Composite polypropylene injection molding device

Abstract

The present invention relates to the field of injection molding technology, and discloses a composite polypropylene injection molding device, including a pressure-holding component, a mold component and an extrusion component; the pressure-holding component includes a pressure-holding shell with a pressure-holding cavity, and a pressure relief mechanism is arranged on the pressure-holding shell; the mold component includes an upper mold and a lower mold, the upper mold, the lower mold and a blocking mechanism, a model cavity is formed between the upper mold and the lower mold, the upper mold is provided with an exhaust hole communicating with the model cavity, and the blocking mechanism is used to connect the exhaust hole with the pressure-holding cavity when the air pressure in the model cavity reaches a threshold; the extrusion component is used to squeeze the injection molding material into the model cavity in a quantitative and stable manner; and also includes an air supply component whose output end is connected with the pressure-holding cavity, and the air supply component is used to deliver positive pressure gas into the pressure-holding cavity. The composite polypropylene injection molding device can assist the gas in the injection molding material to escape when the fluidity of the injection molding material is slow, so as to avoid bubbles inside the product and thus form surface defects.

Description

Technical Field

[0001] The invention relates to the technical field of injection molding, in particular to a composite polypropylene injection molding device. Background Art

[0002] Injection molding machines are the main molding equipment that uses plastic molding molds to make plastic products of various shapes from thermoplastics or thermosetting plastics. They are divided into vertical, horizontal, and all-electric types. The injection molding machine can heat the plastic and apply high pressure to the molten plastic to make it eject and fill the mold cavity. Injection molded parts refer to the various injection molded products produced by the injection molding machine, collectively known as injection molded parts, including various packaging, parts, etc. Among them, composite polypropylene materials are more widely used in injection molded products. Protective shell products can be produced through injection molding, which have good light transmittance and impact resistance.

[0003] Before the injection molding of composite polypropylene materials, particulate fillers (such as glass fiber and mineral fillers) can be added to improve the rigidity and strength of the injection molding material, and anti-cold agents can be added to enhance the toughness of the material in low-temperature environments. However, these modified materials usually lead to poor fluidity in the molten state, and the injection speed of the injection molding material into the mold cavity is slow. Traditional injection molding devices rely on simple exhaust grooves and exhaust holes, which are difficult to exhaust efficiently at low flow rates. Especially after the addition of modifiers, the fluidity of the injection molding material decreases, making it more difficult for the gas in the injection molding material to escape, which can easily lead to an increase in bubbles inside the product, significant surface defects, and even the formation of a layered structure. Such internal defects are very unfavorable for outdoor equipment casings with high performance requirements, especially in applications requiring high stability and resistance to mechanical shock, which will significantly reduce reliability.

[0004] Therefore, the existing injection molding device still has the problem that when the fluidity of the injection molding material decreases, it is not easy to assist the escape of gas in the injection molding material, which easily leads to an increase in bubbles inside the product and significant surface defects. Summary of the Invention

[0005] The purpose of the present invention is to provide a composite polypropylene injection molding device, which can assist the escape of gas in the injection molding material when the fluidity of the injection molding material is slow, thereby avoiding bubbles in the product and thus forming surface defects.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0007] Design a composite polypropylene injection molding device, including a pressure holding component, a mold component and an extrusion component;

[0008] The pressure-maintaining assembly includes a pressure-maintaining shell with a pressure-maintaining cavity, and the pressure-maintaining shell is provided with a pressure relief mechanism;

[0009] The mold assembly includes an upper mold and a lower mold, the upper mold, the lower mold and a blocking mechanism, a mold cavity is formed between the upper mold and the lower mold, the upper mold is provided with an exhaust hole communicating with the mold cavity, and the blocking mechanism is used to connect the exhaust hole with the pressure holding cavity when the air pressure in the mold cavity reaches a threshold;

[0010] The extrusion assembly is used to extrude the injection molding material into the mold cavity in a quantitative and stable manner;

[0011] It also includes an air supply component whose output end is connected to the pressure-maintaining chamber, and the air supply component is used to deliver positive pressure gas into the pressure-maintaining chamber.

[0012] Optionally, the pressure relief mechanism includes a pressure relief valve and a pressure relief port, the pressure relief valve is arranged in the pressure relief port, the pressure relief port is opened on the pressure maintaining shell and communicates with the pressure maintaining chamber, and the pressure relief valve is used to connect the pressure maintaining chamber with the outside world when the blocking mechanism connects the exhaust hole with the pressure maintaining chamber.

[0013] Optionally, the blocking mechanism includes a blocking disk, a blocking hole and a blocking portion, the blocking disk is rotatably connected in the upper mold, the blocking holes are circumferentially distributed on the surface of the blocking disk along the axis of the blocking disk, the blocking portion is correspondingly arranged in the blocking hole, and the size of the blocking hole matches the exhaust hole.

[0014] Optionally, the blocking portion includes a blocking block, an extrusion spring and a connecting hole opened on the inner wall of the blocking hole, the blocking block is slidably connected in the blocking hole, one end of the extrusion spring abuts the blocking hole, and the other end abuts the blocking block.

[0015] Optionally, a trigger mechanism is further included, which includes a reed switch, which is arranged in the upper mold. The material of the blocking block is at least partially magnet. When the blocking block slides to the middle part between the two ends of the connecting hole, the reed switch receives the magnetism of the blocking block and operates. The reed switch is connected in series in the circuit of the pressure relief valve.

[0016] Optionally, heat dissipation channels are provided inside the upper mold and the lower mold. The heat dissipation channels surround the outside of the mold cavity and are used to circulate gas or liquid to dissipate heat inside the mold cavity.

[0017] Optionally, the air supply assembly includes an air pump and a tee pipe, the air pump is arranged on one side of the pressure-maintaining shell, the output end of the air pump is connected to one end of the tee pipe through a pipe, the other two ends of the tee pipe are connected to the input ends of the heat dissipation channels opened by the upper mold and the lower mold through pipes, and the output ends of the heat dissipation channels opened by the upper mold and the lower mold are connected to the pressure-maintaining cavity.

[0018] Optionally, the air supply component further includes a control valve, which is disposed in the three-way pipe. When the air pressure in the pressure-maintaining chamber reaches a preset threshold, the gas output by the air pump no longer enters the pressure-maintaining chamber.

[0019] Optionally, the extrusion assembly includes an extrusion pipe and a telescopic part, the telescopic part is arranged on the pressure-maintaining shell and located in the pressure-maintaining cavity, the upper mold is fixedly connected to the telescopic end of the telescopic part, the surface of the pressure-maintaining shell is sealed and slidably connected to the outer surface of the extrusion pipe through a through hole, one end of the extrusion pipe is connected to the material source, and the other end is fixedly connected to the upper mold and communicates with the model cavity.

[0020] Optionally, a detachable closing door is provided on the side of the pressure retaining shell, and a sealing strip is provided between the closing door and the pressure retaining shell.

[0021] The present invention provides a composite polypropylene injection molding device, which has the following beneficial effects:

[0022] The composite polypropylene injection molding device delivers the injection molding material into the mold cavity at a fixed quantity and pressure through an extrusion component, blocks the exhaust hole through a blocking mechanism, and squeezes the original gas in the mold cavity during the process of the injection molding material being transported into the mold cavity. The pressure-maintaining shell and the pressure-maintaining cavity are used to deliver positive pressure gas through the air delivery component to assist in sealing the upper mold and the lower mold. When the injection molding material is at the end of input, the original gas in the mold cavity is relatively squeezed on the gas space due to the injection molding material entering the mold cavity space. The gas is compressed and generates gas pressure to push open the blocking mechanism, so that the original gas in the mold cavity is discharged. The gas in the mold cavity is squeezed to form a mold. The reaction force not only pushes the injection material to flow to all corners of the mold, promotes the distribution of the injection material, and enhances the filling effect of the injection material, but also reduces the generation of bubbles inside the injection material, improves the uniformity of the internal structure of the finished product, and compacts the material in a positive pressure environment, so that the injection material can better overcome the flow resistance during the filling process, thereby improving the filling density, reducing the generation of defects such as weld lines and air inclusions, and improving the density and strength of the product, thereby significantly enhancing the structural stability and mechanical impact resistance of the finished product, and improving the reliability and service life of the finished product. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the three-dimensional structure of the composite polypropylene injection molding device of the present invention;

[0024] Figure 2 Schematic diagram of the exploded structure of the mold assembly in the present invention;

[0025] Figure 3 Schematic diagram of the main cross-sectional structure of the composite polypropylene injection molding device of the present invention;

[0026] Figure 4 Schematic diagram of the left side cross-sectional structure of the mold assembly of the present invention;

[0027] Figure 5 Schematic diagram of the top cross-sectional structure of the mold assembly in the present invention;

[0028] Figure 6 For the present invention Figure 3 A is an enlarged structural diagram of FIG.

[0029] In the figure: 100, pressure-maintaining assembly; 110, pressure-maintaining shell; 120, pressure-maintaining cavity; 130, pressure relief mechanism; 131, pressure relief valve; 132, pressure relief port; 200, mold assembly; 210, upper mold; 220, lower mold; 230, mold cavity; 240, blocking mechanism; 241, blocking disk; 242, blocking hole; 243, blocking part; 2431, blocking block; 2432, extrusion spring; 2433, connecting hole; 300, extrusion assembly; 310, extrusion pipe; 320, telescopic part; 400, air supply assembly; 410, air pump; 420, tee pipe; 500, trigger mechanism; 510, reed switch. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative work shall fall within the scope of protection of the present invention.

[0031] See also Figures 1 to 6 , the present invention provides a technical solution: a composite polypropylene injection molding device, comprising a pressure holding component 100, a mold component 200 and an extrusion component 300;

[0032] The pressure-maintaining assembly 100 includes a pressure-maintaining shell 110 having a pressure-maintaining cavity 120 , and a pressure relief mechanism 130 is provided on the pressure-maintaining shell 110 ;

[0033] The mold assembly 200 includes an upper mold 210 and a lower mold 220, and a blocking mechanism 240. A mold cavity 230 is formed between the upper mold 210 and the lower mold 220. The upper mold 210 has an exhaust hole connected to the mold cavity 230. The blocking mechanism 240 is used to connect the exhaust hole to the pressure holding chamber 120 when the air pressure in the mold cavity 230 reaches a threshold.

[0034] The extrusion assembly 300 is used to extrude the injection material into the mold cavity 230 in a quantitative and stable manner;

[0035] The device further includes a gas supply assembly 400 whose output end is connected to the pressure-maintaining chamber 120 , and the gas supply assembly 400 is used to supply positive pressure gas into the pressure-maintaining chamber 120 ;

[0036] The extrusion assembly 300 delivers the injection molding material into the mold cavity 230 at a constant quantity and pressure, and blocks the exhaust hole through the blocking mechanism 240, so that the original gas in the mold cavity 230 is gradually squeezed during the slow delivery of the injection molding material into the mold cavity 230. The positive pressure gas is delivered through the air delivery assembly 400 in cooperation with the pressure holding shell 110 and the pressure holding cavity 120 to assist in sealing the upper mold 210 and the lower mold 220 (specifically, the auxiliary blocking mechanism 240 seals the exhaust hole). When the injection molding material is at the end of input, the original gas in the mold cavity 230 is gradually squeezed, and the gas pressure gradually increases. Then, the gas pressure reaches the threshold value and pushes open the blocking mechanism 240, so that the original gas in the mold cavity 230 is discharged. In the process of slowly conveying the injection molding material into the mold cavity 230, the gas in the mold cavity 230 is squeezed. As the space occupied by the gas gradually becomes smaller, the gas compression forms a reaction force relative to the injection molding material, thereby exerting additional pressure on the injection molding material. This reaction force not only pushes the injection molding material to flow to all corners of the mold, promotes the distribution of the injection molding material, and enhances the filling effect of the injection molding material, but also reduces the generation of bubbles inside the injection molding material, improves the uniformity of the internal structure of the finished product, and compacts the material through a positive pressure environment, so that the injection molding material can better overcome the flow resistance during the filling process, thereby improving the filling density, reducing the occurrence of defects such as weld lines and air entrapment, and improving the density and strength of the product;

[0037] The extrusion assembly 300 is responsible for delivering the molten injection molding material into the mold cavity 230 in a quantitative and stable manner. Its stability and accuracy directly affect the uniform distribution of the material and the consistency of the product. The extrusion assembly 300 has a storage space for storing the molten injection molding material. The molten injection molding material stored in the storage space is extruded through the output end of the extrusion assembly 300.

[0038] The air supply component 400 delivers positive pressure gas into the pressure holding chamber 120, so that the pressure holding chamber 120 is filled with positive pressure gas, so that the gas in the model cavity 230 needs to be squeezed to a certain extent by the injection molding material before it can push open the blocking mechanism 240 and be discharged. It can assist the blocking mechanism 240 to seal the model cavity 230 to ensure the sealing between the upper mold 210 and the lower mold 220. It can also be that when there is a gap between the upper mold 210 and the lower mold 220, the positive pressure gas in the pressure holding chamber 120 can be wrapped between the upper mold 210 and the lower mold 220. When the gas pressure in the model cavity 230 is insufficient, it cannot overcome the pressure of the positive pressure gas and be discharged. The gas pressure of the gas in the model cavity 230 that pushes open the blocking mechanism 240 corresponds to the gas pressure exerted by the positive pressure gas.

[0039] In this embodiment, as a preferred solution, the pressure relief mechanism 130 includes a pressure relief valve 131 and a pressure relief port 132. The pressure relief valve 131 is disposed within the pressure relief port 132. The pressure relief port 132 is provided on the pressure retaining shell 110 and communicates with the pressure retaining chamber 120. The pressure relief valve 131 is used to connect the pressure retaining chamber 120 to the outside when the blocking mechanism 240 connects the exhaust hole to the pressure retaining chamber 120.

[0040] When the blocking mechanism 240 connects the exhaust hole with the pressure-maintaining chamber 120, the pressure-maintaining chamber 120 is connected with the outside, that is, the positive-pressure gas can be discharged from the pressure-maintaining chamber 120 through the pressure relief port 132. The pressure relief valve 131 can be a solenoid valve, which is a well-known technology. It is in a normally closed state during normal use. When the blocking mechanism 240 connects the exhaust hole with the pressure-maintaining chamber 120, it changes from a normally closed state to an open state, allowing the gas in the pressure-maintaining chamber 120 to be discharged from the pressure-maintaining chamber 120.

[0041] In this embodiment, as a preferred solution, the blocking mechanism 240 includes a blocking disk 241, blocking holes 242, and a blocking portion 243. The blocking disk 241 is rotatably connected to the upper mold 210. The blocking holes 242 are circumferentially distributed on the surface of the blocking disk 241 along the axis of the blocking disk 241. The blocking portions 243 are correspondingly disposed in the blocking holes 242. The size of the blocking holes 242 matches that of the exhaust holes.

[0042] Through the connection between the blocking disk 241 and the upper mold 210, the blocking disk 241 can rotate in the upper mold 210. Through the opening of the blocking hole 242, when the blocking disk 241 rotates to different angles, the blocking hole 242 of the corresponding angle is connected with the exhaust hole, and the blocking part 243 in the corresponding blocking hole 242 blocks the exhaust hole and the blocking hole 242. The blocking hole 242 is blocked by the blocking part 243. Since the blocking hole 242 is the same as the exhaust hole, the connection between the model cavity 230 and the pressure holding cavity 120 is cut off and blocked. A sealing ring is provided on the outer ring of the blocking hole 242 corresponding to the blocking hole 242 on the blocking disk 241, which can fill and compensate the gap between the upper mold 210 and the blocking disk 241 to avoid gas leakage due to the gap between the upper mold 210 and the blocking disk 241 when the blocking hole 242 is connected with the exhaust hole.

[0043] In this embodiment, as a preferred solution, the blocking portion 243 includes a blocking block 2431, a pressing spring 2432, and a communicating hole 2433 formed on the inner wall of the blocking hole 242. The blocking block 2431 is slidably connected to the blocking hole 242. One end of the pressing spring 2432 abuts against the blocking hole 242, and the other end abuts against the blocking block 2431.

[0044] The connection between the blocking block 2431 and the blocking hole 242 allows the blocking block 2431 to be lifted and slid in the blocking hole 242. A rubber ring is provided between the blocking block 2431 and the blocking hole 242. That is, the rubber ring is fixedly connected to the outer surface of the blocking block 2431 to serve as an auxiliary seal.

[0045] The blocking block 2431 is provided with a first position and a second position. When the blocking block 2431 is in the first position, both ends of the communicating hole 2433 are communicated with the pressure holding chamber 120. When the blocking block 2431 is subjected to the thrust of the gas in the mold cavity 230, it moves from the first position to the second position. When it moves to the second position, one end of the communicating hole 2433 is communicated with the pressure holding chamber 120, and the other end is communicated with the exhaust hole (i.e., the mold cavity 230). At the same time, the pressure relief valve 131 is opened, and the gas in the mold cavity 230 is discharged through the communicating hole 2433 and communicated with the pressure holding chamber 120. The gas in the pressure holding chamber 120 is discharged to the outside. The extrusion spring 2432 pushes the blocking block 2431 to return to its original position after the gas in the mold cavity 230 is exhausted. After the finished product is taken out, it can be injection molded again.

[0046] The blocking portions 243 in different blocking holes 242 can be set to blocking blocks 2431 of different weights, with the aim of increasing the required gas pressure range in the model cavity 230, and can also cooperate with the positive pressure gas in the pressure holding cavity 120 to increase the required gas pressure range in the model cavity 230. Specifically, when the weight of the blocking block 2431 is X, the positive pressure gas can generate a thrust on the blocking block 2431 with a weight of X, assisting the blocking block 2431 to block the blocking hole 242 until the gas pressure in the model cavity 230 overcomes the sum of the weight of the blocking block 2431, the thrust generated by the positive pressure gas, and the elastic thrust of the extrusion spring 2432, pushing the blocking block 2431 from the first position to the second position. In this application, the gas pressure of the gas in the model cavity 230 after being relatively squeezed by the extruded material is sufficient to achieve this purpose.

[0047] This embodiment, as a preferred solution, further includes a trigger mechanism 500, which includes a reed switch 510. The reed switch 510 is disposed within the upper mold 210. The blocking block 2431 is at least partially made of magnet. When the blocking block 2431 slides to the middle portion between the two ends of the communicating hole 2433, the reed switch 510 receives the magnetism of the blocking block 2431 and operates. The reed switch 510 is connected in series to the circuit of the pressure relief valve 131.

[0048] Through the setting of the reed switch 510, when the blocking block 2431 with magnetic material moves to the second position, corresponding to the reaction position of the reed switch 510, the reed switch 510 is activated by the action of the magnetic force. The reed switch 510 is a well-known technology and is only referenced here. It is connected in series in the circuit of the pressure relief valve 131. When the reed switch 510 receives the magnetic force, the circuit of the pressure relief valve 131 is connected, thereby connecting the pressure holding chamber 120 to the outside world.

[0049] In this embodiment, as a preferred solution, heat dissipation channels are provided inside the upper mold 210 and the lower mold 220. The heat dissipation channels surround the mold cavity 230 and are used to circulate gas or liquid to dissipate heat inside the mold cavity 230.

[0050] The heat dissipation channel is a well-known technology and is only cited here for reference. It is used to cool and solidify the injection molding material in the mold cavity 230.

[0051] In this embodiment, as a preferred solution, the air supply assembly 400 includes an air pump 410 and a tee pipe 420. The air pump 410 is arranged on one side of the pressure-maintaining shell 110. The output end of the air pump 410 is connected to one end of the tee pipe 420 through a pipe. The other two ends of the tee pipe 420 are connected to the input ends of the heat dissipation channels provided in the upper mold 210 and the lower mold 220 through pipes, respectively. The output ends of the heat dissipation channels provided in the upper mold 210 and the lower mold 220 are connected to the pressure-maintaining chamber 120.

[0052] Through the connection between the air pump 410 and the tee pipe 420, the output end of the air pump 410 can deliver gas to the tee pipe 420. Through the action of the tee pipe 420, the gas output by the air pump 410 is delivered to the heat dissipation channels of the upper mold 210 and the heat dissipation channels of the lower mold 220. Then, after passing through the heat dissipation channels of the upper mold 210 and the heat dissipation channels of the lower mold 220, the gas is discharged into the pressure holding chamber 120, acting as positive pressure gas, generating a certain thrust on the blocking block 2431, and assisting the blocking block 2431 in being located in the first position to block the exhaust hole, thereby preventing the communication hole 2433 from being connected.

[0053] When the blocking block 2431 is in the second position, after the pressure relief valve 131 is opened, the gas in the pressure holding chamber 120 has a vent and is discharged through the pressure relief hole, thereby forming an air flow channel, so that the gas output by the air pump 410 can continue to flow through the heat dissipation channel of the upper mold 210 and the heat dissipation channel of the lower mold 220 and then be discharged to the outside, so that the mold cavity 230 can be automatically cooled when pressure holding is not required (that is, after the injection molding material fills the mold cavity 230), reducing manual operation steps, reducing the detection and control process, improving the integration effect, further improving production efficiency, and saving costs.

[0054] In this embodiment, as a preferred option, the air supply component 400 also includes a control valve, which is arranged in the three-way pipe 420. When the air pressure in the pressure holding chamber 120 reaches a preset threshold value, the gas output by the air pump 410 no longer enters the pressure holding chamber 120. The control valve is also an existing well-known technology. When the air pressure in the pressure holding chamber 120 reaches a preset threshold value, the gas output by the air pump 410 no longer enters the pressure holding chamber 120, but is directly discharged to the outside through the control valve without entering the heat dissipation channel of the upper mold 210 and the heat dissipation channel of the lower mold 220.

[0055] In this embodiment, as a preferred embodiment, the extrusion assembly 300 includes an extrusion pipe 310 and a telescopic portion 320. The telescopic portion 320 is disposed on the pressure-retaining shell 110 and is located within the pressure-retaining cavity 120. The upper mold 210 is fixedly connected to the telescopic end of the telescopic portion 320. The surface of the pressure-retaining shell 110 is sealed and slidably connected to the outer surface of the extrusion pipe 310 via a through hole. One end of the extrusion pipe 310 is connected to a material source, and the other end is fixedly connected to the upper mold 210 and communicates with the mold cavity 230.

[0056] The extrusion assembly 300 also includes an extruder, and an extrusion pipe 310 is connected to the output end of the storage space of the extruder. At the same time, the extrusion pipe 310 rises and falls with the upper mold 210 without affecting the injection material output from the output end of the storage space of the extruder. It stably enters the extrusion pipe 310 and then enters the upper mold 210. At the same time, the extruder and the extrusion pipe 310 quantitatively extrude the injection material, which is a well-known technology. No improvement or adjustment is made to the extrusion assembly 300 herein. The purpose is only to provide a source of injection material for the mold cavity 230.

[0057] The telescopic portion 320 may be an electric telescopic rod, which is a known technology and is only cited here. During the injection molding process, the electric telescopic rod extends and presses against the upper mold 210, thereby pressing the upper mold 210 and the lower mold 220 together. At the same time, the connecting surface between the upper mold 210 and the lower mold 220 is also provided with corresponding sealing grooves and sealing blocks, which are common sense means for the purpose of ensuring the stability and sealing of the mold cavity 230. After the injection molding is completed, the electric telescopic rod causes the upper mold 210 to rise, thereby removing the molded product from the lower mold 220.

[0058] In this embodiment, as a preferred solution, a detachable closed door is provided on the side of the pressure retaining shell 110, and a sealing strip is provided between the closed door and the pressure retaining shell 110;

[0059] The closed door is used to take out the molded product when opened, and to ensure the sealing of the pressure-maintaining chamber 120 when closed. This is a conventional setting, and the use of sealing strips is also common knowledge for those skilled in the art.

[0060] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A composite polypropylene injection molding device, characterized in that: It comprises a pressure-maintaining component (100), a mold component (200) and an extrusion component (300); The pressure-maintaining assembly (100) comprises a pressure-maintaining shell (110) having a pressure-maintaining cavity (120), and a pressure relief mechanism (130) is provided on the pressure-maintaining shell (110); The mold assembly (200) comprises an upper mold (210) and a lower mold (220), the upper mold (210), the lower mold (220) and a blocking mechanism (240), a mold cavity (230) is formed between the upper mold (210) and the lower mold (220), and the upper mold (210) is provided with an exhaust hole communicating with the mold cavity (230); The extrusion assembly (300) is used to extrude the injection material into the mold cavity (230) in a quantitative and stable manner; The upper mold (210) and the lower mold (220) are both provided with heat dissipation channels inside, which are used to dissipate heat from the upper mold (210) and the lower mold (220); It also includes an air supply component (400) whose output end is connected to the pressure-maintaining chamber (120) through a heat dissipation channel, and the air supply component (400) is used to deliver positive pressure gas into the pressure-maintaining chamber (120) through the heat dissipation channel; The blocking mechanism (240) comprises a blocking disk (241), a blocking hole (242) and a blocking portion (243); the blocking disk (241) is rotatably connected to the upper mold (210); the blocking holes (242) are circumferentially distributed on the surface of the blocking disk (241) along the axis of the blocking disk (241); the blocking portion (243) is correspondingly arranged in the blocking hole (242); the size of the blocking hole (242) matches the exhaust hole; the blocking portion (243) is used to connect the exhaust hole with the pressure holding cavity (120) when the air pressure in the model cavity (230) reaches a threshold value; The pressure relief mechanism (130) is used to connect the pressure-maintaining chamber (120) with the outside world when the blocking portion (243) connects the exhaust hole with the pressure-maintaining chamber (120); It also includes a trigger mechanism (500), which is used to open the pressure relief mechanism (130) to relieve pressure when the blocking portion (243) causes the exhaust hole to communicate with the pressure-maintaining chamber (120).

2. A composite polypropylene injection molding device according to claim 1, characterized in that: The pressure relief mechanism (130) comprises a pressure relief valve (131) and a pressure relief port (132); the pressure relief valve (131) is arranged in the pressure relief port (132); the pressure relief port (132) is opened on the pressure retaining shell (110) and communicates with the pressure retaining chamber (120).

3. A composite polypropylene injection molding device according to claim 2, characterized in that: The blocking portion (243) comprises a blocking block (2431), a pressing spring (2432) and a connecting hole (2433) provided on the inner wall of the blocking hole (242); the blocking block (2431) is slidably connected in the blocking hole (242); one end of the pressing spring (2432) abuts against the blocking hole (242) and the other end abuts against the blocking block (2431).

4. A composite polypropylene injection molding device according to claim 3, characterized in that: The trigger mechanism (500) comprises a reed switch (510), wherein the reed switch (510) is arranged in the upper mold (210), and the material of the blocking block (2431) is at least partially magnet. When the blocking block (2431) slides to the middle part between the two ends of the connecting hole (2433), the reed switch (510) receives the magnetism of the blocking block (2431) and operates. The reed switch (510) is connected in series in the circuit of the pressure relief valve (131).

5. A composite polypropylene injection molding device according to claim 1, characterized in that: The heat dissipation channel surrounds the outside of the model cavity (230) and is used to circulate gas or liquid to dissipate heat in the model cavity (230).

6. A composite polypropylene injection molding device according to claim 5, characterized in that: The air delivery assembly (400) comprises an air pump (410) and a three-way pipe (420); the air pump (410) is arranged on one side of the pressure-maintaining shell (110); the output end of the air pump (410) is connected to one end of the three-way pipe (420) through a pipeline; the other two ends of the three-way pipe (420) are respectively connected to the input ends of the heat dissipation channels opened in the upper mold (210) and the lower mold (220) through pipelines; and the output ends of the heat dissipation channels opened in the upper mold (210) and the lower mold (220) are connected to the pressure-maintaining cavity (120).

7. A composite polypropylene injection molding device according to claim 6, characterized in that: The gas delivery component (400) further comprises a control valve, which is arranged in the three-way pipe (420) and prevents the gas output by the air pump (410) from entering the pressure-maintaining chamber (120) when the air pressure in the pressure-maintaining chamber (120) reaches a preset threshold.

8. A composite polypropylene injection molding device according to claim 1, characterized in that: The extrusion assembly (300) comprises an extrusion pipeline (310) and a telescopic part (320); the telescopic part (320) is arranged on the pressure-retaining shell (110) and is located in the pressure-retaining cavity (120); the upper mold (210) is fixedly connected to the telescopic end of the telescopic part (320); the surface of the pressure-retaining shell (110) is sealed and slidably connected to the outer surface of the extrusion pipeline (310) via a through hole; one end of the extrusion pipeline (310) is connected to a material source, and the other end is fixedly connected to the upper mold (210) and communicates with the mold cavity (230).

9. A composite polypropylene injection molding device according to claim 1, characterized in that: A detachable closing door is provided on the side of the pressure retaining shell (110), and a sealing strip is provided between the closing door and the pressure retaining shell (110).

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