High-strength, optical grade transparent dealcoholized silicone sealant and preparation method thereof

Abstract

The application discloses a high-strength, optical-grade transparent dealcoholized silicone sealant and a preparation method thereof. The dealcoholized silicone sealant comprises the following raw materials in parts by mass: 100 parts of vinyl-terminated polydimethylsiloxane, 30-50 parts of vinyl MQ silicone resin, 12-15 parts of single-end hydrogen-containing trimethoxyl polydimethylsiloxane, 0.06-0.18 parts of platinum catalyst, 5-10 parts of dimethyl silicone oil, 3-10 parts of crosslinking agent, 2-5 parts of coupling agent and 0.5-1.5 parts of organic tin catalyst. The dealcoholized silicone sealant prepared by the application has excellent mechanical properties and optical-grade light transmittance and is cured at normal temperature.

Description

Technical Field

[0001] This invention relates to the field of sealants, and in particular to a high-strength, optically transparent de-alcoholized silicone sealant and its preparation method. Background Technology

[0002] In existing technologies, de-alcoholized silicone sealants are typically made from hydroxyl-terminated polydimethylsiloxane or alkoxy-terminated polydimethylsiloxane as the base adhesive, with the addition of appropriate crosslinking agents and catalysts. To improve the mechanical properties of silicone sealants, reinforcing fillers such as calcium carbonate, silica, and organomontmorillonite are also added.

[0003] For example, Chinese patent CN107118736A discloses a dealcohol-type silicone sealant composition, including alkoxy-terminated polydimethylsiloxane, silica, organotin catalyst, plasticizer, dehydrating agent, tackifier, and stabilizer. In order to obtain better mechanical properties for the silicone sealant, silica is added, which reduces the transparency of the silicone sealant, preventing it from achieving optical-grade transparency and making it difficult to apply to optical equipment.

[0004] For example, Chinese patent CN104945914A discloses an optical-grade transparent liquid silicone rubber composition, comprising vinyl-terminated polydimethylsiloxane, vinyl MQ silicone resin, methyl hydrogen MQ silicone resin, hydrogen-containing silicone oil, inhibitor, and platinum catalyst. This liquid silicone rubber has advantages such as high transparency and high resilience, but it lacks adhesive properties and cannot be cured at room temperature.

[0005] In view of this, the present invention proposes a high-strength, optically transparent de-alcoholized silicone sealant and its preparation method to solve the above problems. Summary of the Invention

[0006] In order to overcome the shortcomings of the above-mentioned technologies, the present invention provides a high-strength, optically transparent de-alcoholized silicone sealant that is viscous and can be cured at room temperature, and has excellent mechanical properties after curing.

[0007] To achieve the above objectives, the present invention provides a high-strength, optically transparent de-alcoholized silicone sealant, comprising the following raw materials in parts by weight: 100 parts of vinyl-terminated polydimethylsiloxane, 30-50 parts of vinyl MQ silicone resin, 12-15 parts of single-terminated hydrogen-containing trimethoxy polydimethylsiloxane, 0.06-0.18 parts of platinum catalyst, 5-10 parts of dimethyl silicone oil, 3-10 parts of crosslinking agent, 2-5 parts of coupling agent, and 0.5-1.5 parts of organotin catalyst.

[0008] Preferably, at 25°C, the viscosity of the vinyl-terminated polydimethylsiloxane is 10,000–50,000 mPa·s.

[0009] Preferably, the vinyl MQ silicone resin contains 1.3% to 1.7% vinyl by mass.

[0010] Preferably, the single-terminated hydrogen-containing trimethoxy polydimethylsiloxane is prepared by an addition reaction of hydrogen-containing polydimethylsiloxane and vinyltrimethoxysilane, wherein the molar ratio of Si-H in the hydrogen-containing polydimethylsiloxane to the vinyl group in the vinyltrimethoxysilane is 2:1.

[0011] Preferably, the platinum catalyst is a platinum(O)-divinyltetramethyldisiloxane complex.

[0012] Preferably, the platinum catalyst contains 5000 ppm of platinum.

[0013] Preferably, the crosslinking agent is one or a combination of several of methyltrimethoxysilane, ethyltrimethoxysilane, methyl orthosilicate, methyltriethoxysilane, ethyl orthosilicate, ethyl orthosilicate oligomer, and propyl orthosilicate.

[0014] Preferably, the coupling agent is one or a combination of several of aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminoethylaminopropyltrimethoxysilane, aminoethylaminopropyltriethoxysilane, and diethylaminomethyltriethoxysilane.

[0015] Preferably, the organotin catalyst is one or a combination of several of the following: dibutyltin dilaurate, dibutyltin dioctanoate, dibutyltin diacetate, and chelated tin.

[0016] To achieve the above objectives, the present invention further provides a method for preparing a high-strength, optically transparent, alcohol-free silicone sealant, comprising the following steps:

[0017] Step 1: Add vinyl-terminated polydimethylsiloxane, ethylene MQ silicone resin, and platinum catalyst to a mixer and stir evenly at room temperature; then add single-terminated hydrogen-containing trimethoxy polydimethylsiloxane and stir at room temperature for 5-15 minutes.

[0018] Step 2: Heat the mixture in the mixer to 100-120°C and react for 0.5-2 hours;

[0019] Step 3: After the reaction, cool the mixture in the mixer to below 50°C, then add dimethyl silicone oil and stir for 10-20 minutes. At the same time, evacuate the mixer and circulate nitrogen.

[0020] Step 4: Add the crosslinking agent, coupling agent, and organotin catalyst to the mixer and stir until homogeneous to obtain the organosilicon sealant;

[0021] Step 5: Vacuum the mixer to degas the silicone sealant, and then press and package it.

[0022] Preferably, the preparation steps of the single-ended hydrogen-containing trimethoxy polydimethylsiloxane are as follows: add the single-ended hydrogen-containing polydimethylsiloxane and platinum catalyst into a stirrer and stir evenly, heat to 60-80°C under nitrogen protection, and then slowly add vinyltrimethoxysilane dropwise for 1 hour, and react for 3-6 hours.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] 1. This invention modifies vinyl-terminated polydimethylsiloxane and vinyl MQ silicone resin with a single-terminated hydrogen-containing trimethoxy polydimethylsiloxane, grafting reactive methoxy groups onto the vinyl-terminated polydimethylsiloxane and vinyl MQ silicone resin. This modification, along with the synergistic effect of a crosslinking agent, coupling agent, and organotin catalyst, enables curing at room temperature. Furthermore, during the dealcoholization condensation, crosslinking reactions occur between the components, forming a tight network structure, thereby improving the mechanical properties of the silicone sealant.

[0025] 2. Compared with the alcohol-free silicone sealant in the prior art, the silicone sealant of the present invention adds vinyl MQ silicone resin as a liquid reinforcing filler, which further improves the mechanical strength of the silicone sealant without affecting its transparency, so that the overall transparency of the silicone sealant can reach the optical level. Detailed Implementation

[0026] The following examples further illustrate the features and other related characteristics of the present invention in detail, to facilitate understanding by those skilled in the art:

[0027] An embodiment of the present invention provides a high-strength, optically transparent de-alcoholized silicone sealant, comprising the following raw materials in parts by weight: 100 parts of vinyl-terminated polydimethylsiloxane, 30-50 parts of vinyl MQ silicone resin, 12-15 parts of single-terminated hydrogen-containing trimethoxy polydimethylsiloxane, 0.06-0.18 parts of platinum catalyst, 5-10 parts of dimethyl silicone oil, 3-10 parts of crosslinking agent, 2-5 parts of coupling agent, and 0.5-1.5 parts of organotin catalyst.

[0028] In some embodiments, the viscosity of the vinyl-terminated polydimethylsiloxane at 25°C is 10,000–50,000 mPa·s, indicating strong viscosity.

[0029] In some embodiments, the vinyl MQ silicone resin contains 1.3% to 1.7% vinyl by mass.

[0030] In some embodiments, the single-ended hydrogen-containing trimethoxy polydimethylsiloxane is prepared by an addition reaction of hydrogen-containing polydimethylsiloxane and vinyltrimethoxysilane, wherein the molar ratio of Si-H in the hydrogen-containing polydimethylsiloxane to the vinyl group in the vinyltrimethoxysilane is 2:1, so that the addition reaction of hydrogen-containing polydimethylsiloxane and vinyltrimethoxysilane can generate single-ended hydrogen-containing trimethoxy polydimethylsiloxane as much as possible.

[0031] In some embodiments, the platinum catalyst is used to catalyze the addition reaction of terminal vinyl polydimethylsiloxane, vinyl MQ silicone resin, and single-terminated hydrogen-containing trimethoxy polydimethylsiloxane. The platinum catalyst is a platinum(O)-divinyltetramethyldisiloxane complex, which is well compatible with terminal vinyl polydimethylsiloxane, vinyl MQ silicone resin, and single-terminated hydrogen-containing trimethoxy polydimethylsiloxane.

[0032] In some embodiments, the platinum catalyst contains 5000 ppm of platinum.

[0033] In some embodiments, the crosslinking agent is one or a combination of several of methyltrimethoxysilane, ethyltrimethoxysilane, methyl orthosilicate, methyltriethoxysilane, ethyl orthosilicate, ethyl orthosilicate oligomers, and propyl orthosilicate. Under normal air temperature conditions, silicone sealants can undergo de-alcoholization condensation. The crosslinking agent is used to link the polymer molecules of the silicone sealant after de-alcoholization condensation, thereby improving the mechanical properties of the silicone sealant.

[0034] In some embodiments, the coupling agent is one or a combination of several of aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminoethylaminopropyltrimethoxysilane, aminoethylaminopropyltriethoxysilane, and diethylaminomethyltriethoxysilane. The coupling agent is used to increase the adhesive properties of the silicone sealant and to facilitate curing and crosslinking.

[0035] In some embodiments, the organotin catalyst is one or a combination of several of dibutyltin dilaurate, dibutyltin dioctanoate, dibutyltin diacetate, and chelated tin. The organotin catalyst is used to catalyze the de-alcoholization condensation reaction of methoxy groups with Si-H in organosilicon sealants.

[0036] Embodiments of the present invention also provide a method for preparing a high-strength, optically transparent, alcohol-free silicone sealant, comprising the following steps:

[0037] Step 1: Add 100 parts of vinyl-terminated polydimethylsiloxane, 30-50 parts of ethylene MQ silicone resin, and 0.06-0.18 parts of platinum catalyst to a mixer and stir at room temperature for 10 minutes; then add 12-15 parts of single-terminated hydrogen-containing trimethoxy polydimethylsiloxane and stir at room temperature for 5-15 minutes.

[0038] Step 2: Heat the mixture in the mixer to 100-120℃ and react for 0.5-2 hours. The vinyl groups of vinyl polydimethylsiloxane and vinyl MQ silicone resin undergo an addition reaction with the Si-H group of single-terminated hydrogen-trimethoxy polydimethylsiloxane, which grafts reactive methoxy groups onto the vinyl-terminated polydimethylsiloxane and vinyl MQ silicone resin. The methoxy-grafted polysiloxane and silicone resin can be cured in moisture.

[0039] Step 3: After the reaction, cool the mixture in the mixer to below 50°C, then add 5-10 parts of dimethyl silicone oil and stir for 10-20 minutes. At the same time, evacuate the mixer and circulate nitrogen to degas the mixture after the reaction.

[0040] Step 4: Add 3-10 parts of crosslinking agent, 2-5 parts of coupling agent, and 0.5-1.5 parts of organotin catalyst to a mixer and stir until homogeneous to obtain organosilicon sealant.

[0041] Step 5: Vacuum the mixer to degas the silicone sealant, and then press and package it.

[0042] In some embodiments, the preparation steps of the single-terminated hydrogen-containing trimethoxy polydimethylsiloxane are as follows: Hydrogen-containing polydimethylsiloxane and a platinum catalyst are added to a stirrer and stirred until homogeneous. The mixture is heated to 60–80°C under nitrogen protection, and then vinyltrimethoxysilane is slowly added dropwise over a period of 1 hour. The reaction proceeds for 3–6 hours. The resulting mixture is degassed at -99 kPa for 1–2 hours and cooled to room temperature to obtain the single-terminated hydrogen-containing trimethoxy polydimethylsiloxane.

[0043] Example 1

[0044] A method for preparing a high-strength, optically transparent, alcohol-free silicone sealant, comprising the following steps:

[0045] Step 1: Add 100 parts of vinyl-terminated polydimethylsiloxane (viscosity 10000 mP.s), 30 parts of ethylene MQ silicone resin (vinyl content 1.3%), and 0.06 parts of platinum catalyst to a planetary disperser and stir at room temperature for 10 min. Then add 12 parts of single-terminated hydrogen-containing trimethoxy polydimethylsiloxane and stir at room temperature for 10 min.

[0046] Step 2: Heat the mixture in the planetary disperser to 100-120°C and react for 1 hour.

[0047] Step 3: After the reaction, the mixture in the planetary disperser is cooled to below 50°C, and then 5 parts of dimethyl silicone oil are added and stirred for 15 minutes. At the same time, the planetary disperser is evacuated and circulated with nitrogen twice.

[0048] Step 4: Add 3 parts tetraethyl orthosilicate, 2 parts aminopropyltriethoxysilane, and 0.5 parts dibutyltin dilaurate to a planetary disperser and stir for 5 minutes to obtain the silicone sealant.

[0049] Step 5: Vacuum is drawn inside the planetary disperser to degas the silicone sealant, and finally the material is pressed and packaged.

[0050] Examples 2-4 and Comparative Examples 1-2 were prepared by modifying the raw material formulation according to Table 1 and following the preparation method of Example 1. Specifically, in Comparative Example 2, hydrophobic fumed silica was added after the dimethyl silicone oil was added, and the mixture was stirred until homogeneous.

[0051] Table 1. Formulations of Examples 1-4 and Comparative Examples 1-2

[0052]

[0053] The silicone sealants prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to the following tests.

[0054] 1. The surface drying time of the silicone sealant shall be determined in accordance with GB / T13477.5 standard.

[0055] II. The Shore hardness of the silicone sealant was determined according to GB / T531.1-2008 standard.

[0056] III. Determine the extrusion speed of silicone sealant according to GB / T13477.4.1-2017 standard.

[0057] IV. Determine the tensile strength and elongation at break of the silicone sealant according to GB / T528-2009 standard.

[0058] V. Determine the light transmittance of silicone sealant according to GB / T2410-2008 standard.

[0059] Table 2 Test results of Examples 1-4 and Comparative Examples 1-2

[0060]

[0061] (1) As can be seen from the data in Table 2, the hardness, tensile strength and elongation at break of the silicone sealant in Examples 1 to 4 are better than those in Comparative Example 1. This is because vinyl MQ silicone resin is added to the silicone sealant. The vinyl MQ silicone resin forms a three-dimensional network structure in the silicone sealant, which plays an effective reinforcing role and enhances the mechanical properties of the silicone sealant.

[0062] (2) The light transmittance of the silicone sealants in Examples 1-4 is better than that in Comparative Example 2. This is because hydrophobic fumed silica was added to Comparative Example 2 to improve the mechanical properties of the silicone sealant, which significantly reduced the light transmittance of the silicone sealant. However, Examples 1-4 used vinyl MQ silicone resin silicone sealant, which can ensure that the silicone sealant has good mechanical properties and also has optical-grade light transmittance.

[0063] (3) A comparison of Examples 1 and 2 shows that although vinyl MQ silicone resin can improve the mechanical properties of silicone sealant, the amount of vinyl MQ silicone resin used has different effects on the hardness, tensile strength, and elasticity (elongation at break) of the silicone sealant. In the silicone sealant formulation of this invention, the higher the mass fraction of vinyl MQ silicone resin, the better the hardness and tensile strength, while the elasticity will decrease slightly.

[0064] (4) As can be seen from the comparison of Examples 1 to 4, the more crosslinking agent is used in the silicone sealant, the better the hardness and tensile strength of the silicone sealant, while the elasticity will decrease slightly. This is because the crosslinking agent connects the polymer molecules after the de-alcoholization condensation of the silicone sealant, which can improve the hardness and tensile strength of the silicone sealant.

[0065] (5) The surface drying speed of the silicone sealant in Example 1 was greater than that in Example 2. This is because the increased amount of vinyl MQ silicone resin and single-terminated hydrogen-containing trimethoxy polydimethylsiloxane in the silicone sealant led to a longer de-alcoholization time, which slowed down the curing speed of the silicone sealant. Furthermore, a comparison of Examples 1-4 shows that the surface drying speed of the silicone sealant is also related to the amount of organotin catalyst used; the surface drying speed is positively correlated with the amount of organotin catalyst used.

[0066] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a high-strength, optically transparent, alcohol-free silicone sealant, characterized in that, Includes the following steps: Step 1: Add vinyl-terminated polydimethylsiloxane, vinyl MQ silicone resin, and platinum catalyst to a mixer and stir evenly at room temperature; then add single-terminated hydrogen-containing trimethoxy polydimethylsiloxane and stir at room temperature for 5-15 minutes. Step 2: Heat the mixture in the mixer to 100-120°C and react for 0.5-2 hours; Step 3: After the reaction, cool the mixture in the mixer to below 50°C, then add dimethyl silicone oil and stir for 10-20 minutes. At the same time, evacuate the mixer and circulate nitrogen. Step 4: Add the crosslinking agent, coupling agent, and organotin catalyst to the mixer and stir until homogeneous to obtain the organosilicon sealant; Step 5: Vacuum the mixer to degas the silicone sealant, then press and package it. The de-alcoholized silicone sealant comprises the following raw materials in parts by weight: 100 parts vinyl-terminated polydimethylsiloxane, 30-50 parts vinyl MQ silicone resin, 12-15 parts single-terminated hydrogen-containing trimethoxy polydimethylsiloxane, 0.06-0.18 parts platinum catalyst, 5-10 parts dimethyl silicone oil, 3-10 parts crosslinking agent, 2-5 parts coupling agent, and 0.5-1.5 parts organotin catalyst; The single-terminated hydrogen-containing trimethoxy polydimethylsiloxane is prepared by an addition reaction of hydrogen-containing polydimethylsiloxane and vinyltrimethoxysilane, wherein the molar ratio of Si-H in the hydrogen-containing polydimethylsiloxane to the vinyl group in the vinyltrimethoxysilane is 2:

1.

2. The method for preparing a high-strength, optically transparent, de-alcoholized silicone sealant according to claim 1, characterized in that, At 25°C, the viscosity of the terminal vinyl polydimethylsiloxane is 10,000–50,000 mPa·s.

3. The method for preparing a high-strength, optically transparent, de-alcoholized silicone sealant according to claim 1, characterized in that, The vinyl MQ silicone resin contains 1.3% to 1.7% vinyl by mass.

4. The method for preparing a high-strength, optically transparent, de-alcoholized silicone sealant according to claim 1, characterized in that, The platinum catalyst is a platinum(O)-divinyltetramethyldisiloxane complex; the platinum content in the platinum catalyst is 5000 ppm.

5. The method for preparing a high-strength, optically transparent, de-alcoholized silicone sealant according to claim 1, characterized in that, The crosslinking agent is one or a combination of several of the following: methyltrimethoxysilane, ethyltrimethoxysilane, methyl orthosilicate, methyltriethoxysilane, ethyl orthosilicate, ethyl orthosilicate oligomer, and propyl orthosilicate.

6. The method for preparing a high-strength, optically transparent, de-alcoholized silicone sealant according to claim 1, characterized in that, The coupling agent is one or a combination of several of the following: aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminoethylaminopropyltrimethoxysilane, aminoethylaminopropyltriethoxysilane, and diethylaminomethyltriethoxysilane.

7. The method for preparing a high-strength, optically transparent, de-alcoholized silicone sealant according to claim 1, characterized in that, The organotin catalyst is one or a combination of several of the following: dibutyltin dilaurate, dibutyltin dioctanoate, dibutyltin diacetate, and chelated tin.

8. The method for preparing a high-strength, optically transparent, de-alcoholized silicone sealant according to claim 1, characterized in that, The preparation steps of the single-ended hydrogen-containing trimethoxy polydimethylsiloxane are as follows: add the single-ended hydrogen-containing polydimethylsiloxane and platinum catalyst into a stirrer and stir evenly. Under nitrogen protection, heat to 60-80°C, and then slowly add vinyltrimethoxysilane dropwise for 1 hour. The reaction time is 3-6 hours.

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