A method for foaming a polymer polyol using pressurized liquid carbon dioxide

Abstract

This invention discloses a method for foaming polymer polyols using pressurized liquid carbon dioxide. The method involves mixing polyether polyols and / or polymer polyols, then thoroughly mixing them with pressurized liquid carbon dioxide in a static mixer. Subsequently, the mixture reacts with nitrogen-assisted dispersed toluene diisocyanate in a main mixing chamber. Foaming is then completed through a three-stage filtration system and a gradient decompression process. The three-stage filtration system employs a combination of pre-filters, working filters, and terminal filters, while the gradient decompression process ensures stable vaporization of carbon dioxide. This invention significantly improves the cell structure and mechanical properties of the foamed product by optimizing process parameters and system configuration. The resulting polyurethane foam exhibits excellent comprehensive performance. This method is characterized by process stability, environmental friendliness, and high efficiency, solving the technical challenges of traditional foaming processes.

Description

Technical Field

[0001] This invention belongs to the field of polymer foam material preparation technology, and particularly relates to a method for foaming polymer polyols using liquid carbon dioxide under pressure. Background Technology

[0002] Polymer polyol foam materials are widely used in the automotive, construction, and packaging industries due to their excellent mechanical properties and lightweight characteristics. Traditional foaming processes mainly rely on physical foaming agents such as chlorofluorocarbons (HCFC-141b) or hydrocarbons (such as cyclopentane), but these substances pose environmental problems such as ozone layer depletion and global warming. With increasingly stringent environmental protection requirements, the development of new environmentally friendly foaming technologies has become an urgent need for the industry.

[0003] Liquid carbon dioxide has attracted much attention as a green blowing agent with zero ozone depletion potential and low global warming potential. However, in practical industrial applications, it still faces the following technical bottlenecks, such as solubility and nucleation control problems. That is, the solubility of CO2 in polymer systems is significantly lower than that of traditional blowing agents, resulting in uneven nucleation and easy formation of cell merging or collapse. Another issue is insufficient process stability, that is, CO2 injected under high pressure is prone to sudden vaporization during decompression, causing damage to the cell structure.

[0004] CN104175445A discloses a supercritical carbon dioxide foaming device for extruded polystyrene boards, including a high-pressure carbon dioxide metering pump, a static mixer, a high-pressure accelerator metering pump, a carbon dioxide thermostat, a first pulse damper, a carbon dioxide mass flow meter, a second pulse damper, an accelerator mass flow meter, and a data processing device. The first pulse damper eliminates pulses in the carbon dioxide liquid within the pipeline, ensuring the carbon dioxide mass flow meter can accurately measure the mass value. The data processing device controls the delivery rate of the high-pressure carbon dioxide metering pump based on pre-stored carbon dioxide mass values ​​and real-time carbon dioxide mass values ​​to adjust the carbon dioxide pressure to reach the critical pressure. The carbon dioxide thermostat is located between the first pulse damper and the carbon dioxide mass flow meter to heat the carbon dioxide liquid to reach the critical temperature value. The carbon dioxide at the critical state is then transported to the static mixer for successful foaming. While the device uses supercritical carbon dioxide as the foaming medium, which improves solubility, maintaining the supercritical state requires continuous heating, resulting in high energy consumption during the foaming process.

[0005] CN107722218A discloses an organofluorosilicone resin modified polyurethane foam, which comprises the following components by weight: 40-65 parts polyester polyol, 30-45 parts hydroxyl-terminated fluorosilicone resin, 55-75 parts isocyanate, 12-23 parts triethanolamine, 8-12 parts antioxidant, 3-5 parts deionized water, 8-15 parts surfactant, and 1.5-4 parts blowing agent. The polyurethane foam improves the cell structure by adding a special surfactant containing silicon-fluorine segments, but the cost of the additive is 3-5 times that of conventional surfactants, and it has poor compatibility with TDI systems, which easily leads to foam cracking.

[0006] CN215742228U discloses a foaming and filtering device for foam production, relating to the field of foaming technology. This foaming and filtering device includes a support assembly consisting of a base plate and a first support frame. A foaming agent storage box is fixed on the first support frame, and the foaming agent storage box is connected to a filter box movably mounted on the base plate via a feed pipe. A second fixed plate is movably mounted inside the filter box, and a first filter assembly is mounted inside the second fixed plate. A second filter assembly is located below the second fixed plate. While the two-stage filtration device reduces the clogging frequency of ordinary systems, it cannot solve the clogging problem of high-hardness polymer polyol foams. Summary of the Invention

[0007] To address the problems of uneven foaming, poor adaptability of filtration systems, and filter clogging and increased foaming pressure that often occur when polymer polyol components are used in liquid carbon dioxide foaming, this invention solves these problems through optimized raw material selection, a three-stage gradient filtration system, and a combination of process parameters.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for foaming polymer polyols using liquid carbon dioxide under pressure, the method comprising the following steps:

[0010] (1) Polyether polyol SC56-16S and polymer polyol HS-200S with a mass ratio of (50~80):(20~50) are pressurized to 20~35 bar by a feed pump and a high pressure pump and then fed into a static mixer. At the same time, liquid carbon dioxide with a mass of 1.5~3.0% of the total mass of polyols is pressurized to 40~60 bar and injected into the static mixer to mix with the polyols.

[0011] (2) The mixture obtained in step (1) is transported to the main mixing chamber and the pressure is reduced to 5-7 bar. At the same time, silicone oil surfactant, amine catalyst and tin catalyst are injected into the main mixing chamber.

[0012] (3) Inject pressurized nitrogen at 90~110 bar into the toluene diisocyanate pipeline to form a TDI-nitrogen mixture, and inject it into the main mixing chamber at a pressure of 50~70 bar;

[0013] (4) After mixing at a speed of 4000~6000 r / min in the main mixing chamber, the material enters the emulsifier and is gradually depressurized to atmospheric pressure by 50~60 bar before being poured and foamed; the emulsifier is equipped with a three-stage filtration structure, which includes:

[0014] Pre-filter with a pore size of 100~350 μm;

[0015] Working filter element with a pore size of 80~160 μm;

[0016] Terminal filter with a pore size of 70~160 μm.

[0017] The present invention provides a method for polymer polyol foaming using liquid carbon dioxide pressurization, which differs from other liquid carbon dioxide foaming methods in that it involves a polymer polyol component. In this invention, the polymer polyol is a polyether polyol grafted with styrene and acrylonitrile copolymers, and a specific ratio of polyols is used to form an optimized molecular chain structure, which can significantly improve the hardness of the sponge in the formulation system. Due to the particle size distribution of styrene-acrylonitrile copolymer particles, its application in liquid carbon dioxide foaming is generally very difficult, as the copolymer particles in the polymer polyol cannot pass 100% through the filter in the emulsifier, causing filter blockage and increased foaming pressure. In this invention, for a system using polymer polyols for foaming, firstly, a polyol pressurization pressure of 20-35 bar and a liquid CO2 injection pressure of 40-60 bar work synergistically to achieve homogeneous mixing under supercritical conditions. Secondly, a three-stage gradient filtration system combined with a step-by-step decompression mechanism achieves step-by-step interception of impurities and precise control of bubble nuclei. Among these, the high-pressure injection of the TDI-nitrogen mixture can significantly improve the uniformity of the bubble pores, while the gradient pore size design of the three-stage filtration effectively intercepts undispersed particles and prevents bubble collapse. Ultimately, this achieves a comprehensive improvement in bubble pore uniformity, process stability, and production economy, forming a triple synergistic mechanism of pressure control, filtration purification, and parameter optimization, thus breaking through the technical bottleneck of liquid CO2 foaming.

[0018] Preferably, in step (1), the static mixer is provided with 4 to 6 spiral guide vanes with a spiral angle of 30 to 45°, and the liquid carbon dioxide injection rate is 5 to 10% of the mass flow rate of the polyol.

[0019] The present invention provides a method for foaming polymer polyols using liquid carbon dioxide pressurization. It designs a spiral guide plate with a spiral angle of 30-45° to enhance the micro-mixing of CO2 and polyol by generating a turbulence effect. The layout of 4-6 plates achieves a balance between pressure drop and mixing efficiency. The CO2 injection rate is controlled at 5-10% of the polyol flow rate, which can ensure the saturated solubility of gas in the polymer melt and avoid excessive local concentration that leads to cell merging.

[0020] Preferably, the injection pressure of liquid carbon dioxide in step (1) is 45~55 bar, and the pressurization pressure of nitrogen in step (3) is 95~105 bar.

[0021] Preferably, in step (2), the HLB value of the silicone oil surfactant is 9 to 11.

[0022] The present invention provides a method for foaming polymer polyols under pressure with liquid carbon dioxide. It selects polyether-modified polysiloxanes with HLB values ​​of 9-11, which can form a dynamic equilibrium molecular arrangement at the gas-liquid interface. This specific HLB range reduces the surface tension to 20-25 mN / m, which exactly matches the interfacial energy requirements of the CO2 foaming system, thereby stabilizing the cell structure.

[0023] Preferably, in step (2), the mass ratio of bis(dimethylaminoethyl) ether to triethylenediamine in the amine catalyst is 1:(0.8~1.5).

[0024] The present invention provides a method for foaming polymer polyols under pressure with liquid carbon dioxide. Preferably, a "gel-foaming" bifunctional catalytic system is formed by a ratio of bis(dimethylaminoethyl) ether and triethylenediamine of 1:0.8-1.5. The former preferentially catalyzes the formation of urea bonds to improve matrix strength, while the latter promotes gas release. Under this ratio, the peak temperature of the reaction exothermic curve can be controlled within the ideal range of 160±5℃.

[0025] Preferably, in step (4), the combination of the three-stage filtration structure is any one of the following:

[0026] Pre-filter C1 with pore size of 250~350 μm / Working filter B2 with pore size of 80~120 μm / Terminal filter A1 with pore size of 70~90 μm;

[0027] Pre-filter C2P with pore size of 120~160 μm / Working filter B2P with pore size of 140~180 μm / Terminal filter A1P with pore size of 140~180 μm.

[0028] The present invention provides a method for foaming with liquid carbon dioxide, which optimizes the foaming process through a three-stage pressure reduction architecture that combines physical interception and dynamic sieving. The pre-filter (C1 / C2P) uses a large-pore metal sintered mesh to intercept large particulate impurities in the raw material and prevent clogging of subsequent units. The gradient density fiber layer of the working filter (B2 / B2P) achieves dynamic adjustment within the range of 80-160μm through its asymmetric pore structure, which can ensure both throughput and maintain appropriate pressure. The terminal filter (A1 / A1P) (70-160μm) further releases pressure, promoting the vaporization, emulsification, and foaming of liquid carbon dioxide. This staged design reduces the system pressure drop step by step, and the clear division of labor among the units ensures filtration efficiency and foam core quality. The filter C1, C2P, B2, B2P, A1, and A1P in this invention represent different models, and the filter models used in the three-stage filtration structure include, but are not limited to, the models mentioned above. Preferably, in step (4), the mixing speed of the main mixing chamber is preferably 4500~5500 r / min.

[0029] Preferably, in step (4), the primary pressure of the emulsifier is 55~58 bar.

[0030] Preferably, in step (4), the pressure drop of each stage of the emulsifier is controlled within the range of 40-50%.

[0031] Preferably, in step (4), the decompression chamber of the emulsifier is equipped with a temperature control system to control the foaming temperature to 35~45℃, preferably 38~42℃.

[0032] This invention provides a method for foaming polymer polyols using liquid carbon dioxide under pressure. A stepped pressure drop design of 40-50% ensures that only a portion of the dissolved gas is released during each decompression stage. By controlling the ΔP / Δt gradient within 0.5-0.8 MPa / s, a dynamic balance between cell growth rate and polymer curing rate can be achieved. Simultaneously, a temperature control window of 35-45℃ is selected, as this parameter directly affects the Henry's constant of CO2. The preferred range of 38-42℃ keeps the gas solubility change rate within 5% / ℃, ensuring stability at the foaming front. The temperature control system uses a PID algorithm to adjust the cooling medium flow rate, achieving a temperature control accuracy of ±0.5℃.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] (1) The method for foaming polymer polyols under pressure with liquid carbon dioxide provided by the present invention significantly improves the filtration efficiency of raw materials with different viscosities and reduces the risk of clogging through a specific three-stage filtration structure combination;

[0035] (2) The method for foaming polymer polyols using liquid carbon dioxide pressurization provided by the present invention achieves a more stable foaming process through optimized pressure gradient design;

[0036] (3) The method for foaming polymer polyols using liquid carbon dioxide pressurization provided by the present invention adopts a step-by-step decompression design of the emulsifier to ensure the stable vaporization of CO2 and avoid the collapse of the foam cells. Attached Figure Description

[0037] Figure 1 The image shows the pores of a polyurethane sponge obtained by the method of polymer polyol foaming under pressure with liquid carbon dioxide provided in Example 2 of the present invention.

[0038] Figure 2 The image shows the pores of the polyurethane sponge obtained by the method of polymer polyol foaming under pressure with liquid carbon dioxide provided in Comparative Example 2 of the present invention. Detailed Implementation

[0039] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0040] It should be understood that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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. Therefore, they should not be construed as limitations on the invention. Those skilled in the art can understand the specific meaning of the above terms in this invention through the specific circumstances.

[0041] Unless otherwise specified, all chemical products mentioned in this article are commercially available products.

[0042] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0043] In one specific embodiment, the present invention provides a method for foaming polymer polyols under pressure using liquid carbon dioxide, the method comprising the following steps:

[0044] (1) 50-80 parts by weight of polyether polyol SC56-16S and / or 20-50 parts by weight of polymer polyol HS-200S are pressurized to 20-35 bar by a feed pump and a high-pressure pump and then fed into a static mixer. The static mixer is equipped with 4-6 spiral guide vanes with a spiral angle of 30-45°. At the same time, liquid carbon dioxide accounting for 1.5-3.0% of the total mass of polyol is pressurized to 15-25 bar by a pressure regulating valve. At 15-25°C, it is pressurized to 40-60 bar by a metering pump and then injected into the static mixer at a rate of 5-10% of the mass flow rate of polyol.

[0045] (2) The mixture obtained in step (1) is transported to the main mixing chamber and the pressure is reduced to 5~7 bar. At the same time, a polyether modified polysiloxane surfactant with an HLB value of 8~12 is injected, the amount of which is 0.5~1.5% of the total mass of the polyol, and a composite amine catalyst composed of dimethylaminoethyl ether and triethylenediamine in a mass ratio of 1:(0.5~2).

[0046] (3) Pressurize nitrogen to 90~110 bar and inject it into the TDI pipeline to form a TDI-nitrogen mixture, and inject it into the main mixing chamber at a pressure of 50~70 bar;

[0047] (4) After mixing at a speed of 4000~6000 r / min in the main mixing chamber, the material temperature is controlled at 35~45℃ in an emulsifier. The material is then gradually depressurized from 50~60 bar to atmospheric pressure for casting and foaming. During the depressurization process, the pressure drop at each stage is controlled within the range of 40 to 50%. The emulsifier is equipped with a three-stage filtration structure, and its pore size is selected from any combination of the following:

[0048] ① C1 pre-filter with a pore size of 250~350 μm, B2 working filter with a pore size of 80~120 μm, and A1 terminal filter with a pore size of 70~90 μm; or

[0049] ② C2P pre-filter with pore size of 120~160 μm, B2P working filter with pore size of 140~180 μm, and A1P terminal filter with pore size of 140~180 μm.

[0050] In another specific embodiment, the present invention provides a polyurethane foam sponge product, which is obtained from the above-described specific embodiments.

[0051] It should be clarified that any use of the process provided in the embodiments of the present invention or any substitution or change of conventional data falls within the protection and disclosure scope of the present invention.

[0052] Example 1:

[0053] This embodiment provides a method for foaming polymer polyols using liquid carbon dioxide under pressure, the method comprising the following steps:

[0054] (1) 100 parts by mass of polyether polyol SC56-16S are pressurized to 28 bar by a feed pump and a high-pressure pump and then fed into a static mixer. At the same time, liquid carbon dioxide accounting for 2.1% of the total mass of polyol is pressurized to 20 bar by a pressure regulating valve at 18°C, and then pressurized to 50 bar by a metering pump and injected into the static mixer at a mass flow rate of 8% to mix with polyether polyol SC56-16S. The mixer is equipped with 5 spiral guide vanes with a spiral angle of 38°.

[0055] (2) The mixture obtained in step (1) is transported to the main mixing chamber and the pressure is reduced to 5.5 bar. At the same time, a polyether-modified polysiloxane surfactant with an HLB value of 10 (1.2% dosage) and a composite catalyst with a mass ratio of bis(dimethylaminoethyl ether) to triethylenediamine of 1:1.2 are added.

[0056] (3) Based on the formula, pressurize nitrogen to 100 bar and inject it into the TDI pipeline to form a TDI-nitrogen mixture, and inject it into the main mixing chamber at a pressure of 60 bar;

[0057] (4) After mixing at a speed of 5000 r / min in the main mixing chamber, the material enters the 42℃ emulsifier and is gradually depressurized from 60 bar to atmospheric pressure, and then cast and foamed, with a pressure drop of 42% at each stage; the emulsifier is provided with the following three-stage filtration structure in sequence: C1 pre-filter with 300 μm pore size, B2 working filter with 100 μm pore size, and A1 terminal filter with 85 μm pore size.

[0058] The mass fractions and flow rates in the above scheme are shown in Table 1:

[0059] Table 1

[0060]

[0061] This embodiment also provides a polyurethane foam sponge product, which is obtained by the above method.

[0062] Example 2:

[0063] This embodiment provides a method for foaming polymer polyols using liquid carbon dioxide under pressure, the method comprising the following steps:

[0064] (1) 60 parts by mass of polyether polyol SC56-16s and 40 parts by mass of polymer polyol HS-200s are pressurized to 30 bar by a feed pump and a high-pressure pump, respectively, and then fed into a static mixer. At the same time, liquid carbon dioxide accounting for 2.5% of the total mass of polyols is pressurized to 20 bar by a pressure regulating valve at 22°C, and then pressurized to 50 bar by a metering pump and injected into the static mixer at a mass flow rate of 6% to mix with polyether polyol SC56-16s and polymer polyol HS-200s. The mixer is equipped with 6 spiral guide vanes with a spiral angle of 45°.

[0065] (2) The mixture obtained in step (1) is fed to the main mixing chamber and depressurized to 6.5 bar. At the same time, a polyether-modified polysiloxane surfactant with an HLB value of 11 (0.8% dosage) and a composite catalyst with a mass ratio of bis(dimethylaminoethyl ether) to triethylenediamine of 1:0.8 are added.

[0066] (3) Based on the formula, pressurize nitrogen to 100 bar and inject it into the TDI pipeline to form a TDI-nitrogen mixture, and inject it into the main mixing chamber at a pressure of 60 bar;

[0067] (4) After mixing at a speed of 5000 r / min in the main mixing chamber, the material enters the 38℃ emulsifier and is gradually depressurized from 60 bar to atmospheric pressure, and then cast and foamed, with a pressure drop of 48% at each stage; the emulsifier is provided with the following three-stage filtration structure in sequence: C2P pre-filter with 140 μm pore size, B2P working filter with 160 μm pore size, and A1P terminal filter with 160 μm pore size.

[0068] The mass fractions and flow rates in the above scheme are shown in Table 2:

[0069] Table 2

[0070]

[0071] This embodiment also provides a polyurethane foam sponge product, which is obtained by the above method. The polyurethane foam sponge product of this embodiment is as follows: Figure 1 As shown, the pores are uniform and there are no broken pores.

[0072] Example 3:

[0073] This embodiment provides a method for foaming polymer polyols using liquid carbon dioxide under pressure. The only difference from Example 1 is that in step (1), the CO2 injection pressure after being pressurized by a metering pump is 35 bar.

[0074] This embodiment also provides a polyurethane foam sponge product, which is obtained by the above method.

[0075] Example 4:

[0076] This embodiment provides a method for foaming polymer polyols under pressure with liquid carbon dioxide. The only difference from Example 1 is that in step (4), the pore size of the A1 terminal filter is changed to 100 μm.

[0077] This embodiment also provides a polyurethane foam sponge product, which is obtained by the above method.

[0078] Example 5:

[0079] This embodiment provides a method for foaming polymer polyols using liquid carbon dioxide pressurization. The only difference from Embodiment 1 is that in step (3), nitrogen is pressurized to 80 bar and then injected into the TDI pipeline.

[0080] This embodiment also provides a polyurethane foam sponge product, which is obtained by the above method.

[0081] Example 6:

[0082] This embodiment provides a method for foaming polymer polyols under pressure with liquid carbon dioxide. The only difference from Example 2 is that in step (1), the mass fractions of polyether polyol SC56-16s and polymer polyol HS-200S are 55 parts and 45 parts, respectively.

[0083] This embodiment also provides a polyurethane foam sponge product, which is obtained by the above method.

[0084] Comparative Example 1:

[0085] This comparative example provides a method for foaming polymer polyols under pressure using dichloromethane. The method employs a one-step process to prepare flexible polyurethane foam. As shown in Table 3, polyether polyol SC56-16s, water, silicone oil surfactant, amine catalyst, tin catalyst, dichloromethane, TDI, and other raw materials are injected into the mixing chamber according to the formulation flow rate. The mixing chamber is stirred at a speed of 5000 r / min. Then, the foam is poured into a foaming box.

[0086] Table 3

[0087]

[0088] This comparative example also provides a polyurethane foam sponge product, which is obtained by the above method.

[0089] Comparative Example 2:

[0090] This comparative example provides a method for foaming polymer polyols using liquid carbon dioxide under pressure. The only difference between this method and Example 2 is that in step (2), the mixture is transported to the main mixing chamber and depressurized to 4.5 bar, while in step (4), the pore size of the B3P working sheet is 200 μm.

[0091] The mass fractions and flow rates in the above scheme are shown in Table 4:

[0092] Table 4

[0093]

[0094] This comparative example also provides a polyurethane foam sponge product, which is obtained by the above method. The polyurethane foam sponge product of this comparative example is as follows: Figure 2 As shown, there are obvious irregular and broken pores. Compared with Example 2, Comparative Example 2 reduced the mixing head pressure from 6.5 bar to 4.5 bar under the same formulation, and changed the pore size of the filter in the emulsifier from B2p to B3p, which affected the phase state of carbon dioxide in the mixing chamber and emulsifier, ultimately resulting in uneven carbon dioxide vaporization.

[0095] The performance of the polyurethane foam products of Examples 1-6 and Comparative Examples 1-2 was tested, and the test results are shown in Table 5:

[0096] Table 5

[0097]

[0098] From the test results in Table 1, we can see that:

[0099] (1) The indentation hardness, tensile strength and ball rebound performance in Examples 1-6 are significantly better than those in Comparative Examples 1-2, indicating that the present invention significantly improves the mechanical properties and cell structure uniformity of polyurethane foam by optimizing CO2 injection pressure, filtration system design and nitrogen-assisted dispersion process.

[0100] (2) Comparing Examples 1 and 3-5, it can be seen that in Example 3, the CO2 injection pressure was reduced to 35 bar, resulting in an increase in the bubble diameter and a decrease in tensile strength of 6.7%; in Example 4, the pore size of the terminal filter increased to 100 μm, which reduced the rebound performance of the falling ball by 2%; and in Example 5, the nitrogen pressure was reduced to 80 bar, resulting in bubble merging and a decrease in tensile strength of 8.1%. This indicates that precise control of each process parameter is crucial to product performance.

[0101] (3) Comparing Example 2 and Example 6, it can be seen that, since the polyol ratio was adjusted in Example 6 (55:45), although the indentation hardness was basically maintained, the tensile strength decreased by 1.7% and the ball rebound performance decreased by 2.4%, proving that the 60:40 ratio in Example 2 was the optimal choice.

[0102] (4) Comparing Example 1 and Comparative Example 1, it can be seen that Comparative Example 1, which uses the traditional dichloromethane foaming process, has a 9.1% reduction in indentation hardness, a 22.2% reduction in tensile strength, and a 18.3% reduction in elongation at break, which fully demonstrates the superiority of the liquid CO2 foaming process.

[0103] (5) Comparing Example 2 and Comparative Example 2, it can be seen that Comparative Example 2 has a disordered pore and broken pore phenomenon due to the low pressure (4.5 bar) and insufficient filtration accuracy (200 μm). The ball rebound performance is reduced by 7.3% and the tensile strength is reduced by 8.7%, which further verifies the necessity of the process parameter combination of the present invention.

[0104] In summary, the method for foaming polymer polyols using liquid carbon dioxide pressurization provided by this invention significantly improves the mechanical properties and cell uniformity of polyurethane foam sponge while maintaining low density by optimizing the liquid CO2 injection pressure, the three-stage filtration system design, and the nitrogen-assisted dispersion process, achieving the optimal balance of "low density-high strength-high elasticity".

[0105] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for foaming polymer polyols under pressure using liquid carbon dioxide, characterized in that, The method includes the following steps: (1) Polyether polyol SC56-16S and polymer polyol HS-200S with a mass ratio of (50~80):(20~50) are pressurized to 20~35 bar by a feed pump and a high pressure pump and then fed into a static mixer. At the same time, liquid carbon dioxide of 1.5~3.0% of the total mass of polyols is pressurized to 40~60 bar and injected into the static mixer to mix with the polyols. (2) The mixture obtained in step (1) is transported to the main mixing chamber and the pressure is reduced to 5-7 bar. At the same time, silicone oil surfactant, amine catalyst and tin catalyst are injected into the main mixing chamber. (3) Inject pressurized nitrogen at 90~110 bar into the toluene diisocyanate pipeline to form a TDI-nitrogen mixture, and inject it into the main mixing chamber at a pressure of 50~70 bar; (4) After mixing at a speed of 4000~6000 r / min in the main mixing chamber, the material enters the emulsifier and is gradually depressurized to atmospheric pressure by 50~60 bar before being poured and foamed; the emulsifier is equipped with a three-stage filtration structure, which includes: Pre-filter with a pore size of 100~350 μm; Working filter element with a pore size of 80~160 μm; Terminal filter with a pore size of 70~160 μm.

2. The method according to claim 1, characterized in that, In step (1), the static mixer is equipped with 4 to 6 spiral guide vanes with a spiral angle of 30 to 45°, and the liquid carbon dioxide injection rate is 5 to 10% of the mass flow rate of the polyol.

3. The method according to claim 1, characterized in that, In step (1), the injection pressure of liquid carbon dioxide is 45~55 bar, and in step (3), the pressurization pressure of nitrogen is 95~105 bar.

4. The method according to claim 1, characterized in that, In step (2), the HLB value of the silicone oil surfactant is 9~11.

5. The method according to claim 1, characterized in that, In step (2), the mass ratio of bis(dimethylaminoethyl) ether to triethylenediamine in the amine catalyst is 1:(0.8~1.5).

6. The method according to claim 1, characterized in that, In step (4), the combination of the three-stage filtration structure can be any of the following: Pre-filter C1 with pore size of 250~350 μm / Working filter B2 with pore size of 80~120 μm / Terminal filter A1 with pore size of 70~90 μm; Pre-filter C2P with pore size of 120~140 μm / Working filter B2P with pore size of 140~160 μm / Terminal filter A1P with pore size of 140~160 μm.

7. The method according to claim 1, characterized in that, In step (4), the mixing speed of the main mixing chamber is 4500~5500 r / min.

8. The method according to claim 1, characterized in that, In step (4), the initial decompression pressure of the emulsifier is 55~58 bar.

9. The method according to claim 1, characterized in that, In step (4), the pressure drop of each stage of the emulsifier is controlled within the range of 40-50%.

10. The method according to claim 1, characterized in that, In step (4), the decompression chamber of the emulsifier is equipped with a temperature control system to control the foaming temperature to 35~45℃.

11. The method according to claim 10, characterized in that, Control the foaming temperature to 38~42℃.

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