A die structure for plastic pipe extrusion

Abstract

The utility model relates to a die structure for plastic tubular product extrusion belongs to die technical field, specifically including the both ends of die mounting seat are installed with the shunt cone body and melt segmentation mixer respectively, the end of melt segmentation mixer is installed with the core mould, the outside of shunt cone body is installed with the front end mould body, is provided with the upstream runner between the front end mould body and shunt cone body, the outside of core mould is installed with the die head, is provided with the downstream runner between die head and core mould, the die mounting seat is provided with a plurality of annular distribution's overflow port, and the overflow port is used for connecting the upstream runner, melt segmentation mixer and downstream runner, the utility model discloses structure design is reasonable, can eliminate the traditional die support structure formation fusion line influence product mechanical property.

Description

Technical Field

[0001] This utility model relates to a mold structure for extruding plastic pipes, belonging to the field of mold technology. Background Technology

[0002] In the extrusion molding process of plastic pipes, the compaction and shaping of the polymer melt through a molding die is an essential step. When the pipe is composed of two or more raw materials, the uniformity of their dispersion directly affects the stability of the extrusion process and the physical and mechanical properties of the finished product. The commonly used support-structure molds in plastic pipe molding primarily compact the polymer melt fed into the mold by the screw and preliminarily shape it into a pipe blank according to the cross-sectional shape of the mold's flow channels. They do not have a dispersing function for multi-component polymer melts. In production practice, it is common to directly extrude pipes using polymer materials as the main material and containing various functional additives. The plasticizing and dispersing effect of a single-screw extruder is limited, especially in the later stages of its use when the barrel and screw are worn significantly. This leads to poor dispersion of the functional components, resulting in unstable plastic pipe extrusion processing and product physical and mechanical properties. The 1995 textbook *Plastic Machinery Design*, co-edited by Beijing University of Chemical Technology and South China University of Technology (pp. 132-136), details the use of static mixers with different structures between the die and extruder. This allows the multi-component polymer melt to be mixed before entering the die cavity flow channel, achieving homogenization. However, static mixers generally have a small flow channel cross-section. When the generally high-viscosity polymer fluid flows into the static mixer, the internal temperature of the melt rises sharply, causing excessive shear force and instability, affecting subsequent product molding. Furthermore, the problem of decreased mechanical properties due to longitudinal fusion lines formed after the die support divides and re-fusions remains unresolved. Utility Model Content

[0003] To address the technical problems existing in the prior art, this utility model provides a mold structure for plastic pipe extrusion with a reasonable structural design that can eliminate the influence of fusion lines formed by traditional mold support structures on the mechanical properties of the product.

[0004] To achieve the above objectives, the technical solution adopted by this utility model is a mold structure for extruding plastic pipes, including a front mold body, a flow divider cone, a mold mounting base, an orifice die, and a core die. The flow divider cone and a melt divider mixer are respectively installed at both ends of the mold mounting base. The core die is installed at the end of the melt divider mixer. The front mold body is installed outside the flow divider cone. An upstream flow channel is provided between the front mold body and the flow divider cone. An orifice die is installed outside the core die. A downstream flow channel is provided between the orifice die and the core die. The mold mounting base is provided with multiple flow ports arranged in a ring. The flow ports are used to connect the upstream flow channel, the melt divider mixer, and the downstream flow channel.

[0005] Preferably, the melt dividing mixer includes an annular outer mold shell and an inner mold tube. The inner surface of the annular outer mold shell and the outer surface of the inner mold tube are uniformly provided with a plurality of dividing protrusions. The dividing protrusions on the annular outer mold shell and the inner mold tube are arranged alternately with gaps. The mold mounting base and the core mold are both provided with connecting posts. Two of the connecting posts are respectively threaded into the inner mold tube.

[0006] Preferably, the mold mounting base is further provided with a central airflow channel, which passes through the connecting column. The mold mounting base is also provided with multiple airflow channels communicating with the outside world on its circumference. The airflow channels are connected to the central airflow channel. The core mold is provided with an airflow outlet channel, which passes through the core mold and the connecting column and is connected to the central airflow channel.

[0007] Preferably, the front mold body, the mold mounting base and the melt dividing mixer are connected by bolts, the die is mounted on the die fixing plate, the die fixing plate is mounted on the melt dividing mixer, and the die fixing plate is also mounted with a die pressing plate for pressing the die.

[0008] Preferably, the dividing protrusion is a cubic prism, a cylindrical prism, an elliptical prism, a water droplet, or any curved prism.

[0009] Compared with existing technologies, this invention has the following technical advantages: This invention employs a melt-splitting mixer installed inside the mold. This mixer ensures more uniform dispersion and mixing of the multi-component polymer melt within the mold, which is beneficial for promoting the stability of the physical and mechanical properties of the extruded plastic pipe. After passing through the mixer, the polymer fluid exhibits smaller melt pressure differences on the same cross-section, and the extrusion speed differences along the circumferential cross-section of the flow channel are also smaller, effectively eliminating pipe extrusion fusion lines and contributing to greater product dimensional stability. Simultaneously, cooling gas channels evenly distributed along the circumferential direction within the mold pass through each support to reach the mold interior. During high-speed extrusion, each gas channel introduces cooling gas into the mold interior, preventing uncontrolled melt temperatures at both the support flow channels and the melt-splitting mixer flow channels.

[0010] Furthermore, the mold structure of this invention is suitable for multi-component polymer melts of various viscosities and Reynolds numbers, especially multi-component polymer melts that are difficult to disperse or have high dispersion requirements. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of this utility model.

[0012] Figure 2 This is a schematic diagram of the exploded structure of this utility model.

[0013] Figure 3 This is the left view of the present invention.

[0014] Figure 4 This is a schematic diagram of the annular outer mold shell in this utility model.

[0015] Figure 5 This is a schematic diagram of the inner mold tube in this utility model. Detailed Implementation

[0016] To make the technical problems, technical solutions, and beneficial effects of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0017] like Figures 1 to 5 As shown, a mold structure for extruding plastic pipes includes a front mold body 1, a flow divider cone 2, a mold mounting base 3, an orifice 4, and a core mold 5. The flow divider cone 2 and a melt divider mixer 6 are respectively installed at both ends of the mold mounting base 3. The core mold 5 is installed at the end of the melt divider mixer 6. The front mold body 1 is installed outside the flow divider cone 2. An upstream flow channel 7 is provided between the front mold body 1 and the flow divider cone 2. The orifice 4 is installed outside the core mold 5. A downstream flow channel 8 is provided between the orifice 4 and the core mold 5. The mold mounting base 3 is provided with multiple flow ports 9 arranged in a ring. The flow ports 9 are used to connect the upstream flow channel 7, the melt divider mixer 6, and the downstream flow channel 8.

[0018] In this invention, a melt dividing mixer 6 is installed between the front die body 1 and the die 4. The front die body 1, the die mounting base 3, and the melt dividing mixer 6 are connected by bolts. The die 4 is mounted on the die fixing plate 17, which is also mounted on the melt dividing mixer 6. A die clamping plate 18 for pressing the die 4 is also installed on the die fixing plate 17. The front die body 1 is used to connect to the extruder flange. The multi-component polymer melt in the extruder can enter the melt dividing mixer 6 through the upstream flow channel 7. After being mixed in the melt dividing mixer 6, it is extruded through the downstream flow channel 8. The die mounting base 3 serves to install the die and also divides the annular tubular fluid according to the number of flow ports 9. Due to the effect of the flow ports, the cross-section of the polymer fluid is reduced, the melt pressure increases, and the melt temperature rises accordingly, thereby improving the extrusion effect.

[0019] The melt dividing mixer 6 includes an annular outer mold shell 10 and an inner mold tube 11. Multiple dividing protrusions 12 are evenly arranged on the inner surface of the annular outer mold shell 10 and the outer surface of the inner mold tube 11. The dividing protrusions on the annular outer mold shell 10 and the inner mold tube 11 are arranged alternately with gaps. Connecting posts 13 are provided on both the mold mounting base 3 and the core mold 5. The two connecting posts 13 are threaded into the inner mold tube 11 respectively.

[0020] The melt segmentation mixer 6 employs nested annular outer mold shells 10 and inner mold tubes 11. Multiple segmentation protrusions 12 are uniformly arranged on the inner surface of the annular outer mold shell 10 and the outer surface of the inner mold tube 11. These segmentation protrusions 12 can be cubic prisms, cylinders, elliptical cylinders, prismatic prisms, droplets, or any curved surface. The number of segmentation protrusions along the circumference, the dislocations in the longitudinal arrangement, the shape, size, number, and arrangement of the segmentation elements, and the angle of attack of the segmentation elements on the polymer fluid can be designed and adjusted according to the rheological properties of the polymer melt and the state of the fluid Reynolds number to accommodate multi-component polymer melts with different viscosities and fluid Reynolds numbers. When the multi-component polymer melt enters the mold, it allows for more uniform dispersion of the functional components in the polymer matrix. Simultaneously, after the polymer fluid flows through the melt segmentation mixer, it effectively eliminates the fluid pressure difference formed at the same cross-section after the melt flows through the support structure, thereby overcoming the influence of the fusion line formed by the mold support on the mechanical properties of the product.

[0021] Furthermore, to suppress the uncontrolled rise in the temperature of the polymer melt, a central airflow channel 14 is provided at the center of the mold mounting base 3, which passes through the connecting pillar 13. Multiple airflow channels 15 connected to the outside are also provided on the circumference of the mold mounting base 3, and these airflow channels 15 are connected to the central airflow channel 14. An airflow outlet channel 16 is provided at the center of the core mold 5, passing through the core mold 5 and the connecting pillar 13, and is connected to the central airflow channel 14. Gas is supplied to the mold through the airflow channels 15. The gas flowing through each channel converges at the central airflow channel 14, and then flows out of the mold through the airflow outlet channel 16. During this process, the gas is heated by the mold and the polymer melt inside the mold, carrying away some of the heat.

[0022] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model shall be included within the scope of the present utility model.

Claims

1. A mold structure for extruding plastic pipes, comprising a front mold body, a flow-dividing cone, a mold mounting base, an orifice mold, and a core mold, characterized in that: The mold mounting base has a flow divider cone and a melt divider mixer installed at both ends, respectively. A core mold is installed at the end of the melt divider mixer. A front mold body is installed on the outside of the flow divider cone. An upstream flow channel is provided between the front mold body and the flow divider cone. An orifice mold is installed on the outside of the core mold. A downstream flow channel is provided between the orifice mold and the core mold. The mold mounting base has multiple flow ports arranged in a ring. The flow ports are used to connect the upstream flow channel, the melt divider mixer and the downstream flow channel.

2. The mold structure for extruding plastic pipes according to claim 1, characterized in that: The melt dividing mixer includes an annular outer mold shell and an inner mold tube. Multiple dividing protrusions are evenly arranged on the inner surface of the annular outer mold shell and the outer surface of the inner mold tube. The dividing protrusions on the annular outer mold shell and the inner mold tube are arranged alternately with gaps. Connecting posts are provided on the mold mounting base and the core mold. Two of the connecting posts are threaded into the inner mold tube.

3. The mold structure for extruding plastic pipes according to claim 2, characterized in that: The mold mounting base is also provided with a central airflow channel at its center, which passes through the connecting column. The mold mounting base is also provided with multiple airflow channels that communicate with the outside world on its circumference. The airflow channels are connected to the central airflow channel. The core mold is provided with an airflow outlet channel at its center, which passes through the core mold and the connecting column and is connected to the central airflow channel.

4. The die structure for extruding plastic pipes according to claim 1, characterized in that: The front mold body, mold mounting base and melt dividing mixer are connected by bolts. The die is mounted on the die fixing plate, the die fixing plate is mounted on the melt dividing mixer, and the die fixing plate is also mounted with a die pressure plate for pressing the die.

5. The mold structure for extruding plastic pipes according to claim 2, characterized in that: The dividing protrusions can be cubic prisms, cylindrical prisms, elliptical prisms, prismatic prisms, teardrop-shaped prisms, or any curved surface prisms.

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