Silicone rubber thermal insulation material for heater and preparation method of silicone rubber thermal insulation material

Abstract

The invention discloses a silicone rubber thermal insulation material for a heater and a preparation method thereof, and belongs to the technical field of thermal insulation materials. Comprising the following raw materials in parts by weight: 42-56 parts of methyl vinyl silicone rubber, 31-43 parts of alpha, omega-dihydroxymethyl phenyl silicone rubber, 10-20 parts of modified montmorillonite, 12-18 parts of a reinforcing agent, 7-11 parts of silicon dioxide aerogel powder, 4-6 parts of a cross-linking agent, 8-12 parts of a foaming agent and 3-5 parts of sulfur. Wherein the silicon dioxide aerogel powder can reduce the heat conductivity coefficient of the material; wherein the modified montmorillonite can enhance the mechanical strength and flame retardance of the material and reduce the heat conductivity coefficient of the material, so that the prepared silicone rubber thermal insulation material is high in mechanical strength and low in heat conductivity coefficient and has stable and efficient flame retardance, and when the silicone rubber thermal insulation material is used for a heater, the energy consumption of the heater can be reduced, the service life of the heater is prolonged, and the service life of the heater is prolonged. The important application value is realized in the technical field of thermal insulation materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal insulation materials, and in particular relates to a silicone rubber thermal insulation material for a heater and a preparation method thereof. Background Art

[0002] With the rapid development of modern industry, heaters, as important thermal energy conversion devices, are widely used in a variety of fields, including home appliances, automobiles, aerospace, medical equipment, and industrial production. In these applications, the performance and efficiency of heaters depend not only on the design of their core heating elements but also on the supporting insulation materials. The choice of insulation material directly affects the heater's energy utilization, safety, and service life. Therefore, the research and development of high-performance insulation materials has become a key focus of the industry.

[0003] Traditional heater insulation materials mainly include inorganic materials such as glass fiber, asbestos, ceramic fiber, and some organic foam materials (such as polyurethane foam). These materials have met the needs of early heaters to a certain extent, but they also have obvious limitations. For example, although glass fiber and ceramic fiber have good high-temperature resistance, they are relatively brittle and easily generate dust during processing and use, posing a potential threat to human health; asbestos has been banned in many countries due to its carcinogenic risk. In addition, although traditional organic foam materials are light in weight and have good thermal insulation effects, their temperature resistance is limited and they cannot adapt to the long-term working requirements in high-temperature environments. At the same time, their flammability also poses a safety hazard.

[0004] In recent years, silicone rubber has gradually attracted the attention of researchers due to its unique comprehensive properties and is considered an ideal alternative to traditional thermal insulation materials. Silicone rubber is a polymer elastomer with a silicon-oxygen bond as its main chain structure. It has excellent high and low temperature resistance, electrical insulation, chemical stability, and mechanical strength. Especially under extreme temperature conditions, silicone rubber can still maintain good flexibility and physical properties, making it very suitable for use as a thermal insulation material for heaters. However, the thermal conductivity of ordinary silicone rubber is relatively high, and its thermal insulation effect is not ideal when used alone as a thermal insulation material. Silicone rubber also has low mechanical strength. In addition, silicone rubber still has the defect of being easily flammable when used in high-temperature environments, which limits its application areas.

[0005] Therefore, how to design a silicone rubber insulation material that has high thermal insulation performance, excellent mechanical properties and flame retardant properties is still a technical problem that needs to be solved urgently. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and provide a silicone rubber thermal insulation material for a heater and a preparation method thereof.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A method for preparing a silicone rubber thermal insulation material for a heater comprises the following steps:

[0009] Methyl vinyl silicone rubber, α,ω-dihydroxymethylphenyl silicone rubber, modified montmorillonite, a reinforcing agent, silica aerogel powder and a cross-linking agent are mixed in a mixer, and the uniformly mixed raw materials are added to an open mill for mixing to obtain a rubber mix, and then the rubber mix, a foaming agent and sulfur are added to a flat vulcanizer for foaming and vulcanization, and cooled to room temperature to obtain a silicone rubber insulation material for a heater.

[0010] Furthermore, the raw materials are calculated in parts by weight as follows: 42-56 parts of methyl vinyl silicone rubber, 31-43 parts of α,ω-dihydroxymethylphenyl silicone rubber, 10-20 parts of modified montmorillonite, 12-18 parts of reinforcing agent, 7-11 parts of silica aerogel powder, 4-6 parts of crosslinking agent, 8-12 parts of foaming agent, and 3-5 parts of sulfur.

[0011] Furthermore, the reinforcing agent is one of white carbon black, silicon particles, zinc oxide, iron oxide and titanium oxide.

[0012] Furthermore, the cross-linking agent is one of hydrogen-containing silicone oil, polysilazane and dicumyl peroxide.

[0013] Furthermore, the foaming agent is one of azodicarbonamide, azobisisobutyronitrile, and p-benzenesulfonylhydrazide.

[0014] Adding silica aerogel powder to the raw materials is a loose and porous nanoparticle that can effectively reduce the thermal conductivity of the material, thereby reducing the energy consumption of the heater and increasing the service life of the heater. In addition, adding a reinforcing agent to the raw materials can improve the mechanical strength of the material. Finally, the mechanical strength and thermal insulation properties of the material after vulcanization and foaming treatment are enhanced.

[0015] Furthermore, the modified montmorillonite is prepared by the following steps:

[0016] Step 1. Add diethylenetriamine, diethylphosphinoacetic acid, and N,N-dimethylformamide (DMF) to a round-bottom flask equipped with a stirring device, stir and mix, then add dicyclohexylcarbodiimide (DCC) to the flask, place the device in a 50°C water bath, and heat in the water bath for 10 hours. After the reaction is complete, stop heating, filter, and remove the solvent by vacuum distillation. The mixture is washed with anhydrous ethanol several times and dried in vacuo to obtain intermediate 1; the ratio of diethylenetriamine, diethylphosphinoacetic acid, N,N-dimethylformamide, and dicyclohexylcarbodiimide is 10.3 g:41.7 g:150 mL:41.2 g;

[0017] DCC acts as a dehydrator to catalyze the reaction, where the two amino groups on diethylenetriamine react with the carboxyl groups on diethylphosphoacetic acid to form an amidation reaction, with a slight excess of diethylphosphoacetic acid, to obtain intermediate 1. The specific reaction process is shown below:

[0018]

[0019] Step 2, the intermediate product 1, benzyl chloride and xylene were added to a round-bottom flask equipped with a stirring and reflux device, stirred and mixed, and the temperature was gradually increased until reflux occurred. The temperature was maintained constant and the reaction was kept warm for 10 hours. After the reaction was completed, part of the solvent was removed by rotary evaporation, and then purified by column chromatography (the eluent was a mixed solvent of ethyl acetate / benzene, the volume ratio of the two was 2:3). The eluent was removed by rotary evaporation to obtain the intermediate product 2; the ratio of the amount of the intermediate product 1, benzyl chloride and xylene was 45.9 g:27.3 g:150 mL;

[0020] The secondary amino group on the intermediate product 1 reacts with the chlorine group on the benzyl chloride, with the molar ratio of benzyl chloride to the intermediate product 1 being 2:1, and the benzyl chloride being slightly in excess, to obtain the intermediate product 2 (quaternized product). The specific reaction process is shown below:

[0021]

[0022] Step 3, sodium montmorillonite and xylene are added to a round-bottom flask equipped with a stirring device, and mechanically stirred in a water bath at 80°C until the sodium montmorillonite is uniformly dispersed to obtain a montmorillonite suspension; then the intermediate product 2 and xylene are added to another round-bottom flask equipped with a stirring device, and the mixture is fully stirred and mixed to obtain a mixed solution, and the mixed solution is mixed with the montmorillonite suspension, and the reaction is stirred at 80°C for 5 hours. After the reaction is completed, the mixture is centrifuged and washed several times with deionized water until the Cl - All of the solution was washed out (0.1 mol / L AgNO3 solution was added dropwise to the filtrate without producing a white precipitate), vacuum dried, and ground to obtain modified montmorillonite; the ratio of sodium montmorillonite, xylene, and intermediate 2 was 10 g:100 mL:12.6 g;

[0023] In the layered structure of sodium montmorillonite, the silicon-oxygen tetrahedron layer and the aluminum-oxygen octahedron layer are bonded by ionic bonds, and the interlayers adsorb Na by electrostatic interaction. + To balance the charge, the intermediate product 2 is adsorbed between the montmorillonite layers by electrostatic interaction, replacing the original Na + , to obtain modified montmorillonite;

[0024] Montmorillonite (MMT) is a layered silicate mineral with a unique nano-scale lamellar structure and a high specific surface area. Its thermal conductivity is much lower than that of the silicone rubber matrix, and it has high mechanical strength. Modification of montmorillonite by intermediate product 2 greatly enhances the surface hydrophobicity of montmorillonite, improves the compatibility of montmorillonite with the silicone rubber matrix, and enables the modified montmorillonite to be evenly dispersed in the silicone rubber matrix, so that the performance of montmorillonite is fully utilized, effectively improves the mechanical strength of the matrix, and reduces the conductivity. Thermal coefficient; in addition, the modified montmorillonite molecule contains phosphate groups, which are a type of phosphorus-based flame retardant. It achieves flame retardant effects through gas-phase flame retardant mechanisms and condensed-phase flame retardant mechanisms, and can improve the flame retardant properties of the matrix; not only that, the modified montmorillonite molecule also contains benzene rings, which not only further improve the hydrophobicity of the modified montmorillonite, but also, as a rigid group, further enhance the mechanical strength of the matrix; finally, the organic molecular chain is connected to the inorganic montmorillonite, which improves the stability of the organic small molecules, thereby improving the stability of the modified montmorillonite performance.

[0025] Beneficial effects of the present invention:

[0026] 1. The silicone rubber thermal insulation material prepared by the present invention, by adding silica aerogel powder to the raw materials, can effectively reduce the thermal conductivity of the material;

[0027] 2. Adding reinforcing agent to the raw materials improves the mechanical strength of the material;

[0028] 3. By modifying montmorillonite, the compatibility with the silicone rubber matrix is ​​better than that of ordinary montmorillonite, which significantly enhances the mechanical strength and flame retardancy of the material, reduces the thermal conductivity of the material, and maintains long-term stable performance;

[0029] 4. The mechanical strength and thermal insulation properties of the material after vulcanization and foaming treatment are further enhanced;

[0030] Therefore, the silicone rubber thermal insulation material prepared by the present invention has high mechanical strength, low thermal conductivity, and stable and efficient flame retardant properties. Using it in a heater can reduce the energy consumption of the heater and increase the service life of the heater, and has important application value in the field of thermal insulation material technology. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] Example 1

[0033] Preparation of modified montmorillonite:

[0034] Step 1, 10.3 g of diethylenetriamine, 41.7 g of diethylphosphinoacetic acid and 150 mL of N,N-dimethylformamide were added to a round-bottom flask equipped with a stirring device, and after stirring and mixing, 41.2 g of dicyclohexylcarbodiimide was added to the flask, and the device was placed in a 50°C water bath and heated in a water bath for 10 hours. After the reaction was complete, heating was stopped, the product was filtered, and the solvent was removed by distillation under reduced pressure. The product was washed with anhydrous ethanol several times and dried in vacuo to obtain intermediate 1;

[0035] Step 2, 45.9 g of intermediate product 1, 27.3 g of benzyl chloride and 150 mL of xylene were added to a round-bottom flask equipped with a stirring and reflux device, stirred and mixed, and the temperature was gradually increased until reflux occurred. The temperature was maintained constant and the reaction was kept warm for 10 hours. After the reaction was completed, part of the solvent was removed by rotary evaporation, and then purified by column chromatography (the eluent was a mixed solvent of ethyl acetate / benzene, the volume ratio of the two was 2:3), and the eluent was removed by rotary evaporation to obtain intermediate product 2;

[0036] Step 3, 10g of sodium montmorillonite and 50mL of xylene were added to a round-bottom flask equipped with a stirring device, and mechanically stirred in a water bath at 80°C until the sodium montmorillonite was uniformly dispersed to obtain a montmorillonite suspension; then 12.6g of intermediate product 2 and 50mL of xylene were added to another round-bottom flask equipped with a stirring device, and the mixture was thoroughly stirred and mixed to obtain a mixed solution, which was mixed with the montmorillonite suspension and stirred at 80°C for 5h. After the reaction was completed, the mixture was centrifuged and washed several times with deionized water until the Cl - All of the precipitate was washed out (0.1 mol / L AgNO3 solution was added dropwise to the filtrate without producing a white precipitate), vacuum dried, and ground to obtain modified montmorillonite.

[0037] Example 2

[0038] Preparation of modified montmorillonite:

[0039] Step 1, 20.6g of diethylenetriamine, 83.4g of diethylphosphinoacetic acid and 300mL of N,N-dimethylformamide were added to a round-bottom flask equipped with a stirring device, and after stirring and mixing, 82.4g of dicyclohexylcarbodiimide was added to the flask, and the device was placed in a 50°C water bath and heated in a water bath for 10 hours. After the reaction was complete, heating was stopped, and the mixture was filtered. The solvent was removed by distillation under reduced pressure, and the mixture was washed with anhydrous ethanol several times and dried in vacuo to obtain intermediate 1;

[0040] Step 2, 91.8 g of intermediate product 1, 54.6 g of benzyl chloride and 300 mL of xylene were added to a round-bottom flask equipped with a stirring and reflux device, stirred and mixed, and the temperature was gradually increased until reflux occurred. The temperature was maintained constant and the reaction was kept warm for 10 hours. After the reaction was completed, part of the solvent was removed by rotary evaporation, and then purified by column chromatography (the eluent was a mixed solvent of ethyl acetate / benzene, the volume ratio of the two was 2:3), and the eluent was removed by rotary evaporation to obtain intermediate product 2;

[0041] Step 3, 20g of sodium montmorillonite and 100mL of xylene were added to a round-bottom flask equipped with a stirring device, and mechanically stirred in a water bath at 80°C until the sodium montmorillonite was uniformly dispersed to obtain a montmorillonite suspension; then 25.2g of intermediate product 2 and 100mL of xylene were added to another round-bottom flask equipped with a stirring device, and the mixture was thoroughly stirred and mixed to obtain a mixed solution, and the mixed solution was mixed with the montmorillonite suspension, and stirred at 80°C for 5h. After the reaction was completed, the mixture was centrifuged and washed several times with deionized water until the Cl - All of the precipitate was washed out (0.1 mol / L AgNO3 solution was added dropwise to the filtrate without producing a white precipitate), vacuum dried, and ground to obtain modified montmorillonite.

[0042] Example 3

[0043] 42 g of methyl vinyl silicone rubber, 31 g of α, ω-dihydroxymethylphenyl silicone rubber, 10 g of modified montmorillonite prepared in Example 1, 12 g of titanium oxide, 7 g of silica aerogel powder, and 4 g of hydrogenated silicone oil were mixed in a mixer. The uniformly mixed raw materials were added to an open mill for mixing to obtain a rubber mix. The rubber mix, 8 g of azodicarbonamide, and 3 g of sulfur were then added to a flat vulcanizer for foaming and vulcanization, and the mixture was cooled to room temperature to obtain a silicone rubber insulation material for a heater.

[0044] Example 4

[0045] 49 g of methyl vinyl silicone rubber, 37 g of α, ω-dihydroxymethylphenyl silicone rubber, 15 g of modified montmorillonite prepared in Example 1, 15 g of white carbon black, 9 g of silica aerogel powder, and 5 g of dicumyl peroxide were mixed in a mixer, and the uniformly mixed raw materials were added to an open mill for mixing to obtain a rubber mix. The rubber mix, 10 g of azobisisobutyronitrile, and 4 g of sulfur were then added to a flat vulcanizer for foaming and vulcanization, and the mixture was cooled to room temperature to obtain a silicone rubber insulation material for a heater.

[0046] Example 5

[0047] 56 g of methyl vinyl silicone rubber, 43 g of α, ω-dihydroxymethylphenyl silicone rubber, 20 g of modified montmorillonite prepared in Example 1, 18 g of white carbon black, 11 g of silica aerogel powder, and 6 g of dicumyl peroxide were mixed in a mixer, and the uniformly mixed raw materials were added to an open mill for mixing to obtain a rubber mix. The rubber mix, 12 g of azobisisobutyronitrile, and 5 g of sulfur were then added to a flat vulcanizer for foaming and vulcanization, and the mixture was cooled to room temperature to obtain a silicone rubber insulation material for a heater.

[0048] Comparative Example 1

[0049] Commercially available ordinary sodium montmorillonite was used to replace the modified montmorillonite in Example 5, and the remaining steps were the same as in Example 5 to obtain the material.

[0050] Comparative Example 2

[0051] Use commercially available silicone rubber insulation.

[0052] The following performance tests were performed on Examples 3, 4, and 5 and Comparative Examples 1 and 2:

[0053] The tensile strength was determined using the national standard GB / T 528-2009 “Vulcanized rubber or thermoplastic rubber - Determination of tensile stress-strain properties”;

[0054] The thermal conductivity of the sample is measured using the national standard GB / T10294-2008 "Determination of steady-state thermal resistance and related properties of insulation materials";

[0055] The limiting oxygen index of the sample was measured using the national standard GB / T 10707 "Determination of Combustion Properties of Rubber". The limiting oxygen index of Examples 3, 4, and 5 was then measured again after standing at room temperature for 100 days. The limiting oxygen index retention rate was calculated as follows: limiting oxygen index retention rate = limiting oxygen index after test / limiting oxygen index before test × 100%.

[0056] The measured results are shown in the following table:

[0057]

[0058]

[0059] As can be seen from the above table, the mechanical strength and flame retardancy of the silicone rubber thermal insulation material prepared in the embodiment of the present invention are higher than those of the comparative example, and the thermal conductivity is lower than that of the comparative example. Therefore, the present invention has important application value in the field of thermal insulation material technology.

[0060] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0061] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a silicone rubber thermal insulation material for a heater, characterized in that: The following steps are involved: The methyl vinyl silicone rubber, α,ω-dihydroxymethylphenyl silicone rubber, modified montmorillonite, a reinforcing agent, silica aerogel powder and a cross-linking agent are mixed in a mixer, and the uniformly mixed raw materials are added to an open mill for mixing to obtain a rubber mix, and then the rubber mix, a foaming agent and sulfur are added for foaming and vulcanization, and cooled to obtain a silicone rubber insulation material for a heater.

2. The method for preparing a silicone rubber thermal insulation material for a heater according to claim 1, characterized in that: The raw materials are calculated as follows in parts by weight: 42-56 parts of methyl vinyl silicone rubber, 31-43 parts of α,ω-dihydroxymethylphenyl silicone rubber, 10-20 parts of modified montmorillonite, 12-18 parts of reinforcing agent, 7-11 parts of silica aerogel powder, 4-6 parts of crosslinking agent, 8-12 parts of foaming agent, and 3-5 parts of sulfur.

3. The method for preparing a silicone rubber thermal insulation material for a heater according to claim 1, characterized in that: The modified montmorillonite is prepared by the following steps: Step 1: Add diethylenetriamine, diethylphosphinoacetic acid, and N,N-dimethylformamide to a round-bottom flask, stir and mix, then add dicyclohexylcarbodiimide to the flask, heat in a water bath at 50°C for 10 hours, stop heating, filter, evaporate under reduced pressure, wash, and dry to obtain intermediate 1; Step 2: Add the intermediate product 1, benzyl chloride and xylene into a flask, stir and mix, gradually increase the temperature until reflux occurs, maintain the temperature unchanged, and keep the reaction for 10 hours. After the reaction is complete, rotary evaporation, column chromatography purification, and rotary evaporation to obtain the intermediate product 2; Step 3: Add sodium montmorillonite and xylene to a flask, stir evenly in a water bath at 80°C to obtain a montmorillonite suspension; then add the intermediate product 2 and xylene to another flask, stir evenly to obtain a mixed solution, mix the mixed solution with the montmorillonite suspension, stir and react at 80°C for 5 hours. After the reaction is completed, centrifuge and wash, vacuum dry, and grind to obtain modified montmorillonite.

4. The method for preparing a silicone rubber thermal insulation material for a heater according to claim 3, characterized in that: In step 1, the ratio of diethylenetriamine, diethylphosphinoacetic acid, N,N-dimethylformamide, and dicyclohexylcarbodiimide is 10.3 g:41.7 g:150 mL:41.2 g.

5. The method for preparing a silicone rubber thermal insulation material for a heater according to claim 3, characterized in that: In step 2, the ratio of the intermediate product 1, benzyl chloride, and xylene used is 45.9 g:27.3 g:150 mL.

6. The method for preparing a silicone rubber thermal insulation material for a heater according to claim 3, characterized in that: In step 3, the ratio of sodium montmorillonite, xylene and intermediate product 2 is 10g:100mL:12.6g.

7. The method for preparing a silicone rubber thermal insulation material for a heater according to claim 1, characterized in that: The reinforcing agent is one of white carbon black, silicon particles, zinc oxide, iron oxide and titanium oxide.

8. The method for preparing a silicone rubber thermal insulation material for a heater according to claim 1, characterized in that: The crosslinking agent is one of hydrogen-containing silicone oil, polysilazane and dicumyl peroxide.

9. The method for preparing a silicone rubber thermal insulation material for a heater according to claim 1, characterized in that: The foaming agent is one of azodicarbonamide, azobisisobutyronitrile and p-benzenesulfonylhydrazide.

10. A silicone rubber thermal insulation material for a heater, characterized in that: Prepared according to the method according to any one of claims 1 to 9.

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