Polyurethane sponge production system with liquid carbon dioxide as foaming agent

Abstract

The polyurethane sponge production system provided by the application is characterized in that liquid carbon dioxide and other raw materials are injected into a stirring device in the form of high pressure to obtain a mixture, the mixture is sent into a pouring system through a discharge port of the stirring device after being reduced to a pressure slightly higher than saturated vapor pressure of the liquid carbon dioxide, and the pressure of the mixture is rapidly reduced to atmospheric pressure when the mixture is sprayed from the pouring system, so that polyurethane sponge is generated by foaming, wherein the carbon dioxide is kept in liquid state during metering, conveying and mixing to prevent the liquid carbon dioxide from being precipitated in advance and affecting the quality of the polyurethane sponge. Meanwhile, the application is provided with a filter and a pouring mold, the mixture is filtered through a filter screen to form uniform and fine carbon dioxide bubble seeds, and then the mixture is sprayed through the pouring mold to fall on a conveying chain to continuously foam and harden to generate polyurethane sponge foam with uniform cells.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyurethane sponge production, and further relates to a polyurethane sponge step-by-step pressure reduction production system using liquid carbon dioxide as a foaming agent. BACKGROUND

[0002] In known continuous production of polyurethane block sponge, the most commonly used method is: at least one component containing a hydroxyl group (-OH) (especially a polyhydric alcohol compound such as a polyether) is mixed with an auxiliary physical foaming agent (commonly dichloromethane (MC)), a nucleating gas (dry air or nitrogen), and other additives, and then mixed with a component containing an isocyanate group (-CON) (especially an isocyanate such as TDI, MDI, etc.), and then a chemical foaming agent (water) and a catalyst (tin) are injected into the mixture, after high-speed stirring, the final mixture is sent to a continuously running conveyor belt, and one of the products of the chemical reaction of the final mixture is gaseous carbon dioxide, and a large amount of heat is released at the same time, the MC rapidly vaporizes and expands under the heat, and the main product of the mixture reaction rapidly expands to form a polyurethane foam under the combined action of the nucleation bubbles, MC bubbles, and carbon dioxide bubbles generated by the reaction. In order to produce high-quality polyurethane foam, the foaming process needs to be controlled to make the polyurethane foam body have uniform and fine pores, and the conventional method is to increase the catalyst to shorten the nucleation time, adjust the stirring speed to promote gas dispersion, adjust the pressure of the mixing head to control the gas release speed, and increase the nucleating agent to increase the nucleation center.

[0003] Since dichloromethane (MC) is harmful to the environment and human health, it is restricted and limited for use by countries around the world. In order to solve this problem, technical experts around the world have explored and verified through many studies that liquid carbon dioxide can be used to replace dichloromethane (MC) for foaming. Carbon dioxide itself is colorless, odorless, non-toxic, and harmless, and the use of liquid carbon dioxide for foaming has the excellent characteristics of stable flame retardation, high foaming efficiency, lower cost, and reasonable pore structure.

[0004] However, since carbon dioxide is a gas at room temperature, the known process for producing high-quality polyurethane foam using liquid carbon dioxide is no longer suitable, and therefore there is an urgent need for a production system that can complete the foaming nucleation process while maintaining the temperature and pressure of liquid carbon dioxide and produce high-quality polyurethane sponge. SUMMARY

[0005] In view of the problems in the prior art, the purpose of the present application is to provide a polyurethane sponge step-by-step pressure reduction production system using liquid carbon dioxide as a foaming agent, which replaces toxic dichloromethane (MC) with liquid carbon dioxide as a physical foaming agent, and completes the foaming nucleation process under the conditions of maintaining the temperature and pressure of liquid carbon dioxide, and produces polyurethane foam with uniform pores.

[0006] To achieve the above object, the present application provides the following technical solutions.

[0007] A polyurethane sponge production system using liquid carbon dioxide as a foaming agent, comprising a feeding system, a stirring device and a pouring system, wherein the feeding system comprises a liquid carbon dioxide high-pressure feeding unit, the outlet of the liquid carbon dioxide high-pressure feeding unit is connected to the feeding port of the stirring device, the stirring device is used to uniformly stir the liquid carbon dioxide and other raw materials under high pressure to obtain a mixture; the outlet of the stirring device is connected to the pouring system, the pressure of the mixture is reduced to a pressure slightly higher than the saturated vapor pressure of liquid carbon dioxide through the outlet of the stirring device and then the mixture is fed into the pouring system, and the pressure of the mixture is reduced to atmospheric pressure after being sprayed from the pouring system to form a polyurethane sponge.

[0008] In some technical solutions, the pouring system comprises a pouring mold, and the pouring mold comprises an outlet flow channel provided with a protruding structure, which is used to form a turbulent flow when the mixture is sprayed through the outlet flow channel, thereby facilitating the generation of bubbles.

[0009] In some technical solutions, the system further comprises a filter arranged on a pipeline between the outlet of the stirring device and the pouring system, which is used to filter and shear the mixture to generate micro-bubbles.

[0010] In some technical solutions, the system further comprises a pressure regulating device, wherein the pressure regulating device comprises a first pressure regulating valve and a second pressure regulating valve, the first pressure regulating valve is arranged on a pipeline between the outlet of the stirring device and the filter, and is used to maintain the pressure of the mixture close to or slightly higher than the dissolution partial pressure of carbon dioxide to slow down the precipitation of carbon dioxide; and the second pressure regulating valve is arranged on a pipeline between the filter and the pouring system, and is used to reduce the pressure of the mixture to accelerate the precipitation of carbon dioxide.

[0011] In some technical solutions, the feeding system further comprises a polyol high-pressure feeding unit, an additive high-pressure feeding unit, an isocyanate high-pressure feeding unit, a chemical reaction agent high-pressure feeding unit, an auxiliary agent high-pressure feeding unit and a nucleating gas feeding unit, which are respectively connected to the feeding port of the stirring device.

[0012] In some technical solutions, the outlet of the polyol high-pressure feeding unit and the outlet of the liquid carbon dioxide high-pressure feeding unit converge in a static mixer, which is used to uniformly mix the polyol and the liquid carbon dioxide to form an initial mixture; the outlet of the static mixer and the outlet of the additive supply unit converge in a first high-pressure manifold, which is used to uniformly mix the additive and the initial mixture to form an intermediate mixture, and the outlet of the first high-pressure manifold is connected to the feeding port of the stirring device; the outlet of the nucleation gas supply unit is connected to the outlet of the first high-pressure manifold, which is used to inject nucleation gas into the intermediate mixture before the intermediate mixture enters the stirring device.

[0013] In some technical solutions, the pouring mold comprises a feeding pipe, a left damping plate of a feeding port, a right damping plate of the feeding port, a left damping plate of a discharging port and a right damping plate of the discharging port, the left damping plate of the feeding port is provided with a feeding channel, the right damping plate of the feeding port is provided with a storage channel, the feeding channel and the storage channel enclose a storage groove, and a discharging flow channel A is arranged below the storage groove; the left damping plate of the discharging port is arranged below the left damping plate of the feeding port, the right damping plate of the discharging port is arranged below the right damping plate of the feeding port, a tapered discharging flow channel B is arranged between the left damping plate of the discharging port and the right damping plate of the discharging port, the tapered discharging flow channel B is provided with the convex structure, and the tapered discharging flow channel B is connected to the discharging flow channel A.

[0014] In some technical solutions, the convex structure is a corrugated structure, the left damping plate of the discharging port is provided with a first corrugated surface, the right damping plate of the discharging port is provided with a second corrugated surface, and the first corrugated surface and the second corrugated surface cooperatively form the corrugated structure.

[0015] In some technical solutions, the filter comprises a filter shell and a filter screen, the filter shell comprises, in order of water inlet sequence, a water inlet section, a diffusion section, a straight section, a contraction section and a water outlet section, the cross-sectional area of the water inlet section and the cross-sectional area of the water outlet section are the same and smaller than the cross-sectional area of the straight section, and the central axes of the water inlet section, the diffusion section, the straight section, the contraction section and the water outlet section are on the same straight line; the filter screen is detachably arranged in the filter shell in a U-shaped cross section, and the outer wall of the filter screen and the inner wall of the filter shell have a certain gap to form a filter flow passage.

[0016] In some technical solutions, the liquid carbon dioxide high-pressure feeding unit, the polyol high-pressure feeding unit, the additive high-pressure feeding unit, the isocyanate high-pressure feeding unit, the chemical reaction agent high-pressure feeding unit and the additive high-pressure feeding unit are respectively provided with a feeding storage tank and a self-circulation exhaust pipeline connected to each feeding storage tank, which is used to exhaust the gas in the pipeline to accurately measure the amount; the feeding system further comprises a metering device and a measuring device arranged on each self-circulation exhaust pipeline.

[0017] Compared with the prior art, the polyurethane sponge step-by-step pressure reduction production system provided by the application has the following beneficial effects:

[0018] 1、The liquid carbon dioxide and other raw materials in the polyurethane sponge step-by-step pressure reduction production system provided by the application are injected into the stirring device in the form of high pressure for mixing to obtain a mixture, the mixture is sent into the pouring system through the discharge port of the stirring device after being reduced to a pressure slightly higher than the saturated vapor pressure of the liquid carbon dioxide, and the pressure of the mixture is rapidly reduced to atmospheric pressure when the mixture is sprayed from the pouring system, so that the polyurethane sponge foam body is continuously foamed and hardened on the conveying chain, and the carbon dioxide remains in liquid state during the metering, conveying and mixing processes, thereby preventing the liquid carbon dioxide from precipitating in advance and affecting the quality of the polyurethane sponge;

[0019] 2、The pouring system provided by the application includes a filter and a pouring mold, the mixture is subjected to the shearing action of the filter screen to generate uniform and fine carbon dioxide bubble seeds, and then is sprayed from the outlet flow channel of the pouring mold, the outlet flow channel of the pouring mold is provided with a corrugated structure, when the mixture is rapidly sprayed from the outlet flow channel, the cross section changes sharply to cause impact and form turbulence, and when the mixture is sprayed, its pressure is rapidly reduced to atmospheric pressure, the carbon dioxide is rapidly precipitated from the mixture and agglomerated on the fine bubble nuclei in advance to form uniform bubble holes filled between the solid substances generated by the reaction;

[0020] 3、The filter provided by the application filters the mixture first to avoid that the poured mixture is mixed with impurities, and the filter screen cross section is U-shaped and detachably arranged in the filter shell to form a larger filtering area, so that more impurities are filtered and the filtering efficiency is higher, the filter is convenient to replace and clean and durable;

[0021] 4、The liquid carbon dioxide is used to replace the toxic methylene chloride (MC) as the physical foaming agent, the liquid carbon dioxide is low in price, non-toxic and widely available, and the production cost and environmental pollution of the polyurethane sponge are reduced. BRIEF DESCRIPTION OF DRAWINGS

[0022] The above-mentioned features, technical characteristics, advantages and implementation modes of the application will be further described in the following in a clear and understandable manner in combination with the preferred embodiments and the accompanying drawings.

[0023] Figure 1 The overall structure schematic diagram of the polyurethane sponge step-by-step pressure reduction production system provided by the application is shown in the figure;

[0024] Figure 2 The structure schematic diagram of the pouring system provided by the application is shown in the figure;

[0025] Figure 3 The structure schematic diagram of the filter provided by the application is shown in the figure;

[0026] Figure 4 A structure diagram of a pouring mold provided by the present application is shown in the figure.

[0027] Figure 5 For Figure 4 A local enlarged view at X in the middle.

[0028] BRIEF DESCRIPTION OF DRAWINGS 1 - polyol high-pressure supply unit; 2 - second high-pressure manifold; 3 - liquid carbon dioxide high-pressure supply unit; 4 - static mixer; 5 - additive high-pressure supply unit; 6 - first high-pressure manifold; 7 - nucleation gas supply unit; 8 - chemical reactant high-pressure supply unit; 9 - auxiliary agent high-pressure supply unit; 10 - stirring device; 11 - other raw material high-pressure supply unit; 12 - isocyanate high-pressure supply unit; 13 - first pressure regulating valve; 14 - first filter; 15 - second pressure regulating valve; 16 - first pouring mold; 17 - second filter; 18 - third pressure regulating valve; 19 - second pouring mold; 20 - filter housing; 21 - filter screen; 22 - feed pipe; 23 - left damping plate of feed inlet; 24 - right damping plate of feed inlet; 25 - left damping plate of discharge outlet; 26 - right damping plate of discharge outlet. DETAILED DESCRIPTION

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, specific embodiments of the present application will be described below with reference to the drawings. Obviously, the drawings in the following description only represent some embodiments of the present application, and for those skilled in the art, other drawings can be obtained from these drawings without creative labor, and other embodiments can also be obtained.

[0030] In order to make the drawing simple, only the parts related to the application are shown in each drawing, which does not represent the actual structure of the product. In addition, in order to make the drawing simple and easy to understand, in some drawings, only one of the parts with the same structure or function is shown schematically, or only one of them is marked. In this paper, "one" not only means "only one", but also means "more than one".

[0031] It should be further understood that the term "and / or" used in the specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0032] In this article, it is necessary to explain that, unless otherwise expressly provided and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0033] In addition, in the description of the present application, the terms "first", "second" and the like are only used for differentiation and description, and cannot be understood as indicating or implying relative importance.

[0034] Embodiment 1

[0035] As Figure 1 shown, the present application provides a step-by-step pressure reduction production system for polyurethane sponge using liquid carbon dioxide as a foaming agent, which comprises a feeding system, a stirring device 10 and a pouring system. The feeding system comprises a liquid carbon dioxide high-pressure feeding unit 3, the outlet of the liquid carbon dioxide high-pressure feeding unit 3 is connected to the inlet of the stirring device 10, and the stirring device 10 is used to uniformly stir the liquid carbon dioxide and other raw materials under high pressure to obtain a mixture; the outlet of the stirring device 10 is connected to the pouring system, and the mixture is sent into the pouring system after being reduced in pressure to a pressure slightly higher than the saturated vapor pressure of liquid carbon dioxide through the outlet of the stirring device 10, and the pressure of the mixture is reduced to atmospheric pressure after being sprayed out of the pouring system, and carbon dioxide is quickly precipitated from the mixture, and the mixture is quickly foamed to form polyurethane sponge.

[0036] In this embodiment, the feeding system further comprises a polyol high-pressure feeding unit 1, an additive high-pressure feeding unit 5, an isocyanate high-pressure feeding unit 12, a chemical reaction agent high-pressure feeding unit 8, an auxiliary agent high-pressure feeding unit 9 and a nucleating gas feeding unit 7, which are respectively connected to the inlet of the stirring device 10. The above-mentioned feeding units sequentially pass the raw materials into the stirring device 10 to be uniformly stirred with the liquid carbon dioxide to obtain a mixture.

[0037] Embodiment 2

[0038] On the basis of embodiment 1, the pouring system comprises a first pouring mold 16, and the first pouring mold 16 comprises a discharge flow channel provided with a protruding structure. When the mixture is sprayed out through the discharge flow channel, it passes through the protruding structure and is impacted due to the sharp change in cross section, forming turbulent flow, which is conducive to the generation of bubbles and improves the foaming effect.

[0039] As Figure 1 shown, the present application provides a preferred embodiment of a pouring mold, which is combined with Figure 4 and Figure 5As shown, the first pouring mold 16 comprises a feeding pipe 22, a left damping plate 23 of the feeding port, a right damping plate 24 of the feeding port, a left damping plate 25 of the discharging port and a right damping plate 26 of the discharging port, the left damping plate 23 of the feeding port is provided with a feeding channel, the right damping plate 24 of the feeding port is provided with a storage channel, the feeding channel and the storage channel enclose a storage groove, and a discharging flow channel A is arranged below the storage groove.

[0040] The left damping plate 25 of the discharging port is arranged below the left damping plate 23 of the feeding port, the right damping plate 26 of the discharging port is arranged below the right damping plate 24 of the feeding port, a tapered discharging flow channel B is arranged between the left damping plate 25 of the discharging port and the right damping plate 26 of the discharging port, the tapered discharging flow channel B is provided with a convex structure, and the tapered discharging flow channel B is in communication with the discharging flow channel A.

[0041] More preferably, as shown in the drawings, Figure 5 The convex structure of the tapered discharging flow channel B is a corrugated structure, the left damping plate 25 of the discharging port is provided with a first corrugated surface, the right damping plate 26 of the discharging port is provided with a second corrugated surface, and the first corrugated surface and the second corrugated surface cooperatively form the corrugated structure.

[0042] When the mixture enters the flow channel B from the flow channel A, the cross section of the mixture changes sharply when passing through the corrugated structure, and the turbulence caused by the impact helps the generation of bubbles, and after the mixture flows out of the flow channel B, the pressure is sharply reduced to atmospheric pressure, carbon dioxide is rapidly precipitated from the mixture and agglomerated on the bubble seeds to form uniform cell polyurethane foam.

[0043] In addition, the feeding pipe 22, the left damping plate 23 of the feeding port, the right damping plate 24 of the feeding port, the left damping plate 25 of the discharging port and the right damping plate 26 of the discharging port all have quick release structures, and the first pouring mold 16 can be disassembled and cleaned when not in production, and can be quickly installed for pouring when in production.

[0044] Example 3

[0045] On the basis of example 1 and example 2, the system further comprises a first filter 14 and a pressure regulating device, the first filter 14 is arranged on the pipeline between the discharging port of the stirring device 10 and the first pouring mold 16, the pressure regulating device comprises a first pressure regulating valve 13 and a second pressure regulating valve 15, the first pressure regulating valve 13 is arranged on the pipeline between the discharging port of the stirring device 10 and the first filter 14, and the second pressure regulating valve 15 is arranged on the pipeline between the first filter 14 and the first pouring mold 16, as shown in the drawings, Figure 1 The outlet of the stirring device 10 is in sequence communicated with the first pressure regulating valve 13, the first filter 14, the second pressure regulating valve 15 and the first pouring mold 16 to form a pouring pipeline, and after the mixture flows out of the first pressure regulating valve 13, it flows through the first filter 14 and the second pressure regulating valve 15 in sequence, and then enters the first pouring mold 16 to form a polyurethane foam body.

[0046] The first pressure regulating valve 13 can adjust the pressure of the mixture output by the stirring device 10, and control the pressure at 1-3 MPa. More preferably, the pressure of the output mixture is adjusted according to the different parts of carbon dioxide in the formula, and the pressure of the output mixture is controlled to be maintained at 1-3 MPa, so as to maintain the liquid phase of carbon dioxide.

[0047] The second pressure regulating valve 15 adjusts the pressure of the mixture flowing through the first filter 14 to be 0.1-0.3 MPa lower than the pressure of the mixture in the stirring device 10. This pressure is very close to or slightly higher than the equilibrium dissolution partial pressure of carbon dioxide in the final mixture. At this time, the carbon dioxide gas released from the liquid carbon dioxide and the carbon dioxide gas generated by the reaction of each raw material are evenly distributed in the mixture, and the bubbles agglomerate and increase in size. The mixture is sheared and dispersed by the filter screen 21, which delays the formation of large bubbles and makes the bubbles more uniform and smaller. Finally, after being sprayed out through the first casting mold 16, the pressure of the mixture is rapidly reduced to atmospheric pressure, and carbon dioxide is rapidly released and agglomerates on the foam seeds to grow and form a polyurethane foam with uniform cells.

[0048] In actual use, the first casting mold 16 occasionally becomes clogged. To reduce downtime losses caused by the clogged first casting mold 16, such as... Figure 2 As described above, an additional backup pouring pipeline is added at the outlet of the first pressure regulating valve 13. This backup pouring pipeline is sequentially equipped with a second filter 17, a third pressure regulating valve 18, and a second pouring mold 19. Pressure sensors are installed on both pouring pipelines to monitor the mixture pressure in real time. When the pressure in one of the working pipelines exceeds a set value, production can be switched to the backup pouring pipeline. The blocked working pipeline can be manually disassembled, cleaned, and then reused, thus avoiding downtime losses.

[0049] Example 4

[0050] Based on Example 3, this example provides a preferred implementation of the first filter 14, such as... Figure 3 As shown, the first filter 14 includes a filter housing 20 and a filter screen 21. The filter housing 20 is arranged in the order of water inlet, consisting of an inlet section, a diffuser section, a straight section, a contraction section, and an outlet section. The cross-sectional area of ​​the inlet section and the outlet section are the same and smaller than the cross-sectional area of ​​the straight section. The central axes of the inlet section, diffuser section, straight section, contraction section, and outlet section are on the same straight line.

[0051] Since the cross-sectional areas of the inlet and outlet sections of the filter housing 20 are smaller than those of the straight section, the flow velocity of the mixture within the filter housing 20 varies due to the combination of the diffuser and constriction sections. Furthermore, the central axes of the inlet, diffuser, straight section, constriction section, and outlet sections are on the same straight line, which reduces the eddies in the filter housing 20 and thus reduces the flow resistance.

[0052] likeFigure 3 As shown, the filter screen 21 has a U-shaped cross-section and is detachably installed within the filter housing 20 as a straight section. The outer wall of the filter screen 21 has a certain gap with the inner wall of the filter housing 20, forming a filtration flow chamber. The width of this filtration flow chamber is S1, and its length is L. With S1 determined, by reasonably adjusting the opening ratio of the filter screen 21 and the length L of the filtration flow chamber, the ratio of the filtration area to the flow area of ​​the inlet section can be made between 3 and 5 times. This satisfies the filtration flow requirements while maintaining the speed at which the mixture flows through the filter screen 21, thus generating a shearing effect on the mixture and producing microbubbles.

[0053] Furthermore, the filter screen 21 is U-shaped within the filter housing, resulting in a filtration area much larger than the cross-sectional area of ​​the inlet section of the filter housing 20. This, combined with the aforementioned filter housing structure, ensures a more uniform flow rate of the mixture passing through the filter screen 21, significantly improving the filtration effect.

[0054] Example 5

[0055] Based on the above embodiments, such as Figure 1 As shown, in this embodiment, the liquid carbon dioxide high-pressure feeding unit 3, the polyol high-pressure feeding unit 1, the additive high-pressure feeding unit 5, the isocyanate high-pressure feeding unit 12, the chemical reactant high-pressure feeding unit 8, and the auxiliary agent high-pressure feeding unit 9 are each equipped with a feeding tank and a self-circulating exhaust pipeline connected to each feeding tank. Each self-circulating exhaust pipeline is equipped with a metering device and a measuring device. The metering device includes a metering pump and a mass flow meter connected in sequence, and the measuring device includes a pressure sensor and a temperature sensor, such as... Figure 1 As shown, before production begins, each of the aforementioned feeding units has a self-circulating exhaust process before introducing raw materials into the mixing device 10. According to the formula, various raw materials to be added are first pumped from their respective feeding tanks by metering pumps. These raw materials circulate back to their feeding tanks within the self-circulating exhaust pipeline. This circulation is to remove air from the pipeline, facilitating accurate measurement of the amount of each raw material. The outlet of the self-circulating exhaust pipeline and the inlet of the mixing device 10 are connected by a three-way valve. A one-way valve and a nozzle are also sequentially connected on the pipeline between the outlet of the self-circulating exhaust pipeline and the inlet of the mixing device 10. At the start of production, the three-way valve is switched, and the various raw materials, after being metered in the self-circulating exhaust pipeline, pass through the three-way valve, the one-way valve, and finally, the high-pressure raw materials are injected into the mixing device 10 through the nozzle.

[0056] In this embodiment, the nucleating gas supply unit 7 preferably uses high-pressure nitrogen as the nucleating gas, and the high-pressure nitrogen is stored in a series of gas cylinders.

[0057] Since liquid carbon dioxide requires low-temperature and high-pressure storage (-18℃~-24℃, 1.85Mpa) to maintain its liquid phase, starting the liquid carbon dioxide circulation pipeline before production begins can be used to purge the gas in the pipeline and cool all pipelines and fittings to prevent carbon dioxide from precipitating out.

[0058] Therefore, in this embodiment, the liquid carbon dioxide circulation pipeline preferably includes an internal circulation cooling pipeline and an external circulation cooling pipeline, such as Figure 1 As shown, the outlet and inlet of the liquid carbon dioxide storage tank are connected by pipelines to form an internal circulation cooling pipeline. The outlet of the liquid carbon dioxide storage tank, the liquid carbon dioxide pressure sensor, the liquid carbon dioxide metering pump, the liquid carbon dioxide mass flow meter, and the inlet of the liquid carbon dioxide storage tank are connected in series by pipelines to form an external circulation cooling pipeline. First, the internal circulation cooling pipeline is turned on some time before production, preferably 40 minutes before production. The delivery pump on the outlet pipeline of the liquid carbon dioxide storage tank pumps liquid carbon dioxide into the internal circulation cooling pipeline and then back into the liquid carbon dioxide storage tank. This ensures that the supply pipelines outside the liquid carbon dioxide storage tank reach the liquid carbon dioxide storage temperature range (-18℃ to -24℃), eliminating the possibility of gas release due to temperature rise. After internal circulation cooling for more than 30 minutes, the internal circulation cooling pipeline is closed, and the external circulation cooling pipeline is turned on. When the temperature in the external circulation cooling pipeline reaches the liquid carbon dioxide storage temperature range, the liquid carbon dioxide is introduced into the stirring device 10 according to the formula dosage to mix with other raw materials.

[0059] Example 6

[0060] On the basis of embodiment 5, in the production of polyurethane sponge, multiple polyol high-pressure supply units 1 and additive high-pressure supply units 5 can be set according to the formulation requirements, the outlets of each polyol high-pressure supply unit 1 converge in the second high-pressure manifold 2, the outlets of multiple additive high-pressure supply units 5 converge in the first high-pressure manifold 6, each polyol high-pressure supply unit 1 includes a self-circulating exhaust pipeline, when the corresponding polyol compound is required by the formulation, the corresponding self-circulating exhaust pipeline is opened, after exhausting, the metered polyol compound is introduced into the second high-pressure manifold 2 to uniformly mix to form a mixture one. At the same time, the outlet of the second high-pressure manifold 2 and the outlet of the liquid carbon dioxide high-pressure supply unit 3 converge in a static mixer 4, the metered liquid carbon dioxide and the mixture one are uniformly mixed in the static mixer 4 to form a mixture two, the outlet of the static mixer 4 and the outlet of the additive high-pressure supply unit 5 converge in the inlet of the first high-pressure manifold 6, the mixture two and the multiple additives are uniformly mixed in the first high-pressure manifold 6 to form a mixture three, the outlet of the first high-pressure manifold 6 is connected to the inlet of the stirring device 10, the outlet of the nucleation gas supply unit 7 is connected to the outlet of the first high-pressure manifold 6, the nucleation gas (high-pressure nitrogen) is injected into the mixture three flowing from the first high-pressure manifold 6 to the stirring device 10 to form a mixture four, and then the mixture four is injected into the stirring device 10 to mix with the remaining raw materials to form a final mixture.

[0061] In actual production, the isocyanate high-pressure supply unit 12 can select one or more isocyanate raw materials according to the formulation, accordingly, multiple isocyanate high-pressure supply units 12 can be provided, and the isocyanate raw material is preferably TDI. When multiple isocyanate raw materials are used in production, the outlets of the multiple isocyanate high-pressure supply units 12 converge in a third high-pressure manifold, and the multiple isocyanate raw materials are uniformly mixed in the third high-pressure manifold and then injected into the stirring device 10 in two paths.

[0062] The chemical reaction agent of the chemical reaction agent high-pressure supply unit 8 is preferably water, and the additive of the additive high-pressure supply unit 9 is preferably tin.

[0063] The injection order of the above-mentioned raw materials into the stirring device 10 is preferably mixture four, isocyanate, chemical reaction agent, and additive, and the injection order can also be adjusted according to the selected raw materials and reaction time of the raw materials.

[0064] Preferably, the supply system is also provided with other raw material high-pressure supply units 11, the outlets of the other raw material high-pressure supply units 11 are connected to the inlet of the stirring device 10, which can be used as a standby raw material supply unit, or other raw materials can be added according to the production formulation.

[0065] The stirring speed of the stirring device 10 is 1000-6000 RPM, which can be adjusted according to the formulation.

[0066] The above merely is the preferred embodiment of the present application, it should be pointed out that, for ordinary skilled in the art, without departing from the principles of the present application, can also make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A staged decompression production system for polyurethane foam using liquid carbon dioxide as a foaming agent, characterized in that, The system comprises a feeding system, a stirring device and a pouring system, The feeding system comprises a high-pressure liquid carbon dioxide feeding unit, an outlet of which is connected to an inlet of the stirring device, the stirring device is used to uniformly stir the liquid carbon dioxide and other raw materials under high pressure to obtain a mixture; An outlet of the stirring device is connected to the pouring system, the mixture is depressurized to a pressure slightly higher than the saturated vapor pressure of liquid carbon dioxide through the outlet of the stirring device and is fed into the pouring system, the pouring system comprises a pouring mold, the pouring mold comprises an outlet flow channel, the outlet flow channel is provided with a protruding structure, and after the mixture is sprayed out of the pouring system, the pressure of the mixture is reduced to atmospheric pressure to form a polyurethane sponge by foaming; The system further comprises a filter and a pressure regulating device, The filter is arranged on a pipeline between the outlet of the stirring device and the pouring system, and is used to filter and shear the mixture to generate micro-bubbles; The pressure regulating device comprises a first pressure regulating valve and a second pressure regulating valve, the first pressure regulating valve is arranged on a pipeline between the outlet of the stirring device and the filter, and is used to maintain the pressure of the mixture close to or slightly higher than the dissolution partial pressure of carbon dioxide to slow down the precipitation of carbon dioxide; The second pressure regulating valve is arranged on a pipeline between the filter and the pouring system, and is used to reduce the pressure of the mixture to accelerate the precipitation of carbon dioxide.

2. The polyurethane sponge step-by-step pressure reduction production system according to claim 1, wherein The feeding system further comprises a high-pressure polyol feeding unit, a high-pressure additive feeding unit, a high-pressure isocyanate feeding unit, a high-pressure chemical reaction agent feeding unit, a high-pressure auxiliary agent feeding unit and a nucleation gas feeding unit, which are respectively connected to the inlet of the stirring device.

3. The polyurethane sponge step-by-step pressure reduction production system according to claim 2, wherein An outlet of the high-pressure polyol feeding unit and an outlet of the high-pressure liquid carbon dioxide feeding unit converge in a static mixer, the static mixer is used to uniformly mix the polyol and the liquid carbon dioxide to form an initial mixture; An outlet of the static mixer and an outlet of the additive supply unit converge in a first high-pressure manifold, the first high-pressure manifold is used to uniformly mix the additive and the initial mixture to form an intermediate mixture, and an outlet of the first high-pressure manifold is connected to the inlet of the stirring device; An outlet of the nucleation gas supply unit is connected to the outlet of the first high-pressure manifold, and is used to inject nucleation gas into the intermediate mixture before the intermediate mixture enters the stirring device.

4. The polyurethane sponge step-by-step pressure reduction production system according to claim 1, wherein The pouring mold comprises an inlet pipe, a left damping plate of an inlet, a right damping plate of the inlet, a left damping plate of an outlet and a right damping plate of the outlet, The left damping plate of the inlet is provided with an inlet channel, the right damping plate of the inlet is provided with a storage channel, the inlet channel and the storage channel enclose a storage groove, and a lower portion of the storage groove is provided with an outlet flow channel A. The left damping plate of the discharge port is arranged below the left damping plate of the feeding port, the right damping plate of the discharge port is arranged below the right damping plate of the feeding port, a tapered discharge flow channel B is arranged between the left damping plate of the discharge port and the right damping plate of the discharge port, the tapered discharge flow channel B is provided with the convex structure, and the tapered discharge flow channel B is in communication with the discharge flow channel A.

5. The polyurethane sponge step-by-step pressure reduction production system according to claim 4, characterized in that, The convex structure is a corrugated structure, the left damping plate of the discharge port is provided with a first corrugated surface, the right damping plate of the discharge port is provided with a second corrugated surface, and the first corrugated surface and the second corrugated surface cooperate to form the corrugated structure.

6. The polyurethane sponge step-by-step pressure reduction production system according to claim 1, characterized in that, The filter comprises a filter shell and a filter screen, the filter shell comprises, in order of water inlet, a water inlet section, a diffusion section, a straight section, a contraction section and a water outlet section, the cross-sectional area of the water inlet section and the cross-sectional area of the water outlet section are the same and smaller than the cross-sectional area of the straight section, and the central axes of the water inlet section, the diffusion section, the straight section, the contraction section and the water outlet section are on the same straight line; The filter screen is in the shape of U and is detachably arranged in the filter shell, the outer wall of the filter screen and the inner wall of the filter shell have a certain gap, and a filter flow cavity is formed.

7. The polyurethane sponge step-by-step pressure reduction production system according to claim 2, characterized in that, The liquid carbon dioxide high-pressure feeding unit, the polyhydric alcohol high-pressure feeding unit, the additive high-pressure feeding unit, the isocyanate high-pressure feeding unit, the chemical reaction agent high-pressure feeding unit and the auxiliary agent high-pressure feeding unit are respectively provided with a feeding storage tank and a self-circulation exhaust pipeline in communication with each feeding storage tank, for exhausting gas in the pipeline to accurately measure the amount; The feeding system further comprises a metering device and a measuring device arranged on each self-circulation exhaust pipeline.

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