A porous insulating extrusion device and method thereof

Abstract

The application provides a porous insulating extrusion device and a method thereof. Through the cooperative design of a through-hole porous inner die and a flow-controlled blowing assembly, a plurality of continuous and stable airflow columns are formed at the outlet of the inner die. The molten rubber material fills and covers the airflow columns, and then is extruded through the outer die to directly form a solid insulating layer with a regular axial hole structure. In combination with a selectable gear pump flow stabilizing mechanism, precise porous insulating extrusion of 32AWG-44AWG ultra-fine coaxial lines can be realized, and the method is suitable for a plurality of materials such as polypropylene, perfluoroethylene propylene, soluble polytetrafluoroethylene, thermoplastic polyester elastomer and poly-4-methyl-1-pentene. The number of through holes on the inner die and the size of the blowing flow are accurately controlled to reduce the dielectric constant, realize low delay and low attenuation electrical performance, and the device has low investment cost, wide material adaptation range and high process stability, which provides a new technical path for the preparation of ultra-fine coaxial line insulation, and has the advantages of controllable process, stable yield, and easy popularization and implementation.

Description

Technical Field

[0001] This application belongs to the technical field of polymer production equipment, specifically relating to a porous insulating extrusion device and its extrusion method. Background Technology

[0002] With the rapid development of 5G communications, consumer electronics, medical imaging, and other fields, ultra-fine coaxial cables of 32AWG to 44AWG (US wire gauge) are widely used for high-frequency signal transmission inside precision electronic equipment due to their small size and excellent signal transmission performance. To meet the requirements of low-latency high-frequency electrical characteristics, the insulation layer of ultra-fine coaxial cables usually needs to incorporate a porous structure to reduce the dielectric constant. Currently, the industry mainly uses two technical paths to achieve porous insulation extrusion.

[0003] In existing technologies, the first type of solution is the physical foaming extrusion process. This involves injecting nitrogen or carbon dioxide into the molten rubber compound under high pressure using a dedicated physical foaming extruder, followed by extrusion through the inner and outer dies of the die head to form a foamed insulator with irregularly distributed cells. While this solution can meet electrical performance requirements, it has significant drawbacks: the investment cost of dedicated perfluoroethylene propylene (FEP) / soluble polytetrafluoroethylene (PFA) physical foaming extruders is enormous, with single units ranging from several million to tens of millions of yuan. This high equipment procurement cost limits the widespread application of this process; supply stability and cost fluctuate; and the supply chain lacks autonomy and control, with significant uncertainties in raw material costs and delivery cycles.

[0004] The second approach involves a conventional extruder vacuum process. A vacuum pump creates a pressure difference in the die area, which, combined with the outer die structure, achieves shaping. The pressure difference and linear velocity create traction, causing the rubber compound to adhere to and coat the conductor's outer periphery, forming a porous solid insulating layer. This approach has relatively low equipment investment, but it suffers from significant limitations: insufficient precision in pore size, pore shape continuity, structural uniformity, and process stability. Especially in the production of ultra-fine coaxial cables of 32AWG and smaller specifications, even slight fluctuations in extrusion pressure can lead to pore size deviations and channel breakage, resulting in low product yield and poor consistency, making it difficult to meet the stringent requirements of high-frequency signal transmission. Furthermore, this process is highly sensitive to the melt flow rate of the material, only suitable for low-viscosity fluoroplastics, and has poor moldability for non-fluoromaterials such as polypropylene (PP) and thermoplastic polyester elastomers (TPEE), severely limiting its applicability.

[0005] Therefore, in order to balance the electrical performance, production stability, and manufacturing cost of ultra-fine coaxial porous insulation, overcome the aforementioned technical defects in existing technologies, and expand the application range of materials, it is currently urgent to make systematic improvements to the extrusion process and supporting equipment for porous insulation, so as to achieve high-precision and high-stability porous insulation production based on ordinary extrusion equipment, and meet the industry's demand for low-cost and high-reliability mass production. Summary of the Invention

[0006] In order to address the technical problems in the prior art, such as high equipment investment costs, limited raw material supply chain, poor pore shape stability and inconsistency, and narrow material applicability of the physical foaming extrusion process, which cannot simultaneously achieve the electrical performance, mass production stability and economy of ultra-fine coaxial porous insulation, this application proposes a porous insulation extrusion method and extrusion device.

[0007] The present application adopts the following technical solution: a porous insulating extrusion device, including a die head disposed on a preset mounting reference surface, an inner mold disposed in the die head, an outer mold sleeved on the outer periphery of the inner mold, and a guide pipe communicating with the die head for conveying molten rubber to the mold cavity between the inner mold and the outer mold, and also including an air blowing assembly; The inner mold has a central hole for the conductor to pass through, and the inner mold also has multiple through-holes that extend along the axial direction. The air blowing assembly is provided with an air blowing fixing device on the machine head and an air blowing center rod on the inner mold. The air blowing center rod extends axially into the interior of the inner mold, and its outer wall at the end is tightly fitted with the inner wall of the inner mold to form a sealing fit. An air inlet channel is formed between the air blowing center rod and the inner wall of the guide tube, and the air inlet channel is connected to each through-type air blowing hole.

[0008] Specifically, the blowing center rod has an axial air inlet chamber inside, which is connected to each through-hole blowing hole; the blowing fixing device has an air inlet that is sealed and connected to the air inlet chamber of the blowing center rod.

[0009] Specifically, the blowing assembly also includes an air source unit with flow control, which is used to deliver a preset flow rate of air to the blowing center rod.

[0010] In some feasible embodiments, the extrusion apparatus further includes a gear pump located between the extruder and the die head, for homogenizing and stabilizing the extrusion flow rate of the molten rubber.

[0011] In some feasible embodiments, the number of through-holes is 3 to 8, and they are evenly distributed along the circumference of the central hole.

[0012] In some feasible embodiments, the cross-sectional shape of the through-hole is circular, fan-shaped, trapezoidal, or regular polygonal.

[0013] In some feasible embodiments, an annular cavity is provided between the inner mold and the outer mold, and the annular cavity is connected to the discharge end of the guide tube.

[0014] To address the technical problems raised in this application, this application also provides an extrusion method for a porous insulating extrusion apparatus, comprising the following steps: Step a: Install the inner mold, outer mold, and air blowing assembly onto the mounting position of the extrusion head. Step b: Turn on the air blowing assembly, set the air blowing volume through the flow controller, and the airflow enters each through-hole of the inner mold along the air inlet channel, forming multiple continuous airflow columns at the outlet of the inner mold. Step c: The molten rubber material in the annular cavity between the inner mold and the outer mold fills and covers the multiple airflow columns, and is continuously extruded after being sized by the outer mold to form a solid insulated core wire with an axial porous structure.

[0015] In some feasible embodiments, in step c, the melt flow rate (MFR) of the adhesive compound is ≥15 g / 10 min, and the adhesive compound is any one of PP, FEP, PFA, TPEE, and PMP. The MFR data for PP, TPEE, and PMP are based on test method ASTM D1238 230C, under conditions of 2.16 kg; the MFR data for FEP and PFA are based on test method ASTM D2116 372C, under conditions of 5 kg (all MFR data mentioned in the context are based on this test method).

[0016] In some feasible embodiments, in step b, a discontinuous porous insulation structure is prepared by adjusting the air flow rate and air interval of the air blowing assembly; the air blowing interval is controlled by a solenoid valve to open and close the air path according to a preset cycle.

[0017] In some feasible embodiments, in step c, after the rubber compound is heated and extruded from the extruder, it is first subjected to flow homogenization and pressure stabilization treatment by a gear pump, and then conveyed to the feed pipe of the die head; the gear pump is linked and controlled with the extruder.

[0018] In some feasible embodiments, in step c, the cooling and shaping method of the solid insulated core wire is one of air cooling, room temperature water cooling, or ice water cooling.

[0019] In actual implementation, the air-blowing center rod extends axially into the rear mounting hole of the inner mold, and its outer end wall fits tightly against the inner wall of the inner mold to form a radial seal. The rubber flow channel is located in the annular cavity on the outer periphery of the inner mold, independent of the air inlet channel. The air-blowing fixing device connects the air-blowing assembly to the die head, ensuring the coaxiality and airtightness of the air path and preventing channel forming failure caused by air leakage. Multiple through-holes evenly distributed circumferentially in the inner mold rectify and equalize the airflow in the air inlet channel, transforming the originally chaotic compressed gas into multiple parallel, continuous, and stable axial airflow columns, which are evenly ejected from the outlet end of the inner mold. The guide pipe transports the molten rubber output from the extruder to the annular cavity between the inner and outer molds. The cavity gradually narrows along the extrusion direction, causing the molten rubber to form a uniform circumferential pressure, smoothly wrapping around the outer periphery of the airflow columns, and finally being extruded and formed through the sizing die of the outer mold.

[0020] Specifically, after the equipment is heated to the set temperature, the molten rubber enters the annular cavity through the feed pipe and flows towards the outlet under pressure; The blowing assembly with flow control outputs gas at a set pressure, which is rectified through the air inlet channel and through-hole blowing hole, forming a continuous airflow column in the same direction as the extrusion direction at the inner mold outlet. Under the pressure of the cavity, the molten rubber material is uniformly coated and filled along the outer periphery of the air column. The internal pressure of the air column counteracts the radial shrinkage force of the rubber material, preventing the channel from collapsing and forming an insulating blank with axial through holes. The insulating blank, which is covered by the airflow column, is extruded after being sized by the outer mold. It then enters the cooling stage to cool down and solidify rapidly. The airflow is continuously discharged during the extrusion process, eventually forming a solid insulating core wire with a regular axial porous structure. The conductor passes through the central hole of the inner mold and is always located in the center of the insulation layer to ensure concentricity.

[0021] In practical implementation, this application utilizes the rectifying effect of the through-hole airflow and the precise pressure regulation of the flow controller to control the size and pressure fluctuation range of the airflow column within ±5%. Compared to the traditional vacuum process that relies on pressure difference adsorption molding, this effectively offsets the impact of extrusion pressure fluctuations and linear velocity changes on the hole shape, reducing the probability of broken holes, eccentric holes, and dimensional deviations. Based on melt flow characteristics, this application eliminates the need for dedicated foaming masterbatches and is compatible with various insulating materials such as PP, FEP, PFA, TPEE, and PMP with a melt flow rate (MFR) ≥ 15 g / 10 min. This overcomes the limitation of traditional vacuum processes, which are only suitable for low-viscosity fluoroplastics, allowing for flexible selection of raw materials according to product performance requirements. By changing the inner mold with different hole diameters and quantities, and adjusting the airflow rate, this application can continuously control the opening ratio and channel size of the insulating layer within a certain range, thereby precisely controlling the equivalent dielectric constant of the insulating layer to match the electrical performance requirements of different product specifications.

[0022] More preferably, the room temperature gas is rapidly preheated over the distance from the blowing center rod placed in the guide tube to the inner die opening. After preheating, when the gas is blown out of the inner die into a stable airflow column, its temperature will be slightly lower than the temperature of the extruded rubber. This temperature difference helps the rubber shrink and cover the airflow column to form a stable through hole, which can avoid the defect of melt fracture, improve the surface smoothness of the insulation layer and the continuity of the channel, and is especially suitable for the extrusion of high melting point fluoroplastics such as PFA.

[0023] In actual implementation, during the start-up phase, air is initially supplied at a low flow rate. Once the rubber compound is stably extruded and the linear speed reaches the set value, the air flow rate is gradually increased to the target value. During normal production, the flow controller finely adjusts the air flow rate in real time based on the fluctuation of the extrusion pressure, and the fluctuation range of the air flow rate is controlled within ±3%.

[0024] The above process can avoid channel rupture caused by airflow impact at the moment of startup, improve startup yield, and ensure dynamic stability of channel size during production.

[0025] In actual implementation, air cooling is sufficient to achieve the insulation curing requirement when the extruded core wire is at low speed. When the production speed is increased, room temperature water or ice water can be used at 1-2m in the end water tank to accelerate cooling.

[0026] This process avoids stress cracking of the insulation layer and shrinkage deformation of the pores caused by rapid cooling, thus ensuring the dimensional accuracy and structural integrity of the porous structure.

[0027] Compared with the prior art, this application has the following beneficial effects: This application provides a porous insulation extrusion device and method. Through the collaborative design of a through-hole porous inner mold and a blowing component with flow control, multiple continuous and stable airflow columns are formed at the outlet of the inner mold. Molten rubber fills and covers the airflow columns and is then extruded through the outer mold to directly form a solid insulation layer with a regular axial hole structure. With the optional gear pump flow stabilization mechanism, it can realize the precision porous insulation extrusion of 32AWG to 44AWG ultra-fine coaxial lines. It is suitable for various materials such as polypropylene (PP), perfluoroethylene propylene (FEP), soluble polytetrafluoroethylene (PFA), thermoplastic polyester elastomer (TPEE), and poly4-methyl-1-pentene (PMP) with a melt flow rate (MFR) ≥15g / 10min. This solution eliminates the need for expensive specialized physical foaming equipment, overcoming the technical bottlenecks of large fluctuations and poor continuity in pore size in traditional vacuum processes. It can precisely control the opening ratio of the insulation layer by blowing air flow to reduce the dielectric constant, achieving low delay and low attenuation electrical performance. At the same time, it has low equipment investment costs, a wide range of material compatibility, and high process stability, providing a brand-new technical path for the preparation of ultra-fine coaxial cable insulation. It has the advantages of controllable process, stable yield, and easy promotion and implementation. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a porous insulation extrusion device according to this application; Figure 2 This is a side view of the inner mold of this application; Figure 3 This is a sectional view of the inner mold of this application. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below through specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Combination Figures 1-3 Examples 1-4 and Comparative Examples 1-4 further illustrate the technical solutions proposed in this application.

[0031] Specifically, a porous insulating extrusion device includes a die head 1, an inner mold 2 and an outer mold 3 disposed within the die head 1, a feed tube 4, and an air blowing assembly. The inner mold 2 has a central hole 12 for a conductor 7 to pass through, and also has multiple through-holes 13 extending axially. The air blowing assembly 8 includes an air blowing fixing device 10 and an air blowing center rod 6, which extends axially into the inner mold 2, with its outer end tightly fitted against the inner wall of the inner mold 2 to form a sealing fit. An air inlet channel is formed between the air blowing center rod 6 and the inner wall of the feed tube 4, and the air inlet channel is connected to each of the through-holes 13. An annular cavity 5 is formed between the inner mold 2 and the outer mold 3, and the cavity 5 is connected to the discharge end of the feed tube 4. Preferably, the device further includes a gear pump, which is disposed between the extruder and the die head 1, and is used to homogenize and stabilize the extrusion flow rate of the molten rubber. Preferably, the number of through-holes 13 is 3 to 8, and they are evenly distributed around the circumference of the central hole 12 of the inner mold.

[0032] Example 1 This embodiment prepares 36AWG ultrafine coaxial porous insulated core wire using FEP adhesive with an MFR of 22±1g / 10min. The specific steps are as follows: 1. Standby extruder: Set the temperature of each section of the single screw extruder: Zone 1 290℃, Zone 2 340℃, Zone 3 342℃, clamp 345℃, and die head temperature 348℃. After the temperature stabilizes, add FEP material to the hopper and preheat and plasticize for 15 minutes to complete the standby.

[0033] 2. Mold and device installation: Install the inner mold and the outer mold. The inner mold has 8 square through-holes for blowing air, which are evenly distributed around the center hole. Install the blowing center rod, the blowing fixing device and the blowing assembly with flow control, so that the end of the blowing center rod fits tightly against the inner wall of the inner mold to form a sealed air intake channel.

[0034] 3. Air blowing parameter setting: Turn on the air blowing component and use air as the blowing medium. Set the total air blowing flow rate to 0.075L / min through the flow controller so that the airflow enters each through-hole through the air inlet channel and forms 6 continuous and stable airflow columns at the inner mold outlet.

[0035] 4. Threading preparation: Release the silver-plated copper conductor through the wire release frame, and pass it in sequence through the air blowing center rod, the center hole of the inner mold, and the center hole of the outer mold. Then, connect it to the take-up device through the ambient temperature water tank and the wire storage guide wheel, and set the take-up speed to 27m / min.

[0036] 5. Extrusion production: Start the extruder, and the molten FEP material enters the cavity between the inner and outer dies through the feed tube. The material is filled and covered by 6 airflow columns. After being sized by the outer die, it is continuously extruded to form a solid insulated core wire with 6 axial holes. The outer diameter of the insulation layer is controlled to be 0.35mm, and the conductor is located in the center of the insulation layer.

[0037] 6. Cooling and winding: The extruded core wire enters a three-section water tank for air cooling and shaping. After being tested by a capacitor in the water, it is dried by a blower and then wound and packaged to complete the preparation.

[0038] Example 2 This embodiment prepares 42AWG micro coaxial porous insulated core wire using PFA adhesive with an MFR of 28±1g / 10min. A gear pump flow stabilization mechanism is added. The specific steps are as follows: 1. Extrusion main unit standby: Set the temperature of each section of the single screw extruder main unit: Zone 1 290℃, Zone 2 340℃, Zone 3 342℃, clamp 345℃, and die head temperature 348℃. After the temperature stabilizes, add PFA rubber to the hopper and preheat and plasticize for 20 minutes to complete the standby.

[0039] 2. Gear pump linkage setting: A high-precision gear pump is connected between the extruder and the die head. The speed of the gear pump is set to be linked with the speed of the screw of the extruder to homogenize and stabilize the extrusion amount of rubber material and stabilize the extrusion pressure.

[0040] 3. Mold and device installation: Install the inner mold and outer mold. The inner mold has 6 circular through-holes for blowing air, which are evenly distributed around the center hole. Install the blowing center rod and blowing assembly to ensure a tight seal.

[0041] 4. Air blowing parameter setting: Turn on the air blowing component, using air as the blowing medium, and set the total air blowing flow rate to 0.045L / min, forming 6 continuous and stable fan-shaped airflow columns at the inner mold outlet. 5. Threading preparation: Release the silver-plated copper alloy conductor through the wire release frame, pass it through each device in sequence, and connect it to the wire take-up device. Set the take-up speed to 30m / min.

[0042] 6. Extrusion production: Start the extruder and gear pump. The molten PFA material is homogenized by the gear pump and enters the cavity. It is extruded around 6 fan-shaped airflow columns and sized by the outer die to form a solid insulated core wire with 4 fan-shaped holes. The outer diameter of the insulation layer is controlled to be 0.32mm.

[0043] 7. Cooling and winding: The extruded core wire enters a three-section water tank for air cooling and shaping. After being tested by a capacitor in the water, it is dried by a blower and then wound and packaged to complete the preparation.

[0044] Example 3 This embodiment prepares 32AWG ultrafine coaxial porous insulated core wire using PP adhesive with an MFR of 16±1g / 10min. The specific steps are as follows: 1. Standby for the extruder: Set the temperature of each section of the single screw extruder as follows: Zone 1 180℃, Zone 2 200℃, Zone 3 220℃, Zone 4 230℃, clamp 232℃, neck 235℃, and die head 230℃. After the temperature stabilizes, add PP material to the hopper and preheat and plasticize for 10 minutes to complete the standby.

[0045] 2. Mold and device installation: Install the inner mold and outer mold. The inner mold has 8 trapezoidal through-holes for blowing air, which are evenly distributed around the center hole. Install the blowing center rod and blowing assembly to ensure a tight seal.

[0046] 3. Air blowing parameter setting: Turn on the air blowing component and use clean compressed air that has been de-dusted and de-oiled as the air blowing medium. Set the total air blowing flow rate to 0.10L / min, and form 8 continuous and stable trapezoidal airflow columns at the inner mold outlet.

[0047] 4. Threading preparation: Release the tinned copper conductor through the wire release frame, pass it through each device in sequence, and connect it to the wire take-up device. Set the take-up speed to 30m / min.

[0048] 5. Extrusion production: Start the extruder, and the molten PP material enters the cavity and is extruded around 8 airflow columns. After being sized by the outer die, it forms a solid insulated core wire with 8 trapezoidal holes; control the outer diameter of the insulation layer to 0.50mm.

[0049] 6. Cooling and winding: The extruded core wire enters a three-section water tank for air cooling and shaping. After being tested by a capacitor in the water, it is dried by a blower and then wound and packaged to complete the preparation.

[0050] Example 4 This embodiment prepares 36AWG discontinuous porous insulated core wire using FEP compound with an MFR of 22±1g / 10min. The air blowing interval is controlled by a solenoid valve. The specific steps are as follows: 1. Extrusion main machine standby and mold installation: The process parameters are consistent with those in Example 1. A high-frequency solenoid valve is connected in the blowing air circuit and connected in series with the flow controller.

[0051] 2. Air blowing parameter setting: Turn on the air blowing component and solenoid valve, set the total air blowing flow rate to 0.075L / min, and set the solenoid valve on / off cycle to 0.5s on and 0.5s off to form an intermittent airflow column.

[0052] 3. Extrusion production: Start the extruder, molten FEP compound fills and coats the intermittent airflow column, and is continuously extruded after being sized by the outer die to form a discontinuous porous insulated core wire with intermittent axial holes; control the outer diameter of the insulation layer to 0.35mm.

[0053] 4. Cooling and winding: The process is consistent with that in Example 1 to complete the preparation of discontinuous multi-hole insulated core wire.

[0054] Comparative Example 1 36AWGFEP foamed insulated core wire was prepared using existing physical foaming extrusion technology. A dedicated physical foaming extruder was used, and nitrogen gas was injected for foaming. The outer diameter of the insulation layer was controlled at 0.35 mm. The degree of foaming was comparable to the open porosity of Example 1, and the other specifications were consistent with those of Example 1.

[0055] Comparative Example 2 36AWGFEP porous insulated core wire was prepared using the existing vacuum extrusion process. A regular extruder was used in conjunction with a vacuum die to control the outer diameter of the insulation layer to 0.35mm. The other specifications were the same as in Example 1.

[0056] Comparative Example 3 36AWGFEP insulated core wires were prepared using a single-hole inner mold combined with an air blowing process. The inner mold had only one air blowing hole around the central conductor hole, and the remaining process parameters were consistent with those in Example 1.

[0057] Comparative Example 4 36AWGFEP porous insulated core wires were prepared using a blow-air process without flow control. The wires were directly connected to an atmospheric pressure air source without flow controller adjustment. The remaining structure and process parameters were consistent with those in Example 1.

[0058] According to the testing standards shown in Table 1 below, the core wire samples prepared in Examples 1-4 and Comparative Examples 1-4 were subjected to performance tests. For each test group, 1000m of sample were continuously produced, and the average value was recorded. Table 1: Test Items The test results are shown in Table 2 below.

[0059] Table 2 Performance Test Results As shown in Table 2, in Examples 1-4, the combined effect of the through-hole inner mold and the air blowing component with flow control forms multiple continuous and stable axial airflow columns at the outlet of the inner mold. The molten rubber is shaped and extruded around the airflow columns, resulting in a regular and continuous porous solid insulation structure with excellent performance.

[0060] On the one hand, the process stability of this application is significantly better than that of the traditional vacuum process, far superior to Comparative Example 2, and can more closely approach the characteristic impedance of the 50Ω standard center value with a smaller delay. The core reason is that this solution rectifys and guides the airflow through a through-hole, resulting in a stable airflow column with clear boundaries. Combined with a flow controller to precisely regulate the airflow, it can offset the influence of rubber extrusion pressure fluctuations on the pore shape, ensuring consistent pore size and position. In contrast, the vacuum process relies on pressure difference adsorption molding, and even slight fluctuations in rubber viscosity, extrusion speed, and vacuum level will be directly transmitted to the pore shape, leading to pore diameter fluctuations and pore breakage, making stability difficult to guarantee. At the same time, the electrical performance of this solution is close to that of high-cost physical foaming processes, with the dielectric constant stably controlled below 1.70, and the impedance and delay are basically equivalent to those of the physical foaming solution, fully meeting the low delay requirements of high-frequency signal transmission.

[0061] On the other hand, the equipment investment cost of this application is low. It eliminates the need for a dedicated FEP / FPA physical foaming extruder and the reliance on imported foaming materials. Production can be achieved simply by adding an air-blowing component and a dedicated inner mold to a standard extruder, significantly lowering the industry entry barrier and enabling companies to quickly achieve mass production of porous, insulated, ultra-fine coaxial cables. Furthermore, this solution is compatible with various insulating materials such as PP, FEP, and PFA with an MFR ≥ 15g / 10min, overcoming the limitation of existing vacuum processes that only work with a few fluoroplastics, allowing for more flexible material selection.

[0062] Comparative Example 1 uses a traditional physical foaming process, which has similar electrical performance to this application, but has high equipment investment costs.

[0063] Comparative Example 2 uses a vacuum process, and the equipment cost is similar to that of this application. However, due to the influence of the internal structure of the die head and the installation of the inner and outer molds, it is difficult to create a completely vacuum environment. Since a stable vacuum environment cannot be provided continuously, the shape of the hole is difficult to control, which increases the risk of production instability and the possibility of production debugging or unstable continuous production, resulting in higher actual mass production costs.

[0064] Comparative Example 3 uses a single-hole air-blowing structure, which cannot form a circumferentially uniformly distributed porous structure. The opening ratio is limited, the dielectric constant is relatively high, and the airflow in the single hole is prone to deviation. The hole shape stability and impedance consistency are significantly worse than the porous scheme of this application, and the design goal of reducing the dielectric constant cannot be fully achieved.

[0065] Comparative Example 4 uses an air blowing method without flow control. Fluctuations in air source pressure are directly transmitted to the airflow column, causing the orifice size to fluctuate and the orifice channel to be intermittent. The orifice shape qualification rate and consistency decrease significantly, and the electrical performance deteriorates accordingly. This proves that the combination of flow control and multi-hole inner mold is the key to achieving stable extrusion, and neither can be lacking.

[0066] In summary, this application provides a porous insulation extrusion device and method. Through the collaborative design of a through-hole porous inner mold and a blowing assembly with flow control, multiple continuous and stable airflow columns are formed at the outlet of the inner mold. The molten rubber fills and covers the airflow columns and is then extruded through the outer mold to directly form a solid insulation layer with a regular axial hole structure. With the optional gear pump flow stabilization mechanism, it can achieve precision porous insulation extrusion of 32AWG to 44AWG ultra-fine coaxial lines. It is suitable for various materials such as polypropylene (PP), perfluoroethylene propylene (FEP), soluble polytetrafluoroethylene (PFA), thermoplastic polyester elastomer (TPEE), and poly4-methyl-1-pentene (PMP) with a melt flow rate (MFR) ≥15g / 10min. This solution eliminates the need for expensive dedicated FEP / PFA / PP physical foaming equipment, overcoming the technical bottlenecks of traditional vacuum processes, such as difficulty in controlling pore shape, relatively large dimensional fluctuations, and poor continuity. It allows for precise control of the number and size of openings in the insulation layer through air blowing flow, thereby achieving the desired porosity to reduce the dielectric constant and realize low-delay electrical performance. At the same time, it features low equipment investment costs, a wide range of material compatibility, and high process stability, providing a brand-new technical path for the preparation of ultra-fine coaxial cable insulation. It has the advantages of controllable process, stable yield, and ease of promotion and implementation.

[0067] The embodiments provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A porous insulating extrusion device, comprising a die head disposed on a preset mounting reference surface, an inner mold disposed within the die head, an outer mold sleeved around the outer periphery of the inner mold, and a guide pipe communicating with the die head for conveying molten rubber to the mold cavity, characterized in that, It also includes an air blowing component; The inner mold has a central hole for the conductor to pass through, and the inner mold also has multiple through-holes that extend along the axial direction. The air blowing assembly includes an air blowing fixing device on the machine head and an air blowing center rod on the inner mold. The air blowing center rod extends axially into the interior of the inner mold, and its outer end wall is tightly fitted with the inner wall of the inner mold. An air inlet channel is formed between the air blowing center rod and the inner wall of the guide tube, and the air inlet channel is connected to each through-type air blowing hole.

2. The porous insulating extrusion apparatus according to claim 1, characterized in that, It also includes a gear pump, which is located between the extruder and the die head, and is used to homogenize and stabilize the extrusion flow rate of the molten rubber.

3. The porous insulating extrusion apparatus according to claim 1, characterized in that, The number of through-holes is 3 to 8, and they are evenly distributed around the circumference of the central hole.

4. The porous insulating extrusion apparatus according to claim 1, characterized in that, The cross-sectional shape of the through-hole is circular, fan-shaped, trapezoidal, or regular polygonal.

5. The porous insulating extrusion apparatus according to claim 1, characterized in that, An annular cavity is provided between the inner mold and the outer mold, and the annular cavity is connected to the discharge end of the guide tube.

6. An extrusion method for a porous insulating extrusion apparatus according to any one of claims 1-5, characterized in that, Includes the following steps: Step a: Install the inner mold, outer mold, and air blowing assembly onto the mounting position of the extrusion head. Step b: Turn on the air blowing assembly, set the air blowing volume through the flow controller, and the airflow enters each through-hole of the inner mold along the air inlet channel, forming multiple continuous airflow columns at the outlet of the inner mold. Step c: The molten rubber material in the annular cavity between the inner mold and the outer mold fills and covers the multiple airflow columns, and is continuously extruded after being sized by the outer mold to form a solid insulated core wire with an axial porous structure.

7. The extrusion method of a porous insulating extrusion apparatus according to claim 6, characterized in that, In step c, the melt flow rate (MFR) of the adhesive is ≥15 g / 10 min, and the adhesive is any one of PP, FEP, PFA, TPEE, and PMP.

8. The extrusion method of a porous insulating extrusion apparatus according to claim 6, characterized in that, In step b, a discontinuous porous insulation structure is prepared by adjusting the air flow rate and air interval of the air blowing assembly; the air blowing interval is controlled by a solenoid valve to open and close the air path according to a preset cycle.

9. The extrusion method of a porous insulating extrusion apparatus according to claim 6, characterized in that, In step c, after the rubber compound is heated and extruded from the extruder, it is first subjected to flow homogenization and pressure stabilization treatment by a gear pump, and then conveyed to the feed pipe of the die head.

10. The extrusion method of a porous insulating extrusion apparatus according to claim 6, characterized in that, In step c, the cooling and shaping method for the solid insulated core wire is one of air cooling, room temperature water cooling, or ice water cooling.

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