Mixing system for producing polyurethane elastomer

Abstract

The utility model belongs to the technical field of polyurethane elastomer production, and particularly relates to a mixing system for producing a polyurethane elastomer. Comprising a plurality of raw material storage tanks which are arranged in parallel pairwise, the bottoms of the raw material storage tanks which are connected in parallel pairwise are communicated through communicating pipes, the tops of the raw material storage tanks which are connected in parallel pairwise are communicated through nitrogen-sealed balance pipes, and the communicating pipes and the nitrogen-sealed balance pipes are provided with valves; the two-position three-way plug valve arranged on the discharging pipe is connected to the metering pump and then connected to the pouring machine, the pouring machine is connected with the extruder, and the flow guide mechanism is arranged at the bottom in the raw material storage tank. And the available storage volume of each type of raw materials is directly doubled, so that the raw material guarantee capability of single-batch production and the buffer capability on supply fluctuation are improved. The flow guide mechanism is arranged to force the materials to sweep over each part of the tank bottom during flowing, so that the raw materials in the tank can be discharged without residues basically.

Description

Technical Field

[0001] This utility model belongs to the field of polyurethane elastomer production technology, specifically relating to a mixing system for producing polyurethane elastomers. Background Technology

[0002] In the production of polyurethane elastomers, raw materials such as MDI, small molecule alcohols, and polyols need to be precisely metered and mixed under heating conditions. Existing raw material supply systems typically use a single raw material storage tank in conjunction with a metering pump for feeding. When the storage tank requires maintenance or cleaning, the entire production line must be shut down, leading to production interruptions and low efficiency.

[0003] To improve continuity, the industry has adopted a simple parallel standby tank design. However, this design has significant drawbacks: First, the standby tank is usually in a "cold standby" state, with different temperature, pressure, and material conditions than the main tank. Before switching, it must undergo preheating, pressurization, and homogenization processes, making instant switching impossible and essentially still requiring a shutdown window. Second, the existing tank bottom structure is prone to creating dead zones at low liquid levels when dealing with high-viscosity, easily crystallizing polyurethane raw materials, leading to material residue. This not only wastes raw materials and causes proportioning errors, but the crystallized residue can also clog pipelines, increasing maintenance burden. Finally, simple parallel connection does not effectively expand usable volume, and the switching operation is cumbersome, requiring the operation of multiple valves and posing a risk of misoperation.

[0004] Therefore, existing technologies lack a polyurethane raw material mixing system that can achieve rapid, seamless online switching, completely eliminate tank bottom residue, and has a standardized and safe operating procedure. Utility Model Content

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a mixing system for producing polyurethane elastomers.

[0006] The mixing system for producing polyurethane elastomers according to this utility model includes several raw material storage tanks arranged in parallel in pairs. The bottoms of the parallel raw material storage tanks are connected by a connecting pipe, and the tops are connected by a nitrogen-sealing balance pipe. Both the connecting pipe and the nitrogen-sealing balance pipe are equipped with valves. The bottoms of the parallel raw material storage tanks are equipped with discharge pipes that are connected to the discharge port. A two-position three-way stopcock valve on the discharge pipe is connected to a metering pump, which is then connected to a casting machine. The casting machine is connected to an extruder. The bottom of the raw material storage tank is equipped with a flow guiding mechanism to guide the material to the discharge port and prevent sedimentation.

[0007] The raw material storage tanks are connected at the bottom by a connecting pipe and at the top by a nitrogen-sealed balance pipe. This ensures that the pressure of the two tanks in any parallel tank group remains consistent during operation, and that the internal materials can flow between them and the liquid levels are synchronized.

[0008] By operating a two-position three-way stopcock valve, it is possible to select that only one of the raw material storage tanks supplies material to the metering pump, while the other tank can be isolated online for maintenance or feeding.

[0009] Each of the two parallel raw material storage tanks is equipped with a jacket, and the jacket is connected to the vacuum heat transfer oil furnace through a connected heat transfer oil pipeline.

[0010] The flow guiding mechanism includes at least two concentric annular flow guiding plates disposed at the bottom of the raw material storage tank, and each annular flow guiding plate has a flow passage hole at its bottom.

[0011] The flow holes are staggered circumferentially on adjacent annular guide plates. This design forces the material to flow around the tank in a circumferential manner instead of falling in a straight line, thus thoroughly sweeping over every corner of the tank bottom and achieving discharge without dead zones.

[0012] The height of the annular guide plate decreases sequentially from near the raw material storage tank wall towards near the discharge port.

[0013] When the liquid level is high, all the annular baffles are submerged in the raw material, allowing the fluid to flow freely. The situation changes when the liquid level drops to the point where the upper edge of the outermost annular baffle is about to be exposed: the remaining raw material is contained within the annular area between the baffle and the tank wall. At this point, the only outlet for the raw material to flow out of this area is the flow hole at the bottom of the outermost annular baffle. This forces all the raw material within this annular area, regardless of its viscosity, to converge and flow out through the flow hole. As the raw material in this area is about to be emptied, the liquid level drops to the upper edge of the middle annular baffle. This decreasing height ensures that the annular baffles are exposed sequentially from top to bottom and from outside to inside, allowing them to function in sequence. If all the annular baffles were the same height, they would all be exposed simultaneously, losing their segmented guidance and gradual emptying function, significantly reducing the residue prevention effect. This design, combined with the staggered flow holes that force the raw material to flow around within each ring, ensures thorough emptying.

[0014] The function of the annular deflector with its decreasing height is:

[0015] As the raw material level decreases from high to low, it acts like several annular dams of different heights, dividing the bottom of the tank into several annular areas. The raw material in each area is forced to flow out through the flow hole at its bottom, thus achieving thorough emptying from the outside to the inside, ring by ring, eliminating any residue in any corner.

[0016] A honeycomb rectifier is fixedly installed in the internal channel of the discharge port.

[0017] The honeycomb rectifier can organize the potentially turbulent material from the flow guiding mechanism into a smooth laminar flow before it enters the discharge pipe, thereby providing stable feeding conditions for the downstream metering pump and improving metering accuracy.

[0018] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0019] (1) This utility model realizes safe and standardized online hot switching and zero-downtime maintenance. Through the combination of "normally open connecting valve + two-position three-way plug valve" and the clear "close isolation - venting - switching" operation process, not only is uninterrupted production achieved, but also the safety and standardization of maintenance operations are ensured, and the risk of misoperation is eliminated.

[0020] (2) By designing two parallel storage tanks connected by a connecting pipe, this utility model not only provides thermal backup capability, but also directly doubles the available storage volume of each type of raw material, significantly improving the raw material guarantee capability for single batch production and the buffer capability against supply fluctuations.

[0021] (3) The clear physical isolation point connecting pipe valve and switching point plug valve between the storage tanks of this utility model make the system status clear at a glance, the maintenance logic simple and clear, reduce the complexity of operation, and improve the long-term operation reliability and maintainability of the entire mixing system.

[0022] (4) By combining the stepped annular guide plate with the staggered flow holes, the material is forced to flow across every part of the tank bottom, which can discharge the raw material in the tank with basically no residue. For the last remaining high-viscosity liquid, the guide structure can provide effective guidance and solve the industry problem of raw material sticking to the bottom of the tank and not flowing when the liquid level is low. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of the present invention, form part of this invention. In the drawings:

[0024] Figure 1 This is a schematic diagram of the mixing system for producing polyurethane elastomers according to the present invention.

[0025] Figure 2 This is a schematic diagram of the storage tank structure;

[0026] Figure 3 This is a top view of the flow guiding mechanism at the bottom of the storage tank.

[0027] In the picture:

[0028] 1. First MDI storage tank; 2. Second MDI storage tank; 3. First small molecule alcohol storage tank; 4. Second small molecule alcohol storage tank; 5. First polyol storage tank; 6. Second polyol storage tank; 7. MDI storage tank nitrogen blanketing balance pipe; 8. Small molecule alcohol storage tank nitrogen blanketing balance pipe; 9. Polyol storage tank nitrogen blanketing balance pipe; 10. MDI storage tank discharge pipe; 1001. MDI two-position three-way stopcock valve; 11. Small molecule alcohol storage tank discharge pipe; 1101. Small molecule alcohol two-position three-way stopcock valve; 12. Polyol storage tank discharge pipe; 1201. Polyol two-position three-way stopcock valve; 13. MDI metering pump; 14. Small molecule alcohol metering pump; 15. Polyol metering pump; 16. Casting machine; 17. Extruder; 18. Vacuum heat transfer oil furnace; 19. MDI storage tank heat transfer oil pipeline; 20. Small molecule alcohol storage tank heat transfer oil pipeline; 21. Polyol storage tank heat transfer oil pipeline; 22. First annular guide plate; 23. Second annular guide plate; 24. Third annular guide plate; 25. Feed port; 26. Honeycomb rectifier; 27. MDI connecting pipe; 28. Small molecule alcohol connecting pipe; 29. ​​Polyol connecting pipe. Detailed Implementation

[0029] The present invention will be explained in detail below with reference to the embodiments.

[0030] Example 1

[0031] The mixing system for producing polyurethane elastomers, as shown in the attached figure... Figure 1-3 As shown, the raw material storage tanks are set up in parallel in pairs, specifically including: the first MDI storage tank 1 and the second MDI storage tank 2 are connected in parallel, the first small molecule alcohol storage tank 3 and the second small molecule alcohol storage tank 4 are connected in parallel, and the first polyol storage tank 5 and the second polyol storage tank 6 are connected in parallel.

[0032] To achieve pressure and material balance between the parallel tanks, dedicated connecting pipes are installed at the top and bottom of each pair of parallel tanks. The tops of the first MDI tank 1 and the second MDI tank 2 are connected via the MDI tank nitrogen-sealing balance pipe 7, and their bottoms are connected via the MDI connecting pipe 27. Similarly, the first small molecule alcohol tank 3 and the second small molecule alcohol tank 4 are connected via the small molecule alcohol tank nitrogen-sealing balance pipe 8 and the small molecule alcohol connecting pipe 28; the first polyol tank 5 and the second polyol tank 6 are connected via the polyol tank nitrogen-sealing balance pipe 9 and the polyol connecting pipe 29. This ensures that the pressure of the two tanks in any parallel tank group remains consistent during operation, and that the internal materials can flow between them, with synchronized liquid levels. Normally open valves are installed on both the connecting pipes and the nitrogen-sealing balance pipes.

[0033] Each raw material storage tank has a discharge port 25 at its bottom. This discharge port 25 is connected to a discharge pipe; for example, the discharge ports 25 of the first MDI storage tank 1 and the second MDI storage tank 2 are both connected to the MDI storage tank discharge pipe 10. An MDI two-position three-way stopcock valve 1001 is installed on the MDI storage tank discharge pipe 10. The two inlets of the MDI two-position three-way stopcock valve 1001 are respectively connected to the branches of the first MDI storage tank 1 and the second MDI storage tank 2, and its outlet leads to the MDI metering pump 13. By operating the MDI two-position three-way stopcock valve 1001, it is possible to select that only the first MDI storage tank 1 or the second MDI storage tank 2 supplies material to the MDI metering pump 13, while the other tank can be isolated online for maintenance or feeding. The pipeline connection method for small molecule alcohols and polyols is exactly the same. The discharge pipes 11 of the small molecule alcohol storage tanks at the bottom of the first small molecule alcohol storage tank 3 and the second small molecule alcohol storage tank 4 are respectively connected to the small molecule alcohol metering pump 14 through the small molecule alcohol two-position three-way stopcock valve 1101. The discharge pipes 12 of the polyol storage tanks at the bottom of the first polyol storage tank 5 and the second polyol storage tank 6 are connected to the polyol metering pump 15 through the polyol two-position three-way stopcock valve 1201.

[0034] Each metering pump delivers precisely metered raw materials to the casting machine 16 for high-speed mixing and reaction, and then into the extruder 17 for molding.

[0035] The entire system is heated by a vacuum thermal oil heater 18. Each raw material storage tank is equipped with a jacket, which is connected to the vacuum thermal oil heater 18 via thermal oil pipelines, forming a circulating heating loop. Specifically, these are: thermal oil pipeline 19 for the MDI storage tank, thermal oil pipeline 20 for the small molecule alcohol storage tank, and thermal oil pipeline 21 for the polyol storage tank. To avoid cluttered lines, the return pipeline is not shown in the diagram. Each raw material transport pipeline is also equipped with a heating layer to prevent the raw materials from cooling during transport. The vacuum thermal oil heater 18 controls the temperature of each pair of parallel raw material storage tanks to be consistent, ensuring the stability of the raw material temperature during seamless switching in the production process.

[0036] Each raw material storage tank is equipped with a flow guiding mechanism inside. This mechanism is located at the bottom of the tank and is used to guide the material flow to the feed inlet 25 to prevent sedimentation. Figure 2 and Figure 3As shown, the tank is equipped with a first annular guide plate 22, a second annular guide plate 23, and a third annular guide plate 24. The height of these guide plates decreases sequentially from near the tank wall towards the discharge port 25, forming a stepped shape. Each annular guide plate has flow holes at its bottom, and crucially, these flow holes are staggered circumferentially on adjacent annular guide plates. For example, the flow holes on the second annular guide plate 23 are not on the same radial line as those on the first and third annular guide plates 22 and 24. This design forces the material to flow around the tank circumferentially within the annular area formed by the adjacent guide plates, rather than falling in a straight line, thus thoroughly sweeping every corner of the tank bottom and achieving discharge without dead zones.

[0037] A honeycomb rectifier 26 is fixedly installed in the internal channel of the discharge port 25. The honeycomb rectifier 26 can organize the potentially turbulent material from the flow guiding mechanism into a stable laminar flow before it enters the discharge pipe, thereby providing stable feeding conditions for the downstream metering pump and improving metering accuracy.

[0038] The detailed operating procedure is as follows:

[0039] Normal hot standby status:

[0040] Taking the MDI system as an example, the MDI two-position three-way stopcock valve 1001 is set to connect to the first MDI storage tank 1, which serves as the main feed tank. The normally open valve on the MDI connecting pipe 27 and the valve on the nitrogen-sealing balance pipe 7 of the MDI storage tank are both in the open state. At this time, the first MDI storage tank 1 and the second MDI storage tank 2 form a connected whole system through the bottom MDI connecting pipe 27 and the top MDI storage tank nitrogen-sealing balance pipe 7. The liquid levels of the two tanks are always kept consistent through the principle of the communicating vessels, and the materials can be freely complemented. This not only prepares for switching but also substantially doubles the total storage volume, providing a greater buffer to cope with large-scale production or raw material replenishment cycles. In this state, the raw material is guided by the flow guiding mechanism inside the tank and stabilized by the honeycomb rectifier 26, and pumped out from the discharge port 25 through the MDI storage tank discharge pipe 10 by the MDI metering pump 13. When the material is discharged from the bottom of the tank, it is guided by the stepped first annular guide plate 22, the second annular guide plate 23, and the third annular guide plate 24 with staggered flow holes, forming an orderly swirling flow, completely emptying the tank without any residue. Subsequently, after the material is stabilized by the honeycomb rectifier 26, it is precisely delivered to the casting machine 16 by the metering pump.

[0041] Switching and maintenance operation procedures:

[0042] When maintenance is required on the main feed tank: MDI storage tank 1, follow the standardized procedure below:

[0043] First, close the normally open valve on the MDI connecting pipe 27 to isolate the first MDI storage tank 1 from the second MDI storage tank 2 at the material level. Continue running the MDI metering pump 13. Since the MDI two-position three-way stopcock valve 1001 is still connected to the first MDI storage tank 1, the remaining material in the tank will be completely pumped to the production line. After the first MDI storage tank 1 is emptied, operate the MDI two-position three-way stopcock valve 1001 to switch its path from the first MDI storage tank 1 to the second MDI storage tank 2. At this point, the material supply source has been seamlessly switched, and production has never been interrupted. At this time, the material in the first MDI storage tank 1 has been emptied and isolated from the system, and it is safe to clean, inspect, or maintain it. The second MDI storage tank 2 becomes the new main supply tank.

Claims

1. A mixing system for producing polyurethane elastomers, characterized in that, It includes several raw material storage tanks arranged in parallel. The bottom of the two parallel raw material storage tanks is connected by a connecting pipe, and the top is connected by a nitrogen sealing balance pipe. Both the connecting pipe and the nitrogen sealing balance pipe are equipped with valves. The bottom of the two parallel raw material storage tanks is equipped with a discharge pipe connected to the discharge port (25). The discharge pipe is connected to a metering pump through a two-position three-way stopcock valve, and then connected to a casting machine (16). The casting machine (16) is connected to an extruder (17). The bottom of the raw material storage tank is equipped with a flow guiding mechanism.

2. The mixing system for producing polyurethane elastomers according to claim 1, characterized in that, Each of the two parallel raw material storage tanks is equipped with a jacket, and the jacket is connected to the vacuum heat transfer oil furnace (18) through a connected heat transfer oil pipeline.

3. The mixing system for producing polyurethane elastomers according to claim 1, characterized in that, The flow guiding mechanism includes at least two concentric annular flow guiding plates disposed at the bottom of the raw material storage tank, and each annular flow guiding plate has a flow passage hole at its bottom.

4. The mixing system for producing polyurethane elastomers according to claim 3, characterized in that, The flow holes are arranged circumferentially staggered on adjacent annular guide plates.

5. The mixing system for producing polyurethane elastomers according to claim 4, characterized in that, The height of the annular guide plate decreases sequentially from near the raw material storage tank wall to near the discharge port (25).

6. The mixing system for producing polyurethane elastomers according to claim 1, characterized in that, A honeycomb rectifier (26) is fixedly installed in the internal channel of the discharge port (25).

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