A foaming process for low-carbon carbon dioxide-based polyether polyol sponges

Abstract

This invention relates to the technical field of general processing and batching processes, and discloses a foaming process for low-carbon carbon dioxide-based polyether polyol sponges, including: establishing a constant-pressure circulation path for carbon dioxide-based polyether polyols; introducing polyols into a mixing chamber and pulse-injecting isocyanate within a preset delay time to generate a pressure gradient; implementing a two-stage step depressurization; collecting isocyanate pulse drive signals as a reference phase benchmark; controlling the dynamic back pressure throttle valve at the outlet to unload in the offset phase, generating a transient pressure drop wave; guiding the material in the mixing chamber to undergo elastic displacement; and restoring the flow field to its initial state. This invention actively intervenes in the fluid elastic memory through an anti-phase back pressure compensation mechanism, eliminates flow hysteresis residue, ensures that the pulse period has a consistent physical flow field background, calibrates the nucleation rate and distribution of gas nuclei, and improves the homogeneity and isotropic properties of the sponge.

Description

Technical Field

[0001] This invention relates to a foaming process for low-carbon carbon dioxide-based polyether polyol sponges, belonging to the technical field of general processing and formulation processes. Background Technology

[0002] Current foaming processes employ constant high-pressure impact mixing, achieving material mixing by adjusting component pressure and flow ratio. However, the processing of high-viscosity carbon dioxide-based polyether polyols suffers from nucleation kinetic lag. The material transitions from a high-pressure liquid state to a normal-pressure gas-solid state, and the system viscosity hinders the uniform precipitation of gas nuclei. This leads to transient supersaturation and accumulation of carbon dioxide in the mixing chamber, and the energy accumulation induces uncontrollable explosive nucleation, resulting in density gradients or cell fissures in the sponge.

[0003] Existing technologies improve mixing quality by increasing mixing pressure or implementing global temperature control. However, increased pressure induces over-shearing of materials, causing thinning of bubble walls. Temperature control methods suffer from physical response lag and cannot capture transient viscosity fluctuations when materials enter the mixing head. Single linear adjustment methods cannot achieve precise coupling between the mixing energy field and nucleation timing, making it difficult to eliminate physical intervention caused by the elastic memory of high-viscosity materials. For example, Chinese invention patent CN115785425A discloses a carbon dioxide-based polycarbonate-polyether block polyol and its preparation method. It utilizes a non-metallic Lewis acid-base pair catalytic system to achieve green synthesis and improve thermal stability. During the foaming process, the block polyol has strong non-Newtonian fluid characteristics and viscoelastic memory effect. Existing processes remain at the level of raw material synthesis or static property improvement, lacking a precise decoupling scheme between high-frequency pulse injection environment micro-shear energy injection and gas phase nucleation timing. In continuous production, pressure reflection standing wave energy superposition occurs in the mixing chamber, failing to eliminate product density deviation and skin effect caused by elastic stress accumulation.

[0004] Therefore, how to achieve precise decoupling between the microscopic shear energy injection and gas-phase nucleation timing of high-viscosity materials, and construct a nucleation template with spatial and temporal consistency in a complex flow field environment, has become the technical problem to be solved by this invention. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: A foaming process for low-carbon carbon dioxide-based polyether polyol sponge, comprising the following steps:

[0006] Step S1: Establish a material conveying path so that the carbon dioxide-based polyether polyol can... MPa to Constant pressure cycling is performed at a first preset pressure of MPa;

[0007] Step S2: Open the mixing channel and introduce carbon dioxide-based polyether polyol into the mixing chamber;

[0008] Step S3, after the introduction of carbon dioxide-based polyether polyol ms to Within a preset delay time of ms, isocyanate components are injected into the mixing chamber; wherein, the isocyanate components are in the form of... Hz to A pulse is injected at a preset frequency of Hz to generate a transient pressure gradient in the mixing chamber for material mixing;

[0009] Step S4: Guide the mixture to the outlet and perform a two-stage stepped pressure unloading to induce controlled nucleation of carbon dioxide; the two-stage stepped pressure unloading includes a first stage of depressurization to an intermediate equilibrium pressure and a second stage of depressurization to atmospheric pressure;

[0010] Step S5: In the second-stage step pressure unloading stage, the pulse injection drive signal of the isocyanate component is acquired in real time, and the falling edge of the pulse injection drive signal is used as the reference phase reference.

[0011] Step S6: Control the dynamic back pressure throttle valve at the discharge port after the reference phase reference. An unloading action is performed at the bias phase, causing an amplitude of [value missing] to be generated in the mixing chamber during the gap when the isocyanate component stops being injected. MPa to The transient pressure drop wave of MPa induces the material in the mixing chamber, which is under compression, to undergo forced elastic displacement towards the discharge port. Before the next pulse injection of the isocyanate component, the material flow field in the mixing chamber is restored to the static initial state.

[0012] Preferably, the intermediate equilibrium pressure in the two-stage stepped pressure unloading is set to the mixed chamber pressure. to During the second stage of depressurization to atmospheric pressure, a lubricating fluid is introduced circumferentially into the inner wall of the discharge port, forming an envelope slip layer around the material flow. The lubricating fluid has a flow rate lower than the total flow rate of the carbon dioxide-based polyether polyol. Carbon dioxide-based polyether polyols without nucleation auxiliary gases; by reducing the velocity gradient difference between the central fluid and the wall surface through the enveloping slip layer, the radial force environment of the carbon dioxide nucleation points tends to be symmetrical.

[0013] Preferably, the pulse injection stage in step S3 further includes: real-time monitoring of the pressure drop per unit length of the carbon dioxide-based polyether polyol in the material conveying path, and defining it as a flow characterization parameter. Establish flow regime characterization parameters The inverse mapping rule with the pulse on-width of the isocyanate component; when the flow characterization parameters When the pulse width decreases, the pulse opening width of the isocyanate component is automatically reduced according to the reverse mapping rule to compensate for the shear energy overflow caused by the decrease in material viscosity.

[0014] Preferably, the transient pressure drop wave in step S6 is achieved by adjusting the slope of the rising edge of the dynamic back pressure throttle valve; the slope of the rising edge generates a coherent pressure field at the outlet to offset the normal stress difference of the material, thereby reducing the elastic recovery of the material stream when it leaves the mixing chamber.

[0015] Preferably, the pressure reflection residual wave generated by the pulse injection of the isocyanate component induces periodic shear disturbance on the inner wall of the mixing chamber; by adjusting the feeding pressure waveform of the carbon dioxide-based polyether polyol, pressure fluctuation is generated at the end of each pulse cycle, and the pressure fluctuation and the pressure reflection residual wave are superimposed in amplitude in the boundary layer region of the inner wall to peel off the material retention layer on the inner wall.

[0016] Preferably, the preset frequency in the pulse injection step Characteristic relaxation time constants of molecular chain segments with carbon dioxide-based polyether polyols at mixing temperatures The logical resonance constraint is satisfied, and the logical resonance constraint satisfies the formula: ,in, The preset hybrid correlation coefficient, and The range of values ​​is to The accumulation of elastic stress when the material stream leaves the outlet is reduced by using logical resonance constraints.

[0017] Preferably, before the start of each pulse injection cycle of the isocyanate component, the following step is further included: applying a pressure with a first preset value. to The leader micro-perturbation signal is captured; the echo energy distribution characteristics generated by the leader micro-perturbation signal in the mixing chamber are captured, and the attenuation coefficient of the echo envelope is calculated; the pulse opening width is corrected according to the attenuation coefficient to compensate for the nucleation stability drift caused by the fluctuation of carbon dioxide pre-dissolution state.

[0018] Preferably, at the instant the pulse injection of the isocyanate component is stopped, the pressure relief circuit connected to the mixing chamber is simultaneously opened; the pressure relief circuit guides the pressure reflection standing wave energy in the mixing chamber to the material conveying path to eliminate the pressure peak caused by the superposition of high-frequency pulses.

[0019] Preferably, pulse injection is achieved by controlling the duty cycle of the solenoid valve switching in the isocyanate component channel; the residence time at the intermediate equilibrium pressure is not less than [missing information]. s.

[0020] Preferably, in step S1, the circulation speed of the material conveying path is adjusted by a variable frequency pump so that the Reynolds number of the carbon dioxide-based polyether polyol is at a certain level before entering the mixing chamber. to Within the range.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. In the foaming of carbon dioxide-based polyether polyol sponges, the shear energy injection of carbon dioxide-based polyether polyols and the gas-phase nucleation time sequence are decoupled by asymmetric pulse injection and two-stage step-like pressure unloading logic coupling. The injection generates a local transient pressure gradient, which forcibly intervenes in the kinetic path of carbon dioxide conversion from the solvent state to the gas nucleus state, eliminating energy accumulation caused by the kinetic lag of nucleation due to material polarity, avoiding uncontrollable explosive nucleation, and enabling stable precipitation of gas nuclei under a controlled pressure gradient. The flow resistance feedback of the material conveying path is used to establish a pulse energy compensation and transient viscosity drift mapping. When the flow resistance changes due to the mechanical shear heat of the material, the pulse opening width is calibrated in real time according to the flow feedback to adjust the shear work injection per unit volume, avoiding over-shearing or insufficient mixing kinetic energy caused by material viscosity fluctuations, maintaining the spatial topological stability of the microcellular structure during processing, and eliminating the performance differences between the sponge edge material and the core material.

[0023] 2. By utilizing the pressure reflection residual wave generated by the main pulse injection, periodic shear disturbances are induced in the mixing chamber wall, breaking the microscopic retention layer formed by the material at the zero-velocity boundary layer; in conjunction with the low-shear environment constructed by the envelope slip layer at the discharge end, the velocity gradient difference between the central fluid and the wall surface is reduced, making the carbon dioxide nucleation points more symmetrical in the radial stress environment, eliminating the edge densification effect caused by uneven radial shear stress distribution, and unifying the porosity and compression resilience modulus of the product from the center to the edge; the pulse frequency is adjusted to logically resonate with the relaxation frequency of molecular chain segments at a specific temperature of the material, and mechanical pressure fluctuation interference is used to induce in-situ conformational adjustment of macromolecular chain segments; a coherent pressure field is generated by the pulse execution unit to counteract the accumulation of elastic internal stress generated during the high-speed ejection of high-viscosity materials, eliminating the extrusion swelling phenomenon at the outlet.

[0024] 3. During the non-working interval of the pulse injection cycle, apply a small pressure disturbance and analyze the pressure echo signal attenuation coefficient to invert and sense the microscopic solvation depth of carbon dioxide inside the material; adjust the pulse opening width and delay time in real time according to the acoustic impedance characteristics to compensate for the presaturation degree drift caused by the fine adjustment of the ambient air pressure, so that the foaming process has the ability to resist the fluctuation of raw material pretreatment and ensure the reliability of the physical performance of the sponge products throughout the entire life cycle. Attached Figure Description

[0025] Figure 1 This is a block diagram of the pulse injection and bias unloading control logic for the logical resonance constraint of this invention;

[0026] Figure 2 This is a graph showing the logical resonance relationship between the pulse frequency and the characteristic relaxation time constant of the molecular chain segment in this invention.

[0027] Figure 3 This is a flowchart of the two-stage stepped pressure unloading process for constructing the collaborative envelope slip layer of this invention. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are intended to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0029] A foaming process for low-carbon carbon dioxide-based polyether polyol sponge includes the following steps: Step S1, establishing a material conveying path, and using a variable frequency pump to adjust the circulation speed of the material conveying path, so that the carbon dioxide-based polyether polyol... MPa to The mixture is subjected to constant pressure cycling at a first preset pressure of MPa. Before entering the mixing chamber, the Reynolds number of the carbon dioxide-based polyether polyol is at a certain value. to Within the specified range, maintain the critical solubility state of carbon dioxide in the polyol system. Step S2: Open the mixing channel and introduce the carbon dioxide-based polyether polyol into the mixing chamber. Step S3: After the introduction of the carbon dioxide-based polyether polyol... ms to Within a preset delay time of ms, isocyanate components are injected into the mixing chamber, and the isocyanate components are... Hz to A pulse injection is performed at a preset frequency of Hz to generate a transient pressure gradient for material mixing in the mixing chamber. The pulse injection is achieved by controlling the duty cycle of the solenoid valve in the isocyanate component channel. In the pulse injection stage of step S3, the pressure drop per unit length of the carbon dioxide-based polyether polyol in the material conveying path is monitored in real time and defined as a flow characterization parameter. The system is based on the established flow regime characterization parameters. The flow regime is controlled by an inverse mapping rule to the pulse on-width of the isocyanate component, when the flow regime characterization parameters... During reduction, the pulse opening width of the isocyanate component is automatically shortened to compensate for the shear energy overflow caused by the decrease in material viscosity; in the pulse injection step, a preset frequency is used. Characteristic relaxation time constants of molecular chain segments with carbon dioxide-based polyether polyols at mixing temperatures The logical resonance constraint is satisfied, and the logical resonance constraint satisfies the formula: ,in, The pulse frequency is expressed in Hz. is the characteristic relaxation time constant of the molecular chain segment, in seconds; The preset hybrid correlation coefficient, and The range of values ​​is to By using logical resonance constraints, the accumulation of elastic stress when the material stream leaves the outlet is reduced.

[0030] Before the start of each pulse injection cycle of the isocyanate component, an application of a pressure with a first preset value is also included. to The system captures the echo energy distribution characteristics generated by the leader micro-perturbation signal in the mixing chamber and calculates the attenuation coefficient of the echo envelope. Based on the attenuation coefficient, the pulse opening width is corrected to compensate for the nucleation stability drift caused by fluctuations in the carbon dioxide pre-dissolving state. In step S4, the mixed material is guided to the outlet, and a two-stage stepped pressure unloading is performed to induce controlled carbon dioxide nucleation. The two-stage stepped pressure unloading includes a first stage of depressurization to an intermediate equilibrium pressure and a second stage of depressurization to atmospheric pressure. The intermediate equilibrium pressure is set to the pressure within the mixing chamber. to The residence time of the mixture under intermediate equilibrium pressure shall not be less than During the second stage of depressurization to atmospheric pressure, lubricating fluid is introduced circumferentially into the inner wall of the discharge port to form an envelope slip layer around the material flow. The flow rate of the lubricating fluid is lower than the total flow rate of the carbon dioxide-based polyether polyol. The carbon dioxide-based polyether polyol without nucleation auxiliary gas reduces the velocity gradient difference between the central fluid and the wall surface through an encapsulation slip layer, making the radial stress environment of the carbon dioxide nucleation points more symmetrical; in step S5, during the two-stage step pressure unloading stage, the pulse injection drive signal of the isocyanate component is collected in real time, and the falling edge of the pulse injection drive signal is used as the reference phase reference; in step S6, the dynamic back pressure throttle valve at the outlet is controlled after the reference phase reference. An unloading action is performed at the bias phase, generating an amplitude of [value missing] during the gap when the isocyanate component stops being injected. MPa to The transient pressure drop wave of MPa induces a forced elastic displacement of the material in the mixing chamber under compression towards the discharge port. Before the next pulse injection of the isocyanate component, the material flow field in the mixing chamber is restored to its static initial state. In step S6, the transient pressure drop wave is generated by adjusting the rising slope of the dynamic back pressure throttle valve to generate a coherent pressure field at the discharge port to offset the normal stress difference of the material and reduce the elastic recovery of the material stream when it leaves the mixing chamber. At the same time, the process uses the pressure reflection residual wave generated by the pulse injection of the isocyanate component to induce periodic shear disturbance on the inner wall of the mixing chamber. By adjusting the feed pressure waveform of the carbon dioxide-based polyether polyol, pressure fluctuations are generated at the end of each pulse cycle. The pressure fluctuations and the pressure reflection residual wave are superimposed in the boundary layer region of the inner wall, stripping the material retention layer on the inner wall. At the moment the pulse injection of the isocyanate component ends, the pressure relief circuit connected to the mixing chamber is opened simultaneously to guide the pressure reflection standing wave energy in the mixing chamber into the material conveying path.

[0031] Example 1: In the continuous production of high-viscosity carbon dioxide-based polyether polyol sponges, due to the non-Newtonian fluid characteristics and viscoelastic memory effect of carbon dioxide-based polyether polyols during flow, when isocyanate components are injected using conventional constant pressure, the high-viscosity material in the mixing chamber forms a physical displacement barrier due to the lag in flow response. This restricts the diffusion of isocyanate in the mixing zone, causing excessive aggregation of carbon dioxide nucleation points in local areas. Consequently, radial density deviations occur in the cell structure of the sponge product. The system establishes a first preset pressure of... MPa and Reynolds number is The material conveying path, in which carbon dioxide-based polyether polyol is introduced into the mixing chamber After ms, initiate pulse injection of the isocyanate component, setting the preset frequency to [value missing]. Hz, and simultaneously monitor flow regime characterization parameters. To adjust the opening pulse width of the solenoid valve in real time.

[0032] During this process, the dynamic back pressure throttle valve acquires the falling edge of the isocyanate injection signal as a reference phase, and then... An unloading action is performed at the offset phase of degrees, producing an image with a value of A transient pressure drop wave of MPa generates a suction effect that forcibly pulls the retained material in the mixing chamber toward the discharge port, causing the residual pressure field in the mixing chamber to return to its static initial state before the next pulse begins; the pulse injection process follows logical resonance constraints and a preset frequency. Satisfying the formula: ,in, The pulse frequency is expressed in Hz. is the characteristic relaxation time constant of the molecular chain segment, in seconds; The preset hybrid correlation coefficient has a value of [value missing]. When the material flows to the discharge port, a two-stage stepped pressure unloading process is implemented, and the material remains under the intermediate equilibrium pressure. After unloading under atmospheric pressure, the wall velocity gradient is maintained within a preset range by utilizing the envelope slip layer introduced by the micropores in the inner wall of the discharge port.

[0033] Example 2: The performance of the foaming process for low-carbon carbon dioxide-based polyether polyol sponge was verified on a material mixing verification platform equipped with a high-frequency electromagnetic drive valve. The sampling frequency of the pressure monitoring unit in the test platform was set to [value missing]. Hz, measurement resolution is MPa, the flow meter's measurement accuracy is not less than By injecting into the delivery path with A wideband pressure noise with a signal-to-noise ratio of dB is used to simulate the mechanical vibration interference generated by the switching of the variable frequency pump. Quantitative data are used to reveal the mechanism of the anti-phase backpressure compensation mechanism and the logic resonance constraint on the calibration of the spatial distribution of carbon dioxide nuclei.

[0034] The setting of key process parameters is based on a trade-off between material rheological properties and processing stability, among which the characteristic relaxation time constant of molecular chain segments is crucial. The calibration procedure utilizes a rotational rheometer to perform small-amplitude oscillatory shear tests on carbon dioxide-based polyether polyols under isothermal conditions to obtain the intersection frequency of the storage modulus and the loss modulus, and to measure the reference operating conditions. for s, and based on the logic resonance constraint formula, the preset frequency is... Anchored at Hz, at this point, the mixed correlation coefficient Values The sampling period is set based on the characteristic period of the transient pressure wave in the mixed indoor environment, and its sampling frequency is higher than the pulse frequency. To avoid signal aliasing, the test scheme includes: sample groups 1-3 of the present invention, comparison sample group 1 with the anti-phase back pressure compensation action removed, and the first preset pressure. Comparative sample groups 2 and 3 are set outside the required protection range, and comparative sample group 4 is set due to resonance failure caused by improper pulse frequency setting.

[0035] Table 1: Summary of Experimental Data on the Processing Technology of Carbon Dioxide-Based Polyether Polyol Sponge Foaming

[0036]

[0037] Referring to the data evolution pattern shown in Table 1, within the range of sample groups 1 to 3 of this invention, the transient pressure drop wave generated by the anti-phase backpressure compensation mechanism induces a forced elastic displacement of the material in the mixing chamber under compression towards the discharge port. This eliminates the viscoelastic memory accumulation of the material within each pulse cycle, maintaining the bubble diameter deviation of the product within a certain range. The following describes the situation in comparison group 1: After the unloading action was removed, the flow field in the mixing chamber experienced energy accumulation due to flow response lag, leading to inaccurate distribution of carbon dioxide nucleation points and a deterioration in pore uniformity. The data from the out-of-range comparison sample group showed a performance inflection point, when... Below At MPa, uncontrolled carbon dioxide leakage occurs, leading to explosive nucleation, while when Exceed The overshear heat induced by the pressure at MPa resulted in localized thermal degradation of the polyol, verifying the role of the first preset pressure range in maintaining the critical dissolved state of carbon dioxide. This experiment confirmed the physical synergy between logical resonance constraint and the two-stage stepped pressure unloading process. Sample group 1 of this invention applied an amplitude of the first preset pressure. The pulse opening width is corrected in real time by calculating the attenuation coefficient of the echo envelope based on the leading micro-perturbation signal, and the measurement deviation of the carbon dioxide nucleation rate is no higher than [missing information]. During the two-stage stepped pressure unloading phase, a flow rate lower than the total flow rate of the polyol is introduced. The lubricating fluid forms an envelope slip layer, reducing the shear stress on the outlet wall. The above eliminates the stretching of the product's skin pores caused by the radial velocity gradient.

[0038] Example 3: This example combines Figures 1 to 3 The foaming process of a low-carbon carbon dioxide-based polyether polyol sponge is described, such as... Figure 1 As shown, the control logic of this process obtains the relaxation time constant based on the material rheological properties. Input it into the logic resonance constraint calculation module, according to the formula The preset frequency f is calculated and transmitted to the pulse injection control logic; simultaneously, the pressure monitoring unit collects the pressure drop value per unit length in real time to execute the flow characterization parameters. Calculate, will generate The parameters are fed back to the pulse injection control logic. On the other hand, the characteristics of the pilot micro-perturbation echo are captured and transmitted to the perturbation echo attenuation coefficient analysis module. The correction coefficient generated by the calculation is also input to the pulse injection control logic. After integrating the above signals, the pulse injection control logic outputs a switch duty cycle or pulse opening width command to control the isocyanate channel solenoid valve, and outputs a pulse injection drive signal to the phase reference acquisition and bias calculation module, and generates a 180-degree bias signal for unloading action command. Finally, it controls the dynamic back pressure throttle valve at the discharge port to perform the corresponding action and obtains the characteristic relaxation time constant of the molecular chain segment. Procedure: A small-amplitude oscillatory shear test was performed on carbon dioxide-based polyether polyols under isothermal conditions using a rotational rheometer to obtain the storage modulus. With loss modulus With angular frequency Extracting the intersection frequency from the change curve satisfy ,calculate Real-time calibration Inject logical resonance constraint calculation module, according to formula Solving for the preset frequency If the ambient temperature fluctuates Drift triggers a frequency compensation mechanism: where, The characteristic relaxation time constant of molecular chain segments under the current processing conditions is obtained by real-time monitoring using a rotational rheometer, with units of . ; To the reference temperature control point (e.g.) The characteristic relaxation time constant of the reference molecular chain segment, calibrated, in units of When real-time monitoring value The logic resonant module inversely reduces the output frequency. This allows the pulse period to be synchronized with the polymer chain conformation adjustment period, thus suppressing sponge extrusion swelling and material normal stress accumulation.

[0039] like Figure 2 As shown, the horizontal axis represents the characteristic relaxation time constant of the molecular chain segment. The unit is seconds (s), with values ​​ranging from 0.01s to 0.03s. The vertical axis represents the pulse frequency f, with units in Hz, ranging from 30 to 120. The graph contains three lines based on different hybrid correlation coefficients. The function curves plotted are as follows: =1.0 ideal resonance, =0.8 lower limit and =1.2 upper limit, all three indicate that with the characteristic relaxation time constant of molecular chain segments. As the value increases, the pulse frequency f exhibits a non-linear decreasing trend, and all discrete data points fall within the envelope interval formed by the upper and lower limit curves; for example... Figure 3 As shown, the process begins in an initial high-pressure state, where the mixture is under high pressure in the mixing chamber and is ready to start the depressurization process. The first stage of depressurization begins, where the pressure drops to an intermediate equilibrium pressure and is maintained for a residence time that is not less than a preset value. During this period, a lubricating fluid pump is used to introduce lubricating fluid circumferentially into the inner wall of the outlet to perform the envelope slip layer formation step. This forms an envelope slip layer on the outer periphery of the material and reduces the wall velocity gradient difference. Then, the second stage of depressurization begins, where the pressure drops to atmospheric pressure, achieving controlled nucleation of carbon dioxide. Finally, the nucleation control is completed, and the gas nuclei are evenly distributed radially. The material enters the forming space and is finally discharged into the atmosphere after the bubble structure is stably formed.

[0040] Example 4: Temperature generated during the processing of carbon dioxide-based polyether polyol sponges Under operating conditions with fluctuating temperatures within a certain range, the apparent viscosity of carbon dioxide-based polyether polyol decreases nonlinearly with increasing temperature. This causes a shift in the energy density of the transient shear field generated during the pulsed injection of the isocyanate component, inducing premature precipitation of carbon dioxide in the mixing zone and the formation of large bubbles. The system executes the initial state definition procedure to determine the reference Reynolds number of carbon dioxide-based polyether polyol in the material conveying path as follows: And establish flow regime characterization parameters Pulse opening width with isocyanate component Correction algorithm, flow regime characterization parameters The quantitative procedure utilizes differential pressure sensors installed at both ends of the delivery pipeline to collect the pressure drop per unit length, substitutes it into Darcy's formula to calculate the apparent viscosity, and to compensate for the decrease in flow resistance caused by the viscosity drop, the system executes an isocyanate injection pulse opening width... Closed-loop control, pulse opening width Satisfying the formula: ,in, The corrected pulse on-width is expressed in milliseconds (ms). The reference pulse opening width is set to a value in this embodiment. ms; These are flow regime characterization parameters measured in real time. To correspond to the reference flow regime characterization parameters set at the temperature control point, when the temperature rises, the real-time measured... Below At that time, the control unit is reduced proportionally. This ensures that the kinetic energy injected into the mixing chamber in each cycle reaches a physical balance with the viscoelastic consumption of the material.

[0041] In response to fluctuations in the carbon dioxide solvation depth, the process applies a pressure with an amplitude of a first preset value before the start of each pulse injection cycle of the isocyanate component. The system captures the echo envelope of the pilot micro-perturbation signal through acoustic transducers mounted on the walls of the hybrid chamber, and extracts its exponential attenuation coefficient. Exponential decay coefficient It is positively correlated with the effective volumetric modulus of carbon dioxide in the polyol system, when the exponential decay coefficient As the value increases, it is determined that the solvation gap between carbon dioxide molecules decreases and the solubility stability decreases, based on the exponential decay coefficient. The deviation amount affects the aforementioned corrected pulse opening width By superimposing negative feedback gain, local supersaturation is reduced by shortening the injection time, and a pressure relief circuit connected to the mixing chamber is simultaneously opened at the moment the pulse injection action ends. This guides the pressure reflection standing wave energy in the mixing chamber to the material conveying path, eliminating the pressure peaks caused by the superposition of high-frequency pulses. In the two-stage stepped pressure unloading process, the intermediate equilibrium pressure is set based on the carbon dioxide content... The saturated vapor pressure at the mixing temperature of ℃ was determined, and the intermediate equilibrium pressure was set to... MPa, which is the pressure inside the mixed chamber. The residence time of the mixture under this pressure is set to The procedure for determining the residence time is based on the gas nucleus growth rate model. When the residence time is not less than... At time s, the pressure difference between the gas nucleus and the surrounding liquid phase tends to balance, suppressing explosive nucleation during the unloading process to atmospheric pressure. Simultaneously, the system maintains the lubricating fluid flow rate. The regulation procedure for real-time extraction of the main flow rate of carbon dioxide-based polyether polyols. And drive the micro-metering pump to introduce a flow rate of [missing information] through the circumferential micropores on the inner wall of the outlet. The lubricating fluid forms a thickness of [thickness value missing] on the inner wall of the discharge port. m to The envelope slip layer of m transfers the shear stress at the wall from... kPa decreased to kPa, to offset the outward extrusion and expansion of the central fluid due to the velocity gradient difference, resulting in a final sponge product with an average cell diameter distribution within... m to The m interval has no density gradient in the radial section.

[0042] Example 5: In the sponge processing condition after batch change of carbon dioxide-based polyether polyol raw materials, due to the fluctuation of the initial viscosity of different batches of materials, the system performs pre-calibration. In the initial circulation stage after the material conveying path is started, the variable frequency pump is controlled to... At the reference temperature of ℃ The material is driven by a first preset pressure of MPa, and the pipe diameter of the measuring section is collected by the pressure monitoring unit. And the length is Pressure difference at both ends of the measuring section and combined with material flow Calibration reference flow regime characterization parameters Reference flow regime characterization parameters The calibration satisfies the formula: ,in, For reference flow regime characterization parameters, This refers to the inner diameter of the pipe, in meters (m). The measurement unit is Pa; The measurement segment length is in meters (m). Volumetric flow rate, unit: m³ 3 / s; The calibration results are stored in the control unit and used as the pulse on-time width for correcting the isocyanate component. The dynamic baseline ensures that different batches of raw materials are in a consistent initial flow state before being introduced into the mixing chamber.

[0043] During the carbon dioxide pre-dissolution state confirmation stage, to eliminate signal fluctuations caused by differences in the installation position of the acoustic transducers, the process flow implements echo reference calibration. Before the carbon dioxide-based polyether polyol reaches the first preset pressure and before the isocyanate component is injected, the system sends an image with a value of [value missing] to the mixing chamber. A pulse excitation signal of MPa is used to capture the initial echo energy envelope reflected from the wall of the mixing chamber, and the corresponding no-load attenuation coefficient is calculated. As the amount of dissolved carbon dioxide increases, the system extracts the current real-time attenuation coefficient by monitoring the changes in the echo envelope of the leader micro-perturbation signal. And based on the deviation To determine the solubility depth of carbon dioxide, when the deviation amount In continuous The stability and rate of change within each sampling period are lower than At that time, it is determined that carbon dioxide has reached dissolution equilibrium in the polyol system; the system will record the deviation. The nucleation state of the batch is locked as the identification benchmark, and the pressure field is coordinated with the residence time parameter of the two-stage stepped pressure unloading stage to keep the critical radius of the gas nucleus in the preset energy steady state range during the material flow to the outlet.

[0044] Example 6: In the case of on-site deployment of a mixing unit, due to the difference in mechanical response characteristics between the electromagnetic drive valve and the dynamic back pressure throttle valve, a time-domain offset occurs. The system implements a standardized pre-calibration procedure, filling the material conveying path with a non-reactive test fluid of reference viscosity, and utilizing a sampling frequency of... The Hz pressure monitoring unit acquires the pressure pulse waveform at the isocyanate injection point and the pressure drop waveform at the outlet, and calculates the time difference between the peak injection pressure and the trough pressure drop. Calibration phase offset Phase offset The calculation satisfies the formula: ,in, This is the phase offset, in degrees; The pulse frequency is expressed in Hz. The measured time difference is expressed in seconds; the control unit uses the obtained time difference... Compensation for the execution time of the drive command of the dynamic back pressure throttle valve ensures that the transient pressure drop wave accurately acts on the hysteresis phase interval after the pulse injection of the isocyanate component stops at the physical flow field level.

[0045] In addition, a calibration procedure for implementing logical resonance constraints in the process flow is used to address the viscoelastic characteristic drift caused by the replacement of carbon dioxide-based polyether polyol raw materials, maintaining the main flow rate of carbon dioxide-based polyether polyol before material processing. Constant, driven by the controller to execute the isocyanate component channel Hz to The variable frequency injection scanning at Hz utilizes a laser diameter gauge at the outlet to monitor the expansion ratio of the flow beam after leaving the outlet to extract the elastic recovery strength curve. When the elastic recovery strength reaches its minimum value, the preset frequency is determined. With the characteristic relaxation time constant of molecular chain segments Achieve energy coupling and according to a preset frequency With characteristic relaxation time constant The ratio determines the mixed correlation coefficient. The quantitative value; the mixed correlation coefficient measured during the calibration process. for This value is stored in the parameter matrix of the controller and is used to calibrate the spatial distribution of carbon dioxide nucleation rate in subsequent processing.

[0046] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A foaming process for low-carbon carbon dioxide-based polyether polyol sponge, characterized in that, Includes the following steps: Step S1: Establish a material conveying path so that the carbon dioxide-based polyether polyol can... MPa to Constant pressure cycling is performed at a first preset pressure of MPa; Step S2: Open the mixing channel and introduce carbon dioxide-based polyether polyol into the mixing chamber; Step S3, after the introduction of carbon dioxide-based polyether polyol ms to Within a preset delay time of ms, isocyanate components are injected into the mixing chamber; wherein, the isocyanate components are in the form of... Hz to A pulse is injected at a preset frequency of Hz to generate a transient pressure gradient in the mixing chamber for material mixing; Step S4: Guide the mixture to the outlet and perform a two-stage stepped pressure unloading to induce controlled nucleation of carbon dioxide; the two-stage stepped pressure unloading includes a first stage of depressurization to an intermediate equilibrium pressure and a second stage of depressurization to atmospheric pressure; Step S5: In the second-stage step pressure unloading stage, the pulse injection drive signal of the isocyanate component is acquired in real time, and the falling edge of the pulse injection drive signal is used as the reference phase reference. Step S6: Control the dynamic back pressure throttle valve at the discharge port after the reference phase reference. An unloading action is performed at the bias phase, causing an amplitude of [value missing] to be generated in the mixing chamber during the gap when the isocyanate component stops being injected. MPa to The transient pressure drop wave of MPa induces the material in the mixing chamber, which is under compression, to undergo forced elastic displacement towards the discharge port. Before the next pulse injection of the isocyanate component, the material flow field in the mixing chamber is restored to the static initial state.

2. The foaming process for a low-carbon carbon dioxide-based polyether polyol sponge according to claim 1, characterized in that, The intermediate equilibrium pressure in the two-stage stepped pressure unloading is set to the mixed chamber pressure. to During the second stage of depressurization to atmospheric pressure, a lubricating fluid is introduced circumferentially into the inner wall of the discharge port, forming an envelope slip layer around the material flow. The lubricating fluid has a flow rate lower than the total flow rate of the carbon dioxide-based polyether polyol. Carbon dioxide-based polyether polyols without nucleation auxiliary gases; by reducing the velocity gradient difference between the central fluid and the wall surface through the enveloping slip layer, the radial force environment of the carbon dioxide nucleation points tends to be symmetrical.

3. The foaming process for a low-carbon carbon dioxide-based polyether polyol sponge according to claim 1, characterized in that, The pulse injection stage in step S3 also includes: real-time monitoring of the pressure drop per unit length of the carbon dioxide-based polyether polyol in the material conveying path, and defining it as a flow characterization parameter. Establish flow regime characterization parameters The inverse mapping rule with the pulse on-width of the isocyanate component; when the flow characterization parameters When the pulse width decreases, the pulse opening width of the isocyanate component is automatically reduced according to the reverse mapping rule to compensate for the shear energy overflow caused by the decrease in material viscosity.

4. The foaming process for a low-carbon carbon dioxide-based polyether polyol sponge according to claim 1, characterized in that, The transient pressure drop wave in step S6 is achieved by adjusting the rising edge slope of the dynamic back pressure throttle valve; the rising edge slope generates a coherent pressure field at the outlet to offset the normal stress difference of the material, thereby reducing the elastic recovery of the material stream when it leaves the mixing chamber.

5. The foaming process for a low-carbon carbon dioxide-based polyether polyol sponge according to claim 1, characterized in that, The pressure reflection residual wave generated by the pulse injection of the isocyanate component induces periodic shear disturbance on the inner wall of the mixing chamber. By adjusting the feeding pressure waveform of the carbon dioxide-based polyether polyol, pressure fluctuations are generated at the end of each pulse cycle, and the pressure fluctuations and pressure reflection residual waves are superimposed in amplitude in the boundary layer region of the inner wall to peel off the material retention layer on the inner wall.

6. The foaming process for a low-carbon carbon dioxide-based polyether polyol sponge according to claim 1, characterized in that, Preset frequency in pulse injection step Characteristic relaxation time constants of molecular chain segments with carbon dioxide-based polyether polyols at mixing temperatures The logical resonance constraint is satisfied, and the logical resonance constraint satisfies the following formula: ,in, The preset hybrid correlation coefficient, and The range of values ​​is to The accumulation of elastic stress when the material stream leaves the outlet is reduced by using logical resonance constraints.

7. The foaming process for a low-carbon carbon dioxide-based polyether polyol sponge according to claim 1, characterized in that, Before each pulse injection cycle of the isocyanate component begins, the following steps are also included: applying a pulse value of a first preset pressure. to The leader micro-perturbation signal is captured; the echo energy distribution characteristics generated by the leader micro-perturbation signal in the mixing chamber are captured, and the attenuation coefficient of the echo envelope is calculated; the pulse opening width is corrected according to the attenuation coefficient to compensate for the nucleation stability drift caused by the fluctuation of carbon dioxide pre-dissolution state.

8. The foaming process for a low-carbon carbon dioxide-based polyether polyol sponge according to claim 1, characterized in that, At the instant the pulse injection of the isocyanate component stops, the pressure relief circuit connected to the mixing chamber is simultaneously activated; the pressure relief circuit guides the pressure reflection standing wave energy in the mixing chamber to the material conveying path.

9. The foaming process for a low-carbon carbon dioxide-based polyether polyol sponge according to claim 1, characterized in that, Pulse injection is achieved by controlling the duty cycle of the solenoid valve in the isocyanate component channel; the residence time at the intermediate equilibrium pressure is not less than [amount missing]. s.

10. The foaming process for a low-carbon carbon dioxide-based polyether polyol sponge according to claim 1, characterized in that, In step S1, the circulation speed of the material conveying path is adjusted by a variable frequency pump so that the Reynolds number of the carbon dioxide-based polyether polyol is at a certain level before entering the mixing chamber. to Within the range.

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