Single-component room temperature vulcanized silicone rubber adhesive and preparation method thereof

Abstract

The invention relates to the technical field of adhesives, in particular to a single-component room temperature vulcanized silicone rubber adhesive and a preparation method thereof. The silicone-modified silicone rubber comprises the following components in parts by weight: 100 parts of alpha, omega-dihydroxy polydimethylsiloxane, 10-20 parts of silicone oil, 60-140 parts of an inorganic filler, 0.5-3 parts of a carbon reinforcing material, 0.05-0.5 part of a coupling agent, 3-10 parts of a cross-linking agent, 1-5 parts of a tackifier and 0.1-2 parts of a catalyst, the tackifier comprises linear alkyl triethoxy silane substituted by a single primary amino group. The tackifier in the components is selected from single primary amino substituted linear alkyl triethoxy silane, can balance the bonding performance of the adhesive, and is especially suitable for bonding of the inner wall (butyl film) of a tire; the content of the tackifier in the components is 0.8-1.5 wt%, and the mechanical property and the bonding strength of the adhesive can be improved at the same time.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, specifically to a one-component room temperature vulcanizing silicone rubber adhesive and its preparation method. Background Technology

[0002] One-component room temperature vulcanizing (RTV-1) silicone rubber adhesives are widely used in various fields such as electronic and electrical packaging, automotive manufacturing, building sealing, and new energy equipment protection because they can cure at room temperature without additional heating or mixing, are easy to use, and possess excellent weather resistance, high and low temperature resistance, and electrical insulation. Their core formulation typically uses hydroxyl-terminated polydimethylsiloxane or modified polysiloxane as the base adhesive, combined with silane crosslinking agents, amino or epoxy coupling agents, inorganic fillers (such as fumed silica, calcium carbonate, and alumina), and tin / titanium catalysts. The crosslinking reaction is initiated by ambient moisture to form an elastic adhesive layer. Existing alcohol-based one-component room temperature moisture-curing adhesives suffer from slow curing speeds, making it difficult to meet the rapid turnover requirements of industrial production, becoming a significant bottleneck in the application of this type of system. With the increasing demands for material performance in industrial applications, there is a growing trend towards targeted performance optimization, such as focusing on improving single indicators like thermal conductivity, heat resistance, transparency, or low hardness. Meanwhile, existing formulations suffer from uneven filler dispersion and insufficient synergistic effects of additives, potentially leading to poor product storage stability or performance degradation after long-term use. Furthermore, non-silicone rubber alternatives exist on the market, such as silane-terminated polyether sealants (MS sealants). However, the urethane and other low-bond-energy structures in MS sealants decompose to some extent at 90°C, easily causing sealant failure with prolonged high-temperature use; their temperature resistance is significantly inferior to silicone rubber systems. Additionally, MS sealants often use organotin catalysts, resulting in poor environmental performance. Another type of self-healing viscoelastic adhesive is mostly butyl rubber, which has poor high and low temperature resistance. At low temperatures, its adhesion decreases, leading to peeling; at high temperatures, it thins, causing slippage and resulting in unbalanced stress. Silicone rubber, on the other hand, can achieve long-term stable use from -40°C to 150°C, exhibiting a significant advantage in extreme temperature adaptability. Therefore, developing a single-component room-temperature vulcanizing silicone rubber adhesive that requires no special curing equipment, offers excellent synergistic performance across multiple properties, and has a simple process is a key direction for meeting the needs of practical industrial applications.

[0003] Chinese invention patent CN119193097B discloses a UV / moisture dual-curing high-strength neutral de-alcoholized RTV silicone rubber. This technology uses end-capped 107 adhesive as the base adhesive, combined with modified photoresist and photoinitiator, and achieves improved tensile strength and weather resistance through synergistic curing by UV light and moisture, making it suitable for bonding precision components where curing efficiency is required. However, some of its solutions employ a dual-curing system, which relies on UV irradiation equipment and is difficult to adapt to the bonding needs of concealed environments or complex structures. Single moisture-curing products often face the challenge of balancing curing rate and bonding strength, and most formulations focus on optimizing a single performance, making it difficult to simultaneously meet the multi-dimensional requirements of high bonding strength, aging resistance, low VOC emissions, and adaptability to extreme environments. Summary of the Invention

[0004] The first aspect of this invention provides a one-component room temperature vulcanizing silicone rubber adhesive, comprising, by weight: 100 parts of α,ω-dihydroxypolydimethylsiloxane, 10-20 parts of silicone oil, 60-140 parts of inorganic filler, 0.5-3 parts of carbon-based reinforcing material, 0.05-0.5 parts of coupling agent, 3-10 parts of crosslinking agent, 1-5 parts of tackifier, and 0.1-2 parts of catalyst; wherein the tackifier comprises a mono-primary amino-substituted linear alkyltriethoxysilane.

[0005] The viscosity of the α,ω-dihydroxy polydimethylsiloxane at 25°C is 30,000-80,000 cP.

[0006] The silicone oil has a viscosity of 50-300 cP at 25°C.

[0007] The inorganic filler is treated with fatty acids or coupling agents.

[0008] The content of the tackifier in the components is 0.8-1.5 wt%.

[0009] Optionally, the content of the tackifier in the component is 0.9-1.2 wt%.

[0010] The weight ratio of the coupling agent to the thickener is 0.2:(1.8-3.5).

[0011] Optionally, the weight ratio of the coupling agent to the thickener is 0.2:(2-3).

[0012] The weight ratio of the α,ω-dihydroxy polydimethylsiloxane, silicone oil and inorganic filler is 100:(12-18):(90-120).

[0013] Optionally, the weight ratio of the α,ω-dihydroxy polydimethylsiloxane, silicone oil and inorganic filler is 100:(12-18):(100-110).

[0014] The tackifier of this invention is selected from mono-primary amino-substituted linear alkyltriethoxysilanes, which can balance the adhesive performance of the adhesive, especially suitable for bonding butyl films. Mono-primary amino-substituted linear alkyltriethoxysilanes contain a primary amino group and three ethoxy groups. The primary amino group has moderate activity and the propyl chain has low steric hindrance, allowing it to undergo condensation reactions with the hydroxyl groups of α,ω-dihydroxypolydimethylsiloxane, and to form hydrogen bonds or chemical bonds with the polar groups of sound-absorbing cotton and tire inner walls. Simultaneously, the ethoxy groups have a mild hydrolysis rate, and the ethanol produced by hydrolysis has low volatility, preventing the formation of bubbles in the system. Furthermore, the synergistic reaction between the hydrolysis products and the base adhesive and inorganic fillers is stable, forming a dense and uniform Si-O-Si crosslinked network, balancing thixotropy and adhesive strength. In contrast, current technologies using diamino or amino-conjugated types suffer from problems such as excessively high amino activity leading to self-polymerization, or insufficient interfacial bonding due to excessively low activity; and due to their large steric hindrance structure, they suffer from insufficient effective contact reactions with the polar groups of the substrate.

[0015] The tackifier comprises mono-primary amino-substituted linear alkyltriethoxysilanes.

[0016] The mono-primary amino-substituted linear alkyl triethoxysilane includes at least one of 4-aminobutyltriethoxysilane, 5-aminopentyltriethoxysilane, 6-aminohexyltriethoxysilane, 2-aminoethyltriethoxysilane, and 7-aminoheptyltriethoxysilane.

[0017] The silicone oil includes at least one of methylphenyl silicone oil, dimethyl silicone oil, polyether-modified silicone oil, fluorine-modified silicone oil, and hydroxyl silicone oil.

[0018] The inorganic filler includes at least one of calcium carbonate, silica fume, fumed silica, precipitated silica, talc, and diatomaceous earth.

[0019] The coupling agent includes at least one of dodecyltrimethoxysilane, hexadecyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, tridecyltrimethoxysilane, and tetradecyltrimethoxysilane.

[0020] The crosslinking agent includes at least one of vinyltriisopropoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, vinyltritert-butoxysilane, and vinyltriisopropoxysilane.

[0021] The catalyst comprises at least one of tetramethylguanidinopropyltrimethoxysilane, 1,1,3,3-tetramethylguanidine, 2-guanidinoethyltrimethoxysilane, N,N-dimethylcyclohexylamine, N-ethylmorpholine, and 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0022] The carbon-based reinforcing material includes at least one of carbon black, graphite powder, carbon nanotubes, and carbon fiber powder.

[0023] The second aspect of the present invention provides a method for preparing a single-component room temperature vulcanizing silicone rubber adhesive, characterized by comprising the following steps: dispersing α,ω-dihydroxy polydimethylsiloxane, inorganic filler and carbon-based reinforcing material evenly to obtain a mixture, and then adding the remaining components to the mixture and dispersing them evenly.

[0024] Beneficial effects 1. The tackifier in the components of this invention is selected from mono-primary amino-substituted linear alkyltriethoxysilanes, which can balance the adhesive bonding performance and is especially suitable for bonding tire inner walls (butyl films).

[0025] 2. By limiting the content of the tackifier in the components to 0.8-1.5wt%, the mechanical properties and bond strength of the adhesive can be improved simultaneously.

[0026] 3. By using a weight ratio of coupling agent to tackifier of 0.2:(1.8-3.5), rapid curing can be achieved while improving workability (flowability).

[0027] 4. The adhesive of the present invention has a surface drying time of about 10 minutes at 25°C and 50%RH, which provides a better application window.

[0028] 5. According to GB / T528 testing, the adhesive of the present invention has a tensile strength ≥2.0MPa and an elongation at break ≥400%. Detailed Implementation

[0029] Examples 1-3, Comparative Examples 1-6 A one-component room temperature vulcanizing silicone rubber adhesive, the components of which are shown in Table 1 by weight, with blank spaces indicating no addition.

[0030] Table 1

[0031] The α,ω-dihydroxypolydimethylsiloxane is sourced from Shandong Dayi Chemical Co., Ltd., brand name: DY-OH501, with a viscosity of 50,000 cP at 25℃.

[0032] The dimethyl silicone oil is sourced from Shandong Dayi Chemical Co., Ltd., brand name: DY-201 silicone oil, with a viscosity of 100 cP at 25℃.

[0033] The calcium carbonate is sourced from Warner New Materials, brand name: CCS-30, and has undergone fatty acid treatment.

[0034] The carbon black is sourced from Cabot, grade: M900.

[0035] The coupling agent, dodecyltrimethoxysilane, is sourced from Hangzhou Jessica Chemical Co., Ltd.

[0036] The crosslinking agent, vinyltriisopropoxysilane, is sourced from Hubei Chengfeng Chemical Co., Ltd.

[0037] The tackifiers 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, anilinemethyltriethoxysilane, and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane are all sourced from Hangzhou Jessica Chemical Co., Ltd.

[0038] The catalyst, tetramethylguanidinopropyltrimethoxysilane, was obtained from Hangzhou Hairui Chemical Co., Ltd.

[0039] A method for preparing a one-component room temperature vulcanizing silicone rubber adhesive comprises the following steps: First, dry calcium carbonate at 70℃ for 2 hours. Then, add α,ω-dihydroxypolydimethylsiloxane, silicone oil, carbon black, calcium carbonate, and coupling agent in sequence, stirring gradually at low speed first and then high speed to obtain a mixture. Heat the mixture to 130℃, keep it at that temperature for 20 minutes, vacuum for 40 minutes, and then cool it to below 35℃. Pass the mixture through a three-roll mill to grind the particles. Heat it to 130℃, keep it at that temperature for 20 minutes, vacuum for 40 minutes, and then cool it to room temperature to obtain the masterbatch.

[0040] Stir under vacuum for 30 minutes, then stop stirring, purge with nitrogen, repeat the process of vacuuming and purging with nitrogen, and add the crosslinking agent first under nitrogen atmosphere and stir until homogeneous. Then add the remaining components, repeat the vacuuming and nitrogen purging process three times, stirring until homogeneous under nitrogen atmosphere. Let stand under nitrogen protection for 1 hour ± 20 minutes; then vacuum for 20 minutes while stirring. Turn off stirring and vacuum, purge with nitrogen, transfer to a press, vacuum again, and discharge to obtain the adhesive.

[0041] Performance testing methods The adhesives prepared in the examples and comparative examples were subjected to performance tests. The test data are listed in Table 2. Blank spaces indicate that no tests were performed.

[0042] The bonding performance test method is as follows: For butyl film as the substrate, apply an adhesive strip of about 2 mm thickness onto the butyl film. After the adhesive has cured for 24 hours, peel off the adhesive strip and observe whether the adhesive strip is completely destroyed. For sound-absorbing cotton as the substrate, apply an adhesive strip of about 2 mm thickness onto the sound-absorbing cotton. After the adhesive has fully cured for 24 hours, peel off the adhesive strip and observe whether the sound-absorbing cotton is torn off.

[0043] Performance test data Table 2

Claims

1. A one-component room temperature vulcanizing silicone rubber adhesive, characterized in that, By weight, the components include: 100 parts of α,ω-dihydroxypolydimethylsiloxane, 10-20 parts of silicone oil, 60-140 parts of inorganic filler, 0.5-3 parts of carbon-based reinforcing material, 0.05-0.5 parts of coupling agent, 3-10 parts of crosslinking agent, 1-5 parts of tackifier, and 0.1-2 parts of catalyst; the tackifier includes mono-primary amino-substituted linear alkyltriethoxysilane.

2. The single-component room temperature vulcanizing silicone rubber adhesive according to claim 1, characterized in that, The content of the tackifier in the components is 0.8-1.5 wt%.

3. The single-component room temperature vulcanizing silicone rubber adhesive according to claim 2, characterized in that, The content of the tackifier in the components is 0.9-1.2 wt%.

4. The single-component room temperature vulcanizing silicone rubber adhesive according to claim 1 or 3, characterized in that, The weight ratio of the coupling agent to the thickener is 0.2:(1.8-3.5).

5. The single-component room temperature vulcanizing silicone rubber adhesive according to claim 4, characterized in that, The weight ratio of the coupling agent to the thickener is 0.2:(2-3).

6. The single-component room temperature vulcanizing silicone rubber adhesive according to claim 5, characterized in that, The mono-primary amino-substituted linear alkyl triethoxysilane includes at least one of 4-aminobutyltriethoxysilane, 5-aminopentyltriethoxysilane, 6-aminohexyltriethoxysilane, 2-aminoethyltriethoxysilane, and 7-aminoheptyltriethoxysilane.

7. The single-component room temperature vulcanizing silicone rubber adhesive according to claim 1, characterized in that, The silicone oil includes at least one of methylphenyl silicone oil, dimethyl silicone oil, polyether-modified silicone oil, fluorine-modified silicone oil, and hydroxyl silicone oil.

8. The single-component room temperature vulcanizing silicone rubber adhesive according to claim 1, characterized in that, The inorganic filler includes at least one of calcium carbonate, silica fume, fumed silica, precipitated silica, talc, and diatomaceous earth.

9. The single-component room temperature vulcanizing silicone rubber adhesive according to claim 1, characterized in that, The weight ratio of the α,ω-dihydroxy polydimethylsiloxane, silicone oil and inorganic filler is 100:(12-18):(90-120).

10. A method for preparing a single-component room-temperature vulcanizing silicone rubber adhesive according to any one of claims 1-9, characterized in that, Includes the following steps: α,ω-dihydroxypolydimethylsiloxane, inorganic filler, and carbon-based reinforcing material are dispersed evenly to obtain a mixture. The remaining components are then added to the mixture and dispersed evenly.

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