Preparation method of EPS (Expandable Polystyrene) foam insulation board

Abstract

The invention provides a preparation method of an EPS foam insulation board, and relates to the technical field of foam insulation boards, the preparation method comprises the following steps: S1, raw material preparation: screening EPS foam particles, and controlling the particle size to be 5-8 mm; the EPS foam particles, the flame retardant, the antioxidant and the auxiliaries are put into a mixing machine to be stirred, and the rotating speed ranges from 230 RPM to 500 RPM. According to the preparation method, the particle size of EPS particles is screened, the mixing uniformity of the raw materials is optimized, the uniformity and compactness of the internal structure of the material are enhanced in a dynamic particle filling mode in the melting process, meanwhile, the surfaces of the EPS particles are tightly combined with a gel matrix containing red phosphorus through a hydrogel embedding technology, and the overall flame retardant property and structural stability of the material are improved; in the continuous foaming stage, high-pressure steam is used for promoting the hydrogel and EPS particles to expand together to form a more uniform pore structure.

Description

Technical Field

[0001] This invention relates to the field of foam insulation board technology, and in particular to a method for preparing EPS foam insulation board. Background Technology

[0002] Foam insulation boards are made by using polymer materials through foaming technology to produce lightweight, porous boards. These boards typically have excellent thermal insulation, heat preservation, moisture resistance, and sound insulation properties, and are widely used for thermal insulation of building walls, roofs, and floors, as well as for thermal protection of cold storage, industrial equipment, pipes, and containers.

[0003] In practical manufacturing, existing technologies typically utilize a single foaming process with polymer materials to produce foam boards. This approach fails to effectively address the density variations in the boards caused by uneven particle size and incomplete raw material mixing. Consequently, the resulting foam boards exhibit insufficient overall structural uniformity and are prone to developing weak areas with uneven density distribution. Therefore, improvements are necessary. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for preparing EPS foam insulation boards.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing EPS foam insulation board, comprising the following steps: S1. EPS foam particles are screened, and the particle size is controlled within the range of 5-8 mm. EPS foam particles, flame retardant, antioxidant and additives are put into a mixer and stirred at a speed of 230-500 RPM for 25-35 min. The mixing process is maintained in the range of 50-60℃ to obtain EPS mixed raw materials. S2, Dynamic melt microparticles are added to the EPS mixed raw material; the mixture is compounded using a twin-screw extruder, with the extrusion temperature controlled at 140-160℃, the screw speed maintained in the range of 40-60 RPM, and the outlet pressure in the range of 0.1-0.2 MPa, to obtain microparticle filler; S3, hydrogel embedding of the microparticle filler: Sodium alginate and agar are dissolved in a water bath at 60-70℃, and calcium chloride and melamine are added at a stirring speed of 300-400 RPM, and stirring is continued for 15-25 min to form a gel matrix; the microparticle filler is immersed in the gel matrix to ensure full contact between the surface of the EPS particles and the gel matrix, and the immersion time is controlled between 5-10 min; then, it is dried at a constant temperature of 40-50℃ using a forced-air drying oven to obtain the hydrogel embedding material. The hydrogel embedding material is dried to form a foam insulation board.

[0006] Preferably, it also includes: S4, feeding the hydrogel embedding material into a continuous foaming machine, maintaining the internal temperature in the range of 100-120℃ and the pressure in the range of 0.2-0.3 MPa by steam heating; setting the foaming time to 30-60 min, the hydrogel and EPS particles expand together under the action of heat to form a porous structure, and obtaining preliminary foamed foam. S5, the preliminary foam is fed into a heating furnace, the temperature is set at 60-80℃, the blower speed is controlled at 0.3-0.5 m / s; the conveyor belt speed is maintained at 0.5-1 m / min, and the preliminary foam stays in the furnace for 15-25 min to obtain the preliminary low-temperature extended material; S6. The temperature of the heating furnace is further increased to 120-160℃ and maintained for 20-40 minutes to allow the material to complete the cross-linking and curing process, resulting in cross-linked foam.

[0007] Preferably, the method further includes: S7, feeding the cross-linked foam into a flat plate pressing mold, maintaining the mold temperature in the range of 30-40°C, applying a molding pressure of 0.1-0.2 MPa; controlling the pressing time to 10-20 min according to the thickness of the board to obtain a cured board; S8. Perform surface spraying and hardening treatment on the cured board; control the spray gun pressure in the range of 0.2-0.3 MPa, spray interval of 5-10 min, repeat 2-5 times; after standing for 30-60 min, send the board into a UV curing unit or hot air curing box for curing, maintain the temperature in the range of 40-60℃, and control the time in the range of 2-3 h; obtain flame-retardant EPS insulation board.

[0008] Preferably, in step S1, the flame retardant is a mixture of melamine, antimony trioxide, brominated polystyrene, and phosphorus pentoxide in a mass ratio of 2-3:1-2:1-4:1-2; the antioxidant is a mixture of tert-butylhydroquinone, propyl gallate, BHT, and vitamin E in a mass ratio of 1-3:1-3:1-3:1-3; and the additives are a mixture of calcium stearate, polyethylene glycol, polyacrylamide, and sodium dodecyl sulfate in a mass ratio of 2-3:1-2:1-4:1-2.

[0009] Preferably, in step S2, the dynamically molten microparticles are composed of polypropylene, talc, calcium carbonate and glass fiber in a mass ratio of 2-3:1-2:1-4:1-2.

[0010] Preferably, in step S3, the hydrogel is composed of sodium alginate, agar, calcium chloride and melamine in a mass ratio of 2-3:2-3:1-2:1-2.

[0011] Preferably, in step S8, the sprayed material consists of a fire-retardant coating and a scratch-resistant resin, wherein the fire-retardant coating is composed of aluminum hydroxide, flame-retardant ammonium polyphosphate, melamine-formaldehyde resin and silicone-acrylic emulsion in a mass ratio of 2-3:1-2:1-4:1-2, and the scratch-resistant resin is composed of polyurethane and a curing agent in a mass ratio of 2-4:1-3.

[0012] Compared to existing technologies, this invention enhances the uniformity and density of the internal structure of EPS by sieving the particle size and optimizing the uniformity of raw material mixing. During the melting process, it utilizes dynamic microparticle filling to strengthen the uniformity and density of the material's internal structure. Simultaneously, hydrogel embedding technology tightly bonds the surface of the EPS particles with a red phosphorus-containing gel matrix, improving the overall flame retardant performance and structural stability of the material. In the continuous foaming stage, high-pressure steam promotes the co-expansion of the hydrogel and EPS particles, forming a more uniform pore structure. In the subsequent heating stage, temperature-controlled segmented heating achieves cross-linking curing and hierarchical expansion of the material, improving the mechanical strength and compressive strength of the insulation board. The cooling process strictly controls the cooling rate and gradient to ensure the stability of the cell structure, preventing cell collapse and deformation. Mold pressing and multiple spray hardening treatments further enhance the surface hardness and wear resistance of the molded board. While improving the flame retardant performance of the EPS foam insulation board, it also enhances the board's compressive strength, thermal insulation, and structural durability, significantly increasing the board's service life, ensuring the safety and reliability of the material in long-term applications, and reducing construction risks and subsequent maintenance costs.

[0013] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 The present invention provides a method for preparing EPS foam insulation boards, which includes the following preparation steps. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1: A method for preparing EPS foam insulation board, comprising the following steps: S1. Raw material preparation: EPS foam particles are sieved and the particle size is controlled at 8 mm. EPS foam particles, flame retardant, antioxidant and additives are put into a mixer and stirred at 500 RPM for 35 min. The mixing process is maintained at 50℃ to obtain EPS mixed raw material. S2, Dynamic Melt Microparticle Filler, is made by adding dynamic melt microparticles to EPS mixed raw materials; the mixing is carried out using a twin-screw extruder, the extrusion temperature is controlled at 160℃, the screw speed is maintained at 40 RPM, and the outlet pressure is 0.1MPa to obtain microparticle filler; S3, Hydrogel Preparation and Embedding: Hydrogel embedding of microparticle fillers; Sodium alginate and agar are dissolved in a 70℃ water bath, and calcium chloride and melamine are added at a stirring speed of 400 RPM and stirred continuously for 25 min to form a gel matrix; The microparticle fillers are immersed in the gel matrix to ensure full contact between the surface of the EPS particles and the gel matrix, and the immersion time is controlled within 5 min; Subsequently, the particles are dried at a constant temperature of 50℃ using a forced-air drying oven to obtain the hydrogel embedding material.

[0018] S4, heating and foaming: The hydrogel embedding material is fed into a continuous foaming machine, and the internal temperature is maintained at 120℃ and the pressure is 0.2 MPa by steam heating; the foaming time is set to 60 min. The hydrogel and EPS particles expand together under the action of heat to form a porous structure and obtain preliminary foam. S5, Layered Expansion: The initial foamed foam is fed into a heating furnace, the temperature is set at 80℃, the blower speed is controlled at 0.5 m / s, the conveyor belt speed is maintained at 1 m / min, and the initial foamed foam stays in the furnace for 15 min to obtain the initial low-temperature expanded material. S6, Layered Expansion: The temperature of the heating furnace is further increased to 160℃ and maintained for 20 minutes to allow the material to complete the cross-linking and curing process, resulting in cross-linked foam; S7, Molding and Curing: The cross-linked foam is fed into a flat pressing mold, the mold temperature is maintained at 30℃, and a molding pressure of 0.1MPa is applied; the pressing time is controlled at 20 min according to the thickness of the board to obtain the cured board; S8, Surface treatment: Surface spraying and hardening treatment is carried out on the cured board; the spray gun spraying pressure is controlled at 0.3MPa, the spraying interval is 5min, and it is repeated 5 times; after standing for 60min, the board is sent to the UV curing unit or hot air curing box for curing, the temperature is maintained at 60℃, and the time is controlled at 2h; flame-retardant EPS insulation board is obtained.

[0019] In this embodiment, in step S1, the flame retardant is a mixture of melamine, antimony trioxide, brominated polystyrene, and phosphorus pentoxide in a mass ratio of 3:2:4:1; the antioxidant is a mixture of tert-butylhydroquinone, propyl gallate, BHT, and vitamin E in a mass ratio of 3:1:1:1; and the additive is a mixture of calcium stearate, polyethylene glycol, polyacrylamide, and sodium dodecyl sulfate in a mass ratio of 2:2:4:1.

[0020] In this embodiment, in step S2, the dynamically molten microparticles are formed by mixing polypropylene, talc, calcium carbonate and glass fiber in a mass ratio of 2:1:1:2.

[0021] In this embodiment, in step S3, the hydrogel is made by mixing sodium alginate, agar, calcium chloride and melamine in a mass ratio of 3:3:1:2.

[0022] In this embodiment, in step S8, the sprayed material consists of a fire-retardant coating and a scratch-resistant resin. The fire-retardant coating is composed of aluminum hydroxide, flame-retardant ammonium polyphosphate, melamine-formaldehyde resin and silicone acrylic emulsion in a mass ratio of 3:2:4:1. The scratch-resistant resin is composed of polyurethane and a curing agent in a mass ratio of 4:3.

[0023] Example 2 is the same as Example 1, except that it includes a method for preparing EPS foam insulation board, comprising the following steps: S1. Raw material preparation: EPS foam particles are sieved and the particle size is controlled within 5mm. EPS foam particles, flame retardant, antioxidant and additives are put into a mixer and stirred at a speed of 400RPM for 35 minutes. The mixing process is maintained at 60℃ to obtain EPS mixed raw materials. S2, Dynamic Melt Microparticle Filler, is made by adding dynamic melt microparticles to EPS mixed raw materials; the mixing is carried out using a twin-screw extruder, the extrusion temperature is controlled at 160℃, the screw speed is maintained at 60RPM, and the outlet pressure is 0.2MPa to obtain microparticle filler; S3, Hydrogel Preparation and Embedding: Hydrogel embedding of microparticle fillers; Sodium alginate and agar are dissolved in a 70℃ water bath, and calcium chloride and melamine are added at a stirring speed of 400 RPM and stirred continuously for 25 min to form a gel matrix; The microparticle fillers are immersed in the gel matrix to ensure full contact between the surface of the EPS particles and the gel matrix, and the immersion time is controlled within 10 min; Subsequently, the material is dried at a constant temperature of 50℃ using a forced-air drying oven to obtain the hydrogel embedding material.

[0024] Experimental methods: Thermal conductivity test: Reference standards: Refer to GB / T 10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Protective Hot Plate Method" or GB / T 10295-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Heat Flow Meter Method". The heat flow meter method is commonly used because it is relatively fast.

[0025] Testing equipment: Precision heat flow meter for measuring thermal conductivity. The equipment mainly includes a heating unit (hot plate), a cooling unit (cold plate), a heat flow sensor, a thickness measuring device, a temperature control system, and a data acquisition system.

[0026] Sample Preparation: Cut at least three identical square or circular samples from the prepared flame-retardant EPS foam insulation board, typically 300mm × 300mm or as required by the instrument. The samples should have uniform thickness and a smooth surface free of obvious defects. After cutting, the samples should be conditioned in a standard laboratory environment (typically 23±2℃, 50±5% relative humidity) for at least 24 hours, or until the mass is constant. Accurately measure the thickness and area of ​​each sample.

[0027] Test conditions: Set the hot plate temperature (Th) and cold plate temperature (Tc) of the instrument. Typically, a temperature gradient simulating actual application conditions is selected. For example, set the hot plate temperature to 35°C and the cold plate temperature to 15°C, resulting in an average test temperature of approximately 25°C. Ensure good contact between the hot and cold plate surfaces and the sample. If necessary, apply a small amount of thermal grease to the contact surfaces to reduce contact thermal resistance.

[0028] Test steps: Turn on the instrument and preheat it to the set hot and cold plate temperatures until it reaches a stable state.

[0029] Place the conditioned sample between the hot and cold plates, ensuring that the sample is centered and in close contact with the plate surface.

[0030] Start the thickness measuring device to accurately measure the thickness (L) of the sample under the test pressure.

[0031] The test program is started, and the instrument automatically controls the temperature of the hot and cold plates to remain constant, and measures the heat flow (Q) through the sample using a heat flow sensor.

[0032] Continuously monitor temperature and heat flow until the system reaches steady state (usually defined as a continuous period of time during which the temperature and heat flow readings change by less than a set threshold, such as 1%).

[0033] Record the hot plate temperature, cold plate temperature, sample thickness, and heat flow through the central metering region of the sample at steady state.

[0034] Results Calculation: Thermal conductivity (λ) is calculated according to Fourier's law: λ = (Q × L) / (A × (Th - Tc)). Where Q is the steady-state heat flux (W), L is the sample thickness (m), A is the measurement area (m²), and Th and Tc are the temperatures of the hot and cold plates, respectively (K or °C). The average value of multiple sample test results is taken as the final reported value, in units of W / (m·K).

[0035] Limiting Oxygen Index (LOI) Test: Reference standards: Refer to GB / T 2406.2-2009 "Determination of flammability of plastics by oxygen index method - Part 2: Test at room temperature" or ISO 4589-2:2017.

[0036] Testing equipment: Limiting oxygen index (LOI) tester. This mainly includes a combustion chamber (usually a vertical glass tube), a gas mixing and flow control system (for precise control of the nitrogen and oxygen ratio and total flow rate), a sample holder, and an igniter (such as a propane flame torch).

[0037] Specimen preparation: Prepare strip-shaped specimens according to the standard specifications, typically (80-150) mm × 10 mm × (4±0.25) mm, or select appropriate sizes and types based on the material morphology. Specimens should be representative with smooth edges. Prepared specimens should be conditioned in a standard laboratory environment (23±2℃, 50±5% RH) for at least 48 hours or until their mass is constant.

[0038] Test conditions: The test was conducted at room temperature. The total flow rate of the nitrogen-oxygen mixture was set to ensure a stable laminar flow within the combustion chamber. The igniter flame height was adjusted to standard (e.g., approximately 50 mm high for a propane flame, with a blue inner flame of approximately 25 mm).

[0039] Test steps: The sample is held vertically in the sample clamp in the center of the combustion cylinder.

[0040] Set an initial oxygen concentration (volume percentage), introduce a nitrogen-oxygen mixture, and wait at least 30 seconds for the gas environment inside the cylinder to stabilize.

[0041] Ignite the sample from the top using an igniter, with the ignition time as specified in the standard (e.g., within 10 seconds). Remove the igniter immediately after ignition.

[0042] Observe the combustion behavior of the sample. Record the duration of combustion or the length of flame spread. The judgment criteria are usually: the flame extinguishes itself within a specified time (e.g., 180 seconds), or the length of combustion does not exceed the specified mark (e.g., 50 mm below the top).

[0043] Depending on whether the sample continues to burn or extinguishes, adjust the oxygen concentration (decrease the oxygen concentration if it continues to burn, and increase the oxygen concentration if it extinguishes). Repeat steps 2-4, using the "up-down method" or a similar approximation method to find the critical oxygen concentration. The step size for each adjustment of the oxygen concentration should be in accordance with the standard specifications (it can be larger initially, and decreased as it approaches the critical value).

[0044] The limiting oxygen index is the minimum oxygen concentration required to sustain combustion (or just barely sustain combustion) of a sample. This value needs to be determined precisely through a series of effective tests (e.g., multiple consecutive tests yielding opposite results).

[0045] Results Calculation: The Limiting Oxygen Index (LOI) is expressed as the volume percentage of oxygen in a nitrogen-oxygen mixture. The formula is: LOI = [O2] / ([O2] + [N2]) × 100%. Where [O2] and [N2] are the minimum volumetric flow rates of oxygen and nitrogen required to sustain combustion, respectively. The reported value is the average of calculations from multiple valid tests, typically accurate to 0.1%.

[0046] Vertical Burning Test: Reference standards: Refer to the flammability rating in GB / T 8627-2007 "Test Method for Smoke Density of Building Materials for Combustion or Decomposition" or the vertical flammability test section in GB / T 2408-2008 "Determination of Flammability of Plastics - Horizontal and Vertical Methods" (corresponding to UL 94 standard). For building insulation materials, GB 8624-2012 "Classification of Flammability of Building Materials and Products" is more commonly referred to. This section simulates a test process similar to UL 94 Class V.

[0047] Test equipment: Vertical combustion test chamber, with built-in sample holder, standard Bunsen burner (flame height adjustable), timer, and fume hood (for smoke extraction).

[0048] Specimen Preparation: Prepare strip specimens of the specified dimensions, e.g., 125mm × 13mm × (actual thickness of the board). The edges should be smooth. Prepare multiple sets of specimens (e.g., 5 specimens per set). Condition the specimens at a standard environment (23±2℃, 50±5% RH) for at least 48 hours before testing. Place a layer of degreased cotton under the specimen to observe for any burning droplets that could ignite the cotton.

[0049] Test conditions: The flame height of the standard Bunsen burner is adjusted to the specified value (e.g., inner flame 20mm, total height 100mm). The test is conducted in a combustion chamber without forced ventilation.

[0050] Test steps: Clamp the sample vertically, with the lower end at a specified distance (e.g., 10 mm) from the Bunsen burner nozzle.

[0051] Move the Bunsen lamp to the center of the sample and apply the flame for 10 seconds.

[0052] Remove the Bunsen lamp and start the first timer (t1) to record the flaming combustion time of the sample.

[0053] After the flaming combustion stops, if the sample exhibits flameless combustion (glow), start the second timer (t2) and record the flameless combustion time.

[0054] After the first flaming combustion stops, immediately (or after a short period of time, depending on the specific standard) move the Bunsen lamp under the sample again and apply the flame for 10 seconds.

[0055] Remove the Bunsen lamp and start the third timer (t3) to record the flaming time after the second application of flame.

[0056] After the second flaming combustion stops, if there is flameless combustion, start the fourth timer (t4) and record its duration.

[0057] Record throughout the process whether the sample burns through, whether there are burning droplets, and whether the droplets ignite the degreased cotton below.

[0058] Result Interpretation: According to GB 8624 standard, the flammability rating of building materials (such as B1 and B2 grades) involves more complex test combinations (such as the Single Intake Burning Test (SBI)). A simplified simulation of UL 94 Class V determination is possible. V-0 level: After each application of flame, the flaming time (t1 or t3) is ≤10 seconds; the total flaming time (t1+t3) is ≤50 seconds (for a group of 5 samples); the flameless burning time (t4) after the second application of flame is ≤30 seconds; no sample burns through; no burning droplets ignite the absorbent cotton.

[0059] V-1 level: After each application of flame, the flaming time (t1 or t3) is ≤30 seconds; the total flaming time (t1+t3) is ≤250 seconds (for a group of 5 samples); the flameless time (t4) after the second application of flame is ≤60 seconds; no sample burns through; no burning droplets ignite the absorbent cotton.

[0060] V-2: Same as V-1, but allows burning drippings to ignite absorbent cotton.

[0061] If the V-2 requirements are not met, the rating will be either "failed" or lower (e.g., HB level flammability). The B1 and B2 ratings here simulate the ratings of domestic building materials. B1 has stricter requirements and typically corresponds to flame-retardant materials, while B2 is for combustible materials.

[0062] Compression Strength Test: Reference standards: Refer to GB / T 8813-2008 "Determination of compressive properties of rigid foamed plastics" or ISO 844:2014.

[0063] Testing equipment: Universal testing machine (equipped with compression clamps and flat plate), thickness gauge.

[0064] Specimen preparation: Cut square or circular specimens from the sheet material, typically 50mm × 50mm or 100mm × 100mm, with the same thickness as the original sheet material. Ensure the top and bottom surfaces are parallel and flat. Prepare at least 5 specimens. Condition at a standard environment (23±2℃, 50±5% RH) for at least 24 hours.

[0065] Test conditions: The loading speed of the testing machine is constant, usually set to 10% of the initial thickness of the sample per minute. For example, for a 50 mm thick sample, the speed is 5 mm / min.

[0066] Test steps: Measure the initial thickness (h0) and cross-sectional area (A) of the specimen.

[0067] Place the sample in the center of the lower pressure plate of the testing machine.

[0068] Start the testing machine, and the upper platen moves downward at a set constant speed to apply a compressive load to the specimen.

[0069] Continuously record the load (F) and displacement (or deformation Δh).

[0070] Continue loading until the specimen yields (the load stops increasing or begins to decrease) or reaches the specified relative deformation (usually 10%).

[0071] Record the load F10 when the relative deformation reaches 10% (i.e., deformation Δh = 0.1 × h0). If the material yields or fails when the deformation is less than 10%, record the load at the yield point or failure point and the corresponding deformation.

[0072] Results Calculation: Compressive strength is typically reported as the compressive stress (σ10) at 10% relative deformation. The formula is: σ10 = F10 / A. Units are typically kilopascals (kPa) or megapascals (MPa). If the material yields or fails before 10% deformation, the compressive yield strength or failure strength is reported. The average of results from multiple specimens is taken.

[0073] Water Absorption Test: Reference standards: Refer to GB / T 8810-2005 "Determination of water absorption of rigid foamed plastics" or ISO 2896:2001. Short-time partial immersion or long-time full immersion methods are commonly used. The long-time full immersion method is described here.

[0074] Test equipment: constant temperature water bath, balance (accuracy 0.01g or higher), drying oven, measuring instruments.

[0075] Specimen preparation: Cut cube or cuboid specimens of the specified dimensions, such as 100mm × 100mm × 50mm. The specimen surface should be intact, without any broken skin. Prepare at least 3 specimens. First, dry the specimens in an oven at (50±2)℃ until constant weight (two consecutive weighings 24 hours apart, with a mass change of less than 0.1%), and record the mass after drying (m_dry).

[0076] Test conditions: The water temperature in the constant temperature water bath is maintained at (23±2)℃.

[0077] Test Procedure: Completely immerse the dried sample to constant weight in a water bath, ensuring all surfaces of the sample are in contact with water and the top of the sample is at least 50 mm above the water surface. Weights or a grid can be used to prevent the sample from floating, but it should be ensured that water can freely contact the sample surface.

[0078] Soaking time is specified, such as the standard requirement of 28 days, or other time points can be selected as needed (such as 24 hours).

[0079] After the specified soaking time has been reached, remove the sample from the water, quickly wipe off the surface water with a wrung-out damp cloth, and immediately weigh it (m_wet). At the same time, measure the dimensions of the sample to calculate its volume (V).

[0080] Results Calculation: Water absorption rate is usually expressed as volume percentage (V / V) or mass percentage (m / m).

[0081] Volumetric water absorption rate (%) = [(m_wet - m_dry) / ρ_water] / V × 100%. Where ρ_water is the density of water (approximately 1000 kg / m³ or 1 g / cm³), and V is the original volume of the sample.

[0082] Mass water absorption rate (%) = (m_wet - m_dry) / m_dry × 100%.

[0083] The report must specify the calculation method and soaking time used. The average value of multiple sample results should be taken.

[0084] Dimensional Stability Test: Reference standards: Refer to GB / T 8811-2008 "Test method for dimensional stability of rigid foamed plastics" or ISO2796:1986.

[0085] Testing equipment: constant temperature and humidity chamber or drying oven, precision measuring instruments (such as digital calipers or length measuring instruments with an accuracy of 0.01mm).

[0086] Specimen preparation: Cut specimens to the specified dimensions, typically cuboids, such as 200mm × 50mm × (plate thickness). Mark measurement points along the length, width, and thickness directions. Prepare at least three specimens. Condition the specimens at a standard environment (23±2℃, 50±5%RH) for at least 24 hours. Accurately measure the initial length (L0), width (W0), and thickness (T0) of each specimen at the marked points.

[0087] Test conditions: Select test conditions as needed, such as placing it in an oven at (70±2)℃ for 48 hours as mentioned in the question. Other temperature and humidity combinations can also be selected, such as high temperature and high humidity or low temperature conditions.

[0088] Test procedure: Place the measured initial size of the sample into a constant temperature chamber that has reached the set temperature (and humidity, if necessary). There should be a gap between the samples to avoid contact.

[0089] Keep the sample exposed to specified conditions for a specified time (e.g., 48 hours at 70°C).

[0090] After the specified time has elapsed, remove the sample and place it back in a standard environment (23±2℃, 50±5% RH) to cool for at least 1 hour.

[0091] At the same location as the initial measurement, the final length (L1), width (W1), and thickness (T1) of the specimen were measured again.

[0092] Results Calculation: Calculate the rate of change of dimensions in the length, width, and thickness directions: Length change rate (%) = (L1 - L0) / L0 × 100% Width change rate (%) = (W1 - W0) / W0 × 100% Thickness change rate (%) = (T1 - T0) / T0 × 100% Report the rate of dimensional change in each direction, typically the maximum absolute value or reported separately. Retain one decimal place. Average the results from multiple samples.

[0093] Experiments were conducted on the finished materials prepared in Examples 1-2, with Comparative Example 1 being the finished material prepared using Chinese Patent Publication No. CN104086913B. The experimental results are as follows: As shown in Table 1, Examples 1-2 exhibit superior overall performance compared to Comparative Example 1. Specifically, the flame-retardant EPS foam insulation boards prepared in Examples 1-2 of this invention demonstrate lower thermal conductivity, indicating better thermal insulation performance and contributing to improved building energy efficiency. Simultaneously, Examples 1-2 show an increased limiting oxygen index and a higher vertical flammability rating of B1, demonstrating superior flame-retardant safety. In terms of mechanical properties, Examples 1-2 exhibit higher compressive strength, enabling them to withstand greater loads. Furthermore, Examples 1-2 show significantly reduced water absorption, improving the material's durability and stability in humid environments, and exhibiting better dimensional stability under high-temperature conditions. These improvements make the products of this invention superior to existing technologies in terms of safety, energy efficiency, and durability.

[0094] Compared to Example 1, Example 2 shows slight improvements in all performance indicators (lower thermal conductivity, higher LOI in combustion performance, higher compressive strength, lower water absorption, and better dimensional stability). This can be attributed to the adjustment of the aforementioned process parameters: Smaller EPS particle size (Example 2: 5mm vs. Example 1: 8mm): Impact: Using smaller EPS particles results in a greater number of particles and a larger total surface area within the same volume. This facilitates more uniform and thorough contact and mixing with subsequent flame retardants, additives, dynamically molten microparticles, and hydrogels. It may also lead to a finer and more uniform cell structure after foaming.

[0095] Effect: Reduced thermal conductivity: The finer and more uniform pore structure can more effectively impede heat through gas convection and solid conduction. Therefore, the thermal conductivity of Example 2 is slightly lower than that of Example 1 (0.034 vs 0.035 W / (m·K)).

[0096] Increased compressive strength: A finer pore structure usually means higher material density and stronger structural support, so Example 2 has higher compressive strength (225 vs 210 kPa).

[0097] Reduced water absorption: The smaller, potentially more closed-cell structure reduces the channels for water penetration, resulting in a lower water absorption rate (1.8% vs 2.0%).

[0098] Improved dimensional stability: The uniform and dense structure results in more even thermal expansion and contraction, leading to better stability (<0.4% vs <0.5%).

[0099] S1 Mixing Condition Adjustment (Example 2: 400 RPM / 60°C vs Example 1: 500 RPM / 50°C): Impact: The mixing speed in Example 2 was lower, but the temperature was higher. The lower speed may reduce physical damage to the particles, while the higher temperature may help to slightly soften the EPS surface, promoting better adhesion or slight melting of additives (especially flame retardants, antioxidants, etc.).

[0100] Effect: This factor alone may have a small impact, but it may work synergistically with smaller particle sizes to promote uniform premixing of raw materials.

[0101] S2 extrusion condition adjustment (Example 2: 60 RPM / 0.2 MPa vs Example 1: 40 RPM / 0.1 MPa): Impact: The higher screw speed (60 RPM) in Example 2 means stronger shearing action, which helps the dynamically molten microparticles (polypropylene, talc, calcium carbonate, glass fiber) to disperse more evenly in the EPS matrix. The higher outlet pressure (0.2 MPa) may result in a denser mixture.

[0102] Effect: Improved compressive strength: Dynamically molten microparticles, as a reinforcing phase, have a more uniform dispersion that can more effectively improve the mechanical properties of the material, thus contributing to increased compressive strength.

[0103] Improved Flame Retardancy (LOI): Dynamically molten microparticles may contain or synergistically act as flame retardants (e.g., non-flammable glass fiber, endothermic decomposition of talc and calcium carbonate upon heating), and more uniform dispersion contributes to improved overall flame retardancy (LOI 35% vs 34%).

[0104] S3 hydrogel impregnation time is longer (Example 2: 10 min vs. Example 1: 5 min): Impact: The longer impregnation time (10 minutes) allows the hydrogel matrix (containing flame-retardant components such as sodium alginate, agar, calcium chloride and melamine) to penetrate more fully into the surface and possible pores of the particulate filler, forming a thicker and more complete coating layer.

Claims

1. A method for preparing EPS foam insulation board, characterized in that, Includes the following steps: S1. EPS foam particles are screened, and the particle size is controlled within the range of 5-8 mm. EPS foam particles, flame retardant, antioxidant and additives are put into a mixer and stirred at a speed of 230-500 RPM for 25-35 min. The mixing process is maintained in the range of 50-60℃ to obtain EPS mixed raw materials. S2, Dynamic melt microparticles are added to the EPS mixed raw material; the mixture is compounded using a twin-screw extruder, with the extrusion temperature controlled at 140-160℃, the screw speed maintained in the range of 40-60 RPM, and the outlet pressure in the range of 0.1-0.2 MPa, to obtain microparticle filler; S3, hydrogel embedding of the microparticle filler: Sodium alginate and agar are dissolved in a water bath at 60-70℃, and calcium chloride and melamine are added at a stirring speed of 300-400 RPM, and stirring is continued for 15-25 min to form a gel matrix; the microparticle filler is immersed in the gel matrix to ensure full contact between the surface of the EPS particles and the gel matrix, and the immersion time is controlled between 5-10 min; then, it is dried at a constant temperature of 40-50℃ using a forced-air drying oven to obtain the hydrogel embedding material. The hydrogel embedding material is dried to form a foam insulation board.

2. The method for preparing EPS foam insulation board according to claim 1, characterized in that, Also includes: S4, heating and foaming: The hydrogel embedding material is fed into a continuous foaming machine, and the internal temperature is maintained in the range of 100-120℃ by steam heating, and the pressure is in the range of 0.2-0.3 MPa; the foaming time is set to 30-60 min, and the hydrogel and EPS particles expand together under the action of heat to form a porous structure, thus obtaining preliminary foam. S5, the preliminary foam is fed into a heating furnace, the temperature is set at 60-80℃, the blower speed is controlled at 0.3-0.5m / s; the conveyor belt speed is maintained at 0.5-1 m / min, and the preliminary foam stays in the furnace for 15-25 min to obtain the preliminary low-temperature extended material; S6. The temperature of the heating furnace is further increased to 120-160℃ and maintained for 20-40 minutes to allow the material to complete the cross-linking and curing process, resulting in cross-linked foam.

3. The method for preparing EPS foam insulation board according to claim 2, characterized in that, Also includes: S7, the cross-linked foam is fed into a flat pressing mold, the mold temperature is maintained in the range of 30-40℃, and a molding pressure of 0.1-0.2 MPa is applied; the pressing time is controlled at 10-20 min according to the thickness of the board to obtain a cured board; S8. Perform surface spraying and hardening treatment on the cured board; control the spray gun pressure in the range of 0.2-0.3 MPa, spray interval of 5-10 min, repeat 2-5 times; after standing for 30-60 min, send the board into a UV curing unit or hot air curing box for curing, maintain the temperature in the range of 40-60℃, and control the time in the range of 2-3 h; obtain flame-retardant EPS insulation board.

4. The method for preparing EPS foam insulation board according to claim 1, characterized in that: In step S1, the flame retardant is a mixture of melamine, antimony trioxide, brominated polystyrene, and phosphorus pentoxide in a mass ratio of 2-3:1-2:1-4:1-2; the antioxidant is a mixture of tert-butylhydroquinone, propyl gallate, BHT, and vitamin E in a mass ratio of 1-3:1-3:1-3:1-3; and the additives are a mixture of calcium stearate, polyethylene glycol, polyacrylamide, and sodium dodecyl sulfate in a mass ratio of 2-3:1-2:1-4:1-2.

5. The method for preparing EPS foam insulation board according to claim 1, characterized in that: In step S2, the dynamic molten microparticles are composed of polypropylene, talc, calcium carbonate and glass fiber in a mass ratio of 2-3:1-2:1-4:1-2.

6. The method for preparing EPS foam insulation board according to claim 1, characterized in that: In step S3, the hydrogel is composed of sodium alginate, agar, calcium chloride and melamine in a mass ratio of 2-3:2-3:1-2:1-2.

7. The method for preparing EPS foam insulation board according to claim 3, characterized in that: In step S8, the sprayed material consists of a fire-retardant coating and a scratch-resistant resin. The fire-retardant coating is composed of aluminum hydroxide, flame-retardant ammonium polyphosphate, melamine-formaldehyde resin and silicone-acrylic emulsion in a mass ratio of 2-3:1-2:1-4:1-2. The scratch-resistant resin is composed of polyurethane and a curing agent in a mass ratio of 2-4:1-3.

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