A method for producing an epoxy resin prepreg

Abstract

The present application relates to the technical field of prepreg preparation, and particularly relates to a preparation method of epoxy resin prepreg. The method comprises the following steps: a first resin film with low surface density is prepared by using epoxy resin without adding a thixotropic agent; the first resin film is used as upper and lower adhesive films, and then epoxy resin with the thixotropic agent is coated to prepare a second resin film; after the second resin film is stripped of the upper and lower adhesive films, the second resin film is combined with reinforcing fibers under a preset temperature and a preset pressure to prepare the epoxy resin prepreg. The purpose of the preparation method of the epoxy resin prepreg is to solve the problem of low accuracy of resin content of the prepreg caused by the addition of the thixotropic agent in the traditional epoxy resin preparation process.

Description

Technical Field

[0001] This invention relates to the field of prepreg preparation technology, and specifically to a method for preparing epoxy resin prepreg. Background Technology

[0002] Prepregs are composite materials made by impregnating continuous fibers or fabrics with a resin matrix under strictly controlled conditions, forming a combination of resin matrix and reinforcement. Currently, the most widely used prepreg types in aerospace and other fields are epoxy resin prepregs, bismaleimide resin prepregs, and polyimide resin prepregs. Among these, epoxy resin prepregs have the largest usage and the widest application. Epoxy resins possess excellent physicochemical and mechanical properties, but their disadvantages include brittleness, poor toughness, low corrosion resistance, and low abrasion resistance. Generally, organic toughening agents or inorganic fillers are added to improve their performance and reduce costs. However, highly filled epoxy resins with more fillers have higher viscosity and poorer flowability, affecting the molding processability of composite materials and the internal quality of the final composite product.

[0003] Therefore, in practical engineering applications, epoxy resins are generally mixed with epoxy thixotropic agents through high-speed shear dispersion to alter the resin's flowability and achieve a lower viscosity. Simultaneously, the presence of the epoxy thixotropic agent allows the entire epoxy resin to form a continuous network. Some thixotropic agents can also form chemical bonds with the epoxy resin matrix, causing the entire resin system to aggregate and form a three-dimensional network structure, preventing the already fluid epoxy resin from flowing. At this point, the epoxy resin possesses both a certain degree of flowability and can quickly cure and maintain a specific shape. When this epoxy resin is prepared into a prepreg, and then into a composite material blank intermediate of a certain shape, the three-dimensional network within the epoxy resin in the blank intermediate is disrupted during the curing process due to increased temperature and pressure. The resin begins to flow, thus wetting the fibers and carrying away some of the air trapped during resin and prepreg preparation, improving the internal quality of the final composite material product.

[0004] Therefore, the inventors provide a method for preparing epoxy resin prepreg. Summary of the Invention

[0005] (1) Technical problems to be solved

[0006] This invention provides a method for preparing epoxy resin prepreg, which solves the technical problem of low accuracy of resin content in prepreg due to the addition of thixotropic agents in the traditional epoxy resin preparation process.

[0007] (2) Technical solution

[0008] This invention provides a method for preparing epoxy resin prepreg, comprising the following steps:

[0009] Step 1: Prepare a first resin film with low areal density using epoxy resin without added thixotropic agent;

[0010] Step 2: Using the first resin film as the top and bottom adhesive films, coat it with epoxy resin containing a thixotropic agent to prepare the second resin film;

[0011] Step 3: The second resin film and reinforcing fiber are compounded at a preset temperature and pressure to prepare an epoxy resin prepreg.

[0012] Furthermore, the areal density of the first resin film is 8 g / m³. 2 ~20g / m 2 .

[0013] Furthermore, in step one, the temperature of the coating roller is 60℃~90℃.

[0014] Furthermore, the speed of the coating roller is 3m / min to 20m / min.

[0015] Furthermore, in step two, the temperature of the coating roller is 60℃~90℃.

[0016] Furthermore, the speed of the coating roller is 3m / min to 15m / min.

[0017] Furthermore, in step three, the temperature of the heating roller is 65℃~100℃.

[0018] Furthermore, the speed of the heating roller is 3m / min to 8m / min.

[0019] Furthermore, the reinforcing fiber is a fiber or a fiber fabric.

[0020] Furthermore, the reinforcing fiber includes any one of glass fiber, carbon fiber, and basalt fiber.

[0021] (3) Beneficial effects

[0022] In summary, this invention utilizes a two-step hot-melt process to prepare a pair of low-area-density first resin films using thixotropic epoxy resin. These first resin films are then used as the upper and lower release papers in a one-step prepreg preparation process. Thixotropic epoxy resin is placed in the resin tank of the one-step prepreg machine, ultimately producing an epoxy resin prepreg. During the prepreg process, because the release paper (i.e., the first resin film) in contact with the second resin film does not contain thixotropic agent, it is easily peeled off from the resin, ensuring that the final prepreg's resin content accuracy meets requirements. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic flowchart of a method for preparing an epoxy resin prepreg provided in an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the structure of a first resin film preparation device provided in an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the structure of an epoxy resin prepreg preparation device provided in an embodiment of the present invention.

[0027] In the picture:

[0028] 1-Film winding shaft; 2-Release film sending shaft; 3-Ice water machine; 4-Thickness gauge; 5-Adjusting roller; 6-Upper coating roller; 7-Lower coating roller; 8-Release paper sending shaft; 9-Wound shaft; 10-Discharge table; 11-PE film; 12-Glue roller; 13-Return paper winding; 14-Upper coating film; 15-Lower coating film; 16-Heated roller; 17-Ice roller; 18-Upper coating roller; 19-Lower coating roller; 20-PE film winding; 21-Reinforcing fiber. Detailed Implementation

[0029] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention by way of example, but should not be used to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments.

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0032] Figure 1This is a schematic flowchart of a method for preparing an epoxy resin prepreg according to an embodiment of the present invention, as shown below. Figure 1 As shown, the method may include the following steps:

[0033] S100. A first resin film with low areal density is prepared using epoxy resin without added thixotropic agent.

[0034] Specifically, the areal density of the first resin film is 8 g / m³. 2 ~20g / m 2 Utilizing, for example Figure 1 The equipment shown is used to prepare the first resin film in a resin film preparation process. The temperature of the coating roller is 60℃~90℃ and the speed of the coating roller is 3m / min~20m / min.

[0035] S200. The first resin film is used as the top and bottom adhesive films, and then coated with epoxy resin with added thixotropic agent to prepare the second resin film.

[0036] Specifically, the areal density in step 5 is 8 g / m³. 2 ~20g / m 2 The resin film serves as the upper and lower release paper for the one-step prepreg preparation in this step. This adhesive-coated release paper is coated with epoxy resin containing a thixotropic agent as it passes through the coating roller of the one-step prepreg machine. The weight of the resin coating in this step is calculated based on the required resin content and fiber areal density of the final prepreg. The temperature of the coating roller is 60℃~90℃, and the roller speed is 3m / min~15m / min.

[0037] S300: The second resin film and reinforcing fiber are compounded at a preset temperature and a preset pressure to prepare an epoxy resin prepreg.

[0038] Specifically, the temperature of the heating roller is 65℃~100℃, and the speed of the heating roller is 3m / min~8m / min. The reinforcing fiber includes any one of glass fiber, carbon fiber, and basalt fiber. Alternatively, it can be a fiber fabric, specifically a glass fiber fabric, carbon fiber fabric, or quartz fiber fabric.

[0039] Epoxy resin thixotropic agents are generally nano- or micron-sized powders. Adding thixotropic agents to epoxy resin disrupts its cohesive strength. In practical engineering, when using a two-step hot-melt process to prepare epoxy resin prepreg, the epoxy resin is first prepared into two layers using a hot-melt film-making machine, and then the prepreg is prepared using a prepreg machine. In this method, the presence of the thixotropic agent reduces the cohesive strength of the epoxy resin during the film preparation. During the second step of prepreg preparation, the epoxy resin in the film is difficult to peel off from the release paper, resulting in a certain amount of epoxy resin remaining on the release paper, affecting the accuracy of the prepreg resin content.

[0040] Example 1

[0041] The prepared fiber surface density is (220±7) g / m 2 A T300-grade fiber-reinforced high-temperature epoxy resin prepreg with a resin content of (38±3)% was prepared. Two portions of high-temperature epoxy resin with a curing temperature of 180℃ were prepared: the first portion was a high-temperature epoxy resin with added thixotropic agent, and the second portion was a high-temperature epoxy resin without added thixotropic agent. Using... Figure 2 The equipment described above (its specific structure and working principle will not be elaborated here as it is conventional) is used to prepare the first resin film, and a second batch of high-temperature epoxy resin without thixotropic agent is used to prepare a film with an areal density of 15 g / m³. 2 The first resin film was prepared by setting the coating roller temperature to 85℃ and the machine speed to 8m / min, producing two rolls in total. The prepared film (first resin film) was then used... Figure 3 The equipment used (since it is conventional, its specific structure and working principle will not be described in detail here) is used to prepare prepreg by coating it with epoxy resin containing a thixotropic agent. After this step, the areal density of the coated film is 66 g / m³. 2 The areal density of the lower adhesive film is 66 g / m³. 2 The coating roller temperature in this step is 85℃, and the machine speed is 5m / min. Continuing through the prepreg machine, after peeling off the release paper from the upper and lower adhesive films, the upper and lower adhesive films are laminated with the fiberglass cloth in the middle layer to prepare the prepreg. At this point, the lamination temperature is 95℃, and the machine speed is 5m / min.

[0042] Example 2

[0043] The prepared fiber has an areal density of 133 g / m³. 2 A T800 grade carbon fiber reinforced medium-temperature epoxy resin prepreg with a resin content of 33% was used. Two portions of medium-temperature epoxy resin with a curing temperature of 120℃ were prepared: the first portion was a medium-temperature epoxy resin with added thixotropic agent, and the second portion was a medium-temperature epoxy resin without added thixotropic agent. Using... Figure 2 The first resin film was prepared using the equipment described above (since this equipment is conventional, its specific structure and working principle will not be elaborated here). A second batch of medium-temperature epoxy resin without thixotropic agents was used to prepare a film with an areal density of 8 g / m³. 2 The first resin film was prepared by setting the coating roller temperature to 65℃ and the machine speed to 10m / min, producing two rolls in total. The prepared film (first resin film) was then used... Figure 3 The equipment used (its specific structure and working principle will not be detailed here as it is conventional) prepares prepreg by coating it with epoxy resin containing a thixotropic agent. After this step, the areal density of the adhesive film is 33 g / m³. 2 The areal density of the lower adhesive film is 32 g / m³. 2In this step, the coating roller temperature is 65℃ and the machine speed is 4m / min. Continuing through the prepreg machine, after the release paper of the upper and lower adhesive films is peeled off, the upper and lower adhesive films are combined with the carbon fiber of the middle layer to prepare the prepreg. At this time, the bonding temperature is 70℃ and the machine speed is 4m / min.

[0044] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0045] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art without departing from the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A method for preparing an epoxy resin prepreg, characterized in that, The method includes the following steps: Step 1: Prepare a first resin film with low areal density using epoxy resin without added thixotropic agent; Step 2: Use the first resin film as the upper and lower release paper, and coat it with epoxy resin with added thixotropic agent to prepare the second resin film; Step 3: The second resin film and reinforcing fiber are compounded at a preset temperature and pressure to prepare an epoxy resin prepreg.

2. The method for preparing epoxy resin prepreg according to claim 1, characterized in that, The areal density of the first resin film is 8 g / m³. 2 ~20g / m 2 .

3. The method for preparing epoxy resin prepreg according to claim 1, characterized in that, In step one, the temperature of the coating roller is 60℃~90℃.

4. The method for preparing epoxy resin prepreg according to claim 3, characterized in that, The speed of the coating roller is 3m / min to 20m / min.

5. The method for preparing epoxy resin prepreg according to claim 1, characterized in that, In step two, the temperature of the coating roller is 60℃~90℃.

6. The method for preparing epoxy resin prepreg according to claim 5, characterized in that, The speed of the coating roller is 3m / min to 15m / min.

7. The method for preparing epoxy resin prepreg according to claim 1, characterized in that, In step three, the temperature of the heating roller is 65℃~100℃.

8. The method for preparing epoxy resin prepreg according to claim 7, characterized in that, The speed of the heating roller is 3m / min to 8m / min.

9. The method for preparing epoxy resin prepreg according to claim 1, characterized in that, The reinforcing fiber is a fiber fabric.

10. The method for preparing epoxy resin prepreg according to claim 1, characterized in that, The reinforcing fiber includes any one of glass fiber, carbon fiber, and basalt fiber.

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