Rubber compound, heat-conducting wave-absorbing foam and preparation method of heat-conducting wave-absorbing foam

Abstract

The invention discloses a rubber compound, heat-conducting wave-absorbing foam and a preparation method thereof, and relates to the technical field of foam. The rubber compound comprises the following raw materials in parts by weight: 40-50 parts of vinyl silicone oil, 4-7 parts of MQ resin, 15-25 parts of white carbon black, 25-35 parts of a modifier, 0.01-0.05 part of an inhibitor, 1-3 parts of a cross-linking agent and 0.5-1 part of a catalyst. The heat-conducting and wave-absorbing foam is prepared by taking the rubber compound as a base material, compounding the rubber compound with high-proportion modified wave-absorbing powder and heat-conducting powder and combining with other foaming and crosslinking components for kneading and foaming. According to the invention, the problems of matrix weakening and poor processability caused by high filling of foam are solved, the obtained foam has excellent heat-conducting property and wave-absorbing property, and also has better mechanical strength, rebound resilience and uniform foaming structure, and the processing yield and reliability of the product are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foam, in particular to a rubber compound, a heat-conducting wave-absorbing foam and a preparation method thereof. BACKGROUND

[0002] At present, common ordinary foams (such as PU and EVA) have poor heat resistance, and are prone to softening, deformation or aging in a high-temperature environment for a long time, resulting in attenuation of their cushioning and sealing performance, and thus failing to meet the needs of high heat flow density scenarios. Heat-conducting silica gel foam improves the heat-conducting performance to some extent, but in order to achieve a necessary thermal conductivity (usually >0.5 W / (m·K)), a large amount of high-thermal-conductivity inorganic fillers such as alumina, boron nitride and graphene are often needed. High filling amount seriously damages the mechanical properties of the silica gel matrix itself, resulting in increased hardness, decreased resilience and reduced tensile strength of the foam. This makes the material prone to edge damage, size shrinkage or deformation during subsequent precision die cutting processing, especially when preparing small and special-shaped parts, and the yield is difficult to control. In addition, during use, such high-filled foam is also more prone to plastic deformation or cracking after long-term compression or heating, affecting its long-term reliability as an interface material.

[0003] On the other hand, most existing heat-conducting foams mainly focus on heat conduction performance and lack effective electromagnetic wave absorption function, and thus cannot solve the problem of electromagnetic interference inside the equipment. A few products that attempt to integrate wave-absorbing function often simply blend wave-absorbing powder (such as hydroxyl iron powder and ferrite) with heat-conducting fillers, but face the problems of uneven dispersion of powder, poor interfacial compatibility, and further deterioration of mechanical properties and processing performance due to large addition of wave-absorbing agent.

[0004] Therefore, it is an important goal to develop a matrix material that can withstand high filling amount without losing mechanical properties, and further realize the synergy and optimization of heat conduction and wave absorption function, in order to meet the needs of high-end electronic integration. SUMMARY

[0005] In order to solve the problems existing in the prior art, the purpose of the present application is to provide a rubber compound, a heat-conducting wave-absorbing foam and a preparation method thereof. The rubber compound has the characteristics of being suitable for high-proportion filler filling, good foaming effect and excellent mechanical strength. The heat-conducting wave-absorbing foam prepared by using the rubber compound in combination with heat-conducting powder and modified wave-absorbing powder has good resilience and mechanical strength, realizes effective heat conduction and electromagnetic wave absorption function, has uniform foaming, good processing performance, and is suitable for the heat dissipation field of high-end equipment such as new energy vehicle on-board charging equipment.

[0006] The present application provides the following technical solutions: In a first aspect, the present application provides a rubber compound for preparing a heat-conducting wave-absorbing foam, the raw materials of which include the following components in parts by weight: 40-50 parts of vinyl silicone oil; 4-7 parts of MQ resin; 15-25 parts of silica; 25-35 parts of modifier; Inhibitor 0.01–0.05 parts; 1-3 parts of crosslinking agent; Catalyst 0.5 to 1 part.

[0007] Preferably, the vinyl silicone oil has a viscosity of 10,000 to 100,000 mPa·s and a vinyl content of 0.05% to 0.07%.

[0008] Preferably, the viscosity of the MQ resin is 1,000 to 100,000 cps, and the vinyl content is 1.2% to 1.3%.

[0009] Preferably, the silica is at least one of fumed silica and precipitated silica; Preferably, the modifier is selected from one or more of hexamethyldisilazane, dimethyldichlorosilane, and polydimethylsiloxane.

[0010] Preferably, the crosslinking agent is at least one of terminal hydrogen-containing silicone oil and side-hydrogen silicone oil.

[0011] Preferably, the inhibitor is selected from one or more of 2-vinylisopropanol, perchloroethylene, and acetylenecyclohexanol.

[0012] Preferably, the catalyst is a platinum catalyst with a platinum content of 2000–5000 ppm.

[0013] Secondly, the present invention provides a method for preparing the above-mentioned compound rubber, which includes the following steps: (1) Mix vinyl silicone oil with MQ resin and knead at a speed of 30 r / min for 20 to 30 min; (2) Add inhibitor and crosslinking agent, and knead at 30 r / min for 10-20 min; (3) Add catalyst and knead for 10-20 minutes at a speed of 20 r / min and a temperature of 120-150℃, then cool to room temperature; (4) Add modifier and knead at 30 r / min for 10-20 min; (5) Add silica, knead at 30 r / min for 10-20 min, then knead at 50 r / min for 20-30 min; (6) Under a nitrogen protective atmosphere, dry at 180-200℃ for 2-4 hours to obtain the compound rubber.

[0014] Preferably, in step (1), the kneading temperature is maintained at 20~30℃.

[0015] Thirdly, the present invention provides a thermally conductive and wave-absorbing foam, the raw materials of which, by weight, comprise the following components: 15-25 parts of the above-mentioned compound rubber; 15-65 parts of thermally conductive powder; 15-65 parts of microwave absorbing powder; Antioxidant 1.0–1.5 parts; Inhibitor 0.008–0.01 parts; Crosslinking agent 0.15–0.65 parts; Catalyst 0.2–0.5 parts; Foaming agent 0.15-0.65 parts.

[0016] Preferably, the modified microwave absorbing powder is prepared by the following method: the modifier and solvent are mixed at a weight ratio of 4:6, hydrolyzed for 2-4 hours to prepare a modified liquid; the modified liquid and microwave absorbing powder are mixed at a weight ratio of 8:2, stirred evenly, ultrasonically treated, and dried to obtain modified oxidized microwave absorbing powder.

[0017] Preferably, the microwave absorbing powder is selected from one or more of the following: hydroxyl iron powder, hydroxyl nickel powder, iron-silicon-aluminum alloy powder, ferrite, and iron powder.

[0018] Preferably, the modifier is selected from one or more of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

[0019] The silane coupling agent is selected from one or more of 3-aminopropyltriethoxysilane (KH550), γ-glycidoxypropyltrimethoxysilane (KH560), γ-(methacryloyloxy)propyltrimethoxysilane (KH570), dodecyltrimethoxysilane, vinyltriethoxysilane, and dodecylsilane.

[0020] Preferably, the solvent is anhydrous ethanol.

[0021] Preferably, the stirring is performed at a speed of 1000 rpm / min for 20 to 30 minutes.

[0022] Preferably, the ultrasonic treatment is performed by using 2000Hz ultrasound for 20-30 minutes. Preferably, the drying temperature is 30–50°C.

[0023] Preferably, the drying process further includes allowing the material to stand at room temperature for 24–48 hours to allow the modifier to fully coat the microwave-absorbing powder.

[0024] Preferably, the antioxidant is selected from one of the following: peroxide decomposition type antioxidants, free radical scavenging type antioxidants, and metal deactivation type antioxidants. Examples include zinc dialkyl dithiophosphate, zinc dialkyl dithiocarbamate, N-phenyl-α-naphthylamine, alkylphenthiazides, benzotriazole derivatives, and mercaptobenzothiazide derivatives.

[0025] Preferably, the foaming agent is selected from one or more of benzoyl peroxide (BPO), di(2,4-dimethyl)sulfide, di(2,5-dimethyl)sulfide, and azobisisobutyronitrile.

[0026] Preferably, the thermally conductive powder is selected from one or more of alumina, aluminum nitride, boron nitride, aluminum hydroxide, silicon nitride, and diamond.

[0027] Preferably, the crosslinking agent is at least one of terminal hydrogen-containing silicone oil and side-hydrogen silicone oil.

[0028] Preferably, the inhibitor is selected from one or more of 2-vinylisopropanol, perchloroethylene, and acetylenecyclohexanol.

[0029] Preferably, the catalyst is a platinum catalyst with a platinum content of 2000–5000 ppm.

[0030] Fourthly, the present invention also provides a method for preparing the above-mentioned thermally conductive and wave-absorbing foam, which includes the following steps: S1. Knead the thermally conductive powder and the compound to obtain the base material; S2. Add antioxidants and microwave absorbing powder to the base material and knead. S3. Add cross-linking agent and inhibitor, and knead. S4. Add catalyst and knead. S5. Add foaming agent, knead and mix to obtain rubber compound; S6. After the rubber material is extruded, calendered and foamed, thermally conductive and wave-absorbing foam is obtained.

[0031] Preferably, in step S1, the kneading speed is 30 r / min and the time is 20 min.

[0032] Preferably, in step S2, the mixing parameters are: rotation speed 30 r / min and time 20 min.

[0033] Preferably, in step S3, the mixing parameters are: rotation speed 30 r / min, time 10 min.

[0034] Preferably, in step S4, the mixing parameters are: rotation speed 30 r / min and time 10 min.

[0035] Preferably, in step S5, the mixing parameters are: rotation speed 30 r / min, time 10 min.

[0036] Preferably, in steps S2 to S5, the temperature is maintained at 20 to 30°C.

[0037] Preferably, in step S6, the linear speed of the calendering process is 0.8 m / min.

[0038] Preferably, in step S6, the foaming temperature is 120~150℃.

[0039] The present invention has the following technical effects: This invention prepares a high-strength, high-toughness compound through the compounding of specific components. This compound constructs a robust elastic network, serving as a core framework and providing a solid mechanical foundation for subsequent high-proportion filling of functional fillers, thus fundamentally ensuring the mechanical properties and processing feasibility of the final composite material. Furthermore, using this compound as a matrix, foam is prepared by introducing a specific proportion of thermally conductive powder and modified microwave-absorbing powder. This design allows the material to maintain excellent mechanical reliability even under high filler loads, while achieving effective synergy between thermal conductivity and microwave absorption properties. Ultimately, the thermally conductive and microwave-absorbing foam of this invention overcomes the processing defects of traditional products, possessing excellent dimensional stability, die-cutting capability, and a uniform foam structure, significantly improving production yield and long-term product reliability. Detailed Implementation

[0040] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] It should be understood that, when used in this specification and the appended claims, the terms “comprising” and “including” indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0042] It should be noted that the raw material information of the compound rubber in the following embodiments of the present invention is as follows: Raw materials used to prepare rubber compounds: Vinyl silicone oil: model Vi301, viscosity 100,000 mPa·s, vinyl content approximately 0.05%–0.07%, purchased from Ningbo Runhe High-Tech Materials Co., Ltd.; MQ resin: Model CX355, viscosity 6500 mPa·s, vinyl content approximately 1.2%–1.3%, purchased from Guangdong Chenxi New Material Technology Co., Ltd.; Fumed silica: Model TS-610, purchased from Cabot Corporation; Modifier: Hexamethyldisilazane, purchased from Xinghuo Company; Inhibitor: Model CX-5002H, component is acetylenecyclohexanol, purchased from Guangdong Chenxi New Material Technology Co., Ltd.; Crosslinking agent: Model CX-350D, is a hydrogen-terminated silicone oil with a hydrogen content of approximately 0.08% and a viscosity of approximately 10-50 mm² / s, purchased from Guangdong Chenxi New Materials Technology Co., Ltd. Catalyst: Model CX-5001, a platinum catalyst with a platinum (Pt) content of approximately 2000 ppm, purchased from Guangdong Chenxi New Materials Technology Co., Ltd.

[0043] Raw materials used to prepare thermally conductive and microwave-absorbing foam: Compound rubber: Products prepared using the technical solution of this invention; Thermally conductive powder: alumina, model GD-750A, purchased from Foshan Jingge New Material Co., Ltd.; Microwave-absorbing powder: Hydroxy iron powder, model LH-C03, purchased from Jiangxi Yuean New Material Co., Ltd.; Antioxidant: Type 245 (hindered phenol), purchased from BASF; Inhibitor: Model CX-5002H (acetylenecyclohexanol), purchased from Guangdong Chenxi New Material Technology Co., Ltd.; Crosslinking agent: Model CX-351, is a hydrogen-containing silicone oil with a hydrogen content of approximately 0.18% and a viscosity of approximately 10-50 mm² / s, purchased from Guangdong Chenxi New Materials Technology Co., Ltd. Catalyst: Model CX-5001 (platinum catalyst), purchased from Guangdong Chenxi New Material Technology Co., Ltd. Foaming agent: azobisisobutyronitrile, purchased from Dongguan Yongzheng Chemical Co., Ltd.; Modifier (used for modifying microwave absorbing powder): Dodecyltriethoxysilane (silane coupling agent), model N1213, purchased from Shandong Silicon Science New Materials Co., Ltd. Solvent (used in the preparation of modified microwave absorbing powder): anhydrous ethanol, industrial grade.

[0044] The modified microwave absorbing powder is prepared by the following method: the modifier and ethanol are mixed at a weight ratio of 4:6 and hydrolyzed for 3 hours to prepare a modified liquid; the modified liquid and the microwave absorbing powder are mixed at a weight ratio of 8:2 and stirred at 1000 rpm / min for 20-30 min; then ultrasonically treated with 2000 Hz for 25 min, dried at 40℃, and left at room temperature for 36 hours to allow the modifier to fully coat the microwave absorbing powder, thus preparing the modified microwave absorbing powder.

[0045] It should be noted that the specific raw material models, specifications, and supplier information listed in the above embodiments are only for more clearly describing and verifying the technical solution of the present invention, and are not intended to limit the present invention. For those skilled in the art, within the scope of the formulation composition and performance requirements provided by the present invention, other commercially available or self-made equivalent raw materials that meet the requirements can be selected for substitution. All raw materials obtained by equivalent substitution or equivalent transformation should be considered to be included within the protection scope of the claims of the present invention.

[0046] To verify the technical effect of the compound of the present invention, compounds A1-A3 and compounds B1-B3 were prepared, and the component contents of their raw materials are shown in Table 1 below: Table 1. Raw material component content of compound A1-A3 and compound B1-B3

[0047] The above components are used to prepare a compound rubber according to the following preparation method, which includes the following steps: (1) Add vinyl silicone oil and MQ resin to a kneader and knead for 25 minutes at a speed of 30 r / min; (2) Add inhibitor and crosslinking agent, and knead for 15 minutes at a speed of 30 r / min under the condition of 25°C cooling water flowing through the kneader; (3) Add catalyst and knead for 15 minutes at a speed of 20 r / min and a temperature of 120-150℃. After kneading, cool to room temperature. (4) Add modifier and knead at 30 r / min for 15 min; (5) Add silica, knead at 30 r / min for 15 min, then knead at 50 r / min for 25 min; (6) Under a nitrogen protective atmosphere, the mixture is dried at 190°C for 3 hours to obtain the compound.

[0048] The prepared rubber compounds A1-A3 and B1-B3 were subjected to mechanical property tests, including hardness, tensile strength, and elongation at break. The test results are shown in Table 2 below. Table 2 Test results of mechanical properties of rubber compound

[0049] As shown in Table 2, the compound using the technical solution of this application exhibits moderate hardness, high tensile strength, and excellent elongation at break, indicating that it successfully constructs an elastic network that combines strength and toughness. This effectively solves the fundamental problem of insufficient strength of the silicone rubber matrix in high-filling scenarios, laying a reliable mechanical foundation for the subsequent preparation of high-performance foams. However, after modifying the compound formulation of compounds B1-B3, the mechanical properties of the prepared compounds all decreased to varying degrees.

[0050] To further illustrate the technical solution of the present invention, the following embodiments and comparative examples of foam are provided. The content of raw material components of foam in each embodiment and comparative example is shown in Table 3 below: Table 3. Raw material component content of the examples and comparative examples

[0051] The above components are used to prepare foam according to the following foam preparation method, which includes the following steps: S1. Add the thermally conductive powder and the compound to the kneader and knead at a speed of 30 r / min for 20 min to obtain the base material; S2. Add antioxidants and microwave absorbing powder to the base material, and knead it for 20 minutes at a speed of 30 r / min under the condition of cooling water flowing through the kneader. S3. Add crosslinking agent and inhibitor, and knead for 10 minutes at a speed of 30 r / min under the condition of cooling water flowing through the kneader; S4. Add the catalyst and knead for 10 minutes at a speed of 30 r / min under the condition of cooling water flowing through the kneader; S5. Add foaming agent and knead at 30 r / min for 10 min under the condition of cooling water in the kneader to obtain rubber material; S6. Place the rubber compound into an extruder, set the extrusion rate to 100g / s and the vacuum degree to -0.08Mpa, and extrude the rubber compound; calender the extruded rubber compound at a linear speed of 0.8m / min, and then foam it in a tunnel oven at a temperature of 135℃ to obtain foam.

[0052] The foams prepared in Examples 1-7 and Comparative Examples 1-4 were subjected to thermal conductivity tests, density tests, tensile strength tests, and frequency band tests, and their foaming behavior was observed. The test results are shown in Table 4 below: Table 4 Performance test results of the foams prepared in Examples 1-7 and Comparative Examples 1-4

[0053] As shown in Table 4, the embodiments of the present invention, by compounding rubber A1 with thermally conductive powder and modified microwave absorbing powder in a specific ratio, can balance and regulate the thermal conductivity and microwave absorption properties of the material within a certain range while ensuring the mechanical properties of the matrix, thus achieving functional integration. In contrast, Comparative Example 1 uses ordinary silicone oil to replace the compounding rubber, resulting in a significant increase in thermal resistance and uneven foaming; Comparative Example 3 does not add a crosslinking agent, and although its thermal resistance is low, its strength network is incomplete and its tensile strength is insufficient; Comparative Examples 2 and 4 only add a single thermally conductive powder or microwave absorbing powder, thus only possessing the single effect of thermal conductivity or microwave absorption.

[0054] In summary, the technical solution of this invention possesses a significant synergistic effect. By "strengthening the matrix first, then incorporating functional components," it systematically solves the long-standing contradictions in the field of high-performance foam. The use of compounded rubber provides the necessary mechanical framework to withstand high filler volumes, fundamentally ensuring the material's processability. Furthermore, by using it as the matrix material and incorporating functional fillers, foam products with excellent thermal conductivity and microwave absorption properties, as well as outstanding processing stability and long-term reliability, have been successfully prepared.

[0055] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A rubber compound characterized in that, The raw materials include the following components by weight fraction: Vinyl silicone oil 40-50 parts; MQ resin 4-7 parts; White carbon black 15-25 parts; Modifier 25-35 parts; Inhibitor 0.01-0.05 parts; Crosslinking agent 1-3 parts; Catalyst 0.5-1 part.

2. The rubber mixture of claim 1, wherein The viscosity of the vinyl silicone oil is 10,000-100,000 mPa·s, and the vinyl content is 0.05%-0.07%.

3. The rubber composition of Claim 1 wherein, The modifier is selected from one or more of hexamethyldisilazane, dimethyldichlorosilane, and polydimethylsiloxane.

4. A process for the preparation of a rubber mixture according to any one of claims 1 to 3, characterized in that The method includes the following steps: After mixing the vinyl silicone oil and the MQ resin, knead at a rotation speed of 30 r / min for 20-30 min; Add the inhibitor and the crosslinking agent, and knead at a rotation speed of 30 r / min for 10-20 min; Add the catalyst, and knead at a rotation speed of 20 r / min and a temperature of 120-150℃ for 10-20 min, and then cool to room temperature; Add the modifier, and knead at a rotation speed of 30 r / min for 10-20 min; Add the white carbon black, first knead at a rotation speed of 30 r / min for 10-20 min, and then knead at a rotation speed of 50 r / min for 20-30 min; Dry treat at 180-200℃ for 2-4 h in a nitrogen protective atmosphere to obtain a rubber compound.

5. A heat conductive wave-absorbing foam, characterized in that, The raw materials include the following components by weight fraction: The rubber compound of any one of claims 1-3 15-25 parts; Modified wave-absorbing powder 15-65 parts; Thermal conductive powder 15-65 parts; Antioxidant 1.0-1.5 parts; Inhibitor 0.008-0.01 parts; Crosslinking agent 0.15-0.65 parts; Catalyst 0.2-0.5 parts; Foaming agent 0.15-0.65 parts.

6. The heat-conducting wave-absorbing foam of claim 5, wherein, The modified wave-absorbing powder is prepared by the following method: mix the modifier and the solvent in a weight ratio of 4:6, hydrolyze for 2-4 h to prepare a modified liquid; mix the modified liquid and the wave-absorbing powder in a weight ratio of 8:2, uniformly stir, then perform ultrasonic treatment, and dry to obtain modified oxidized wave-absorbing powder.

7. The heat-conducting wave-absorbing foam of claim 6, wherein, The wave-absorbing powder is selected from one or more of hydroxyl iron powder, hydroxyl nickel powder, iron-silicon-aluminum alloy powder, ferrite, and iron powder.

8. The heat-conducting wave-absorbing foam of claim 5, wherein, The thermal conductive powder is selected from one or more of aluminum oxide, aluminum nitride, boron nitride, aluminum hydroxide, silicon nitride, and diamond.

9. The heat-conducting wave-absorbing foam of claim 5, wherein, The foaming agent is selected from one or more of benzoyl peroxide, bis-ditetra-sulfurizing agent, bis-dipenta-sulfurizing agent, and azobis-isobutyronitrile.

10. A method for preparing the heat-conducting wave-absorbing foam according to any one of claims 5-9, characterized in that, The method includes the following steps: S1, knead the thermal conductive powder and the rubber compound of any one of claims 1-3 to obtain a base material; S2, add the antioxidant and the modified wave-absorbing powder to the base material and knead; S3, add the crosslinking agent and the inhibitor and knead; S4, add the catalyst and knead; S5, add the foaming agent and knead to obtain a glue; S6, extrude and calender the glue, and then foam to obtain thermal conductive wave-absorbing foam.

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