A method of continuous forming of thermoplastic composites

Abstract

The application discloses a kind of thermoplastic composite continuous forming methods.The system includes successively in the direction of material travel: multiple roll unwinding mechanism, flattening arrangement, continuous mould pressing device and double steel belt presser.Wherein, continuous mould pressing device is made of multiple independent presser module, for applying 5-15MPa high pressure to realize the sufficient impregnation of resin to fiber;Double steel belt presser follows immediately, for applying 1-3MPa low pressure to eliminate surface indentation generated in mould pressing process.The application is by high pressure impregnation and low pressure finishing function clear distinction and collaborative use, overcome the technical contradiction that impregnation quality and surface quality are difficult to obtain in prior art, both ensure the excellent internal impregnation quality of composite material, also obtain high surface flatness, realize the continuous production of high-quality thermoplastic composite plate.

Description

Technical Field

[0001] This invention relates to the field of composite material molding technology, specifically to a continuous molding method for thermoplastic composite materials, particularly a molding system and method that uses alternating layers of continuous fiber fabric and thermoplastic film, and achieves continuous production through the combined use of molding and double steel strips. Background Technology

[0002] Thermoplastic composite sheets are widely used in aerospace, rail transportation, automobile manufacturing, and building decoration due to their excellent properties such as lightweight, high strength, corrosion resistance, and recyclability. Currently, the main continuous molding methods for thermoplastic composite sheets include the double-strip continuous press method and the flat vulcanizing machine molding method.

[0003] The double steel belt continuous press method can achieve continuous production with high efficiency. However, due to the limitations of the steel belt structure, its working pressure is usually limited to below 3MPa, which is difficult to meet the requirements of high viscosity thermoplastic resin for sufficient impregnation of fibers. This results in defects such as dry spots and bubbles inside the composite material, which seriously affects the mechanical properties of the sheet.

[0004] Flat vulcanizing molding can achieve quasi-continuous production by using multiple presses working alternately, applying high pressure of 5-15 MPa to ensure sufficient resin impregnation of fibers. However, because this process uses multiple independent press modules to press alternately, obvious indentations or overlap marks will form at the edges of the pressing area of ​​each press module, which seriously affects the flatness of the sheet surface and requires subsequent processing such as grinding.

[0005] In summary, a technical contradiction exists in the existing technology: processes that can apply high pressure to ensure impregnation quality (flat vulcanizing machine molding method) cannot achieve good surface quality; while processes that can achieve good surface quality (double steel belt continuous press method) cannot apply high pressure to ensure impregnation quality. This contradiction has long existed in the field and has not yet been effectively resolved. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a continuous molding method for thermoplastic composite materials. This system organically combines a modular continuous molding device with a double-strand press, ensuring sufficient impregnation of the fiber fabric and thermoplastic film while eliminating surface indentations generated during the molding process, thus achieving continuous production of high-quality thermoplastic composite sheet materials.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A continuous molding method for thermoplastic composite materials, characterized in that the following components are arranged sequentially along the material travel direction: The multi-roll unwinding mechanism includes several continuous fiber fabric unwinding rollers and several thermoplastic film unwinding rollers, used to synchronously unwind according to a preset layup sequence (such as fabric / film alternation) to form a multi-layer stacked structure; The flattening and finishing mechanism, located after the unwinding mechanism, includes multiple flattening devices for flattening and finishing the multi-layered structure and eliminating wrinkles; The continuous molding unit, located after the flattening and finishing mechanism, comprises multiple independent press modules arranged sequentially along the material conveying direction. Each press module includes a heating section and a cooling section for applying high pressure of 5-15 MPa. Under heating conditions, the thermoplastic film is melted and fully impregnated with the continuous fiber fabric, followed by cooling and shaping under pressure. The core function of this step is to achieve thorough impregnation, but surface indentations are unavoidable.

[0008] A double-strand press, located after the continuous molding unit, is used to receive the molded sheet metal. This press applies a low pressure of 1-3 MPa to continuously level and finish the upper and lower surfaces of the sheet metal, eliminating surface indentations generated during the molding process. This pressure is insufficient for impregnation, but sufficient to level the surface.

[0009] The trimming and winding mechanism, located after the double steel strip press, is used to trim the edges of the trimmed sheet material and then wind it up or cut it to a fixed length.

[0010] Preferably, there is a gap between adjacent independent press modules in the continuous molding device, and the material is in a pressureless state at the gap. This area is the main cause of indentation.

[0011] Preferably, the operating speed of the double steel belt press is matched with the material conveying speed of the continuous molding device, and the speed difference does not exceed ±5%, so as to ensure that the sheet material is neither stretched nor piled up in the double steel belt press.

[0012] The present invention also provides a method for preparing thermoplastic composite material sheets using the above-described system.

[0013] The beneficial effects of this invention are as follows: Excellent impregnation quality: High pressure of 5-15MPa is applied by a modular continuous molding device to ensure that the high viscosity thermoplastic resin is fully impregnated on the fiber fabric. The composite material is free of defects such as dry spots and bubbles, and has excellent mechanical properties.

[0014] High surface flatness: The molded sheet is finished by a double steel belt press, which completely eliminates the indentations caused by the junction of the independent press modules, achieving a mirror finish without the need for subsequent polishing.

[0015] Synergistic effect beyond simple superposition: The technical effect of this invention is not a simple superposition of the effects of the molding device and the double steel belt press, but rather a synergistic effect of 1+1>2. By clearly distinguishing between the two functional units of "impregnation" and "trimming," this invention allows each to operate within its most suitable pressure range, thereby simultaneously achieving high impregnation quality and high surface smoothness that cannot be achieved by a single device.

[0016] Highly adaptable to different processes: Process parameters such as temperature, pressure, and speed can be adjusted according to different thermoplastic matrix materials, making it applicable to a wide range of applications.

[0017] It has a wide range of applications. Attached Figure Description

[0018] Figure 1 This is a production diagram. Multi-roll unwinding mechanism (1); continuous fiber fabric unwinding roll (1-1); thermoplastic film unwinding roll (1-2); flattening and finishing mechanism (2); collection roll mechanism (3); continuous molding device (4); hot pressing module (4-1); cold pressing module (4-2); double steel strip press (5); double steel strip hot pressing mechanism (5-1); double steel strip cold pressing mechanism (5-2); trimming / cutting mechanism (6); sheet material (7). Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this does not constitute a limitation on the scope of protection of the present invention. A comparative experiment was specifically designed to demonstrate the synergistic effect of the present invention.

[0020] like Figure 1 As shown, the system of the present invention includes, in sequence along the material travel direction: a multi-roll unwinding mechanism 1, a flattening and finishing mechanism 2, a continuous molding device 4, a double steel strip press 5, and a trimming / cutting mechanism 6. Example 1:

[0021] This embodiment provides a method for preparing a continuous glass fiber fabric reinforced polypropylene composite board, as detailed below: Raw material preparation: continuous glass fiber fabric, surface density 100g / m²; polypropylene film, thickness 0.1mm.

[0022] Process flow: a) The multi-roll unwinding mechanism 1 is equipped with two glass fiber fabric unwinding rollers and one polypropylene film unwinding roller, which are synchronously unwound in an alternating sequence of fabric / film / fabric / film to form a total of three-layer stacked structure.

[0023] b) The stacked structure is passed through the flattening mechanism 2 in sequence through three sets of flattening rollers with fine textured surfaces to ensure that each layer is flat.

[0024] c) The flattened laminated structure is fed into the continuous molding device 4. This device includes an independent press module, five hot pressing modules, and one cold pressing module. Each module has a pressing area of ​​600mm × 600mm. The heating section temperature is set to 200℃, the pressure to 10MPa, and the settling time to 60 seconds; the cooling section temperature is set to 40℃, and the pressure to 10MPa. The material continuously passes through each press module at a speed of 0.5 m / min to obtain a sheet with surface indentations. A slide rail (not shown in the figure) is installed below the continuous molding device 4. During pressurization, the slide rail moves with the material, moves to the set position, and then returns to the original position to ensure continuous material flow. d) Feed the molded sheet into the double steel belt press 5 at a speed of 0.5 m / min (matching the speed of the molding device). The surface temperature of the double steel belt hot pressing mechanism is 200℃ and the pressure is 2MPa. The surface temperature of the double steel belt cold pressing mechanism is 40℃ and the pressure is 2MPa. The sheet is then leveled and trimmed to eliminate surface indentations.

[0025] e) The trimmed board is then trimmed at the edges by the trimming / cutting mechanism 6 and rolled into a continuous roll or a board of a certain size.

[0026] The technical effect of this invention is not a simple superposition of the effects of the molding device and the double steel belt press, but rather produces a significant synergistic effect: the molding device ensures the impregnation quality, and the double steel belt press eliminates the resulting indentations. Together, they achieve comprehensive performance that cannot be achieved by a single process.

[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A continuous molding method for thermoplastic composite materials, characterized in that, Along the material travel direction, there are arranged a multi-roll unwinding mechanism (1), including several continuous fiber fabric unwinding rollers (1-1) and several thermoplastic film unwinding rollers (1-2), which are used to synchronously unwind according to the preset layup sequence to form a multi-layer stacked structure; The flattening and finishing mechanism (2) is located after the unwinding mechanism and includes multiple flattening devices for flattening and finishing the multi-layer stacked structure; after flattening, the material passes through the collecting roller mechanism (3) together. The continuous molding device (4) is located after the collecting roller mechanism (3) and includes multiple independent press modules arranged sequentially along the material conveying direction, including a hot pressing module (4-1) and a cold pressing module (4-2). Each press module is used to apply a pressure of 5-15 MPa. The thermoplastic film is heated under the hot pressing module (4-1) to melt and impregnate the continuous fiber fabric, and then cooled and shaped under the pressure of the cold pressing module (4-2). A slide rail (not shown in the figure) is installed below the continuous molding device (4). When pressurized, it moves with the material, moves to the set position, and then returns to the original position to ensure the continuous operation of the material. The double steel belt press (5) is set after the continuous molding device and is used to receive the molded and shaped sheet metal. It is divided into a hot pressing mechanism (5-1) and a cold pressing mechanism (5-2). It can apply a pressure of 1-3MPa to continuously flatten and trim the upper and lower surfaces of the sheet metal to eliminate the surface indentations generated during the molding process. The trimming and winding mechanism (6) is located after the double steel strip press and is used to trim and wind or cut the edges of the trimmed sheet material.

2. The continuous molding method for thermoplastic composite materials according to claim 1, characterized in that, In the continuous molding device, there is a gap between adjacent independent press modules, and the material is in a pressureless state at the gap.

3. The continuous molding method for thermoplastic composite materials according to claim 1, characterized in that, The continuous molding device (4) includes a separate hot pressing module (4-1) and a cold pressing module (4-2).

4. The continuous molding method for thermoplastic composite materials according to claim 1, characterized in that, The operating speed of the double steel belt press (5) is matched with the material conveying speed of the continuous molding device (4), and the speed difference does not exceed ±5%.

5. A method for preparing thermoplastic composite material sheets according to any one of claims 1 to 4, characterized in that, Includes the following steps: a) By using a multi-roll unwinding mechanism, continuous fiber fabric and thermoplastic film are simultaneously unwound in an alternating sequence to form a multi-layered structure; b) The multi-layered structure obtained in step a is flattened and shaped using a flattening and sizing mechanism; c) The multi-layered structure processed in step b is fed into a continuous molding device and subjected to heating, pressurizing, impregnation, and cooling shaping under high pressure of 5-15 MPa to obtain a sheet material with surface indentations. d) The sheet material molded in step c is fed into a double steel belt press at a matching speed and continuously leveled and trimmed under a pressure of 1-3MPa to eliminate surface indentations. e) Trim and roll or cut the sheet material after step d.

6. The method according to claim 5, characterized in that, The continuous fiber fabric mentioned in step a is one of continuous glass fiber fabric, continuous carbon fiber fabric, or continuous aramid fiber fabric, with an areal density of 50-1000 g / m²; the thermoplastic film is selected from one or more combinations of polypropylene film, polyethylene film, nylon film, polyethylene terephthalate film, and polycarbonate film, with a film thickness of 0.05-0.25 mm.

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