Low-odor ethylene propylene diene monomer preparation process and equipment

Abstract

The invention discloses a low-odor ethylene propylene diene monomer preparation process and equipment, and relates to the technical field of rubber processing. A sealing cover capable of being opened is arranged on one side of the negative pressure tank, a heat tracing system is arranged outside the negative pressure tank, and sliding ways are symmetrically and fixedly connected to the upper portion and the lower portion in the negative pressure tank; and the feeding box is slidably connected to the slide way at the upper part of the negative pressure tank and is used for feeding vulcanizable rubber compound, and a plurality of mutually parallel slots are formed in a bottom plate of the feeding box. The pressure difference formed by negative pressure is used for driving bubbles to be naturally separated out, rubber structure damage and hole residues caused by puncture are fundamentally avoided, the mechanical property of a product is completely reserved, the product is made into a sheet shape through mechanical extrusion, the migration path of the bubbles from the interior of rubber to the surface of the rubber is greatly shortened through the sheet shape, and the product quality is improved. The migration resistance of the bubbles in the rubber is reduced, and the technical bottleneck that the bubbles are difficult to discharge due to breaking through the strong resistance of a thick rubber layer in a pure negative pressure environment is solved.

Description

Technical Field

[0001] This invention relates to the field of rubber processing technology, specifically to a process and equipment for preparing low-odor EPDM rubber. Background Technology

[0002] Ethylene propylene diene monomer (EPDM) rubber is a synthetic rubber copolymerized from ethylene, propylene, and a small amount of non-conjugated diene. Due to its excellent weather resistance, ozone resistance, and chemical stability, it is widely used in automotive seals, building waterproofing, and other fields. However, its odor has long plagued the industry. The odor mainly originates from residual catalysts in the raw rubber, aromatic softeners, decomposition products of vulcanizing agents, and volatile impurities from fillers. In odor-sensitive applications such as automotive interiors, the demand for low-odor EPDM is particularly prominent.

[0003] The existing EPDM rubber manufacturing process uses EPDM raw rubber as the main component, combined with chemical additives and fillers, and is completed through processes such as ingredient mixing, compounding and plasticizing, filtration, extrusion molding, vulcanization, inspection, and packaging. However, during production, the vulcanizable compounded rubber raw materials are prone to forming a large number of bubbles due to air entrainment during mixing and trace gases generated by the vulcanization reaction. These bubbles are difficult to eliminate during extrusion molding, resulting in defects such as porosity and looseness in the final product. This not only directly affects the mechanical properties and sealing reliability of the product, but also becomes a significant source of odor. These internal bubbles constitute a microscopic enrichment zone and rapid migration channel for volatile organic compounds (VOCs): on the one hand, trace low-molecular-weight residues, processing aids, and decomposition products generated during mixing and vulcanization are trapped inside the bubbles and cannot escape; on the other hand, the large number of microbubbles greatly increases the specific surface area inside the rubber, providing a concentrated and rapid release path for these odor substances when the product is heated or compressed during subsequent use, significantly exacerbating the odor problem.

[0004] To address the bubble problem, existing technology proposes a process for preparing EPDM rubber (publication number CN115230044B). This process includes the following steps: Step 1: Heating multiple raw materials to a fluid state and mixing them; Step 2: Kneading the resulting rubber raw material and inspecting the kneaded product; Step 3: Vulcanizing the inspected raw material; Step 4: Extruding and packaging the vulcanized rubber raw material. The EPDM rubber preparation process utilizes EPDM rubber, and the apparatus includes a molding frame for extruding the rubber. A door panel slides on one side of the molding frame, and multiple circular plates rotate on the molding frame. Each of these circular plates has a sliding blade capable of cutting the rubber raw material, which can break down the pores in the accumulated rubber raw material.

[0005] The proposed solution involves using a cutting tool to cut the rubber and disrupt the pores. A rotating disc on the molding frame drives the cutting tool to puncture the accumulated rubber, achieving "physical defoaming." However, this method has significant drawbacks: First, the cutting tool leaves tiny holes inside the rubber, which become new accumulation points for air bubbles, resulting in poor defoaming effects. Second, the rubber becomes harder after vulcanization, making it difficult for the cutting tool to completely penetrate the thick rubber layer; air bubbles are easily cut and dispersed rather than completely expelled. Furthermore, puncturing disrupts the continuous structure of the rubber, leading to a decrease in the product's mechanical properties and failing to solve the problem of residual air bubbles between layers. Summary of the Invention

[0006] The purpose of this invention is to provide a process and equipment for preparing low-odor EPDM rubber, so as to solve the problem that the physical defoaming method in the above-mentioned background technology is not effective and easily introduces new bubbles.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A process for preparing low-odor EPDM rubber includes the following steps: S1. Mixing: Mix the raw EPDM rubber, compounding agents and vulcanizing agents to obtain a uniform vulcanizable compound. S2. Negative pressure sheeting and degassing: The vulcanizable compound is placed in a closed negative pressure environment and mechanically extruded into a sheet at a first temperature T1. The sheet shape and negative pressure work together to remove air bubbles. The first temperature T1 is higher than the softening temperature of the rubber compound but lower than the rapid vulcanization start temperature of the vulcanization system used. S3. Hot-press vulcanization molding: Under the condition of maintaining negative pressure or inert environment, the degassed sheet rubber material is stacked, and then the temperature is raised to a second temperature T2, and pressure is applied at temperature T2 for hot pressing; the second temperature T2 is higher than the first temperature T1, and reaches the temperature range in which the vulcanization system undergoes a rapid cross-linking reaction, so that the vulcanization cross-linking reaction of the rubber material is completed simultaneously with the hot-press molding process, resulting in a dense vulcanized rubber block; S4. Post-processing: Cooling, unloading and packaging the rubber block.

[0008] By precisely controlling the process temperature, the rubber compound containing vulcanizing agent is first extruded into thin sheets in a low-temperature plastic state. The thin sheet shape greatly shortens the bubble migration path, and combined with the driving force provided by the negative pressure environment, the bubbles are efficiently and completely removed, avoiding the problem of odorous bubbles remaining inside the rubber and continuously releasing odors for a long time.

[0009] A further improvement of the technical solution of the present invention is that: in step S4, the thickness of the sheet-like adhesive is 5 to 10 mm; the sealed negative pressure environment is a low vacuum environment, and the vacuum degree is controlled at -0.07 to -0.09 MPa; the first temperature T1 is 70℃ to 90℃; and the second temperature T2 is 160℃ to 180℃.

[0010] By adopting the above technical solution, the bubble degassing efficiency, sheet structure stability and energy consumption control are balanced by precisely limiting key parameters, ensuring that the process can be implemented stably in different production scenarios. This avoids the problems of bubble residue and sheet breakage, reduces equipment operating energy consumption, and improves the bonding effect of subsequent lamination and compaction.

[0011] A further improvement of the technical solution of the present invention is that the vulcanizing agent is a peroxide vulcanizing agent, and the first temperature T1 is lower than the decomposition temperature of the peroxide vulcanizing agent.

[0012] By adopting the above technical solution and selecting peroxide as the vulcanizing agent, a clear plastic processing window is provided: below the decomposition temperature of peroxide, the rubber compound can maintain an uncrosslinked plastic flow state for a long time during the negative compression sheeting stage, thereby ensuring that it can be successfully extruded into thin sheets to achieve efficient degassing. This achieves precise separation of degassing and vulcanization in terms of timing.

[0013] This invention also provides a low-odor EPDM rubber preparation device, comprising: a frame; a negative pressure tank, fixedly mounted on the frame, with an openable sealing cover on one side of the negative pressure tank, a heating system installed outside the negative pressure tank, and symmetrically fixedly connected slide rails at the upper and lower parts inside the negative pressure tank; a feeding box, slidably connected to the slide rail at the upper part of the negative pressure tank, for feeding vulcanizable compounded rubber, with several parallel slits on the bottom plate of the feeding box; an extrusion component for extruding the rubber, including an electric push rod fixedly mounted on the top of the negative pressure tank, the movable end of the electric push rod extending into the interior of the negative pressure tank and fixedly connected to a pressure block, the shape of the pressure block matching the inner cavity shape of the feeding box; and a molding box, slidably connected to the slide rail at the lower part of the negative pressure tank, for receiving the extruded sheet-like rubber, the inner cavity shape of the molding box matching the shape of the pressure block; both the molding box and the feeding box are fixed to the negative pressure tank by quick-release locking buckles.

[0014] By adopting the above technical solution, the negative pressure tank is used as the core working space. The process is realized by using its openable sealing cover. During the process, the heating and temperature control system is used to accurately maintain the process environment of the first or second temperature inside the tank, so as to provide the required plastic conditions or vulcanization reaction conditions for the rubber material at different stages, ensuring efficient removal of bubbles and stable performance of the final product.

[0015] A further improvement of the technical solution of the present invention is that: the bottom plate of the feeding box is set as an openable structure, including two templates symmetrically and rotatably connected to the two sides of the bottom of the feeding box, with slots opened on the templates, a worm gear fixedly connected to one end of the template rotation shaft, a transmission box fixedly connected to one side of the feeding box, worms rotatably connected to both sides of the inner wall of the transmission box, a dual-axis motor fixedly connected to the side of the feeding box near the transmission box, the output end of the dual-axis motor being fixedly connected to the two worms respectively, and the worm gear and the worm are corresponding and meshing.

[0016] By adopting the above technical solution, the bottom of the feeding box is designed to be openable. After the sheet is made, the bottom of the feeding box is opened to allow the pressing block to pass through until it enters the forming box for pressing and shaping. This achieves an integrated operation of sheet making and compaction, avoids air mixing in during the operation, and further improves the degassing effect.

[0017] A further improvement of the technical solution of the present invention is that: two side plates are symmetrically and fixedly connected inside the negative pressure tank, and several scraping racks are fixedly connected to each side plate. The scraping racks correspond one-to-one with the slots. The scraping rack includes an installation part and a scraping part. The width of the scraping part matches the width of the slot. A guide platform is fixedly connected to the top of the slide below. The top of the guide platform has a slope, and the height of the guide platform near the middle position is lower than the height of the periphery.

[0018] By adopting the above technical solution, a scraper that matches the slot is fixed on the side plate of the negative pressure tank. When the template is opened, the scraper inserts into the slot to thoroughly remove residual rubber, ensuring uniform sheet thickness and providing a stable path for bubble migration. By setting a guide platform with an inclined surface at the top of the slide, the sheet is guided to slide along the inclined surface towards the center of the forming box, avoiding falling and deviation, and achieving neat stacking. The two work together to reduce bubble residue caused by uneven thickness and misalignment, improve the density of the rubber block, and reduce the frequency of manual cleaning, ensuring continuous operation of the equipment.

[0019] A further improvement of the technical solution of the present invention is as follows: Support seats are fixedly connected to both sides of the slide inside the negative pressure tank. A bidirectional screw is rotatably connected between the inner sides of the support seats. Two sliders are symmetrically threaded to the outer sides of the bidirectional screw. The sliders are slidably connected to the support seats. A support rod is hinged to one side of each slider. A support block is hinged between the ends of the two support rods away from the sliders. The tops of both the support block and the support rods are in contact with the bottom of the template. A retraction motor is fixedly installed on one side of the support seat. The output end of the retraction motor is fixedly connected to one end of the bidirectional screw.

[0020] By adopting the above technical solution, a support structure with bidirectional screws, sliders and struts linked on both sides of the slide is set. When the template is closed and squeezed, the screw drives the slider to slide in opposite directions to unfold the strut. The support block rises and presses against the bottom of the template to form a stable support, disperse pressure and avoid deformation. It ensures that the strip seams are aligned and the joints are sealed, guarantees the forming accuracy of the sheet and prevents the leakage of the adhesive. When the template is opened, the screw reverses to make the support block fall to avoid the gap, without affecting the opening and closing.

[0021] A further improvement of the technical solution of the present invention is that: a number of vibrators are fixedly installed on the side of the template away from the feeding box; a chamfer is provided on the side of the template away from its rotation axis, and the chamfer and the inclined surface of the top of the guide platform are both 45°; the length of the template is less than the distance between the bottom of the guide platform and the rotation axis of the template, and greater than the distance between the top of the guide platform and the rotation axis of the template.

[0022] By adopting the above technical solution, a vibrator is set up so that the rubber material can move downwards with shaking when it is extruded through the slit. On the one hand, this promotes the precipitation of air bubbles, and on the other hand, it can promote the downward detachment of the rubber material at the end of the extrusion.

[0023] Preferably, the surfaces of the feeding box, forming box, pressing block, template and rejecting rack are all provided with an anti-stick coating, which is a Teflon anti-stick coating.

[0024] By adopting the above technical solution, Teflon anti-stick coatings are applied to all locations that can come into contact with the adhesive, reducing rubber adhesion throughout the entire process from adhesive input, extrusion into thin sheets, stacking and compaction to seam cleaning. This not only improves the working efficiency of each component and ensures the stability of product quality, but also reduces equipment cleaning costs and downtime.

[0025] By adopting the above technical solution, the technical effects achieved by this invention compared to the prior art are as follows: 1. This invention places the vulcanizable compound in a closed negative pressure environment, using the pressure difference created by the negative pressure to drive the natural precipitation of bubbles. This fundamentally avoids the damage to the rubber structure and the presence of pores caused by punctures, thus achieving complete preservation of the product's mechanical properties. Furthermore, it uses mechanical extrusion to form it into a thin sheet, which significantly shortens the migration path of bubbles from the inside of the rubber to the surface, reducing the migration resistance of bubbles inside the rubber. This solves the technical bottleneck that bubbles are difficult to expel under simple negative pressure environments because they need to overcome the strong resistance of thick rubber layers.

[0026] 2. This invention, through the synergistic effect of the sheet-like shape and the negative pressure environment, provides sufficient power for bubble precipitation without relying on high vacuum, achieving efficient degassing under low vacuum conditions. This significantly reduces energy consumption during the vacuuming process and the technical requirements for providing a vacuum environment, while also reducing the pressure replenishment time during repeated opening and closing of the tank, thus greatly improving production efficiency. By directly stacking and compacting the degassed sheet-like rubber in the same sealed negative pressure environment, secondary air mixing during material transfer is avoided. The continuous support and compaction effect of the negative pressure environment promotes tight adhesion between the sheet layers, completely solving the problem of residual bubbles between layers and effectively avoiding quality defects such as porosity and looseness.

[0027] 3. By setting the bottom of the feeding box to be openable, the bottom of the feeding box can be opened after the sheet is made, so that the pressing block can pass through until it enters the forming box for pressing and shaping. This realizes the integrated operation of sheet making and compaction, avoids air mixing in during the operation, and further improves the degassing effect.

[0028] 4. This invention uses a scraper that matches the seam to be fixed to the side plate of the negative pressure tank. When the template is opened, the scraper inserts into the seam to thoroughly remove residual rubber, ensuring uniform sheet thickness and providing a stable path for bubble migration. By setting a guide platform with an inclined surface at the top of the slide, the sheet is guided to slide along the inclined surface towards the center of the forming box, avoiding falling and deviation, and achieving neat stacking. The two work together to reduce bubble residue caused by uneven thickness and misalignment, improve the density of the rubber block, and reduce the frequency of manual cleaning, ensuring continuous operation of the equipment.

[0029] 5. This invention provides a support structure with bidirectional screws, sliders, and struts linked on both sides of the slide. When the template is closed and compressed, the screws drive the sliders to slide in opposite directions, causing the struts to unfold. The support blocks rise and press against the bottom of the template, forming a stable support, dispersing pressure and preventing deformation. This ensures that the seams are aligned and the joints are sealed, guaranteeing the precision of sheet forming and preventing material leakage. Attached Figure Description

[0030] The invention will now be further described with reference to the accompanying drawings.

[0031] Figure 1 This is a flowchart of the process flow of the present invention; Figure 2 This is one of the structural schematic diagrams of the entire invention with the sealed cover of the negative pressure tank open. Figure 3 This is the second schematic diagram of the overall structure of the invention with the sealed cover of the negative pressure tank open. Figure 4 This is the third schematic diagram of the overall structure of the invention with the sealed cover of the negative pressure tank open. Figure 5 This is one of the three-dimensional cross-sectional structural schematic diagrams of the present invention; Figure 6 This is a second three-dimensional sectional view of the present invention; Figure 7 This is a schematic diagram of the feeding box of the present invention with the bottom template in a closed state; Figure 8 This is a schematic diagram of the feeding box of the present invention with the bottom template in the open state; Figure 9 For the present invention Figure 8 Enlarged view of point A in the middle; Figure 10 This is a three-dimensional structural diagram of the overall external structure of the present invention.

[0032] In the diagram: 1. Frame; 2. Negative pressure tank; 3. Slide rail; 4. Feeding box; 5. Forming box; 6. Slot; 7. Template; 8. Electric push rod; 9. Pressing block; 10. Transmission box; 11. Worm gear; 12. Dual-axis motor; 13. Worm wheel; 14. Support base; 15. Retraction motor; 16. Bidirectional screw; 17. Slider; 18. Support rod; 19. Support block; 20. Side plate; 21. Mounting part; 22. Scraping part; 23. Vibrator; 24. Guide table; 25. Chamfer; 26. Quick-release lock. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the embodiments.

[0034] Example like Figure 1 As shown, the present invention provides a process for preparing low-odor EPDM rubber, comprising the following steps: S1. Mixing: Mix the raw EPDM rubber, compounding agents and vulcanizing agents to obtain a uniform vulcanizable compound. Ethylene propylene diene monomer (EPDM) raw rubber, filler oil, reinforcing fillers (such as carbon black and silica), antioxidants, processing aids, and vulcanizing agents (such as DCP peroxide) are placed in an internal mixer and thoroughly mixed under conditions below the decomposition temperature of the vulcanizing agent to obtain a homogeneous vulcanizable compound. The key at this stage is to ensure uniform dispersion of the vulcanizing agent while avoiding premature initiation of crosslinking reactions.

[0035] S2. Negative pressure sheeting and degassing: The vulcanizable compound is placed in a closed negative pressure environment and mechanically extruded into a sheet at a first temperature T1. The sheet shape and negative pressure work together to remove air bubbles. The first temperature T1 is higher than the softening temperature of the rubber compound but lower than the rapid vulcanization start temperature of the vulcanization system used. This temperature, T1, needs to be higher than the softening temperature of the rubber compound to ensure good plasticity, but must be strictly lower than the rapid decomposition initiation temperature of the selected vulcanization system (such as peroxide). At this "safe window" temperature, the mechanical extrusion device is activated to uniformly extrude the rubber compound through specific gaps into continuous sheets with a thickness of 5–10 mm. At the instant the sheet is formed and falls, due to the rapid decrease in thickness, the path for internal air bubbles to migrate to the surface is significantly shortened; simultaneously, the negative pressure environment maintained within the equipment creates a pressure difference, which works synergistically on the sheet, allowing air bubbles to be efficiently and thoroughly removed from the rubber compound. The degassed sheets are then stacked and collected at the bottom of the equipment.

[0036] S3. Hot-press vulcanization molding: Under the condition of maintaining negative pressure or inert environment, the degassed sheet rubber material is stacked, and then the temperature is raised to a second temperature T2, and pressure is applied at temperature T2 for hot pressing; the second temperature T2 is higher than the first temperature T1, and reaches the temperature range in which the vulcanization system undergoes a rapid cross-linking reaction, so that the vulcanization cross-linking reaction of the rubber material is completed simultaneously with the hot-press molding process, resulting in a dense vulcanized rubber block; In this process, high temperature (T2) and high pressure work together to produce a dual effect: firstly, the interfaces of the uncured plastic sheets soften, melt, and interpenetrate, flowing and fusing into a whole under high pressure; secondly, the high temperature simultaneously activates the vulcanization crosslinking reaction, which is completed during the microscopic flow and fusion of the rubber compound. This synchronicity between hot pressing and vulcanization crosslinking draws on the core concept of dynamic vulcanization, ensuring that the crosslinking network forms uniformly while the product is finally shaped, resulting in a vulcanized rubber block that is internally dense, has no interlayer interfaces, and exhibits excellent mechanical properties.

[0037] S4. Post-processing: Cooling, unloading and packaging the rubber block.

[0038] By precisely controlling the process temperature, the rubber compound containing vulcanizing agent after mixing is first extruded into thin sheets in a low-temperature (T1, such as 70-90℃) plastic state. The thin sheet shape greatly shortens the bubble migration path, and combined with the driving force provided by the negative pressure environment, the bubbles are efficiently and completely removed, avoiding the problem of odorous bubbles existing inside the rubber and continuously releasing odors for a long time. Subsequently, without disrupting the sealed environment, the temperature is rapidly increased to the vulcanization reaction range (T2, such as 160-180℃), and hot pressure is applied. This allows the degassed sheet to undergo interfacial melting and flow fusion under high temperature and pressure, simultaneously completing the vulcanization crosslinking reaction. This continuous process of plastic degassed and dynamic vulcanization molding avoids the problem of the rubber compound being unable to be plastically processed due to complete vulcanization first in traditional methods, as well as the bottleneck of bubbles being difficult to expel due to excessive rubber layer thickness in simple negative pressure treatment. The final result is the production of EPDM rubber products with no bubbles inside or between layers, a dense and uniform structure, complete mechanical properties, and low odor.

[0039] The solution uses precise temperature control to mechanically extrude the rubber into thin sheets while it is in a stage where it maintains good plasticity (first temperature T1). The thin sheet shape significantly shortens the path of bubbles migrating from the inside to the surface, thus significantly reducing migration resistance. At this stage, the pressure difference formed by the closed negative pressure environment provides sufficient power for bubble precipitation, thereby achieving efficient degassing at a lower vacuum level. This reduces the dependence on high vacuum equipment and the corresponding energy consumption.

[0040] From the stacking of degassed sheets to the final hot-press vulcanization molding, all processes are continuously completed in the same closed negative pressure environment. This integrated operation completely avoids the secondary mixing of air during material transfer, and at the same time, the continuous negative pressure environment and hot pressing promote tight adhesion between the sheet layers, fundamentally solving the problem of residual air bubbles between layers.

[0041] Preferably, in step S4, the thickness of the sheet-like adhesive is 5-10 mm; the sealed negative pressure environment is a low vacuum environment, with the vacuum degree controlled at -0.07 to -0.09 MPa; the first temperature T1 is 70℃ to 90℃; and the second temperature T2 is 160℃ to 180℃.

[0042] Since the solution requires repeatedly opening the negative pressure tank 2 to take out and put out materials, if the negative pressure environment is controlled to an absolute vacuum, not only will the technical requirements be high, but all the pressure will also need to be released each time the tank is opened, resulting in a huge waste of energy.

[0043] In this embodiment, by precisely defining key parameters, the bubble degassing efficiency, sheet structure stability and energy consumption control are balanced, ensuring that the process can be stably implemented in different production scenarios. This avoids the problems of bubble residue and sheet breakage, reduces equipment operating energy consumption, and improves the bonding effect of subsequent lamination and compaction.

[0044] Furthermore, the thickness of the sheet rubber is controlled at 5-10 mm. This thickness ensures that the bubble migration path is short enough to facilitate rapid precipitation, while maintaining the structural integrity of the sheet itself and avoiding breakage or curling due to excessive thinness. Furthermore, the closed negative pressure environment is set to a low vacuum state, with the vacuum degree controlled between -0.07 and -0.09 MPa. This provides sufficient pressure difference for bubble precipitation without approaching absolute vacuum, while reducing the energy consumption of vacuuming when repeatedly opening and closing the tank, making it suitable for intermittent production. Furthermore, during degassing, the processing temperature is controlled at a first temperature T1 (70℃~90℃), which serves a dual purpose. First, it is above the softening point of the EPDM rubber compound, ensuring the compound is in a suitable plastic flow state for extrusion. Second, and more importantly, this temperature is strictly controlled below the rapid decomposition temperature of the selected vulcanization system (such as peroxides), forming a "process safety window" to ensure that the compound maintains its thermoplasticity and does not undergo significant cross-linking reactions during the sheeting and degassing process, which can last for several minutes. During hot-press vulcanization, the processing temperature is controlled at the second temperature T2 (160℃~180℃). This temperature is crucial for triggering and completing the vulcanization reaction. This temperature is much higher than T1 and reaches the activation temperature range for rapid decomposition of the vulcanizing agent and cross-linking of rubber molecular chains. Hot pressing at this temperature can simultaneously achieve two goals: first, to rapidly soften the degassed plastic sheet and fuse the interface; and second, to efficiently initiate and complete the vulcanization cross-linking reaction, achieving dynamic synchronization between molding and vulcanization.

[0045] Preferably, the vulcanizing agent is a peroxide vulcanizing agent, and the first temperature T1 is lower than the decomposition temperature of the peroxide vulcanizing agent.

[0046] In this embodiment, selecting peroxide as the vulcanizing agent and using its decomposition temperature as the upper limit control point of the first temperature T1 is a key synergistic design for achieving plastic degassing followed by hot-press vulcanization in this process. This design first provides a clear plastic processing window: at T1 (70–90°C), below the peroxide decomposition temperature, the rubber compound can maintain an uncrosslinked plastic flow state for a long time during the negative compression sheeting stage, ensuring it can be smoothly extruded into sheets for efficient degassing. This achieves precise temporal separation between degassing (physical process) and vulcanization (chemical process). When the temperature jumps to T2 (160–180°C), which is much higher than the decomposition point, the peroxide rapidly decomposes, triggering a uniform and thorough C-C bond crosslinking reaction. This not only endows the product with excellent heat resistance and compression set resistance, but its low-odor byproduct characteristics also directly contribute to the product's core objectives.

[0047] like Figures 2-10As shown, the present invention also provides a low-odor EPDM rubber preparation device, comprising: a frame 1; a negative pressure tank 2, fixedly installed on the frame 1, with an openable sealing cover on one side of the negative pressure tank 2, and a heating and temperature control system for precisely reaching and maintaining the working area inside the tank at a first temperature T1 or a second temperature T2, with slide rails 3 symmetrically fixedly connected to the upper and lower parts of the negative pressure tank 2; and a feeding box 4, slidably connected to the slide rails 3 on the upper part of the negative pressure tank 2, for feeding vulcanizable compound rubber, with an opening on the bottom plate of the feeding box 4. The device includes several parallel slits 6; an extrusion component for extruding the rubber material, comprising an electric push rod 8 fixedly mounted on the top of the negative pressure tank 2, the movable end of the electric push rod 8 extending into the interior of the negative pressure tank 2 and fixedly connected to a pressure block 9, the shape of which matches the inner cavity shape of the feeding box 4; a forming box 5 slidably connected to a slide rail 3 at the bottom of the negative pressure tank 2 for receiving the extruded sheet-like rubber material, the inner cavity shape of which matches the shape of the pressure block 9; both the forming box 5 and the feeding box 4 are fixed to the negative pressure tank 2 by quick-release latches 26.

[0048] The heating and temperature control system includes a heating module, a temperature sensor and a controller integrated into the negative pressure tank 2. The controller is configured to set and control the temperature inside the tank to operate stably within a first range of 70℃ to 90℃ or a second range of 160℃ to 180℃.

[0049] Preferably, the pressing block 9 is made of high-temperature resistant material, and a heating unit is integrated inside the pressing block 9.

[0050] The negative pressure tank 2 is equipped with a vacuum pumping device, which can maintain the pressure inside the tank in a low vacuum range of -0.07 to -0.09 MPa. The vacuum pumping device includes an integrated vacuum pump (such as a rotary vane pump or a micro screw pump), a vacuum valve, a pressure sensor, and a control system, forming an independent unit.

[0051] The quick-release latch 26 includes a mounting sheet metal, an L-shaped pin slidably connected to the mounting sheet metal, a pad fixedly connected to the L-shaped pin, and a locking spring sleeved on the L-shaped pin. One end of the L-shaped pin is set as a pointed tip, and insertion holes for cooperating with the L-shaped pin are opened on the top of the feeding box 4 and the bottom of the forming box 5.

[0052] Existing rubber preparation equipment lacks an integrated structure adapted to low-odor processes, cannot provide a stable, sealed negative pressure environment to meet degassing requirements, and cannot meet the continuous requirements of plastic degassing and hot-pressing dynamic vulcanization. Furthermore, it lacks coordinated extrusion and molding components, resulting in dispersed processes for achieving the above-mentioned technologies. Air is easily introduced during material transfer, forming secondary bubbles. The sealing structure is cumbersome during material changes, the vacuum environment is prone to leakage, and repeated vacuuming and pressurization are required, increasing energy consumption. Insufficient temperature control precision leads to fluctuations in bubble precipitation efficiency and poor product quality stability. In this embodiment, the negative pressure tank 2 is used as the core working space, and its openable sealing cover is used to realize the process. During the process, the heating and temperature control system is used to precisely maintain the process environment of the first temperature T1 (70~90℃) or the second temperature T2 (160~180℃) in the tank, so as to provide the required plastic conditions or vulcanization reaction conditions for the rubber material at different stages, and ensure efficient removal of bubbles and stable performance of the final product. Furthermore, by setting an electric pusher 8 at the top of the negative pressure tank 2 to drive the pressure block 9, and utilizing the shape matching between the pressure block 9 and the inner cavity of the feeding box 4, it is ensured that the vulcanizable compound in a plastic state is uniformly squeezed and extruded from the slot 6 to form a sheet of uniform thickness, thus completing degassing. Subsequently, using the matching design of the same pressure block 9 and the inner cavity of the molding box 5, the stacked sheets are hot-pressed at high temperature, providing a suitable structure for the simultaneous completion of interlayer fusion and vulcanization crosslinking. By equipping an integrated vacuum device, a stable low vacuum environment is maintained inside the tank, providing a continuous pressure difference for bubble precipitation and preventing oxidation side reactions during high-temperature vulcanization. The overall equipment has a compact structure and smooth operation, realizing a continuous integrated operation of the entire process of "degassing-stacking-vulcanization", reducing manual intervention and intermediate transfer, and greatly improving production efficiency and product quality consistency.

[0053] During operation, the prepared vulcanizable compound containing vulcanizing agent but not crosslinked is added to the feeding box 4. Then, the feeding box 4 is pushed into the negative pressure tank 2 along the upper slide rail 3 and secured with quick-release buckles 26. Simultaneously, the molding box 5 is pushed into the corresponding position in the tank along the lower slide rail 3 and secured. After closing the sealing cover of the negative pressure tank 2, the heating and temperature control system is activated. First, the working area inside the tank is precisely controlled at the first temperature T1 (70-90℃). This temperature ensures the rubber compound softens and maintains good plasticity, while effectively inhibiting… The vulcanizing agent decomposes; the integrated vacuum device operates synchronously to maintain the pressure inside the tank at a low vacuum environment of -0.07 to -0.09 MPa; at this time, the electric push rod 8 at the top of the negative pressure tank 2 drives the pressure block 9 downward, and the pressure block 9 fits against the inner cavity of the feeding box 4, uniformly squeezing the plastic material and forcing it to be continuously extruded from the slots 6 of the bottom plate of the feeding box 4 to form thin sheets of 5 to 10 mm; the extruded sheets fall in the negative pressure environment, and the air bubbles inside are efficiently removed under the drive of the negative pressure difference due to their extremely short migration paths. The degassed sheets then fall into the forming box 5 below and are neatly stacked in sequence.

[0054] After the rubber compound in the feeding box 4 is completely extruded and formed into thin sheets stacked in the molding box 5, the equipment enters the next stage. The heating and temperature control system quickly raises the temperature of the working area inside the tank from T1 and precisely controls it at the second temperature T2 (160-180℃). This temperature will activate the vulcanizing agent. Then, the electric push rod 8 drives the pressure block 9 downward again, applying high pressure to the thin sheets of rubber compound stacked in the molding box 5 for hot pressing. Under the combined action of high temperature (T2) and high pressure, the sheet interface quickly softens, melts, and permeates and fuses with each other. At the same time, the vulcanization crosslinking reaction is triggered and completed rapidly during this hot pressing process, realizing the "dynamic vulcanization" molding effect, and finally forming a dense and fully vulcanized rubber block. After pressure holding and shaping, the pressure block 9 is reset, the temperature control system stops heating, the vacuum device stops working, and after restoring normal pressure, the sealing cover and quick-release lock 26 are opened, and the molding box 5 is pulled out along the slide 3 to remove the final low-odor EPDM rubber block.

[0055] In the above scheme, the required negative pressure environment is lower by making the adhesive into thin sheets, and the technical requirements for implementation are also lower. More importantly, the operation process requires the sealing cover of the negative pressure tank 2 to be opened continuously. The relatively lower negative pressure environment will result in less energy waste and save on implementation costs.

[0056] like Figure 7 , Figure 8 and Figure 9 As shown, in this embodiment, preferably, the bottom plate of the feeding box 4 is configured as an openable structure, including two templates 7 symmetrically and rotatably connected to the two sides of the bottom of the feeding box 4. A slot 6 is opened on the template 7. One end of the rotating shaft of the template 7 is fixedly connected to a worm gear 13. A transmission box 10 is fixedly connected to one side of the feeding box 4. Worms 11 are rotatably connected to both sides of the inner wall of the transmission box 10. A dual-axis motor 12 is fixedly connected to the side of the feeding box 4 near the transmission box 10. The output end of the dual-axis motor 12 is fixedly connected to the two worms 11 respectively. The worm gear 13 corresponds to and meshes with the worm 11.

[0057] In the above scheme, the bottom plate of the feeding box 4 is a fixed structure. After the pressing block 9 is extruded into a thin sheet, the feeding box 4 needs to be removed or moved to another position. Repeatedly opening the can not only wastes energy, but also easily introduces air during the process, causing secondary bubbles. In this embodiment, by setting the bottom of the feeding box 4 to be openable, the bottom of the feeding box 4 can be opened after the sheet is made, so that the pressing block 9 can pass through until it enters the forming box 5 for pressing and forming. This realizes the integrated operation of sheet making and compaction, avoids air mixing in during the operation, and further improves the degassing effect.

[0058] The bottom plate of the feeding box 4 is designed as an openable double template 7 structure. The two templates 7 are symmetrically rotated and connected to the bottom sides of the feeding box 4. When extruding to manufacture thin sheets, the dual-axis motor 12 drives the worm gear 11 to reverse, and through the meshing transmission of the worm wheel 13 and the worm gear 11, it drives the template 7 to close. The joint of the template 7 is tightly fitted, ensuring that the rubber material is only extruded from the slit 6. When it is necessary to compact the thin sheet, the dual-axis motor 12 rotates forward, and the worm gear 11 drives the worm wheel 13 to rotate, which in turn drives the two templates 7 to open to both sides. The opening completely avoids the stroke of the pressure block 9, so that the pressure block 9 can pass through the feeding box 4 and go directly down into the forming box 5 to compact the thin sheet. After the template 7 is opened, the slit 6 is fully exposed, which makes it easy for operators to clean up residual rubber. The self-locking characteristics of the worm wheel 13 and the worm gear 11 can also ensure the sealing when the template 7 is closed, preventing the rubber material from leaking from the joint during extrusion.

[0059] like Figure 2 , Figure 5 and Figure 6 As shown, in this embodiment, preferably, the negative pressure tank 2 has two side plates 20 symmetrically fixedly connected inside. Each side plate 20 has several scraping racks fixedly connected to it. The scraping racks correspond one-to-one with the slots 6. The scraping rack includes a mounting part 21 (specifically, multiple horizontal bars) connected to the side plate 20 and a scraping part 22 (specifically, a diagonal bar) connected to the mounting part 21. The width of the scraping part 22 matches the width of the slots 6. A guide platform 24 is fixedly connected to the top of the slide 3 located below. The top of the guide platform 24 has a slope, and the height of the guide platform 24 near the middle position is lower than the height of the periphery.

[0060] During the extrusion process, some rubber will remain in the groove 6 of the template 7 due to its stickiness. If it is not cleaned in time, it will cause uneven thickness of the extruded sheet and affect the degassing effect. At the same time, when the sheet falls from the opening of the template 7 to the forming box 5, it is easy to cause misalignment due to gravity, resulting in gaps between layers and residual air forming bubbles. In this embodiment, by fixing a scraper that matches the slot 6 to the side plate 20 of the negative pressure tank 2, the scraper 22 is inserted into the slot 6 when the template 7 is opened to thoroughly remove residual rubber, ensuring uniform sheet thickness and providing a stable path for bubble migration. By setting a guide platform 24 with an inclined surface at the top of the slide 3, the sheet is guided to slide along the inclined surface towards the center of the forming box 5, avoiding falling and deviation, and achieving neat stacking. The two work together to reduce bubble residue caused by uneven thickness and misalignment, improve the density of the rubber block, and reduce the frequency of manual cleaning, ensuring continuous operation of the equipment.

[0061] When the template 7 is opened, the scraping part 22 of the scraper rotates with the template 7 and is inserted into the slot 6 to scrape away the residual rubber, ensuring that the rubber material can pass evenly through the slot 6 during the next extrusion, forming a sheet of uniform thickness. The guide platform 24 located at the top of the lower slide 3 has a sloped top that is lower in the middle and higher at the periphery. After the sheet falls from the opening between the templates 7, it contacts the sloped surface of the guide platform 24 and slides along the sloped surface towards the center area of ​​the forming box 5 under the action of gravity, avoiding displacement during the fall, achieving neat stacking of the sheet and reducing the amount of air residue between layers.

[0062] like Figure 7 , Figure 8 and Figure 9 As shown, in this embodiment, preferably, the interior of the negative pressure tank 2 is fixedly connected to both sides of the slide 3 with support seats 14. A bidirectional screw 16 is rotatably connected between the inner sides of the support seats 14. Two sliders 17 are symmetrically threaded to the outside of the bidirectional screw 16. The sliders 17 are slidably connected to the support seats 14. A support rod 18 is hinged to one side of the slider 17. A support block 19 is hinged between the ends of the two support rods 18 away from the sliders 17. The tops of the support block 19 and the support rods 18 are in contact with the bottom of the template 7. A retraction motor 15 is fixedly installed on one side of the support seat 14. The output end of the retraction motor 15 is fixedly connected to one end of the bidirectional screw 16.

[0063] Because the bottom of the feeding box 4 is designed to be openable, and the feeding box 4 also needs to withstand a certain pressure, when the sheet is extruded, the pressure applied by the pressure block 9 will directly act on the template 7. Relying solely on the rotating shaft for support can easily cause the template 7 to deform, resulting in misalignment of the seam 6 and poor sealing at the joint of the template 7. This not only affects the sheet forming accuracy but may also lead to adhesive leakage. In this embodiment, a support structure consisting of a bidirectional screw 16, a slider 17, and a support rod 18 linked together is provided on both sides of the slide rail 3. When the template 7 is closed and compressed, the screw drives the slider 17 to slide towards each other, causing the support rod 18 to unfold. The support block 19 rises and presses against the bottom of the template 7, forming a stable support, dispersing pressure and preventing deformation. This ensures that the seams 6 are aligned and the joints are sealed, guaranteeing the sheet forming accuracy and preventing material leakage. When the template 7 is opened, the screw reverses, causing the support block 19 to descend and avoid obstruction, without affecting the opening and closing, thus improving the stability of equipment operation and the utilization rate of raw materials.

[0064] It should be noted that the above-mentioned auxiliary support structure is located below both sides of the feeding box 4, and will not interfere with the descent of the pressure block 9 or the extraction of the feeding box 4.

[0065] When the template 7 is closed in preparation for compression, the bidirectional screw 16 rotates, causing the two sliders 17 to slide towards each other along the support base 14. The sliders 17 push the support rod 18 to gradually unfold, and the support block 19 moves to the middle of the template 7. Both the support block 19 and the support rod 18 are in contact with the bottom of the template 7, which can form a stable multi-point support structure for the template 7, disperse the pressure applied by the pressure block 9, and prevent the template 7 from deforming. When it is necessary to open the template 7, the bidirectional screw 16 rotates in the opposite direction, the sliders 17 slide away from each other along the support base 14, the support rod 18 gradually retracts, and the support block 19 resets until it is detached from the template 7 from the side, making room for the template 7 to rotate and ensuring that the template 7 can open and close smoothly.

[0066] like Figure 4 , Figure 7 and Figure 8 As shown, in this embodiment, preferably, a plurality of vibrators 23 are fixedly installed on the side of the template 7 away from the feeding box 4; a chamfer 25 is provided on the side of the template 7 away from its rotation axis, and the chamfer 25 and the inclined surface of the top of the guide platform 24 are both 45°. The length of the template 7 is less than the distance between the bottom of the guide platform 24 and the rotation axis of the template 7, and greater than the distance between the top of the guide platform 24 and the rotation axis of the template 7.

[0067] In this embodiment, by setting a vibrator 23, the rubber material can move downwards with shaking when it is extruded through the slit 6. On the one hand, this promotes the precipitation of air bubbles, and on the other hand, it can cause the rubber material to fall downwards at the end of the extrusion. In addition, the template 7 is provided with a chamfer 25, and when the template 7 is flipped to the open state, the chamfer 25 surface is in contact with the inclined surface on the guide table 24. This allows the vibrator 23 to vibrate, which not only promotes the material to fall into the molding box 5, but also transmits the vibration through the physical contact mentioned above, causing the molding box 5 to shake, promoting the material to bond together, and allowing the material to fill the molding box 5 faster.

[0068] Preferably, the surfaces of the feeding box 4, forming box 5, pressing block 9, template 7 and rejecting rack are all provided with an anti-stick coating, which is a Teflon anti-stick coating.

[0069] In this embodiment, by applying a Teflon anti-stick coating to all locations that can come into contact with the adhesive, the entire process from adhesive input, extrusion into thin sheets, stacking and compaction to cleaning of the seams 6 is reduced, which not only improves the working efficiency of each component, but also ensures the stability of product quality, while reducing the cleaning cost and downtime of the equipment.

[0070] The present invention has been described in detail above. However, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, any modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A process for preparing low-odor EPDM rubber, characterized in that, Includes the following steps: S1. Mixing: Mix the raw EPDM rubber, compounding agents and vulcanizing agents to obtain a uniform vulcanizable compound. S2. Negative pressure sheeting and degassing: The vulcanizable compound is placed in a closed negative pressure environment and mechanically extruded into a sheet at a first temperature T1. The sheet shape and negative pressure work together to remove air bubbles. The first temperature T1 is higher than the softening temperature of the rubber compound but lower than the rapid vulcanization start temperature of the vulcanization system used. S3. Hot-press vulcanization molding: Under the condition of maintaining negative pressure or inert environment, the degassed sheet rubber material is stacked, and then the temperature is raised to a second temperature T2, and pressure is applied at temperature T2 for hot pressing; the second temperature T2 is higher than the first temperature T1, and reaches the temperature range in which the vulcanization system undergoes a rapid cross-linking reaction, so that the vulcanization cross-linking reaction of the rubber material is completed simultaneously with the hot-press molding process, resulting in a dense vulcanized rubber block; S4. Post-processing: Cooling, unloading and packaging the rubber block.

2. The preparation process of low-odor EPDM rubber according to claim 1, characterized in that: In step S4, the thickness of the sheet-like adhesive is 5-10 mm; the sealed negative pressure environment is a low vacuum environment, with the vacuum degree controlled at -0.07 to -0.09 MPa; the first temperature T1 is 70℃ to 90℃; and the second temperature T2 is 160℃ to 180℃.

3. The process for preparing low-odor EPDM rubber according to claim 1, characterized in that: The vulcanizing agent is a peroxide vulcanizing agent, and the first temperature T1 is lower than the decomposition temperature of the peroxide vulcanizing agent.

4. A low-odor EPDM rubber preparation equipment, characterized in that: The process for preparing low-odor EPDM rubber according to any one of claims 1-3 is applicable; comprising: Frame (1); The negative pressure tank (2) is fixedly installed on the frame (1). A sealable cover is provided on one side of the negative pressure tank (2). The negative pressure tank (2) is equipped with a heating and temperature control system to ensure that the working area inside the tank reaches and is maintained at the first temperature T1 or the second temperature T2. Slides (3) are symmetrically fixedly connected to the upper and lower parts of the negative pressure tank (2). The feeding box (4) is slidably connected to the slide (3) on the upper part of the negative pressure tank (2) and is used to feed vulcanizable compound rubber. The bottom plate of the feeding box (4) has several parallel slots (6). The extrusion component, used for extruding rubber material, includes an electric push rod (8) fixedly mounted on the top of the negative pressure tank (2), the movable end of which extends into the interior of the negative pressure tank (2) and is fixedly connected to a pressure block (9), the shape of which matches the inner cavity shape of the feeding box (4); The molding box (5) is slidably connected to the slide (3) at the bottom of the negative pressure tank (2) and is used to receive the extruded sheet-like rubber material. The inner cavity shape of the molding box (5) matches the shape of the pressing block (9). The molding box (5) and the feeding box (4) are both fixed to the negative pressure tank (2) by quick-release buckles (26).

5. The low-odor EPDM rubber preparation equipment according to claim 4, characterized in that: The bottom plate of the feeding box (4) is designed to be openable, including two templates (7) symmetrically and rotatably connected to the bottom sides of the feeding box (4). The slot (6) is opened on the template (7). One end of the rotating shaft of the template (7) is fixedly connected to a worm gear (13). A transmission box (10) is fixedly connected to one side of the feeding box (4). Worms (11) are rotatably connected to both sides of the inner wall of the transmission box (10). A dual-axis motor (12) is fixedly connected to the side of the feeding box (4) near the transmission box (10). The output end of the dual-axis motor (12) is fixedly connected to the two worms (11) respectively. The worm gear (13) corresponds to and meshes with the worm (11).

6. The low-odor EPDM rubber preparation equipment according to claim 5, characterized in that: The negative pressure tank (2) has two side plates (20) fixedly connected symmetrically inside. Several scraping racks are fixedly connected on both side plates (20). The scraping racks correspond one-to-one with the slots (6). The scraping racks include an installation part (21) and a scraping part (22). The width of the scraping part (22) matches the width of the slots (6). A guide platform (24) is fixedly connected to the top of the slide (3) below. The top of the guide platform (24) has a slope, and the height of the guide platform (24) near the middle position is lower than the height of the periphery.

7. The low-odor EPDM rubber preparation equipment according to claim 6, characterized in that: Inside the negative pressure tank (2), there are fixed support seats (14) on both sides of the slide (3). A double screw (16) is rotatably connected between the inner sides of the support seats (14). Two sliders (17) are symmetrically threaded on the outside of the double screw (16). The sliders (17) are slidably connected to the support seats (14). A support rod (18) is hinged to one side of the slider (17). A support block (19) is hinged between the ends of the two support rods (18) away from the sliders (17). The tops of the support block (19) and the support rods (18) are in contact with the bottom of the template (7). A retraction motor (15) is fixedly installed on one side of the support seat (14). The output end of the retraction motor (15) is fixedly connected to one end of the double screw (16).

8. The low-odor EPDM rubber preparation equipment according to claim 7, characterized in that: Several vibrators (23) are fixedly installed on the side of the template (7) away from the feeding box (4); a chamfer (25) is provided on the side of the template (7) away from its rotation axis. The chamfer (25) and the inclined surface of the top of the guide platform (24) are both 45°. The length of the template (7) is less than the distance between the bottom of the guide platform (24) and the rotation axis of the template (7), and greater than the distance between the top of the guide platform (24) and the rotation axis of the template (7).

9. The low-odor EPDM rubber preparation equipment according to claim 8, characterized in that: The surfaces of the feeding box (4), forming box (5), pressing block (9), template (7) and rejecting rack are all provided with an anti-stick coating, which is a Teflon anti-stick coating.

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