Production process of extruded polystyrene thermal insulation board

Abstract

The application discloses a production process of extruded polystyrene thermal insulation board, which comprises the following steps: S1) polystyrene resin, gradient particle size graphene, surface modified nano silicon dioxide and flame retardant are mixed according to the weight ratio of 100:1-2:0.5-1:3-5, the gradient particle size graphene comprises three specifications with particle sizes of 0.1-0.5 microns, 1-2 microns and 3-5 microns, and is mixed according to the weight ratio of 1:2:1 to obtain a mixture; and S2) the mixture is pretreated at 80-85 DEG C for 4-6 hours under a vacuum degree of -0.08 MPa by using a mechanical shearing and ultrasonic wave composite dispersion device to obtain pretreated materials. The application adopts a compound foaming system of gradient particle size graphene, supercritical CO2 and cyclopentane, forms a multi-stage heat conduction network through the gradient particle size structure, significantly reduces the filler amount, effectively improves the heat conduction performance of the product, the fluorinated graphene has a core-shell structure, the compatibility with the matrix is improved, the interface bonding force is enhanced, and the problem of mechanical performance reduction caused by high filler amount is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of extruded polystyrene boards, in particular to a production process of extruded polystyrene insulation boards. Background Art

[0002] Extruded polystyrene (XPS) is a closed-cell foam insulation material made primarily from polystyrene resin, heated, mixed, and injected with a blowing agent, then extruded. Due to its low thermal conductivity, high compressive strength, and low water absorption, it is widely used in building exterior wall insulation, roof insulation, and floor insulation. Currently, XPS production processes both domestically and internationally primarily use Freon (F142b + F22) as a blowing agent, processed and formed using single-screw or twin-screw extruders. However, due to its high ODP value, Freon has been designated by the United Nations as an environmentally unfriendly product and is on the verge of being phased out globally.

[0003] To address the above-mentioned issues, the Chinese invention patent application number CN201710188788.7 discloses a process for producing extruded polystyrene boards using supercritical CO2 as the main foaming agent. This process improves the problem of high thermal conductivity caused by CO2 foaming by adding a high proportion of graphite and adopting a secondary steam foaming process. However, this solution still has the following limitations: 1) Although the addition of a high proportion of graphite improves thermal conductivity, it significantly reduces the mechanical properties of the material; 2) The temperature control accuracy of the single steam secondary foaming process is limited, making it difficult to achieve precise control; 3) It fails to fundamentally solve the problem of uneven cell structure caused by excessively rapid CO2 diffusion; 4) There is a lack of precise control means for the internal structure of the board, which affects the stability of product performance. In addition, conventional cooling methods in the prior art are difficult to achieve precise control, which can easily cause uneven stress distribution within the board, and the foaming agent is prone to premature decomposition in the screw barrel, affecting the foaming effect.

[0004] Therefore, there is an urgent need for a new production process for extruded polystyrene insulation boards that can not only solve the performance problems caused by environmentally friendly foaming agents, but also avoid the adverse effects of a high proportion of fillers on mechanical properties. At the same time, it has the ability to precisely control the foaming process, internal structure and cooling process to ensure the comprehensive performance of the product and process stability. Summary of the Invention

[0005] The object of the present invention is to provide a production process for an extruded polystyrene insulation board to solve the problems existing in the existing extruded polystyrene board production process mentioned in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a production process of an extruded polystyrene insulation board, comprising the following steps:

[0007] S1) mixing polystyrene resin, gradient particle size graphene, surface modified nano-silica, and flame retardant in a weight ratio of 100:1-2:0.5-1:3-5, wherein the gradient particle size graphene includes three specifications of particle size of 0.1-0.5 μm, 1-2 μm, and 3-5 μm, and the mixture is mixed in a weight ratio of 1:2:1 to obtain a mixed material;

[0008] S2) pretreating the mixed material at 80-85° C. for 4-6 hours using a mechanical shearing and ultrasonic composite dispersion device under a vacuum degree of −0.08 MPa to obtain a pretreated material;

[0009] S3) melt-extruding the pretreated material through a parallel co-rotating twin-screw extruder, wherein the barrel of the extruder includes a first temperature zone, a second temperature zone, a third temperature zone, a fourth temperature zone, and a fifth temperature zone, wherein the temperature of the first temperature zone is 140±2°C, the temperature of the second temperature zone is 145±2°C, the temperature of the third temperature zone is 150±2°C, the temperature of the fourth temperature zone is 148±2°C, and the temperature of the fifth temperature zone is 145±2°C, supercritical CO2 is injected into the second temperature zone at a pressure of 16-18 MPa, and cyclopentane is injected into the fourth temperature zone at a pressure of 2-3 MPa, wherein the mass ratio of CO2 to cyclopentane is 4:1-5:1, to obtain a foamed melt;

[0010] S4) forming the foamed melt through a special-shaped mold with a periodic micropore array, wherein the mold is provided with three-stage vacuum negative pressure chambers along the extrusion direction, wherein the micropore array has a pore diameter of 50-100 μm, a depth of 20-30 μm, and a spacing of 200-300 μm, to obtain a primary foamed sheet;

[0011] S5) cooling the primary foamed sheet in sequence through an atomizing cooling zone and a circulating water cooling zone, wherein the atomizing cooling zone uses 5-10 μm water mist at a pressure of 0.8-1.2 MPa, and the water temperature in the circulating water cooling zone is 15-20° C., to obtain a cooled sheet;

[0012] S6) treating the cooling plate with microwaves at a frequency of 2.45 GHz and a power density of 300-500 W / m² for 30-60 seconds, and then subjecting the cooling plate to hot air circulation aging to obtain a thermal insulation plate.

[0013] Preferably, the surface-modified nano-silica is modified with KH550, has a specific surface area of ​​180-220 m² / g, a surface grafting rate of 15-20%, and a surface loading of 0.5-1 wt% of silver nanoparticles.

[0014] Preferably, the foaming agent injection system includes a supercritical CO2 injection system and a cyclopentane injection system, wherein:

[0015] Supercritical CO2 injection system: After refrigeration and dehumidification, CO2 is pressurized to above the critical pressure by a high-pressure plunger pump and heated to 40-45°C in a heat exchanger. When the ambient temperature is below 20°C, the injection pressure is 18-20MPa and the flow rate is 0.8-1.0kg / h; when the ambient temperature is 20-30°C, the injection pressure is 16-18MPa and the flow rate is 0.6-0.8kg / h; when the ambient temperature is above 30°C, the injection pressure is 14-16MPa and the flow rate is 0.4-0.6kg / h.

[0016] Cyclopentane injection system: Use a metering pump to accurately inject at a flow rate of 0.2-0.3kg / h and an injection pressure of 2-3MPa.

[0017] Preferably, the three-stage vacuum negative pressure chamber is divided into three independent chambers by two partitions, and each chamber is pumped to a negative pressure of -0.04MPa, -0.06MPa and -0.08MPa respectively by a vacuum pump. The length ratio of each chamber is 1:1.5:2, and sealing baffles are set between the chambers.

[0018] Preferably, the gas-liquid two-phase cooling system also includes an intelligent temperature field control unit, which monitors the surface temperature distribution of the plate in real time through an infrared thermal imager, and automatically adjusts the cooling parameters when it detects that the temperature unevenness exceeds ±2°C; the micro-water channel cooling adopts a variable-section spiral channel design, and the channel cross-sectional area gradually decreases from the inlet to the outlet, with a reduction ratio of 30-40%.

[0019] Preferably, the microwave treatment is carried out in a rectangular resonant cavity, using TE103 mode, and nitrogen is introduced at a flow rate of 2-3 L / min during the treatment.

[0020] Preferably, the gradient particle size graphene is surface fluorinated with a fluorination degree of 10-15%, has a core-shell structure, and a shell thickness of 2-5 nm.

[0021] Preferably, the second temperature zone and the fourth temperature zone of the parallel co-rotating twin-screw extruder are respectively provided with independent foaming agent injection systems, each injection system includes: a storage tank, a booster pump, a metering pump, a buffer and an injection port, a one-way valve is provided at the injection port, and the connecting pipeline between the injection port and the barrel adopts a heating and insulation structure.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) This application uses a composite foaming system of gradient-sized graphene with supercritical CO2 and cyclopentane. The gradient-sized structure forms a multi-level thermal conductivity network, significantly reducing the amount of filler while effectively improving the thermal conductivity of the product. The fluorinated graphene has a core-shell structure, which not only improves its compatibility with the matrix but also enhances interfacial bonding, thus avoiding the problem of decreased mechanical properties caused by high filler loading.

[0024] 2) This application innovatively designs a three-stage vacuum negative pressure molding system and a gas-liquid dual-phase cooling system with intelligent temperature field control. By gradually increasing the negative pressure along the extrusion direction and combining it with a microporous array mold, precise control of the foaming process is achieved. At the same time, a cooling method combining infrared thermal imaging monitoring with intelligent feedback control ensures uniformity during the sheet cooling process and effectively avoids internal stress concentration.

[0025] 3) This application sets up independent foaming agent injection systems in the second and fourth temperature zones, and adopts a heat-tracing and heat-insulating structure. By rationally controlling the injection pressure and temperature, the premature decomposition of the foaming agent is effectively prevented. In addition, the design of automatically adjusting the foaming agent injection parameters according to the ambient temperature significantly improves the adaptability and stability of the process.

[0026] 4) This application adopts a post-processing process that combines microwave treatment with hot air circulation aging. Through the precise electric field distribution control of the TE103 mode, the internal structure of the board is further optimized, and the dimensional stability and long-term performance of the product are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the process flow chart of this application;

[0028] Figure 2 Detailed process flow chart for this application;

[0029] Figure 3 This is a schematic diagram of the vacuum negative pressure chamber hole of the mold of this application;

[0030] Figure 4 Schematic diagram of the mold micropores of this application;

[0031] Figure 5 This is a schematic diagram of the parallel co-rotating twin-screw extruder of the present application. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] In the description of the invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," "the other end," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In the description of the invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "provided with," "connected," etc., should be understood broadly. For example, "connected" may refer to a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0035] In the description of the invention, it should be noted that the execution order of the steps is not limited by the serial numbers. The order of some steps can be changed, the steps can be executed simultaneously, and the steps can be executed separately, all of which are within the scope of protection of this application.

[0036] See also Figure 1-5 The present invention provides a technical solution: a production process of an extruded polystyrene insulation board, comprising the following steps:

[0037] S1) mixing polystyrene resin, gradient particle size graphene, surface modified nano-silica, and flame retardant in a weight ratio of 100:1-2:0.5-1:3-5, wherein the gradient particle size graphene includes three specifications of particle size of 0.1-0.5 μm, 1-2 μm, and 3-5 μm, and the mixture is mixed in a weight ratio of 1:2:1 to obtain a mixed material;

[0038] S2) pretreating the mixed material at 80-85° C. for 4-6 hours using a mechanical shearing and ultrasonic composite dispersion device under a vacuum degree of -0.08 MPa to obtain a pretreated material;

[0039] S3) melt-extruding the pretreated material through a parallel co-rotating twin-screw extruder, wherein the barrel of the extruder includes a first temperature zone, a second temperature zone, a third temperature zone, a fourth temperature zone, and a fifth temperature zone, wherein the temperature of the first temperature zone is 140±2°C, the temperature of the second temperature zone is 145±2°C, the temperature of the third temperature zone is 150±2°C, the temperature of the fourth temperature zone is 148±2°C, and the temperature of the fifth temperature zone is 145±2°C, supercritical CO2 is injected into the second temperature zone at a pressure of 16-18 MPa, and cyclopentane is injected into the fourth temperature zone at a pressure of 2-3 MPa, wherein the mass ratio of CO2 to cyclopentane is 4:1-5:1, to obtain a foamed melt;

[0040] S4) forming the foamed melt through a shaped die with a periodic micropore array, wherein the die is provided with three-stage vacuum negative pressure chambers along the extrusion direction, wherein the micropore array has a pore diameter of 50-100 μm, a depth of 20-30 μm, and a spacing of 200-300 μm, to obtain a primary foamed sheet;

[0041] S5) cooling the primary foamed sheet in turn through an atomizing cooling zone and a circulating water cooling zone, wherein the atomizing cooling zone uses 5-10 μm water mist at a pressure of 0.8-1.2 MPa, and the water temperature in the circulating water cooling zone is 15-20° C., to obtain a cooled sheet;

[0042] S6) treating the cooling plate with microwaves at a frequency of 2.45 GHz and a power density of 300-500 W / m² for 30-60 seconds, and then subjecting the plate to hot air circulation aging to obtain an insulation plate.

[0043] Specifically, this application uses gradient particle size graphene to replace traditional graphite fillers. Through the gradient structure of three specifications of 0.1-0.5μm, 1-2μm and 3-5μm, a multi-scale thermal conductive network is formed. Graphene of different sizes forms interconnected channels in the matrix. Large-sized graphene provides the main thermal conductive path, medium-sized graphene fills the connection gaps, and micron-sized particles fill the tiny gaps. This multi-level combination significantly improves the thermal conductivity efficiency. At the same time, since the total filling amount is only 1-2 parts (relative to 100 parts of polystyrene resin), it is far lower than the amount added in the prior art, effectively avoiding the problem of mechanical property degradation caused by high filling. In addition, the process adopts a synergistic foaming system of high-pressure CO2 and cyclopentane. By injecting it in different temperature zones, it not only ensures environmental protection, but also overcomes the defect of a single CO2 foaming agent diffusing too quickly.

[0044] Reference Manual Figure 1 Steps S1-S6 are raw material premixing, pretreatment, twin-screw extrusion, mold forming, cooling treatment, and microwave treatment, respectively.

[0045] Example 1

[0046] S1) mixing 100 parts of a polystyrene resin, 1.5 parts of graphene with gradient particle sizes (graphene with particle sizes of 0.1-0.5 μm, 1-2 μm, and 3-5 μm, mixed in a weight ratio of 1:2:1), 0.8 parts of nano-silica modified with KH550 (specific surface area of ​​200 m² / g, surface grafting rate of 18%, and surface loading of 0.8 wt% of silver nanoparticles), and 4 parts of a flame retardant to obtain a mixture;

[0047] S2) pretreating the mixed material at 82° C. for 5 hours using a mechanical shearing and ultrasonic composite dispersion device under a vacuum degree of −0.08 MPa to obtain a pretreated material;

[0048] S3) melt-extrude the pretreated material through a parallel co-rotating twin-screw extruder, wherein the temperatures in the first temperature zone are 140° C., the second temperature zone is 145° C., the third temperature zone is 150° C., the fourth temperature zone is 148° C., and the fifth temperature zone is 145° C.; supercritical CO2 is injected into the second temperature zone at a pressure of 17 MPa, and cyclopentane is injected into the fourth temperature zone at a pressure of 2.5 MPa; the mass ratio of CO2 to cyclopentane is 4.5:1, to obtain a foamed melt;

[0049] S4) forming the foamed melt through a shaped die with a periodic micropore array, wherein the die has three vacuum chambers with pressures of -0.04 MPa, -0.06 MPa, and -0.08 MPa, respectively, along the extrusion direction, and the micropore array has a pore diameter of 75 μm, a depth of 25 μm, and a spacing of 250 μm, to obtain a primary foamed sheet;

[0050] S5) cooling the primary foamed sheet in turn through an atomizing cooling zone and a circulating water cooling zone, wherein the atomizing cooling zone uses 8 μm water mist at a pressure of 1.0 MPa and the water temperature in the circulating water cooling zone is 18° C., thereby obtaining a cooled sheet;

[0051] S6) The cooling plate is subjected to microwave treatment at a frequency of 2.45 GHz and a power density of 400 W / m² for 45 seconds, followed by hot air circulation aging to obtain an insulation plate.

[0052] The insulation board prepared in Example 1 was tested, and the test results are as follows:

[0053] Thermal conductivity: 0.028 W / (m·K);

[0054] Compressive strength: 320 kPa;

[0055] Closed cell rate: 98.5%;

[0056] Dimensional stability: 0.6%;

[0057] Filler dispersion: coefficient of variation 2.3%;

[0058] Average cell diameter: 180 μm;

[0059] Standard deviation of cell diameter: ±15μm.

[0060] The thermal insulation board prepared in Example 1 was tested, and the physical and chemical index data obtained were as follows:

[0061] Table 1 Physical and chemical indicators of Example 1

[0062] Test items Test standards Test conditions Test results Thermal conductivity GB / T 10294-2008 Temperature: 25±0.5℃, relative humidity: 50±5%, test sample size: 300×300×30mm 0.028 W / (m·K) Compressive strength GB / T 8813-2008 Temperature: 23±2℃, loading speed: 5mm / min, test sample size: 100×100×30mm 320 kPa Closed-cell rate GB / T 30595-2014 Temperature: 23±2℃, relative humidity: 50±5%, test sample size: 50×50×30mm 98.5% Dimensional stability GB / T 8811-2008 Temperature: 70±2℃, time: 48h, test sample size: 300×300×30mm 0.6% Filler dispersion Thermal conductivity uniformity test Measure thermal conductivity at 9 different locations on the sample and calculate the coefficient of variation Coefficient of variation: 2.3% Average cell diameter Indirect determination of water absorption After the sample is immersed in water for 48 hours, the water absorption rate is measured and calculated based on the density. 180±15μm

[0063] Thus, in Example 1, the optimal performance combination was achieved through the synergistic effect of gradient particle size graphene, surface modified nano-silica and fluorination treatment, especially the thermal conductivity reached 0.028 W / (m·K) while maintaining a high compressive strength of 320 kPa. The high dispersion of the filler and the uniform pore structure proved the rationality of the process parameters. The closed porosity of 98.5% and the dimensional stability of 0.6% showed that the product had excellent thermal insulation performance and stability in use.

[0064] Specifically, in closed-cell extruded polystyrene boards, water absorption primarily occurs in the open cells on the material surface and cut surfaces. Water absorption is closely related to the cell structure (including cell diameter, distribution, and connectivity). The following method indirectly estimates cell diameter based on the sample's water absorption, density, and theoretical calculation formula:

[0065] Calculation formula:

[0066] in:

[0067] d is the average cell diameter (μm);

[0068] V p is the total volume of the sample (mm³);

[0069] P is the porosity (which can be calculated from the density);

[0070] S is the surface area of ​​the cells per unit volume (which can be calculated indirectly by water absorption);

[0071] Porosity calculation:

[0072] in:

[0073] P is the porosity;

[0074] ρ a is the apparent density of the sample (g / cm³);

[0075] ρ t is the theoretical density of polystyrene (g / cm³), which is approximately 1.05 g / cm³;

[0076] Calculation of cell surface area per unit volume:

[0077]

[0078] in:

[0079] S is the total surface area of ​​cells per unit volume (mm² / mm³);

[0080] W w is the water absorption of the sample (expressed as a decimal, e.g. 0.92% should be 0.0092);

[0081] ρ a is the apparent density of the sample (g / cm³);

[0082] h is the density of water (g / cm³), which is 1 g / cm³;

[0083] σ is the surface tension coefficient of water (N / m);

[0084] t is the test time (h);

[0085] Take the sample in Example 1 and measure the following data:

[0086] Apparent density (ρ a ):0.035g / cm³;

[0087] Water absorption (W w ):0.92% (48 hours water immersion test);

[0088] Sample volume (V p ):10cm³;

[0089] Calculation steps:

[0090] 1. Calculate porosity: P = 1 (0.035 / 1.05) = 0.967 (96.7%)

[0091] 2. Calculate the surface area of ​​pores per unit volume:

[0092] Assume that the surface tension coefficient of water is σ = 72.8 mN / m, the water density is h = 1 g / cm³, and the test time is t = 48 hours.

[0093] S=(0.92%×0.035) / (1×72.8×10⁻³×48)=9.25×10⁻ 6 cm² / cm³;

[0094] 3. Calculate the average cell diameter:

[0095] d=√[6×10×(1-0.967) / (9.25×10⁻6 ×0.967)]

[0096] d = 4,528 μm;

[0097] 4. Application of correction factors:

[0098] In extruded polystyrene boards, the empirical correction factor is approximately 0.04.

[0099] d 校正 =4,528×0.04=181μm.

[0100] The average cell diameters of the samples in the following examples and comparative examples can be calculated in this way.

[0101] Example 2:

[0102] S1) mixing 100 parts of polystyrene resin, 1.2 parts of gradient particle size graphene (other proportions are the same as in Example 1), 0.6 parts of KH550-modified nano-silica (other parameters are the same as in Example 1), and 4 parts of a flame retardant to obtain a mixed material;

[0103] Steps S2-S6 are the same as in Example 1.

[0104] The insulation board prepared in Example 2 was tested, and the test results are as follows:

[0105] Thermal conductivity: 0.029 W / (m·K);

[0106] Compressive strength: 305 kPa;

[0107] Closed cell rate: 98.0%;

[0108] Dimensional stability: 0.7%;

[0109] Filler dispersion: coefficient of variation 3.1%;

[0110] Average cell diameter: 185 μm;

[0111] Standard deviation of cell diameter: ±18μm.

[0112] The thermal insulation board prepared in Example 2 was tested, and the physical and chemical index data obtained were as follows:

[0113] Table 2 Physical and chemical indicators of Example 2

[0114] Test items Test standards Test conditions Test results Thermal conductivity GB / T 10294-2008 Same as Example 1 0.029 W / (m·K) Compressive strength GB / T 8813-2008 Same as Example 1 305 kPa Closed-cell rate GB / T 30595-2014 Same as Example 1 98.0% Dimensional stability GB / T 8811-2008 Same as Example 1 0.7% Filler dispersion Thermal conductivity uniformity test Same as Example 1 Coefficient of variation: 3.1% Average cell diameter Indirect determination of water absorption Same as Example 1 185±18μm

[0115] Thus, despite reducing the amount of gradient-sized graphene and modified nano-silica in Example 2, good overall performance was still maintained. The thermal conductivity (0.029 W / (m·K)) and compressive strength (305 kPa) were slightly lower than those in Example 1. The process of the present invention has a wide operating window and can adapt to different formulation requirements.

[0116] Comparative Example 1:

[0117] Compared with Example 1, ordinary graphite powder was used instead of gradient particle size graphene, and other conditions were the same.

[0118] S1: 100 parts of polystyrene resin, 1.5 parts of graphite powder (average particle size 2 μm), 0.8 parts of nano-silica modified by KH550 (parameters are the same as those in Example 1), and 4 parts of flame retardant are mixed to obtain a mixed material;

[0119] Steps S2-S6 are the same as in Example 1.

[0120] The insulation board prepared in Comparative Example 1 was tested, and the test results were as follows:

[0121] Thermal conductivity: 0.032 W / (m·K);

[0122] Compressive strength: 280 kPa;

[0123] Closed cell rate: 97.0%;

[0124] Dimensional stability: 1.2%;

[0125] Filler dispersion: coefficient of variation 9.5%;

[0126] Average cell diameter: 200 μm;

[0127] Standard deviation of cell diameter: ±35μm.

[0128] The thermal insulation board prepared in Comparative Example 1 was tested, and the physical and chemical index data obtained were as follows:

[0129] Table 3 Physical and chemical indicators of Comparative Example 1

[0130] Test items Test standards Test conditions Test results Thermal conductivity GB / T 10294-2008 Same as Example 1 0.032 W / (m·K) Compressive strength GB / T 8813-2008 Same as Example 1 280 kPa Closed-cell rate GB / T 30595-2014 Same as Example 1 97.0% Dimensional stability GB / T 8811-2008 Same as Example 1 1.2% Filler dispersion Thermal conductivity uniformity test Same as Example 1 Coefficient of variation 9.5% Average cell diameter Indirect determination of water absorption Same as Example 1 200±35μm

[0131] By comparing Comparative Example 1 with Example 1, it can be seen that after gradient particle size graphene is used to replace ordinary graphite powder:

[0132] 1) The thermal conductivity is significantly reduced from 0.032 to 0.028 W / (m·K);

[0133] 2) Compressive strength increased by approximately 14.3%;

[0134] 3) The dispersion of fillers is greatly improved and the agglomeration phenomenon is significantly reduced;

[0135] 4) The cell structure is more uniform, and the standard deviation of the diameter is reduced by 57%.

[0136] Therefore, in Comparative Example 1, replacing the gradient-sized graphene with ordinary graphite powder resulted in a significant performance degradation. The higher thermal conductivity (0.032 W / (m·K)) and larger coefficient of variation indicate that gradient particle size design is crucial for improving thermal conductivity and dispersibility. The large standard deviation of cell diameter (±35 μm) suggests that the graphite powder affected foaming uniformity.

[0137] The surface-modified nano-silica is modified with KH550, with a specific surface area of ​​180-220m² / g, a surface grafting rate of 15-20%, and a surface loading of 0.5-1wt% silver nanoparticles. Specifically, due to the good compatibility of the amino groups in the KH550 molecule with the polystyrene matrix, the high specific surface area provides sufficient nucleation sites, while the control of the surface grafting rate ensures the modification effect without excessively affecting the dispersibility. In addition, after the surface is loaded with 0.5-1wt% silver nanoparticles, the silver nanoparticles not only provide additional heat conduction channels, but also have a synergistic nucleation effect, which can provide more uniform bubble nucleation points.

[0138] Comparative Example 2:

[0139] Compared with Example 1, ordinary nano-silica without KH550 modification was used, and other conditions were the same.

[0140] S1: 100 parts of polystyrene resin, 1.5 parts of gradient particle size graphene (the ratio is the same as in Example 1), 0.8 parts of ordinary nano-silica (specific surface area 200 m² / g, without surface modification) and 4 parts of flame retardant are mixed to obtain a mixed material;

[0141] Steps S2-S6 are the same as in Example 1.

[0142] The insulation board prepared in Comparative Example 2 was tested, and the test results were as follows:

[0143] Thermal conductivity: 0.031 W / (m·K);

[0144] Compressive strength: 290 kPa;

[0145] Closed cell rate: 97.5%;

[0146] Dimensional stability: 1.0%;

[0147] Filler dispersion: coefficient of variation 7.2%;

[0148] Average cell diameter: 195 μm;

[0149] Standard deviation of cell diameter: ±28μm.

[0150] The insulation board prepared in Comparative Example 2 was tested, and the physical and chemical index data were as follows:

[0151] Table 4 Physical and chemical indicators of Comparative Example 2

[0152] Test items Test standards Test conditions Test results Thermal conductivity GB / T 10294-2008 Same as Example 1 0.031 W / (m·K) Compressive strength GB / T 8813-2008 Same as Example 1 290 kPa Closed-cell rate GB / T 30595-2014 Same as Example 1 97.5% Dimensional stability GB / T 8811-2008 Same as Example 1 1.0% Filler dispersion Thermal conductivity uniformity test Same as Example 1 Coefficient of variation 7.2% Average cell diameter Indirect determination of water absorption Same as Example 1 195±28μm

[0153] By comparing Comparative Example 2 with Example 1, it can be seen that after using nano-silica modified with KH550:

[0154] 1) Filler dispersibility is significantly improved;

[0155] 2) Thermal conductivity decreased by about 9.7%;

[0156] 3) The cell structure is more uniform, and the diameter standard deviation is reduced by 46%;

[0157] 4) Mechanical properties improved by approximately 10.3%.

[0158] Therefore, in Comparative Example 2, the nano-silica without KH550 modification resulted in poor filler dispersion, which in turn affected the thermal conductivity (0.031 W / (m·K)) and mechanical properties (290 kPa). This verifies the importance of surface modification for improving the compatibility between the filler and the matrix.

[0159] The foaming agent injection system includes a supercritical CO2 injection system and a cyclopentane injection system, wherein:

[0160] Supercritical CO2 injection system: After refrigeration and dehumidification, CO2 is pressurized to above the critical pressure by a high-pressure plunger pump and heated to 40-45°C in a heat exchanger. When the ambient temperature is below 20°C, the injection pressure is 18-20MPa and the flow rate is 0.8-1.0kg / h; when the ambient temperature is 20-30°C, the injection pressure is 16-18MPa and the flow rate is 0.6-0.8kg / h; when the ambient temperature is above 30°C, the injection pressure is 14-16MPa and the flow rate is 0.4-0.6kg / h.

[0161] Cyclopentane injection system: Use a metering pump to accurately inject at a flow rate of 0.2-0.3kg / h and an injection pressure of 2-3MPa.

[0162] Specifically, in the foaming agent injection system, lower temperatures require higher injection pressures and flow rates. This is because ambient temperature influences the heat transfer conditions in the barrel and mold, which in turn affects the decomposition kinetics of the foaming agent. For example, in low-temperature environments (<20°C), a high pressure of 18-20 MPa and a high flow rate of 0.8-1.0 kg / h can compensate for insufficient foaming caused by lower temperatures. In high-temperature environments, these parameters are reduced accordingly to avoid excessive foaming. This adaptive control solution significantly improves process adaptability and product quality stability.

[0163] Reference Manual Figure 3 The three-stage vacuum negative pressure chamber is divided into three independent chambers by two partitions. Each chamber is evacuated to a negative pressure of -0.04MPa, -0.06MPa, and -0.08MPa respectively by a vacuum pump. The length ratio of each chamber is 1:1.5:2, and a sealing baffle is set between the chambers. Specifically, the traditional process usually adopts a single negative pressure or a simple two-stage negative pressure, which makes it difficult to accurately control the foaming process. The present application divides the mold into three independent chambers by two partitions and adopts a progressive negative pressure of -0.04MPa, -0.06MPa, and -0.08MPa, which matches the length ratio of 1:1.5:2, forming a pressure gradient field along the product molding direction.

[0164] Specifically, the low negative pressure (-0.04 MPa) in the first chamber primarily controls initial foaming, initially reducing melt pressure and guiding bubbles to slowly nucleate, preventing cell merging and thus cell rupture caused by intense foaming. The moderate negative pressure (-0.06 MPa) in the second chamber promotes cell growth, further releasing pressure and promoting uniform bubble expansion. The high negative pressure (-0.08 MPa) in the third chamber is used for the final shaping of the cells, ultimately stabilizing the cell structure, expelling residual gas, and ensuring a smooth surface. This progressive negative pressure control enables precise regulation of the foaming process and results in a more uniform cell structure.

[0165] Reference Manual Figure 3 The three-stage vacuum negative pressure chamber is directly integrated into the mold and arranged in sequence along the flow direction of the extruded foaming melt (i.e. the length direction of the mold). The first chamber is set near the inlet end, the second chamber is set in the middle section, and the third chamber is set near the outlet end. Each chamber is connected to the mold molding cavity. The partition can be made of high-temperature resistant rubber or metal to ensure the sealing between the chambers while allowing the melt to pass continuously. The three-stage vacuum chamber is also the pre-processing area of ​​the mold molding cavity, responsible for the pre-forming and gas management of the foaming melt. After the vacuum chamber optimizes the bubble structure through gradient negative pressure, the melt enters the molding cavity to complete the shaping. The cavity length ratio (1:1.5:2) is designed to match the melt foaming dynamics requirements. The short front section can quickly reduce the pressure, and the long back section can be finely controlled.

[0166] Reference Manual Figure 4 A periodic array of micropores (pore size 50-100μm) on the mold surface extracts volatile gases (such as residual CO2 and cyclopentane) generated during the foaming process, preventing bubble bursting and surface defects. The micropore array on the mold cavity surface works in conjunction with the vacuum system to ensure efficient gas discharge while preventing melt clogging of the micropores. A gradient negative pressure prevents sudden bubble expansion or collapse, reducing the standard deviation of the cell diameter distribution by 30%-40%. The micropore array, combined with a high vacuum level (-0.08MPa), eliminates surface air marks, achieving a roughness (Ra) of ≤5μm. Furthermore, staged vacuuming reduces local pressure overload, extending mold life by 20%-30%.

[0167] The gas-liquid dual-phase cooling system also includes an intelligent temperature field control unit, which uses an infrared thermal imager to monitor the plate surface temperature distribution in real time. When temperature nonuniformity exceeds ±2°C, it automatically adjusts cooling parameters. Micro-channel cooling utilizes a variable-section spiral channel design, with the channel's cross-sectional area gradually decreasing by 30-40% from inlet to outlet. Specifically, this application combines infrared thermal imaging monitoring technology with an automatic adjustment system. In existing technologies, the cooling process often relies on empirical control, making real-time adjustment difficult. This application uses an infrared thermal imager to monitor the plate surface temperature distribution in real time. When temperature nonuniformity exceeds ±2°C, the system automatically adjusts cooling parameters. This closed-loop control ensures uniformity during the cooling process. In particular, the variable-section spiral channel design, through a gradual change in cross-sectional area along the flow direction (a 30-40% reduction), maintains a stable cooling water flow rate while compensating for pressure losses along the flow path, achieving a more uniform cooling effect.

[0168] Specifically, the gas-liquid dual-phase cooling system is located in the cooling section after the extruder outlet and the forming die. The first stage (gas phase) is an atomizing cooling device. Multiple atomizing nozzles are positioned above the atomizing cooling device, facing the sheet surface at a 45° angle. An exhaust system can be installed below the atomizing cooling device to collect the cooling mist. The second stage (liquid phase) is a water cooling device. The upper and lower water-cooling plates of the water cooling device are equipped with variable-section spiral channels within the plates. The channels have a larger cross-sectional area at the starting end and a smaller cross-sectional area at the end, and the channels are arranged spirally along the sheet's travel direction. The intelligent temperature field control system includes, but is not limited to, an infrared thermal imager and an infrared thermal imager. The infrared thermal imager is mounted above the cooling section, and a control unit is used to connect the infrared thermal imager and the cooling system. When the automatic adjustment mechanism is in operation, it adjusts the nozzle pressure and water flow rate when it detects uneven temperatures. The automatic adjustment mechanism provides real-time feedback control to ensure cooling uniformity. The variable-section spiral channel cooling structure is already existing and will not be described in detail here.

[0169] Microwave treatment is performed within a rectangular resonant cavity using the TE103 mode, an electromagnetic field distribution pattern with one half-wave across the cavity width and three half-waves along its length. Nitrogen is introduced at a rate of 2-3 L / min during the treatment process. Specifically, the TE103 mode, which describes an electromagnetic field distribution pattern with one half-wave across the cavity width and three half-waves along its length, creates a uniform electric field distribution within the sheet, avoiding the "hotspots" problem associated with conventional microwave treatment. The introduction of 2-3 L / min of nitrogen also serves a dual purpose: it prevents oxidation of the sheet at high temperatures and promotes temperature uniformity through convective heat transfer.

[0170] Specifically, a rectangular resonant cavity structure is placed after the cooling section. The rectangular cavity is a rectangular cavity adapted to the width of the plate. When in use, the rectangular cavity generates a specific electromagnetic field distribution in the TE103 mode. As the plate passes through the center of the cavity, microwave energy is evenly applied to the plate. A nitrogen protection system can be used to set air curtains at both ends of the cavity to prevent oxidation of the plate.

[0171] The gradient particle size graphene has been surface fluorinated to a degree of fluorination of 10-15%, and has a core-shell structure with a shell thickness of 2-5nm. Specifically, within the fluorination range of 10-15%, the fluorinated graphene maintains good thermal conductivity while significantly improving its interfacial compatibility with the polystyrene matrix. The design of a shell thickness of 2-5nm is based on the following mechanism: a shell that is too thin cannot provide sufficient interface regulation effect, while a shell that is too thick will affect thermal conductivity. This core-shell structure design achieves the dual functions of "thermal conductivity enhancement" and "interface compatibility", overcoming the problems of filler agglomeration and poor interfacial bonding in the existing technology.

[0172] Comparative Example 3:

[0173] Compared with Example 1, the gradient particle size graphene without fluorination treatment was used, and other conditions were the same.

[0174] Description of the fluorination treatment process: Graphene was dispersed in a 40 wt% hydrofluoric acid solution, reacted at 60°C for 4 hours, filtered, washed with water until neutral, and vacuum dried at 80°C for 12 hours to obtain fluorinated graphene with a fluorination degree of 12%, forming a fluorinated layer of 2-5 nm.

[0175] S1: 100 parts of polystyrene resin, 1.5 parts of non-fluorinated gradient particle size graphene (the same proportions as in Example 1), 0.8 parts of KH550-modified nano-silica (the same parameters as in Example 1), and 4 parts of flame retardant are mixed to obtain a mixed material;

[0176] Steps S2-S6 are the same as in Example 1.

[0177] The insulation board prepared in Comparative Example 3 was tested, and the test results are as follows:

[0178] Thermal conductivity: 0.030 W / (m·K);

[0179] Compressive strength: 295 kPa;

[0180] Closed cell rate: 97.8%;

[0181] Dimensional stability: 0.9%;

[0182] Filler dispersion: coefficient of variation 6.2%;

[0183] Average cell diameter: 190 μm;

[0184] Standard deviation of cell diameter: ±25μm.

[0185] The insulation board prepared in Comparative Example 3 was tested, and the physical and chemical index data were as follows:

[0186] Table 5 Physical and chemical indicators of comparative example 3

[0187] Test items Test standards Test conditions Test results Thermal conductivity GB / T 10294-2008 Same as Example 1 0.030 W / (m·K) Compressive strength GB / T 8813-2008 Same as Example 1 295 kPa Closed-cell rate GB / T 30595-2014 Same as Example 1 97.8% Dimensional stability GB / T 8811-2008 Same as Example 1 0.9% Filler dispersion Thermal conductivity uniformity test Same as Example 1 Coefficient of variation 6.2% Average cell diameter Indirect determination of water absorption Same as Example 1 190±25μm

[0188] By comparing Comparative Example 3 with Example 1, it can be seen that the gradient particle size graphene after fluorination treatment:

[0189] 1) Improved filler dispersion;

[0190] 2) Thermal conductivity decreased by about 6.7%;

[0191] 3) Compressive strength increased by about 8.5%;

[0192] 4) The cell structure is more uniform and the diameter standard deviation is reduced by 40%.

[0193] Therefore, in Comparative Example 3, although the gradient particle size graphene without fluorination treatment is better than ordinary graphite powder, its performance is not as good as that of Example 1. The poor dispersibility (coefficient of variation 6.2%) and low mechanical properties (295 kPa) indicate that fluorination treatment plays an important role in improving the interfacial bonding strength.

[0194] As an additional explanation, in the physical and chemical index tests of any of the aforementioned embodiments / comparative examples:

[0195] 1) Thermal conductivity test: This reflects the material's ability to conduct heat. The lower the value, the better the thermal insulation effect. Example 1 achieved 0.028 W / (m·K), which is better than the existing technology.

[0196] 2) Compressive strength test: This test measures a material's ability to withstand pressure. Higher values ​​indicate better mechanical properties. The 320 kPa value in Example 1 demonstrates improved thermal conductivity without sacrificing mechanical properties.

[0197] 3) Closed-cell rate test: reflects the degree of sealing of the foam structure, affecting thermal insulation performance and water absorption. A high closed-cell rate of 98.5% indicates excellent foaming technology;

[0198] 4) Dimensional stability test: This test characterizes the degree of deformation of the material at high temperatures. The smaller the value, the more stable it is. A low deformation rate of 0.6% indicates good product stability.

[0199] 5) Thermal conductivity uniformity test: The thermal conductivity is measured at 9 different locations on the sample (the center point and 8 evenly distributed points around it), and the coefficient of variation is calculated. The smaller the coefficient of variation, the more uniform the filler dispersion. The coefficient of variation (CV) calculation formula is: CV = (standard deviation / average) × 100%;

[0200] 6) Cell size test: This test reflects the uniformity of the foaming structure. The apparent density of the sample is measured using the Archimedes principle, and the true density of the material is measured using a pycnometer. The porosity is calculated and, combined with the known relationship between the total volume and number of pores, the average cell diameter can be calculated. The smaller the standard deviation, the more uniform the structure and the more stable the performance.

[0201] As an additional explanation, in the physical and chemical index tests of any of the aforementioned embodiments / comparative examples:

[0202] 1) Thermal conductivity: According to GB / T 10294-2008 standard, using a thermal conductivity tester, the test temperature is 25°C;

[0203] 2) Compressive strength: measured using a universal testing machine in accordance with GB / T 8813-2008;

[0204] 3) Closed porosity: measured according to GB / T 30595-2014;

[0205] 4) Dimensional stability: According to GB / T 8811-2008, the dimensional change rate is measured at 70°C for 48 hours;

[0206] 5) Filler dispersion: Measure thermal conductivity at 9 different locations on the sample and calculate the coefficient of variation;

[0207] 6) Average cell diameter: After the sample is immersed in water for 48 hours, the water absorption rate is measured and calculated based on the density.

[0208] As an additional explanation, in the physical and chemical index tests of any of the aforementioned embodiments / comparative examples:

[0209] 1) All tests were conducted under standard laboratory conditions (temperature 23±2°C, relative humidity 50±5%).

[0210] 2) Each set of data is the average value of 5 test samples.

[0211] Therefore, it can be seen from the test results of the aforementioned embodiments / comparative examples that: Example 1 and Example 2 both exhibit excellent comprehensive performance, and are significantly better than the three comparative examples; the coefficient of variation of Example 1 is the smallest (2.3%), indicating that the filler is most evenly dispersed; the coefficient of variation of Comparative Example 1 is the largest (9.5%), indicating that the use of ordinary graphite powder results in the most uneven dispersion of the filler, and gradient particle size graphene, surface modification and fluorination treatment are necessary; the present invention not only significantly improves the thermal conductivity of the product, but also maintains higher mechanical properties, thereby achieving an overall improvement in performance.

[0212] The second and fourth temperature zones of the parallel co-rotating twin-screw extruder are respectively equipped with independent foaming agent injection systems. Each injection system includes: a storage tank, a booster pump, a metering pump, a buffer and an injection port. A one-way valve is set at the injection port, and the connecting pipeline between the injection port and the barrel adopts a heating and insulation structure.

[0213] Specifically, the foaming agent injection system of this application is completely different from the simple injection methods used in the prior art. Each injection system includes a storage tank, a booster pump, a metering pump, a buffer, and an injection port, forming a complete and precise control system. The one-way valve at the injection port prevents material backflow, and the heating and insulation structure of the connecting pipeline, in particular, effectively prevents premature decomposition of the foaming agent during transportation by precisely controlling the temperature. This systematic design fundamentally solves various problems in the foaming agent transportation and injection process in the prior art, significantly improving the controllability of the process and the stability of product quality.

[0214] Specifically, the foaming agent injection system is installed on the twin-screw extruder. In the second temperature zone injection system (CO2), a storage tank is used to store liquid CO2, a booster pump pressurizes the CO2 to a supercritical state, a metering pump accurately controls the injection volume, and a buffer balances pressure fluctuations. The injection port is a dedicated injection device with a check valve. The fourth temperature zone injection system (cyclopentane) has the same structure as the second temperature zone injection system, but with lower pressure requirements and enhanced sealing and insulation design.

[0215] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A process for producing an extruded polystyrene insulation board, characterized in that: The steps include: S1) polystyrene resin, gradient particle size graphene, surface modified nano-silica and flame retardant are mixed in a ratio of 100:1-2:0.5-1:3-5 by weight, wherein the gradient particle size graphene includes three specifications with particle sizes of 0.1-0.5 μm, 1-2 μm and 3-5 μm, and the mixture is mixed in a weight ratio of 1:2:1 to obtain a mixed material; S2) pretreating the mixed material at 80-85° C. for 4-6 hours using a mechanical shearing and ultrasonic composite dispersion device under a vacuum degree of −0.08 MPa to obtain a pretreated material; S3) the pretreated material is melt-extruded by a parallel co-rotating twin-screw extruder, the barrel of the extruder comprises a first temperature zone, a second temperature zone, a third temperature zone, a fourth temperature zone and a fifth temperature zone, the temperature of the first temperature zone is 140 ± 2 ° C, the temperature of the second temperature zone is 145 ± 2 ° C, the temperature of the third temperature zone is 150 ± 2 ° C, the temperature of the fourth temperature zone is 148 ± 2 ° C, the temperature of the fifth temperature zone is 145 ± 2 ° C, supercritical CO is injected at a pressure of 16-18 MPa in the second temperature zone , cyclopentane is injected at a pressure of 2-3 MPa in the fourth temperature zone, CO The mass ratio of cyclopentane is 4: 1-5: 1 to obtain a foamed melt; S4) forming the foamed melt through a special-shaped mold with a periodic micropore array, wherein the mold is provided with three-stage vacuum negative pressure chambers along the extrusion direction, wherein the micropore array has a pore diameter of 50-100 μm, a depth of 20-30 μm, and a spacing of 200-300 μm, to obtain a primary foamed sheet; S5) cooling the primary foamed sheet in turn through an atomizing cooling zone and a circulating water cooling zone, wherein the atomizing cooling zone uses 5-10 μm water mist at a pressure of 0.8-1.2 MPa and the water temperature in the circulating water cooling zone is 15-20° C., to obtain a cooled sheet; S6) The cooling plate is subjected to a 2.45 GHz frequency and 300-500 W / m 2 After microwave treatment at a power density of 30-60 seconds, hot air circulation aging is performed to obtain an insulation board; The surface modified nano-silica is modified by KH550 and has a specific surface area of ​​180-220m 2 / g, surface grafting rate is 15-20%, and surface loading is 0.5-1wt% silver nanoparticles; The gradient particle size graphene is subjected to surface fluorination treatment, with a fluorination degree of 10-15%, has a core-shell structure, and a shell thickness of 2-5 nm.

2. The process for producing extruded polystyrene insulation board according to claim 1, characterized in that: The second temperature zone and the fourth temperature zone of the parallel co-rotating twin-screw extruder are respectively provided with independent foaming agent injection systems, each injection system includes: a storage tank, a booster pump, a metering pump, a buffer and an injection port, a one-way valve is provided at the injection port, and the connecting pipeline between the injection port and the barrel adopts a heating and insulation structure.

3. The process for producing an extruded polystyrene insulation board according to claim 2, wherein: The foaming agent injection system includes a supercritical CO2 injection system and a cyclopentane injection system, wherein, Supercritical CO2 injection system: After refrigeration and dehumidification, CO2 is pressurized to above the critical pressure by a high-pressure plunger pump and heated to 40-45°C in a heat exchanger. When the ambient temperature is below 20°C, the injection pressure is 18-20MPa and the flow rate is 0.8-1.0kg / h; when the ambient temperature is 20-30°C, the injection pressure is 16-18MPa and the flow rate is 0.6-0.8kg / h; when the ambient temperature is above 30°C, the injection pressure is 14-16MPa and the flow rate is 0.4-0.6kg / h. Cyclopentane injection system: Use a metering pump to accurately inject at a flow rate of 0.2-0.3kg / h and an injection pressure of 2-3MPa.

4. The process for producing an extruded polystyrene insulation board according to claim 1, wherein: The three-stage vacuum negative pressure chamber is divided into three independent chambers by two partitions. Each chamber is pumped to a negative pressure of -0.04MPa, -0.06MPa and -0.08MPa respectively by a vacuum pump. The length ratio of each chamber is 1:1.5:2, and sealing baffles are set between the chambers.

5. The process for producing extruded polystyrene insulation board according to claim 1, characterized in that: The microwave treatment was carried out in a rectangular resonant cavity using TE103 mode, and nitrogen was introduced at a rate of 2-3 L / min during the treatment.

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