A continuous foaming preparation process of a microstructure-regulated high and low temperature resistant flame-retardant organic silicon foam

Abstract

The application belongs to the field of silicone foam cotton preparation, and particularly relates to a continuous foaming preparation process of a microstructure-regulated high and low temperature resistant flame-retardant silicone foam cotton, wherein the silicone foam cotton is prepared by blending and reacting component A and component B at a mass ratio of 1:1; component A comprises the following raw materials: hydroxyl-terminated polydimethylsiloxane, hydroxyl silicone oil, fumed silica, powder aluminum hydroxide, a catalyst and color paste; component B comprises the following raw materials: hydroxyl-terminated polydimethylsiloxane, hydrogen-containing silicone oil, an inhibitor and powder aluminum hydroxide; the silicone foam cotton prepared by the application has excellent comprehensive performance, is resistant to high and low temperatures in a wide temperature range, has stable flame-retardant performance, good mechanical performance and elastic recovery performance, and has uniform and fine pores, and has high performance consistency between batches; the silicone foam cotton can be widely applied to the fields of sealing protection of new energy automobile battery systems, edge sealing of photovoltaic modules, heat insulation protection of energy storage equipment, potting and filling of aerospace electronic devices, and the like, and can completely replace imported similar products, thereby reducing application cost.

Description

Technical Field

[0001] This invention belongs to the field of silicone foam preparation, specifically relating to a continuous foaming preparation process for microstructure-controlled high and low temperature flame-retardant silicone foam. Background Technology

[0002] Organosilicon materials, with silicon-oxygen bonds as the main chain, combine the high and low temperature resistance and aging resistance of inorganic materials with the flexibility and processability of organic materials, making them core basic materials in new energy, electronics, aerospace, and other fields. Liquid silicone rubber foam, as an important branch of organosilicon materials, is a key supporting material in these fields due to its lightweight, good elasticity, and excellent sealing and protective properties. However, existing preparation technologies face several bottlenecks: First, formulation design flaws: high molecular weight silicone raw rubber is often used to prepare foam, and there is limited research on the application of liquid room temperature vulcanizing silicone rubber. Furthermore, catalysts and foaming aids are not separated and configured, leading to premature cross-linking and poor storage stability of components A and B. Flame retardants are often added alone, resulting in poor compatibility with the silicone rubber matrix, easily causing uneven cell structure and decreased mechanical properties, making it difficult to maintain both flame retardancy and low density characteristics. Second, insufficient product performance: existing products have limited high and low temperature resistance, failing to meet the requirements for wide temperature range use (-50-200℃), and their flame retardancy stability is poor, with the flame retardancy rating easily decreasing after high-temperature aging, significantly affecting their application in demanding fields, necessitating urgent improvement. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a continuous foaming preparation process for microstructure-controlled high and low temperature flame-retardant silicone foam.

[0004] The present invention adopts the following technical solution:

[0005] A continuous foaming preparation process for microstructure-controlled high and low temperature flame-retardant silicone foam, wherein the silicone foam is prepared by mass blending of component A and component B in a 1:1 ratio.

[0006] Component A comprises the following raw materials in parts by weight: 60-80 parts of hydroxyl-terminated polydimethylsiloxane, 5-10 parts of hydroxyl silicone oil, 3-8 parts of fumed silica, 10-15 parts of powdered aluminum hydroxide, 0.05-2 parts of catalyst, and 0.5-2 parts of color paste.

[0007] Component B comprises the following raw materials in parts by weight: 60-80 parts of hydroxyl-terminated polydimethylsiloxane, 0.1-0.3 parts of hydrogen-containing silicone oil, 0.01-0.05 parts of inhibitor, and 5-10 parts of powdered aluminum hydroxide. The inhibitor comprises the following raw materials in parts by weight: 85-95 parts of 1-ethynylcyclohexanol and 5-15 parts of 2-methyl-3-butyn-2-ol.

[0008] The preparation process of the silicone foam specifically includes the following steps:

[0009] Step 1: Prepare component A and component B separately;

[0010] Step 2: Component A and component B are delivered to the mixer at a mass ratio of 1:1 via a metering pump and mixed at a speed of 1500-2000 rpm for 3-5 minutes. During the mixing process, a water-cooled jacket is used to control the temperature of the mixed rubber compound to maintain the temperature at 25-30℃.

[0011] Step 3: The blended material is fed into a calender and calendered to form a composite roll by double-sided composite release film.

[0012] Step 4: Place the composite roll into the oven and use a gradient heating mode. The total vulcanization and foaming time is 15-20 minutes. The temperature zones are set as follows: preheating zone 120-140℃, foaming and cross-linking zone 160-180℃, and cross-linking and shaping zone 150-160℃.

[0013] Step 5: The foam blank obtained in step 4 is placed in an oven and dried for 1-2 hours at 100-120℃. Then it is cooled to room temperature at a rate of 5-10℃ / min. After peeling off the release film, the silicone foam is obtained.

[0014] Preferably, in step 1, the preparation process of component A is as follows:

[0015] A. The fumed silica and powdered aluminum hydroxide were sieved separately, and then dried at 80℃ for 2-4 hours until the moisture content was ≤0.1%;

[0016] B. Place hydroxyl-terminated polydimethylsiloxane and hydroxyl silicone oil at 25±5℃ for 1-2 hours and adjust the viscosity to 5000-10000 mPa·s.

[0017] C. Disperse the color paste and a portion of the pretreated hydroxyl silicone oil at 1000-1500 rpm for 5-10 minutes to obtain a color paste premix.

[0018] D. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the remaining hydroxyl silicone oil at a speed of 300-500 rpm, and stir for 10-15 min.

[0019] E. Increase the rotation speed to 800-1000 rpm, add the pretreated fumed silica and powdered aluminum hydroxide in three separate additions, stirring and mixing for 15 minutes after each addition, add the color paste premix, mix and stir evenly, then reduce the rotation speed to 200-300 rpm, add the catalyst, and mix and stir for 8-10 minutes to obtain component A.

[0020] Preferably, in step C, the amount of hydroxyl silicone oil added is 1 / 4 of its weight.

[0021] Preferably, in step 1, the preparation process of component B is as follows:

[0022] S1. Sift the powdered aluminum hydroxide, then dry it at 80℃ for 2-4 hours until the moisture content is ≤0.1%;

[0023] S2. Place hydroxyl-terminated polydimethylsiloxane and hydrogen-containing silicone oil at 25±5℃ for 1-2 hours and adjust the viscosity to 5000-10000 mPa·s.

[0024] S3. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the pretreated hydrogen-containing silicone oil at a speed of 300-500 rpm. Stir for 10-15 minutes.

[0025] S4. Continue to add inhibitor and powdered aluminum hydroxide to the reactor, mix and stir for 20-30 minutes to obtain component B.

[0026] Preferably, in step 4, the crosslinking time of the preheating section is 3-5 min, the crosslinking time of the foaming crosslinking section is 7-8 min, and the crosslinking and shaping section is 5-7 min.

[0027] Preferably, in step 3, the thickness of the composite roll is ≤3mm.

[0028] As can be seen from the above description of the present invention, compared with the prior art, the beneficial effects of the present invention are as follows: the apparent density of the silicone foam prepared by the present invention is as low as 305.2 kg / m³, the average tensile strength is as high as 338 kPa, the permanent compression deformation is ≤5%, and it can be used stably in environments ranging from -50 to 200℃; it shows no cracks after aging at 200℃ for 72 hours and no cracks after bending 180° after aging at -40℃ for 72 hours; its flame retardant performance is stable, and it still maintains UL94 V-0 after aging at 70℃ for 168 hours; its overall comprehensive performance is excellent, and it can be adapted to high-end applications in a wide temperature range, fully meeting the application requirements of high-end fields such as new energy vehicles, photovoltaics, and energy storage; among them, component A and component B are formulated separately, separating the catalyst from the crosslinking agent and foaming agent, effectively preventing premature crosslinking, and component A and component B have good storage stability, with a storage period of ≥6 months at room temperature. For several months, a uniform adhesive system was provided for subsequent reactions; and the composition of the inhibitor was further defined, consisting of 1-ethynylcyclohexanol and 2-methyl-3-butyn-2-ol, to control the reaction rate and prevent premature crosslinking; at the same time, the content of each component was precisely controlled in conjunction with a specific preparation process to achieve a precise match between the foaming rate and the crosslinking rate, forming a continuous, dense, and tough flame-retardant skeleton in the cell walls inside the product, making the microstructure of the silicone foam uniform and controllable, and rapidly forming a complete heat-insulating char layer that does not crack, drip, or smolder during combustion, fundamentally solving the problem of flame retardancy fluctuation in 300kg / m³ density foam, and stabilizing the total afterburning time within 50s to ensure that the flame retardancy rating reaches UL94 V-0; among them, the aluminum hydroxide-fumed silica flame retardant synergistic system, under the premise of ensuring UL94 V-0, improves the compatibility between the flame retardant and the matrix, taking into account both low density and excellent mechanical properties;

[0029] The specific manufacturing process for silicone foam is fully automated and continuous, ensuring high batch consistency and suitability for large-scale production. The gradient temperature-controlled vulcanization and foaming crosslinking process, combined with subsequent secondary baking and shaping, and gradient cooling, effectively solves problems such as uneven cell size, localized bubbling, and delamination. This results in silicone foam with fine and uniform cell size and good batch-to-batch performance consistency. The 120-140℃ preheating section enables initial crosslinking of the adhesive, generating microbubbles to prepare for foaming; the 160-180℃ foaming and crosslinking section allows for rapid bubble formation. Expansion forms cells, and the cross-linking rate increases simultaneously, gradually solidifying the cell walls to form a stable cell structure. The cross-linking and setting section at 150-160℃ slows down the foaming reaction, allowing the cross-linking reaction to proceed fully, further solidifying the cell walls, improving mechanical properties, preventing cell collapse and product shrinkage, and thus ensuring the overall performance of the prepared silicone foam. Secondary baking and setting eliminates residual stress inside the product, stabilizes the cell structure, and prevents subsequent shrinkage and cracking. At the same time, combined with subsequent gradient cooling, it avoids thermal stress caused by sudden cooling, which can lead to surface cracking and cell deformation.

[0030] When preparing components A and B, some raw materials are pretreated to remove impurities and adjust their state, ensuring the uniformity of the subsequent reaction and avoiding uneven cell structure and performance degradation due to poor raw material state. This also prevents the absence of additional bubbles during the subsequent foaming process, thus ensuring the performance of the prepared silicone foam. Attached Figure Description

[0031] Figure 1 Here are graphs showing the trends of apparent density and tensile strength for each embodiment;

[0032] Figure 2 For each embodiment, a permanent deformation trend diagram is provided;

[0033] Figure 3 This is a scanning electron microscope image of the silicone foam prepared in Example 1;

[0034] Figure 4 This is a schematic diagram of the microstructure of the silicone foam prepared in Example 1;

[0035] Figure 5 Images of the silicone foams prepared in Examples 1-5 before the UL94 flame retardancy test;

[0036] Figure 6 Images of silicone foam samples prepared in Examples 1-5 after UL94 flame retardancy testing. Detailed Implementation

[0037] The present invention will be further described below through specific embodiments.

[0038] A microstructure-controlled, high- and low-temperature resistant, flame-retardant silicone foam is prepared by a 1:1 mass blending reaction of component A and component B. Component A comprises the following raw materials in parts by weight: 60-80 parts hydroxyl-terminated polydimethylsiloxane, 5-10 parts hydroxyl silicone oil, 3-8 parts fumed silica, 10-15 parts aluminum hydroxide powder, 0.05-2 parts 5000ppm platinum catalyst, and 0.5-2 parts colorant. Component B comprises the following raw materials in parts by weight: 60-80 parts hydroxyl-terminated polydimethylsiloxane, 0.1-0.3 parts hydrogen-containing silicone oil, 0.01-0.05 parts inhibitor, and 5-10 parts aluminum hydroxide powder. Specifically, the inhibitor comprises the following raw materials in parts by weight: 85-95 parts 1-ethynylcyclohexanol and 5-15 parts 2-methyl-3-butyn-2-ol; the fumed silica is 300-mesh fumed silica.

[0039] Its continuous foaming preparation process specifically includes the following steps:

[0040] Step 1, Prepare component A:

[0041] A. The fumed silica and powdered aluminum hydroxide were sieved separately, and then dried at 80℃ for 2-4 hours until the moisture content was ≤0.1%;

[0042] B. Place hydroxyl-terminated polydimethylsiloxane and hydroxyl silicone oil at 25±5℃ for 1-2 hours and adjust the viscosity to 5000-10000 mPa·s.

[0043] C. Disperse the color paste with 1 / 4 of the pretreated hydroxyl silicone oil at 1000-1500 rpm for 5-10 min to obtain the color paste premix.

[0044] D. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the remaining hydroxyl silicone oil at a speed of 300-500 rpm, and stir for 10-15 min.

[0045] E. Increase the rotation speed to 800-1000 rpm, add the pretreated fumed silica and powdered aluminum hydroxide in three separate additions, stirring and mixing for 15 minutes after each addition, add the color paste premix, mix and stir evenly, then reduce the rotation speed to 200-300 rpm, add the catalyst, and mix and stir for 8-10 minutes to obtain component A.

[0046] Step 2, prepare component B:

[0047] S1. Sift the powdered aluminum hydroxide, then dry it at 80℃ for 2-4 hours until the moisture content is ≤0.1%;

[0048] S2. Place hydroxyl-terminated polydimethylsiloxane and hydrogen-containing silicone oil at 25±5℃ for 1-2 hours and adjust the viscosity to 5000-10000 mPa·s.

[0049] S3. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the pretreated hydrogen-containing silicone oil at a speed of 300-500 rpm. Stir for 10-15 minutes.

[0050] S4. Continue to add inhibitor and powdered aluminum hydroxide to the reactor, mix and stir for 20-30 minutes to obtain component B;

[0051] Step 3: Component A and component B are delivered to the mixer at a mass ratio of 1:1 via a metering pump and mixed at a speed of 1500-2000 rpm for 3-5 minutes. During the mixing process, a water-cooled jacket is used to control the temperature of the mixed rubber compound to maintain the temperature at 25-30℃.

[0052] Step 4: The blended material is fed into a calender and calendered to form a double-sided composite release film to form a composite roll. The roller temperature of the calender is 30±5℃, and the roller gap is set to press the rubber material to a thickness of 3mm. The calendering accuracy error is ≤±0.1mm.

[0053] Step 5: Place the composite roll into the oven and use a gradient heating mode. The total vulcanization and foaming time is 15-20 minutes. The temperature zones are set as follows: preheating section 120-140℃, foaming and cross-linking section 160-180℃, cross-linking and shaping section 150-160℃. The cross-linking time in the preheating section is 3-5 minutes, the cross-linking time in the foaming and cross-linking section is 7-8 minutes, and the cross-linking time in the cross-linking and shaping section is 5-7 minutes.

[0054] Step 6: The foam blank obtained in step 4 is placed in an oven and dried for 1-2 hours at 100-120℃. Then it is cooled to room temperature at a rate of 5-10℃ / min. After peeling off the release film, the silicone foam is obtained.

[0055] Example 1

[0056] A high- and low-temperature resistant flame-retardant silicone foam is prepared by reacting component A and component B in a 1:1 mass ratio. Component A includes the following raw materials in parts by weight: 70 parts hydroxyl-terminated polydimethylsiloxane, 8 parts hydroxyl silicone oil, 5 parts fumed silica, 12 parts aluminum hydroxide powder, 0.1 parts 5000ppm platinum catalyst, and 1 part color paste. Component B includes the following raw materials in parts by weight: 70 parts hydroxyl-terminated polydimethylsiloxane, 0.2 parts hydrogen-containing silicone oil, 0.03 parts inhibitor, and 8 parts aluminum hydroxide powder. Specifically, the inhibitor includes the following raw materials in parts by weight: 90 parts 1-ethynylcyclohexanol and 10 parts 2-methyl-3-butyn-2-ol.

[0057] Its continuous foaming preparation process specifically includes the following steps:

[0058] Step 1, Prepare component A:

[0059] A. The fumed silica and powdered aluminum hydroxide were sieved separately, and then dried at 80°C for 3 hours until the moisture content was 0.08%.

[0060] B. Place hydroxyl-terminated polydimethylsiloxane and hydroxyl silicone oil at 30°C for 1.5 hours and adjust the viscosity to 8000 mPa·s.

[0061] C. Disperse the color paste with 1 / 4 of the pretreated hydroxyl silicone oil at 1200 rpm for 8 min to obtain the color paste premix.

[0062] D. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the remaining hydroxyl silicone oil at a speed of 400 rpm, and stir for 12 min.

[0063] E. Increase the rotation speed to 900 rpm, add the pretreated fumed silica and powdered aluminum hydroxide in three separate additions, stirring and mixing for 15 minutes after each addition, add the color paste premix, mix and stir evenly, then reduce the rotation speed to 250 rpm, add the catalyst, mix and stir for 9 minutes to obtain component A.

[0064] Step 2, prepare component B:

[0065] S1. The powdered aluminum hydroxide is sieved and then dried at 80°C for 3 hours until the moisture content is 0.08%.

[0066] S2. Place hydroxyl-terminated polydimethylsiloxane and hydrogen-containing silicone oil at 30°C for 1.5 hours and adjust the viscosity to 8000 mPa·s.

[0067] S3. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the pretreated hydrogen-containing silicone oil at 400 rpm. Stir for 12 min.

[0068] S4. Continue to add inhibitor and powdered aluminum hydroxide to the reactor, mix and stir for 25 minutes to obtain component B;

[0069] Step 3: Component A and component B are delivered to the mixer at a mass ratio of 1:1 via a metering pump and mixed at a speed of 1800 rpm for 4 minutes. During the mixing process, a water-cooled jacket is used to control the temperature of the mixed rubber compound to maintain the temperature at 28°C.

[0070] Step 4: The blended material is fed into a calender and calendered to form a double-sided composite release film to form a composite roll. The roller temperature of the calender is 30°C, and the roller gap is set to press the rubber material to a thickness of 3mm. The calendering accuracy error is ≤±0.08mm.

[0071] Step 5: The composite roll is placed in the oven and a gradient heating mode is adopted. The total vulcanization and foaming time is 18 minutes. The temperature zones are set as follows: 130°C for the preheating section, 170°C for the foaming and cross-linking section, and 155°C for the cross-linking and shaping section. The cross-linking time for the preheating section is 4 minutes, the cross-linking time for the foaming and cross-linking section is 8 minutes, and the cross-linking time for the cross-linking and shaping section is 6 minutes.

[0072] Step 6: The foam blank obtained in step 4 is placed in an oven and dried for 1.5 hours at 110°C. Then it is cooled to room temperature at a rate of 8°C / min. After peeling off the release film, the silicone foam is obtained.

[0073] Continuous production length is 350m.

[0074] Example 2

[0075] A high- and low-temperature resistant flame-retardant silicone foam is prepared by reacting component A and component B in a 1:1 mass ratio. Component A includes the following raw materials in parts by weight: 60 parts hydroxyl-terminated polydimethylsiloxane, 5 parts hydroxyl silicone oil, 3 parts fumed silica, 10 parts aluminum hydroxide powder, 0.05 parts 5000ppm platinum catalyst, and 0.5 parts color paste. Component B includes the following raw materials in parts by weight: 60 parts hydroxyl-terminated polydimethylsiloxane, 0.1 parts hydrogen-containing silicone oil, 0.01 parts inhibitor, and 5 parts aluminum hydroxide powder. Specifically, the inhibitor includes the following raw materials in parts by weight: 85 parts 1-ethynylcyclohexanol and 15 parts 2-methyl-3-butyn-2-ol.

[0076] Its continuous foaming preparation process specifically includes the following steps:

[0077] Step 1, Prepare component A:

[0078] A. The fumed silica and powdered aluminum hydroxide were sieved separately, and then dried at 80°C for 2 hours until the moisture content was 0.09%.

[0079] B. Place hydroxyl-terminated polydimethylsiloxane and hydroxyl silicone oil at 30°C for 1 hour and adjust the viscosity to 7000 mPa·s.

[0080] C. Disperse the color paste with 1 / 4 of the pretreated hydroxyl silicone oil at 1200 rpm for 8 min to obtain the color paste premix.

[0081] D. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the remaining hydroxyl silicone oil at a speed of 400 rpm, and stir for 12 min.

[0082] E. Increase the rotation speed to 900 rpm, add the pretreated fumed silica and powdered aluminum hydroxide in three separate additions, stirring and mixing for 15 minutes after each addition, add the color paste premix, mix and stir evenly, then reduce the rotation speed to 250 rpm, add the catalyst, mix and stir for 9 minutes to obtain component A.

[0083] Step 2, prepare component B:

[0084] S1. The powdered aluminum hydroxide is sieved and then dried at 80℃ for 2 hours until the moisture content is 0.09%.

[0085] S2. Place hydroxyl-terminated polydimethylsiloxane and hydrogen-containing silicone oil at 30°C for 1 hour and adjust the viscosity to 7000 mPa·s.

[0086] S3. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the pretreated hydrogen-containing silicone oil at 400 rpm. Stir for 12 min.

[0087] S4. Continue to add inhibitor and powdered aluminum hydroxide to the reactor, mix and stir for 25 minutes to obtain component B;

[0088] Step 3: Component A and component B are delivered to the mixer at a mass ratio of 1:1 via a metering pump and mixed at a speed of 1500 rpm for 5 minutes. During the mixing process, a water-cooled jacket is used to control the temperature of the mixed rubber compound to maintain the temperature at 25°C.

[0089] Step 4: The blended material is fed into a calender and calendered to form a double-sided composite release film to form a composite roll. The roller temperature of the calender is 25°C, and the roller gap is set to press the rubber material to a thickness of 3mm. The calendering accuracy error is ≤±0.09mm.

[0090] Step 5: Send the composite roll into the oven and use a gradient heating mode. The total vulcanization and foaming time is 15 minutes. The temperature zones are set as follows: 120°C for the preheating section, 160°C for the foaming and cross-linking section, and 150°C for the cross-linking and shaping section. The cross-linking time for the preheating section is 3 minutes, the cross-linking time for the foaming and cross-linking section is 7 minutes, and the cross-linking time for the cross-linking and shaping section is 5 minutes.

[0091] Step 6: The foam blank obtained in step 4 is placed in an oven and dried for 2 hours at 100°C. Then it is cooled to room temperature at a rate of 5°C / min. After peeling off the release film, the silicone foam is obtained.

[0092] The continuous production length is 320m.

[0093] Example 3

[0094] A high- and low-temperature resistant flame-retardant silicone foam is prepared by a 1:1 mass blending reaction of component A and component B. Component A comprises the following raw materials in parts by weight: 80 parts hydroxyl-terminated polydimethylsiloxane, 10 parts hydroxyl silicone oil, 8 parts fumed silica, 15 parts aluminum hydroxide powder, 0.2 parts 5000ppm platinum catalyst, and 2 parts color paste. Component B comprises the following raw materials in parts by weight: 80 parts hydroxyl-terminated polydimethylsiloxane, 0.3 parts hydrogen-containing silicone oil, 0.05 parts inhibitor, and 10 parts aluminum hydroxide powder. Specifically, the inhibitor comprises the following raw materials in parts by weight: 95 parts 1-ethynylcyclohexanol and 5 parts 2-methyl-3-butyn-2-ol.

[0095] Its continuous foaming preparation process specifically includes the following steps:

[0096] Step 1, Prepare component A:

[0097] A. The fumed silica and powdered aluminum hydroxide were sieved separately, and then dried at 80°C for 4 hours until the moisture content was 0.07%.

[0098] B. Place hydroxyl-terminated polydimethylsiloxane and hydroxyl silicone oil at 30°C for 2 hours and adjust the viscosity to 9000 mPa·s.

[0099] C. Disperse the color paste with 1 / 4 of the pretreated hydroxyl silicone oil at 1200 rpm for 8 min to obtain the color paste premix.

[0100] D. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the remaining hydroxyl silicone oil at a speed of 400 rpm, and stir for 12 min.

[0101] E. Increase the rotation speed to 900 rpm, add the pretreated fumed silica and powdered aluminum hydroxide in three separate additions, stirring and mixing for 15 minutes after each addition, add the color paste premix, mix and stir evenly, then reduce the rotation speed to 250 rpm, add the catalyst, mix and stir for 9 minutes to obtain component A.

[0102] Step 2, prepare component B:

[0103] S1. The powdered aluminum hydroxide is sieved and then dried at 80°C for 4 hours until the moisture content is 0.07%.

[0104] S2. Place hydroxyl-terminated polydimethylsiloxane and hydrogen-containing silicone oil at 30°C for 2 hours and adjust the viscosity to 9000 mPa·s.

[0105] S3. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the pretreated hydrogen-containing silicone oil at 400 rpm. Stir for 12 min.

[0106] S4. Continue to add inhibitor and powdered aluminum hydroxide to the reactor, mix and stir for 25 minutes to obtain component B;

[0107] Step 3: Component A and component B are delivered to the mixer at a mass ratio of 1:1 via a metering pump and mixed at a speed of 2000 rpm for 3 minutes. During the mixing process, a water-cooled jacket is used to control the temperature of the mixed rubber compound to maintain the temperature at 30°C.

[0108] Step 4: The blended material is fed into a calender and calendered to form a composite roll by double-sided composite release film. The roller temperature of the calender is 35°C, and the roller gap is set to press the rubber material to a thickness of 3mm. The calendering accuracy error is ≤±0.07mm.

[0109] Step 5: Send the composite roll into the oven and use a gradient heating mode. The total vulcanization and foaming time is 20 minutes. The temperature zones are set as follows: 140°C for the preheating section, 180°C for the foaming and cross-linking section, and 160°C for the cross-linking and shaping section. The cross-linking time for the preheating section is 5 minutes, the cross-linking time for the foaming and cross-linking section is 8 minutes, and the cross-linking time for the cross-linking and shaping section is 7 minutes.

[0110] Step 6: The foam blank obtained in step 4 is placed in an oven and dried for a second time at 120°C for 1 hour. Then it is cooled to room temperature at a rate of 10°C / min. After peeling off the release film, the silicone foam is obtained.

[0111] Continuous production length is 300m.

[0112] Example 4

[0113] A high- and low-temperature resistant flame-retardant silicone foam is prepared by reacting component A and component B in a 1:1 mass ratio. Component A includes the following raw materials in parts by weight: 65 parts hydroxyl-terminated polydimethylsiloxane, 6 parts hydroxyl silicone oil, 4 parts fumed silica, 11 parts aluminum hydroxide powder, 0.08 parts 5000ppm platinum catalyst, and 0.8 parts color paste. Component B includes the following raw materials in parts by weight: 65 parts hydroxyl-terminated polydimethylsiloxane, 0.15 parts hydrogen-containing silicone oil, 0.02 parts inhibitor, and 6 parts aluminum hydroxide powder. Specifically, the inhibitor includes the following raw materials in parts by weight: 90 parts 1-ethynylcyclohexanol and 10 parts 2-methyl-3-butyn-2-ol.

[0114] Its continuous foaming preparation process specifically includes the following steps:

[0115] Step 1, Prepare component A:

[0116] A. The fumed silica and powdered aluminum hydroxide were sieved separately, and then dried at 80°C for 2.5 hours until the moisture content was 0.085%.

[0117] B. Place hydroxyl-terminated polydimethylsiloxane and hydroxyl silicone oil at 30°C for 1.2 hours and adjust the viscosity to 7500 mPa·s.

[0118] C. Disperse the color paste with 1 / 4 of the pretreated hydroxyl silicone oil at 1200 rpm for 8 min to obtain the color paste premix.

[0119] D. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the remaining hydroxyl silicone oil at a speed of 400 rpm, and stir for 12 min.

[0120] E. Increase the rotation speed to 900 rpm, add the pretreated fumed silica and powdered aluminum hydroxide in three separate additions, stirring and mixing for 15 minutes after each addition, add the color paste premix, mix and stir evenly, then reduce the rotation speed to 250 rpm, add the catalyst, mix and stir for 9 minutes to obtain component A.

[0121] Step 2, prepare component B:

[0122] S1. The powdered aluminum hydroxide is sieved and then dried at 80℃ for 2.5 hours until the moisture content is 0.085%.

[0123] S2. Place hydroxyl-terminated polydimethylsiloxane and hydrogen-containing silicone oil at 30°C for 1.2 hours and adjust the viscosity to 7500 mPa·s.

[0124] S3. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the pretreated hydrogen-containing silicone oil at 400 rpm. Stir for 12 min.

[0125] S4. Continue to add inhibitor and powdered aluminum hydroxide to the reactor, mix and stir for 25 minutes to obtain component B;

[0126] Step 3: Component A and component B are delivered to the mixer at a mass ratio of 1:1 via a metering pump and mixed at a speed of 1600 rpm for 4.5 minutes. During the mixing process, a water-cooled jacket is used to control the temperature of the mixed rubber compound to maintain the temperature at 26°C.

[0127] Step 4: The blended material is fed into a calender and calendered to form a double-sided composite release film to form a composite roll. The roller temperature of the calender is 28°C, and the roller gap is set to press the rubber material to a thickness of 3mm. The calendering accuracy error is ≤±0.085mm.

[0128] Step 5: Place the composite roll into the oven and use a gradient heating mode. The total vulcanization and foaming time is 16 minutes. The temperature zones are set as follows: preheating section 125℃, foaming and cross-linking section 165℃, cross-linking and shaping section 152℃. The cross-linking time in the preheating section is 3.5 minutes, the cross-linking time in the foaming and cross-linking section is 7.5 minutes, and the cross-linking time in the cross-linking and shaping section is 5 minutes.

[0129] Step 6: The foam blank obtained in step 4 is placed in an oven and dried for 1.8 hours at 105°C. Then it is cooled to room temperature at a rate of 6°C / min. After peeling off the release film, the silicone foam is obtained.

[0130] The continuous production length is 330m.

[0131] Example 5

[0132] A high- and low-temperature resistant flame-retardant silicone foam is prepared by reacting component A and component B in a 1:1 mass ratio. Component A includes the following raw materials in parts by weight: 75 parts hydroxyl-terminated polydimethylsiloxane, 9 parts hydroxyl silicone oil, 7 parts fumed silica, 14 parts aluminum hydroxide powder, 0.15 parts 5000ppm platinum catalyst, and 1.5 parts color paste. Component B includes the following raw materials in parts by weight: 75 parts hydroxyl-terminated polydimethylsiloxane, 0.25 parts hydrogen-containing silicone oil, 0.04 parts inhibitor, and 9 parts aluminum hydroxide powder. Specifically, the inhibitor includes the following raw materials in parts by weight: 90 parts 1-ethynylcyclohexanol and 10 parts 2-methyl-3-butyn-2-ol.

[0133] Its continuous foaming preparation process specifically includes the following steps:

[0134] Step 1, Prepare component A:

[0135] A. The fumed silica and powdered aluminum hydroxide were sieved separately, and then dried at 80°C for 3.5 hours until the moisture content was 0.075%.

[0136] B. Place hydroxyl-terminated polydimethylsiloxane and hydroxyl silicone oil at 30°C for 1.8 hours and adjust the viscosity to 8500 mPa·s.

[0137] C. Disperse the color paste with 1 / 4 of the pretreated hydroxyl silicone oil at 1200 rpm for 8 min to obtain the color paste premix.

[0138] D. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the remaining hydroxyl silicone oil at a speed of 400 rpm, and stir for 12 min.

[0139] E. Increase the rotation speed to 900 rpm, add the pretreated fumed silica and powdered aluminum hydroxide in three separate additions, stirring and mixing for 15 minutes after each addition, add the color paste premix, mix and stir evenly, then reduce the rotation speed to 250 rpm, add the catalyst, mix and stir for 9 minutes to obtain component A.

[0140] Step 2, prepare component B:

[0141] S1. The powdered aluminum hydroxide is sieved and then dried at 80℃ for 1.8 hours until the moisture content is 0.075%.

[0142] S2. Place hydroxyl-terminated polydimethylsiloxane and hydrogen-containing silicone oil at 30°C for 1.8 hours and adjust the viscosity to 8500 mPa·s.

[0143] S3. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the pretreated hydrogen-containing silicone oil at 400 rpm. Stir for 12 min.

[0144] S4. Continue to add inhibitor and powdered aluminum hydroxide to the reactor, mix and stir for 25 minutes to obtain component B;

[0145] Step 3: Component A and component B are delivered to the mixer at a mass ratio of 1:1 via a metering pump and mixed at a speed of 1900 rpm for 3.5 minutes. During the mixing process, a water-cooled jacket is used to control the temperature of the mixed rubber compound to maintain it at 29°C.

[0146] Step 4: The blended material is fed into a calender and calendered to form a double-sided composite release film to form a composite roll. The roller temperature of the calender is 32℃, and the roller gap is set to press the rubber material to a thickness of 3mm. The calendering accuracy error is ≤±0.075mm.

[0147] Step 5: The composite roll is placed in the oven and a gradient heating mode is adopted. The total vulcanization and foaming time is 19 minutes. The temperature zones are set as follows: 135°C for the preheating section, 175°C for the foaming and cross-linking section, and 158°C for the cross-linking and shaping section. The cross-linking time for the preheating section is 4 minutes, the cross-linking time for the foaming and cross-linking section is 8 minutes, and the cross-linking time for the cross-linking and shaping section is 7 minutes.

[0148] Step 6: The foam blank obtained in step 4 is placed in an oven and dried for 1.2 hours at 115°C. Then it is cooled to room temperature at a rate of 9°C / min. After peeling off the release film, the silicone foam is obtained.

[0149] The continuous production length is 340m.

[0150] Example 6

[0151] A high- and low-temperature resistant flame-retardant silicone foam is prepared by reacting component A and component B in a 1:1 mass ratio. Component A includes the following raw materials in parts by weight: 72 parts hydroxyl-terminated polydimethylsiloxane, 7 parts hydroxyl silicone oil, 6 parts fumed silica, 13 parts aluminum hydroxide powder, 0.12 parts 5000ppm platinum catalyst, and 1.2 parts color paste. Component B includes the following raw materials in parts by weight: 72 parts hydroxyl-terminated polydimethylsiloxane, 0.18 parts hydrogen-containing silicone oil, 0.035 parts inhibitor, and 7 parts aluminum hydroxide powder. Specifically, the inhibitor includes the following raw materials in parts by weight: 90 parts 1-ethynylcyclohexanol and 10 parts 2-methyl-3-butyn-2-ol.

[0152] Its continuous foaming preparation process specifically includes the following steps:

[0153] Step 1, Prepare component A:

[0154] A. The fumed silica and powdered aluminum hydroxide were sieved separately, and then dried at 80°C for 3 hours until the moisture content was 0.08%.

[0155] B. Place hydroxyl-terminated polydimethylsiloxane and hydroxyl silicone oil at 30°C for 1.5 hours and adjust the viscosity to 8200 mPa·s.

[0156] C. Disperse the color paste with 1 / 4 of the pretreated hydroxyl silicone oil at 1200 rpm for 8 min to obtain the color paste premix.

[0157] D. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the remaining hydroxyl silicone oil at a speed of 400 rpm, and stir for 12 min.

[0158] E. Increase the rotation speed to 900 rpm, add the pretreated fumed silica and powdered aluminum hydroxide in three separate additions, stirring and mixing for 15 minutes after each addition, add the color paste premix, mix and stir evenly, then reduce the rotation speed to 250 rpm, add the catalyst, mix and stir for 9 minutes to obtain component A.

[0159] Step 2, prepare component B:

[0160] S1. The powdered aluminum hydroxide is sieved and then dried at 80°C for 3 hours until the moisture content is 0.08%.

[0161] S2. Place hydroxyl-terminated polydimethylsiloxane and hydrogen-containing silicone oil at 25±5℃ for 1.5h and adjust the viscosity to 8200 mPa·s.

[0162] S3. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the pretreated hydrogen-containing silicone oil at 400 rpm. Stir for 12 min.

[0163] S4. Continue to add inhibitor and powdered aluminum hydroxide to the reactor, mix and stir for 25 minutes to obtain component B;

[0164] Step 3: Component A and component B are delivered to the mixer at a mass ratio of 1:1 via a metering pump and mixed at a speed of 1700 rpm for 4 minutes. During the mixing process, a water-cooled jacket is used to control the temperature of the mixed rubber compound to maintain the temperature at 27°C.

[0165] Step 4: The blended material is fed into a calender and calendered to form a double-sided composite release film to form a composite roll. The roller temperature of the calender is 30°C, and the roller gap is set to press the rubber material to a thickness of 3mm. The calendering accuracy error is ≤±0.08mm.

[0166] Step 5: Place the composite roll into the oven and use a gradient heating mode. The total vulcanization and foaming time is 17 minutes. The temperature zones are set as follows: 130°C for the preheating section, 172°C for the foaming and cross-linking section, and 155°C for the cross-linking and shaping section. The cross-linking time for the preheating section is 4 minutes, the cross-linking time for the foaming and cross-linking section is 7.5 minutes, and the cross-linking time for the cross-linking and shaping section is 5.5 minutes.

[0167] Step 6: The foam blank obtained in step 4 is placed in an oven and dried for 1.5 hours at 110°C. Then it is cooled to room temperature at a rate of 7°C / min. After peeling off the release film, the silicone foam is obtained.

[0168] The continuous production length is 335m.

[0169] The foam products prepared in Examples 1-6 were subjected to performance testing. All tests were conducted in accordance with national / industry standards, and the specific results are shown in Table 1. Specifically, apparent density was tested according to ASTM D1056, tensile strength according to ASTM D412, compression set according to the standard for testing compression set of rubber products, high and low temperature resistance was tested according to the standard for constant temperature aging + appearance / bending test, and flame retardancy was tested according to UL94 standard (including retesting after aging at 70℃ for 168 hours).

[0170] Table 1 Test Data Table

[0171]

[0172] Based on the above test data, trend charts for key performance indicators and performance correlation analysis charts were created to visually analyze the impact of formulation and process parameters on product performance, as well as the correlations between various performance indicators. See details below. Figure 1 and Figure 2 As shown.

[0173] Figure 1 In the middle, the horizontal axis represents the example numbers (1-6); the vertical axis represents the apparent density (left, kg / m³) and tensile strength (right, kPa); the curve type is: apparent density is represented by a solid blue line, and tensile strength is represented by a dashed yellow line.

[0174] The trend analysis is as follows:

[0175] The apparent density generally increases with the increase of the amount of hydroxyl-terminated polydimethylsiloxane and fumed silica + aluminum hydroxide added to components A and B: In Example 2, the amount of fumed silica + aluminum hydroxide added was the least, and the apparent density was the lowest (305.20 kg / m³). In Example 3, the amount of fumed silica + aluminum hydroxide added was the most, and the apparent density was the highest (342.10 kg / m³). In the other examples, the apparent density increased linearly with the change of filler amount.

[0176] Tensile strength is positively correlated with apparent density: as the amount of fumed silica and aluminum hydroxide added increases, the mechanical support of the foam is improved, and the tensile strength increases accordingly. In Example 2, the tensile strength is the lowest (289.0 kPa), and in Example 3, the tensile strength is the highest (338.0 kPa). The tensile strength of all examples is much higher than the index requirement of 250 kPa, indicating that the product has excellent mechanical properties.

[0177] Figure 2 In the graph, the horizontal axis represents the example number (1-6); the vertical axis represents the permanent compression deformation (%); and the bar chart represents the permanent compression deformation values ​​for each example.

[0178] The trend analysis is as follows:

[0179] The overall compression permanent deformation slightly increased with the increase of the amount of fumed silica + aluminum hydroxide added: In Example 2, the amount of fumed silica + aluminum hydroxide added was the least, and the compression permanent deformation was the lowest (3.5%). In Example 3, the amount of fumed silica + aluminum hydroxide added was the highest, and the compression permanent deformation was the highest (4.8%). All examples met the requirement of ≤5%, indicating that the product has excellent elastic recovery performance, is not easily deformed after long-term compression, and is suitable for sealing and protection scenarios.

[0180] The small change in compression permanent deformation (only 1.3%) indicates that the formulation and process of this invention have good control over the product's elasticity, and even with adjustments to the filler ratio, excellent elastic recovery performance can still be guaranteed.

[0181] Specifically, for the silicone foam prepared in Example 1, the cross-section of the foam was characterized using a ZEISS scanning electron microscope. The foam cross-section was treated with platinum spraying before observation. The cell structure and size of the foam were analyzed. The foam cell structure is as follows: Figure 3 As shown. By Figure 3 It can be seen that the foam cell structure is relatively uniform, with an average pore diameter of 300μm in the transverse direction and 550μm in the longitudinal direction.

[0182] Reference Figure 4 The diagram shows the microstructure of silicone foam. A continuous, dense, and resilient flame-retardant framework is constructed on the inner wall of the foam cells, making the microstructure of the silicone foam uniform and controllable, ultimately achieving 300 kg / m³.3 The density-grade silicone foam consistently achieves the UL94 V-0 flame retardant rating under normal conditions and after aging at 70℃ for 168 hours, while maintaining a compression set of ≤5%, not becoming brittle at -40℃, and without a decrease in mechanical properties.

[0183] Comparison images of the silicone foams prepared in Examples 1-5 before and after UL94 flame retardancy testing are shown below. Figure 5 and Figure 6 .

[0184] In summary, the silicone foam prepared by this invention exhibits excellent comprehensive performance, with wide-range high and low temperature resistance, stable flame retardant properties, good mechanical properties and elastic recovery, uniform and fine pores, and high batch-to-batch performance consistency. It can be widely used in fields such as sealing and protection of new energy vehicle battery systems, edge sealing of photovoltaic modules, thermal insulation protection of energy storage equipment, and potting and filling of aerospace electronic devices. It can completely replace imported similar products and reduce application costs. At the same time, the process and formulation of this invention have an important role in promoting the technological upgrading of my country's silicone rubber new materials field, and can drive the improvement and development of upstream and downstream industrial chains (silicone raw materials, flame retardants, foaming equipment, etc.), with significant industrial applicability, economic and social benefits, and market promotion value.

[0185] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent application and the contents of the specification of the present invention should still fall within the scope of the patent of the present invention.

Claims

1. A continuous foaming preparation process for microstructure-controlled high and low temperature flame-retardant silicone foam, characterized in that; The silicone foam is prepared by reacting component A and component B in a 1:1 mass ratio. Component A comprises the following raw materials in parts by weight: 60-80 parts of hydroxyl-terminated polydimethylsiloxane, 5-10 parts of hydroxyl silicone oil, 3-8 parts of fumed silica, 10-15 parts of powdered aluminum hydroxide, 0.05-2 parts of catalyst, and 0.5-2 parts of color paste. Component B comprises the following raw materials in parts by weight: 60-80 parts of hydroxyl-terminated polydimethylsiloxane, 0.1-0.3 parts of hydrogen-containing silicone oil, 0.01-0.05 parts of inhibitor, and 5-10 parts of powdered aluminum hydroxide. The inhibitor comprises the following raw materials in parts by weight: 85-95 parts of 1-ethynylcyclohexanol and 5-15 parts of 2-methyl-3-butyn-2-ol. The preparation process of the silicone foam specifically includes the following steps: Step 1: Prepare component A and component B separately; Step 2: Component A and component B are delivered to the mixer at a mass ratio of 1:1 via a metering pump and mixed at a speed of 1500-2000 rpm for 3-5 minutes. During the mixing process, a water-cooled jacket is used to control the temperature of the mixed rubber compound to maintain the temperature at 25-30℃. Step 3: The blended material is fed into a calender and calendered to form a composite roll by double-sided composite release film. Step 4: Place the composite roll into the oven and use a gradient heating mode. The total vulcanization and foaming time is 15-20 minutes. The temperature zones are set as follows: preheating zone 120-140℃, foaming and cross-linking zone 160-180℃, and cross-linking and shaping zone 150-160℃. Step 5: The foam blank obtained in step 4 is placed in an oven and dried for 1-2 hours at 100-120℃. Then it is cooled to room temperature at a rate of 5-10℃ / min. After peeling off the release film, the silicone foam is obtained.

2. The continuous foaming preparation process of the microstructure-regulated high and low temperature resistant flame-retardant organic silicon foam according to claim 1, characterized in that: In step 1, the preparation process of component A is as follows: A. The fumed silica and powdered aluminum hydroxide were sieved separately, and then dried at 80℃ for 2-4 hours until the moisture content was ≤0.1%; B. Place hydroxyl-terminated polydimethylsiloxane and hydroxyl silicone oil at 25±5℃ for 1-2 hours and adjust the viscosity to 5000-10000 mPa·s. C. Disperse the color paste and a portion of the pretreated hydroxyl silicone oil at 1000-1500 rpm for 5-10 minutes to obtain a color paste premix. D. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the remaining hydroxyl silicone oil at a speed of 300-500 rpm, and stir for 10-15 min. E. Increase the rotation speed to 800-1000 rpm, add the pretreated fumed silica and powdered aluminum hydroxide in three separate additions, stirring and mixing for 15 minutes after each addition, add the color paste premix, mix and stir evenly, then reduce the rotation speed to 200-300 rpm, add the catalyst, and mix and stir for 8-10 minutes to obtain component A.

3. The continuous foaming preparation process of microstructure-controlled high and low temperature flame-retardant silicone foam according to claim 2, characterized in that: In step C, the amount of hydroxyl silicone oil added is 1 / 4 of its weight.

4. The continuous foaming preparation process of microstructure-controlled high and low temperature flame-retardant silicone foam according to claim 1, characterized in that: In step 1, the preparation process of component B is as follows: S1. Sift the powdered aluminum hydroxide, then dry it at 80℃ for 2-4 hours until the moisture content is ≤0.1%; S2. Place hydroxyl-terminated polydimethylsiloxane and hydrogen-containing silicone oil at 25±5℃ for 1-2 hours and adjust the viscosity to 5000-10000 mPa·s. S3. Add the pretreated hydroxyl-terminated polydimethylsiloxane to the reactor, and add the pretreated hydrogen-containing silicone oil at a speed of 300-500 rpm. Stir for 10-15 minutes. S4. Continue to add inhibitor and powdered aluminum hydroxide to the reactor, mix and stir for 20-30 minutes to obtain component B.

5. The continuous foaming preparation process of microstructure-controlled high and low temperature flame-retardant silicone foam according to claim 1, characterized in that: In step 4, the crosslinking time is 3-5 min in the preheating section, 7-8 min in the foaming crosslinking section, and 5-7 min in the crosslinking and shaping section.

6. The continuous foaming preparation process of microstructure-controlled high and low temperature flame-retardant silicone foam according to claim 1, characterized in that: In step 3, the thickness of the composite roll material is ≤3mm.

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