A silicone sealant composition for anti-fog vehicle lights and its preparation method
By using a polyalkyloxysilane derivative prepared by a tertiary amine polyol and an isocyanate-based silane coupling agent as a second crosslinking agent, combined with α,ω-dihydroxy polydimethylsiloxane with low D3-D10 content, the problems of fogging and slow curing speed of vehicle lights were solved, achieving anti-fogging effect and rapid curing of vehicle lights.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGXI BLUESTAR XINGHUO SILICONE CO LTD
- Filing Date
- 2023-11-01
- Publication Date
- 2026-06-30
AI Technical Summary
Existing silicone sealants have high volatile content in automotive lights, causing them to fog up, and they also have a slow curing speed, resulting in poor overall performance.
A polyalkyloxysilane derivative was prepared by reacting a tertiary amine polyol with an isocyanate-based silane coupling agent as a second crosslinking agent, and combined with α,ω-dihydroxy polydimethylsiloxane with low D3-D10 content as a base adhesive to reduce volatile matter and maintain a fast curing speed.
It effectively reduces the fogging phenomenon of vehicle lights, while maintaining a fast curing speed and excellent mechanical properties, thus extending the shelf life.
Abstract
Description
Technical Field
[0001] This invention belongs to the field of silicone sealant technology, specifically relating to a silicone sealant composition for anti-fog vehicle lights and its preparation method. Background Technology
[0002] Vehicle lights are one of the most important safety devices in a vehicle, and silicone sealant is a key technology in vehicle light manufacturing. Silicone sealant is a special adhesive made from silicone polymers. It possesses excellent adhesion, resistance to high and low temperatures, weather resistance, chemical corrosion resistance, and good mechanical properties. It effectively protects the internal electronic circuitry and light source of the vehicle lights from external environmental influences, thereby ensuring stable and normal operation of the lights and improving vehicle safety and reliability.
[0003] De-alcoholized room temperature vulcanizing silicone sealant is a commonly used silicone sealant for bonding and sealing automotive lights. It is formulated with α,ω-dihydroxy polydimethylsiloxane as the base, supplemented with crosslinking agents, catalysts, fillers, etc. After mixing, the crosslinking agent and the base sealant undergo a condensation reaction to generate active silicone-terminated hydroxyl-terminated polydimethylsiloxane. The latter reacts with moisture in the air to crosslink and cure. De-alcoholized room temperature vulcanizing silicone sealant exhibits no irritating acidic odor during the entire curing process, is non-corrosive to metals, has good adhesion, and does not crack, making it a type of room temperature vulcanizing sealant with good overall performance. However, this type of room temperature vulcanizing silicone sealant contains a large amount of low-volatile components, such as siloxane cyclic compounds D3-D10 and low-molecular-weight siloxanes, which gradually escape from the sealant and adhere to the car lights, causing fogging and reduced light transmittance, posing a significant safety hazard. Researchers in this field have conducted extensive improvement studies. For example, patent CN107880841B discloses an anti-fog automotive light silicone sealant and its preparation method, which includes the following components by weight: 10-30 parts of alkoxy-terminated 107 silicone rubber with a capacity of 80,000-5,000,000 mPa·s, 10-40 parts of alkoxy-terminated 107 silicone rubber with a capacity of 1,000-80,000 mPa·s, 30-50 parts of calcium powder, 1-10 parts of fumed silica, 1-10 parts of carbon paste, 1-5 parts of macromolecular crosslinking agent, 1-5 parts of coupling agent, and 0.1-5 parts of catalyst. This technology reduces volatile content by first hydrolyzing and condensing small-molecule volatile crosslinking agents into low-molecular-weight oligomers (polymethyltrimethoxysiloxane) with a degree of polymerization of 2-50, which are less volatile. Although this makes the headlights less prone to fogging, as the degree of polymerization increases, the structure of the macromolecular crosslinking agent becomes more complex (with the appearance of large side groups, side chains, and cyclic siloxane structures). This reduces the activity of the reactive groups on the crosslinking agent, slows down the hydrolysis rate, and greatly reduces the curing speed. Patent CN102277126B discloses a single-component, alcohol-free silicone sealant for automotive lights and its preparation method. The method involves taking 90-110 parts of α,ω-dihydroxy polydimethylsiloxane with a viscosity of 15000-80000 mPa·s, 120-150 parts of pre-dried stearic acid-treated nano-activated calcium carbonate, 10-20 parts of carbon black, 5-20 parts of methyl silicone oil, 5-30 parts of crosslinking agent, 2-5 parts of fumed silica, 0.01-10 parts of catalyst, and 0.1-1 parts of tackifier. The mixture is stirred and mixed under a vacuum of 0.06-0.1 MPa for 30-40 minutes. After removing low-molecular-weight substances under a vacuum of 0.08-0.1 MPa, the mixture is discharged and filled. This technology reduces the volatilization of low-molecular-weight siloxane and lowers the probability of fogging by adding tackifiers containing amino groups that can form hydrogen bonds, but the actual effect is not satisfactory.
[0004] Therefore, it is of great significance to develop an organosilicon sealant that can reduce volatile content, prevent car lights from fogging, and has a fast curing speed, with excellent overall performance. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides an organosilicon sealant composition for anti-fog vehicle lights and its preparation method. It utilizes a polyalkyloxysilane derivative prepared from a tertiary amine polyol and an isocyanate-based silane coupling agent as a non-volatile second crosslinking agent. This crosslinking agent not only has high activity and does not reduce the curing speed, but also reduces the amount of the volatile first crosslinking agent while maintaining mechanical properties. Furthermore, using α,ω-dihydroxy polydimethylsiloxane with low D3-D10 content as the base adhesive further reduces volatile content, making the vehicle lights less prone to fogging.
[0006] To achieve the above objectives, the following technical solution is adopted:
[0007] A silicone sealant composition for anti-fog vehicle lights comprises the following components: α,ω-dihydroxy polydimethylsiloxane, a first crosslinking agent, a second crosslinking agent, a catalyst, a filler, a coupling agent, and a plasticizer. The first crosslinking agent has 3 alkoxy functional groups, the second crosslinking agent has ≥4 alkoxy functional groups, and the α,ω-dihydroxy polydimethylsiloxane has a D3-D10 content of 0.01-0.05 wt%.
[0008] Further, it includes the following components in parts by weight: 100 parts α,ω-dihydroxypolydimethylsiloxane, 1-3 parts first crosslinking agent, 1-2 parts second crosslinking agent, 1-3 parts catalyst, 50-150 parts filler, 1-3 parts coupling agent, and 3-10 parts plasticizer.
[0009] The first crosslinking agent is selected from one or a combination of two or more of methyltrimethoxysilane, vinyltrimethoxysilane, propyltrimethoxysilane, octyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, and phenyltrimethoxysilane.
[0010] The viscosity of the α,ω-dihydroxypolydimethylsiloxane is 20,000-100,000 cps.
[0011] The catalyst is selected from one or a combination of two of organotin compounds, titanates, titanate complexes, and platinum catalysts.
[0012] Furthermore, the catalyst is an organotin compound selected from one or a combination of two of dibutyltin dilaurate, dibutyltin diacetate, and stannous octoate.
[0013] The filler is selected from one or a combination of two of calcium carbonate and precipitated silica; the average particle size of the filler is 0.1-100 μm, and the specific surface area of the precipitated silica is 50-400 m². 2 / g.
[0014] The coupling agent is selected from one or a combination of two of cyanoalkoxysilanes and aminoalkoxysilanes.
[0015] The cyanoalkoxysilane is selected from one or a combination of two or more of γ-cyanopropyltriethoxysilane, β-cyanoethyltriethoxysilane, β-cyanoethylmethyldimethoxysilane, β-cyanoethyltrimethoxysilane, and β-cyanoethylmethyldiethoxysilane; the aminoalkoxysilane is selected from one or a combination of two or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β(aminoethyl)-γ-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldiethoxysilane, phenylaminomethyltriethoxysilane, and phenylaminomethyltrimethoxysilane.
[0016] The plasticizer has an apparent viscosity of 35-350 mPa·s at 25°C and is selected from one or more combinations of alkyl aromatic compounds, dimethyl silicone oil, alkanes, α,ω-dimethoxy polydimethylsiloxane, and MDT-type silicone oil.
[0017] The second crosslinking agent is a polyalkyloxysilane derivative prepared by reacting a tertiary amine polyol with an isocyanate-based silane coupling agent.
[0018] The molar ratio of alcohol hydroxyl groups to isocyanate groups in the tertiary amine polyol-isocyanate silane coupling agent is 1:1.10-1.16.
[0019] The tertiary amine polyol is selected from one or a combination of two or more of the following: triethanolamine, 2-(dimethylamino)-2-(hydroxymethyl)-1,3-propanediol, 1-dimethylamino-2-(hydroxymethyl)propane-1,3-diol, N,N,N',N'-tetrahydroxyethylethylenediamine, N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine, hydroxyethyl diisopropanolamine, dihydroxyethyl tert-butanolamine, and ethylenediaminetetrapropanol.
[0020] The isocyanate-based silane coupling agent is selected from one or a combination of two or more of (3-propyl isocyanate)triethoxysilane, methyl isocyanatetriethoxysilane, 3-propyl isocyanatetrimethoxysilane, and propyl isocyanatemethyldiethoxysilane.
[0021] The second crosslinking agent is prepared by a method comprising the following steps:
[0022] Under dry inert gas conditions, tertiary amine polyol, isocyanate-based silane coupling agent, and catalyst are mixed evenly, heated and kept at a constant temperature, and the reaction is carried out under stirring. After the reaction is completed, the second crosslinking agent is obtained by vacuum distillation.
[0023] The catalyst is selected from dibutyltin dilaurate and stannous octoate. The amount of the catalyst is 0.01-0.03 wt% of the weight of the tertiary amine polyol and the isocyanate-based silane coupling agent. The temperature is raised to 50-100℃ and the reaction time is 1-5 h.
[0024] The present invention also provides a method for preparing the above-mentioned silicone sealant composition for anti-fog vehicle lights, comprising the following steps:
[0025] 1) Mix α,ω-dihydroxypolydimethylsiloxane, filler, and plasticizer evenly;
[0026] 2) Add the first crosslinking agent and the second crosslinking agent to the mixture from step 1), and mix thoroughly;
[0027] 3) Add the catalyst and coupling agent to the mixture in step 2), mix well, cool, discharge, and package.
[0028] Step 1) The mixing temperature is 100-120℃, the time is 1-3h, and the vacuum degree is 0.01-0.1MPa;
[0029] Step 2) The mixing temperature is 20-30℃, the time is 10-30 min, and the vacuum degree is 0.01-0.1 MPa;
[0030] Step 3) The mixing temperature is 20-40℃, the time is 1-3h, and the vacuum degree is 0.01-0.1MPa.
[0031] Compared with the prior art, the beneficial effects of the present invention are:
[0032] This invention utilizes polyalkyloxysilane derivatives prepared from tertiary amine polyols and isocyanate-based silane coupling agents as a secondary crosslinking agent that is not easily volatile. This crosslinking agent not only has high activity and does not reduce the reaction rate, but also reduces the amount of the easily volatile primary crosslinking agent while maintaining mechanical properties. At the same time, the use of α,ω-dihydroxy polydimethylsiloxane with low D3-D10 content as the base adhesive can further reduce the volatile content, making the headlights less prone to fogging.
[0033] The inventors discovered that the second crosslinking agent has the effect of synergistically improving the curing speed at room temperature (20-30°C, for example 25°C) with organotin compounds. Detailed Implementation
[0034] The present invention will be further described below with reference to specific embodiments, but is not limited to the contents of the specification. Unless otherwise specified, all "parts" mentioned in the embodiments of the present invention are parts by weight. All reagents used are commercially available in the art.
[0035] α,ω-dihydroxypolydimethylsiloxane H48V20000, with a viscosity of 10000cps and a D3-D10 content of 1wt%, was purchased from Jiangxi Lanxing Xinghuo Organosilicon Co., Ltd.
[0036] α,ω-dihydroxypolydimethylsiloxane P48V20000, viscosity 20000cps, D3-D10 content 0.03wt%, purchased from Jiangxi Lanxing Xinghuo Organosilicon Co., Ltd.
[0037] α,ω-Dihydroxypolydimethylsiloxane HP48V80000, viscosity 80000cps, D3-D10 content 0.03wt%, purchased from Jiangxi Lanxing Xinghuo Organosilicon Co., Ltd.
[0038] Calcium carbonate CCS-25 was purchased from Guangxi Huana New Materials Co., Ltd.
[0039] The dimethyl silicone oil had an apparent viscosity of 100 mPa·s at 25°C and was purchased from Jiangxi Lanxing Xinghuo Organosilicon Co., Ltd.
[0040] Preparation of the second crosslinking agent
[0041] Preparation Example 1
[0042] Under a dry nitrogen atmosphere, 1 mol of N,N,N',N'-tetrahydroxyethylethylenediamine, 4.4 mol of isocyanate methyltriethoxysilane, and 0.36 g of dibutyltin dilaurate were mixed evenly, heated to 85°C and kept at a constant temperature, and reacted for 5 h under stirring. After the reaction was completed, the second crosslinking agent was obtained by vacuum distillation.
[0043] Preparation Example 2
[0044] Under a dry nitrogen atmosphere, 1 mol of triethanolamine, 3.45 mol of isocyanate methyltriethoxysilane, and 0.27 g of dibutyltin dilaurate were mixed evenly, heated to 80°C and kept at a constant temperature, and reacted for 5 h under stirring. After the reaction was completed, the second crosslinking agent was obtained by vacuum distillation.
[0045] Preparation of silicone sealant composition
[0046] Example 1
[0047] 1) Mix 50 parts of P48V20000, 50 parts of HP48V80000, 100 parts of calcium carbonate CCS-25, and 6 parts of dimethyl silicone oil in a high-speed mixer that can be heated and vacuumed for 3 hours at 120℃ and a vacuum degree of 0.090MPa until they are homogeneous.
[0048] 2) Add 3 parts of vinyltrimethoxysilane and 2 parts of the second crosslinking agent prepared in Preparation Example 1 to the mixture in step 1), and stir and mix for 30 min at room temperature and vacuum degree of 0.050 MPa until homogeneous;
[0049] 3) Add 3 parts of dibutyltin dilaurate and 3 parts of γ-cyanopropyltriethoxysilane to the mixture in step 2), and stir for 2 hours at 25°C and 0.085 MPa until the mixture is homogeneous. Cool, discharge and package.
[0050] Example 2
[0051] The rest is the same as in Example 1, except that the second crosslinking agent is prepared in Preparation Example 2.
[0052] Example 3
[0053] The rest is the same as in Example 1, except that the amount of the second crosslinking agent prepared in Example 1 is 1 part.
[0054] Example 4
[0055] The rest is the same as in Example 1, except that the amount of the second crosslinking agent prepared in Example 1 is 0.5 parts.
[0056] Example 5
[0057] The rest is the same as in Example 1, except that the amount of the second crosslinking agent prepared in Example 1 is 4 parts.
[0058] Example 6
[0059] The rest is the same as in Example 1, except that the amount of dibutyltin dilaurate is 1 part.
[0060] Example 7
[0061] The rest is the same as in Example 1, except that the catalyst is dibutyltin diacetate.
[0062] Example 8
[0063] Everything else is the same as in Example 1, except that the catalyst is... Titanate chelates.
[0064] Example 9
[0065] The rest is the same as in Example 1, except that the catalyst is 2-ethylhexyloxytitanate.
[0066] Comparative Example 1
[0067] The rest is the same as in Example 1, except that 100 parts of α,ω-dihydroxypolydimethylsiloxane H48V20000 are used.
[0068] Comparative Example 2
[0069] The rest is the same as in Example 1, except that no second crosslinking agent is added, and the amount of the first crosslinking agent, vinyltrimethoxysilane, is 5 parts.
[0070] The sealants prepared in the above embodiments and comparative examples were subjected to the following performance tests:
[0071] Tensile properties: Tested according to GB / T 528-2009 (Type 2 specimen).
[0072] Surface drying time: Tested according to GB / T 13477.5-2003.
[0073] Curing speed: Tested in accordance with GB / T 29595-2013.
[0074] Anti-fog effect: 1) Apply about 50g of the above sealant to a petri dish and spread it evenly; 2) Place the car light with the anti-fog coating on the petri dish, with the anti-fog coating side facing the sealant side, and seal them together in a self-sealing bag; 3) After the sealant has cured for 72 hours, place the petri dish together with the transparent substrate coated with the anti-fog coating in an 80℃ environment for 24 hours, and then cool it to 23±2℃; 4) Place the treated transparent substrate above 80℃ warm water, with the substrate 200mm above the water surface, and observe for 30 seconds. Observe whether the part of the transparent substrate coated with the anti-fog coating remains transparent or becomes foggy. Score according to subjective judgment: 5 points for complete transparency, the lower the transparency, the lower the score, and 0 points for complete fogging.
[0075] Test method for shelf life: Place the sample at 23±2℃ and 50±5%RH, and store it away from light. Measure the tensile strength of the sample every half month. When the tensile strength remains above 60% of the original index, it is determined to be within the shelf life; otherwise, it is determined to be past the shelf life.
[0076] Table 1
[0077] project Surface drying time / min Curing speed (mm / 24h) Tensile strength / MPa Anti-fog effect / score Shelf life / month Example 1 15 3.5 3.28 5 13.0 Example 2 17 3.4 3.14 5 13.0 Example 3 19 3.2 3.03 5 13.5 Example 4 28 2.1 2.95 5 15.0 Example 5 12 3.8 3.35 4 11.0 Example 6 22 3.1 3.27 5 13.5 Example 7 16 3.4 3.20 5 13.0 Example 8 25 2.6 3.18 5 14.5 Example 9 26 2.5 3.16 4 14.5 Comparative Example 1 16 3.2 2.99 2 13.0 Comparative Example 2 24 2.4 2.56 3 15.0
[0078] As shown in Table 1, the second crosslinking agent prepared in this invention can significantly reduce the volatile content of the sealant and prevent the headlights from fogging, while also achieving a faster curing speed and excellent shelf life. The examples and comparative examples show that the second crosslinking agent has a synergistic effect with organotin compounds to improve the room temperature curing speed. This is presumably because the tertiary amine on the second crosslinking agent promotes the hydrolysis of the most easily hydrolyzed ester groups on the tin atoms, thereby accelerating subsequent reactions.
[0079] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.
Claims
1. A silicone sealant composition for anti-fog vehicle lights, characterized in that, The product comprises the following components: α,ω-dihydroxy polydimethylsiloxane, a first crosslinking agent, a second crosslinking agent, a catalyst, a filler, a coupling agent, and a plasticizer. The first crosslinking agent has 3 alkoxy functional groups, and the second crosslinking agent has ≥4 alkoxy functional groups. The D3-D10 content of the α,ω-dihydroxy polydimethylsiloxane is 0.01-0.05 wt%. The second crosslinking agent is a polyalkoxysilane prepared by reacting a tertiary amine polyol with an isocyanate-based silane coupling agent. The molar ratio of alcohol hydroxyl groups to isocyanate groups in the tertiary amine polyol and isocyanate-based silane coupling agent is 1:1.10-1.
16.
2. The silicone sealant composition for anti-fog vehicle lights according to claim 1, characterized in that, It includes the following components in parts by weight: 100 parts α,ω-dihydroxypolydimethylsiloxane, 1-3 parts first crosslinking agent, 1-2 parts second crosslinking agent, 1-3 parts catalyst, 50-150 parts filler, 1-3 parts coupling agent, and 3-10 parts plasticizer.
3. The silicone sealant composition for anti-fog vehicle lights according to claim 1, characterized in that, The first crosslinking agent is selected from one or a combination of two or more of methyltrimethoxysilane, vinyltrimethoxysilane, propyltrimethoxysilane, octyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, and phenyltrimethoxysilane.
4. The silicone sealant composition for anti-fog vehicle lights according to claim 1, characterized in that, The catalyst is selected from one or a combination of two of organotin compounds, titanates, titanate complexes, and platinum catalysts.
5. The silicone sealant composition for anti-fog vehicle lights according to claim 4, characterized in that, The catalyst is an organotin compound.
6. The silicone sealant composition for anti-fog vehicle lights according to claim 5, characterized in that, The catalyst is one or a combination of two of dibutyltin dilaurate, dibutyltin diacetate, and stannous octoate.
7. The silicone sealant composition for anti-fog vehicle lights according to claim 1, characterized in that, The viscosity of the α,ω-dihydroxypolydimethylsiloxane is 20,000-100,000 cps; the filler is selected from one or a combination of two of calcium carbonate and precipitated silica; the average particle size of the filler is 0.1-100 μm, and the specific surface area of the precipitated silica is 50-400 m². 2 / g; the coupling agent is selected from one or a combination of two of cyanoalkoxysilane and aminoalkoxysilane; the plasticizer has an apparent viscosity of 35-350 mPa·s at 25°C and is selected from one or a combination of two or more of alkyl aromatic compounds, dimethyl silicone oil, alkanes, α,ω-dimethoxy polydimethylsiloxane, and MDT-type silicone oil.
8. The silicone sealant composition for anti-fog vehicle lights according to claim 1, characterized in that, The tertiary amine polyol is selected from one or a combination of two or more of the following: triethanolamine, 2-(dimethylamino)-2-(hydroxymethyl)-1,3-propanediol, 1-dimethylamino-2-(hydroxymethyl)propane-1,3-diol, N,N,N',N'-tetrahydroxyethylethylenediamine, N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine, hydroxyethyl diisopropanolamine, and dihydroxyethyl tert-butanolamine; the isocyanate-based silane coupling agent is selected from one or a combination of two or more of the following: (3-propyl isocyanate)triethoxysilane, methyl isocyanatetriethoxysilane, 3-propyl isocyanatetrimethoxysilane, and propyl methyl isocyanatediethoxysilane.
9. The silicone sealant composition for anti-fog vehicle lights according to claim 1, characterized in that, The second crosslinking agent is prepared by a method comprising the following steps: Under dry inert gas conditions, tertiary amine polyol, isocyanate-based silane coupling agent, and catalyst are mixed evenly, heated and kept at a constant temperature, and the reaction is carried out under stirring. After the reaction is completed, the second crosslinking agent is obtained by vacuum distillation.
10. A method for preparing the silicone sealant composition for anti-fog vehicle lights according to any one of claims 1-9, comprising the following steps: 1) Mix α,ω-dihydroxypolydimethylsiloxane, filler, and plasticizer evenly; 2) Add the first crosslinking agent and the second crosslinking agent to the mixture from step 1), and mix thoroughly; 3) Add the catalyst and coupling agent to the mixture in step 2), mix well, cool, discharge, and package.