A continuous mixing and molding system and molded product made therefrom

Abstract

The invention discloses a continuous mixing and compression molding system, comprising a twin-screw extruder and a compression molding device, the compression molding device comprising a lower fixed mold and an upper movable mold, the bottom surface of the upper movable mold is provided with an upper mold cavity, the top surface of the lower fixed mold is provided with an injection molding cavity, a melt continuous conveying mechanism is provided in the lower mold seat, the melt continuous conveying mechanism comprises a melt conveying pipeline and a feed valve, the outlet of the twin-screw extruder is connected with the inlet of the melt conveying pipeline, the feed valve comprises a valve body and a valve stem, the valve body is fixed in the lower mold seat, a feed port is provided on the outer surface of the valve body, a discharge port is provided on the top of the valve body, the discharge port is communicated with the injection molding cavity, the melt conveying pipeline is communicated with the feed port on the valve body, the valve stem is located in the valve body, the gap between the valve stem and the valve body constitutes a melt conveying channel, a valve plug is provided at the upper end of the valve stem, and the lower end of the valve stem passes through the valve body and is connected to a driving mechanism A. The invention is suitable for online compression molding of thermoplastic resin systems with high melting points and fast crystallization rates, can mold complex structural parts and ensure the integrity of molded products.

Description

Technical Field

[0001] The invention relates to the technical field of plastic molding processing, in particular to a continuous mixing and molding system and a molded product manufactured by the system. Background Art

[0002] LFT-D technology is an online direct compression molding technology for thermoplastic composite materials with thermoplastic resin as the matrix and long fiber as the reinforcement material. It is very suitable for the production of structural and semi-structural automotive parts and will become an indispensable force in the automotive lightweight industry.

[0003] LFT-D technology realizes the direct online production mode of raw materials, greatly reduces the cost of the final product, avoids the high procurement and related logistics and warehousing costs of semi-finished products, uses the residual temperature of plasticized materials for immediate molding, eliminates the energy loss caused by the secondary heating of semi-finished sheets, and the production process is fully controlled by the program, and the production line runs automatically, which significantly reduces the overall energy consumption. However, LFT-D technology is currently only promoted and used in developed countries such as Europe and the United States, and the technology of domestic LFT-D online molding equipment is not mature. There are only more than 10 existing LFT-D production lines and equipment, and most of them are imported from abroad. The most advanced is the LFT-D fully automatic molding production line of Dieffenbacher Company of Germany introduced by Shanghai Yaohua Dazhong New Materials Company. Fujian Haiyuan Automation Machinery Co., Ltd. successfully developed my country's first LFT-D production line in April 2012, filling the gap in my country's LFT-D production line equipment.

[0004] However, whether it is imported from abroad or independently developed by China, the applicable resin matrix of LFT-D production line equipment is mainly PP. It is not applicable to resin matrices with high melting points and fast cold crystallization rates such as nylon. The main reason is that the current LFT-D technology adopts the following process: first, the resin matrix and functional additives such as reinforcing fibers are processed into molten composite material embryos, and then the material embryos are cut into blocks according to the size of the molded parts by a cutting machine, and then the cut blocks are placed on the surface of the mold cavity of the molding device by a manipulator for molding. This process requires the material embryos to be prepared in advance and placed on the conveyor belt waiting for the manipulator to grab and send them into the mold cavity. During the waiting stage and before being grabbed by the manipulator and entering the mold cavity, the material embryos need to be exposed to the air for a period of time. During this period of time, a considerable part of the temperature of the material embryos will be lost. For thermoplastic resin melts with high melting points and fast cold crystallization rates, crystallization has begun before they are sent to the mold cavity. Even more, after the melt enters the mold cavity, it has cooled and solidified into blocks before it can completely fill the mold cavity, resulting in the inability to mold the desired product. Furthermore, when the molten thermoplastic resin is exposed to the air, there is a risk that the overall performance of the molded product will be affected by oxidation. Most automotive plastic parts, especially structural parts, are molded with nylon substrates. Nylon is the most important engineering plastic for the automotive industry, which is why LFT-D production line equipment has not been widely used by domestic automotive plastic manufacturers.

[0005] In addition, the current LFT-D production line equipment usually adds a heat preservation device in the material preparation section to ensure that the blank does not solidify prematurely, which results in high energy consumption in production and processing. At the same time, because the blank is directly placed on the surface of the mold cavity, only flat products with simple structures can be formed. For products with complex structures, the blank melt cannot flow evenly through various parts of the mold cavity, or cannot completely fill various parts of the mold cavity, resulting in missing parts or incomplete defects in the molded products. Summary of the invention

[0006] The present invention aims to solve the above-mentioned technical problems existing in the existing LFT-D online compression molding equipment, and provides a continuous mixing and compression molding system, which can realize the online compression molding of thermoplastic resin systems with high melting points and fast crystallization rates, is suitable for the molding of products with complex structures, and is conducive to reducing energy consumption and production costs.

[0007] Another object of the present invention is to provide a plastic molded product manufactured using the above-mentioned continuous mixing and molding system.

[0008] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a continuous mixing and molding system, comprising a twin-screw extruder and a molding device, the molding device comprising a lower fixed mold and an upper movable mold that can move up and down relative to the lower fixed mold, the upper top surface of the upper movable mold is fixedly connected to an upper mold base, the bottom surface of the upper movable mold is provided with an upper mold cavity, the top surface of the lower fixed mold is provided with an injection cavity, the bottom surface of the lower fixed mold is fixedly connected to a lower mold base, a melt continuous conveying mechanism is provided in the lower mold base, the melt continuous conveying mechanism comprises a melt conveying pipeline and a feed valve, the outlet of the twin-screw extruder is connected to the melt The inlet of the conveying pipeline is connected, the feed valve includes a valve body and a valve stem, the valve body is fixed in the lower mold base, a feed port is provided on the outer side surface of the valve body, a discharge port is provided on the top of the valve body, the discharge port is located at the bottom of the injection cavity and is connected with the injection cavity, the melt conveying pipeline is connected with the feed port on the valve body, the valve stem is located in the valve body, the gap between the valve stem and the valve body constitutes a melt conveying channel, a valve plug for controlling the opening and closing of the discharge port is provided at the upper end of the valve stem, the lower end of the valve stem passes through the valve body and the valve stem and the valve body are sealed and slidably matched, and the lower end of the valve stem is connected to a driving mechanism A that can make the valve stem move linearly up and down.

[0009] The present invention connects the compression molding device with the twin-screw extruder through a melt continuous conveying mechanism. After the resin matrix and various functional additives are mixed and plasticized by the twin-screw extruder to form a raw material melt, the melt is conveyed to the feed valve through a melt conveying pipeline, and then conveyed to the injection cavity of the compression molding device through the feed valve for compression molding. This not only realizes continuous online production and improves production efficiency, but also avoids the melt from being exposed to the air. There is no need to worry about the quality of subsequent compression molded products being affected by premature condensation of the melt, and solves the problem that the current LFT-D production line equipment is not suitable for online compression molding of thermoplastics with high melting points and fast crystallization rates. The melt conveying channel can be of various shapes as long as it can realize the conveying of the plastic melt to the feed valve. Cooling water is passed through the upper fixed mold and the lower fixed mold to cool the molded product. This is common knowledge in the field, so the specific structure is not shown in the drawings of the specification. The discharge port at the top of the valve body is located at the bottom of the injection cavity and is connected to the injection cavity. The invention can realize the injection feeding at the bottom of the injection cavity, and the material embryo melt can fully flow through all parts of the mold cavity and completely fill the mold cavity, thereby ensuring the integrity of the molded product, so that the present invention can be used to produce products with complex structures, and broaden the application scope of online compression molding; in addition, compared with traditional intermittent compression molding, the polymer only needs one heating process, which not only significantly reduces energy consumption, but also further ensures the comprehensive performance of the molded product; compared with the existing online compression molding production line, the insulation device of the material preparation section, the cutting machine for preparing the material embryo and the manipulator for taking the material embryo are omitted, and the manufacturing cost is lower, which can reduce a large amount of equipment investment cost for automobile plastic parts manufacturers, and is more conducive to the promotion and use of domestic LFT-D production line equipment, and improves the domestic automobile plastic parts manufacturing efficiency and product quality; it is common knowledge in the field that the upper movable mold can move up and down relative to the lower fixed mold, and there is no technical obstacle to its realization for those skilled in the art, so it is not described in detail; the lower mold base is fixed on the mold frame.

[0010] Preferably, the compression molding device further comprises an ejection mechanism, the ejection mechanism comprises an upper template and a lower pressure plate, the upper template is fixed above the upper mold base, a gap is left between the upper template and the upper mold base, the gap forms an installation cavity, the lower pressure plate is located in the installation cavity, a driving mechanism B is provided on the lower pressure plate that can make the lower pressure plate produce up and down linear motion, an ejector fixing plate is fixed to the bottom surface of the lower pressure plate, an ejector that passes through the upper mold base and the upper movable mold is provided on the bottom surface of the ejector fixing plate, and the free end of the ejector can extend into the upper cavity. The ejection mechanism of the present invention is arranged above the upper mold base of the compression molding device to enable the molded product to be demolded smoothly; the lower pressure plate can make up and down linear motion under the drive of the driving mechanism B, so that the ejector extends into the upper cavity of the upper movable mold to eject the molded product; the driving mechanism B can be a variety of driving mechanisms such as a cylinder and an oil cylinder, as long as the lower pressure plate can achieve up and down linear motion.

[0011] Preferably, pads are fixed on the left and right sides of the top surface of the upper die seat, the upper die plate is fixed on the pads, and the space between the upper die plate, the upper die seat and the pads forms an installation cavity.

[0012] Preferably, guide pillars are provided at the four corners of the bottom surface of the ejector fixing plate, the upper ends of the guide pillars are fixedly connected to the ejector fixing plate, the lower ends of the guide pillars pass through the upper die seat and are slidably matched with the upper die seat, and the portion of the guide pillars located between the upper die seat and the ejector fixing plate is sleeved with springs. The guide pillars ensure the running stability of the ejector fixing plate, thereby ensuring that the ejector moves linearly up and down without deviation.

[0013] Preferably, the driving mechanism B is an oil cylinder, the cylinder body of the oil cylinder is fixedly connected to the lower pressure plate, and the piston rod of the oil cylinder is fixedly connected to the upper template.

[0014] Preferably, the lower die base is a box structure, a transverse mounting plate is provided in the lower die base, the melt delivery pipeline is fixed to the top surface of the mounting plate, an avoidance hole is provided on the mounting plate, the lower end of the valve stem passes through the avoidance hole and is fixed with a lifting block, the diameter of the avoidance hole is larger than the maximum width of the lifting block, the driving mechanism A is a cylinder located below the mounting plate and fixedly connected to the lower die base, and the piston rod of the cylinder is fixedly connected to the lifting block.

[0015] Preferably, the discharge port is configured as a flared structure, and the outer contour of the valve plug is adapted to the discharge port.

[0016] Therefore, the present invention has the following beneficial effects:

[0017] (1) The use of a continuous melt conveying mechanism for feeding not only realizes continuous online production and improves production efficiency, but also avoids the exposure of the melt to the air. There is no need to worry about the quality of subsequent molded products being affected by premature condensation of the melt. This solves the problem that the current LFT-D production line equipment is not suitable for online compression molding of thermoplastics with high melting points and fast crystallization rates. It can realize online compression molding of thermoplastic resin systems with high melting points and fast crystallization rates;

[0018] (2) The melt continuous conveying mechanism is used for feeding. Compared with the existing LFT-D production line equipment, the insulation device in the material preparation section, the cutting machine for the material blank and the manipulator for taking the material blank are omitted, which can greatly reduce energy consumption and manufacturing costs, and is conducive to the promotion and use of LFT-D production line equipment;

[0019] (3) The outlet at the top of the valve body is located at the bottom of the injection cavity and is connected to the injection cavity, so that the injection molding and feeding at the bottom of the injection cavity can be realized. The molten material can fully flow through all parts of the mold cavity and completely fill the mold cavity, ensuring the integrity of the molded product. It can be used for the molding of products with complex structures, broadening the application field of compression molding. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is an overall structural connection diagram of the present invention.

[0021] Figure 2 yes Figure 1 A right side view of the middle compression molding device.

[0022] Figure 3 yes Figure 1 A connection diagram of the upper template, lower pressure plate, ejector fixing plate and ejector.

[0023] Figure 4 yes Figure 1 A schematic diagram of the connection between the middle and lower fixed molds, the lower mold base and the melt delivery pipeline.

[0024] Figure 5 It is a structural schematic diagram of the melt continuous conveying mechanism in the present invention.

[0025] Figure 6 yes Figure 5 A structural diagram of the medium feed valve.

[0026] Figure 7 yes Figure 6 Cross-sectional view along AA direction.

[0027] In the figure: upper movable mold 1, lower fixed mold 2, upper mold base 3, injection cavity 4, lower mold base 5, melt delivery pipeline 6, valve body 7, valve stem 8, feed port 9, discharge port 10, melt delivery channel 11, valve plug 12, upper mold plate 13, lower pressure plate 14, mounting cavity 15, ejector fixing plate 16, ejector 17, guide column 18, spring 19, oil cylinder 20, air cylinder 21, mounting plate 22, lifting block 23, avoidance hole 24, twin-screw extruder 25, cushion block 26. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0029] like Figure 1 , Figure 2A continuous mixing and compression molding system shown in the figure comprises a twin-screw extruder 25 and a compression molding device, the compression molding device comprises a lower fixed mold 2, an upper movable mold 1 which can move up and down relative to the lower fixed mold, and an ejection mechanism, the upper top surface of the upper movable mold is fixedly connected to an upper mold base 3, the bottom surface of the upper movable mold is provided with an upper cavity, the ejection mechanism comprises an upper mold plate 13 and a lower pressing plate 14, pads 26 are fixed to the left and right sides of the top surface of the upper mold base, the upper mold plate is fixed on the pads, the space between the upper mold plate, the upper mold base and the pads forms an installation cavity 15, the lower pressing plate is located in the installation cavity, two symmetrically arranged oil cylinders 20 which can make the lower pressing plate move up and down linearly are connected to the lower pressing plate, the cylinder body of the oil cylinder is fixedly connected to the lower pressing plate, the piston rod of the oil cylinder is fixedly connected to the upper mold plate, the bottom surface of the lower pressing plate is fixed with an ejector fixing plate 16, and the bottom surface of the ejector fixing plate is fixed with an ejector 17 (such as Figure 3 As shown in the figure, the free end of the ejector pin can extend into the upper cavity, and guide pillars 18 are provided at the four corners of the bottom surface of the ejector fixing plate. The upper end of the guide pillar is fixedly connected to the ejector fixing plate, and the lower end of the guide pillar passes through the upper mold base and slides with the upper mold base. The part of the guide pillar located between the upper mold base and the ejector fixing plate is sleeved with a spring 19; the top surface of the lower fixed mold is provided with an injection cavity 4 (as shown in the figure) that matches the upper cavity. Figure 4 As shown, the bottom surface of the lower fixed mold is fixedly connected to a lower mold base 5, the lower mold base is a box structure, a transverse mounting plate 22 is fixed inside the lower mold base, and the melt continuous conveying mechanism includes a melt conveying pipeline 6 (as shown Figure 5 As shown) and a feed valve, the melt delivery pipeline is fixed to the top surface of the mounting plate, the outlet of the twin-screw extruder is connected to the inlet of the melt delivery pipeline through a pipeline, and the feed valve includes a valve body 7 and a valve stem 8 (as shown Figure 6 , 7 As shown), a feed port 9 is provided on the outer side surface of the valve body, a discharge port 10 is provided on the top of the valve body, and the discharge port is set as a flaring structure. The valve body passes through the melt conveying pipeline and is fixedly connected to the melt conveying pipeline. The upper end of the valve body is fixedly connected to the lower fixed mold. The discharge port is located at the bottom of the injection cavity and is connected to the injection cavity. The valve stem is located in the valve body, and the gap between the valve stem and the valve body constitutes a melt conveying channel 11. A valve plug 12 for controlling the opening and closing of the discharge port is provided at the upper end of the valve stem. The outer contour of the valve plug is adapted to the discharge port. The lower end of the valve stem passes through the valve body and the valve stem and the valve body are sealed and slidably matched. An avoidance hole 24 is provided on the mounting plate. The lower end of the valve stem passes through the avoidance hole and is fixed with a lifting block 23 (circular block). The diameter of the avoidance hole is larger than the maximum width of the lifting block. A cylinder 21 is fixed on the lower mold base below the mounting plate, and the piston rod of the cylinder is fixedly connected to the lifting block.

[0030] The operation process of the present invention is as follows: the resin matrix and various functional additives are thrown into the twin-screw extruder for mixing and plasticizing, and then the melt continuously enters the melt conveying pipeline and the melt conveying channel from the inlet of the melt conveying pipeline, the piston rod of the cylinder extends to lift the valve stem and the valve plug, the discharge port is opened, and the melt to be formed is injected into the injection cavity. When the melt in the injection cavity reaches a certain amount, the piston rod of the cylinder contracts to retract the valve stem and the valve plug, the discharge port is closed, and the upper movable mold is pressed down to start molding. After the molding is completed, the upper movable mold is lifted to pull the molded product out of the injection cavity. At this time, the piston rod of the oil cylinder extends, driving the cylinder body of the oil cylinder in the opposite direction so that the lower pressure plate moves downward, and the molded product is ejected from the upper cavity in the upper movable mold through the ejector pin. At this time, a complete injection molding process is completed.

[0031] The above-described embodiment is only a preferred solution of the present invention and does not limit the present invention in any form. There are other variations and modifications without exceeding the technical solution described in the claims.

Claims

1. A continuous mixing and molding system, comprising a twin-screw extruder (25) and a molding device, characterized in that: The compression molding device comprises a lower fixed mold (2) and an upper movable mold (1) which can move up and down relative to the lower fixed mold, the upper top surface of the upper movable mold is fixedly connected to an upper mold base (3), the bottom surface of the upper movable mold is provided with an upper cavity, the top surface of the lower fixed mold is provided with an injection cavity (4), the bottom surface of the lower fixed mold is fixedly connected to a lower mold base (5), a melt continuous conveying mechanism is provided in the lower mold base, the melt continuous conveying mechanism comprises a melt conveying pipeline (6) and a feed valve, the outlet of the twin-screw extruder is connected to the inlet of the melt conveying pipeline, the feed valve comprises a valve body (7) and a valve stem (8), the valve body is fixed in the lower mold base, a feed port (9) is provided on the outer side surface of the valve body, a discharge port (10) is provided on the top of the valve body, the discharge port is located at the bottom of the injection cavity and is connected to the injection cavity, the discharge port is set as a flaring structure, the melt conveying pipeline is connected to the feed port on the valve body, the valve stem is located in the valve body, The gap between the valve stem and the valve body constitutes a melt conveying channel (11), and a valve plug (12) for controlling the opening and closing of the discharge port is provided at the upper end of the valve stem, the outer contour of the valve plug is adapted to the discharge port, the lower end of the valve stem passes through the valve body and the valve stem and the valve body are sealed and slidably matched, and the lower end of the valve stem is connected to a driving mechanism A capable of causing the valve stem to move linearly up and down; the compression molding device also includes an ejection mechanism, the ejection mechanism includes an upper mold plate (13) and a lower pressure plate (14), the upper mold plate is fixed above the upper mold base, a gap is left between the upper mold plate and the upper mold base, the gap forms an installation cavity (15), the lower pressure plate is located in the installation cavity, and a driving mechanism B capable of causing the lower pressure plate to move linearly up and down is provided on the lower pressure plate, and an ejector fixing plate (16) is fixed on the bottom surface of the lower pressure plate, and an ejector (17) passing through the upper mold base and the upper movable mold is provided on the bottom surface of the ejector fixing plate, and the free end of the ejector can extend into the upper cavity.

2. A continuous mixing and molding system according to claim 1, characterized in that: Cushion blocks (26) are fixed on the left and right sides of the top surface of the upper die seat, the upper die plate is fixed on the cushion blocks, and the space between the upper die plate, the upper die seat and the cushion blocks forms a mounting cavity.

3. A continuous mixing and molding system according to claim 1 or 2, characterized in that: Guide pillars (18) are provided at the four corners of the bottom surface of the ejector fixing plate. The upper ends of the guide pillars are fixedly connected to the ejector fixing plate. The lower ends of the guide pillars pass through the upper die seat and are slidably fitted between the upper die seat. The portion of the guide pillars located between the upper die seat and the ejector fixing plate is sleeved with a spring (19).

4. A continuous mixing and molding system according to claim 1, characterized in that: The driving mechanism B is an oil cylinder (20), the cylinder body of the oil cylinder is fixedly connected to the lower pressing plate, and the piston rod of the oil cylinder is fixedly connected to the upper template.

5. The continuous mixing and molding system according to claim 1, characterized in that: The lower die base is a box structure, a transverse mounting plate (22) is provided inside the lower die base, the melt delivery pipeline is fixed to the top surface of the mounting plate, an avoidance hole (24) is provided on the mounting plate, the lower end of the valve stem passes through the avoidance hole and is fixed with a lifting block (23), and the diameter of the avoidance hole is greater than the maximum width of the lifting block.

6. A continuous mixing and molding system according to claim 5, characterized in that: The driving mechanism A is a cylinder (21) located below the mounting plate and fixedly connected to the lower die base, and a piston rod of the cylinder is fixedly connected to the lifting block.

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