Preparation system of rigid polyurethane foam
By using static premixing and high-pressure counter-mixing in a rigid polyurethane foam preparation system, the challenges of flexibility and customization in the preparation process of rigid polyurethane foam have been solved, enabling efficient and customized production of polyurethane foam and improving production flexibility and quality stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- WANHUA CHEM NINGBO RONGWEI POLYURETHANE
- Filing Date
- 2025-05-09
- Publication Date
- 2026-05-19
AI Technical Summary
Rigid polyurethane foam presents challenges in terms of flexibility and customization during its preparation, especially in refrigerator manufacturing where high raw material stability is required and the process for changing performance is cumbersome, leading to raw material waste.
A rigid polyurethane foam preparation system was designed, including a supply unit, a premixing device, and a mixing and dispensing device. The system achieves high-pressure counter-mixing by statically premixing polyurethane additives with combined polyethers or isocyanates, and the combination ratio can be flexibly adjusted by a supply quantity regulating device to ensure customized production of polyurethane foam.
It improves the production flexibility and quality stability of polyurethane foam, meets the diverse needs of different customers, reduces raw material waste, and achieves efficient customized production.
Smart Images
Figure CN224252664U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of polyurethane foam technology, and in particular to a system for preparing rigid polyurethane foam. Background Technology
[0002] Rigid polyurethane (PU) foam is one of the main types of polyurethane synthetic materials. It is a foam plastic made by reacting polyether polyols or polyester polyols with isocyanates to form the polyurethane matrix, and then reacting the isocyanates with water or low-boiling-point chlorofluorocarbon (CFC) blowing agents. It is a low-density microporous polymer material with a closed-cell structure and excellent overall performance. As a refrigerator insulation material, it has advantages such as low density, low thermal conductivity, high compressive strength, good adhesion, and ease of processing. Currently, rigid polyurethane foam is widely used not only in the refrigeration industry but also in furniture, construction, packaging, and insulation materials.
[0003] Rigid polyurethane foam is produced by a series of chemical reactions between a polyether polyol and isocyanate in the presence of a catalyst, surfactant, foaming agent, and other additives. Generally, before the reaction, the additives are added to the polyether polyol and mixed thoroughly to form a polyether. The polyether is then mixed evenly with the isocyanate using a high-pressure foaming machine before being filled into the refrigerator cavity. Because refrigerator manufacturing is a continuous production process, the stability of raw materials is crucial. This leads to cumbersome procedures for temporary performance changes and a high risk of material waste. Therefore, the flexibility and customization of rigid polyurethane foam preparation have gradually become a challenge in the industry. Utility Model Content
[0004] Therefore, this utility model proposes a preparation system for customized production of rigid polyurethane foam.
[0005] To address the aforementioned technical problems, this utility model provides the following technical solution:
[0006] A rigid polyurethane foam preparation system includes: a first supply unit, a second supply unit, a third supply unit, a premixing device, and a mixing and dispensing device; wherein, one of the first and second supply units is used to supply a composite polyether; the other of the first and second supply units is used to supply isocyanate; the third supply unit is used to supply polyurethane additives; at least one of the first and second supply units is provided with a supply amount adjustment device; the output terminals of the first and third supply units are connected to the input terminal of the premixing device; the output terminals of the premixing device and the second supply unit are connected to the input terminal of the mixing and dispensing device; and the output terminal of the mixing and dispensing device is connected to the product to be dispensed.
[0007] In some embodiments of this utility model, the first supply unit includes a first circulating supply pipeline and a first supply container, a first switching valve, and a first metering pump disposed on the first circulating supply pipeline. The first switching valve is used to switch the flow direction of the material passing through the outlet of the first metering pump.
[0008] In some embodiments of this utility model, the first supply unit further includes a first compressor and a first temperature regulating device connected to the first supply container. The first compressor is used to deliver high-pressure gas to the first supply container; the first temperature regulating device is used to exchange heat with the first supply container to regulate its internal temperature.
[0009] In some embodiments of this utility model, the first switching valve is a pneumatically controlled distribution valve, which includes a first working position and a second working position. When the first switching valve is in the first working position, the material in the first supply container circulates inside the first circulating supply pipeline. When the first switching valve is in the second working position, the material in the first supply container is supplied to the premixing device via a first metering pump.
[0010] In some embodiments of this utility model, the second supply unit includes a second circulating supply pipeline, a second supply container, a second switching valve, and a second metering pump disposed on the second circulating supply pipeline. The second metering pump is used to adjust the supply amount of the second supply unit, and the second switching valve is used to switch the flow direction of the material through the outlet of the second metering pump.
[0011] In some embodiments of this utility model, the second supply unit further includes a second compressor and a second temperature regulating device connected to the second supply container. The second compressor is used to deliver high-pressure gas to the second supply container, and the second temperature regulating device is used to exchange heat with the second supply container to regulate its internal temperature.
[0012] In some embodiments of this utility model, the second switching valve is a pneumatically controlled distribution valve, which includes a first working position and a second working position. When the second switching valve is in the first working position, the material in the second supply container circulates inside the second circulating supply pipeline. When the second switching valve is in the second working position, the material in the second supply container is supplied to the mixing and dispensing device via the second metering pump.
[0013] In some embodiments of this utility model, the third supply unit includes a third circulation supply pipeline, a third supply container disposed on the third circulation supply pipeline, a third switching valve, and a third metering pump. The third switching valve is a pneumatically controlled distribution valve, which includes a first working position and a second working position. When the third switching valve is in the first working position, the material in the third supply container circulates inside the third circulation supply pipeline. When the third switching valve is in the second working position, the material in the third supply container is supplied to the premixing device via the third metering pump.
[0014] In some embodiments of this utility model, the third supply container is a high-pressure supply container with a pressure value greater than 10 MPa, a pressure regulating valve is provided on the third circulation supply pipeline, and a pressure relief device is provided on the third supply container.
[0015] In some embodiments of this utility model, the third supply unit further includes a third temperature regulating device connected to the third supply container, the third temperature regulating device being used to exchange heat with the third supply container to regulate its internal temperature.
[0016] The technical solution of this utility model has the following technical advantages over the prior art:
[0017] The rigid polyurethane foam preparation system provided by this invention utilizes a premixing device to statically premix polyurethane additives with combined polyethers or isocyanates. This premixing is then introduced into a mixing and dispensing device for high-pressure counter-mixing of the combined polyethers and isocyanates, generating rigid polyurethane foam. This effectively solves the problem of reactions between additives and materials, thereby improving foam performance. Simultaneously, at least one of the first and second supply units is equipped with a supply rate adjustment device to regulate the supply ratio of combined polyethers and isocyanates, ensuring stable quality and expected performance of the produced polyurethane foam, thus enabling customized production of rigid polyurethane foam. Attached Figure Description
[0018] The preferred embodiments of this utility model will be described in detail below with reference to the accompanying drawings, which will help to understand the purpose and advantages of this utility model, wherein:
[0019] Figure 1 A system configuration diagram of the rigid polyurethane foam preparation system provided by this utility model. Detailed Implementation
[0020] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.
[0021] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0022] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.
[0023] Furthermore, the technical features involved in the different embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.
[0024] like Figure 1 The diagram illustrates a specific embodiment of the rigid polyurethane foam preparation system provided by this invention. The system includes a first supply unit 10, a second supply unit 20, a third supply unit 30, a premixing device 40, and a mixing and dispensing device 50. The first supply unit 10 and the second supply unit 20 are responsible for supplying the combined polyether and isocyanate, respectively, while the third supply unit 30 supplies polyurethane additives. Before the combined polyether and isocyanate are mixed under high pressure, the premixing device 40 mixes the polyurethane additives into the combined polyether pipeline or the isocyanate. Furthermore, by providing a supply quantity adjustment device in at least one of the first supply unit 10 and the second supply unit 20, the supply quantity can be flexibly adjusted to change the ratio when producing specific product models, achieving customized production of polyurethane foam. This design makes the entire preparation process more flexible and efficient, meeting the diverse performance requirements of different customers for polyurethane foam.
[0025] Specifically, the combined polyether comprises 62.5-85.8 parts of a combined polyether polyol, 1.2-4.0 parts of a surfactant, 1.5-5.5 parts of a combined catalyst, 1.5-3.0 parts of water, and 10-25 parts of a blowing agent; the surfactant is a silicone surfactant, preferably an organosilicon surfactant; the combined catalyst includes one or more of pentamethyldiethylenetriamine, tetramethylhexanediamine, bis-dimethylaminoethyl ether, dimethylbenzylamine, dimethylcyclohexane, triethylenediamine, methylimidazole, potassium formate, potassium acetate, quaternary ammonium salts, and tris(dimethylaminopropyl)hexahydrotriazine; the blowing agent includes cyclohexanediamine... One or more of the following: pentane (CP), isopentane (IP), n-pentane (NP), n-butane (R600), isobutane (R600a), 1,1,1,3,3-pentafluoropropane (HFC-245fa), 1-chloro,3,3,3-trifluoropropene (HFO-1233zd), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1-difluoroethane (HFC-152a), cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336MZZ), and 1,3,3,3-tetrafluoropropene (HFO-1234ZE). The combined polyether polyols include: polyether polyol A (10-35 parts, hydroxyl value 370-470 mgKOH / g), prepared by addition reaction of sucrose and propylene oxide; polyether polyol B (10-30 parts, hydroxyl value 320-420 mgKOH / g), prepared by addition reaction of sorbitol and glycerol and propylene oxide; polyether polyol C (15-30 parts, hydroxyl value 490-610 mgKOH / g), prepared by addition reaction of o-toluenediamine and propylene oxide; and polyether polyol D (5-15 parts, hydroxyl value 100-350 mgKOH / g), prepared by addition reaction of propylene glycol and propylene oxide.
[0026] The polyisocyanate is polymeric MDI, preferably polymeric MDI with an NCO content of 30-32%; more preferably, it is one or more of polymeric MDI Wanhua PM-200, polymeric MDI Wanhua PM-2010 and polymeric MDI Wanhua PM-400.
[0027] The polyurethane additives include one or more substances selected from polyurethane catalysts, surfactants, foaming agents, perfluorinated additives, organic acids, color pastes, and polyether polyols, or mixtures of different categories. The polyurethane catalyst contains one or more amine or metal catalysts, including pentamethyldiethylenetriamine, tetramethylhexanediamine, bis-dimethylaminoethyl ether, dimethylbenzylamine, dimethylcyclohexane, triethylenediamine, methylimidazole, potassium formate, potassium acetate, quaternary ammonium salts, tris(dimethylaminopropyl)hexahydrotriazine, etc. The surfactant is a silicone surfactant, preferably one or more organosilicon surfactants, such as Momentive's L6863, L6900, Y16148, etc.; Evonik Degussa's B8461, B8462, B8481, B84806, etc.; M-8805, M-8815, M-8830, M-8860, M-88310, M-88108, etc.; and Stellate's SD-613, SD-624, SD-625, SD-638, etc.; the foaming agent is a physical foaming agent, preferably cyclopentane (CP), isopentane (IP), n-pentane (NP), n-butane (R600), isobutane (R600a), 1,1,1,3,3-pentafluoropropane (HFC-245fa), 1-chloro,3- The polyether polyol is selected from one or more of the following: 3,3-trifluoropropylene (HFO-1233zd), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1-difluoroethane (HFC-152a), cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336MZZ), and 1,3,3,3-tetrafluoropropylene (HFO-1234ZE); the perfluorinated additive is preferably one or more of the following: 3M-5056, FA-188, and Noah 2100B; the polyether polyol is preferably a sucrose initiator polyether polyol, a sorbitol initiator polyether polyol, a glycerol initiator polyether polyol, an o-TDA initiator polyether polyol, a propylene glycol initiator polyether polyol, a diethylene glycol initiator polyether polyol, and mixed initiator polyether polyols.
[0028] Specifically, the first supply unit 10 includes a first circulating supply pipeline 11, a first supply container 12, a first switching valve 18, and a first metering pump 13 located on the first circulating supply pipeline 11. The first supply container 12 is used to store the combined polyether or isocyanate (depending on its set function in the system). The first metering pump 13 can precisely control the liquid flow rate output from the first supply container 12. Precise flow control is crucial to ensuring the accuracy of the proportions of each raw material during the preparation process, thereby ensuring that the produced polyurethane foam has stable quality and meets expected performance. Furthermore, flow sensors 14 are respectively installed on the inlet and outlet pipelines of the first metering pump 13 to detect the real-time flow rate on the first circulating supply pipeline 11, so as to precisely control the pumping volume of the first metering pump 13.
[0029] Specifically, the first switching valve 18 is used to switch the flow direction of material through the outlet of the first metering pump 13. The first switching valve 18 is a pneumatically controlled distribution valve, that is, it is connected to a pneumatic system to realize the switching of working positions, including a first working position and a second working position. When the first switching valve 18 is in the first working position, the material in the first supply container 12 circulates inside the first circulating supply pipeline 11; when the first switching valve 18 is in the second working position, the material in the first supply container 12 is supplied to the premixing device 40 via the first metering pump 13.
[0030] Specifically, in one optional embodiment, a first filter device 15 is provided on the first circulating supply pipeline 11, located between the first supply container 12 and the first metering pump 13. The first filter device 15 can effectively filter out impurity particles in the combined polyether or isocyanate. This prevents these impurities from entering the subsequent metering pump and the entire preparation system, preventing wear on the metering pump and extending the equipment's service life. It also ensures the purity of the raw materials, improves the quality of the polyurethane foam, and avoids defects inside the foam caused by impurities.
[0031] Specifically, in one optional embodiment, the first supply unit 10 is further configured with a first compressor 16 connected to the first supply container 12, the first compressor 16 supplying high-pressure gas to the first supply container 12. The supply of high-pressure gas can apply pressure to the liquid in the first supply container 12, causing the liquid to flow smoothly in the pipeline, especially in situations where significant transport resistance needs to be overcome, ensuring that the raw materials can be stably and continuously supplied to subsequent devices, thus guaranteeing the continuity of the preparation process.
[0032] Specifically, in one optional embodiment, the first supply container 12 is also connected to a first temperature regulating device 17 for regulating the internal temperature of the first supply container 12. Temperature has a significant impact on the physical properties and chemical reactivity of the combined polyether or isocyanate. By precisely regulating the temperature, the raw materials can be kept in an optimal reaction state, improving reaction efficiency, while ensuring the consistency of product quality, such as controlling the density, hardness, and other performance indicators of the foam within a stable range.
[0033] Specifically, in one optional embodiment, the second supply unit 20 includes a second circulating supply pipeline 21 and a second supply container 22, a second switching valve 28, and a second metering pump 23 located thereon. Its function is similar to that of the first supply unit 10. The second supply container 22 stores the combined polyether or isocyanate (different from the raw materials stored in the first supply unit 10), and the second metering pump 23 precisely controls the liquid flow rate to ensure precise matching of the flow rates of the two main raw materials (combined polyether and isocyanate) during the preparation process, thereby guaranteeing the quality of the polyurethane foam preparation. Furthermore, flow sensors 24 are respectively installed on the inlet and outlet pipelines of the second metering pump 23 to detect the real-time flow rate on the second circulating supply pipeline 21, so as to precisely control the pumping volume of the second metering pump 23.
[0034] The second switching valve 28 is used to switch the flow direction of material through the outlet of the second metering pump 23. The second switching valve 28 is a pneumatically controlled distribution valve, that is, it is connected to a pneumatic system to realize the switching of working positions. It includes a second working position and a second working position. When the second switching valve 28 is in the first working position, the material in the second supply container 22 circulates inside the second circulation supply pipeline 21. When the second switching valve 28 is in the second working position, the material in the second supply container 22 is supplied to the mixing and dispensing device 50 through the second metering pump 23.
[0035] Similarly, a second filter device 25 is installed on the second circulating supply pipeline 21, located between the second supply container 22 and the second metering pump 23. The second filter device 25 also serves to filter impurities, protecting the second metering pump 23 and the entire system from the influence of impurities, improving equipment reliability, ensuring product quality, and avoiding product defects caused by impurities.
[0036] Specifically, in one optional embodiment, the second compressor 26 is connected to the second supply container 22 and delivers high-pressure gas to the second supply container 22. Its function is similar to that of the first compressor 16, providing pressure to the liquid within the second supply container 22 to ensure smooth transport of raw materials in the pipeline and maintain the stability of the preparation process.
[0037] Specifically, in one optional embodiment, the second supply container 22 is also connected to a second temperature regulating device 27 for regulating the internal temperature of the second supply container 22. Similar to the function of the first temperature regulating device 17, controlling the temperature optimizes the reaction conditions of the raw materials, ensuring the stability and consistency of the polyurethane foam product's performance.
[0038] Specifically, the third supply unit 30 includes a third circulating supply pipeline 31 and a third supply container 32, a third switching valve 38, and a third metering pump 37 disposed thereon. The third supply container 32 stores polyurethane additives and is a high-pressure supply container with a pressure value greater than or equal to 10 MPa, and is equipped with a pressure relief device 35. The pressure relief device 35 releases pressure in a timely manner when the system pressure rises abnormally, ensuring the safe operation of the system and preventing equipment damage or safety accidents caused by excessive pressure. The third metering pump 37 can accurately control the liquid flow rate output from the third supply container 32. Precise flow control is crucial to ensuring the accuracy of the proportions of each raw material during the preparation process, thereby ensuring that the produced polyurethane foam has stable quality and meets expected performance.
[0039] Specifically, the third switching valve 38 is used to switch the flow direction of material through the outlet of the third metering pump 37. The third switching valve 38 is a pneumatically controlled distribution valve, that is, it is connected to a pneumatic system to realize the switching of working positions. It includes a third working position and a second working position. When the third switching valve 38 is in the first working position, the material in the third supply container 32 circulates inside the third circulation supply pipeline 31. When the third switching valve 38 is in the second working position, the material in the third supply container 32 is supplied to the premixing device 40 via the third metering pump 37.
[0040] Specifically, the third circulation supply line 31 is also equipped with a pressure regulating valve 33 and a flow sensor 34. The pressure regulating valve 33 can adjust the pressure of the polyurethane additive in the supply line to ensure that the additive can be delivered to the premixing device 40 at a suitable pressure. The flow sensor 34 is used to detect the flow rate in the third circulation supply line 31 in order to accurately control the amount of polyurethane additive entering the premixing device 40.
[0041] The working principle of the above preparation system is as follows:
[0042] Preparation stage: The first supply unit 10, the second supply unit 20, and the third supply unit 30 are in an internal circulation process. Specifically, the first switching valve 18, the second switching valve 28, and the third switching valve 38 are controlled to switch to the first working position. Among them, the combined polyether material is fed into the first supply container 12 by the first compressor 16 with pressurized air. The combined polyether material flows into the first metering pump 13. The first metering pump 13 pumps the combined polyether material into the first supply container 12 at a first flow rate to achieve internal circulation. At the same time, during the internal circulation process, the combined polyether material is adjusted to a set temperature value suitable for subsequent mixing and reaction by the first temperature regulating device 17. The isocyanate material and polyurethane additives are also internally circulated in the same way, which will not be described in detail here.
[0043] Preparation stage: The first switching valve 18, the second switching valve 28, and the third switching valve 38 are switched to the second working position respectively. After internal circulation, the combined polyether material that meets the preparation conditions passes through the first supply container 12 and is pressurized by the first compressor 16. It then flows into the first metering pump 13 through the first filter device 15. The first metering pump 13 pumps the material into the premixing device 40 at a set flow rate. Similarly, the polyurethane additive in the third supply container 32 flows out in liquid form through pressurized air and is premixed in the premixing device 40 at a certain ratio. The premixing device 40 is equipped with a static mixing unit to achieve thorough mixing of the liquid. The material mixed by the premixing device 40 enters the mixing and dispensing device 50. After internal circulation, the isocyanate material that meets the preparation conditions passes through the first supply container 12 and is pressurized by the second compressor 26. It then flows into the second metering pump 23 through the second filter device 25. The second metering pump 23 pumps the material into the mixing and dispensing device 50 at a certain flow rate. The mixing and dispensing device 50 uses a hydraulic pump 60 to drive the mixing nozzle to dispense the material into the product to be dispensed.
[0044] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the protection scope of this utility model.
Claims
1. A system for preparing rigid polyurethane foam, characterized in that, include: The system comprises a first supply unit, a second supply unit, a third supply unit, a premixing device, and a mixing and dispensing device; wherein, one of the first and second supply units is used to supply a combined polyether; the other of the first and second supply units is used to supply isocyanate; the third supply unit is used to supply polyurethane additives; at least one of the first and second supply units is provided with a supply amount adjustment device; the output terminals of the first and third supply units are connected to the input terminal of the premixing device; the output terminals of the premixing device and the second supply unit are connected to the input terminal of the mixing and dispensing device; and the output terminal of the mixing and dispensing device is connected to the product to be dispensed.
2. The rigid polyurethane foam preparation system according to claim 1, characterized in that, The first supply unit includes a first circulating supply pipeline and a first supply container, a first switching valve, and a first metering pump disposed on the first circulating supply pipeline. The first switching valve is used to switch the flow direction of the material passing through the outlet of the first metering pump.
3. The rigid polyurethane foam preparation system according to claim 2, characterized in that, The first supply unit further includes a first compressor and a first temperature regulating device connected to the first supply container. The first compressor is used to deliver high-pressure gas to the first supply container; the first temperature regulating device is used to exchange heat with the first supply container to regulate its internal temperature.
4. The rigid polyurethane foam preparation system according to claim 2, characterized in that, The first switching valve is a pneumatically controlled distribution valve, which includes a first working position and a second working position. When the first switching valve is in the first working position, the material in the first supply container circulates inside the first circulating supply pipeline. When the first switching valve is in the second working position, the material in the first supply container is supplied to the premixing device via the first metering pump.
5. A rigid polyurethane foam preparation system according to any one of claims 1-4, characterized in that, The second supply unit includes a second circulating supply pipeline, a second supply container, a second switching valve, and a second metering pump disposed on the second circulating supply pipeline. The second metering pump is used to adjust the supply amount of the second supply unit, and the second switching valve is used to switch the flow direction of the material through the outlet of the second metering pump.
6. The rigid polyurethane foam preparation system according to claim 5, characterized in that, The second supply unit further includes a second compressor and a second temperature regulating device connected to the second supply container. The second compressor is used to deliver high-pressure gas to the second supply container, and the second temperature regulating device is used to exchange heat with the second supply container to regulate its internal temperature.
7. The rigid polyurethane foam preparation system according to claim 5, characterized in that, The second switching valve is a pneumatically controlled distribution valve, which includes a first working position and a second working position. When the second switching valve is in the first working position, the material in the second supply container circulates inside the second circulating supply pipeline. When the second switching valve is in the second working position, the material in the second supply container is supplied to the mixing and dispensing device via the second metering pump.
8. The rigid polyurethane foam preparation system according to claim 1, characterized in that, The third supply unit includes a third circulation supply pipeline, a third supply container disposed on the third circulation supply pipeline, a third switching valve, and a third metering pump. The third switching valve is a pneumatically controlled distribution valve, which includes a first working position and a second working position. When the third switching valve is in the first working position, the material in the third supply container circulates inside the third circulation supply pipeline. When the third switching valve is in the second working position, the material in the third supply container is supplied to the premixing device via the third metering pump.
9. The rigid polyurethane foam preparation system according to claim 8, characterized in that, The third supply container is a high-pressure supply container with a pressure value greater than 10 MPa. A pressure regulating valve is installed on the third circulation supply pipeline, and a pressure relief device is provided on the third supply container.
10. The rigid polyurethane foam preparation system according to claim 8, characterized in that, The third supply unit further includes a third temperature regulating device connected to the third supply container, the third temperature regulating device being used to exchange heat with the third supply container to regulate its internal temperature.