Production process of extruded polyphenyl insulation board

Abstract

The invention discloses a production process of an extruded polyphenyl insulation board. Comprising the following steps that S1, polystyrene resin, gradient particle size graphene, surface modified nano silicon dioxide and a flame retardant are mixed according to the weight part ratio of 100: (1-2): (0.5-1): (3-5), the gradient particle size graphene comprises the particle size of 0.1-0.5 micron, the particle size of 1-2 microns and the particle size of 3-5 microns, mixing is conducted according to the weight ratio of 1: 2: 1, and a mixed material is obtained; s2) pretreating the mixed material for 4-6 hours at the temperature of 80-85 DEG C by adopting a mechanical shearing and ultrasonic composite dispersion device under the vacuum degree of-0.08 MPa, so as to obtain a pretreated material; a compound foaming system of gradient particle size graphene, supercritical CO2 and cyclopentane is adopted, a multi-stage heat conduction network is formed through a gradient particle size structure, the heat conduction performance of a product is effectively improved while the use amount of filler is remarkably reduced, and fluorinated graphene has a core-shell structure, so that the compatibility with a matrix is improved, and the heat conduction performance of the product is improved. And the interface bonding force is enhanced, and the problem that the mechanical property is reduced due to high filling amount is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of extruded polystyrene boards, and specifically to a production process for extruded polystyrene insulation boards. Background Art

[0002] Extruded polystyrene board (XPS) is a closed-cell foamed thermal insulation material mainly made of polystyrene resin. It is formed by heating and mixing and injecting a foaming agent, and then extruded. Due to its advantages such as low thermal conductivity, high compressive strength, and low water absorption, it is widely used in fields such as building exterior wall insulation, roof insulation, and ground insulation. At present, the production processes of XPS boards at home and abroad mainly use Freon (F142b + F22) as the foaming agent and are processed and formed by single-screw or twin-screw extruders. However, due to the relatively high ODP value of Freon, it has been listed as an environmentally unfriendly product by the United Nations and will be phased out globally.

[0003] To solve the above problems, the Chinese invention patent with the application number CN201710188788.7 discloses a production process for extruded polystyrene boards with supercritical CO 2 as the main foaming agent. It improves the problem of high thermal conductivity caused by CO 2 foaming by adding a high proportion of graphite and adopting a secondary steam foaming process. However, this solution still has the following limitations: 1) The addition of a high proportion of graphite improves the thermal conductivity, but significantly reduces the mechanical properties of the material; 2) The process of using only steam for secondary foaming has limited temperature control accuracy and is difficult to achieve precise regulation; 3) It fails to fundamentally solve the problem of uneven cell structure caused by too fast CO 2 diffusion; 4) There is a lack of precise regulation means for the internal structure of the board, which affects the stability of product performance. In addition, the conventional cooling methods in the prior art are difficult to achieve precise control, easily cause uneven distribution of internal stress in 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, which can not only solve the performance problems brought by environmentally friendly foaming agents, but also avoid the adverse effects of high proportion of fillers on mechanical properties, and at the same time have the ability to precisely regulate the foaming process, internal structure, and cooling process to ensure the comprehensive performance and process stability of the product. Summary of the Invention

[0005] The purpose of the present invention is to provide a production process for extruded polystyrene insulation boards to solve the problems existing in the existing production processes of extruded polystyrene boards as mentioned in the above background art.

[0006] To achieve the above purpose, the present invention provides the following technical solution: A production process for extruded polystyrene insulation boards, including the following steps: S1) Mix polystyrene resin, gradient particle size graphene, surface-modified nano-silica and a flame retardant in a weight ratio of 100:1 - 2:0.5 - 1:3 - 5. 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 is mixed in a weight ratio of 1:2:1 to obtain a mixed material; S2) Under a vacuum of -0.08 MPa, pretreat the mixed material at 80 - 85 °C for 4 - 6 hours using a mechanical shear and ultrasonic composite dispersion device to obtain a pretreated material; S3) Melt-extrude the pretreated material through a co-rotating twin-screw extruder. 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. 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. Inject supercritical CO 2 at a pressure of 16 - 18 MPa in the second temperature zone, and inject cyclopentane at a pressure of 2 - 3 MPa in the fourth temperature zone. The mass ratio of CO 2 to cyclopentane is 4:1 - 5:1 to obtain a foamed melt; S4) Mold the foamed melt through a special-shaped mold with a periodic microporous array. The mold is provided with three-stage vacuum negative pressure chambers along the extrusion direction. The aperture of the microporous array is 50 - 100 μm, the depth is 20 - 30 μm, and the spacing is 200 - 300 μm to obtain a primary foamed board; S5) Cool the primary foamed board successively through an atomized cooling zone and a circulating water cooling zone. The atomized cooling zone uses 5 - 10 μm water mist under 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 board; S6) After microwave treatment of the cooled board at a frequency of 2.45 GHz and a power density of 300 - 500 W / m² for 30 - 60 seconds, perform hot air circulation aging to obtain a heat-insulating board.

[0007] Preferably, the surface-modified nano-silica is modified by 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.

[0008] Preferably, the foaming agent injection system includes a supercritical CO 2 injection system and a cyclopentane injection system, where, supercritical CO 2 injection system: CO 2After being refrigerated and dehumidified, it is pressurized 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 - 20 MPa and the flow rate is 0.8 - 1.0 kg / h; when the ambient temperature is between 20 - 30°C, the injection pressure is 16 - 18 MPa and the flow rate is 0.6 - 0.8 kg / h; when the ambient temperature is above 30°C, the injection pressure is 14 - 16 MPa and the flow rate is 0.4 - 0.6 kg / h; Cyclopentane injection system: It is precisely injected at a flow rate of 0.2 - 0.3 kg / h by a metering pump, and the injection pressure is 2 - 3 MPa.

[0009] Preferably, the three-stage vacuum negative pressure chamber is separated into three independent chambers by two partition plates. Each chamber is evacuated to a negative pressure of -0.04 MPa, -0.06 MPa, and -0.08 MPa respectively by a vacuum pump. The length ratio of each chamber is 1:1.5:2, and sealing baffles are provided between the chambers.

[0010] Preferably, the gas-liquid two-phase cooling system further includes an intelligent temperature field control unit, which monitors the surface temperature distribution of the plate in real time through an infrared thermal imager. When the detected temperature non-uniformity exceeds ±2°C, the cooling parameters are automatically adjusted; the micro-channel cooling adopts a variable cross-section spiral channel design, and the cross-sectional area of the channel gradually decreases from the inlet to the outlet, with a reduction ratio of 30 - 40%.

[0011] Preferably, the microwave treatment is carried out in a rectangular resonant cavity, using the TE103 mode, and nitrogen is introduced at a flow rate of 2 - 3 L / min during the treatment process.

[0012] Preferably, the gradient particle size graphene is surface fluorinated with a fluorination degree of 10 - 15%, has a core-shell structure, and the shell layer thickness is 2 - 5 nm.

[0013] Preferably, independent foaming agent injection systems are respectively arranged in the second temperature zone and the fourth temperature zone of the parallel co-rotating twin-screw extruder. 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 heat tracing and insulation structure.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1) This application adopts a compound foaming system of gradient particle size graphene, supercritical CO 2 and cyclopentane. A multi-level heat conduction network is formed through the gradient particle size structure, effectively improving the thermal conductivity of the product while significantly reducing the filler dosage. Among them, the fluorinated graphene has a core-shell structure, which not only improves the compatibility with the matrix but also enhances the interfacial bonding force, avoiding the problem of mechanical property degradation caused by high filler content; 2) This application innovatively designs a three - stage vacuum negative pressure forming system and a gas - liquid two - phase cooling system with intelligent temperature field control. By gradually increasing the negative pressure along the extrusion direction and cooperating with a micro - hole array die, precise control of the foaming process is achieved. At the same time, a cooling method combining infrared thermal imaging monitoring and intelligent feedback control is adopted to ensure the uniformity of the sheet cooling process and effectively avoid internal stress concentration. 3) This application separately sets up independent blowing agent injection systems in the second temperature zone and the fourth temperature zone, and adopts a heat - tracing and heat - preservation structure. By reasonably controlling the injection pressure and temperature, premature decomposition of the blowing agent is effectively prevented. In addition, the design of automatically adjusting the blowing agent injection parameters according to the ambient temperature significantly improves the adaptability and stability of the process. 4) This application adopts a post - treatment process combining microwave treatment and hot - air circulation aging. Through precise control of the electric field distribution in the TE103 mode, further optimization of the internal structure of the sheet is achieved, improving the dimensional stability and long - term service performance of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the process flow chart of this application; Figure 2 is the detailed process flow chart of this application; Figure 3 is the schematic diagram of the holes in the mold vacuum negative pressure chamber of this application; Figure 4 is the schematic diagram of the micro - holes in the mold of this application; Figure 5 is the schematic diagram of the co - rotating twin - screw extruder of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0017] In the description of the invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "front end", "rear end", "both ends", "one end", "the other end", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0018] In the description of the invention, it should be noted that unless otherwise clearly specified and defined, terms such as "installed", "equipped with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0019] In the description of the invention, it should be noted that the execution order of steps is not limited by the serial numbers, and changes in the order of some steps, synchronous execution of steps, split execution of steps, etc. are all within the protection scope of this application.

[0020] Please refer to Figures 1-5 , the present invention provides a technical solution: a production process of extruded polystyrene insulation board, including the following steps: S1) Mix 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. 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 is mixed in a weight ratio of 1:2:1 to obtain a mixed material; S2) Pretreat the mixed material at a vacuum degree of -0.08 MPa for 4-6 hours at 80-85 °C using a mechanical shear and ultrasonic composite dispersion device to obtain a pretreated material; S3) Melt-extrude the pretreated material through a parallel co-rotating twin-screw extruder. 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. 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. Inject supercritical CO 2 , inject cyclopentane into the fourth temperature zone at a pressure of 2-3 MPa. The mass ratio of CO 2 to cyclopentane is 4:1-5:1 to obtain a foamed melt; S4) Mold the foamed melt through a special-shaped mold with a periodic microporous array. The mold is provided with three-stage vacuum negative pressure chambers along the extrusion direction. The aperture of the microporous array is 50-100 μm, the depth is 20-30 μm, and the spacing is 200-300 μm to obtain a primary foamed board; S5) Cool the primary foamed board successively through an atomized cooling zone and a circulating water cooling zone. The atomized cooling zone uses 5-10 μm water mist under 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 board; S6) After subjecting the cooled sheet material to microwave treatment at a frequency of 2.45 GHz and a power density of 300 - 500 W / m² for 30 - 60 seconds, hot air circulation aging is carried out to obtain the insulation board.

[0021] Specifically, this application uses gradient particle size graphene to replace traditional graphite fillers. Through a gradient structure of three specifications: 0.1 - 0.5 μm, 1 - 2 μm, and 3 - 5 μm, a multi-scale heat conduction network is formed. Graphene of different sizes forms interconnected channels in the matrix. Large-sized graphene provides the main heat conduction path, medium-sized graphene fills the connection gaps, and micron-sized particles fill the fine voids. This multi-level cooperation significantly improves the heat conduction efficiency. At the same time, since the total filling amount is only 1 - 2 parts (relative to 100 parts of polystyrene resin), which is much lower than the addition amount in the prior art, it effectively avoids the problem of mechanical property degradation caused by high filling. In addition, the process adopts a synergistic foaming system of high-pressure CO 2 and cyclopentane. By injecting in different temperature zones in sections, it not only ensures environmental protection but also overcomes the defect of too fast diffusion of a single CO 2 foaming agent.

[0022] Refer to the attached Figure 1 to the specification. The steps S1 - S6 are respectively raw material premixing, pretreatment, twin-screw extrusion, die forming, cooling treatment, and microwave treatment.

[0023] Example 1 S1) Mix 100 parts of polystyrene resin, 1.5 parts of gradient particle size graphene (graphene with particle sizes of 0.1 - 0.5 μm, 1 - 2 μm, and 3 - 5 μm are mixed in a weight ratio of 1:2:1), 0.8 parts of KH550-modified nano-silica (specific surface area 200 m² / g, surface grafting rate 18%, surface loading of 0.8 wt% silver nanoparticles), and 4 parts of flame retardant to obtain a mixed material; S2) Under a vacuum of -0.08 MPa, use a mechanical shear and ultrasonic composite dispersion device to pretreat the mixed material at 82°C for 5 hours to obtain a pretreated material; S3) Melt-extrude the pretreated material through a parallel co-rotating twin-screw extruder. The temperatures of each temperature zone of the extruder are respectively: the first temperature zone is 140°C, the second temperature zone is 145°C, the third temperature zone is 150°C, the fourth temperature zone is 148°C, the fifth temperature zone is 145°C. Inject supercritical CO 2 at a pressure of 17 MPa in the second temperature zone, inject cyclopentane at a pressure of 2.5 MPa in the fourth temperature zone. The mass ratio of CO 2 to cyclopentane is 4.5:1 to obtain a foamed melt; S4) The foaming melt is formed through a profiled die with a periodic micropore array. The pressures of the three-stage vacuum negative pressure chambers set along the extrusion direction of the die are -0.04 MPa, -0.06 MPa, and -0.08 MPa respectively. The pore diameter of the micropore array is 75 μm, the depth is 25 μm, and the spacing is 250 μm, obtaining a primary foamed sheet; S5) The primary foamed sheet is cooled successively through an atomization cooling zone and a circulating water cooling zone. The atomization cooling zone uses 8-μm water mist under a pressure of 1.0 MPa, and the water temperature in the circulating water cooling zone is 18 °C, obtaining a cooled sheet; S6) After the cooled sheet is treated with microwaves at a frequency of 2.45 GHz and a power density of 400 W / m² for 45 seconds, hot air circulation aging is carried out to obtain a heat-insulating board.

[0024] The heat-insulating board prepared in Example 1 is tested, and the test results are as follows: Thermal conductivity: 0.028 W / (m·K); Compressive strength: 320 kPa; Closed cell ratio: 98.5%; Dimensional stability: 0.6%; Filler dispersibility: coefficient of variation 2.3%; Average cell diameter: 180 μm; Standard deviation of cell diameter: ±15 μm.

[0025] The heat-insulating board prepared in Example 1 is tested, and the physical and chemical index data obtained are as follows: Table 1 Physical and Chemical Indexes of Example 1 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 Rate: 5mm / min, Test Sample Size: 100×100×30mm 320 kPa Closed Cell Ratio 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 the thermal conductivity at 9 different positions of the sample and calculate the coefficient of variation Coefficient of Variation 2.3% Average Cell Diameter Indirect Determination Method for Water Absorption Measure the water absorption after the sample is immersed in water for 48h and calculate in combination with the density 180±15μm Thus, in Example 1, through the synergistic effect of gradient particle size graphene, surface-modified nano-silica, and fluorination treatment, an optimal performance combination is achieved. In particular, the thermal conductivity reaches 0.028 W / (m·K), while maintaining a high compressive strength of 320 kPa. The high dispersibility of the filler and the uniform cell structure prove the rationality of the process parameters. The closed cell ratio of 98.5% and the dimensional stability of 0.6% indicate that the product has excellent heat-insulating performance and service stability.

[0026] Specifically, in a closed-cell extruded polystyrene board, water absorption mainly occurs in the open cells on the material surface and the cut surface. The water absorption rate is closely related to the cell structure (including cell diameter, distribution, and connectivity). The method for indirectly calculating the cell diameter based on the water absorption rate, density, and theoretical calculation formula of the sample is as follows: Calculation formula:

[0027] Where: d is the average cell diameter (μm); V p is the total volume of the sample (mm³); P is the porosity (which can be calculated from the density); S is the surface area of the pores per unit volume (which can be indirectly calculated through the water absorption rate); Porosity calculation:

[0028] Where: P is the porosity; ρ a is the apparent density of the sample (g / cm³); ρ t is the theoretical density of polystyrene (g / cm³), approximately 1.05 g / cm³; Calculation of the surface area of the pores per unit volume:

[0029] Where: S is the total surface area of the pores per unit volume (mm² / mm³); W w is the water absorption rate of the sample (expressed as a decimal, e.g., 0.92% should be 0.0092); ρ a is the apparent density of the sample (g / cm³); h is the density of water (g / cm³), which is 1 g / cm³; σ is the surface tension coefficient of water (N / m); t is the test time (h); Take the sample in Example 1 and measure the following data: Apparent density (ρ a ): 0.035 g / cm³; Water absorption rate (W w ): 0.92% (48-hour immersion test); Sample volume (V p ): 10 cm³; Calculation steps: 1. Calculate the porosity: P = 1 - (0.035 / 1.05) = 0.967 (96.7%) 2. Calculate the surface area of the pores per unit volume: Assume the surface tension coefficient of water σ = 72.8 mN / m, the density of water h = 1 g / cm³, and the test time t = 48 h S = (0.92% × 0.035) / (1 × 72.8 × 10 - ³ × 48) = 9.25 × 10 -6 cm² / cm³; 3. Calculate the average cell diameter: d = √[6 × 10 × (1 - 0.967) / (9.25 × 10 -6 × 0.967)] d = 4,528 μm; 4. Application of correction factor: In the extruded polystyrene board, the empirical correction factor is about 0.04.

[0030] d 校正 = 4,528 × 0.04 = 181 μm.

[0031] The average cell diameter of the samples in the following examples and comparative examples can be calculated in this way.

[0032] Example 2: S1) Mix 100 parts of polystyrene resin, 1.2 parts of gradient particle size graphene (other ratios are the same as in Example 1), 0.6 parts of nano-silica modified by KH550 (other parameters are the same as in Example 1), and 4 parts of flame retardant to obtain a mixed material; Steps S2 - S6 are the same as in Example 1.

[0033] Detect the insulation board prepared in Example 2, and the test results are as follows: Thermal conductivity: 0.029 W / (m·K); Compressive strength: 305 kPa; Closed cell rate: 98.0%; Dimensional stability: 0.7%; Dispersibility of filler: Coefficient of variation 3.1%; Average cell diameter: 185 μm; Standard deviation of cell diameter: ±18 μm.

[0034] Detect the insulation board prepared in Example 2, and the physical and chemical index data are as follows: Table 2 Physical and Chemical Indexes of Example 2 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 Ratio 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 Method for Water Absorption Same as Example 1 185±18μm Thus, in Example 2, although the dosages of gradient particle size graphene and modified nano-silica are reduced, good comprehensive performance is still maintained. The thermal conductivity (0.029 W / (m·K)) and compressive strength (305 kPa) are slightly lower than those in Example 1, and the process of the present invention has a large operation window and can adapt to different formulation requirements.

[0035] Comparative Example 1: Compared with Example 1, instead of using gradient particle size graphene, ordinary graphite powder is used, and other conditions are the same.

[0036] S1: Mix 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 same as in Example 1), and 4 parts of flame retardant to obtain a mixed material; Steps S2 - S6 are the same as in Example 1.

[0037] Test the insulation board prepared in Comparative Example 1, and the test results are as follows: Thermal conductivity: 0.032 W / (m·K); Compressive strength: 280 kPa; Closed cell ratio: 97.0%; Dimensional stability: 1.2%; Dispersibility of filler: Coefficient of variation 9.5%; Average cell diameter: 200 μm; Standard deviation of cell diameter: ±35 μm.

[0038] Test the insulation board prepared in Comparative Example 1, and the physical and chemical index data are as follows: Table 3 Physical and Chemical Indexes of Comparative Example 1 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 Ratio 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 Method for Water Absorption Same as Example 1 200±35μm It can be seen from the comparison between Comparative Example 1 and Example 1 that after using gradient particle size graphene to replace ordinary graphite powder: 1) The thermal conductivity is significantly reduced, from 0.032 to 0.028 W / (m·K); 2) The compressive strength is increased by about 14.3%; 3) The dispersibility of the filler is greatly improved, and the agglomeration phenomenon is significantly reduced; 4) The cell structure is more uniform, and the standard deviation of the diameter is reduced by 57%.

[0039] Therefore, in Comparative Example 1, using ordinary graphite powder to replace gradient particle size graphene results in a significant decline in performance. The relatively high thermal conductivity (0.032 W / (m·K)) and the large coefficient of variation indicate that the gradient particle size design is crucial for improving the thermal conductivity and dispersibility. The relatively large standard deviation of the cell diameter (±35 μm) shows that the graphite powder affects the foaming uniformity.

[0040] The surface-modified nano-silica is modified by KH550, with a specific surface area of 180 - 220 m² / g, a surface grafting rate of 15 - 20%, and 0.5 - 1 wt% of silver nanoparticles are loaded on the surface. Specifically, due to the good compatibility between the amino group in the KH550 molecule and the polystyrene matrix, the high specific surface area provides sufficient nucleation sites, and the control of the surface grafting rate ensures the modification effect without overly affecting the dispersibility. In addition, after loading 0.5 - 1 wt% of silver nanoparticles on the surface, the silver nanoparticles not only provide additional heat conduction channels but also have a synergistic nucleation effect, capable of providing more uniform bubble nucleation points.

[0041] Comparative Example 2: Compared with Example 1, ordinary nano-silica without KH550 modification is used, and other conditions are the same.

[0042] S1: Mix 100 parts of polystyrene resin, 1.5 parts of gradient particle size graphene (the same ratio 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 to obtain a mixed material; Steps S2 - S6 are the same as in Example 1.

[0043] The insulation board prepared in Comparative Example 2 is tested, and the test results are as follows: Thermal conductivity: 0.031 W / (m·K); Compressive strength: 290 kPa; Closed cell rate: 97.5%; Dimensional stability: 1.0%; Filler dispersibility: Coefficient of variation 7.2%; Average bubble diameter: 195 μm; Standard deviation of bubble diameter: ±28 μm.

[0044] The insulation board prepared in Comparative Example 2 is tested, and the physical and chemical index data are as follows: Table 4 Physical and Chemical Indexes of Comparative Example 2 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 Ratio 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 Method for Water Absorption Same as Example 1 195±28μm It can be seen from the comparison between Comparative Example 2 and Example 1 that after using nano-silica modified by KH550: 1) The filler dispersibility is significantly improved; 2) The thermal conductivity is reduced by about 9.7%; 3) The bubble structure is more uniform, and the standard deviation of the diameter is reduced by 46%; 4) The mechanical properties are improved by about 10.3%.

[0045] Therefore, in Comparative Example 2, the nano-silica without KH550 modification led to poor filler dispersion, which in turn affected the thermal conductivity (0.031 W / (m·K)) and mechanical properties (290 kPa), verifying the importance of surface modification in improving the compatibility between the filler and the matrix.

[0046] The foaming agent injection system includes a supercritical CO 2 injection system and a cyclopentane injection system. Among them, Supercritical CO 2 Injection system: After being refrigerated and dehumidified, CO 2 is pressurized to above the critical pressure by a high-pressure piston pump and heated to 40 - 45 °C in a heat exchanger. When the ambient temperature is below 20 °C, the injection pressure is 18 - 20 MPa and the flow rate is 0.8 - 1.0 kg / h; when the ambient temperature is between 20 - 30 °C, the injection pressure is 16 - 18 MPa and the flow rate is 0.6 - 0.8 kg / h; when the ambient temperature is above 30 °C, the injection pressure is 14 - 16 MPa and the flow rate is 0.4 - 0.6 kg / h; Cyclopentane injection system: It is accurately injected at a flow rate of 0.2 - 0.3 kg / h by a metering pump, and the injection pressure is 2 - 3 MPa.

[0047] Specifically, in the foaming agent injection system, the lower the temperature, the higher the injection pressure and flow rate are adopted. This is because the ambient temperature affects the heat transfer conditions of the barrel and the mold, and thus affects the decomposition kinetic process of the foaming agent. For example, in a low-temperature environment (<20 °C), a high pressure of 18 - 20 MPa and a large flow rate of 0.8 - 1.0 kg / h can compensate for the insufficient foaming caused by the temperature reduction; while in a high-temperature environment, the parameters are correspondingly reduced to avoid over-foaming. This adaptive control scheme significantly improves the process adaptability and the stability of product quality.

[0048] Refer to the attached Figure 3 specification. The three-stage vacuum negative pressure chamber is separated into three independent chambers by two partitions. Each chamber is evacuated to a negative pressure of -0.04 MPa, -0.06 MPa, and -0.08 MPa respectively by a vacuum pump. The length ratio of each chamber is 1:1.5:2, and sealing baffles are arranged between the chambers. Specifically, the traditional process usually adopts a single negative pressure or a simple two-stage negative pressure, which is difficult to precisely control the foaming process. In this application, the mold is separated into three independent chambers by two partitions, and a progressive negative pressure of -0.04 MPa, -0.06 MPa, and -0.08 MPa is adopted, which matches the length ratio of 1:1.5:2 to form a pressure gradient field along the product forming direction.

[0049] Specifically, the low negative pressure (-0.04 MPa) in the first chamber mainly controls the initial foaming, initially reduces the melt pressure, guides the slow nucleation of bubbles, and avoids the coalescence of pores, thereby preventing the pore rupture caused by violent foaming; the medium negative pressure (-0.06 MPa) in the second chamber promotes the growth of pores, further releases the pressure, and promotes the uniform expansion of bubbles; the high negative pressure (-0.08 MPa) in the third chamber is used for the final shaping of pores, finally stabilizes the pore structure, discharges the residual gas, and ensures a smooth surface. This progressive negative pressure control realizes the precise regulation of the foaming process and obtains a more uniform pore structure.

[0050] Refer to the attached instruction manual Figure 3 , the three-stage vacuum negative pressure chamber is directly integrated inside the mold and arranged in sequence along the flow direction of the extruded foamed melt (i.e., the length direction of the mold). The first chamber is set at the near inlet end, the second chamber is set in the middle section, and the third chamber is set at the near outlet end. Each chamber is connected to the mold forming cavity. The partition can be made of high-temperature resistant rubber or metal materials to ensure the sealing between chambers and at the same time allow the melt to pass continuously. The three-stage vacuum chamber is also the pre-treatment area of the mold forming cavity, responsible for the pre-forming and gas management of the foamed melt. After the vacuum chamber optimizes the pore structure through gradient negative pressure, the melt enters the forming cavity to complete the shaping. The chamber length ratio (1:1.5:2) is designed to match the kinetic requirements of melt foaming. The short front section can quickly reduce the pressure, and the long rear section can achieve fine regulation.

[0051] Refer to the attached instruction manual Figure 4 , through the periodic microporous array (pore diameter 50 - 100 μm) on the mold surface, the volatile gases (such as residual CO 2 , cyclopentane) generated during the foaming process are evacuated to prevent bubble rupture or surface defects. The microporous array on the surface of the forming cavity cooperates with the vacuum system to ensure the efficient discharge of gas and at the same time avoid the blockage of micropores by the melt. The gradient negative pressure avoids the sudden expansion or collapse of bubbles, and the standard deviation of the pore diameter distribution is reduced by 30% - 40%. The microporous array combined with a high vacuum degree (-0.08 MPa) can eliminate surface air marks, and the roughness (Ra) ≤ 5 μm. And the staged vacuum extraction reduces the local pressure overload, and the mold life is extended by 20% - 30%.

[0052] The gas-liquid two-phase cooling system also includes an intelligent temperature field control unit, which monitors the surface temperature distribution of the sheet in real time through an infrared thermal imager. When the detected temperature non-uniformity exceeds ±2 °C, the cooling parameters are automatically adjusted; the micro-channel cooling adopts a variable cross-section spiral channel design, and the cross-sectional area of the channel gradually decreases from the inlet to the outlet, with a reduction ratio of 30-40%. Specifically, this application combines the infrared thermal imaging monitoring technology with an automatic adjustment system. In the prior art, the cooling process often uses empirical control and it is difficult to achieve real-time adjustment. In this application, the surface temperature distribution of the sheet is monitored in real time through an infrared thermal imager. When the detected temperature non-uniformity exceeds ±2 °C, the system can automatically adjust the cooling parameters, and this closed-loop control ensures the uniformity of the cooling process. Especially the design of the variable cross-section spiral channel, through the gradual change of the cross-sectional area along the flow direction (reduction ratio 30-40%), while maintaining the stable flow velocity of the cooling water, compensates for the pressure loss along the way and achieves a more uniform cooling effect.

[0053] Specifically, the gas-liquid two-phase cooling system is located in the cooling section after the outlet of the extruder and the forming die. The first stage (gas phase) is an atomization cooling device. Multiple atomization nozzles are arranged on the upper part of the atomization cooling device, facing the surface of the sheet at an angle of 45°. A ventilation system can be arranged at the lower part of the atomization cooling device to collect the cooling water mist. The second stage (liquid phase) is a water cooling device. There are two water cooling plates, the upper and the lower, of the water cooling device. A variable cross-section spiral channel is arranged inside the water cooling plate. The cross-sectional area of the starting end of the variable cross-section spiral channel is larger, and the cross-sectional area of the terminal end is smaller, and the variable cross-section spiral channel is arranged spirally along the running direction of the sheet. 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 installed above the cooling section, and the control unit is used to connect the infrared thermal imager and the cooling system. When the automatic adjustment mechanism operates, when the detected temperature is uneven, the nozzle pressure and the water flow velocity are adjusted. The automatic adjustment mechanism performs real-time feedback control to ensure the cooling uniformity. The variable cross-section spiral channel cooling structure is already in the prior art and will not be elaborated here.

[0054] The microwave treatment is carried out in a rectangular resonant cavity, adopting the TE103 mode, that is, an electromagnetic field distribution mode with one half-wave in the width direction of the cavity and three half-waves in the length direction. During the treatment process, nitrogen is introduced at a rate of 2-3 L / min. Specifically, the TE103 mode specifically refers to an electromagnetic field distribution mode with one half-wave in the width direction of the cavity and three half-waves in the length direction. This specific mode can form a uniform electric field distribution in the sheet, avoiding the "hot spot" problem in conventional microwave treatment. The design of introducing 2-3 L / min of nitrogen also has a dual effect: it not only prevents the oxidation of the sheet at high temperatures but also assists in the uniformity of the temperature field through convective heat transfer.

[0055] Specifically, the rectangular resonant cavity structure is arranged after the cooling section. The rectangular resonant cavity is a rectangular cavity adapted to the width of the plate. When the rectangular resonant cavity is in use, a specific electromagnetic field distribution is generated in the TE103 mode. The plate passes through the center position of the cavity, and the microwave energy acts on the plate evenly. The nitrogen protection system can set air curtains at both ends of the cavity to prevent the oxidation of the plate.

[0056] The gradient particle size graphene is surface fluorinated with a fluorination degree of 10 - 15% and has a core-shell structure with a shell layer thickness of 2 - 5 nm. Specifically, within the fluorination degree range of 10 - 15%, the fluorinated graphene not only maintains good thermal conductivity but also significantly improves its interfacial compatibility with the polystyrene matrix. The design of the 2 - 5 nm shell layer thickness is based on the following mechanism: an overly thin shell layer cannot provide sufficient interfacial regulation effect, while an overly thick one will affect the thermal conductivity. The design of this core-shell structure realizes the dual functions of "thermal conductivity enhancement" and "interfacial compatibility", overcoming the problems of filler agglomeration and poor interfacial bonding in the prior art.

[0057] Comparative Example 3: Compared with Example 1, gradient particle size graphene without fluorination treatment is used, and other conditions are the same.

[0058] Description of the fluorination treatment process: Graphene is dispersed in a hydrofluoric acid solution with a concentration of 40 wt%, reacted at 60 °C for 4 hours, filtered by suction, washed with water until neutral, and dried in vacuum at 80 °C for 12 hours to obtain fluorinated graphene with a fluorination degree of 12%, forming a fluorinated layer of 2 - 5 nm.

[0059] S1: Mix 100 parts of polystyrene resin, 1.5 parts of gradient particle size graphene without fluorination treatment (the same ratio 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 to obtain a mixed material; Steps S2 - S6 are the same as in Example 1.

[0060] The insulation board prepared in Comparative Example 3 is tested, and the test results are as follows: Thermal conductivity: 0.030 W / (m·K); Compressive strength: 295 kPa; Closed cell rate: 97.8%; Dimensional stability: 0.9%; Filler dispersibility: coefficient of variation 6.2%; Average cell diameter: 190 μm; Standard deviation of cell diameter: ±25 μm.

[0061] The insulation board prepared in Comparative Example 3 is tested, and the physical and chemical index data are as follows: Table 5 Physical and Chemical Indexes of Comparative Example 3 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 ratio GB / T 30595-2014 Same as Example 1 97.8% Dimensional stability GB / T 8811-2008 Same as Example 1 0.9% Dispersion of filler Test for thermal conductivity uniformity Same as Example 1 Coefficient of variation 6.2% Average cell diameter Indirect determination method for water absorption Same as Example 1 190±25μm From the comparison between Comparative Example 3 and Example 1, it can be seen that for the gradient particle size graphene treated by fluorination: 1) The filler dispersibility is improved; 2) The thermal conductivity is reduced by about 6.7%; 3) The compressive strength is increased by about 8.5%; 4) The cell structure is more uniform, and the standard deviation of the diameter is reduced by 40%.

[0062] Therefore, in Comparative Example 3, although the gradient particle size graphene without fluorination treatment is better than ordinary graphite powder, its performance is inferior to that of Example 1. The poor dispersibility (variation coefficient of 6.2%) and low mechanical properties (295 kPa) indicate that fluorination treatment plays an important role in improving the interfacial bonding strength.

[0063] As an additional note, in the physical and chemical index tests of any of the foregoing examples / comparative examples: 1) Thermal conductivity test: It reflects the ability of the material to conduct heat. The lower the value, the better the heat insulation effect. The thermal conductivity of Example 1 reaches 0.028 W / (m·K), which is better than the prior art; 2) Compressive strength test: It characterizes the ability of the material to withstand pressure. The higher the value, the better the mechanical properties. The 320 kPa of Example 1 indicates that the mechanical properties are not lost while improving the thermal conductivity; 3) Closed cell rate test: It reflects the degree of closure of the foaming structure and affects the heat insulation performance and water absorption. The high closed cell rate of 98.5% indicates an excellent foaming process; 4) Dimensional stability test: It characterizes the degree of deformation of the material at high temperature. The smaller the value, the more stable. The low deformation rate of 0.6% indicates good stability in product use; 5) Thermal conductivity uniformity test: By measuring the thermal conductivity at 9 different positions (the center point and 8 evenly distributed points around) of the sample, and then calculating the variation coefficient. The smaller the variation coefficient, the more uniform the filler dispersion. The calculation formula for the variation coefficient (CV): CV = (standard deviation / average value) × 100%; 6) Cell size test: It reflects the uniformity of the foaming structure. The apparent density of the sample is measured using Archimedes' principle, the true density of the material is measured using a pycnometer, the porosity is calculated, and then combined with the known total pore volume and quantity relationship, the average cell diameter can be deduced. The smaller the standard deviation, the more uniform the structure and the more stable the performance.

[0064] As an additional note, in the physical and chemical index tests of any of the foregoing examples / comparative examples: 1) Thermal conductivity: Measured using a thermal conductivity tester according to the standard of GB / T 10294-2008, with the test temperature of 25°C; 2) Compressive strength: Measured using a universal testing machine according to the standard of GB / T 8813-2008; 3) Closed cell ratio: Measured according to the standard of GB / T 30595-2014; 4) Dimensional stability: Measuring the dimensional change rate under the condition of 70°C for 48h according to the standard of GB / T 8811-2008; 5) Filler dispersion: Measuring the thermal conductivity at 9 different positions of the sample and calculating the coefficient of variation; 6) Average cell diameter: Measuring the water absorption rate after the sample is immersed in water for 48h and calculating in combination with the density.

[0065] As an additional note, in the physical and chemical index tests of any of the foregoing examples / comparative examples: 1) All tests are carried out under standard laboratory conditions (temperature 23±2°C, relative humidity 50±5%); 2) Each set of data is the average value of 5 test samples.

[0066] Thus, it can be seen from the test results of the foregoing examples / comparative examples: Both Example 1 and Example 2 show 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 dispersion is the most uniform; 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 filler dispersion, and the necessity of gradient particle size graphene, surface modification and fluorination treatment; The present invention not only significantly improves the thermal conductivity of the product, but also maintains high mechanical properties, realizing the overall improvement of performance.

[0067] Independent foaming agent injection systems are respectively arranged in the second temperature zone and the fourth temperature zone of the parallel co-rotating twin-screw extruder. Each injection system includes: a storage tank, a booster pump, a metering pump, a buffer and an injection port. A check valve is arranged at the injection port, and the connecting pipeline between the injection port and the barrel adopts a heat tracing and insulation structure.

[0068] Specifically, the foaming agent injection system of the present application is completely different from the simple injection method in the prior art. The storage tank, booster pump, metering pump, buffer and injection port included in each injection system form a complete precise control system. The check valve at the injection port prevents the material from flowing back. Especially, the heat tracing and insulation structure of the connecting pipeline effectively prevents the premature decomposition of the foaming agent during the transportation process by precisely controlling the temperature. This systematic design fundamentally solves various problems in the transportation and injection links of the foaming agent in the prior art, and significantly improves the controllability of the process and the stability of the product quality.

[0069] Specifically, the foaming agent injection system is arranged on the twin-screw extruder, and the second temperature zone injection system (CO 2 ) where the storage tank is used for storing liquid CO 2 . The booster pump pressurizes the CO 2 to the supercritical state. The metering pump can precisely control the injection volume, the buffer can balance the pressure fluctuations, and the injection port is a special injection device with a one-way valve. The structure of the fourth temperature zone injection system (cyclopentane) is the same as that of the second temperature zone injection system, but the pressure requirement is lower, and the sealing and heat preservation designs are particularly strengthened.

[0070] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope 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-silicon dioxide and flame retardant are mixed 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; S2) pretreating the mixed material at -0.08 MPa vacuum by using a mechanical shearing and ultrasonic composite dispersion device at 80-85° C. for 4-6 hours to obtain a pretreated material; S3) melt-extrude 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 16-18MPa, and cyclopentane is injected into the fourth temperature zone at a pressure of 2-3MPa, and the mass ratio of CO2 to 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 through an atomizing cooling zone and a circulating water cooling zone in sequence, 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 microwave treatment at a frequency of 2.45 GHz and a power density of 300-500 W / m² for 30-60 seconds, and then subjected to hot air circulation aging to obtain a heat-insulating plate.

2. The process for producing an extruded polystyrene insulation board according to claim 1, characterized in that: The surface-modified nano-silicon dioxide is modified by KH550, has a specific surface area of ​​180-220 m2 / g, a surface grafting rate of 15-20%, and a surface loading of 0.5-1wt% of silver nanoparticles.

3. The process for producing an extruded polystyrene insulation board according to claim 1, characterized in that: 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 lower than 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 higher than 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, characterized in that: 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 sealing baffles are arranged between the chambers.

5. The process for producing an extruded polystyrene insulation board according to claim 1, characterized in that: 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 is detected 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%.

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

7. The process for producing an extruded polystyrene insulation board according to claim 1, characterized in that: The gradient particle size graphene is subjected to surface fluorination treatment, the fluorination degree is 10-15%, has a core-shell structure, and the shell thickness is 2-5nm.

8. The process for producing an 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 comprises: a storage tank, a booster pump, a metering pump, a buffer and an injection port, a one-way valve is arranged at the injection port, and the connecting pipeline between the injection port and the barrel adopts a heating and insulation structure.

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