A low-density, fast-rebound, high-stress-retention silica gel foam and a preparation method and application thereof

Abstract

The application belongs to the technical field of silica gel foam materials, and more particularly relates to a low-density, fast-rebound and high-stress-retention silica gel foam as well as a preparation method and application thereof. 3 The density of the silica gel foam is less than 300 kg / m 3 , the open porosity is 80% to 95%, the compression permanent deformation rate is less than 5% under the condition of keeping for 168 h at 150 DEG C with a compression strain of 50% and releasing for 30 min, the compression permanent deformation rate is less than 3% under the condition of keeping for 168 h at 150 DEG C with a compression strain of 50% and releasing for 24 h, and the stress attenuation rate is not more than 20% under the condition of keeping for 1000 h at 150 DEG C with a compression strain of 50% and releasing for 30 min. The silica gel foam can ensure low density, fast rebound and high stress retention of the foam under long-term high temperature.

Description

Technical Field

[0001] This application belongs to the technical field of silicone foam materials, and more specifically, relates to a low-density, fast-rebound, high-stress-retention silicone foam, its preparation method, and its application. Background Technology

[0002] Electronic sealing and cushioning materials are widely used in electronic products, automotive electronics, and communication equipment to provide cushioning protection and sealing isolation for internal components. Their temperature resistance and long-term rebound stability directly affect the operational reliability and service life of the protected products. As application environments become increasingly harsh, the industry is placing higher demands on the long-term service capability of sealing and cushioning materials in high-temperature environments.

[0003] Silicone rubber foam, made through a foaming process, combines the excellent weather resistance of silicone materials with the good cushioning properties of foam materials, making it a widely used functional sealing and cushioning material in electronic devices, new energy vehicles, and other fields. However, with the rapid development of thermal management systems for new energy vehicle power batteries, sealing components for 5G communication base stations, and aerospace cushioning materials, the requirements for the temperature resistance and cushioning performance of sealing materials have further increased. Especially in applications requiring sustained high temperatures of 150°C and continuous resilience, existing technologies exhibit significant limitations.

[0004] Currently, most mainstream manufacturing processes are based on addition-type liquid silicone rubber systems. To meet the requirements of resilience and stress retention under long-term high temperatures of 150°C, existing technologies modify the silicone matrix in the following ways: First, adding heat-resistant agents (such as high-temperature resistant fillers and antioxidants) to maintain mechanical properties by inhibiting the thermal oxidative degradation of the silicone rubber backbone at high temperatures. However, increasing the amount of heat-resistant agents significantly increases the material density and cost, and these agents are prone to migration and precipitation under long-term high temperatures, making it difficult to guarantee performance stability. Second, modifying the matrix (such as introducing high-temperature resistant groups) can improve temperature resistance to some extent, but it is often accompanied by increased material hardness and decreased resilience. Furthermore, increased crosslinking density makes it difficult for foams to meet low-density requirements. Third, increasing crosslinking density can enhance stress retention. However, excessively high crosslinking density increases material density and reduces cell opening rate, leading to slower rebound speed and deteriorated cushioning performance. In addition, the above modification methods mostly involve relatively expensive raw materials and complex process steps, making it difficult to promote large-scale application in industrial production. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this application is to provide a low-density, fast-rebound, high-stress-retention silicone foam, its preparation method and application, aiming to solve the problems of insufficient continuous rebound force, poor stress retention, weak resistance to permanent deformation, high process cost and difficulty in large-scale promotion and application of existing electronic product cushioning materials at high temperature of 150℃.

[0006] To achieve the above objectives, in a first aspect, this application provides a low-density, fast-rebound, and high-stress-retention silicone foam, wherein the density of the silicone foam is <300 kg / m³. 3 The open area ratio is 80%~95%; The aforementioned silicone foam, after being kept at 150℃ and 50% compressive strain for 168 hours and then released and recovered for 30 minutes, exhibited a compression set rate of less than 5%. The aforementioned silicone foam, after being kept at 150℃ and 50% compression strain for 168 hours and then released and recovered for 24 hours, exhibited a compression set of less than 3%. The stress attenuation rate of the above-mentioned silicone foam is no more than 20% after being kept at 150℃ and 50% compressive strain for 1000 hours and then released and recovered for 30 minutes.

[0007] Preferably, by weight, the raw materials for preparing the above-mentioned silicone foam include 100 parts of vinyl silicone oil, 10-30 parts of MQ resin, 0.6-1 parts of platinum catalyst, 0.02-0.04 parts of inhibitor, 8-14 parts of hydrogen-containing silicone oil, 10-25 parts of hydroxyl silicone oil, 4-10 parts of hollow glass microspheres, and 25-30 parts of flame-retardant filler. The MQ resin mentioned above is selected from vinyl MQ resins with a viscosity of 10,000~100,000 mP.s, an M / Q ratio of 0.7~0.9, and a vinyl content of 1%~2% by mass.

[0008] Preferably, the true density of the hollow glass microspheres is 240~400 kg / m³. 3 .

[0009] Preferably, the vinyl silicone oil is selected from vinyl-terminated silicone oils with a viscosity of 60,000 to 200,000 mPa·s and a vinyl content of 0.03% to 0.06% by mass.

[0010] Preferably, the hydrogen-containing silicone oil is a hydrogen-containing silicone oil with a Si-H group mass percentage of 1.6%.

[0011] Preferably, the platinum catalyst is selected from platinum catalysts with an effective platinum content of 5000 ppm.

[0012] Preferably, the above-mentioned inhibitor is an alkynyl alcohol inhibitor.

[0013] Preferably, the hydroxyl silicone oil is selected from hydroxyl silicone oils with a Si-OH group content of 4% to 8% by mass.

[0014] Preferably, the flame-retardant filler comprises aluminum hydroxide and / or magnesium hydroxide.

[0015] Secondly, this application provides a method for preparing the above-mentioned silicone foam, comprising the following steps: S1. Mix the above-mentioned vinyl silicone oil, hollow glass microspheres, MQ resin, platinum catalyst, inhibitor, hydrogen-containing silicone oil, hydroxyl silicone oil and flame-retardant filler according to the formula, and vacuum to obtain silicone rubber compound. S2. The above silicone rubber material is extruded into sheets and subjected to two-stage vulcanization treatment to obtain the above silicone foam.

[0016] Preferably, in step S1, the hollow glass microspheres are first mixed and dispersed with the vinyl silicone oil, and then the MQ resin, platinum catalyst, inhibitor, hydrogen-containing silicone oil, hydroxyl silicone oil and flame-retardant filler are added and mixed.

[0017] Preferably, the dispersion rotation speed is 100~300 rpm.

[0018] Preferably, in step S2, the above two-stage vulcanization process is as follows: first vulcanize at 60℃~90℃ for 5min~10min, and then vulcanize at 150℃~190℃ for 30min~40min.

[0019] Thirdly, this application provides a cushioning material for electronic products or power batteries, including the aforementioned silicone foam.

[0020] In summary, the technical solutions conceived in this application have the following main technical advantages compared with the prior art: (1) The density of the silicone foam provided in this application is <300kg / m³. 3 With an open area ratio of 80%~95%, after being held at 150℃ and 50% compressive strain for 168 hours and then released for 30 minutes, its compression permanent deformation rate is less than 5%; after being held at 150℃ and 50% compressive strain for 168 hours and then released for 24 hours, its compression permanent deformation rate is less than 3%; after being held at 150℃ and 50% compressive strain for 1000 hours and then released for 30 minutes, its stress attenuation rate is no more than 20%. This design ensures both low density and rapid rebound and high stress retention of the foam under long-term high temperatures.

[0021] (2) This application uses a specific type of vinyl silicone oil as the matrix, and introduces a specific type and amount of vinyl MQ resin, hollow glass microspheres, hydrogen-containing silicone oil, platinum catalyst, inhibitor, hydroxyl silicone oil and flame-retardant filler therein, so that the components work together to form the above-mentioned silicone foam through a cross-linking foaming process. Among them, the vinyl silicone oil is selected with a suitable viscosity, and combined with hydrogen-containing silicone oil with a high Si-H group content and platinum catalyst with a high platinum content, so that the system is fully cross-linked and the foam is completely formed during the foaming process, avoiding insufficient foaming due to insufficient cross-linking, and effectively reducing the permanent deformation of the foam as a whole; on this basis, the vinyl MQ resin provides cross-linking support and improves the degree of cross-linking without affecting the foaming, further enhancing the strength and temperature resistance of the foam; the hollow glass microspheres improve the resilience of the foam through their suitable true density and addition amount; and the inhibitor and hydroxyl silicone oil are used to control the foaming process and system state to ensure stable foam forming. Through the synergistic combination of the above components, the resulting silicone foam has a suitable porosity and low density, and maintains low compression set and stress attenuation under long-term high temperature conditions of 150°C, thus balancing cushioning, sealing and long-term reliability. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0023] In the description of the embodiments in this application, the words "exemplary" or "for example" are used to indicate that they are examples, illustrations, or descriptions. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design options. Specifically, the use of the words "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0024] In the description of the embodiments in this application, unless otherwise stated, "multiple" means two or more.

[0025] The inventors discovered that the rebound speed of foam materials is closely related to their pore structure and cross-linking density, and there is a trade-off between the two. Specifically, the higher the cross-linking density of the matrix, the faster the foam rebounds and the stronger its resistance to permanent deformation. However, cross-linking density is usually proportional to material density, and foams with high cross-linking density tend to have higher density. To reduce density and achieve lightweighting, existing foams mostly adopt open-cell or semi-open-cell structures. While these structures facilitate rapid rebound, the cell walls are thinner, the matrix strength is lower, and the rebound speed is relatively slow, resulting in poor resistance to permanent deformation after long-term compression. Therefore, how to ensure both rapid rebound and high stress retention of foam under long-term high temperatures while maintaining low density remains an unsolved technical problem. Based on this, this application provides a low-density, fast-rebound, and high-stress-retention silicone foam with a density of <300 kg / m³. 3 The open area ratio is 80%~95%; The aforementioned silicone foam, after being kept at 150℃ and 50% compressive strain for 168 hours and then released and recovered for 30 minutes, exhibited a compression set rate of less than 5%. The aforementioned silicone foam, after being kept at 150℃ and 50% compression strain for 168 hours and then released and recovered for 24 hours, exhibited a compression set of less than 3%. The stress attenuation rate of the above-mentioned silicone foam is no more than 20% after being kept at 150℃ and 50% compressive strain for 1000 hours and then released and recovered for 30 minutes.

[0026] In some embodiments, the density of the aforementioned silicone foam is tested according to the method described in ASTM D1056. The silicone foam is cut into circular samples with a diameter of 29±0.5 mm, and the mass of the samples is weighed using a 0.1 g electronic balance at a temperature of 23±2°C. The thickness of the product is measured using a thickness gauge, and the density is calculated based on the measured mass, area, and thickness. In some embodiments, the density of the aforementioned silicone foam is 180~290 kg / m³. 3 .

[0027] In some embodiments, the open-cell ratio of the aforementioned silicone foam is tested according to the method described in ASTM D6226. Specifically, sample preparation: two cubes with a side length of 2.5 cm are cut from the material to be tested; weighing and geometric volume determination: the sample mass is weighed using a 0.0001 g balance, with the reading accurate to 0.0001 g. Simultaneously, the side lengths of the two cubes are accurately measured and calculated, and the total geometric volume (Vg) of the two cubes is calculated. First measurement (Vp1): the two cubes are placed in a 100 cm... 3In the sample cell, the gas replacement volume (Vp1) of the sample was determined using a fully automated gas replacement true density analyzer. Second cutting: The sample was removed, and each cube was cut once along each of its three sides using a cutting tool, i.e., each cube was cut three times. Each cube was divided into 8 smaller cubes, resulting in a total of 16 smaller cubes. Second measurement (Vp2): All 16 smaller cubes were placed back into the sample cell, and their gas replacement volume (Vp2) was determined using the same method. The porosity was calculated using the following formulas: Open volume (Voc) = Vg - 2Vp1 + Vp2; Porosity (Co) = (Voc / Vg) × 100%.

[0028] In some embodiments, the compression set of the aforementioned silicone foam is tested according to the method described in ASTM D1056. Specifically, the silicone foam is cut into circular specimens with a diameter of 29±0.5 mm and placed in an environment with a temperature of 23±2℃ and a relative humidity of 50±5% for 72 hours to eliminate internal stress, and then the initial thickness t0 of the specimen is recorded. Subsequently, the specimen is placed between two parallel plates of a compression clamp and compressed to 50% of the initial thickness of the specimen (i.e., a constant compressive strain of 50% and a compression limit thickness t0). n =t0×50%), and aged at 150℃ for 168h. After aging, the sample was removed from the fixture and allowed to recover for 30min and 24h respectively in an environment at 23±2℃. After each recovery period, the recovered thickness t was measured at the same location in the center region of the sample. i And calculate the compression set using the following formula: Compression set (%) = [(t0-t...] i ) / (t0-t n )]×100%.

[0029] In some embodiments, the stress decay of the aforementioned silicone foam is tested according to the method described in ASTM D6147. Specifically, the silicone foam is cut into circular specimens with a diameter of 29±0.5 mm and placed at a temperature of 23±2℃ and a relative humidity of 50±5% for 72 hours to eliminate internal stress. Subsequently, the specimen is placed between two parallel plates of a compression fixture and compressed to 50% of the initial thickness of the specimen (i.e., a constant compressive strain of 50%). The initial compressive force F0 is recorded, and the specimen is aged at 150℃ for 1000 hours. After aging, while the specimen is still under compression, the residual force F1 applied to the fixture is recorded, and the stress decay rate is calculated according to the following formula: Stress decay rate (%) = [(F0-F1) / F0] × 100%.

[0030] In some embodiments, the raw materials for preparing the above-mentioned silicone foam, by weight, include 100 parts of vinyl silicone oil, 10-30 parts of MQ resin, 0.6-1 parts of platinum catalyst, 0.02-0.04 parts of inhibitor, 8-14 parts of hydrogen-containing silicone oil, 10-25 parts of hydroxyl silicone oil, 4-10 parts of hollow glass microspheres, and 25-30 parts of flame-retardant filler. The MQ resin mentioned above is selected from vinyl MQ resins with a viscosity of 10,000~100,000 mP.s, an M / Q ratio of 0.7~0.9, and a vinyl content of 1%~2% by mass.

[0031] In this application, the vinyl MQ resin is composed of M units (i.e., monofunctional siloxane units, R3SiO). 1 / 2 R is methyl) and Q unit (i.e. tetrafunctional siloxane unit, SiO 4 / 2 This is an organosilicon resin composed of M units and some of which have vinyl (-CH=CH2) R groups. The molar ratio of M units to Q units (M / Q ratio) in the aforementioned vinyl MQ resin is 0.7~0.9. This ratio provides additional crosslinking points for the silicone rubber network without affecting the foaming reaction, increasing the degree of crosslinking and thus enhancing the strength and temperature resistance of the foam matrix, as well as improving its stress retention under long-term high-temperature service. Simultaneously, the resin has moderate rigidity, good compatibility with the silicone rubber matrix, and can be uniformly dispersed without precipitation. Experiments showed that when the M / Q ratio is less than 0.7, the resin has poor compatibility with the silicone matrix, insufficient crosslinking points, and a low degree of crosslinking, resulting in a harder product, increased brittleness, and significant stress attenuation after long-term compression. When the M / Q ratio is greater than 0.9, the proportion of rigid Q units in the resin decreases, the reinforcing effect is weak, and it is difficult to effectively improve the strength and temperature resistance of the silicone foam.

[0032] In some embodiments, the true density of the hollow glass microspheres is 240~400 kg / m³. 3 By adding hollow glass microspheres within the specific true density range mentioned above, the rebound speed of silicone foam can be accelerated, and the resilience of the foam can be improved. When the true density of the hollow glass microspheres is too low, the particle size is usually large, making dispersion difficult and reducing compressive strength. They are also prone to breakage when mixed with other components, making it difficult to achieve a stable rebound improvement effect. When the true density of the hollow glass microspheres is too high, the effect on improving the resilience of the foam is not significant. In some embodiments, the amount of the hollow glass microspheres is 4wt% to 10wt% of the vinyl silicone oil. By controlling the addition amount of the hollow glass microspheres within this range, the resilience of the foam can be effectively improved. When the addition content is too low, the effect of improving resilience is not significant; when the addition content is too high, the microspheres are difficult to disperse uniformly, and the viscosity of the matrix increases rapidly, increasing the difficulty of processing and molding.

[0033] In some embodiments, the vinyl silicone oil is selected from end-vinyl silicone oils with a viscosity of 60,000 to 200,000 mPa·s and a vinyl content of 0.03% to 0.06% by mass. The inventors discovered in production that when the viscosity of the vinyl silicone oil is within the above-mentioned preferred range, it exhibits suitable viscosity and surface tension during foaming, effectively locking in the air bubbles generated during foaming, ensuring sufficient foaming, and maintaining the dimensional stability of the foam after molding, thereby achieving a lower foam density. Simultaneously, the moderate system viscosity provides good dispersibility and operability with MQ resin, fillers, and various additives, facilitating mixing. When the viscosity of the vinyl silicone oil is too low, the system's air-encapsulation and bubble-locking capabilities are insufficient, making it difficult for bubbles to remain stably, resulting in insufficient foaming and easy collapse and shrinkage of the foam, leading to increased foam density. When the viscosity of the vinyl silicone oil is too high, the system's fluidity decreases, making mixing and dispersion difficult, and causing bubbles to be poorly distributed uniformly, significantly increasing the difficulty of processing and molding, which is detrimental to large-scale production.

[0034] In some embodiments, the aforementioned hydrogen-containing silicone oil is a hydrogen-containing silicone oil with a Si-H group mass percentage of 1.6%.

[0035] In some embodiments, the platinum catalyst is selected from platinum catalysts with an effective platinum content of 5000 ppm. For example, the platinum catalyst may be selected from, but is not limited to, caster catalysts, chloroplatinic acid, etc. Based on the amount of the platinum catalyst and its effective platinum content, the total effective platinum content in the above-mentioned raw materials is 15-30 ppm. For example, the total effective platinum content in the above-mentioned raw materials may be 15 ppm, 17 ppm, 20 ppm, 22 ppm, 25 ppm, 27 ppm, 28 ppm, 30 ppm, etc.

[0036] In some embodiments, the inhibitor is an alkynyl alcohol inhibitor. For example, the alkynyl alcohol inhibitor may be selected from, but is not limited to, diethyl fumarate, ethynylcyclohexanol, 2-methyl-3-butyn-2-ol, 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, 3-phenyl-1-butyn-3-ol, and 1-hexynyl-1-cyclohexanol.

[0037] In some embodiments, the hydroxyl silicone oil is selected from hydroxyl silicone oils with a Si-OH group content of 4% to 8% by mass.

[0038] In some embodiments, the flame-retardant filler includes aluminum hydroxide and / or magnesium hydroxide.

[0039] This application uses vinyl silicone oil as a matrix and introduces vinyl MQ resin, hollow glass microspheres, hydrogen-containing silicone oil, platinum catalyst, inhibitor, hydroxyl silicone oil, and flame-retardant filler into it. These components work synergistically through a cross-linking foaming process to form the aforementioned silicone foam. Specifically, the vinyl silicone oil is selected with an appropriate viscosity, combined with hydrogen-containing silicone oil with a high Si-H group content and a platinum catalyst with a high total effective platinum content. This ensures sufficient cross-linking and complete foam formation during the foaming process, avoiding insufficient foaming due to inadequate cross-linking, and effectively reducing the overall permanent deformation of the foam. Furthermore, the vinyl MQ resin provides cross-linking points and increases the degree of cross-linking without significantly affecting foaming, further enhancing the strength and temperature resistance of the foam. The hollow glass microspheres improve the foam's resilience through their appropriate true density and addition amount. The inhibitor and hydroxyl silicone oil are used to regulate the foaming process and system state, ensuring stable foam formation. Through the synergistic combination of the above components, the resulting silicone foam has a suitable porosity and low density, and maintains low compression set and stress attenuation under long-term high temperature conditions of 150°C, thus balancing cushioning, sealing and long-term reliability.

[0040] On the other hand, this application also provides a method for preparing the above-mentioned silicone foam, comprising the following steps: S1. Mix the above-mentioned vinyl silicone oil, hollow glass microspheres, MQ resin, platinum catalyst, inhibitor, hydrogen-containing silicone oil, hydroxyl silicone oil and flame-retardant filler according to the formula, and then vacuum to obtain silicone rubber compound. S2. The above silicone rubber material is extruded into sheets and subjected to two-stage vulcanization treatment to obtain the above silicone foam.

[0041] In some embodiments, when preparing the above-mentioned silicone foam, hollow glass microspheres are first mixed and dispersed with vinyl silicone oil under low-speed conditions, and then the remaining components are added to the resulting mixture. Dispersing the hollow glass microspheres in the vinyl silicone oil first prevents the low-density hollow glass microspheres from adhering to the material surface and becoming difficult to mix evenly, ensuring uniform dispersion in the system. Low-speed dispersion allows the hollow glass microspheres to maintain their structural integrity during mixing, avoiding high-speed shearing that could cause microsphere breakage and weaken its resilience improvement effect. If high-speed dispersion is used, the hollow glass microspheres are prone to breakage, making it difficult to effectively improve the resilience performance of the foam.

[0042] In some embodiments, the rotational speed of the dispersion is 100~300 rpm.

[0043] In some embodiments, in step S1, the vacuum degree of the above-mentioned vacuuming is -0.085Mpa to -0.095Mpa, and the vacuuming time is 30 to 120 minutes.

[0044] In some embodiments, in step S2, the process of the two-stage vulcanization treatment is as follows: first vulcanization treatment at 60℃~90℃ for 5min~10min, and then vulcanization treatment at 150℃~190℃ for 30min~40min.

[0045] A cushioning material for electronic products or power batteries, characterized in that it comprises the aforementioned silicone foam.

[0046] It should be understood that, unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0047] The following are examples and comparative examples: Example 1 By weight, 100 parts of vinyl-terminated silicone oil (viscosity 170,000 mPa·s, vinyl content 0.04%, purchased from Haiduo Silicon Material HV-170000) and 10 parts of hollow glass microspheres (true density 300 kg / m³) were added. 3 The mixture (purchased from Zhongke Huaxing N32) was dispersed at 300 rpm for 1 hour, then placed in a planetary mixer. Ten parts of vinyl MQ resin (viscosity 60,000 mPa·s, M / Q ratio 0.8, vinyl content 1.4%, purchased from Xin'an Chemical WYNRES® 6350MV series), one part of platinum catalyst (purchased from Betterley PT5000, the total effective platinum content in the raw materials was approximately 27 ppm), 0.034 parts of inhibitor (ethynylcyclohexanol), and 12 parts of hydrogen-containing silicone oil (Si-H content...) were added. 1.6% (purchased from Runhe RH-202), 20 parts of hydroxyl silicone oil (Si-OH content 4%, purchased from Siwn-OH202 from Silicon Innovation Materials), and 30 parts of flame-retardant filler (aluminum hydroxide, purchased from Zhongke Flame Retardant FR3807) were stirred at room temperature for 6 hours, and then vacuumed for 60 minutes under a vacuum of -0.09 MPa to obtain silicone rubber compound. The silicone rubber compound was placed in a feeding machine for extrusion, first vulcanized at 80℃ for 10 minutes, and then vulcanized at 180℃ for 40 minutes to obtain silicone foam sample P1.

[0048] Example 2 By weight, 100 parts of vinyl-terminated silicone oil (viscosity 60,000 mPa·s, vinyl content 0.06%, purchased from Haiduo Silicon Material HV-60000) and 8 parts of hollow glass microspheres (true density 400 kg / m³) were added. 3The mixture (purchased from Zhongke Huaxing N40) was dispersed at 300 rpm for 1 hour, then placed in a planetary mixer. 15 parts of vinyl MQ resin (viscosity 100,000 mPa·s, M / Q ratio 0.7, vinyl content 1%, purchased from Xin'an Chemical WYNRES® 6350MV series) were added, along with 0.6 parts of platinum catalyst (Betterli PT5000, with a total effective platinum content of approximately 17 ppm in the raw materials), 0.02 parts of inhibitor (ethynylcyclohexanol), and 12 parts of hydrogen-containing silicon. Oil (Si-H content 1.6%), 15 parts of hydroxyl silicone oil (Si-OH content 8%, purchased from Siwn-OH203 from Silicon Innovation Materials), and 25 parts of flame-retardant filler (aluminum hydroxide) were stirred at room temperature for 6 hours, and then vacuumed for 60 minutes under a vacuum of -0.09 MPa to obtain silicone rubber compound. The silicone rubber compound was placed in a feeder for extrusion, first vulcanized at 80℃ for 10 minutes, and then vulcanized at 180℃ for 40 minutes to obtain silicone foam sample P2.

[0049] Example 3 By weight, 100 parts of vinyl-terminated silicone oil (viscosity 100,000 mPa·s, vinyl content 0.05%, purchased from Haiduo Silicon Material HV-100000) and 8 parts of hollow glass microspheres (true density 400 kg / m³) were added. 3 The mixture was dispersed at 300 rpm for 1 hour, then placed in a planetary mixer, and 15 parts of vinyl MQ resin (viscosity 60,000 mPa·s, M / Q ratio 0.8, vinyl content 1.4%), 0.8 parts of platinum catalyst (Betterli PT5000, the total effective platinum content in the raw materials was 23 ppm), 0.025 parts of inhibitor (ethynylcyclohexanol), 10 parts of hydrogen-containing silicone oil (Si-H content 1.6%), 16 parts of hydroxyl silicone oil (Si-OH content 4%), and 25 parts of flame-retardant filler (aluminum hydroxide) were added. The mixture was stirred at room temperature for 6 hours, and then vacuumed for 60 minutes under a vacuum of -0.09 MPa to obtain silicone rubber compound. The silicone rubber compound was extruded in a feeder, first vulcanized at 80℃ for 10 minutes, and then vulcanized again at 180℃ for 40 minutes to obtain silicone foam sample P3.

[0050] Example 4 By weight, 100 parts of vinyl-terminated silicone oil (viscosity 100,000 mPa·s, vinyl content 0.05%) and 4 parts of hollow glass microspheres (true density 300 kg / m³) were added. 3The mixture was dispersed at 300 rpm for 1 hour, then placed in a planetary mixer, and 20 parts of vinyl MQ resin (viscosity 10,000 mPa·s, M / Q ratio 0.9, vinyl content 2%), 0.6 parts of platinum catalyst (Betterli PT5000, the total effective platinum content in the raw materials was 18 ppm), 0.02 parts of inhibitor (ethynylcyclohexanol), 8 parts of hydrogen-containing silicone oil (Si-H content 1.6%), 10 parts of hydroxyl silicone oil (Si-OH content 8%), and 25 parts of flame-retardant filler (aluminum hydroxide) were added. The mixture was stirred at room temperature for 6 hours, and then vacuumed for 60 minutes under a vacuum of -0.09 MPa to obtain silicone rubber compound. The silicone rubber compound was extruded in a feeder, first vulcanized at 80℃ for 10 minutes, and then vulcanized again at 180℃ for 40 minutes to obtain silicone foam sample P4.

[0051] Example 5 By weight, 100 parts of vinyl-terminated silicone oil (viscosity 200,000 mPa·s, vinyl content 0.03%, purchased from Haiduo Silicon Material HV-200000) and 6 parts of hollow glass microspheres (true density 300 kg / m³) were added. 3 The mixture was dispersed at 300 rpm for 1 hour, then placed in a planetary mixer, and 30 parts of vinyl MQ resin (viscosity 10,000 mPa·s, M / Q ratio 0.9, vinyl content 2%), 0.8 parts of platinum catalyst (Betterli PT5000, the total effective platinum content in the raw materials is about 20 ppm), 0.025 parts of inhibitor (ethynylcyclohexanol), 13 parts of hydrogen-containing silicone oil (Si-H content 1.6%), 22 parts of hydroxyl silicone oil (Si-OH content 4%), and 30 parts of flame-retardant filler (aluminum hydroxide) were added. The mixture was stirred at room temperature for 6 hours, and then vacuumed for 60 minutes under a vacuum of -0.09 MPa to obtain silicone rubber compound. The silicone rubber compound was extruded in a feeder, first vulcanized at 80℃ for 10 minutes, and then vulcanized at 180℃ for 40 minutes to obtain silicone foam sample P5.

[0052] Example 6 By weight, 100 parts of vinyl-terminated silicone oil (viscosity 60,000 mPa·s, vinyl content 0.06%) and 4 parts of hollow glass microspheres (true density 240 kg / m³) were added. 3The sample (purchased from Zhongke Huaxing N40) was dispersed at 300 rpm for 1 hour, then placed in a planetary mixer, and 10 parts of vinyl MQ resin (viscosity 100,000 mPa·s, M / Q ratio 0.9, vinyl content 1%), 1 part of platinum catalyst (Betterli PT5000, the total effective platinum content in the raw materials was 27 ppm), 0.034 parts of inhibitor (ethynylcyclohexanol), 14 parts of hydrogen-containing silicone oil (Si-H content 1.6%), 25 parts of hydroxyl silicone oil (Si-OH content 4%), and 30 parts of flame-retardant filler (aluminum hydroxide) were added. The mixture was stirred at room temperature for 6 hours, and then vacuumed for 60 minutes under a vacuum of -0.09 MPa to obtain silicone rubber compound. The silicone rubber compound was extruded in a feeder, first vulcanized at 80℃ for 10 minutes, and then vulcanized at 180℃ for 40 minutes to obtain silicone foam sample P6.

[0053] Comparative Example 1 The formulation of silicone foam D1 in this comparative example is the same as that in Example 1, except that the viscosity of the vinyl-terminated silicone oil is 10,000 mPa·s and the mass content of vinyl is 0.1%.

[0054] Comparative Example 2 The formulation of silicone foam D2 in this comparative example is the same as that in Example 1, except that the M / Q ratio of the vinyl MQ resin is 0.5.

[0055] Comparative Example 3 The formulation of silicone foam D3 in this comparative example is the same as that in Example 1, except that the M / Q ratio of the vinyl MQ resin is 1.2.

[0056] Comparative Example 4 The formulation of the silicone foam D4 in this comparative example is the same as that in Example 1, except that the weight fraction of the platinum catalyst is 0.3 parts and the weight fraction of the inhibitor is 0.011 parts (Betteri PT5000, the total effective content of platinum in the raw materials is about 8 ppm).

[0057] Comparative Example 5 The formulation of the silicone foam D5 in this comparative example is the same as that in Example 1, except that the true density of the hollow glass microspheres is 440 kg / m³. 3 .

[0058] Comparative Example 6 The formulation of the silicone foam D6 in this comparative example is the same as that in Example 1, except that the weight of the hollow glass microspheres is 15 parts.

[0059] Comparative Example 7 The formulation of the silicone foam D7 in this comparative example is the same as that in Example 1, except that hollow glass microspheres are not added.

[0060] Comparative Example 8 The formulation of silicone foam D8 in this comparative example is the same as that in Example 1, except that MQ resin is not added.

[0061] Comparative Example 9 The formulation of the silicone foam D9 in this comparative example is the same as that in Example 1, except that MQ resin and hollow glass microspheres are not added.

[0062] Comparative Example 10 The formulation of the silicone foam D10 in this comparative example is the same as that in Example 1, except that MQ resin and hollow glass microspheres are not added, the weight fraction of the platinum catalyst is 0.3 parts, and the weight fraction of the inhibitor Betley PT5000 is 0.011 parts.

[0063] Comparative Example 11 The formulation of silicone foam D11 in this comparative example is the same as that in Example 1, except that the viscosity of the vinyl-terminated silicone oil is 10,000 mPa·s, the mass content of vinyl is 0.1%, the M / Q ratio of the vinyl MQ resin is 1.2, the weight fraction of the platinum catalyst is 0.3 parts, and the weight fraction of the inhibitor Betley PT5000 is 0.011 parts.

[0064] Comparative Example 12 The formulation of the silicone foam D12 in this comparative example is the same as that in Example 1, except that the M / Q ratio of the vinyl MQ resin is 1.2 and the true density of the hollow glass microspheres is 440 kg / m³. 3 The weight is 15 parts.

[0065] The characteristics of the silicone foam in the examples and comparative examples were tested, and the results are shown in Table 1.

[0066] Table 1. Features of the silicone foam in the embodiments

[0067] Table 2. Characteristics of the comparative silicone foam

[0068] As can be seen from Tables 1 and 2, the embodiments of this application, by adjusting the composition of the silicone foam, use vinyl silicone oil of suitable viscosity as the matrix, and introduce specific types and amounts of vinyl MQ resin, hollow glass microspheres, hydrogen-containing silicone oil, platinum catalyst, inhibitor, hydroxyl silicone oil, and flame-retardant filler, so that the silicone foam has a suitable open porosity and low density, and maintains low compression set and stress decay under long-term high temperature conditions of 150°C. This ensures low density while also taking into account the rapid rebound and high stress retention of the foam under long-term high temperature conditions. In contrast, the silicone foam formulations of the comparative examples are not within the scope controlled by this application. The silicone foams of the comparative examples either have a high density, a high compression set under long-term high temperature conditions of 150°C, or excessive stress decay, and do not possess excellent cushioning, sealing, and long-term reliability.

[0069] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A low-density, fast-rebound, high-stress-retention silicone foam, characterized in that, The density of the silicone foam is <300 kg / m³. 3 The open area ratio is 80%~95%; The silicone foam, after being held at 150℃ and 50% compressive strain for 168 hours and then released and recovered for 30 minutes, exhibits a compression set rate of less than 5%. The silicone foam, after being held at 150℃ and 50% compressive strain for 168 hours and then released and recovered for 24 hours, exhibits a compression set rate of less than 3%. The silicone foam is kept at 150℃ and 50% compressive strain for 1000 hours and then released and recovered for 30 minutes. Its stress attenuation rate is no more than 20%.

2. The silicone foam according to claim 1, characterized in that, The raw materials for preparing the silicone foam, by weight, include 100 parts vinyl silicone oil, 10-30 parts MQ resin, 0.6-1 parts platinum catalyst, 0.02-0.04 parts inhibitor, 8-14 parts hydrogen-containing silicone oil, 10-25 parts hydroxyl silicone oil, 4-10 parts hollow glass microspheres, and 25-30 parts flame-retardant filler. The MQ resin is selected from vinyl MQ resins with a viscosity of 10,000~100,000 mP.s, an M / Q ratio of 0.7~0.9, and a vinyl content of 1%~2% by mass.

3. The silicone foam according to claim 2, characterized in that, The true density of the hollow glass microspheres is 240~400 kg / m³. 3 .

4. The silicone foam according to claim 2, characterized in that, The vinyl silicone oil is selected from end-vinyl silicone oils with a viscosity of 60,000 to 200,000 mPa·s and a vinyl content of 0.03% to 0.06% by mass.

5. The silicone foam according to claim 2, characterized in that, The hydrogen-containing silicone oil is a hydrogen-containing silicone oil with a Si-H group content of 1.6% by mass.

6. The silicone foam according to claim 2, characterized in that, The platinum catalyst is selected from platinum catalysts with an effective platinum content of 5000 ppm; and / or, The inhibitor is an alkynyl alcohol inhibitor; and / or, The hydroxyl silicone oil is selected from hydroxyl silicone oils with a Si-OH group content of 4% to 8% by mass; and / or, The flame-retardant filler includes aluminum hydroxide and / or magnesium hydroxide.

7. A method for preparing silicone foam as described in any one of claims 2 to 6, characterized in that, Includes the following steps: S1. Mix the vinyl silicone oil, hollow glass microspheres, MQ resin, platinum catalyst, inhibitor, hydrogen-containing silicone oil, hydroxyl silicone oil, and flame-retardant filler according to the formula, and then vacuum to obtain silicone rubber compound. S2. The silicone material is extruded into sheets and subjected to two-stage vulcanization treatment to obtain the silicone foam.

8. The preparation method according to claim 7, characterized in that, In step S1, the hollow glass microspheres are first mixed and dispersed with the vinyl silicone oil, and then the MQ resin, platinum catalyst, inhibitor, hydrogen-containing silicone oil, hydroxyl silicone oil and flame-retardant filler are added and mixed. The dispersion speed is 100~300 rpm.

9. The preparation method according to claim 7, characterized in that, In step S2, the two-stage vulcanization process is as follows: first, vulcanize at 60℃~90℃ for 5min~10min, and then vulcanize at 150℃~190℃ for 30min~40min.

10. A cushioning material for electronic products or power batteries, characterized in that, Includes the silicone foam as described in any one of claims 1 to 6.

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