Fire-resistant heat-insulating ceramifiable silicone rubber and preparation method thereof

Abstract

The invention discloses a preparation method of fire-resistant heat-insulating ceramifiable silicone rubber, which comprises the following specific steps of: uniformly mixing special silicone rubber serving as a base material, modified composite ceramic powder, a component A curing agent and a component B curing agent, and calendering and curing to obtain the fire-resistant heat-insulating ceramifiable silicone rubber. The modified composite ceramic powder is mainly prepared from needle-like wollastonite, low-melting-point glass powder, aluminum hydroxide, calcium carbonate, flaky mica powder and expanded perlite, and the modified composite ceramic powder is sequentially coated and modified with a chitosan-platinum complex and (4-vinyl phenyl) trimethoxysilane. In a high-temperature environment, a chitosan component in the silicone rubber can form a continuous porous carbon layer, so that the fire resistance of a ceramic layer is improved; meanwhile, the carbon layer, the expanded perlite and the flaky mica powder cooperate to construct a multiple heat insulation interface, so that the transfer of high temperature to the interior is greatly delayed; in addition, the compatibility, dispersity and thermal stability of the powder in a base material are optimized through secondary silane coating, so that the prepared porcelainized silicone rubber has excellent flame retardance, heat insulation effect and porcelainizing strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramicized flame-retardant powder processing and fireproofing and flame-retardant technology, and in particular to a fireproof and heat-insulating ceramicizable silicone rubber and a preparation method thereof. BACKGROUND

[0002] As an important high-temperature flame-retardant material, ceramicizable silicone rubber can form a continuous and dense ceramic layer through high-temperature rapid sintering in a fire scene, thereby achieving fireproof separation and heat insulation, and is widely used in the fields of electric wires and cables, new energy vehicles, energy storage, etc. However, the existing ceramicizable silicone rubber products have several performance contradictions and defects that need to be solved urgently. Although ceramicizable silicone rubber foam has the advantages of good heat insulation and lightweight, it has the problems of low strength after ceramicization and easy deformation and cracking. Although solid ceramicizable silicone rubber can form a ceramic layer with high strength and excellent fire resistance, it is prone to cracking during the ceramicization process, and heat penetrates through the cracks, resulting in poor heat insulation effect. In addition, ceramicizable silicone rubber generally has the problem of insufficient carbon source, which leads to insufficient formation of the carbon layer during the flame-retardant process, cannot effectively buffer the ceramic shrinkage stress, and affects the flame-retardant effect. If conventional composite flame retardants such as MCA and APP are introduced to improve the flame retardancy, they will interfere with the ceramicization process of silicone rubber and damage the ceramicization effect.

[0003] To comprehensively solve the above-mentioned problems of ceramicizable silicone rubber, the present research prepares modified composite ceramic powder through a special formula and process, so that the finally prepared ceramicizable silicone rubber material can maintain the excellent conventional performance of silicone rubber at room temperature. When exposed to high temperature or open flame, a ceramic hard shell layer can be quickly formed on the surface, and a carbon-ceramic composite barrier is constructed inside, which not only utilizes the ceramic layer to ensure the structural strength and fire resistance stability, but also strengthens the heat insulation effect through the carbon layer, thereby achieving the synergistic improvement of the three core performances of fire resistance, heat insulation and crack resistance. SUMMARY

[0004] The present application provides a preparation method of a fireproof and heat-insulating ceramicizable silicone rubber. Compared with the commercially available ceramicizable silicone rubber which is prone to cracking and bulging during combustion, the method effectively solves the above-mentioned problems through innovative modification means. The ceramicization composite flame-retardant powder is modified twice by chitosan-platinum complex and silane containing special groups, and finally the ceramicizable silicone rubber with excellent fireproof and heat-insulating performance is prepared by combining the fixed silicone formula and process.

[0005] To solve the above-mentioned technical problems, the present application adopts the following technical scheme: A fireproof and heat-insulating ceramicizable silicone rubber, comprising the following components in parts by weight: 100 parts of silicone rubber raw rubber, 20-50 parts of reinforcing filler, 100-300 parts of modified composite ceramic powder, 0.25-1 parts of A component curing agent, and 0.5-2 parts of B component curing agent. The modified composite ceramic powder is prepared by the following method: first, chitosan is subjected to coordination reaction with chloroplatinic acid to form a chitosan-platinum complex, then the complex is used to coat the composite ceramic powder once, and finally the composite ceramic powder after the first coating is subjected to secondary coating with vinyl phenyl siloxane; The composite ceramic powder is composed of the following components in percentage by weight: wollastonite 50-75%, low-melting-point glass powder 1-10%, aluminum hydroxide 5-15%, calcium carbonate 5-15%, mica powder 5-10%, and expanded perlite 5-10%.

[0006] The raw silicone rubber is methyl-vinyl silicone raw rubber terminated by methyl or vinyl. It is used to provide the flexibility and weather resistance of the rubber matrix and provide the silicon source for the porcelainization reaction.

[0007] The reinforcing filler is one or a combination of fumed white carbon black and precipitated white carbon black. It is used to improve the tensile strength and tear strength of the silicone rubber matrix and improve the processing properties.

[0008] The A-component curing agent is a mixture of platinum-gold complex and polysiloxane.

[0009] The B-component curing agent is a mixture of bridging agent, inhibitor, and polysiloxane.

[0010] The wollastonite has a needle-like morphology and a particle size D50 of 3-15 μm and an aspect ratio of 2:1-20:1; the low-melting-point glass powder has a particle size D50 of 5-10 μm; the aluminum hydroxide has a particle size D50 of 1-15 μm; the calcium carbonate has a particle size D50 of 1-15 μm; the mica powder has a flaky morphology and a particle size D50 of 3-25 μm; and the closed-cell perlite has a particle size D50 of 20-50 μm.

[0011] A preparation method of a fire-resistant and heat-insulating porcelainizable silicone rubber, comprising the following steps: (1) preparing the modified composite ceramic powder of claim 1; (2) adding 100 parts of raw silicone rubber, 20-50 parts of reinforcing filler, and 3-5 parts of hydroxyl silicone oil into a kneader, and kneading for 2-4 h to obtain a glue A; (3) adding 100 parts of glue A and 0.5-2 parts of B-component curing agent into the kneader, and kneading for 0.5-1 h, then gradually adding 100-300 parts of the modified composite ceramic powder, and continuing to knead for 1-4 h to obtain a glue B; (4) adding 100 parts of glue B into a double-roll open mill, adding 0.25-1 part of A-component curing agent, and opening and rolling for 5-15 min to mix the glue uniformly, and adjusting the roll gap to 0.5-5 mm to obtain the fire-resistant and heat-insulating porcelainizable silicone rubber; (5) placing the fireproof and heat-insulating porcelainizable silicone rubber material on a calendering line, controlling the thickness to be 0.1-10 mm by double rollers, vulcanizing at 120-160 DEG C for 5-15 min, and obtaining the fireproof and heat-insulating porcelainizable silicone rubber sheet through one-time vulcanization forming.

[0012] The modified composite ceramic powder is prepared by a method comprising the following steps: Step one, adding 5-25 g of chitosan powder into a round bottom flask containing 1 L of 1-10 mmol / L aqueous solution of chloroplatinic acid, stirring for 0.5-1.0 h, using the protonation effect of amino group to make the chitosan powder fully dissolved and coordinated with Pt(IV), and obtaining a chitosan-platinum (Chi-Pt for short) complex solution. Step two, adding 200-500 g of ceramic powder into the Chi-Pt complex solution, stirring and dispersing for 0.5-1.0 h, then adjusting the pH of the solution to 6.5-7.0 by using 0.5-1.0 mol / L of ammonia water and continuing to stir for 1 h, fully using the weak alkalinity of the ceramic powder aqueous solution to make the chitosan molecular chain re-aggregate, and then make the Chi-Pt complex slowly precipitate from the solution to the surface of the composite ceramic powder, adjusting the pH of the solution to 8.0-8.5 by using 0.5-1.0 mol / L of ammonia water and continuing to stir for 0.5-1.0 h, making the Chi-Pt complex quickly precipitate from the solution to form a Chi-Pt complex coating layer on the surface of the composite ceramic powder, and after the stirring is completed, the mixed slurry is subjected to suction filtration, washing, and spray drying at 80-100 DEG C to obtain the Chi-Pt coated composite ceramic powder. Step three, adding 150-300 g of the composite ceramic powder into a high-speed mixing and dispersing machine, and then adding 0.1wt%-1.0wt% of (4-vinylphenyl)trimethoxysilane based on the mass of the composite ceramic powder to modify the composite ceramic powder by dry method, the rotation speed is 2000-3000 r / min, and the mixing time is 3-10 min, to obtain the modified composite ceramic powder. This step is used to improve the compatibility between the powder and the silicone rubber, and to improve the heat resistance of the silicone rubber.

[0013] The chitosan powder has a particle size D50 of 15-50 um, a deacetylation degree of 85-95%, and a molecular weight of <150000 Da.

[0014] The fireproof and heat-insulating porcelainizable silicone rubber prepared by the method can be directly used or used after being compounded with other materials for fireproof materials in different scenes.

[0015] The beneficial effects of the method are as follows: 1、The chitosan component in the application can be carbonized to form a continuous porous carbon layer at high temperature, which can not only serve as a modified composite ceramic powder adhesive to fill the gaps between the powders and improve the density and strength of the ceramic layer, but also effectively absorb the volume shrinkage stress during the ceramic process, thereby improving the bulging phenomenon and ceramic cracks caused by deformation of the existing porcelainizable silicone rubber. In addition, the chitosan and platinum catalyst form a chitosan-platinum complex, which has a synergistic effect, effectively inhibits the degradation of silicone rubber at high temperature, promotes the porcelainization of silicone rubber, and greatly improves the porcelainization effect and efficiency. 2、The modified composite ceramic powder of the application precisely matches and synergistically designs the components of the composite ceramic powder, forms multiple thermal insulation interfaces by using the closed pore structure of expanded perlite and the stacked structure of mica powder, and combines the carbon layer formed by carbonization of chitosan to form a double thermal insulation system, which delays the transmission of high temperature to the internal substrate, further ensures the structural integrity of the material, and improves the reliability of the porcelainizable silicone rubber in extreme environments. 3、The application adopts a secondary modification process: once coated with a chitosan-platinum complex by wet surface deposition, and twice coated with a silane coupling agent containing a vinyl benzene group. The chitosan amphoteric polar macromolecule in the first coating has good compatibility with silicone rubber and inorganic fillers, which can improve the dispersion uniformity of the powder; the silane coupling agent in the second coating can be connected to the surface of the powder through chemical bonding, the benzene ring structure gives the composite powder higher thermal stability, and the vinyl group improves the compatibility between the powder and the silicone rubber substrate, finally realizing the simultaneous optimization of the compatibility, dispersion and thermal stability of the composite powder. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Figure 2 is a situation diagram of Example 1 after the ceramic performance test-burning for 30 minutes. DETAILED DESCRIPTION

[0017] The embodiments of the application are only used for illustrative purposes and cannot be understood as a limitation of the application. Specific embodiment 1: (1) Preparation of the modified composite ceramic powder: Step one, in a round bottom flask containing 1L of 5mmol / L chloroplatinic acid aqueous solution, 10g of chitosan powder is added, and stirred for 1.0h to fully dissolve the chitosan powder, to obtain Chi-Pt complex solution 1#. Step two, 300g of wollastonite, 50g of low-melting-point glass powder, 50g of aluminum hydroxide, 50g of calcium carbonate, 25g of mica powder, and 25g of expanded perlite were added to the Chi-Pt complex solution 1#. After stirring and dispersing for 0.5h, the solution pH was adjusted to 7.0 with 0.5mol / L ammonia water and stirring was continued for 1h, allowing the Chi-Pt complex to slowly precipitate from the solution onto the surface of the composite ceramic powder. The solution pH was then adjusted to 8.0 with 0.5mol / L ammonia water and stirring was continued for 1.0h, allowing the Chi-Pt complex to quickly precipitate from the solution and form a Chi-Pt complex coating layer on the surface of the composite ceramic powder. After stirring was completed, the mixed slurry was filtered and washed, and then spray dried at 80℃ to obtain Chi-Pt coated composite ceramic powder 1#. Step three, 300g of Chi-Pt coated composite ceramic powder 1# was added to a high-speed mixing and dispersing machine, and 0.3wt% (4-vinylphenyl) trimethoxysilane was used to dry-modify the Chi-Pt coated composite ceramic powder 1# at a rotation speed of 2500r / min for 5min to obtain modified composite ceramic powder 1#. (2) In a kneader, 100 parts of raw silicone rubber, 40 parts of reinforcing filler, and 3 parts of hydroxyl silicone oil were added and kneaded for 2h to obtain gel A; (3) In a kneader, 100 parts of gel A and 2 parts of B component curing agent were added and kneaded for 0.5h, and then 100 parts of composite modified ceramic powder 1# was added and kneaded for 2h to obtain gel B1#; (4) 100 parts of gel B1# was added to a two-roll open mill, 0.5 parts of A component curing agent was added, and the rubber was evenly opened for 15min with a roll gap of 3mm to obtain fire-resistant and heat-insulating porcelainizable silicone rubber compound 1#; (5) The fire-resistant and heat-insulating porcelainizable silicone rubber compound 1# was placed on a calendering line, the thickness was controlled to 2mm by a double roller, and vulcanization was carried out at 150℃ for 10min to obtain fire-resistant and heat-insulating porcelainizable silicone rubber sheet 1#. Specific embodiment 2: The difference between this embodiment 2 and embodiment 1 is that the modified composite ceramic powder prepared in step (1) is different, and the other steps and amounts are consistent with embodiment 1. The method for preparing the modified composite ceramic powder in this embodiment 2 is as follows: Step one, in a round-bottom flask containing 1L of 5mmol / L aqueous chloroplatinic acid solution, 20g of chitosan powder was added and stirred for 1.0h to fully dissolve the chitosan powder, obtaining Chi-Pt complex solution 2#. Step two, 300g of wollastonite, 50g of low-melting-point glass powder, 50g of aluminum hydroxide, 50g of calcium carbonate, 25g of mica powder, and 25g of expanded perlite were added to the Chi-Pt complex solution 2#. After stirring and dispersing for 0.5h, the pH of the solution was adjusted to 7.0 with 0.5mol / L ammonia water and stirring was continued for 1h, allowing the Chi-Pt complex to slowly precipitate from the solution onto the surface of the composite ceramic powder. The pH of the solution was then adjusted to 8.0 with 0.5mol / L ammonia water and stirring was continued for 1.0h, allowing the Chi-Pt complex to quickly precipitate from the solution and form a Chi-Pt complex coating layer on the surface of the composite ceramic powder. After stirring was completed, the mixed slurry was suction filtered, washed, and spray dried at 80°C to obtain Chi-Pt coated composite ceramic powder 2#. Step three, 300g of Chi-Pt coated composite ceramic powder 2# was added to a high-speed mixing and dispersing machine, and 0.3wt% (4-vinylphenyl) trimethoxysilane was used to dry-modify the Chi-Pt coated composite ceramic powder at a rotation speed of 2500r / min for 5min to obtain modified composite ceramic powder 2#. Specific embodiment 3: The difference between this embodiment 3 and embodiment 1 is that the modified composite ceramic powder prepared in step (1) is different, and the other steps and amounts are consistent with embodiment 1. The method for preparing the modified composite ceramic powder in this embodiment 3 is as follows: Step one, 20g of chitosan powder was added to a round-bottom flask containing 1L of 10mmol / L aqueous chloroplatinic acid solution, and stirring was performed for 1.0h to fully dissolve the chitosan powder, obtaining Chi-Pt complex solution 3#. Step two, 300g of wollastonite, 50g of low-melting-point glass powder, 50g of aluminum hydroxide, 50g of calcium carbonate, 25g of mica powder, and 25g of expanded perlite were added to the Chi-Pt complex solution 3#. After stirring and dispersing for 0.5h, the pH of the solution was adjusted to 7.0 with 0.5mol / L ammonia water and stirring was continued for 1h, allowing the Chi-Pt complex to slowly precipitate from the solution onto the surface of the composite ceramic powder. The pH of the solution was then adjusted to 8.0 with 0.5mol / L ammonia water and stirring was continued for 1.0h, allowing the Chi-Pt complex to quickly precipitate from the solution and form a Chi-Pt complex coating layer on the surface of the composite ceramic powder. After stirring was completed, the mixed slurry was suction filtered, washed, and spray dried at 80°C to obtain Chi-Pt coated composite ceramic powder 3#. Step three, 300g of Chi-Pt coated composite ceramic powder 3# was added to a high-speed mixing and dispersing machine, and 0.3wt% (4-vinylphenyl) trimethoxysilane was used to dry-modify the Chi-Pt coated composite ceramic powder at a rotation speed of 2500r / min for 5min to obtain modified composite ceramic powder 3#. Specific embodiment 4 The difference between this embodiment 4 and embodiment 1 is that the modified composite ceramic powder prepared in step (1) is different, and the other steps and amounts are consistent with embodiment 1. The method for preparing the modified composite ceramic powder in this embodiment 4 is as follows: Step one, add 10g chitosan powder to a round-bottom flask containing 1L of 5mmol / L aqueous chloroplatinic acid solution, stir for 1.0h to fully dissolve the chitosan powder, and obtain Chi-Pt complex solution 1#. Step two, add 300g wollastonite, 25g low-melting-point glass powder, 50g aluminum hydroxide, 25g calcium carbonate, 50g mica powder, and 50g expanded perlite to the Chi-Pt complex solution 1#, stir for 0.5h to disperse, then adjust the solution pH to 7.0 with 0.5mol / L ammonia water and continue stirring for 1h, so that the Chi-Pt complex slowly precipitates from the solution onto the surface of the composite ceramic powder. Adjust the solution pH to 8.0 with 0.5mol / L ammonia water and continue stirring for 1.0h, so that the Chi-Pt complex quickly precipitates from the solution and forms a Chi-Pt complex coating layer on the surface of the composite ceramic powder. After stirring, the mixed slurry is filtered, washed, and spray dried at 80℃ to obtain Chi-Pt coated composite ceramic powder 4#. Step three, add 300g Chi-Pt coated composite ceramic powder 4# to a high-speed mixing and dispersing machine, and use 0.3wt% (4-vinylphenyl) trimethoxysilane to modify the Chi-Pt coated composite ceramic powder by dry method, with a rotation speed of 2500r / min and a mixing time of 5min, to obtain modified composite ceramic powder 4#. Specific embodiment 5 The difference between this embodiment 5 and embodiment 1 is that the colloidal B prepared in step (3) is different, and the other steps and amounts are consistent with embodiment 1. The method for preparing colloidal B in this embodiment 5 is as follows: (3) Add 100 parts of colloidal A to a kneader, add 2 parts of B component curing agent, knead for 0.5h, then add 200 parts of composite modified ceramic powder 1#, and knead for 3h to obtain colloidal B-2#.

[0023] Comparative example 1: The difference between this comparative example 1 and embodiment 1 is that the modified composite ceramic powder prepared in step (1) is different, and the method for preparing the modified composite ceramic powder in this comparative example 1 is as follows (ordinary chitosan coating, chloroplatinic acid is changed to dilute hydrochloric acid, i.e. no Pt complex chitosan): (1) Preparation of the modified composite ceramic powder: Step one, add 10g chitosan powder to a round-bottom flask containing 1L of 5mmol / L dilute hydrochloric acid solution, stir for 1.0h to fully dissolve the chitosan powder, and obtain chitosan aqueous solution. Step 2: Add 300g wollastonite, 50g low-melting-point glass powder, 50g aluminum hydroxide, 50g calcium carbonate, 25g mica powder, and 25g expanded perlite to the chitosan aqueous solution. After stirring and dispersing for 0.5h, adjust the pH of the solution to 7.0 with 0.5mol / L ammonia and continue stirring for 1h to allow chitosan to slowly precipitate from the solution onto the surface of the composite ceramic powder. Adjust the pH of the solution to 8.0 with 0.5mol / L ammonia and continue stirring for 1.0h to allow chitosan to precipitate rapidly from the solution and form a chitosan coating layer on the surface of the composite ceramic powder. After stirring, filter and wash the mixed slurry, and spray dry it at 80℃ to obtain Chi-coated composite ceramic powder. Step 3: Add 300g of Chi-coated composite ceramic powder to a high-speed mixer and disperser. Use 0.3wt% (4-vinylphenyl)trimethoxysilane to dry modify the Chi-coated composite ceramic powder. The speed is 2500r / min and the mixing time is 5min to obtain modified composite ceramic powder 5#.

[0024] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that the modified composite ceramic powder prepared in step (1) is different. The method for preparing the modified composite ceramic powder in Comparative Example 2 is as follows (without expanded perlite): Step 1: In a round-bottom flask containing 1L of 5mmol / L chloroplatinic acid aqueous solution, add 10g of chitosan powder and stir for 1.0h to fully dissolve the chitosan powder, thus obtaining Chi-Pt complex solution 1#. Step 2: Add 325g wollastonite, 50g low-melting-point glass powder, 50g aluminum hydroxide, 50g calcium carbonate, and 25g mica powder to Chi-Pt complex solution 1#. After stirring and dispersing for 0.5h, adjust the pH of the solution to 7.0 with 0.5mol / L ammonia and continue stirring for 1h to allow the Chi-Pt complex to slowly precipitate from the solution onto the surface of the composite ceramic powder. Adjust the pH of the solution to 8.0 with 0.5mol / L ammonia and continue stirring for 1.0h to allow the Chi-Pt complex to precipitate rapidly from the solution, forming a Chi-Pt complex coating layer on the surface of the composite ceramic powder. After stirring, filter and wash the mixed slurry, and spray dry at 80℃ to obtain Chi-Pt coated composite ceramic powder 5#. Step 3: Add 300g of Chi-Pt coated composite ceramic powder 5# to a high-speed mixer and disperser. Use 0.3wt% (4-vinylphenyl)trimethoxysilane to dry modify the Chi-Pt coated composite ceramic powder 5#. The speed is 2500r / min and the mixing time is 5min to obtain modified composite ceramic powder 6#.

[0025] Comparative Example 3: The difference between the present comparative example 3 and example 1 is that the modified composite ceramic powder prepared in step (1) is different, and the method for preparing the modified composite ceramic powder in the present comparative example 3 is as follows (without mica powder): Step one, 10 g of chitosan powder was added into a round bottom flask containing 1 L of 5 mmol / L aqueous chloroplatinic acid solution, and the chitosan powder was fully dissolved by stirring for 1.0 h to obtain a Chi-Pt complex solution 1#. Step two, 325 g of wollastonite, 50 g of low-melting-point glass powder, 50 g of aluminum hydroxide, 50 g of calcium carbonate, and 25 g of expanded perlite were added into the Chi-Pt complex solution 1#, and the mixture was stirred and dispersed for 0.5 h. Then, the pH of the solution was adjusted to 7.0 with 0.5 mol / L ammonia water, and the stirring was continued for 1 h to allow the Chi-Pt complex to slowly precipitate from the solution onto the surface of the composite ceramic powder. Then, the pH of the solution was adjusted to 8.0 with 0.5 mol / L ammonia water, and the stirring was continued for 1.0 h to allow the Chi-Pt complex to quickly precipitate from the solution and form a Chi-Pt complex coating layer on the surface of the composite ceramic powder. After the stirring was completed, the mixed slurry was suction filtered, washed, and spray dried at 80°C to obtain a Chi-Pt coated composite ceramic powder 6#. Step three, 300 g of the Chi-Pt coated composite ceramic powder 6# was added into a high-speed mixing and dispersing machine, and the Chi-Pt coated composite ceramic powder 6# was modified by dry method using 0.3 wt% (4-vinylphenyl) trimethoxysilane at a rotation speed of 2500 r / min for 5 min to obtain a modified composite ceramic powder 7#.

[0026] Comparative example 4: The difference between the present comparative example 4 and example 1 is that the modified composite ceramic powder prepared in step (1) is different, and the method for preparing the modified composite ceramic powder in the present comparative example 4 is as follows (without using (4-vinylphenyl) trimethoxysilane modification): Step one, 10 g of chitosan powder was added into a round bottom flask containing 1 L of 5 mmol / L aqueous chloroplatinic acid solution, and the chitosan powder was fully dissolved by stirring for 1.0 h to obtain a Chi-Pt complex solution 1#. Step two, 300g of wollastonite, 50g of low-melting-point glass powder, 50g of aluminum hydroxide, 50g of calcium carbonate, 25g of mica powder, and 25g of expanded perlite were added to the Chi-Pt complex solution 1#. After stirring and dispersing for 0.5h, the solution pH was adjusted to 7.0 with 0.5mol / L ammonia water and stirring was continued for 1h, allowing the Chi-Pt complex to slowly precipitate from the solution onto the surface of the composite ceramic powder. The solution pH was then adjusted to 8.0 with 0.5mol / L ammonia water and stirring was continued for another 1.0h, causing the Chi-Pt complex to rapidly precipitate from the solution and form a Chi-Pt complex coating layer on the surface of the composite ceramic powder. After stirring was completed, the mixed slurry was filtered and washed, and then spray dried at 80°C to obtain Chi-Pt coated composite ceramic powder 8#.

[0027] Comparative Example 5: Comparative Example 5 differs from Example 1 in that the modified composite ceramic powder prepared in Step (1) is different. The method for preparing the modified composite ceramic powder in Comparative Example 5 is as follows (without chitosan): In a high-speed mixing and dispersing machine, 300g of composite ceramic powder was added, with a ratio of 180g of wollastonite, 30g of low-melting-point glass powder, 30g of aluminum hydroxide, 30g of calcium carbonate, 15g of mica powder, and 15g of expanded perlite. The composite ceramic powder was modified using 0.3wt% (4-vinylphenyl) trimethoxysilane by dry modification, with a rotation speed of 2500r / min and a mixing time of 5min, to obtain modified composite ceramic powder 9#.

[0028] Comparative Example 6: Comparative Example 6 uses commercially available ceramic powder instead of the "modified composite ceramic powder" prepared in Example 1. The preparation method of the ceramicizable silicone rubber in Comparative Example 6 is as follows: (1) In a kneader, 100 parts of silicone rubber raw rubber, 40 parts of reinforcing filler, and 3 parts of hydroxyl silicone oil were added and kneaded for 2h to obtain Gel A; (2) In a kneader, 100 parts of Gel A and 2 parts of B component curing agent were added and kneaded for 0.5h. Then, 100 parts of commercially available ceramic powder was added and kneaded for 2h to obtain Gel B3#; (3) 100 parts of Gel B3# was added to a double roller open mill, 0.5 parts of A component curing agent was added, and the rubber was evenly opened for 15min. The roller gap was adjusted to 3mm to obtain ceramicizable silicone rubber 2#; (4) The ceramicizable silicone rubber 2# was placed on a calendering line, the thickness was controlled to 2mm by double rollers, and vulcanization was carried out at 150°C for 10min to obtain a ceramicizable silicone rubber sheet 2# after primary vulcanization.

[0029] The performance test method is as follows: Vertical flame retardant performance: The vertical flame retardant grade was determined according to GB / T2408-2008. Ceramization performance test: The butane torch was used as heat source, the flame length was about 10-15 cm, the distance between the torch mouth and the sample was 5-7 cm, and the sample was burned for 30 min. The ceramization of the sample was observed, and the ceramization was divided into three levels: ceramization integrity, ceramization crack and ceramization breakdown. The ceramization integrity means that the surface of the ceramizable silicone rubber prepared by the example is relatively complete after the butane torch burning test, and has no obvious defects; the ceramization crack means that the surface of the ceramizable silicone rubber prepared by the example has obvious cracks after the butane torch burning test; and the ceramization breakdown means that the surface of the ceramizable silicone rubber prepared by the example has obvious holes and cracks after the butane torch burning test. Three-point bending strength test: The sample was placed in a 900℃ muffle furnace, and then the three-point bending strength of the ceramizable silicone rubber composite tape after burning was determined according to GBT 1965-1996 after being kept for 1 h. Method for measuring the highest temperature of the back surface of the silicone rubber during burning: The butane torch was used as heat source, the flame length was about 10-15 cm, the distance between the torch mouth and the sample was 5-7 cm, and the sample was burned for 30 min. The temperature of the flame of the torch was measured by a K-type thermocouple before the test, and the temperature of the flame was required to be in the range of 1250-1350℃. Two or more K-type thermocouples were fixed on the back surface of the ceramizable silicone rubber at the burning position to form a temperature measuring array, so as to observe the temperature change of the back surface of the silicone rubber during burning, and record the highest temperature of the back surface. Sample residual weight rate test: The residual weight rate of each silicone rubber sample after being heated from room temperature to 1300℃ was determined according to GB / T 27762-2011.

[0030] Table 1 Performance comparison of examples 1-5 and comparative examples 1-6

[0031] According to the performance test data of Examples 1-5 and Comparative Examples 1-6 in Table 1, the fire-resistant and heat-insulating porcelainizable silicone rubber prepared by the present application exhibits significantly better comprehensive performance than the comparative samples. The vertical combustion flame-retardant grade of Examples 1-5 reaches UL94 V-0 standard, the ceramic layer remains intact during combustion, the three-point bending strength is as high as 48.834 MPa, the maximum back temperature is only 287℃ (excellent heat insulation performance), and the residual weight rate is stable at more than 85%; while the vertical combustion flame-retardant grade of Comparative Examples 1-6 does not reach UL94 V-0, the ceramic performance is generally cracking or even breakdown, the three-point bending strength is only in the range of 16-31 MPa, the maximum back temperature is as high as 486℃, and the maximum residual weight rate is 84.1558% with large fluctuations. The excellent performance of Examples 1-5 is due to the synergistic effect of multiple factors: first, the continuous porous carbon layer formed by chitosan component at high temperature not only serves as a bonding agent for modified composite ceramic powder to fill the voids between the powder, but also improves the fire resistance of the ceramic layer; second, the multiple heat insulation interfaces formed by expanded perlite, flaky mica powder and chitosan carbon layer delay the transmission of high temperature to the internal substrate; third, the secondary composite modification process for ceramic powder optimizes the compatibility, dispersibility and thermal stability of the powder, and finally prepares a fire-resistant and heat-insulating porcelainizable silicone rubber with good flame-retardant performance, excellent heat insulation performance and high porcelain strength.

[0032] Obviously, the above examples of the present application are only examples for clearly illustrating the technical solutions of the present application, and are not intended to limit the specific embodiments of the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A fire-resistant, heat-insulating, ceramizable silicone rubber, characterized in that, Includes the following components by weight: 100 parts of raw silicone rubber; 20-50 parts of reinforcing filler; 100-300 parts of modified composite ceramic powder; Component A curing agent: 0.25–1 part; Component B curing agent: 0.5–2 parts; The modified composite ceramic powder is prepared by the following method: first, chitosan and chloroplatinic acid are coordinated to form a chitosan-platinum complex, then the composite ceramic powder is coated with the complex once, and finally the composite ceramic powder after the first coating is coated with vinylphenylsiloxane a second time. The composite ceramic powder is composed of the following components by weight percentage: 50-75% wollastonite, 1-10% low-melting-point glass powder, 5-15% aluminum hydroxide, 5-15% calcium carbonate, 5-10% mica powder, and 5-10% expanded perlite.

2. The fire-resistant, heat-insulating, ceramizable silicone rubber according to claim 1, characterized in that, The raw silicone rubber is methyl-terminated or vinyl-terminated methyl vinyl silicone raw rubber; the reinforcing filler is one or a combination of two of fumed silica and precipitated silica.

3. The fire-resistant, heat-insulating, ceramizable silicone rubber according to claim 1, characterized in that, The wollastonite has a needle-like morphology with a particle size D50 of 3–15 μm and an aspect ratio of 2:1–20:1; the low-melting-point glass powder has a particle size D50 of 5–10 μm; the aluminum hydroxide has a particle size D50 of 1–15 μm; the calcium carbonate has a particle size D50 of 1–15 μm; the mica powder has a platy morphology with a particle size D50 of 3–25 μm; and the closed-cell perlite has a particle size D50 of 20–50 μm.

4. The fire-resistant, heat-insulating, ceramizable silicone rubber according to claim 1, characterized in that, The curing agent of component A is a mixture of platinum complex and polysiloxane; the curing agent of component B is a mixture containing crosslinking agent, inhibitor and polysiloxane.

5. A method for preparing the fire-resistant, heat-insulating, ceramizable silicone rubber as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Prepare the modified composite ceramic powder according to claim 1; (2) Add 100 parts of raw silicone rubber, 20-50 parts of reinforcing filler and 3-5 parts of hydroxyl silicone oil to a kneader and knead for 2-4 hours to obtain colloid A; (3) Add 100 parts of colloid A and 0.5 to 2 parts of component B curing agent to the kneader, knead for 0.5 to 1 hour, then gradually add 100 to 300 parts of composite modified ceramic powder and continue kneading for 1 to 4 hours to obtain colloid B. (4) Add 100 parts of colloid B to a two-roll mill, add 0.25 to 1 part of component A curing agent, and mill for 5 to 15 minutes to mix the rubber material evenly. Adjust the roller gap to 0.5 to 5 mm to obtain fire-resistant, heat-insulating, ceramic-compatible silicone rubber material. (5) The fire-resistant, heat-insulating, ceramic-like silicone rubber material is placed on a calendering line, and the thickness is controlled by two rollers to be 0.1-10 mm. It is vulcanized at 120-160℃ for 5-15 min and obtained by one vulcanization molding.

6. The method according to claim 5, characterized in that, The specific preparation method of the modified composite ceramic powder mentioned in step (1) is as follows: Step 1: In a round-bottom flask containing 1L of chloroplatinic acid aqueous solution with a concentration of 1-10mmol / L, add 5-25g of chitosan powder and stir for 0.5-1.0h to fully dissolve the chitosan powder to obtain a chitosan-platinum complex solution; wherein the chitosan powder has a particle size D50 of 15-50μm, a degree of deacetylation of 85-95%, and a molecular weight of <150000Da. Step 2: Add 200-500g of composite ceramic powder to the chitosan-platinum complex solution, stir and disperse for 0.5-1.0h, adjust the pH of the solution to 6.5-7.0 with 0.5-1.0mol / L ammonia water, and continue stirring for 1h to allow the chitosan-platinum complex to slowly precipitate from the solution onto the surface of the composite ceramic powder. Adjust the pH of the solution to 8.0-8.5 with 0.5-1.0mol / L ammonia water, and continue stirring for 0.5-1.0h to allow the chitosan-platinum complex to precipitate rapidly from the solution, forming a chitosan-platinum complex coating layer on the surface of the composite ceramic powder. After stirring, filter and wash the mixed slurry, and spray dry at 80-100℃ to obtain Chi-Pt coated composite ceramic powder. Step 3: Add 150-300g of composite ceramic powder to a high-speed mixer and disperser, and then add 0.1wt%-1.0wt% of (4-vinylphenyl)trimethoxysilane according to the mass of the composite ceramic powder. Mix at a speed of 2000-3000r / min for 3-10min for dry modification to obtain modified composite ceramic powder.

Images