A high temperature resistant insulation board and preparation method thereof

Abstract

The present application relates to the technical field of thermal insulation boards, and specifically discloses a high-temperature resistant thermal insulation board and a preparation method thereof. A high-temperature resistant thermal insulation board comprises the following substances in parts by weight: polystyrene 75‑90wt%; reinforcing material 5‑10wt%; nucleating agent 0.5‑3wt%; flame retardant 1‑5wt%; foaming agent 5‑10wt%; the reinforcing material comprises any one or more of polyamide 6, ABS, and PC, and the reinforcing material also comprises magnetic expanded graphite. The preparation method thereof is as follows: S1, raw material preparation; S2, thermal insulation board preparation. The thermal insulation board of the present application can be used in high-temperature occasions such as drying rooms and ovens, and has the advantages of high flame retardancy and high-temperature stability.

Description

Technical Field

[0001] The present application relates to the technical field of thermal insulation boards, and more specifically, to a high temperature resistant thermal insulation board and a preparation method thereof. Background Art

[0002] Extruded polystyrene (XPS) foam refers to a foam material made from general-grade polystyrene using a continuous extrusion foaming method. Due to its excellent thermal insulation performance, moisture resistance, high compressive strength, chemical corrosion resistance, and easy processing, it is widely used in transportation, refrigeration, construction, interior decoration and other fields.

[0003] General-grade polystyrene itself has a low glass transition temperature and poor high-temperature resistance. Generally, it will deform slightly and become sticky at around 100°C. When it comes into contact with a high-temperature medium above 100°C, it is easy to leave marks on the surface. At present, foaming materials are usually prepared by adding some high-temperature resistant materials for blending to improve the high-temperature resistance of the material. However, since the raw material components are prepared by blending and then extrusion molding, a large portion of polystyrene with low high-temperature resistance will exist on the surface of the foaming material. As the temperature is further increased (such as 165°C) or the time is further extended (such as 150°C / 6h), the surface of the composite material will shrink or crack. Therefore, it is urgent to obtain a stable high-temperature resistant thermal insulation material. Summary of the invention

[0004] In order to improve the high temperature stability of the insulation board, the present application provides a high temperature resistant insulation board and a preparation method thereof, adopting the following technical solutions:

[0005] In a first aspect, the present application provides a high temperature resistant insulation board, comprising the following materials in parts by weight:

[0006] Polystyrene 75-90wt%;

[0007] Reinforcement material 5-10wt%;

[0008] Nucleating agent 0.5-3wt%;

[0009] Flame retardant 1-5wt%;

[0010] Foaming agent 5-10wt%;

[0011] The reinforcing material includes any one or more of polyamide 6, ABS, and PC, and the reinforcing material also includes magnetic expanded graphite, and the magnetic expanded graphite is distributed on the surface of the high temperature resistant insulation board.

[0012] By adopting the above technical solution and adding reinforcing materials, the melt strength of the PS matrix can be made higher, which is more conducive to forming a stable pore structure during the pore growth process in the composite insulation board, and enables the composite insulation board to obtain excellent compressive strength and heat deformation temperature.

[0013] Polyamide 6 can significantly enhance the compressive strength of XPS while maintaining the thermal conductivity coefficient unchanged, while improving the side compressive strength. And as the amount of PA6 increases, the compressive strength of the front and side also increases. The introduction of reinforcing materials can also increase the thermal deformation temperature of XPS and increase its use temperature range. Therefore, the introduction of reinforcing materials such as PA6 can significantly increase the mechanical properties of XPS.

[0014] The introduction of magnetic expanded graphite, which has a rich interlayer structure, can effectively play a role in thermal insulation in thermal insulation materials. Expanded graphite has better high temperature resistance, which improves the high temperature resistance of the thermal insulation board and makes the thermal insulation board have excellent flame retardant effect. Since magnetic expanded graphite can be attracted by magnetism, it can be dispersed on the surface of the thermal insulation board by using an external magnetic field during the preparation of the thermal insulation board, reducing the content of polystyrene on the surface of the thermal insulation board, making the expanded graphite stable as a shielding layer of the thermal insulation board, and thus reducing the possibility of cracking on the surface of the thermal insulation board.

[0015] Optionally, the magnetic expanded graphite is prepared as follows: a magnetic body is mixed with a citric acid solution, the pH is adjusted to obtain a magnetic solution, and the expanded graphite is immersed in the magnetic solution, stirred, and baked to obtain the magnetic expanded graphite.

[0016] By adopting the above technical solution, magnetic particles are loaded in expanded graphite by impregnation method, so that the expanded graphite has magnetism and can be dispersed to the surface of the insulation board under the influence of an external magnetic field, thereby improving the possibility of surface cracking of the insulation board at high temperature.

[0017] Optionally, the reinforcing material further includes fiber fillers, and the fiber fillers include carbon fibers and mullite fibers.

[0018] By adopting the above technical scheme, carbon fiber, silicon carbide fiber and mullite fiber all have relatively excellent high temperature resistance. When added to the insulation board, a staggered fiber structure can be introduced into the insulation board, that is, a three-dimensional skeleton structure is introduced into the insulation board, which is beneficial to improve the mechanical strength of the insulation board.

[0019] Optionally, the fiber filler is pre-mixed with the magnetic expanded graphite.

[0020] By adopting the above technical solution, since the fiber filler is pre-mixed with the magnetic expanded graphite, and since the magnetic expanded graphite has more interlayer gaps, after pre-mixing, part of the fiber filler can be inserted into the interlayer of the magnetic expanded graphite, so as to realize the combination of the fiber and the magnetic expanded graphite, and then the magnetic expanded graphite can synchronously drive the fiber filler to move together under the drive of the external electric field, so that the magnetic expanded graphite is connected with the fiber skeleton in the insulation board, and the magnetic expanded graphite can be supported by the fiber skeleton structure, so that the surface of the insulation board has less polystyrene and can maintain a relatively complete surface structure. In addition, part of the fiber filler can be driven to the surface of the insulation board, increasing the density of the shielding layer on the surface of the insulation board, further reducing the content of polystyrene on the surface of the insulation board, and reducing the possibility of cracking on the surface of the insulation board.

[0021] Optionally, the mullite fiber is prepared as follows: aluminum nitrate nonahydrate is dissolved in anhydrous ethanol, ethyl orthosilicate is added to obtain an impregnation solution, kapok plant fiber is impregnated in the impregnation solution, squeezed dry, vacuum dried to obtain dry fiber, and sintered to obtain mullite fiber.

[0022] By adopting the above technical scheme, the preparation method of mullite fiber is optimized. The mullite fiber prepared by the above preparation method has a hollow structure. The introduction of the hollow structured mullite fiber can increase the hollow structure in the insulation board, which can further improve the thermal insulation effect of the insulation board. After some mullite fibers are dispersed on the surface of the insulation board, the high temperature resistance of the insulation board can be improved.

[0023] Optionally, the concentration of the impregnation solution is 25-35wt%.

[0024] By adopting the above technical solution, the concentration of the impregnating solution is optimized, and at a suitable concentration, the mullite particles can be fully wrapped on the surface of the kapok fiber, which is conducive to the formation of hollow mullite fibers with a complete structure.

[0025] Optionally, the mullite fiber is loaded on the magnetic expanded graphite, and the specific preparation method is as follows: adding the mullite fiber and the magnetic expanded graphite to ethanol, ultrasonically dispersing, adding a silane coupling agent, continuously stirring, filtering, and drying to obtain a product.

[0026] By adopting the above technical solution, under the action of the silane coupling agent, the mullite fiber can be stably loaded in the interlayer structure of the magnetic expanded graphite, which is beneficial to improve the bonding effect between the mullite fiber and the magnetic expanded graphite, that is, the mullite fiber can fully improve the structural density of the surface of the insulation board.

[0027] Optionally, the foaming agent includes alcohol, CO 2 , R-152a, HFO-1233zd and HFO-1234ze.

[0028] By adopting the above technical solution, R-152a, HFO-1233zd and HFO-1234ze are all foaming agents with low thermal conductivity, which can reduce foam density, increase foam compression strength, and make pore size distribution uniform, thereby improving the thermal insulation effect and mechanical strength of the insulation board.

[0029] Optionally, the flame retardant includes any one or more of methyl octabromoether, siloxane, silicone rubber, and ammonium polyphosphate.

[0030] By adopting the above technical solution, ammonium polyphosphate can cooperate with expanded graphite to synergistically achieve flame retardancy, thereby further improving the flame retardancy effect of the insulation board.

[0031] In a second aspect, the present application provides a method for preparing a high temperature resistant insulation board, which adopts the following technical solution:

[0032] A method for preparing a high temperature resistant insulation board comprises the following steps:

[0033] S1. Raw material preparation: Weigh polystyrene, reinforcing material, nucleating agent, flame retardant and foaming agent respectively by weight;

[0034] S2. Preparation of thermal insulation board: polystyrene, reinforcing material, nucleating agent and flame retardant are added to the first-stage extruder, mixed, foaming agent is injected from the foaming agent injection port, mixed, extruded, conveyed to the second-stage extruder through the screen changer, stirred, mixed, treated with an external magnetic field, molded, cut to obtain a composite thermal insulation board.

[0035] In summary, this application has the following beneficial effects:

[0036] 1. The introduction of magnetic expanded graphite in this application has a relatively rich interlayer structure, which can effectively play a role in thermal insulation in thermal insulation materials, and the expanded graphite has better high temperature resistance, which improves the high temperature resistance of the thermal insulation board and enables the thermal insulation board to obtain excellent flame retardant effect. Since the magnetic expanded graphite can be attracted by magnetism, the expanded graphite can be dispersed on the surface of the thermal insulation board by using an external magnetic field during the preparation of the thermal insulation board, reducing the content of polystyrene on the surface of the thermal insulation board, making the expanded graphite stable as a shielding layer of the thermal insulation board, thereby reducing the possibility of cracking on the surface of the thermal insulation board.

[0037] 2. In the present application, it is preferred that the fiber filler is pre-mixed with the magnetic expanded graphite. Since the magnetic expanded graphite has a large number of interlayer gaps, after pre-mixing, part of the fiber filler can be inserted into the interlayer of the magnetic expanded fiber to achieve the combination of the fiber and the magnetic expanded graphite. Then, the magnetic expanded graphite can synchronously drive the fiber filler to move together under the drive of the external electric field, so that the magnetic expanded graphite is connected to the fiber skeleton in the insulation board. The magnetic expanded graphite can be supported by the fiber skeleton structure, so that the surface of the insulation board has less polystyrene and can maintain a relatively complete surface structure. In addition, part of the fiber filler can be driven to the surface of the insulation board to increase the density of the shielding layer on the surface of the insulation board, further reduce the content of polystyrene on the surface of the insulation board, and reduce the possibility of cracking on the surface of the insulation board.

[0038] 3. The present application optimizes the preparation method of mullite fiber. The mullite fiber prepared by the above preparation method has a hollow structure. The introduction of the hollow structured mullite fiber can add a hollow structure to the insulation board, which can further improve the thermal insulation effect of the insulation board. After some mullite fibers are dispersed on the surface of the insulation board, the high temperature resistance of the insulation board can be improved. DETAILED DESCRIPTION

[0039] The present application is further described in detail below with reference to the embodiments.

[0040] Preparation example of magnetic expanded graphite

[0041] Preparation Example 1

[0042] Fe(NO 3 ) 3 9H 2 O and Co(NO 3 ) 2 6H 2 O mixture (Fe 3+ With Co 2+ The molar ratio of Fe3+ is 1:2) is uniformly dissolved in a 0.02 mol / L citric acid solution (the molar ratio of citric acid to Fe3+ is 4:1) to obtain a magnetic solution, and the pH of the magnetic solution is adjusted to 7-8. Expanded graphite (expanded volume of 350 mL / g) is added to the magnetic solution (solid-liquid ratio is 1:5), stirred for 30 minutes, and the obtained mixture is further baked at 600°C for 1 hour to obtain magnetic expanded graphite.

[0043] Mullite fiber preparation example

[0044] Preparation Example 2

[0045] Aluminum nitrate nonahydrate is dissolved in anhydrous ethanol, and ethyl orthosilicate is added according to the aluminum-silicon molar ratio of mullite to obtain an impregnation solution with a mass concentration of 25wt%. Kapok plant fibers are immersed in the impregnation solution for 30 minutes, then taken out, squeezed dry, and vacuum dried at 90°C for 10 hours to obtain dry fibers, which are sintered to obtain mullite fibers with a hollow structure.

[0046] Preparation Example 3

[0047] Aluminum nitrate nonahydrate is dissolved in anhydrous ethanol, and ethyl orthosilicate is added according to the aluminum-silicon molar ratio of mullite to obtain an impregnation solution with a mass concentration of 35wt%. Kapok plant fibers are immersed in the impregnation solution for 30 minutes, then taken out, squeezed dry, and vacuum dried at 90°C for 10 hours to obtain dry fibers, which are sintered to obtain mullite fibers with a hollow structure.

[0048] Examples 1-4

[0049] On the one hand, the present application provides a polystyrene composite insulation board, including polystyrene, a reinforcing material, a nucleating agent, a flame retardant and a foaming agent, and the specific qualities are shown in the table below.

[0050] Specifically, the polystyrene is general-grade polystyrene, the reinforcing material is PA6 and the magnetic expanded graphite prepared in Preparation Example 1, the nucleating agent is talcum powder, the flame retardant is methyl octabromoether and ammonium polyphosphate, and the foaming agent is carbon dioxide, HFO-1233zd and R-152a.

[0051]

[0052] On the other hand, the present application provides a method for preparing a polystyrene composite insulation board, comprising the following steps:

[0053] S1. Raw material preparation: Weigh polystyrene, reinforcing material, nucleating agent, flame retardant and foaming agent respectively by weight;

[0054] S2. Preparation of thermal insulation board: polystyrene, reinforcing material, nucleating agent and flame retardant are added to the first-stage extruder, mixed, foaming agent is injected from the foaming agent injection port, mixed, extruded, conveyed to the second-stage extruder through the screen changer, stirred, mixed, molded, cut to obtain a composite thermal insulation board.

[0055] Specifically, step S2, preparing the insulation board includes:

[0056] S21, adding polystyrene, reinforcing material, nucleating agent and flame retardant into a first-stage extruder (twin-screw extruder), and setting the temperature of each zone of the twin-screw extruder to 200-230°C;

[0057] Among them: the section from the feeding port to the foaming agent injection port is mainly a strong shearing section, which is used to fully mix the materials.

[0058] S22, the foaming agent is continuously and stably injected into the twin-screw extruder from the foaming agent injection port through the foaming agent metering pump, and mixed to obtain a mixed melt;

[0059] Among them: the foaming agent should be injected in liquid state and should be pressurized before injection to prevent gas backflow. The injection position is where the polystyrene, reinforcement material, nucleating agent and flame retardant components are evenly mixed. The screw is designed with multiple protrusions at the injection point to prevent the formation of liquid pools and promote rapid and uniform dispersion of gas in the melt. The plasticization of the melt by the foaming agent leads to a decrease in melt strength. The barrel temperature here is set to 200-210℃.

[0060] S23, the mixed melt is filtered out of large impurities through a screen changer and transported to the second-stage extruder (single screw extruder) through a melt conveying pipeline.

[0061] Among them: the single screw extruder can cool down the homogeneous melt whose melt strength has been greatly reduced after being plasticized by the foaming agent, so as to improve the melt strength and reach the viscosity range required for the molded product;

[0062] The screen changer uses a replaceable screen changing system. After a period of operation, large impurities on the wire mesh are replaced and cleaned to reduce the impact on production efficiency.

[0063] The melt delivery pipeline does not contain a screw, and its barrel temperature is set at 180-200°C;

[0064] The single screw extruder adopts a step-down mode from the front to the head to fully cool the melt. The temperature of each zone is set at 90-140℃. The speed of the single screw should not be too fast to prevent the screw shear heat from heating the melt. The melt cooling rate should be efficient and rapid. Static mixing or melt pump equipment should be set in front of the single screw head to control and maintain the pressure of the melt to prevent the melt from premature pressure release and pre-foaming. The static mixing temperature should be appropriately increased, generally set to 110-130℃, to prevent the melt from flowing in a dead zone where it stagnates.

[0065] S24, after cooling, the homogeneous melt passes through the die head and die lip, where the thermodynamic steady state is broken due to rapid pressure relief, and the foaming agent gas quickly escapes from the polymer, causing the melt volume to expand and form a closed cell structure. The XPS is then sized by a shaping template, an external magnetic field treatment (magnetic field strength of 0.5T), a whole platform, and a traction roller;

[0066] Among them: the design of the die runner must ensure that the melt flow rate at each part of the die lip is equivalent, and the pressure drop distribution in each area of ​​the mold should be calculated under the premise of controlling the total pressure drop of the melt; the pulling roller speed should be matched with the melt extrusion amount at the die mouth to ensure that the tensile force on the sheet in the lateral direction is consistent.

[0067] S25. After the XPS board is shaped and flattened, a small amount of edge material on both sides is cut off by a cutter, and after side coding and embossing on the front and back sides, it is sliced ​​by a transverse cutting machine and packaged for storage to obtain a composite insulation board.

[0068] Table 1

[0069]

[0070] Example 5

[0071] The difference from Example 4 is that the reinforcing material includes PA6, magnetic expanded graphite and carbon fiber in a mass ratio of 5:3:2.

[0072] Example 6

[0073] The difference from Example 4 is that the reinforcing material includes PA6, magnetic expanded graphite, carbon fiber and mullite fiber prepared in Preparation Example 2 in a mass ratio of 5:3:1:1, the magnetic expanded graphite, carbon fiber and mullite fiber are pre-ground and mixed, and then blended with PA6 and added to the first-stage extruder.

[0074] Example 7

[0075] The difference from Example 4 is that the reinforcing material includes PA6, magnetic expanded graphite, carbon fiber and mullite fiber prepared in Preparation Example 3 in a mass ratio of 5:3:1:1, the magnetic expanded graphite, carbon fiber and mullite fiber are pre-ground and mixed, and then blended with PA6 and added to the first-stage extruder.

[0076] Example 8

[0077] The difference from Example 4 is that the reinforcing material includes PA6, magnetic expanded graphite, carbon fiber and mullite fiber prepared in Preparation Example 3 in a mass ratio of 5:3:1:1.

[0078] Add magnetic expanded graphite and mullite fiber to ethanol, add 2% silane coupling agent KH560, stir, mix, filter, and dry to obtain a product. Mix the product with carbon fiber, and then blend with PA6 and add it to a first-stage extruder.

[0079] Comparative Example 1

[0080] The difference between this comparative example and Example 4 is that no reinforcing material is added in this comparative example.

[0081] Performance testing:

[0082] (1) Apparent density test: The test shall be conducted in accordance with the test method of GB / T6343-1996 "Determination of apparent (bulk) density of cellular plastics and rubber".

[0083] (2) Thickness detection: Use a ruler to measure the thickness of the insulation board.

[0084] (3) Compression strength test: Test the 10% compression strength and side compression strength of the insulation board according to GB / T8813-1998 "Compression test method for rigid foam plastics".

[0085] (4) Thermal deformation test: Use a thermal deformation Vicat softening point tester to test the thermal deformation temperature of the insulation board.

[0086] (5) Thermal conductivity test: The thermal conductivity test equipment uses FOX200 produced by TA Instruments of the United States.

[0087] (6) Combustion performance test: The combustion performance level of the insulation board is tested according to GB / T 10801.2-2018 Extruded polystyrene foam for thermal insulation.

[0088] (7) High temperature resistance test: The insulation board is tested at (150℃ / 2h, 150℃ / 6h, 165℃ / 6h, 180℃ / 6h, 180℃ / 12h, 200℃ / 6h). The test methods and standards are in accordance with GB17657-2013.

[0089] Table 2 Performance test

[0090]

[0091] Table 3 High temperature resistance test

[0092]

[0093] Combining the performance test comparison in Table 2, we can find that:

[0094] 1. By comparing Examples 1-4 with Comparative Example 1, it can be found that the high temperature resistance of the thermal insulation board prepared in Examples 1-4 is improved, which indicates that the magnetic expanded graphite in the present application can be attracted by magnetism. Therefore, the expanded graphite can be dispersed on the surface of the thermal insulation board by using an external magnetic field during the preparation of the thermal insulation board, thereby reducing the content of polystyrene on the surface of the thermal insulation board, and stabilizing the expanded graphite as a shielding layer of the thermal insulation board, thereby reducing the possibility of cracking on the surface of the thermal insulation board.

[0095] 2. By comparing Example 5 with Example 4, it can be found that the high temperature resistance of the insulation board prepared in Examples 1-4 is improved, which shows that in the present application, carbon fiber, silicon carbide fiber and mullite fiber all have relatively good high temperature resistance. When added to the insulation board, a staggered fiber structure can be introduced into the insulation board, that is, a three-dimensional skeleton structure is introduced into the insulation board, which is beneficial to improve the mechanical strength of the insulation board. Part of the fiber filler can be driven to the surface of the insulation board, increasing the density of the shielding layer on the surface of the insulation board, further reducing the content of polystyrene on the surface of the insulation board, and reducing the possibility of cracking on the surface of the insulation board.

[0096] 3. By comparing Examples 6-7 with Example 4, it can be found that the high temperature resistance of the insulation board prepared in Examples 1-4 is improved, which means that the introduction of hollow mullite fibers in the present application can add a hollow structure to the insulation board, which can further improve the thermal insulation effect of the insulation board, and after some mullite fibers are dispersed on the surface of the insulation board, the high temperature resistance of the insulation board can be improved.

[0097] 4. By comparing Example 8 with Example 4, it can be found that the high temperature resistance of the insulation board prepared in Examples 1-4 is improved, which means that in the present application, under the action of the silane coupling agent, the mullite fiber can be stably loaded in the interlayer structure of the magnetic expanded graphite, which is beneficial to improve the bonding effect between the mullite fiber and the magnetic expanded graphite, that is, the mullite fiber can fully improve the structural density of the surface of the insulation board.

[0098] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A high temperature resistant insulation board, characterized in that: Includes the following substances in weight percentage: Polystyrene 75-90wt%; Reinforcement material 5-10wt%; Nucleating agent 0.5-3wt%; Flame retardant 1-5wt%; Foaming agent 5-10wt%; The sum of the weight percentages of each substance is 100%; The reinforcing material includes any one or more of polyamide 6, ABS, and PC, and the reinforcing material also includes magnetic expanded graphite, and the magnetic expanded graphite is distributed on the surface of the high temperature resistant insulation board; The reinforcing material further comprises fiber fillers, and the fiber fillers comprise carbon fibers and mullite fibers; The fiber filler is mixed with the magnetic expanded graphite in advance.

2. A high temperature resistant insulation board according to claim 1, characterized in that: The preparation of the magnetic expanded graphite is as follows: a magnetic body is mixed with a citric acid solution, the pH is adjusted to obtain a magnetic solution, the expanded graphite is immersed in the magnetic solution, stirred, and baked to obtain the magnetic expanded graphite.

3. The high temperature resistant insulation board according to claim 1, characterized in that: The mullite fiber is prepared as follows: aluminum nitrate nonahydrate is dissolved in anhydrous ethanol, ethyl orthosilicate is added to obtain an impregnation solution, kapok plant fiber is impregnated in the impregnation solution, squeezed dry, vacuum dried to obtain dry fiber, and sintered to obtain mullite fiber.

4. A high temperature resistant insulation board according to claim 3, characterized in that: The concentration of the impregnation solution is 25-35wt%.

5. The high temperature resistant insulation board according to claim 1, characterized in that: The mullite fiber is loaded on the magnetic expanded graphite, and is specifically prepared as follows: adding the mullite fiber and the magnetic expanded graphite into ethanol, ultrasonically dispersing, adding a silane coupling agent, continuously stirring, filtering, and drying to obtain a product.

6. The high temperature resistant insulation board according to claim 1, characterized in that: The foaming agent includes any one or more of alcohol, CO2, R-152a, HFO-1233zd and HFO-1234ze.

7. The high temperature resistant insulation board according to claim 1, characterized in that: The flame retardant includes any one or more of methyl octabromoether, siloxane, silicone rubber, and ammonium polyphosphate.

8. A method for preparing a high temperature resistant insulation board according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Raw material preparation: Weigh polystyrene, reinforcing material, nucleating agent, flame retardant and foaming agent respectively by weight; S2. Preparation of thermal insulation board: polystyrene, reinforcing material, nucleating agent and flame retardant are added to the first-stage extruder, mixed, foaming agent is injected from the foaming agent injection port, mixed, extruded, conveyed to the second-stage extruder through the screen changer, stirred, mixed, treated with an external magnetic field, molded, cut to obtain a composite thermal insulation board.

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