A method and apparatus for preparing a waterborne polyurethane pre-impregnated decorative paper

Abstract

The application provides a preparation method and device of water-based polyurethane pre-impregnated decorative paper. The method comprises obtaining a base paper and injecting recycled thermal energy to physically dehumidify the base paper to obtain a heat-dried base paper; in an alternating acoustic cavitation field, a transient positive pressure and a microjet are used to forcibly inject a water-based polyurethane dispersion liquid into a fiber pore to obtain an over-saturated wet paper web; an electromagnetic wave is injected into a negative pressure space to excite water molecules to flash boiling with micro-bubbles as crystal nuclei and generate water vapor; the water vapor is extracted to in-situ cure the resin, and the latent heat of phase change of the water vapor is extracted by a phase change heat pump to improve the quality into a high-temperature heat flow medium, which is distributed to the step of obtaining the base paper as the recycled heat energy. The application decouples the inherent contradiction between water as a transport carrier and as a swelling damage agent, overlaps the water phase infiltration and the gasification time, and realizes the deep in-situ curing of the macromolecular resin while avoiding the fiber swelling.

Description

Technical Field

[0001] This application relates to the field of papermaking and polymer material surface treatment technology, and more specifically, to a method and apparatus for preparing waterborne polyurethane prepreg decorative paper. Background Technology

[0002] In the manufacturing of decorative laminates and engineered wood panels, polyurethane resins are used as paper-based impregnation materials due to their abrasion resistance, flexibility, and physicochemical stability. With restrictions on volatile organic compound emissions, waterborne polyurethane systems using water as the continuous phase dispersion medium are widely applied. However, deep impregnation of waterborne resin systems in porous fiber substrates faces a fundamental and intractable technical contradiction: water molecules are both the necessary flow carrier for transporting polymeric resins into capillary pores and a destructive medium that breaks the hydrogen bonds between cellulose molecules, inducing irreversible swelling and wrinkling of the paper web.

[0003] Existing technologies extend the physical length of the impregnation tank and lengthen the conduction distance of the hot air oven to increase the penetration depth of the aqueous system within a thick paper base. This method results in the aqueous phase remaining within the fiber ducts for tens of seconds, exceeding the swelling and relaxation time of natural cellulose. This causes extreme instability in the paper web before drying, leading to paper breaks. Simultaneously, traditional hot air drying follows a surface-to-inside temperature gradient heat transfer mechanism, forming a moisture-sealing film on the paper web surface, hindering the escape of internal free water and limiting the compatibility boundary between high-solids-content aqueous impregnation and paper morphological stability. This technological bias has long hampered the continuous low-heat-consumption production of high-quality waterborne polyurethane prepreg decorative paper on high-speed roll-to-roll production lines. Summary of the Invention

[0004] In a first aspect, this application provides a method for preparing waterborne polyurethane prepreg decorative paper. The method includes obtaining base paper and injecting recovered heat energy into the base paper to evaporate the background moisture inside the base paper, generating a heat-dried base paper; in an alternating acoustic cavitation field, using transient mechanical positive pressure and bubble collapse microjets, forcibly injecting an aqueous polyurethane dispersion into the internal fiber pores of the heat-dried base paper to generate a wet paper web in a supersaturated state, wherein the interior of the supersaturated wet paper web contains cavitation microbubbles generated by the alternating acoustic cavitation field; transporting the supersaturated wet paper web to a sealed space with a set absolute negative pressure, and then... Orthogonally polarized electromagnetic waves are injected to excite water molecules inside the supersaturated wet paper web to undergo flash boiling using cavitation microbubbles as nuclei, generating water vapor. The water vapor is then extracted from the sealed space, causing the polymer macromolecules in the waterborne polyurethane dispersion to dehydrate and solidify in situ within the internal fiber pores, yielding waterborne polyurethane prepreg decorative paper. The latent heat of phase change contained in the water vapor is extracted using a reverse Carnot cycle phase change heat pump, and the latent heat of phase change is compressed, heated, and upgraded to generate a high-temperature heat flow medium with a preset high-grade total heat energy. This high-temperature heat flow medium is used as the recovered heat energy and routed to the steps of obtaining base paper and injecting the recovered heat energy into the base paper.

[0005] Secondly, this application provides an apparatus for preparing waterborne polyurethane prepreg decorative paper. The apparatus includes: a stiffness-adaptive tension-decoupling unwinding module configured to acquire base paper and inject recovered heat energy into the base paper to evaporate the background moisture inside the base paper, generating heat-dried base paper; an ultrasonic cavitation impregnation coupling engine, located downstream of the stiffness-adaptive tension-decoupling unwinding module, configured to forcibly inject waterborne polyurethane dispersion into the internal fiber pores of the heat-dried base paper in an alternating acoustic cavitation field using transient mechanical positive pressure and bubble collapse microjets, generating a wet paper web in a supersaturated state, wherein the wet paper web in the supersaturated state contains cavitation microbubbles generated by the alternating acoustic cavitation field; and a microwave negative pressure synergistic flash curing module, located downstream of the ultrasonic cavitation impregnation coupling engine, configured to forcibly inject waterborne polyurethane dispersion into the internal fiber pores of the heat-dried base paper in an alternating acoustic cavitation field ... generating a wet paper web in a super The wet paper web is conveyed into a sealed space with a set absolute negative pressure, and orthogonally polarized electromagnetic waves are injected into the supersaturated wet paper web to excite water molecules inside the supersaturated wet paper web to undergo flash boiling with cavitation microbubbles as crystal nuclei, generating water vapor. The latent heat feedback and rheological stabilization module is configured to extract the water vapor from the sealed space, so that the polymer macromolecules in the waterborne polyurethane dispersion are dehydrated and solidified in situ in the internal fiber pores to obtain waterborne polyurethane prepreg decorative paper. The latent heat feedback and rheological stabilization module is also configured to use a reverse Carnot cycle phase change heat pump to extract the phase change latent heat contained in the water vapor, compress and heat the phase change latent heat to generate a high-temperature heat flow medium, and distribute the high-temperature heat flow medium as the recovered heat energy route to the stiffness adaptive tension decoupling unwinding module.

[0006] This application has the following beneficial effects:

[0007] This application overcomes the technical limitations of existing technologies that extend the impregnation process in the spatiotemporal dimension by constructing an acoustic cavitation-microwave flash vapor-liquid phase change locking architecture. This application physically couples cavitation microbubbles generated by an alternating acoustic field into vaporization nuclei for subsequent electromagnetically heated flash evaporation. This allows free water molecules to undergo flash boiling and detach within a sub-second time window before fiber expansion, due to electromagnetic volumetric thermal excitation. The system utilizes a fluid phase change mechanism to in-situ lock the polyurethane macromolecular network within the fiber skeleton. Combined with a topological flow diagram that reverses the latent heat of phase change of the extracted vapor and feeds it back to the front end as the driving energy for dehumidifying the base paper, this application eliminates wrinkling and paper breakage defects while simultaneously improving overall energy utilization efficiency and achieving a closed-loop thermodynamic system. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0009] Figure 1 A schematic diagram of the overall architecture and internal principle structure of each core physical module of a waterborne polyurethane prepreg decorative paper preparation device provided in this application embodiment;

[0010] Figure 2 This is a schematic diagram of the control and preparation mechanism of a method for preparing waterborne polyurethane prepreg decorative paper provided in an embodiment of this application;

[0011] Figure 3 The graph showing the relationship between total microwave injection power and mass vaporization evaporation flow rate provided in the embodiments of this application (compares and shows the gain effect with and without cavitation nucleus coupling). Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0013] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0014] This embodiment provides a method and apparatus for preparing waterborne polyurethane prepreg decorative paper. In a specific implementation, this method employs a negative pressure flash evaporation mechanism under strong coupling of microwave and acoustic fields, and a closed-loop thermodynamic energy routing architecture. This allows for a high degree of overlap and compression of the physical wetting time and evaporation time of the aqueous carrier at the microscopic scale. This method solves the technical problems in the prior art, such as swelling and wrinkling of paper-based cellulose due to prolonged immersion in the aqueous system, and the surface pseudo-film formation and high energy consumption caused by the hot air conduction drying mechanism. It achieves the beneficial effects of increasing production line speed, ensuring deep anchoring of macromolecular resin within the pores, and closed-loop recovery of heat energy throughout the system.

[0015] In one specific embodiment, the apparatus for preparing waterborne polyurethane prepreg decorative paper according to this application consists of four physical modules.

[0016] The first module is a stiffness-adaptive tension-decoupled unwinding module. This module is configured to output constant tension and physically dehydrated base paper through a combination of mechanical and electronic control. The module's physical structure includes a double-cantilever air shaft fixed to a support base, an AC servo main drive motor directly connected to the air shaft, aluminum alloy surface guide idler rollers arranged along the paper path, and a set of floating damping rollers equipped with mechanical pressure adjusting springs. A 14-bit industrial-grade photoelectric absolute angular displacement encoder is coaxially mounted at the physical rotation center of the floating damping rollers to convert the mechanical deflection motion of the swing arms into absolute angular displacement digital messages. In the frame area immediately downstream of the floating damping roller, there is a stainless steel paper dehumidification and preheating cylinder roller with a built-in hollow fluid-conducting heat jacket. The shaft end of the stainless steel paper dehumidification and preheating cylinder roller is equipped with a dual-channel high-temperature resistant rotary joint, which connects to the high-temperature heat medium fluid from the subsequent module.

[0017] This module includes a high-frequency servo calculation subunit. This subunit runs as a firmware within a dedicated servo axis card of the programmable logic controller (PLC), and is configured to execute the optimal tension control law based on the spatial state feedback matrix, generating high-speed motion control messages.

[0018] This module maintains a persistent memory location of size [size missing] in the main controller's random access memory. A 2D double-precision floating-point array, named the base paper force state vector ( Vector).

[0019] For example, a specific base paper force state vector The entity's internal storage contains [248.5, 1.2, -1.5, 3.4], which correspond to instantaneous absolute tension, respectively. First derivative of tension time Target given deviation and servo motor output current reference The absolute angular displacement encoder communicates with the PLC via an RS485 serial differential bus; the servo drives synchronize torque based on the EtherCAT deterministic fieldbus.

[0020] The second module is the ultrasonic cavitation impregnation coupling engine. This module is located downstream of the stiffness-adaptive tension decoupling unwinding module and is configured to complete the penetration of polar macromolecular dispersions into a porous substrate. This module is presented as an electromechanical integrated impregnation tank deployed on a 316L type corrosion-resistant stainless steel frame. At the bottom of the impregnation tank, a total of 48 half-wavelength ultrasonic transducers made of PZT-8 piezoelectric ceramic material are rigidly bonded in a matrix with equal spacing using high-strength, weather-resistant epoxy resin adhesive. The outer wall of the impregnation tank is surrounded by a double-layer thermally conductive and insulating jacket structure that connects to a water-based heat exchange fluid, and an auxiliary electric heating device is provided on the jacket circuit. Two parallel cylindrical metal rolling structures are arranged on the upper part of the tank, forming an acoustic transmission impregnation roller for applying mechanical stress. This module includes a phased-array shock wave subunit and a acoustic luminescence cavitation detection unit. The phased-array shock wave subunit is configured to execute a multi-channel high-frequency PWM phase delay sequence algorithm. The acoustic cavitation detection unit includes an avalanche photodiode (APD) embedded in the outer side of a quartz glass window on the slot sidewall to capture and perform photon counting. The engine maintains a fixed-length 128-element acoustic impedance ring buffer in the embedded control layer. Exemplarily, an independent discrete element index within this buffer, as a data tuple containing electrical parameters of the driving circuit, can be specifically recorded as ( This continuously maps and quantifies the acoustic load matching state between the piezoelectric transducer array and the aqueous polyurethane dispersion. The array drive power supply is triggered by microsecond-cycle PWM square waves based on the field I / O module.

[0021] The third module is a microwave negative pressure synergistic flash curing module. This module is connected to the downstream outlet of the ultrasonic cavitation impregnation coupling engine and configured to perform liquid-gas phase change dehydration. This entity is a sealed impedance-matched aluminum alloy cavity. At both ends of the slot receiving the wet paper web, there are periodically arranged geometric choke structures. The top and side walls of the cavity are embedded with multi-mode microwave magnetron exciters connected to an industrial water cooling system. The bottom flange assembly is directly connected to a dual-rotor Roots pump system via a bellows. A wave-transparent transmission belt woven from polytetrafluoroethylene is arranged along the central axis of the cavity. This module includes a mode stirrer subunit. This subunit is a multi-bladed metal reflector driven by a stepper motor, which... The constant rotational speed is used to disturb the electromagnetic boundary conditions within the sealed cavity, reorganizing the three-dimensional distribution of standing wave nodes. The central microprocessor maintains a two-dimensional intracavity thermo-baric tensor for this cavity. (Tensor). For example, the morphological dimension of this tensor matrix is... The 10 rows represent 10 longitudinal physical coordinate slices along which the paper web moves, and the first column stores the absolute Celsius values ​​collected by the fiber optic infrared probe (e.g., ...). The second column stores the absolute pressure value read by the silicon piezoresistive vacuum gauge (e.g., ...). All microwave anode high-voltage power supplies are connected to the CAN field communication bus, and the AC frequency converter of the vacuum pumping Roots pump receives frequency commands via the Modbus RTU serial protocol.

[0022] The fourth module is the latent heat feedback and rheological stabilization module. This module is configured to achieve a closed-loop heat pump and energy distribution of the system through a reverse Carnot phase change cycle. The hardware sequence includes: a vertical scroll steam-water separator connected to the exhaust side of the impedance-matched aluminum alloy negative pressure chamber via piping, a stainless steel plate heat exchanger, a closed-loop heat pump compressor unit internally loaded with refrigerant, and an electronic proportional three-way diverter valve with a micro-stepping actuator arranged on the high-temperature side fluid output pipeline. This module includes a thermodynamic routing subunit. This subunit extracts latent heat from the steam based on the refrigeration phase change compression cycle, calculates the dynamic enthalpy requirement of the entire system, and executes a fuzzy PID control algorithm to drive the valve core displacement of the three-way diverter valve. The main controller maintains a thermal energy distribution state matrix. For example, this matrix records the heat power flow parameters of the current physical cycle. The electronic proportional three-way diverter valve is driven by a 4-20mA analog current signal received through a hard-wired digital-to-analog converter module.

[0023] The following section provides a hierarchical explanation of the system's control and preparation mechanisms, using specific methodologies and procedures as examples.

[0024] S000: Acquire parameters and perform rheological hard calibration.

[0025] Before the entire production line is put into operation, the system performs temperature limit calculations for the water-based polyurethane impregnation liquid.

[0026] The central controller reads the ambient temperature sensor readings and receives the target dynamic viscosity signal input by the user. For example, the target dynamic viscosity signal Can be set to .

[0027] The controller microprocessor unit invokes the rheological Arrhenius inverse algorithm module built into the underlying control library. This algorithm module executes the nonlinear mathematical equations with temperature scale transformation:

[0028]

[0029] The optimal constant immersion temperature can be obtained by solving the above equation. During the initial cold start transient phase of the system, the latent heat feedback loop has not yet established a stable enthalpy flow. At this time, the controller drives the auxiliary electric heating device to inject initial starting heat into the insulated electric heating tube inside the tank containing the aqueous polyurethane dispersion, and into the starting heating rod built into the dehumidification preheating cylinder roller used to obtain the base paper, until the actual fluid temperature of the aqueous polyurethane dispersion reaches the optimal constant impregnation temperature in Celsius. Once the system is running and the reverse Carnot cycle phase change heat pump generates the high-temperature heat flow medium, the central controller cuts off the solid-state relay enable signal of the auxiliary electric heating device and smoothly switches to closed-loop heating using the recovered heat energy distributed by the three-way diverter valve.

[0030] S100: Obtain base paper and inject recovered heat energy into the base paper to evaporate the background moisture inside the base paper, generating heat-dried base paper.

[0031] S110: Collect digital messages and map absolute mechanical deviations based on physical geometry.

[0032] The aforementioned high-frequency absolute angular displacement encoder sends digital absolute angular displacement messages reflecting the current position of the swing arm to the central processing core via an RS485 interface at a polling rate of 2000 Hz. The controller's message parsing process performs Gray code decoding and floating-point conversion on the digital sequence to obtain continuous physical absolute angular displacement values. (The unit is converted to standard radians) Simultaneously, acquire the target total tension scalar confirmed in the previous control cycle. (unit: The controller's floating-point unit executes the following geometric and mechanical operator functions, which are based on the equipment's mechanical assembly configuration:

[0033]

[0034] Through this calculation, the swing arm deflection angle is converted into an absolute mechanical deviation value that reflects the current forced tensile tension of the base paper.

[0035] S120: Perform state-space dynamics feedback matrix operations and electromagnetic torque compensation.

[0036] The processing unit calculates the instantaneous absolute tension deviation obtained from S110. Its time first derivative Combined into one Second-order dynamical state tensor of dimension Subsequently, the tensor is input into the linear quadratic regulator (LQR) matrix equation running within the chip. The optimal state feedback solution is then performed. In this solution process, the system optimizes the feedback gain matrix using the algebraic Riccati equation. And calculate the vector This control vector Directly mapped to the electromagnetic compensation torque required to drive the unwinding servo motor. Finally, the underlying communication layer encapsulates the floating-point torque value into a data frame and sends it to the servo drive register.

[0037] S130: Inject routed heat flow and perform fiber pore dehumidification and drying.

[0038] The base paper web, under constant tension conveying, passes through a stainless steel base paper dehumidification and preheating cylinder roll. A high-temperature heat transfer medium (containing the recovered heat energy) pumped from the subsequent latent heat feedback and rheological stabilization module circulates within the fluid jacket of the cylinder roll. Through a heat conduction mechanism, the base paper body is heated to the target dehumidification temperature (e.g., ...). The base paper's inherent equilibrium moisture evaporates, and the air in the pore network expands and is expelled due to heat. After this process, the roll material has a large number of emptied pores in its microstructure, resulting in a heat-dried base paper with a slightly negative pressure hydrophobic pore state.

[0039] S200: In an alternating acoustic cavitation field, a water-based polyurethane dispersion is forcibly injected into the internal fiber pores of the thermally dried base paper using transient mechanical positive pressure and bubble collapse microjets to generate a wet paper web in an oversaturated state.

[0040] S210: Drives the piezoelectric transducer array to excite an alternating wandering field of antinodes.

[0041] The main control board of the sound field generator generates a nominal 28 kHz fundamental radio frequency square wave sequence and injects a center frequency onto this high-frequency carrier. A low-frequency alternating bias signal is applied. An amplification architecture amplifies the bias signal and applies it to an array of 48 piezoelectric transducers on the bottom surface of the impregnation tank. Driven, the array base plate mechanically oscillates, exciting an alternating acoustic cavitation field within the fluid. Due to the superimposed low-frequency bias, the high-pressure antinodes of the standing wave field exhibit a periodic wandering effect in space. Cavitation microbubbles are excited and generated within the fluid.

[0042] S220: Inducing micro-jet cell disruption and permeation in the calendering jaw region.

[0043] The heat-dried base paper, guided by the traction flow, sinks to the bottom of the tank and, while submerged, enters the calendering jaws formed by cylindrical pressure rolls. Due to cross-sectional contraction, the hydrodynamic pressure rises sharply, applying a transient mechanical positive pressure (e.g., 2.5 MPa). Under this high-pressure stress, a large number of ultrasonic cavitation microbubbles entrained by the fluid become unstable and collapse. The bursting of the bubbles releases fluid microjet streams. These microjet streams break down the stagnant boundary layer surrounding the fibers. A large number of aqueous suspended polyurethane macromolecules and uncollapsed microbubbles are forced into the internal capillary network under the combined drive of the positive pressure and the jet streams. The macroscopic paper web output is a supersaturated wet paper web containing cavitation microbubbles.

[0044] S300: The wet paper web in the supersaturated state is transported to a sealed space with a set absolute negative pressure, and orthogonally polarized electromagnetic waves are injected into the wet paper web in the supersaturated state to excite the internal water molecules to undergo flash boiling with cavitation microbubbles as crystal nuclei.

[0045] S310: The suction establishes and maintains a thermodynamic absolute negative pressure step.

[0046] The Roots vacuum pump unit removes gas molecules from the top of the impedance-matched aluminum alloy negative pressure chamber, dynamically maintaining the absolute pressure value inside the chamber at a constant value. An absolute negative pressure plateau is established. Following the Clausius-Clapeyron equation, the boiling point of liquid water is lowered to approximately [value missing]. .

[0047] S320: Collects physical quantities and injects orthogonally polarized electromagnetic waves to excite internal heat.

[0048] The avalanche photodiode continuously captures the photon surge sequence emitted by the microjets and extracts the cavitation nucleus number density. and statistical average bubble radius The controller retrieves the first-principles evaporation kinetic model equations and, based on the formula... and Perform the calculation. During the calculation, substitute the currently set target mass vaporization evaporation flow rate. Acoustic microscale thermal boundary layer thickness Latent heat of vaporization constant and effective dielectric loss factor The total target microwave injection power was obtained through calculation. .

[0049] Subsequently, the control bus sends the calculated data to the dual-frequency microwave magnetron array. Equal power synchronous commands are given. A 2.45 GHz microwave beam with spatial orthogonal polarization is projected into the cavity by a magnetron array. The electromagnetic waves penetrate the entire volume of the wet paper web, which is in a state of oversaturation. Polar water molecule dipoles undergo in-situ reversal and friction at the same frequency. A mode stirring impeller installed in the cavity rotates at a constant speed driven by a stepper motor, reconstructing the interference distribution pattern of the internal standing waves, thereby achieving a uniform distribution of the electromagnetic heating volumetric energy density injected into the cross-section of the paper web.

[0050] S330: Induces cavitation nuclei flash boiling physical exfoliation and polymer network solidification.

[0051] The ultrasonic cavitation microbubbles left inside the fibers act as physical nucleation sites for the evaporative phase transition. When the internal heat causes the local water temperature to approach the boiling point, the liquid water system, originally under microwave heating, undergoes overall flash boiling, with the microbubbles as nuclei. The liquid water rapidly vaporizes and expands... Under the suction of the external negative pressure field, a large amount of water vapor generated by boiling forms a high-speed two-phase flow along the pore channels of the base paper and overflows out of the cavity.

[0052] During the instantaneous stripping of the aqueous phase, the polar polyurethane macromolecules, due to their massive mass, cannot escape with the steam and are forced to crosslink, dehydrate, and adhere to the fiber walls within the internal fiber lumen, solidifying into a continuous resin film. Because the time from the aqueous phase's intrusion to its phase transition is drastically shortened and forcibly ended before the macromolecular resin solidifies, the cellulose hydrophilic groups do not have sufficient time to accumulate and initiate hydrogen bond swelling. The system outputs high-quality waterborne polyurethane prepreg decorative paper with a resin-free surface and internal penetration.

[0053] S400: The water vapor is extracted from the sealed space, causing the polymer macromolecules in the aqueous polyurethane dispersion to dehydrate and solidify in situ within the internal fiber pores; the latent heat of phase change is extracted and upgraded into a high-temperature heat flow medium, which is then routed and distributed.

[0054] S410: Extracts the gaseous enthalpy flow and performs a phase change and quality improvement process using a compressor.

[0055] The discharged high-temperature, high-humidity water vapor stream, containing the phase change potential of water molecules, is introduced into a vortex-type vapor-water separator in the subsequent system to remove free droplets, and then flows into the hot-side channel of a stainless steel plate heat exchanger. The system starts the heat pump compressor unit. The refrigerant fluid efficiently absorbs the latent heat of vaporization released by the condensation of the aforementioned water vapor through physical evaporation phase change on the cold side of the heat exchanger. The refrigerant gaseous state, having absorbed low-grade enthalpy, is heated and pressurized after being compressed, generating a total amount of high-grade heat energy with a preset value. High-temperature heat transfer medium.

[0056] S420: Cross-level thermal energy closed-loop routing allocation based on energy conservation.

[0057] The central processing unit receives multiple power requests from system nodes, including preheating power requests to raise the temperature of low-temperature, moist base paper, impregnation temperature maintenance power requests to maintain a constant liquid temperature, and excess discharge requests to handle redundant heat generation.

[0058] The processor outputs a drive potential to a high-frequency stepper actuator, which rotates the electronic proportional three-way diverter valve. Based on the preheating power demand command, the valve opening is controlled, routing the first portion of the high-temperature heat flux to the preheating and dehumidifying cylinder roller at the unwinding end as recovered heat energy. Based on the impregnation temperature control power demand command, a small bypass channel is adjusted, routing the second portion of the high-temperature heat flux to the insulation jacket of the impregnation tank. Finally, based on the residual discharge command, the unloading channel is controlled to guide the remaining idle high-temperature heat flux to the waste discharge pipeline system. This step achieves a cross-stage thermal closed loop.

[0059] It should be noted that the inherent undamped angular frequency of the second-order model of the system is defined as follows: The formula contains the equivalent Young's modulus. Units are Cross-sectional area Units are winding radius and span Units are Moment of inertia Units are Its internal dimensions are deduced as follows: The dimensionless damping ratio is defined as... Feedback matrix operator Control input operator Substituting into the LQR algebraic Riccati equation ,in Preset as a diagonal matrix , Scalar preset Control input Output the calculated servo compensation torque (unit ).

[0060] Inverse calculation of the Arrhenius constant. Activation energy. ( ) and frequency front factor ( The following results were obtained using a coaxial cylindrical rotational viscometer: to Dynamic viscosity was obtained at 5 temperature points. Data. With For the ordinate, ( Plot a scatter plot on the x-axis and perform log-linear regression. Extract the slope scalar and multiply it by the ideal gas constant. Get Take a straight line. The natural index is derived from the axial intercept. .

[0061] To illustrate the closed-loop calculations of multiphysics thermodynamics, a first quantitative example is proposed:

[0062] For example, the unwinding module releases the width Quantitative thickness Base paper. Linear speed setting. ( The rate at which the oven-dry paper substrate passes through remains constant is... Total target tension Constant as .

[0063] System back calculation Locked in The polyurethane solids content in the M200 tank is 35%. The water content of the wet paper web at the liquid surface is approximately... That is, carrying per second Moisture content. The process requires the finished paper surface moisture content to be below [a certain level]. Therefore, the M300 needs to remove no less than [amount missing] per second. Free water.

[0064] M300 Inner Lumen Maintenance Negative pressure. Latent heat of vaporization of water. .support ( The minimum pure evaporation endothermic power required for liquid boiling is (Right now ).

[0065] The controller drives the magnetron to output total microwave power. Set the effective dielectric loss factor. The system converts to an effective internal heating power that does work on water molecules. .because To meet the heat absorption threshold, and in conjunction with the acoustic thermal boundary layer parameters Constructed nucleation gain amplification effect Within the dwelling space (approximately The liquid phase initiates flash boiling. The residual moisture content of the finished paper after desorption is... .

[0066] Gundam Phase change steam is introduced into the M400 condenser for condensation and upgrading to generate high-grade heat energy. The three-way tiered valve will supply the main branch. The preheating cylinder rollers of the M100 unwinding base are pumped into the pipeline, and... Paper web heated from room temperature to (This process consumes approximately...) Forced vaporization of the paper inside The latent heat consumed by the background equilibrium water is approximately (The margin is matched with natural convection and radiation dissipation). At the same time, a side stream branch is allocated. The reinjection tank jacket counteracts natural temperature drop to maintain End-of-life waste Discharge is connected to the plant's cooling water tower.

[0067] Preset second quantitative example (for thicker materials and parameter adjustment adaptability):

[0068] For example, the base paper is replaced with a basis weight thickness. The linear velocity decreased to ( At this time, the dry paper passes through at the same rate. Due to the Young's modulus of the base paper Increase, by acquiring and parsing the encoder's absolute angular displacement message through S100. The fluctuation amplitude decreases within the LQR system. The algorithm re-iterates the matrix within a two-millisecond control period. Guide out smaller Precisely stabilize the tension at the reset setting. Under this operating condition, the thermodynamic energy budget parameter matrix is ​​recalculated according to the aforementioned formula and an autonomous following closed loop is executed.

[0069] Preset counterexample interference events:

[0070] For example, a phase separation occurred when a non-polar silicone oil defoamer was inadvertently introduced into the M200 impregnation tank. The physical mapping value within the acoustic impedance annular buffer changed abruptly. From normal Sudden drop Phase angle represents the value from Plunging to Controlling the underlying layer Upon confirming that the physical impedance has exceeded the limit, an interlocking control command is immediately generated to disconnect the contactor of the M300 magnetron drive power supply master controller. This completely eliminates the potential for industrial fires caused by venting rated microwave energy onto a dry fiber network that has lost its moisture protection.

[0071] Known technical limitations and engineering solutions: Long-term, fixed-point focusing of local extreme energy in a high-frequency sound field carries a physical probability of severing long polymer chains. The system incorporates a forced 10 Hz frequency offset "standing wave field phase walk" component. This forces the antinodes to drift periodically, preventing sustained millisecond-level high-energy ultrasonic cavitation in the local physical space where the polymer resides, thus physically interrupting the material's mechanical degradation process on a temporal scale.

[0072] Performance verification standards and testing methods: Environmental calibration is performed at temperature. ,humidity A continuous phase change cured sample discharged from S400 was subjected to liquid nitrogen brittle fracture testing. The sample was then observed under 2000x magnification using a scanning electron microscope (SEM) to assess resin anchoring. A satisfactory result was characterized by the internal fiber cavities being fully filled with resin and the apparent polymer coating having a thickness of [insert thickness here]. Physical tensile testing was conducted according to ISO 3781 standard, using wide-width specimens that were immersed in water for 24 hours for wet tensile strength testing. The test data confirmed that the wet tensile strength retention rate of the waterborne polyurethane prepreg decorative paper after flash boiling curing exceeded that of the original paper base. .

[0073] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit described above can be implemented in hardware.

[0074] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing waterborne polyurethane prepreg decorative paper, characterized in that, The method includes: A base paper is obtained and recycled heat energy is injected into the base paper to evaporate the background moisture inside the base paper, thereby generating a heat-dried base paper; In an alternating acoustic cavitation field, a water-based polyurethane dispersion is forcibly injected into the internal fiber pores of the thermally dried base paper using transient mechanical positive pressure and bubble collapse microjets, generating a wet paper web in an oversaturated state. The wet paper web in the oversaturated state contains cavitation microbubbles generated by the alternating acoustic cavitation field. The oversaturated wet paper web is transported to a sealed space with a set absolute negative pressure, and orthogonally polarized electromagnetic waves are injected into the oversaturated wet paper web to excite the water molecules inside the oversaturated wet paper web to undergo flash boiling with the cavitation microbubbles as crystal nuclei, generating water vapor. The water vapor is extracted from the sealed space, causing the polymer macromolecules in the water-based polyurethane dispersion to dehydrate and solidify in situ within the internal fiber pores, thereby obtaining water-based polyurethane prepreg decorative paper. The latent heat of phase change contained in the water vapor is extracted by a reverse Carnot cycle phase change heat pump, and the latent heat of phase change is compressed, heated and upgraded to generate a high-temperature heat flow medium with a preset high-grade total heat energy. The high-temperature heat flow medium is used as the recovered heat energy, which is routed and distributed to the steps of obtaining the base paper and injecting the recovered heat energy into the base paper.

2. The method according to claim 1, characterized in that, Prior to the steps of obtaining the base paper and injecting recovered heat energy into the base paper, the method further includes: Collect ambient absolute temperature signals and user-input target dynamic viscosity signals; Based on the rheological Arrhenius equation, the target dynamic viscosity signal, the viscous flow activation energy of the waterborne polyurethane resin, and the frequency front factor, an exponential back-calculation logic with temperature scale conversion is executed to obtain the optimal constant impregnation temperature in Celsius for maintaining the constant rheological state of the waterborne polyurethane dispersion. During the transient phase of the initial cold start of the system, the auxiliary electric heating device is driven to inject initial starting heat into the tank containing the aqueous polyurethane dispersion and the dehumidifying preheating cylinder roller used to obtain the base paper, until the actual fluid temperature of the aqueous polyurethane dispersion reaches the optimal constant impregnation temperature in Celsius; after the reverse Carnot cycle phase change heat pump generates the high-temperature heat flow medium, the auxiliary electric heating device is cut off and the system is smoothly switched to use the recovered heat energy for heating.

3. The method according to claim 1, characterized in that, The steps of obtaining the base paper and injecting recovered heat energy into the base paper include: The absolute angular displacement digital message of the floating damping roller is acquired by an absolute angular displacement encoder, and the absolute angular displacement digital message is decoded and converted into a floating point number to obtain the physical absolute angular displacement value. Based on the physical absolute angular displacement value, spring stiffness coefficient, swing arm physical length, and target total tension scalar, perform geometric mechanical operator mapping to obtain the instantaneous absolute tension deviation; Based on the instantaneous absolute tension deviation and the time first derivative of the instantaneous absolute tension deviation, a second-order dynamic state tensor is constructed, and the second-order dynamic state tensor is input into the linear quadratic regulator matrix equation for optimal state feedback solution to obtain the electromagnetic compensation torque used to drive the unwinding servo motor. The high-temperature heat flow medium containing the recovered heat energy is introduced into the internal fluid jacket of the dehumidification preheating cylinder roller to heat the base paper covering the surface of the dehumidification preheating cylinder roller to the target dehumidification temperature.

4. The method according to claim 1, characterized in that, The step of forcibly injecting an aqueous polyurethane dispersion into the internal fiber pores of the thermally dried base paper using transient mechanical positive pressure and bubble collapse microjets in an alternating acoustic cavitation field includes: Generate a basic radio frequency square wave sequence, and superimpose a low-frequency alternating bias signal onto the basic radio frequency square wave sequence; The basic radio frequency square wave sequence superimposed with the low-frequency alternating bias signal is amplified and applied to the bottom-mounted piezoelectric transducer array to excite the alternating acoustic cavitation field in the aqueous polyurethane dispersion, in which the high-voltage antinodes of the standing wave periodically move in space. The heat-dried base paper is guided through the calendering jaw area of ​​the acoustic transmission impregnation roll to apply the transient mechanical positive pressure.

5. The method according to claim 1, characterized in that, The step of using the high-temperature heat transfer medium as the recovered heat energy, routing and allocating it to the acquisition of base paper and injecting the recovered heat energy into the base paper, includes: Obtain preheating power demand instructions, impregnation temperature control power demand instructions, and margin discharge instructions; The electronic proportional three-way diverter valve is driven to route the first part of the high-temperature heat flow medium to the preheating and dehumidifying cylinder roller at the unwinding end as the recovered heat energy according to the preheating power demand command. According to the impregnation and temperature maintenance power demand command, the second part of the high-temperature heat flow medium is routed to the insulation jacket of the impregnation tank. According to the residual discharge command, the remaining high-temperature heat flow medium is guided to the waste discharge pipeline.

6. The method according to claim 1, characterized in that, The step of injecting orthogonally polarized electromagnetic waves into the wet paper web in the oversaturated state includes: The cavitation nucleus number density and statistical average bubble radius, which characterize the intensity of the alternating acoustic cavitation field, are collected in real time using a photon avalanche counter. Based on the first-principles evaporation kinetics model, the cavitation nucleus number density, the statistical average bubble radius, the acoustic microscale thermal boundary layer thickness, the latent heat of vaporization of water vapor, and the effective dielectric loss factor, the target total microwave injection power required to satisfy the target mass vaporization evaporation flow rate is calculated. A power synchronization command equal to the total microwave injection power to the target is sent to the dual-frequency magnetron array.

7. The method according to claim 1, characterized in that, The step of injecting orthogonally polarized electromagnetic waves into the wet paper web in the oversaturated state further includes: A multi-bladed metal reflective stirring wheel, driven by a stepper motor and installed inside the sealed space, rotates continuously at a preset speed, constantly changing the electromagnetic resonance boundary conditions within the sealed space and reorganizing the microwave standing wave nodes, so that the electromagnetic heating volumetric energy density injected into the cross-section of the wet paper web, which is in an oversaturated state, is uniformly distributed.

8. An apparatus for preparing waterborne polyurethane prepreg decorative paper, characterized in that, The device includes: The stiffness adaptive tension decoupling unwinding module is configured to acquire base paper and inject recovered heat energy into the base paper to evaporate the background moisture inside the base paper and generate thermally dried base paper. An ultrasonic cavitation impregnation coupling engine is located downstream of the stiffness adaptive tension decoupling unwinding module. It is configured to forcibly inject an aqueous polyurethane dispersion into the internal fiber pores of the thermally dried base paper in an alternating acoustic cavitation field using transient mechanical normal pressure and bubble collapse microjets, thereby generating a wet paper web in an oversaturated state. The wet paper web in the oversaturated state contains cavitation microbubbles generated by the alternating acoustic cavitation field. The microwave negative pressure synergistic flash evaporation and curing module is located downstream of the ultrasonic cavitation impregnation coupling engine. It is configured to transport the wet paper web in a supersaturated state to a closed space with a set absolute negative pressure, and inject orthogonally polarized electromagnetic waves into the wet paper web in a supersaturated state to excite the water molecules inside the wet paper web in a supersaturated state to undergo flash boiling with the cavitation microbubbles as crystal nuclei, generating water vapor. The latent heat feedback and rheological stabilization module is configured to extract the water vapor from the sealed space, causing the polymer macromolecules in the waterborne polyurethane dispersion to dehydrate and solidify in situ within the internal fiber pores, thereby obtaining waterborne polyurethane prepreg decorative paper. The latent heat feedback and rheological stabilization module is further configured to extract the latent heat of phase change contained in the water vapor using a reverse Carnot cycle phase change heat pump, and to compress, heat up, and improve the latent heat of phase change to generate a high-temperature heat flow medium, and to distribute the high-temperature heat flow medium as the route for the recovered heat energy to the stiffness adaptive tension decoupling unwinding module.

9. The apparatus according to claim 8, characterized in that, The stiffness adaptive tension decoupling unwinding module includes an air shaft, an AC servo main drive motor, a floating damping roller, a high-frequency absolute angular displacement encoder, and a stainless steel base paper dehumidification and preheating cylinder roller with a built-in fluid jacket. The stainless steel base paper dehumidification and preheating cylinder roller is connected to the latent heat feedback and rheological stabilization module through a dual-channel rotary joint.

10. The apparatus according to claim 8, characterized in that, The latent heat feedback and rheological stabilization module includes a vortex steam-water separator connected to the exhaust port of the microwave negative pressure synergistic flash curing module, a stainless steel plate heat exchanger, a reverse Carnot heat pump compressor unit loaded with refrigerant, and an electronic proportional three-way diverter valve with a micro-stepping drive actuator. The output end of the electronic proportional three-way diverter valve is connected to the stainless steel base paper dehumidification preheating cylinder roller.

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