Flame-retardant and heat-insulating silicone rubber composition as well as preparation method and application thereof

Abstract

The invention provides a flame-retardant and heat-insulating silicone rubber composition. The flame-retardant and heat-insulating silicone rubber composition is prepared from the following raw materials: 100 parts of rubber compound, 50-100 parts of aluminum hydroxide, 10-50 parts of ceramic powder, 1-8 parts of silane treating agent and 0.5-5 parts of platinum composition, wherein the rubber compound is polysiloxane which takes Si-O-Si as a main chain and takes hydroxyl, phenyl, fluoro or vinyl as a side chain; the ceramic powder is a compound comprising mica powder, calcium silicate, white carbon black and a silane coupling agent. According to the flame-retardant and heat-insulating silicone rubber composition disclosed by the invention, under the condition that the addition amount of aluminum hydroxide is reduced, the flame-retardant grade reaches UL94V-0 grade, and the flame-retardant and heat-insulating silicone rubber composition is heat-insulating and flame-retardant.

Description

Technical Field

[0001] The present invention belongs to the field of silicone rubber, and in particular relates to a flame retardant and heat-insulating silicone rubber composition, a preparation method thereof, and applications thereof. Background Art

[0002] New energy vehicles are developing rapidly, but new energy battery packs are prone to internal heating, creating a large temperature difference between the inside and outside of the battery pack. This in turn causes the air inside the pack to condense, forming condensed water. This condensed water can easily drip onto the battery cells, causing them to short-circuit and overheat, rapidly heating the battery pack. This seriously reduces the battery pack's operational stability and can even cause fires. The explosion temperature of lithium batteries is generally 500°C, so the battery frame must isolate heat transfer and have a certain degree of flame retardancy.

[0003] To address these issues, existing technologies incorporate a thermal insulation cushioning layer into new energy battery cells. This provides insulation and cushioning protection, reducing the temperature difference between the inside and outside of the battery pack and providing flame retardancy in the event of a fire. Silicone rubber is a semi-organic, semi-inorganic polymer with a main chain composed of alternating Si-O-Si bonds and organic groups attached to the side chains. Silicone rubber possesses many unique properties, including excellent dielectric properties, thermal insulation, and high elasticity. Therefore, silicone rubber is suitable as a thermal insulation cushioning material for new energy battery cells. However, silicone rubber has low initial strength and lacks flame retardancy, making it difficult to provide flame retardant protection. Current thermal insulation requirements for protective rubber frames for new energy batteries are as follows: Place temperature sensors on both sides of the sample and place it on a platform heated to 600°C. Apply a pressure of 1 MPa and time the temperature of the other side to ≤ 300°C after 10 minutes. Flame retardancy requirements: UL94 V-0 flame retardancy rating.

[0004] The existing method for improving the fire retardancy of silicone rubber is to add aluminum hydroxide. However, this has the following drawbacks: 1. The addition ratio is relatively high, generally exceeding 60% by mass. However, aluminum hydroxide is not a very good reinforcing filler, and adding such a high ratio deteriorates the mechanical properties of the silicone rubber. 2. After combustion, flame-retardant rubber containing only aluminum hydroxide has poor porcelain strength and low compressive strength, resulting in cracking with even the slightest compression, seriously affecting battery cell safety and failing to meet the requirements of new energy battery packs. 3. Aluminum hydroxide is a highly thermally conductive filler. Adding large amounts of it to silicone rubber enhances its thermal conductivity but impairs its insulation. Abnormal heating in a single cell can quickly transfer heat to adjacent cells, triggering a chain reaction. Consequently, many studies have explored different combinations of aluminum hydroxide. Patent CN115449225B provides a lightweight, low-smoke, fire-resistant, and thermally insulating silicone rubber material and its preparation method, which exhibit low density, low smoke toxicity, and excellent fire and thermal insulation properties. The porcelain filler includes sericite powder and silicon micropowder in a mass ratio of 1:1 to 2:1. The compound flux includes two low-melting-point glass powders, the melting points of the two low-melting-point glass powders are 500-600°C and 700-800°C, respectively, and are compounded in a mass ratio of 1:2 to 2:1. However, this solution is only applicable to the aerospace field, and is used to insulate heat transfer after a fire to resist further ablation and prevent high-temperature flames or gases in the fire zone from entering other areas and causing harm. It is difficult to apply to battery packs. Patent CN115029000B uses hydroxymethyl compounds for flame retardancy and silica aerogel powder as a reinforcing agent. At the same time, it itself has a flame retardant effect of physical barrier and can reduce the thermal conductivity of room temperature vulcanized silicone foam. This patent prepares a highly flame-retardant, high-strength, low-thermal-conductivity room temperature vulcanized silicone foam.

[0005] Therefore, for the field of new energy batteries, it is necessary to provide a new silicone rubber composition that has a low proportion of aluminum hydroxide added, good flame retardant properties and low thermal conductivity, and has a certain strength after vitrification. Summary of the Invention

[0006] The present invention provides a flame-retardant and heat-insulating silicone rubber composition. When the battery temperature is abnormal, within the range of 60°C to 250°C, the flame-retardant and heat-insulating silicone rubber composition provides low thermal conductivity and insulation without degradation. At temperatures above 250°C, the silicone rubber enhances its flame retardancy, providing fire protection. The hollow structure and ceramic layer provide support and insulation. This invention is suitable for use in thermal protection systems within battery packs, specifically in situations where the battery overheats abnormally, preventing fires and blocking heat transfer to protect the battery pack.

[0007] The basic concept of the technical solution adopted in the present invention is as follows:

[0008] A flame-retardant and heat-insulating silicone rubber composition, the raw materials of which include the following components:

[0009]

[0010] The rubber compound is a polysiloxane with Si-O-Si as the main chain and hydroxyl, phenyl, fluoro or vinyl as the side chain;

[0011] The ceramic powder is a compound comprising mica powder, calcium silicate, white carbon black and a silane coupling agent.

[0012] As one mode, the platinum composition is a compound comprising platinum, benzotriazole and raw rubber; preferably, the addition amount of the platinum composition is 1-3 parts.

[0013] As a method, the particle size of aluminum hydroxide is 1-10 μm.

[0014] As one embodiment, the silane treating agent is selected from one or a combination of monomethyltrimethoxysilane, dimethyldimethoxysilane, vinyltriethoxysilane, dimethyldiphenylsilane or methyltriphenylsilane.

[0015] As one approach, in the ceramic powder, the ratio of mica powder, calcium silicate, white carbon black and silane coupling agent is (10-30):(30-40):(30-40):1, preferably 20:40:40:1.

[0016] Preferably, the added amount of the ceramic powder is 10-30 parts.

[0017] As one embodiment, in the platinum composition, per 100 parts of raw rubber, the content of benzotriazole is 3-2 parts, and the content of platinum is 300-2000 ppm. Preferably, the content of platinum is 500 ppm.

[0018] The present invention also provides a method for preparing the flame-retardant and heat-insulating silicone rubber composition as described in any one of the above contents, comprising the following steps:

[0019] Step 1: Add the rubber mix, aluminum hydroxide and silane treatment agent into a kneader;

[0020] Step 2: Heat the kneader to 130-150°C, evacuate to <-0.07 MPa, and knead for 1-3 hours;

[0021] Step 3: Cool to room temperature, add the ceramic powder into the kneader in several batches, and knead into a ball;

[0022] Step 4: Add the platinum composition into a kneader and knead into a dough.

[0023] The present invention further provides a use of the flame retardant and heat-insulating silicone rubber composition as described in any one of the above contents, that is, using the flame retardant and heat-insulating silicone rubber composition for thermal protection of new energy batteries.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. The silicone rubber composition of this invention solves the problem that existing flame-retardant silicone rubbers, even when added with aluminum hydroxide, lack thermal insulation, or when added with thermal insulation fillers, lack adequate flame retardancy. Furthermore, while reducing the amount of aluminum hydroxide added, the flame retardancy rating reaches UL94 V-0.

[0026] 2. The silicone rubber composition of the present invention forms a ceramic hollow structure after combustion, which can block long-term combustion and provide fireproof and heat-insulating protection for each battery cell.

[0027] 3. The flame retardant in the silicone rubber composition of this invention is composed of aluminum hydroxide and ceramic powder, which not only improves flame retardancy but also forms a C-Si-O ceramic layer after ceramicization, providing physical support for the hard shell. Furthermore, under high temperatures, the polymer decomposes, forming a hollow structure with the outer layer, which provides thermal insulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0029] Figure 1 This is an electron microscope image of the fire-retardant silicone rubber composition of Example 1 of the present invention after combustion (combustion conditions: methane gas, combustion temperature 1400° C.-1800° C., flame height 20 mm).

[0030] Figure 2 This is an electron microscope image of ordinary flame-retardant silicone rubber (Xin'an Chemical Product, Model WRB-Z150-50B) after the same combustion. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions of the embodiments of the present invention in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In the present invention, unless otherwise specified, the "parts" in the following embodiments are "parts by weight". The measurement units of "parts" or "parts by weight" in the same embodiment are unified, which is the same as the idea of the technical solution defined by specific measurement units and does not affect its feasibility.

[0033] The rubber compound used in the following examples is a polysiloxane with a Si-O-Si backbone and vinyl and methyl side chains. Silica (a component of the rubber compound) is added to enhance physical properties. The specific rubber compound used in the following examples is XHG-151, a commercially available product from Zhejiang Xin'an Chemical Industry Group Co., Ltd.

[0034] For the platinum composition, as an example, a commercially available product (model: FE450) of Zhejiang Xin'an Chemical Group Co., Ltd. (mainly a compound of platinum, benzotriazole, raw rubber, etc., with a platinum content of 500 ppm) is directly used, and the addition amount is 0.5-5 parts, preferably 1-3 parts.

[0035] The particle size of aluminum hydroxide is preferably 1-10 μm. When subjected to high temperature, it decomposes to produce water, thereby improving the flame retardant properties of silicone rubber. The added amount is 50-100 parts.

[0036] Ceramic powder is commercially available, specifically FD040 produced by Guangdong Xinyida Co., Ltd. The addition of ceramic powder allows the silicone rubber to decompose into silica at high temperatures, transforming it into a hard shell that provides physical support and forms a hollow structure, reducing thermal conductivity and insulation. The powder is primarily a mixture of mica powder, calcium silicate, white carbon black, and a silane coupling agent (specifically, in a mass ratio of 20:40:40:1). The addition amount is 10-50 parts, preferably 10-30 parts.

[0037] The silane treatment agent is selected from monomethyltrimethoxysilane, dimethyldimethoxysilane, vinyltriethoxysilane, dimethyldiphenylsilane or methyltriphenylsilane. The silane treatment agent can make the powder disperse evenly, and the added amount is 1-8 parts.

[0038] Example 1

[0039] Step 1: Add 100 parts of rubber mix, 70 parts of aluminum hydroxide, and 1 part of vinyltriethoxysilane (silane treatment agent) into a vacuum kneader, wherein the aluminum hydroxide is added in 4 portions;

[0040] Step 2: After the materials are mixed evenly, the kneader is heated to 140°C, vacuumed to -0.08 MPa, and kneaded for 2 hours;

[0041] Step 3: After cooling to room temperature, add 15 parts of ceramic powder in two portions, mix evenly, and knead into a mass;

[0042] Step 4: Add 1 part of the platinum composition to obtain a rubber compound.

[0043] Examples 2-4 and Comparative Examples 1-4 were all obtained according to the above method. The raw material components of the products are shown in Table 1 below (all units of measurement are parts by weight).

[0044] Table 1

[0045]

[0046] Effect Examples

[0047] After the products of Examples 1-4 and Comparative Examples 1-4 were vulcanized, their properties were tested.

[0048] The vulcanization conditions are: adding 1.5% of dipentadienyl vulcanizing agent (effective content 40%), and vulcanizing at 170°C*10min.

[0049] Thermal insulation test method: 100*100*4.55mm sample; place temperature sensors on both sides of the sample and place it on a platform heated to 600℃. Compress the thickness to 4mm and time it for 10 minutes. The test is considered passed if the cold surface temperature is ≤250℃ after 10 minutes.

[0050] Table 2

[0051]

[0052] From the above experimental data, we can know that:

[0053] Based on the technical solution of the present invention, Examples 1-4 obtained flame-retardant and heat-insulating silicone rubber with excellent physical properties, passed the UL94 V-0 rating and heat insulation test, and met the application requirements of thermal protection of new energy battery cells.

[0054] Compared with Example 1, the amount of ceramic powder added in Comparative Example 1 is too small. Although the thermal conductivity of the prepared rubber material is low, it does not form porcelain and cannot meet the thermal insulation requirements.

[0055] Compared with Example 1, in Comparative Example 2, no platinum composition was added. In this case, the flame retardant grade of the prepared rubber material did not reach the V-0 level.

[0056] Compared with Example 1, the amount of aluminum hydroxide added in Comparative Example 3 is too small. In this case, although it can pass the thermal insulation test, the flame retardant grade is not enough and cannot meet the requirements.

[0057] Compared with Example 1, in Comparative Example 4, excessive aluminum hydroxide was added. In this case, the flame retardant grade of the prepared rubber material reached V-0 and was able to pass the thermal insulation test, but the mechanical properties were very poor, and the thermal conductivity of the silica gel was too high, which could not meet the application conditions.

Claims

1. A flame retardant and heat-insulating silicone rubber composition, characterized in that: The raw materials include the following components: The rubber compound is a polysiloxane with Si-O-Si as the main chain and hydroxyl, phenyl, fluoro or vinyl as the side chain; The ceramic powder is a compound comprising mica powder, calcium silicate, white carbon black and a silane coupling agent.

2. The flame retardant and heat-insulating silicone rubber composition according to claim 1, characterized in that: The platinum composition is a compound comprising platinum, benzotriazole and raw rubber; preferably, the added amount of the platinum composition is 1-3 parts.

3. The flame retardant and heat-insulating silicone rubber composition according to claim 1, characterized in that: The particle size of aluminum hydroxide is 1-10um.

4. The flame retardant and heat-insulating silicone rubber composition according to claim 1, characterized in that: The silane treating agent is selected from one or a combination of monomethyltrimethoxysilane, dimethyldimethoxysilane, vinyltriethoxysilane, dimethyldiphenylsilane or methyltriphenylsilane.

5. The flame retardant and heat insulating silicone rubber composition according to claim 1, characterized in that: In the ceramic powder, the ratio of mica powder, calcium silicate, white carbon black and silane coupling agent is (10-30):(30-40):(30-40):1, preferably 20:40:40:

1.

6. The flame retardant and heat insulating silicone rubber composition according to claim 1, characterized in that: The added amount of the ceramic powder is 10-30 parts.

7. The flame retardant and heat insulating silicone rubber composition according to claim 2, characterized in that: In the platinum composition, the content of benzotriazole is 3-2 parts per 100 parts of raw rubber, and the content of platinum is 300-2000ppm.

8. The flame retardant and heat insulating silicone rubber composition according to claim 2, characterized in that: The platinum content is 500ppm.

9. The method for preparing the flame retardant and heat insulating silicone rubber composition according to any one of claims 1 to 8, characterized in that: The steps include: Step 1: Add the rubber mix, aluminum hydroxide and silane treatment agent into a kneader; Step 2: Heat the kneader to 130-150°C, evacuate to <-0.07 MPa, and knead for 1-3 hours; Step 3: Cool to room temperature, add the ceramic powder into the kneader in several batches, and knead into a ball; Step 4: Add the platinum composition into a kneader and knead into a dough.

10. Use of the flame retardant and heat insulating silicone rubber composition according to any one of claims 1 to 8, characterized in that: The flame-retardant and heat-insulating silicone rubber composition is used for heat protection of new energy batteries.

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