A low-density, flowable flame-retardant sealant and its preparation method

Abstract

This application discloses a low-density, flowable flame-retardant sealant and its preparation method. The sealant comprises the following raw materials in parts by weight: base adhesive: 100 parts; polydimethylsiloxane: 5-30 parts; flame retardant: 50-120 parts; crosslinking agent: 3-7 parts; coupling agent: 0.5-1 part; curing agent: 2-5 parts. The flame retardant is a flame retardant powder, liquid flame retardant, and hollow glass microspheres in a mass ratio of 20-60:10-20:20-40. The sealant of this application possesses excellent flame retardant properties, flowability, and low density, making it suitable for manufacturing in the electric vehicle field.

Description

Technical Field

[0001] This application relates to the field of silicone sealants, and in particular to a low-density, flowable, flame-retardant sealant and its preparation method. Background Technology

[0002] Sealant is widely used in the auxiliary manufacturing of electric vehicles due to its superior structural toughness, fatigue resistance, impact resistance, and corrosion resistance. In recent years, with the increasing penetration and popularity of new energy vehicles, especially electric vehicles, the development of electric vehicles has placed higher demands on high energy density, long driving range, and low power consumption per 100 kilometers. As the core component of electric vehicles, the power battery typically accounts for 20-35% of the total vehicle weight, making the lightweight development of power battery systems particularly important.

[0003] At the same time, due to the special nature of power batteries, the sealant is required to have excellent flame retardant properties to ensure that the power battery has a certain ability to block combustion when encountering special situations such as impact, short circuit and fire; in addition, as a sealant for potting, it should have a certain fluidity to ensure its penetration and sealing effect. Summary of the Invention

[0004] The purpose of this application is to develop a low-density, flowable flame-retardant sealant and its preparation method, which has the advantages of being lightweight, flame-retardant and highly flowable, and can be adapted to the sealing and bonding of power batteries.

[0005] In a first aspect, this application provides a low-density, flowable, flame-retardant sealant, comprising the following raw materials in parts by weight:

[0006] Base adhesive: 100 parts;

[0007] Polydimethylsiloxane: 5-30 parts;

[0008] Flame retardant: 50-120 parts;

[0009] Crosslinking agent: 3-7 parts;

[0010] Coupling agent: 0.5–1 part;

[0011] Hardener: 2-5 parts;

[0012] The flame retardant is a mixture of flame retardant powder, liquid flame retardant, and hollow glass microspheres in a mass ratio of 20-60:10-20:20-40.

[0013] The aforementioned flame-retardant powder, liquid flame retardant, and hollow glass microspheres all possess excellent flame-retardant properties. Their combined effect imparts a superior flame-retardant rating to the sealant. Secondly, due to the large amount of flame retardant used in this application, a significant number of hollow glass microspheres are employed to balance the overall flame-retardant performance and density of the sealant, ensuring its low-density and lightweight characteristics. Thirdly, the smooth and flat surface of the hollow glass microspheres helps improve the sealant's flowability. Combined with the diluting effect of some of the liquid flame retardant, this effectively ensures the overall flowability of the sealant. Finally, the polydimethylsiloxane added in this application has a diluting effect, promoting the flow and penetration of the sealant during application.

[0014] In summary, this application, by using appropriate proportions of flame-retardant powder, liquid flame retardant, and hollow glass microspheres, can obtain a sealant that simultaneously possesses low density, high flame retardancy, and excellent flowability.

[0015] Preferably, the viscosity of polydimethylsiloxane at 25°C is 100–500 cp, more preferably 200–400 cp, and most preferably 350 cp.

[0016] Preferably, the base adhesive is α,ω-dihydroxypolydimethylsiloxane, and the base adhesive comprises base adhesive I and base adhesive II in a mass ratio of 1 to 10:1. The viscosity of base adhesive I at 25°C is 100 to 1000 cp, and the viscosity of base adhesive II at 25°C is 5000 to 80000 cp.

[0017] Using a large amount of low-viscosity base adhesive helps reduce the mixed viscosity of the sealant and improves its flowability. However, the use of a large amount of low-viscosity, low-molecular-weight base adhesive and a large amount of flame retardant results in extremely high rigidity and increased brittleness after curing, which is detrimental to ensuring its strength properties. Using an appropriate amount of high-viscosity, high-molecular-weight base adhesive can improve the elasticity of the cured sealant, ensuring its shear strength, elongation at break, tensile strength, and other strength indicators.

[0018] Preferably, the raw material of the sealant further includes 5 to 20 parts of methoxy-terminated polydimethylsiloxane, which has a viscosity of 20 to 200 cp, more preferably 20 to 100 cp, and its structural formula is as follows:

[0019]

[0020] The addition of the above-mentioned methoxy-terminated polysiloxanes can effectively adjust the crosslinking density of the sealant, reduce its rigidity after curing, and compensate for its elasticity and toughness.

[0021] The aforementioned methoxy-terminated polydimethylsiloxane can be made from alkoxy silicone oils produced by Runhe Organosilicon, including models such as RH-Z30 and RH-Z50.

[0022] Preferably, the raw materials of the sealant further include 1 to 4 parts of a chain extender, wherein the chain extender is a difunctional siloxane.

[0023] The chain-extending effect of chain extenders helps improve the elasticity of sealants and enhance their strength properties.

[0024] Preferably, the chain extender is selected from one or more of dimethyldimethoxysilane, dimethyldiethoxysilane, methylvinyldimethoxysilane, and methylvinyldiethoxysilane.

[0025] Preferably, the crosslinking agent is selected from one or more of methyl orthosilicate, ethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and phenyltrimethoxysilane.

[0026] Preferably, the coupling agent is selected from one or more of aminosilane coupling agents, epoxysilane coupling agents, and isocyanate-based silane coupling agents.

[0027] Preferably, the coupling agent is selected from one or more of 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-isocyanopropyltrimethoxysilane, and 3-isocyanopropyltriethoxysilane.

[0028] Preferably, the curing agent is a titanate curing agent.

[0029] Preferably, the flame retardant powder is aluminum hydroxide; and / or the liquid flame retardant is one or more of tricresyl phosphate, triisopropylphenyl phosphate, triphenyl phosphate, and toluene diphenyl phosphate; and / or the hollow glass microspheres have a D50 particle size of 20-60 μm.

[0030] The flame retardant powder has a particle size of less than 25 μm, preferably a blend of nano- and micron-sized inorganic flame retardant powder particles; more preferably, the micron-sized flame retardant powder has a particle size of 5-20 μm.

[0031] Secondly, this application provides a method for preparing a low-density, flowable, flame-retardant sealant, characterized by comprising the following steps:

[0032] Step 1: Mix the base adhesive, polydimethylsiloxane, and flame retardant according to the formula, dehydrate and disperse them under heating and vacuum conditions, and obtain mixture A after cooling;

[0033] Step 2: Add crosslinking agent and chain extender to mixture A, mix evenly under vacuum to obtain mixture B;

[0034] Step 3: Add coupling agent and curing agent to mixture B, and mix evenly under vacuum conditions to obtain the final product.

[0035] Preferably, the heating temperature in step 1 is 100-150°C.

[0036] Preferably, the vacuum degree in steps 1, 2, and 3 is -0.08 to -0.1 MPa.

[0037] Preferably, the dehydration and dispersion time in step 1 is 90–240 min.

[0038] Preferably, the mixing time for steps 2 and 3 is 20 to 60 minutes, more preferably 30 to 40 minutes.

[0039] In summary, this application has the following beneficial effects:

[0040] 1. The flame retardant of this application is preferably a combination of flame retardant powder, liquid flame retardant and hollow glass microspheres to obtain a sealant that has excellent flame retardant, flowability and low density properties.

[0041] 2. This application, by selecting low-viscosity and high-viscosity base adhesives together and supplementing them with polydimethylsiloxane and liquid flame retardant, can effectively compensate for the loss of flowability caused by the addition of a large amount of flame retardant.

[0042] 3. This application utilizes methoxy-terminated polysiloxanes to effectively adjust the crosslinking density of the sealant, reduce its rigidity after curing, and compensate for its elasticity and toughness. Detailed Implementation

[0043] Example

[0044] Example 1: A low-density, flowable flame-retardant sealant was prepared according to the following steps:

[0045] Step 1: Add 800g of α,ω-dihydroxypolydimethylsiloxane (viscosity 500cp), 200g of α,ω-dihydroxypolydimethylsiloxane (viscosity 20000cp), 150g of polydimethylsiloxane (viscosity 350cp), 400g of aluminum hydroxide (D50 particle size 8μm), 100g of aluminum hydroxide (D50 particle size 20μm), 400g of hollow glass microspheres (D50 particle size 45μm), and 150g of triisopropylphenyl phosphate to a planetary disperser. Dehydrate and disperse the mixture for 180min at a temperature of 120-130℃ and a vacuum degree of -0.08-0.1MPa. After cooling, obtain mixture A.

[0046] Step 2: Add 35g of methyltrimethoxysilane, 10g of methyltriethoxysilane, 20g of dimethyldimethoxysilane and 50g of methoxy-terminated polydimethylsiloxane (viscosity 30cp) to mixture A, and stir for 30-40 minutes under a vacuum of -0.08 to -0.1MPa to obtain mixture B.

[0047] Step 3: Add 4g of 3-glycidyl etheroxypropyltrimethoxysilane, 4g of 3-aminopropyltriethoxysilane and 30g of di(ethyl acetoacetate)titanium diisopropyl ester to mixture B, and stir for 30-40 minutes under a vacuum of -0.08 to -0.1 MPa to obtain a low-density flowable flame-retardant sealant.

[0048] Example 2: A low-density, flowable flame-retardant sealant was prepared according to the following steps:

[0049] Step 1: Add 750g of α,ω-dihydroxypolydimethylsiloxane (viscosity 500cp), 250g of α,ω-dihydroxypolydimethylsiloxane (viscosity 10000cp), 300g of polydimethylsiloxane (viscosity 350cp), 280g of aluminum hydroxide (D50 particle size 8μm), 220g of hollow glass microspheres (D50 particle size 45μm), and 170g of triphenyl phosphate to a planetary disperser. Dehydrate and disperse the mixture for 180min at a temperature of 120-130℃ and a vacuum degree of -0.08-0.1MPa. After cooling, obtain mixture A.

[0050] Step 2: Add 35g of methyltrimethoxysilane, 10g of phenyltrimethoxysilane, 20g of dimethyldimethoxysilane and 100g of methoxy-terminated polydimethylsiloxane (viscosity 55cp) to mixture A, and stir for 30-40 minutes under a vacuum of -0.08 to -0.1MPa to obtain mixture B.

[0051] Step 3: Add 4g of 3-aminopropyltriethoxysilane, 3g of 3-isocyanate-propyltrimethoxysilane and 25g of di(ethyl acetoacetate)titanium diisopropyl ester to mixture B, and stir for 30-40 minutes under a vacuum of -0.08 to -0.1 MPa to obtain a low-density flowable flame-retardant sealant.

[0052] Example 3: A low-density, flowable flame-retardant sealant was prepared according to the following steps:

[0053] Step 1: Add 550g of α,ω-dihydroxypolydimethylsiloxane (viscosity 100cp), 450g of α,ω-dihydroxypolydimethylsiloxane (viscosity 80000cp), 200g of polydimethylsiloxane (viscosity 350cp), 250g of aluminum hydroxide (D50 particle size 8μm), 50g of aluminum hydroxide (D50 particle size 20μm), 200g of hollow glass microspheres (D50 particle size 45μm), 100g of hollow glass microspheres (D50 particle size 25μm), and 170g of tricresyl phosphate to a planetary disperser. Dehydrate and disperse the mixture for 180min at a temperature of 120-130℃ and a vacuum degree of -0.08-0.1MPa. After cooling, obtain mixture A.

[0054] Step 2: Add 25g of methyltrimethoxysilane, 10g of phenyltrimethoxysilane, 10g of vinyltrimethoxysilane, 20g of dimethyldimethoxysilane and 200g of methoxy-terminated polydimethylsiloxane (viscosity 100cp) to mixture A, and stir for 30-40 minutes under a vacuum of -0.08 to -0.1MPa to obtain mixture B.

[0055] Step 3: Add 4g of 3-glycidyl etheroxypropyltrimethoxysilane, 4g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 30g of di(ethyl acetoacetate)titanium diisopropyl ester to mixture B, and stir for 30-40 minutes under a vacuum of -0.08 to -0.1 MPa to obtain a low-density flowable flame-retardant sealant.

[0056] Example 4, a low-density flowable flame-retardant sealant, differs from Example 3 in that an equal amount of base adhesive (α,ω-dihydroxypolydimethylsiloxane) with a viscosity of 500 cp is used instead of a base adhesive with a viscosity of 100 cp, and an equal amount of base adhesive (α,ω-dihydroxypolydimethylsiloxane) with a viscosity of 5000 cp is used instead of a base adhesive with a viscosity of 80000 cp.

[0057] Example 5 is a low-density, flowable flame-retardant sealant, which differs from Example 4 in that no chain extender is added.

[0058] Example 6, a low-density flowable flame-retardant sealant, differs from Example 4 in that it uses methoxy-terminated polydimethylsiloxane with a viscosity of 200 cp.

[0059] Example 7, a low-density, flowable flame-retardant sealant, differs from Example 4 in that it does not contain methoxy-terminated polydimethylsiloxane.

[0060] Comparative Example

[0061] Comparative Example 1, a low-density flowable flame-retardant sealant, differs from Example 1 in that it uses an equal amount of aluminum hydroxide (D50 particle size 8μm) instead of hollow glass microspheres.

[0062] Comparative Example 2, a low-density flowable flame-retardant sealant, differs from Example 1 in that an equal amount of aluminum hydroxide (D50 particle size 20 μm) is used instead of triisopropylphenyl phosphate (liquid flame retardant).

[0063] Comparative Example 3, a low-density flowable flame-retardant sealant, differs from Example 1 in that equal amounts of aluminum hydroxide (D50 particle size 20 μm) and aluminum hydroxide (D50 particle size 8 μm) are used to replace hollow glass microspheres and triisopropylphenyl phosphate (liquid flame retardant), respectively.

[0064] Comparative Example 4, a low-density flowable flame-retardant sealant, differs from Example 1 in that it uses equal amounts of hollow glass microspheres (D50 particle size of 45 μm) and liquid flame retardant (mass ratio of 3:1) instead of aluminum hydroxide.

[0065] Performance testing

[0066] 1. Flame retardant performance: Tested according to the vertical method in GB / T 2408-2021.

[0067] 2. Flow performance: Fill a 5ml syringe with a certain amount of sealant, ensuring that there are no air bubbles in the sealant. Place a 20cm×20cm transparent PE film flat on the experimental table. Apply 1ml of sealant from the syringe onto the transparent PE film, ensuring that the nozzle is 2-3cm away from the transparent PE film. After 10 minutes, measure the maximum and minimum widths of the sealant spread pattern and record the average value as the spreading diameter R. Repeat this process three times and take the average value as the average spreading diameter Ra.

[0068] 3. Density: Tested according to the provisions of GB / T13477-2002.

[0069] 4. Adhesive shear strength Al-Al: Tested according to GB / T 7124-2008.

[0070] 5. Tensile strength and elongation at break: Tested according to GB / T 528-2009.

[0071] 6. Hardness: Tested according to GB / T 531.1-2008.

[0072] Table 1. Experimental Results

[0073]

[0074] Analysis of experimental results:

[0075] (1) As can be seen from Examples 1-7 and Comparative Examples 1-4, and Table 1, the flame retardant of this application uses flame retardant powder, liquid flame retardant and hollow glass microspheres in combination, and is supplemented with polydimethylsiloxane, which can effectively balance the density, flowability and flame retardant properties of the sealant. A sealant with excellent flame retardant effect, construction performance and lightweight characteristics is obtained.

[0076] (2) As can be seen from Examples 1 and 5 and Table 1, this application can effectively compensate for the loss of colloidal elasticity caused by the use of low molecular weight base glue and a large amount of flame retardant by using chain extender.

[0077] (3) As can be seen from Examples 1 and 6-7 and Table 1, this application improves the elasticity of the sealant and enhances the fatigue resistance and shock absorption performance of the sealing structure by adding small molecule methoxy-terminated polydimethylsiloxane.

[0078] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A low-density, flowable, flame-retardant sealant, characterized in that, The raw materials include the following parts by weight: Base adhesive: 100 parts; Polydimethylsiloxane: 5-30 parts; Flame retardant: 70-160 parts; Crosslinking agent: 3-7 parts; Coupling agent: 1-3 parts; Hardener: 2-5 parts; The flame retardant is a flame retardant powder, liquid flame retardant, and hollow glass microspheres in a mass ratio of 40-80:10-30:20-50; the base adhesive is α,ω-dihydroxy polydimethylsiloxane and / or alkoxy-terminated polysiloxane, and the base adhesive includes base adhesive I and base adhesive II in a mass ratio of 1-10:1, the viscosity of base adhesive I at 25°C is 100-1000cp, and the viscosity of base adhesive II at 25°C is 5000-80000cp; The raw materials of the sealant also include 1 to 4 parts of chain extender, wherein the chain extender is a difunctional siloxane; The hollow glass microspheres have a D50 particle size of 20–60 μm.

2. The low-density, flowable, flame-retardant sealant according to claim 1, characterized in that, The raw materials for the sealant also include 5 to 20 parts of methoxy-terminated polydimethylsiloxane with a viscosity of 20 to 200 cp, with the following structural formula:

3. The low-density, flowable, flame-retardant sealant according to claim 1, characterized in that, The chain extender is selected from one or more of dimethyldimethoxysilane, dimethyldiethoxysilane, methylvinyldimethoxysilane, and methylvinyldiethoxysilane.

4. The low-density, flowable, flame-retardant sealant according to claim 1, characterized in that, The crosslinking agent is selected from one or more of methyl orthosilicate, ethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and phenyltrimethoxysilane.

5. The low-density, flowable, flame-retardant sealant according to claim 1, characterized in that, The coupling agent is selected from one or more of aminosilane coupling agents, epoxysilane coupling agents, and isocyanate-based silane coupling agents.

6. The low-density, flowable, flame-retardant sealant according to claim 1, characterized in that, The curing agent is a titanate curing agent.

7. The low-density, flowable, flame-retardant sealant according to claim 1, characterized in that, The flame retardant powder is one of aluminum hydroxide and magnesium hydroxide or a combination thereof; and / or the liquid flame retardant is one or more of tricresyl phosphate, triisopropylphenyl phosphate, triphenyl phosphate, and toluene diphenyl phosphate.

8. A method for preparing the low-density, flowable, flame-retardant sealant as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: Mix the base adhesive, polydimethylsiloxane, and flame retardant according to the formula, dehydrate and disperse them under heating and vacuum conditions, and obtain mixture A after cooling; Step 2: Add crosslinking agent and chain extender to mixture A, mix evenly under vacuum to obtain mixture B; Step 3: Add coupling agent and curing agent to mixture B, and mix evenly under vacuum conditions to obtain the final product.

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