0063] Dimer acid: Morinaga, Japan;

[0064] Example 1

[0065] The sizing agent provided in this embodiment that does not contain an organic solvent includes the following components, calculated by weight: 40 parts of dimer acid-modified epoxy resin, 5 parts of polyethylene glycol-modified epoxy resin, 0.01 parts of a leveling agent, and 45 parts of water.

[0066] The preparation method thereof comprises the following steps:

[0067] S1. Under nitrogen protection, polyethylene glycol PEG4000 is put into a kettle and heated to 110°C, then the water is removed in vacuo, 0.05 parts of accelerator are added, the temperature is maintained at 110°C, and then in another dropping kettle, the epoxy resin with the same molar mass as the polyethylene glycol input and 12% of the weight of the diluent of the above two substances are put, mixed, heated and stirred evenly, and then added to the above polyethylene glycol mixture by a dropwise method, the dropping time is within 20 minutes, after the dropwise addition is completed, stirring and reacting at 95°C for 40 minutes, the reaction is completed, water is added to dilute it to its solid content of 50%, and then reduced pressure distillation is performed. After all the diluents are distilled out, water is continued to be added to dilute it to its solid content of 50%, and polyethylene glycol-modified epoxy resin is obtained;

[0068] S2, 55 parts of 128 epoxy resin, 6 parts of bisphenol A epoxy resin, and 10 parts of dimer acid were mixed uniformly, then heated to 80°C, 0.1 parts of ethyltriphenylphosphine bromide were added, and the temperature was raised to 140°C. After constant temperature reaction until the epoxy equivalent of the system was 450g / eq, the temperature was lowered to below 100°C to obtain a light yellow dimer acid-modified epoxy resin;

[0069] S3. At a temperature of 50° C., polyethylene glycol-modified epoxy resin and dimer acid-modified epoxy resin are stirred and mixed uniformly in a weight ratio of 6:100. An appropriate amount of water is slowly added under high-speed stirring to reduce the viscosity of the system to 3300 mPa·s. A leveling agent is added and stirred uniformly to obtain a sizing agent free of organic solvents.

[0070] Example 2

[0071] The sizing agent provided in this embodiment that does not contain an organic solvent includes the following components, calculated by weight: 50 parts of dimer acid-modified epoxy resin, 8 parts of polyethylene glycol-modified epoxy resin, 0.3 parts of a leveling agent, and 55 parts of water.

[0072] The preparation method thereof comprises the following steps:

[0073] S1. Under nitrogen protection, polyethylene glycol PEG4000 is put into a kettle and heated to 110°C, then the water is removed in vacuo, 0.3 parts of accelerator is added, the temperature is maintained at 100°C, and then in another dropping kettle, the epoxy resin with the same molar mass as the polyethylene glycol input and 15% of the weight of the diluent of the above two substances are put, mixed, heated and stirred evenly, and then added to the above polyethylene glycol mixture by a dropwise method, the dropping time is within 20min, after the dropwise addition is completed, stirring and reacting at 110°C for 40min, the reaction is completed, water is added to dilute it to its solid content of 50%, and then reduced pressure distillation is performed. After all the diluents are distilled out, water is continued to be added to dilute it to its solid content of 50%, and polyethylene glycol-modified epoxy resin is obtained;

[0074] S2, 60 parts of 128 epoxy resin, 8 parts of bisphenol A epoxy resin, and 16 parts of dimer acid were mixed uniformly, then heated to 80°C, 0.1 parts of ethyltriphenylphosphine bromide were added, and the temperature was raised to 140°C. After constant temperature reaction until the epoxy equivalent of the system was 450g / eq, the temperature was lowered to below 100°C to obtain a light yellow dimer acid-modified epoxy resin;

[0075] S3. At a temperature of 50° C., polyethylene glycol-modified epoxy resin and dimer acid-modified epoxy resin are stirred and mixed uniformly in a weight ratio of 10:100. An appropriate amount of water is slowly added under high-speed stirring to reduce the viscosity of the system to 3100 mPa·s. A leveling agent is added and stirred uniformly to obtain a sizing agent free of organic solvents.

[0076] Example 3

[0077] The sizing agent provided in this embodiment that does not contain an organic solvent includes the following components, calculated by weight: 45 parts of dimer acid-modified epoxy resin, 6 parts of polyethylene glycol-modified epoxy resin, 0.1 parts of a leveling agent, and 48 parts of water.

[0078] The preparation method thereof comprises the following steps:

[0079] S1. Under nitrogen protection, polyethylene glycol PEG4000 is put into a kettle and heated to 120°C, then the water is removed in vacuo, 0.1 parts of accelerator are added, the temperature is maintained at 90°C, and then in another dropping kettle, the epoxy resin with the same molar mass as the polyethylene glycol input and 14% of the weight of the diluent of the above two substances are put, mixed, heated and stirred evenly, and then added to the above polyethylene glycol mixture by a dropwise method, the dropping time is within 30 minutes, after the dropwise addition is completed, stirring and reacting at 110°C for 40 minutes, the reaction is completed, water is added to dilute it to its solid content of 50%, and then reduced pressure distillation is performed. After all the diluents are distilled out, water is continued to be added to dilute it to its solid content of 50%, and polyethylene glycol-modified epoxy resin is obtained;

[0080] S2, 65 parts of 128 epoxy resin, 10 parts of bisphenol A epoxy resin, and 14 parts of dimer acid were mixed uniformly, then heated to 80°C, 0.1 parts of ethyltriphenylphosphine bromide were added, and the temperature was raised to 140°C. After constant temperature reaction until the epoxy equivalent of the system was 450g / eq, the temperature was lowered to below 100°C to obtain a light yellow dimer acid-modified epoxy resin;

[0081] S3. At a temperature of 40° C., polyethylene glycol-modified epoxy resin and dimer acid-modified epoxy resin are stirred and mixed uniformly in a weight ratio of 10:100. An appropriate amount of water is slowly added under high-speed stirring to reduce the viscosity of the system to 2950 mPa·s. A leveling agent is added and stirred uniformly to obtain a sizing agent free of organic solvents.

[0082] Example 4

[0083] The sizing agent provided in this embodiment that does not contain an organic solvent includes the following components, calculated by weight: 42 parts of dimer acid-modified epoxy resin, 5.5 parts of polyethylene glycol-modified epoxy resin, 0.2 parts of a leveling agent, and 44 parts of water.

[0084] The preparation method thereof comprises the following steps:

[0085] S1. Under nitrogen protection, polyethylene glycol PEG4000 is put into a kettle and heated to 110°C, then the water is removed in vacuo, 0.2 parts of accelerator are added, the temperature is maintained at 90°C, and then in another dropping kettle, the epoxy resin with the same molar mass as the polyethylene glycol input and 12% of the weight of the diluent of the above two substances are put, mixed, heated and stirred evenly, and then added to the above polyethylene glycol mixture by a dropwise method, the dropping time is within 20min, after the dropwise addition is completed, stirring and reacting at 110°C for 40min, the reaction is completed, water is added to dilute it to its solid content of 50%, and then reduced pressure distillation is performed. After all the diluents are distilled out, water is continued to be added to dilute it to its solid content of 50%, and polyethylene glycol-modified epoxy resin is obtained;

[0086] S2, 70 parts of 128 epoxy resin, 12 parts of bisphenol A epoxy resin, and 15 parts of dimer acid were mixed uniformly, then heated to 80°C, 0.1 parts of ethyl triphenylphosphine bromide were added, and the temperature was raised to 140°C. After constant temperature reaction until the epoxy equivalent of the system was 450g / eq, the temperature was lowered to below 100°C to obtain a light yellow dimer acid-modified epoxy resin;

[0087] S3. At a temperature of 45° C., polyethylene glycol-modified epoxy resin and dimer acid-modified epoxy resin are stirred and mixed uniformly in a weight ratio of 8:100. An appropriate amount of water is slowly added under high-speed stirring to reduce the viscosity of the system to 3000 mPa·s. A leveling agent is added and stirred uniformly to obtain a sizing agent free of organic solvents.

[0088] Example 5

[0089] The sizing agent provided in this embodiment that does not contain an organic solvent includes the following components, calculated by weight: 44 parts of dimer acid-modified epoxy resin, 6.5 parts of polyethylene glycol-modified epoxy resin, 0.15 parts of a leveling agent, and 46 parts of water.

[0090] The preparation method thereof comprises the following steps:

[0091] S1. Under nitrogen protection, polyethylene glycol PEG4000 is put into a kettle and heated to 110°C, then the water is removed in vacuo, 0.3 parts of accelerator is added, the temperature is maintained at 90°C, and then in another dropping kettle, the epoxy resin with the same molar mass as the polyethylene glycol input and 15% of the weight of the diluent of the above two substances are put, mixed, heated and stirred evenly, and then added to the above polyethylene glycol mixture by a dropwise method, the dropping time is within 40min, after the dropwise addition is completed, stirring and reacting at 110°C for 40min, the reaction is completed, water is added to dilute it to its solid content of 50%, and then reduced pressure distillation is performed. After all the diluents are distilled out, water is continued to be added to dilute it to its solid content of 50%, and polyethylene glycol-modified epoxy resin is obtained;

[0092] S2, 75 parts of 128 epoxy resin, 14 parts of bisphenol A epoxy resin, and 13 parts of dimer acid were mixed uniformly, then heated to 80°C, 0.1 parts of ethyltriphenylphosphonium bromide were added, and the temperature was raised to 140°C. After constant temperature reaction until the epoxy equivalent of the system was 450g / eq, the temperature was lowered to below 100°C to obtain a light yellow dimer acid-modified epoxy resin;

[0093] S3. At a temperature of 50° C., polyethylene glycol-modified epoxy resin and dimer acid-modified epoxy resin are stirred and mixed uniformly in a weight ratio of 6:100. An appropriate amount of water is slowly added under high-speed stirring to reduce the viscosity of the system to 3150 mPa·s. A leveling agent is added and stirred uniformly to obtain a sizing agent free of organic solvents.

[0094] Example 6

[0095] The sizing agent provided in this embodiment that does not contain an organic solvent includes the following components, calculated by weight: 44 parts of dimer acid-modified epoxy resin, 6.5 parts of polyethylene glycol-modified epoxy resin, 0.15 parts of a leveling agent, and 47 parts of water.

[0096] The preparation method thereof comprises the following steps:

[0097] S1. Under nitrogen protection, polyethylene glycol PEG4000 is put into a kettle and heated to 110°C, then the water is removed in vacuo, 0.3 parts of accelerator is added, the temperature is maintained at 90°C, and then in another dropping kettle, the epoxy resin with the same molar mass as the polyethylene glycol input and 15% of the weight of the diluent of the above two substances are put, mixed, heated and stirred evenly, and then added to the above polyethylene glycol mixture by a dropwise method, the dropping time is within 40min, after the dropwise addition is completed, stirring and reacting at 110°C for 40min, the reaction is completed, water is added to dilute it to its solid content of 50%, and then reduced pressure distillation is performed. After all the diluents are distilled out, water is continued to be added to dilute it to its solid content of 50%, and polyethylene glycol-modified epoxy resin is obtained;

[0098] S2, 75 parts of 128 epoxy resin, 14 parts of bisphenol A epoxy resin, and 13 parts of dimer acid were mixed uniformly, then heated to 80°C, 0.1 parts of ethyltriphenylphosphonium bromide were added, and the temperature was raised to 140°C. After constant temperature reaction until the epoxy equivalent of the system was 450g / eq, the temperature was lowered to below 100°C to obtain a light yellow dimer acid-modified epoxy resin;

[0099] S3. At a temperature of 50° C., polyethylene glycol-modified epoxy resin and dimer acid-modified epoxy resin are stirred and mixed uniformly in a weight ratio of 6:100. An appropriate amount of water is slowly added under high-speed stirring to reduce the viscosity of the system to 3100 mPa·s. A leveling agent is added and stirred uniformly to obtain a sizing agent free of organic solvents.

[0100] Example 7

[0101] The sizing agent provided in this embodiment that does not contain an organic solvent includes the following components, calculated by weight: 48 parts of dimer acid-modified epoxy resin, 7.5 parts of polyethylene glycol-modified epoxy resin, 0.3 parts of a leveling agent, and 50 parts of water.

[0102] The preparation method thereof comprises the following steps:

[0103] S1. Under nitrogen protection, polyethylene glycol PEG4000 is put into a kettle and heated to 130°C, then the water is removed in vacuo, 0.3 parts of accelerator is added, the temperature is maintained at 110°C, and then in another dropping kettle, the epoxy resin with the same molar mass as the polyethylene glycol input and 13% of the weight of the diluent of the above two substances are put, mixed, heated and stirred evenly, and then added to the above polyethylene glycol mixture by a dropwise method, the dropping time is within 30min, after the dropwise addition is completed, stirring and reacting at 105°C for 40min, the reaction is completed, water is added to dilute it to its solid content of 50%, and then reduced pressure distillation is performed. After all the diluents are distilled out, water is continued to be added to dilute it to its solid content of 50%, and polyethylene glycol-modified epoxy resin is obtained;

[0104] S2, 55 parts of 128 epoxy resin, 12 parts of bisphenol A epoxy resin, and 6 parts of dimer acid were mixed uniformly, then heated to 80°C, 0.1 parts of ethyltriphenylphosphine bromide were added, and the temperature was raised to 140°C. After constant temperature reaction until the epoxy equivalent of the system was 450g / eq, the temperature was lowered to below 100°C to obtain a light yellow dimer acid-modified epoxy resin;

[0105] S3. At a temperature of 40° C., polyethylene glycol-modified epoxy resin and dimer acid-modified epoxy resin are stirred and mixed uniformly in a weight ratio of 8:100. An appropriate amount of water is slowly added under high-speed stirring to reduce the viscosity of the system to 3500 mPa·s. A leveling agent is added and stirred uniformly to obtain a sizing agent free of organic solvents.

[0106] Example 8

[0107] The sizing agent provided in this embodiment that does not contain an organic solvent includes the following components, calculated by weight: 50 parts of dimer acid-modified epoxy resin, 5 parts of polyethylene glycol-modified epoxy resin, 0.1 parts of a leveling agent, and 47 parts of water.

[0108] The preparation method thereof comprises the following steps:

[0109] S1. Under nitrogen protection, polyethylene glycol PEG4000 is put into a kettle and heated to 110°C, then the water is removed in vacuo, 0.053 parts of accelerator are added, the temperature is maintained at 100°C, and then in another dropping kettle, the epoxy resin with the same molar mass as the polyethylene glycol input and 13% of the weight of the diluent of the above two substances are put, mixed, heated and stirred evenly, and then added to the above polyethylene glycol mixture by a dropwise method, the dropping time is within 40min, after the dropwise addition is completed, stirring and reacting at 95°C for 40min, the reaction is completed, water is added to dilute it to its solid content of 50%, and then reduced pressure distillation is performed. After all the diluents are distilled out, water is continued to be added to dilute it to its solid content of 50%, and polyethylene glycol-modified epoxy resin is obtained;

[0110] S2, 73 parts of 128 epoxy resin, 13 parts of bisphenol A epoxy resin, and 15 parts of dimer acid were mixed uniformly, then heated to 80°C, 0.1 parts of ethyltriphenylphosphonium bromide were added, and the temperature was raised to 140°C. After constant temperature reaction until the epoxy equivalent of the system was 450g / eq, the temperature was lowered to below 100°C to obtain a light yellow dimer acid-modified epoxy resin;

[0111] S3. At a temperature of 45° C., polyethylene glycol-modified epoxy resin and dimer acid-modified epoxy resin are stirred and mixed uniformly in a weight ratio of 10:100. An appropriate amount of water is slowly added under high-speed stirring to reduce the viscosity of the system to 3150 mPa·s. A leveling agent is added and stirred uniformly to obtain a sizing agent free of organic solvents.

[0112] Comparative Example 1

[0113] The difference between Comparative Example 1 and Example 8 is that, in Comparative Example 1, no modified epoxy resin is used, and Nan Ya E20 epoxy resin with an epoxy equivalent of 450 is added.

[0114] Comparative Example 2

[0115] The difference between Comparative Example 2 and Example 8 is that the polyethylene glycol used in Comparative Example 2 is PEG2000.

[0116] Comparative Example 3

[0117] The difference between Comparative Example 3 and Example 8 is that the polyethylene glycol used in the comparative example is PEG6000.

[0118] Comparative Example 4

[0119] The difference between Comparative Example 4 and Example 8 is that the epoxy resin used in the comparative example is Nan Ya 128 epoxy resin.

[0120] Comparative Example 5

[0121] The difference between Comparative Example 5 and Example 8 is that the polyethylene glycol-modified epoxy resin in Comparative Example 6 is prepared according to the following steps:

[0122] Under nitrogen protection, polyethylene glycol and epoxy with equal molar mass are put into an autoclave and heated to 110°C, then the moisture is removed in vacuo, 0.053 parts of accelerator is added, and the temperature is maintained at 100°C. When the viscosity increases to 100 poise, the reaction is completed, and water is added to dilute it to 50% of the solid content to obtain polyethylene glycol-modified epoxy resin.

[0123] Comparative Example 6

[0124] The difference between Comparative Example 6 and Example 8 is that the sizing agent in Comparative Example 7 is prepared specifically according to the following steps:

[0125] At a temperature of 65° C., the obtained polyethylene glycol-modified epoxy resin and dimer acid-modified epoxy resin were stirred and mixed uniformly in a weight ratio of 10:100. An appropriate amount of water was slowly added under high-speed stirring to reduce the viscosity of the system to 3000±500 mPa·s. A leveling agent was added and stirred uniformly to obtain an organic solvent-free sizing agent.

[0126] The sizing agent obtained in Examples 1 to 8 and Comparative Examples 1 to 7 was used to size the T700 carbon fiber after the precursor was pre-oxidized, carbonized, and surface treated, with a sizing amount of 1%, and then dried at 200 to 300°C, collected, and treated to evaluate its performance. The specific steps are as follows:

[0127] First, the T700 carbon fiber is cleaned in a pretreatment tank to remove impurities and grease on the surface to ensure that the fiber surface is clean and pollution-free. The pretreated carbon fiber is immersed in the sizing agent for a certain period of time to ensure that the sizing agent fully penetrates the fiber surface. Then, the impregnated carbon fiber is passed through an extrusion roller to remove excess sizing agent and dried in an oven at a temperature set to 120°C for about 30 minutes.

[0128] The performance tests of the sizing agents in the above embodiments and comparative examples are as follows:

[0129] The amount of fuzz: Determined according to the method (II) in the friction coefficient determination method of "Carbon Fiber and Graphite Fiber". The carbon fiber is sandwiched between two polyurethane sponges, and the fiber passes through the sponge at a speed of 0.5m / min. The mass difference before and after the sponge is measured as the amount of fuzz, and the pre-tension is 1g / tex.

[0130] Interlaminar shear: measured in accordance with JC / T773-2010.

[0131] Actual pulp volume determination: Determine according to the Soxhlet extraction method in method A of national standard GB / T 29761-2013.

[0132] Stability test: Place the sizing agent in a constant temperature environment of 50°C for one month, and observe the morphological changes, stratification, demulsification and other phenomena after one month.

[0133] Particle size test: Use Malvern 3000 particle size analyzer to test the particle size, and take D90, that is, 90% of the particle diameter is less than or equal to this value, as the main indicator of particle size.

[0134] The performance test results are shown in Table 1, which shows the test results of T700 grade carbon fiber of Examples 1 to 8 and Comparative Examples 1 to 6 with a sizing amount of 1%.

[0135] Table 1 Test results of T700 carbon fiber with sizing amount of 1%

[0136]

[0137] According to the above test results, the amount of hair, interlaminar shear and storage stability of the sizing agent in Examples 1 to 8 can all reach a good level. The difference between the various examples is mainly the different ratios between the dimer acid-modified epoxy resin and the polyethylene glycol-modified epoxy resin. In comparison, the higher the mass ratio of the polyethylene glycol-modified epoxy resin, the better the particle size of the prepared sizing agent.

[0138] The difference between Comparative Example 1 and Example 8 is that Comparative Example 1 does not use modified epoxy resin, but adds Nan Ya E20 epoxy resin with an epoxy equivalent of 450, which has a higher amount of fuzz. This is because the E20 epoxy resin itself has a higher hardness, poor lubrication effect, and insufficient adhesion to the carbon fiber surface, which increases the generation of fuzz.

[0139] The difference between Comparative Example 2 and Example 8 is that the polyethylene glycol used in Comparative Example 2 is PEG2000, and the stability of the sizing agent is poor. This is because the particle size of the sizing agent prepared by PEG2000 is poor, resulting in poor dispersibility in the epoxy resin, which affects the stability of the sizing agent and the uniformity of the carbon fiber surface. This leads to an increase in the amount of fuzz and a decrease in interlaminar shear strength.

[0140] The difference between Comparative Example 3 and Example 8 is that the polyethylene glycol used in the comparative example is PEG6000. The amount of fuzz is high and the interlaminar shear strength is low, which may be because the molecular weight of PEG6000 is large, resulting in a high viscosity of the modified epoxy resin, making it difficult to form a uniform sizing layer on the carbon fiber surface.

[0141] The difference between Comparative Example 4 and Example 8 is that the epoxy resin used in the comparative example is Nan Ya 128 epoxy resin. The prepared sizing agent cannot be in a stable emulsion state.

[0142] The difference between Comparative Example 5 and Example 8 is that the method of preparing polyethylene glycol epoxy resin is changed, and no diluent is used in the manufacturing process. The amount of fuzz is high and the interlaminar shear strength is low, which is the reason why the particle size of the sizing agent is coarse. Because no diluent is used in the manufacturing process, the molecular weight of the prepared polyethylene glycol epoxy resin is small, which affects the particle size of the sizing agent.

[0143] The difference between Comparative Example 6 and Example 8 is that the temperature during the preparation of the sizing agent is 65°C. The amount of prepared hair is relatively high because the particle size of the sizing agent is relatively coarse, because during the preparation of the emulsion, due to the high temperature, it does not form a uniform particle size distribution under a high shear environment. In addition, due to the high temperature, part of the polyethylene glycol-modified epoxy resin may be thermally degraded, affecting the stability of the sizing agent and the adhesion of the carbon fiber surface.

[0144] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various modifications or variations within the scope of the claims, which does not affect the essence of the present invention. The above preferred features can be used in any combination without conflicting with each other.

Claims

1. A sizing agent containing no organic solvent, It is characterized in that The composition includes the following components calculated by weight: 40-50 parts of dimer acid modified epoxy resin, 5-8 parts of polyethylene glycol modified epoxy resin, 0.01-0.3 parts of leveling agent and the balance of water; wherein: In the dimer acid modified epoxy resin, the epoxy equivalent is 450 to 550 g / eq; In the polyethylene glycol-modified epoxy resin, the molar ratio of polyethylene glycol to epoxy resin is (1-2): (1-2).

2. The sizing agent containing no organic solvent according to claim 1, It is characterized in that In the polyethylene glycol-modified epoxy resin, the molecular weight of the epoxy resin is 360-900, and the molecular weight of the polyethylene glycol is 2000-6000.

3. The sizing agent containing no organic solvent according to claim 1, It is characterized in that The polyethylene glycol modified epoxy resin, the preparation method thereof comprises: mixing polyethylene glycol and an accelerator to obtain a mixture; mixing the epoxy resin and the diluent to obtain a mixed solution; adding the mixed liquid into the mixture, heating and stirring; After the reaction is completed, water is added to dilute the mixture and distilled until the solid content reaches 50%, thereby obtaining a polyethylene glycol-modified epoxy resin.

4. The sizing agent containing no organic solvent according to claim 3, It is characterized in that The accelerator is any one of boron trifluoride ethyl ether, boron trifluoride ethylamine, ethyltriphenylphosphonium bromide and tetrabutylammonium bromide, or a mixture of two or more thereof.

5. The sizing agent containing no organic solvent according to claim 1, It is characterized in that The dimer acid modified epoxy resin comprises E51 epoxy resin, bisphenol A epoxy resin and dimer acid, and the mass ratio of the three is (55-80):(4-14):(4-14).

6. The sizing agent containing no organic solvent according to claim 1, It is characterized in that The dimer acid modified epoxy resin, the preparation method thereof comprises: The epoxy resin and dimer acid are mixed uniformly, a catalyst is added under heating conditions, the reaction is carried out at a constant temperature until the epoxy equivalent is 450-550 g / eq, the reaction is stopped by cooling, and the dimer acid-modified epoxy resin is obtained.

7. The sizing agent containing no organic solvent according to claim 6, It is characterized in that The catalyst is tetrabutylammonium bromide and / or ethyltriphenylphosphonium bromide.

8. The sizing agent containing no organic solvent according to claim 1, It is characterized in that The leveling agent is any one of BYK-306, BYK-307, BYK-333, BYK-346, BYK-348 and BYK-349, or a mixture of two or more thereof.

9. The sizing agent containing no organic solvent according to claim 1, It is characterized in that The viscosity of the sizing agent is 2500-3500 mPa·s, and the particle size D90 of the sizing agent is less than 0.9 μm.

10. A method for preparing a sizing agent containing no organic solvent according to any one of claims 1 to 9, It is characterized in that include: Under the condition of temperature of 40-55° C., the dimer acid modified epoxy resin and the polyethylene glycol modified epoxy resin are stirred and mixed uniformly; Add water under stirring to reduce the viscosity of the system to the target viscosity; A leveling agent is added and stirred evenly to obtain a sizing agent free of organic solvents.

Images