Preparation method of fireproof and moistureproof micro-foaming profile for building energy-saving thermal insulation material

Abstract

The invention discloses a preparation method of a fireproof and moistureproof micro-foaming profile for a building energy-saving thermal insulation material, and relates to the technical field of building materials. The method comprises the following steps: collecting surface energy data of a polymer base material, a flame retardant and a moisture-proof functional filler and solubility parameters of a physical foaming agent; establishing a three-phase interfacial tension balance model, and solving an optimal cladding layer polarity parameter and thickness; coating the surfaces of the flame retardant particles with a moisture-proof agent layer and an amphiphilic polymer bridging layer in sequence to prepare a modeling functional unit; after mixing and plasticizing with a polymer base material, injecting a supercritical physical foaming agent to form a composite melt; establishing a non-isothermal mathematical model, and generating a space gradient dynamic temperature control program of the extrusion die and the stock die; and finally carrying out extrusion molding through the procedure. The prepared profile has excellent fireproof and moistureproof performance and heat preservation and insulation effects, is stable in structure, high in durability and high in process controllability, is suitable for large-scale production, and meets the high-performance requirement in the field of building energy conservation.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and more specifically, to a method for preparing fireproof and moisture-proof micro-foamed profiles for building energy-saving insulation and heat insulation materials. Background Technology

[0002] In the field of building energy conservation, thermal insulation materials are one of the core components for reducing building energy consumption. Among them, micro-foamed profiles have become mainstream products due to their advantages such as lightweight, high-efficiency insulation, and low material consumption. In existing technologies, micro-foamed thermal insulation profiles for buildings are mostly made of polymers as the base material, and are prepared by adding flame retardants, moisture-proof functional fillers, and other components through processes such as mixing, melt plasticizing, foaming agent injection, and extrusion molding. The core idea is to achieve thermal insulation by utilizing the closed-cell structure of the polymer matrix, while the functional fillers endow the profiles with additional properties such as fire resistance and moisture resistance.

[0003] However, these existing preparation technologies still have significant shortcomings in practical applications: First, the surface energy difference between functional components such as flame retardants and moisture-proof fillers and polymer base materials is large, resulting in poor interfacial compatibility. This leads to the functional fillers easily agglomerating and unevenly dispersing in the base material, failing to fully exert their fireproof and moisture-proof effects and affecting the mechanical structural stability of the profile. Second, the lack of precise temperature field control during the foaming process makes it difficult to control the dissolution and diffusion behavior of physical foaming agents, resulting in uneven cell sizes and disordered distribution, directly reducing the thermal insulation efficiency of the profile. Third, traditional processes do not systematically optimize the interfacial interaction between functional fillers and base materials. After long-term service, the profiles are prone to problems such as functional coating peeling and cell collapse, leading to a decline in fireproof and moisture-proof performance and making it difficult to meet the long-term use requirements of building materials. Summary of the Invention

[0004] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a method for preparing fire-resistant and moisture-proof micro-foamed profiles for building energy-saving thermal insulation materials. The following solutions address the problems mentioned in the background art regarding uneven dispersion of functional fillers, poor interfacial compatibility, disordered cell structure, and reduced fire-resistant, moisture-proof, and thermal insulation performance of micro-foamed profiles for building insulation.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing fireproof and moisture-proof micro-foamed profiles for building energy-saving thermal insulation materials, comprising: S1: collecting surface energy data of polymer base material, flame retardant and moisture-proof functional filler, as well as solubility parameters of physical foaming agent;

[0006] S2: Establish a three-phase interfacial tension balance model, and calculate based on the surface energy data to obtain the polarity parameters and thickness of the coating material that minimizes the interfacial tension between the functional filler and the polymer melt.

[0007] S3: Based on the polarity parameters and thickness of the coating material, a moisture-proof layer and an amphiphilic polymer bridging layer with a specific glass transition temperature are sequentially coated on the surface of the flame retardant particles to obtain a modeled functional unit.

[0008] S4: The modeled functional unit is mixed and plasticized with the polymer base material, and a physical foaming agent is injected under supercritical conditions to form a uniform composite melt;

[0009] S5: Establish a non-isothermal mathematical model, solve it based on the solubility parameter of the physical foaming agent and the glass transition temperature of the amphiphilic polymer bridging layer, and obtain a dynamic temperature control program for generating a spatial gradient temperature field at the extrusion die and the shaping die.

[0010] S6: The composite melt is extruded and shaped through an extrusion die that executes the dynamic temperature control program.

[0011] The technical effects and advantages of this invention are as follows:

[0012] 1. This invention collects the surface energy and solubility parameters of key materials, establishes a three-phase interfacial tension balance model to optimize the polarity parameters and thickness of the coating layer, significantly reduces the interfacial tension between the functional filler and the polymer melt, effectively improves the problems of poor interfacial compatibility and uneven dispersion of functional components in traditional processes, enables the fireproof and moisture-proof components to play a full role, and improves the stability of the profile's functional performance.

[0013] 2. This invention establishes a non-isothermal mathematical model based on the solubility parameters of the physical foaming agent and the glass transition temperature of the amphiphilic polymer bridging layer, generates a spatial gradient dynamic temperature control program, realizes precise control of the foaming process, ensures uniform cell size and dense distribution, and effectively improves the core thermal insulation performance of the profile.

[0014] 3. This invention constructs a model functional unit by adopting a double-layer coating structure of "moisture-proof agent layer + amphiphilic polymer bridging layer", which synergistically leverages the functional characteristics of flame retardant and moisture-proof filler, enabling the profile to have excellent fire resistance and moisture resistance at the same time. Moreover, the coating is firmly bonded to the polymer base material, avoiding the problems of functional coating peeling and performance degradation during long-term service, and significantly improving the durability and service life of the profile. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall method steps of the present invention;

[0016] Figure 2 This is a schematic diagram of the process for obtaining the modeled functional units of the present invention;

[0017] Figure 3 This is a schematic diagram of the process for obtaining a uniform composite melt according to the present invention;

[0018] Figure 4 This is a schematic diagram of the process for obtaining the dynamic temperature control program according to the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] As attached Figure 1 The method for preparing fireproof and moisture-proof micro-foamed profiles for building energy-saving thermal insulation materials includes:

[0021] S1: Collect surface energy data of polymer base material, flame retardant and moisture-proof functional filler, as well as solubility parameters of physical foaming agent.

[0022] The surface energy data of polymer base materials, flame retardants, and moisture-proof fillers were collected, and the specific process is as follows:

[0023] Instrument and reagent preparation: A DSA100 contact angle meter with an accuracy of not less than 0.1 degrees was selected, equipped with a temperature-controlled sample stage, an automatic dispensing system, and an image analysis module. The temperature-controlled sample stage has a temperature range of room temperature to 300 degrees Celsius, and the automatic dispensing system has a dispensing accuracy of 0.1 μL. The standard test solutions are deionized water with a purity of not less than 99.9% and a surface energy of 72.8 mN / m, and high-purity diiodomethane with a purity of not less than 99.5% and a surface energy of 50.8 mN / m. Before testing, the solutions are filtered through a 0.22-micron organic phase filter membrane to remove impurities. Auxiliary equipment includes a vacuum drying oven, a tablet press, and a constant temperature heating device. The temperature control accuracy of the vacuum drying oven is ±1 degree Celsius, and the pressure of the tablet press is adjustable from 0 to 50 MPa with a pressure holding accuracy of ±0.1 MPa.

[0024] Polymer surface energy can be collected, taking polystyrene as an example:

[0025] Pretreatment: Place polystyrene granules in a vacuum drying oven and dry at 80 degrees Celsius for 4 hours to remove adsorbed moisture and impurities; prepare smooth sheets of 50 mm x 50 mm x 2 mm by injection molding, lightly sand the surface with 5000 grit sandpaper (to remove injection marks), wipe clean with anhydrous ethanol, and air dry at room temperature for later use; or wipe directly with anhydrous ethanol and then air dry (if there are no obvious defects on the surface).

[0026] Test conditions: Fix the thin sheet on the temperature-controlled sample stage of the contact angle measuring instrument, heat it to 240 degrees (the melting temperature of polystyrene), and keep it at that temperature for 30 minutes to stabilize the temperature and ensure that the polystyrene is in a molten state.

[0027] Contact angle measurement: The pendant drop method was used. 5 μL of deionized water and 5 μL of pure diiodomethane were slowly added to the surface of polystyrene melt. After the droplet shape stabilized, the profile was photographed after about 10 seconds. Each test liquid was measured 5 times at different positions, and the average value was taken as the final contact angle data.

[0028] Data Calculation: The surface energy and its components were calculated based on the Owens-Wendt equation, which is as follows: In the formula, γ represents the surface energy, the superscript d represents the dispersion component, the superscript p represents the polar component, the subscript S represents the sample, and the subscript L represents the test solution. Substituting the known surface energy and component data of the test solution, the total surface energy γ of polystyrene can be obtained by solving the simultaneous equations. PS polar components and dispersion component .

[0029] Flame retardant surface energy harvesting, taking expanded graphite as an example:

[0030] Pretreatment: Place the expanded graphite particles in a vacuum drying oven and dry at 80 degrees for 6 hours to remove pore moisture; take the dried expanded graphite particles and press them under 20 MPa pressure for 5 minutes to prepare dense and smooth sheets of 50 mm x 50 mm x 3 mm.

[0031] Test conditions: The temperature-controlled sample stage was kept at room temperature of 25 degrees Celsius. The expanded graphite sheet was fixed and left to stand for 10 minutes.

[0032] Contact angle measurement: The contact angles of deionized water, high-purity diiodomethane and expanded graphite sheets were measured using the above-mentioned pendant drop method. Each test solution was repeated 5 times and the average value was taken.

[0033] Data Calculation: Substituting the Owens-Wendt equation and simultaneously solving the contact angle data between deionized water and high-purity diiodomethane, the total surface energy of expanded graphite was obtained. polar components and dispersion component .

[0034] Moisture-proof filler surface energy can be collected, taking hydrophobic silica as an example:

[0035] Pretreatment: After the hydrophobic silica powder is vacuum dried at 80 degrees for 4 hours, it is pressed into a smooth sheet of 50 mm x 50 mm x 3 mm under a pressure of 25 MPa for 5 minutes.

[0036] Test conditions and procedures: Same as flame retardant collection procedure. The contact angle is measured using the pendant drop method at room temperature. Each test solution is repeated 5 times and the average value is taken.

[0037] Data calculation: The total surface energy γ of hydrophobic silica was obtained by solving the Owens-Wendt equation. SiO_2-H .

[0038] The solubility parameters of the physical foaming agent are collected, including the solubility coefficient and the diffusion coefficient. The specific process is as follows:

[0039] Instrument and material preparation: A high-pressure reactor with a volume of 500 mL, a pressure resistance of not less than 50 MPa, a temperature control accuracy of ±1 degree, and equipped with a pressure sensor and an online sampling device, with a pressure sensor accuracy of 0.01 MPa; a GC-TCD gas chromatograph with a detector sensitivity of not less than 1000 mV・mL / mg; food-grade carbon dioxide with a purity of not less than 99.99% as the physical foaming agent; the polymer base material is the same batch of polystyrene granules mentioned above; auxiliary equipment includes an electronic balance and a vacuum drying oven, with an electronic balance accuracy of 0.1 mg.

[0040] Pretreatment: Place the polystyrene particles in a vacuum drying oven and dry at 80 degrees for 4 hours. After cooling to room temperature, accurately weigh 5 grams and place them in a high-pressure reactor. Seal the reactor and evacuate to a vacuum degree of 0.095 MPa (absolute pressure of 0.005 MPa). Maintain this for 30 minutes to remove air from the reactor.

[0041] Test conditions were set as follows: The reactor was heated to 200 degrees Celsius. After the temperature stabilized, carbon dioxide was injected through a high-pressure pump. The pressure gradient was set to 5 MPa, 10 MPa, 15 MPa, 20 MPa, and 25 MPa. Each pressure point was kept at a constant temperature and pressure for 6 hours to ensure that the carbon dioxide reached a dissolution equilibrium in the polystyrene melt.

[0042] Solubility coefficient determination: After reaching equilibrium, slowly release the undissolved carbon dioxide from the reactor, quickly remove the polystyrene sample from the reactor, and immediately weigh the mass change Δm; through... ( The molar amount of dissolved carbon dioxide was calculated, and combined with the volume of polystyrene melt, the solubility coefficient S of carbon dioxide in polystyrene melt under different pressures was derived, with the unit being cm³(STP) / (cm³・MPa). The empirical correlation between S and pressure was obtained through linear fitting: S=k1P+b1, where k1 is the fitting slope, b1 is the intercept, and P is the pressure.

[0043] Diffusion coefficient determination: Under the above constant temperature and pressure conditions, a small amount of polystyrene melt sample was periodically extracted through the sampling port of the high-pressure reactor, and the concentration of carbon dioxide in the sample at different time points was determined by gas chromatography; the diffusion coefficient D of carbon dioxide in polystyrene melt was obtained by fitting the concentration-time curve according to Fick's second law, with the unit being cm² / s; the empirical correlation between D and pressure was established as: D = k²P + b², where k² is the fitting slope and b² is the intercept.

[0044] S2: Establish a three-phase interfacial tension balance model, and calculate based on the surface energy data to obtain the polarity parameters and thickness of the coating material that minimizes the interfacial tension between the functional filler and the polymer melt.

[0045] A three-phase interfacial tension equilibrium model was established and the calculation was completed. The specific process is as follows:

[0046] Model building preparation specifically includes:

[0047] The numerical computation software used was MATLAB 2023b, equipped with an optimization computation toolbox and a data visualization module.

[0048] Data preprocessing: Based on the total surface energy γ of polystyrene PS Polar components of polystyrene Polystyrene dispersion component Total surface energy of expanded graphite γ EG γ-Hydrophobic silica total surface energy SiO_2-H All surface energy data were validated, and outliers deviating from the average by more than 5% were removed. After validation, a standardized surface energy parameter matrix was formed and used as the model input data source.

[0049] The establishment of a three-phase interfacial tension balance model includes:

[0050] Model Assumptions: The functional filler system is assumed to involve a three-phase core system, namely, a polystyrene melt phase, an amphiphilic polymer bridging layer phase, and a hydrophobic silica-expanded graphite composite phase. The hydrophobic silica moisture barrier and the expanded graphite core are densely and stably bonded together through pretreatment processes such as vacuum drying and high-pressure pressing, merging into a single functional composite phase. Based on this three-phase system, three interfaces actually exist within the system: the interface between the polystyrene melt and the bridging layer, the interface between the bridging layer and the hydrophobic silica-expanded graphite composite phase, and the interface between expanded graphite and hydrophobic silica. Since the interface between expanded graphite and hydrophobic silica has already formed a stable bond through pretreatment, its interfacial tension has no room for adjustment within the optimization range of this model. Therefore, this model focuses on two key interfaces affecting the compatibility between the functional filler and the polymer melt: the first interface between the polystyrene melt and the bridging layer, and the second interface between the bridging layer and the hydrophobic silica-expanded graphite composite phase. The model ignores the influence of gravity and temperature gradient on the tension of these two key interfaces, focusing only on the regulatory effect of polarity parameters and thickness on interfacial tension.

[0051] Clarify the relationship between the surface energy components and polarity parameters of the bridging layer:

[0052] In the formula, χ is the polarity parameter of the bridging layer, a dimensionless parameter characterizing the polarity of the bridging layer, with a value ranging from 0 to 1; γ B The total surface energy of the bridging layer is expressed in mN / m. This represents the polarity component of the bridging layer, in mN / m.

[0053] In the formula, The value represents the dispersion component of the bridging layer, expressed in mN / m.

[0054] Based on the Owens-Wendt equation, the formulas for calculating the interfacial tension at the two interfaces are derived respectively:

[0055] The formula for calculating the interfacial tension γ1 at the first interface (polystyrene melt-bridging layer) is: In the formula, γ1 is the interfacial tension of the first interface, with the unit being mN / m;

[0056] The formula for calculating the interfacial tension γ2 of the second interface (bridging layer - hydrophobic silica moisture barrier layer) is: In the formula, γ2 is the interfacial tension of the second interface, with units of mN / m; The dispersion component is that of hydrophobic silica. For the hydrophobic silica polar component, both parameters are based on the industry-standard separation ratio of surface energy components in inorganic silicon-based fillers, with the dispersive component accounting for 90% and the polar component accounting for 10%. , .

[0057] The effective interfacial tension between the functional filler and the polymer melt is defined as the weighted sum of the two interfacial tensions, with the weighting coefficient determined by the bridging layer thickness. The effective interfacial tension γ eff The calculation formula is: In the formula, γ eff The effective interfacial tension is expressed in mN / m; δ is the bridging layer thickness parameter, expressed in nanometers; δ0 is the critical value of the bridging layer thickness, expressed in nanometers, and is set to 200 nanometers. This value is determined by the coating thickness limit of the fluidized bed coating process.

[0058] The objective function is defined as F(χ,δ), aiming to minimize the effective interfacial tension while considering process feasibility. Its expression is: F(χ,δ)=γ eff +α·|δ-δ m In the formula, F(χ,δ) is the objective function, which is dimensionless; α is the process constraint weighting coefficient, with units of mN / m·nm, and a value of 0.05mN / m·nm, used to balance the goal of minimizing interfacial tension with process feasibility; δ m The mean thickness is the optimal thickness for fluidized bed coating process, in nanometers, with a value of 100 nanometers, which is the optimal reference thickness for the process.

[0059] Model calculation and solution, specifically including:

[0060] Parameter initialization: Set the initial value of the polarity parameter χ to 0.5 and the step size to 0.01; set the initial value of the thickness parameter δ to 100 nm and the step size to 5 nm; set the convergence threshold ε to 0.001 mN / m.

[0061] Iterative calculation: The gradient descent method is used for iterative solution. The calculation steps are as follows:

[0062] Step 1: Substitute the initial χ and δ, and combine with γ B The conventional value (referring to the general surface energy range of amphiphilic polymer bridging layers, the value is taken as 35 mN / m) is calculated sequentially. , γ1, γ2, γ eff Finally, the initial objective function value F0 is obtained;

[0063] Step 2: Keep δ constant, adjust the step size along the positive and negative directions of χ, calculate the new objective function value, select the direction that reduces the objective function value and continue iterating until the change in the objective function value in the χ dimension is less than ε (ε is the convergence threshold used to determine whether the iterative calculation has terminated).

[0064] Step 3: Keep the optimized χ unchanged, adjust the step size along the positive and negative directions of δ, and repeat the above iterative process until the change in the objective function value in the δ dimension is less than ε;

[0065] Step 4: Simultaneously optimize χ and δ, repeating steps 2 and 3 until the objective function value no longer decreases;

[0066] Convergence Criterion: When the change in the objective function value is less than the convergence threshold ε for 10 consecutive iterations, the iteration is considered converged, and the optimal bridging layer polarity parameter χ is output. opt and the optimal bridging layer thickness δ opt .

[0067] S3: Based on the polarity parameters and thickness of the coating material, a moisture-proof layer and an amphiphilic polymer bridging layer with a specific glass transition temperature are sequentially coated on the surface of the flame retardant particles to obtain a modeled functional unit.

[0068] The following steps were performed sequentially: coating with a moisture-proof layer, coating with an amphiphilic polymer bridging layer, and validating the functional units.

[0069] Instrument and material preparation, specifically including:

[0070] Core instruments: A WBG-5 fluidized bed coating system with an effective fluidization chamber volume of 5L, equipped with dual-fluid atomizing nozzles, adjustable atomization pressure range of 0.1-0.5MPa, a precision feeding system with a feed rate accuracy of 0.1g / min, and a temperature-controlled heating mantle with a temperature control range of room temperature to 200 degrees Celsius and a temperature control accuracy of ±1 degree Celsius; auxiliary instruments include a SU8010 scanning electron microscope with a magnification of 5000-10000x, a coating thickness measuring instrument with an accuracy of 0.1 nanometers, and a DSC214 differential scanning calorimeter with a temperature control range of -50 to 300 degrees Celsius.

[0071] Materials preparation:

[0072] Flame retardant granules: Expanded graphite with a particle size range of 50-100 micrometers and a density of 2.1 g / cm³ is selected and vacuum dried at 80 degrees Celsius for 6 hours before use. The moisture content after drying is ≤0.5%.

[0073] Moisture-proofing agent: Hydrophobic silica with a particle size of 20-50 nanometers and a purity of not less than 99.8% is selected, and it is from the same batch of products as the hydrophobic silica used to collect surface energy data.

[0074] Amphiphilic polymer bridging layer material: based on the optimal polarity parameter χ opt Select the appropriate type of styrene-maleic anhydride copolymer, wherein the maleic anhydride monomer content is determined by χ. opt Confirmed, χ opt =0.3-0.5 corresponds to a maleic anhydride content of 10%-20%, and the glass transition temperature range of this copolymer is 80-100 degrees Celsius;

[0075] Solvent: Anhydrous ethanol with a purity of not less than 99.7% is selected as the dispersion medium for the moisture-proof agent and the bridging layer material.

[0076] The moisture-proof coating specifically includes:

[0077] Pretreatment: Add 50g of dried expanded graphite particles to the fluidization chamber of the fluidized bed coating equipment, turn on the preheating, set the fluidization chamber temperature to 60 degrees, introduce dry compressed air with a dew point ≤ -40 degrees, adjust the air flow rate to keep the expanded graphite particles in a stable fluidized state, fluidization air velocity 1.2-1.5m / s, preheat for 30 minutes to remove residual moisture.

[0078] Preparation of desiccant dispersion: Hydrophobic silica was added to anhydrous ethanol at a solid-liquid mass ratio of 1:15.8. The dispersion was prepared by using an ultrasonic disperser with a power of 200W and a frequency of 40kHz for 30 minutes. The concentration of the dispersion was controlled at 50g / L.

[0079] Coating operation: Turn on the dual-fluid atomizing nozzle and atomize the hydrophobic silica dispersion at a feed rate of 2 g / min, then spray it into the fluidization chamber. Set the atomization pressure to 0.2 MPa, maintain the fluidization chamber temperature at 60 degrees Celsius, and keep the fluidization air velocity stable. Calculate the coating time based on the required total mass of hydrophobic silica using the following formula: In the formula, The coating time of the moisture-proof agent layer (minutes); The total mass (grams) of the required hydrophobic silica. The mass fraction of hydrophobic silica in the dispersion (for a solid-liquid ratio of 1:15.8, the value is approximately 1 / 16.8 ≈ 5.95%). The mass fraction of hydrophobic silica in the dispersion is approximately 4.76% (1 / 21). The actual coating time should be calculated based on the actual time (usually 10-30 seconds).

[0080] Drying and curing: After coating, maintain the fluidized state, raise the temperature of the fluidization chamber to 80 degrees, and continue to dry with dry air for 40 minutes to allow the anhydrous ethanol to evaporate completely and the moisture-proof layer to cure and adhere to the surface of the expanded graphite.

[0081] Moisture-proof layer thickness control: The thickness of the moisture-proof layer is controlled by adjusting the total feed rate of the hydrophobic silica dispersion. The target thickness is set at 50 nanometers, and the specific calculation formula is as follows: In the formula, The required mass of hydrophobic silica, in grams; M EG The total mass of expanded graphite is expressed in grams (value taken as 50g); ρ EG The density of expanded graphite is expressed in g / cm³ (value 2.1 g / cm³). ρ is the density of hydrophobic silica, taken as 2.2 g / cm³; r is the average radius of expanded graphite particles, in centimeters; The target thickness of the moisture-proof layer is in centimeters.

[0082] The amphiphilic polymer bridging layer coating specifically includes:

[0083] Pretreatment: Leave the expanded graphite particles coated with the moisture-proof agent layer in the fluidization chamber, adjust the fluidization chamber temperature to 90 degrees, maintain the fluidization air velocity at 1.2-1.5 m / s, and preheat for 20 minutes;

[0084] Preparation of bridging layer dispersion: The selected styrene-maleic anhydride copolymer was added to anhydrous ethanol at a solid-liquid mass ratio of 1:11.8 and stirred and dissolved for 30 minutes in a 70-degree water bath to prepare a uniform bridging layer polymer dispersion with a dispersion concentration of 67 g / L.

[0085] Coating operation: Turn on the dual-fluid atomizing nozzle and atomize the bridging layer polymer dispersion into the fluidization chamber at a feed rate of 1.5 g / min. The atomization pressure is 0.25 MPa. Maintain the fluidization chamber temperature at 90 degrees Celsius and the fluidization velocity at a stable level. Based on the optimal thickness δ... opt The specific calculation formula for controlling the coating time is as follows: In the formula, t coat The time for the bridging layer to be applied is in minutes. is the mass fraction of the styrene-maleic anhydride copolymer in the dispersion (taken as 1 / 12.8≈7.81%); r is the average radius of the expanded graphite particles, in centimeters; ρ represents the density of the styrene-maleic anhydride copolymer, taken as 1.05 g / cm³; Q represents the feed rate of the dispersion, in grams per minute.

[0086] Drying and curing: After coating, the temperature of the fluidization chamber is raised to 110 degrees Celsius and kept in a fluidized state for 60 minutes to allow the bridging layer polymer to fully cure and form a dense and uniform bridging layer.

[0087] Model-based functional unit verification specifically includes:

[0088] Morphology and thickness verification: Take 3-5 coated particles and observe the surface morphology using a scanning electron microscope. The coating must be continuous, without peeling or agglomeration. Use a coating thickness measuring instrument to measure the total thickness of the moisture-proof layer and bridging layer of different particles. The measurement points should be no less than 5, and the total thickness deviation should be ≤±5%.

[0089] Polarity verification: A contact angle meter (model DSA100) was used to measure the contact angles of the modeled functional unit surface with deionized water and high-purity diiodomethane, respectively. Each test solution was repeated 5 times, and the average value was taken. The total surface energy, polar component, and dispersion component were calculated using the Owens-Wendt equation to obtain the polarity parameters, which need to be compared with the optimal polarity parameter χ. opt Deviation ≤ ±0.03;

[0090] Glass transition temperature verification: The glass transition temperature of the bridging layer material was determined using a differential scanning calorimeter. The test conditions were a nitrogen atmosphere, flow rate of 50 mL / min, heating rate of 10 °C / min, and a test range of 30-150 °C. The measured glass transition temperature should be within the range of 80-100 °C. The specific values ​​(T) were recorded. g ;

[0091] Acceptance criteria: If all four indicators—morphology, thickness, polarity, and glass transition temperature—meet the requirements, the fabrication of the model functional unit is deemed qualified. If any one of them fails to meet the requirements, the corresponding coating process parameters, such as the feed rate and coating temperature, should be adjusted, and the coating process should be repeated.

[0092] S4: The modeled functional unit is mixed and plasticized with the polymer base material, and a physical foaming agent is injected under supercritical conditions to form a uniform composite melt.

[0093] The modeled functional unit is mixed and plasticized with the polymer base material, and the specific process is as follows:

[0094] Material mixing: Weigh polystyrene granules and qualified model functional units at a mass ratio of 90:10, add them to a high-speed mixer, set the mixing speed to 1500 rpm and the mixing time to 10 minutes to ensure that the two materials are initially dispersed evenly to obtain a premixed material; control the temperature of the mixing chamber at 40 degrees during the mixing process to avoid the polystyrene granules from sticking together due to excessive temperature.

[0095] Melt plasticizing: The premixed material is continuously fed into the feed inlet of a twin-screw extruder, and melt plasticizing is achieved through screw shearing and segmented temperature control. The temperature settings for each segment of the twin-screw extruder are as follows: feed section 160 degrees, compression section 180 degrees, homogenization section 200 degrees, and the screw speed is set to 200 rpm. During the plasticizing process, the melt state is monitored through the visual observation window of the extruder. It is necessary to ensure that the melt is continuous and there are no obvious particulate material residues. After plasticizing, a preliminary polymer-functional unit composite melt is obtained.

[0096] A physical foaming agent is injected under supercritical conditions to form a homogeneous composite melt. The specific process is as follows:

[0097] Supercritical foaming agent injection: A dedicated injection port is set in the homogenization section of the twin-screw extruder, and food-grade carbon dioxide is injected into the composite melt through a high-pressure metering pump. Before injection, the carbon dioxide needs to be pretreated to a supercritical state. The supercritical state control conditions are a temperature of 31 degrees Celsius and a pressure of 8 MPa. The injection pressure is set to 22 MPa to ensure that the supercritical carbon dioxide can penetrate smoothly into the melt. The injection rate is adjusted by a mass flow controller and set to 0.5-1.0 g / min to match the extruder feed rate, ensuring that the foaming agent has a stable concentration in the melt.

[0098] Composite melt: After homogenization and injection of supercritical carbon dioxide, the composite melt continues to be sheared and homogenized in the subsequent mixing section of a twin-screw extruder. The screw in the mixing section adopts an interlocking thread structure to enhance the shearing and mixing effect. The homogenization time is controlled at 3 minutes. After homogenization, the melt pressure is monitored by an online pressure sensor at the extruder die head. The pressure needs to be kept stable at 15-18 MPa to ensure that the supercritical carbon dioxide is fully dissolved in the melt and no bubbles are released.

[0099] Homogenization effect verification: Take a small amount of homogenized composite melt from the sampling port of the extruder head and observe the dissolution state of the foaming agent using a polarizing microscope. There should be no obvious bubble agglomeration. Measure the melt viscosity using a rotational rheometer. The viscosity deviation of the same batch of samples should be ≤±3% to ensure that the melt uniformity meets the requirements of subsequent extrusion molding.

[0100] S5: Establish a non-isothermal mathematical model, and solve it based on the solubility parameter of the physical foaming agent and the glass transition temperature of the amphiphilic polymer bridging layer to obtain a dynamic temperature control program for generating a spatial gradient temperature field at the extrusion die and the shaping die.

[0101] The non-isothermal mathematical model was constructed, numerical iterative solutions were obtained, and the temperature control program was generated and verified in sequence. The specific process is as follows:

[0102] The construction of non-isothermal mathematical models specifically includes:

[0103] Model assumptions: The computational domain is defined as the entire flow channel of the extrusion die and the shaping die. The extrusion die is 100mm long with an inner diameter of 20mm, and the shaping die is 300mm long with an inner diameter matching the target size of the profile. The model only considers the temperature distribution along the axial direction (melt flow direction) and radial direction of the flow channel, ignoring circumferential temperature differences. Radial heat transfer during melt flow is ignored, and only convective and conductive heat transfer are considered. The diffusion process of the foaming agent is driven only by temperature and concentration gradients, ignoring the influence of gravity on diffusion. The glass transition temperature of the amphiphilic polymer bridging layer is the critical temperature for abrupt change in melt viscosity. Above this critical temperature, the melt viscosity decreases significantly, and below this critical temperature, the viscosity increases sharply.

[0104] The governing equations were established, including the energy control equation, the foaming agent mass transfer equation, and the viscosity-temperature correlation equation. The specific establishment method is as follows:

[0105] The energy control equation, used to describe the temperature field distribution within the flow channel, is as follows: In the formula, ρ m The density of the composite melt is expressed in kg / m³, and is taken as 1050 kg / m³; c p λ represents the isobaric specific heat capacity of the composite melt, in J / (kg·K), with a value of 1800 J / (kg·K); u is the axial velocity of the melt, in m / s; v is the radial velocity of the melt, in m / s; T is the temperature, in K; x is the axial coordinate, in m; R is the radial coordinate of the flow channel, in m; λ m q represents the thermal conductivity of the composite melt, expressed in W / (m·K), with a value of 0.13 W / (m·K); vis This refers to the melt shear-viscosity dissipation power, expressed in W / m³, and the specific calculation formula is as follows: ( This refers to the melt shear rate, measured in seconds (s). -1 (Calculated from the velocity gradient within the flow channel)

[0106] The mass transfer equation for blowing agents, used to describe the diffusion behavior of blowing agents, is as follows: In the formula, C is the concentration of the blowing agent in the melt, in cm³(STP) / cm³; t is time, in seconds; D(T) is the temperature-dependent diffusion coefficient of the blowing agent, obtained by modifying the diffusion coefficient correlation D=k²P+b² using the Arrhenius equation, and the modified form is as follows: E d R is the diffusion activation energy, expressed in J / mol, with a value of 25000 J / mol. g T0 is the gas constant, with a value of 8.314 J / (mol・K); T0 is the reference temperature, in K, with a value of 473 K.

[0107] The viscosity-temperature correlation equation, used to correlate temperature and melt viscosity, supports the calculation of viscous dissipation. The equation is as follows: In the formula, η(T) is the temperature-dependent viscosity of the composite melt, in Pa·s; η0 is the reference viscosity, in Pa·s, with a value of 1000 Pa·s; E η T is the viscosity activation energy, expressed in J / mol, with a value of 40,000 J / mol. g R is the glass transition temperature of the amphiphilic polymer bridging layer, expressed in K. g This is the gas constant, with a value of 8.314 J / (mol・K);

[0108] Boundary condition settings include:

[0109] Inlet boundary: The melt temperature at the extrusion die inlet is 473K. The foaming agent concentration is calculated by the solubility coefficient correlation formula S=k1P+b1, which corresponds to the equilibrium concentration at an inlet pressure of 15-18MPa.

[0110] Wall boundary: The wall of the die and the shaping die is a temperature control boundary. The wall temperature can be dynamically adjusted according to the axial position and time. The convective heat transfer coefficient between the wall and the melt is 50W / (m²・K).

[0111] Exit boundary: The melt pressure at the mold exit is atmospheric pressure, taken as 0.1 MPa, and the temperature is T. g +20K ensures structural stability after the profile is shaped.

[0112] The numerical iterative solution and temperature control parameter optimization process are as follows:

[0113] MATLAB R2023b numerical computation software was selected, and the finite element method was used to discretize and solve the governing equations. A structured mesh was generated for the computational domain of the extrusion die and the shaping die flow channel, with an axial mesh step size of 1 mm and a radial mesh step size of 0.25 mm, for a total of 16,000 meshes (400 axial × 40 radial). The mesh quality verification pass rate was ≥95%. The inlet boundary temperature, foaming agent concentration, and initial wall temperature were assigned to the computational domain, with the initial wall temperature set to 453 K. The iteration convergence accuracy was set to 10. -4 An implicit time integral scheme was used for iterative calculations, solving the energy equation and mass transfer equation sequentially to obtain the temperature distribution and foaming agent concentration distribution at different axial positions and time points. With "uniform foaming agent nucleation" and "melt stability" as optimization objectives, uniform foaming agent nucleation requires a concentration distribution standard deviation ≤5%, and melt stability requires an outlet temperature fluctuation ≤±2K. The wall temperatures of different axial regions of the die and forming die were adjusted to obtain the optimal solution for temperature variation with axial position and time, denoted as T. opt (x,t).

[0114] The dynamic temperature control program is generated and verified, and the specific process is as follows:

[0115] Dynamic temperature control program conversion: converting the T obtained from numerical solution opt(x,t) is transformed into zoned dynamic temperature control parameters for the extrusion die and the shaping die, specifically divided into 3 control zones: the front section of the die, the rear section of the die, and the shaping die. The front section of the die corresponds to 0-50mm of the flow channel axis, the rear section of the die corresponds to 50-100mm, and the shaping die corresponds to 100-400mm. The initial temperature, heating or cooling rate, and stable temperature of each zone are clearly defined, forming a dynamic temperature control program that includes time nodes, zone numbers, target temperatures, and temperature control accuracy. The temperature control accuracy is set to ±1K, and the program format is adapted to the PLC control system of the extrusion molding equipment.

[0116] Program Validation: The feasibility of the temperature control program was verified using a small-scale extrusion experimental platform. The dynamic temperature control program was imported into the equipment control system, and small-batch extrusion experiments were conducted using composite melt as raw material. The temperature distribution was monitored in real time by miniature temperature sensors embedded in the flow channel. The deviation between the measured actual temperature and the program-set temperature should be ≤ ±1.5K. Simultaneously, the cell structure of the extruded profile was observed; the average cell size deviation was ≤ ±10%, and the cell density was ≥ 10. 6 A value of 1 piece / cm³ indicates that the verification is successful.

[0117] S6: The composite melt is extruded and shaped through an extrusion die that executes the dynamic temperature control program.

[0118] The verified dynamic temperature control program is imported into the PLC control system of the extrusion molding equipment to complete the linkage debugging of the extruder, die, shaping die and auxiliary system; the prepared uniform composite melt is fed into the extrusion die under a pressure of 15-18MPa. The equipment performs gradient temperature control on multiple areas according to the program to ensure uniform nucleation of foaming agent and inhibit excessive growth of cells. At the same time, the temperature and pressure are monitored in real time and dynamically fine-tuned.

[0119] The initial shaped profile enters the shaping mold, where it is adhered to the mold wall by vacuum adsorption, and internal stress is reduced by gradient cooling. It is then cooled to room temperature by a combination of air cooling and water cooling.

[0120] After cooling, the profiles are pulled, cut to a fixed length, and trimmed and polished to complete the inspection of appearance, dimensional accuracy, and cell structure.

[0121] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0122] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing fireproof and moisture-proof micro-foamed profiles for building energy-saving thermal insulation materials, characterized in that, include: S1: Collect surface energy data of polymer base material, flame retardant and moisture-proof functional filler, as well as solubility parameters of physical foaming agent; S2: Establish a three-phase interfacial tension balance model, and calculate based on the surface energy data to obtain the polarity parameters and thickness of the coating material that minimizes the interfacial tension between the functional filler and the polymer melt. S3: Based on the polarity parameters and thickness of the coating material, a moisture-proof layer and an amphiphilic polymer bridging layer with a specific glass transition temperature are sequentially coated on the surface of the flame retardant particles to obtain a modeled functional unit. S4: The modeled functional unit is mixed and plasticized with the polymer base material, and a physical foaming agent is injected under supercritical conditions to form a uniform composite melt; S5: Establish a non-isothermal mathematical model, solve it based on the solubility parameter of the physical foaming agent and the glass transition temperature of the amphiphilic polymer bridging layer, and obtain a dynamic temperature control program for generating a spatial gradient temperature field at the extrusion die and the shaping die. S6: The composite melt is extruded and shaped through an extrusion die that executes the dynamic temperature control program.

2. The method for preparing a fireproof and moisture-proof micro-foamed profile for building energy-saving thermal insulation materials according to claim 1, characterized in that: The surface energy data was collected as follows: the polymer base material, flame retardant and moisture-proof filler were pretreated respectively, and the contact angle was measured by a contact angle meter using the pendant drop method with deionized water and high-purity diiodomethane as the test solution. The surface energy, dispersion component and polar component of each material were calculated according to the Owens-Winter equation.

3. The method for preparing a fireproof and moisture-proof micro-foamed profile for building energy-saving thermal insulation materials according to claim 1, characterized in that: The solubility parameters are obtained as follows: the solubility parameters include the solubility coefficient and the diffusion coefficient; they are measured by a high-pressure reactor and a gas chromatograph, and the correlation of the solubility coefficient is obtained by linear fitting, and the correlation of the diffusion coefficient is obtained by fitting according to Fick's second law.

4. The method for preparing a fireproof and moisture-proof micro-foamed profile for building energy-saving thermal insulation materials according to claim 1, characterized in that: The three-phase interfacial tension balance model is constructed as follows: the core system is set as polymer melt phase, amphiphilic polymer bridging layer phase, and hydrophobic silica-expanded graphite composite phase, focusing on the two interfaces between polymer melt and bridging layer, and between bridging layer and hydrophobic silica-expanded graphite composite phase; the relationship between the polar component, dispersion component and polar parameter of the surface energy of bridging layer is clarified, and the interfacial tension calculation formulas of the two interfaces are derived based on the Owens-Winter equation, the effective interfacial tension calculation formula is defined with the weight coefficient determined by the thickness of bridging layer, and the objective function including effective interfacial tension and process constraint terms is set.

5. The method for preparing a fireproof and moisture-proof micro-foamed profile for building energy-saving thermal insulation materials according to claim 1, characterized in that: The polarity parameters and thickness of the coating material are obtained as follows: the collected surface energy data are validated and a standardized parameter matrix is ​​formed. The initial values ​​of the polarity parameters and thickness parameters are set for iteration. The gradient descent method is used for iterative calculation. First, the thickness parameter is fixed to optimize the polarity parameter. Then, the optimized polarity parameter is fixed to optimize the thickness parameter. Finally, both parameters are optimized simultaneously until the objective function value meets the convergence criterion. The optimal polarity parameter and optimal thickness are then output.

6. The method for preparing a fireproof and moisture-proof micro-foamed profile for building energy-saving thermal insulation materials according to claim 1, characterized in that: The modeled functional units are obtained as follows: Flame retardant particles are dried and pretreated before being added to a fluidized bed coating device, preheated, and then purged with dry compressed air to achieve a stable fluidized state; a moisture-proofing agent is added to a solvent to disperse and prepare a moisture-proofing agent dispersion, which is then sprayed into the fluidized chamber through an atomizing nozzle for coating, and dried and cured to form a moisture-proofing agent layer; then, an amphiphilic polymer bridging layer material is added to a solvent to dissolve and prepare a bridging layer dispersion, which is then coated and dried and cured using the same equipment to form a bridging layer; The morphology, thickness, polarity, and glass transition temperature of the coated particles were verified. After all indicators were qualified, the model functional unit was obtained.

7. The method for preparing a fireproof and moisture-proof micro-foamed profile for building energy-saving thermal insulation materials according to claim 1, characterized in that: The composite melt is obtained as follows: the modeled functional units and polymer base material are added to a high-speed mixer in proportion and mixed evenly to obtain a premix; the premix is ​​fed into a twin-screw extruder, and melt plasticization is achieved through segmented temperature control and screw shearing to form a polymer-functional unit composite melt; in the homogenization section of the twin-screw extruder, a physical foaming agent pretreated to a supercritical state is injected into the composite melt through the injection port, and after shearing and homogenization in the mixing section, a uniform composite melt is formed.

8. The method for preparing a fireproof and moisture-proof micro-foamed profile for building energy-saving thermal insulation materials according to claim 1, characterized in that: The non-isothermal mathematical model is constructed as follows: the computational domain is set as the overall flow channel of the extrusion die and the shaping die, ignoring the effects of circumferential temperature difference, radiative heat transfer, and gravity on the diffusion of the foaming agent, and the glass transition temperature of the amphiphilic polymer bridging layer is used as the critical temperature for the sudden change in melt viscosity; energy control equations describing the temperature field distribution in the flow channel, mass transfer equations describing the diffusion behavior of the foaming agent, and viscosity-temperature correlation equations relating temperature and melt viscosity are established; the temperature and foaming agent concentration at the extrusion die inlet, the dynamic temperature control properties of the die and shaping die walls, and the pressure and temperature at the shaping die outlet are set as boundary conditions.

9. The method for preparing a fireproof and moisture-proof micro-foamed profile for building energy-saving thermal insulation materials according to claim 1, characterized in that: The dynamic temperature control program is obtained as follows: the control equations of the non-isothermal mathematical model are discretely solved to obtain the temperature distribution and foaming agent concentration distribution at different axial positions and time points in the flow channel; with the optimization objectives of uniform nucleation of the foaming agent and the stable state of the melt, the wall temperature of different axial regions of the die and the shaping die is adjusted to obtain the optimal solution of temperature change with axial position and time; the optimal solution is transformed into the dynamic temperature control parameters of the front section of the die, the rear section of the die, and the shaping die section, and the initial temperature, heating and cooling rate and stable temperature of each region are determined. After experimental verification that the deviation between the actual temperature and the set temperature meets the requirements, the dynamic temperature control program is formed.

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