Preparation process of silicone sealant
By combining modified UV absorbers and secondary cross-linkers, the dispersion problem of UV absorbers in silicone sealants is solved, the anti-UV and anti-mildew properties are improved, and the overall performance of the sealant is improved.
Patent Information
- Application Number
- CN202510781901.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-12
- Publication Date
- 2025-09-12
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
The dispersion effect of ultraviolet absorbers in silicone sealants during the mixing process is poor, which makes it difficult to disperse evenly in the high-viscosity matrix, affecting the ultraviolet absorption effect. At the same time, it is easy to absorb moisture in a high-humidity environment, promoting mold growth and affecting the sealing integrity.
By modifying the UV absorber UV-P, a brominated UV absorber was generated by bromination reaction using N-bromosuccinimide and azobisisobutyronitrile, which was then converted into a formylated UV absorber through a Sommelet reaction. Bis(3-trimethoxysilylpropyl)amine was combined as a secondary cross-linker to improve its compatibility and stability in silicone sealant. Nano-calcium carbonate was used to improve the dispersion effect and inhibit the formation of micropores.
It improves the dispersion effect and stability of ultraviolet absorbers in silicone sealants, enhances the anti-ultraviolet performance and mildew resistance, reduces the formation of microporous structure, and improves the waterproof and mildew resistance of the sealant.
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of adhesives, and in particular, relates to a process for preparing a silicone sealant, and more particularly, to a process for preparing a two-component silicone sealant. Background Art
[0002] Silicone sealants, a key component of organosilicon polymer systems, have been industrialized since the mid-twentieth century. Their exceptional weather resistance, wide temperature stability (-60°C to 200°C), excellent elastic recovery, and adhesion to a variety of substrates have made them a core sealing material in areas such as building curtain walls, door and window caulking, automotive manufacturing, and electronic packaging. Silicone sealants typically have an extremely high initial viscosity. While this high viscosity improves sag resistance and thixotropy during construction, it also poses a significant challenge to the uniform dispersion of solid admixtures. This is especially true when adding functional solid particles such as UV absorbers. The high viscosity of the matrix significantly weakens the diffusion kinetics, leading to a sharp decrease in mixing efficiency. Under conventional mechanical stirring, solid particles struggle to overcome viscous resistance and achieve Brownian motion, easily agglomerating or settling and stratifying, severely impacting the effectiveness of the UV absorber.
[0003] Although silicone sealant has inherent hydrophobicity and a low water vapor permeability, its surface microporous structure can still absorb and retain moisture in the continuous high humidity environment during the plum rain season in the south, providing a breeding microenvironment for mold spores. This not only affects the appearance, but the deep penetration of mycelium is more likely to accelerate the hydrolysis of colloidal chain segments and weaken the sealing integrity. To address the above technical defects, the present invention provides a silicone sealant preparation process. Summary of the Invention
[0004] The object of the present invention is to provide a process for preparing silicone sealant to solve the problems mentioned in the above background technology.
[0005] The purpose of the present invention can be achieved through the following technical solutions:
[0006] A process for preparing silicone sealant comprises the following steps:
[0007] The first step is to mix the ultraviolet absorber UV-P, N-bromosuccinimide, azobisisobutyronitrile, and chloroform in a three-necked flask equipped with a condenser, a thermometer, and a magnetic stirrer, and react at a temperature of 60°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the remaining solid is washed with deionized water and then dried to obtain a brominated ultraviolet absorber;
[0008] The second step is to mix the brominated ultraviolet absorber, hexamethylenetetramine and chloroform in a three-necked flask equipped with a condenser, a thermometer and a magnetic stirrer, and react at a temperature of 50-60°C for 6-8h, then cool the three-necked flask with an ice-water bath to precipitate crystals, and after vacuum filtration, mix the obtained solid with glacial acetic acid solution in a three-necked flask equipped with a condenser, a thermometer and a magnetic stirrer, and react at a temperature of 90-100°C for 3-4h. After the reaction is completed, extract with dichloromethane, separate the organic phase with a separatory funnel, wash the organic phase with a saturated sodium bicarbonate solution and saturated salt water in sequence, dry it, and then evaporate to remove the solvent to obtain a formylated ultraviolet absorber;
[0009] Step 3: Mix 107 silicone rubber, dimethyl silicone oil, and liquid mildew preventer and add them to a planetary mixer. Stir and disperse them at a stirring rate of 100-150 rpm and a dispersion rate of 1600-2000 rpm for 40-60 minutes. Then, add nano-calcium carbonate to the system. Keep stirring at the same speed for 3-4 hours. After vacuum degassing, fill the mixture into a packaging container, and fill it with dry nitrogen to seal it to obtain component A.
[0010] Step 4: Mix the primary cross-linking agent, the secondary cross-linking agent, the catalyst, the dimethyl silicone oil, and the formylated ultraviolet absorber and add them to a planetary mixer. Stir and disperse them for 3 to 4 hours under nitrogen protection at a stirring rate of 100 to 150 rpm and a dispersion rate of 1000 to 1400 rpm. After vacuum degassing, fill the mixture into a packaging container, fill it with dry nitrogen and seal it to obtain component B.
[0011] Step 5: Mix component A and component B in a mass ratio of 86-92:8-14 to obtain the silicone sealant.
[0012] Furthermore, the ultraviolet absorber UV-P is 2-(2-hydroxy-5-benzyl)benzotriazole.
[0013] Furthermore, the glacial acetic acid solution is a glacial acetic acid aqueous solution with a mass fraction of 40 to 60%.
[0014] Furthermore, the viscosity specification of the 107 silicone rubber is 80,000 to 120,000 mPa·s.
[0015] Furthermore, the liquid mildew inhibitor is one of JKCIDE-ST3200 and JKCIDE-ST200.
[0016] Furthermore, the main cross-linking agent is methyltrimethoxysilane.
[0017] Furthermore, the secondary cross-linking agent is bis(3-trimethoxysilylpropyl)amine.
[0018] Furthermore, the catalyst is one of dibutyltin dilaurate, dimethyltin diceneodecanoate, and dibutyltin dioctoate.
[0019] Furthermore, the mass ratio of the ultraviolet absorber UV-P, N-bromosuccinimide, azobisisobutyronitrile and chloroform used in the first step is 1.75-2.25:1.8-2.4:0.2-0.3:30-40.
[0020] Furthermore, the mass ratio of the brominated ultraviolet absorber, hexamine, chloroform and glacial acetic acid solution used in the second step is 1.8-2.2:1.1-1.5:30-40:20-30.
[0021] Furthermore, the mass ratio of 107 silicone rubber, dimethyl silicone oil, mildew inhibitor and nano calcium carbonate used in the third step is 90-100:15-25:1.2-1.8:20-60.
[0022] Furthermore, the mass ratio of the main cross-linking agent, the secondary cross-linking agent, the catalyst, the dimethyl silicone oil and the formylated ultraviolet absorber used in the fourth step is 8-12: 2-4: 0.6-1.2: 4-8: 0.3-0.5.
[0023] Beneficial effects of the present invention:
[0024] 1) The present invention modifies the ultraviolet absorber UV-P, uses N-bromosuccinimide as a bromination reagent and azobisisobutyronitrile as an initiator, and undergoes a bromination reaction at the benzyl position of UV-P to obtain a brominated ultraviolet absorber. Then, the bromomethyl structure of the brominated ultraviolet absorber is converted into a formyl group through a Sommelet reaction to obtain a formylated ultraviolet absorber. The formylated ultraviolet absorber can react with the amino group in the secondary cross-linker bis(3-trimethoxysilylpropyl)amine at room temperature to be connected to the siloxane molecular chain, thereby effectively improving the compatibility and stability of the ultraviolet absorber in the silicone sealant, and improving the dispersion effect of the ultraviolet absorber in the silicone sealant, thereby having better ultraviolet resistance.
[0025] 2) The present invention uses bis(3-trimethoxysilylpropyl)amine as a secondary cross-linking agent for silicone sealant. Bis(3-trimethoxysilylpropyl)amine has six siloxane structures, which can effectively increase the cross-linking density of silicone sealant, reduce the micropores on the surface of silicone sealant, reduce the physical migration of liquid mildew inhibitors, and inhibit the adsorption of surface organic matter, thereby effectively improving the mildew-proof effect of silicone sealant. DETAILED DESCRIPTION
[0026] It should be understood that the expression "one or more of" includes individually each of the items recited after the expression and various combinations of two or more of the recited items, unless otherwise apparent from the context and usage. The expression "and / or" in conjunction with three or more recited items should be understood to have the same meaning, unless otherwise apparent from the context.
[0027] The terms "comprising", "having" or "containing", including their grammatical synonyms, should generally be understood as open and non-restrictive, e.g., not excluding other unrecited elements or steps, unless otherwise specifically stated or understood from the context.
[0028] It should be understood that the order of steps or the order in which certain actions are performed are not important as long as the present invention remains operable. Additionally, two or more steps or actions may be performed simultaneously.
[0029] The use of any and all examples or exemplary language, such as "such as" or "including," herein is intended merely to better illustrate the invention and does not limit the scope of the invention unless otherwise claimed. No language in this specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
[0030] Example 1
[0031] A process for preparing silicone sealant comprises the following steps:
[0032] The first step is to mix 1.75 parts of ultraviolet absorber UV-P, 1.8 parts of N-bromosuccinimide, 0.2 parts of azobisisobutyronitrile, and 30 parts of chloroform in a three-necked flask equipped with a condenser, a thermometer, and a magnetic stirrer, and react at a temperature of 60°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the remaining solid is washed with deionized water and then dried to obtain a brominated ultraviolet absorber;
[0033] The second step, by weight, 1.8 parts of brominated ultraviolet absorber, 1.1 parts of hexamethylenetetramine, and 30 parts of chloroform were mixed in a three-necked flask equipped with a condenser, a thermometer, and a magnetic stirrer, and the reaction was carried out at a temperature of 50 ° C for 8 hours. After that, the three-necked flask was cooled in an ice-water bath to precipitate crystals. After vacuum filtration, the obtained solid and 20 parts of a 60% by weight aqueous glacial acetic acid solution were mixed together in a three-necked flask equipped with a condenser, a thermometer, and a magnetic stirrer, and the reaction was carried out at a temperature of 90 ° C for 4 hours. After the reaction, the organic phase was extracted with dichloromethane, and the organic phase was separated by a separatory funnel. The organic phase was washed with a saturated sodium bicarbonate solution and a saturated brine, dried, and then evaporated to remove the solvent to obtain a formylated ultraviolet absorber;
[0034] Step 3: Mix 90 parts of silicone rubber with a viscosity of 120,000 mPa·s107, 15 parts of dimethyl silicone oil, and 1.2 parts of JKCIDE-ST3200 mildew inhibitor, by mass, and add them to a planetary mixer. Stir and disperse them at a stirring rate of 100 rpm and a dispersion rate of 1,600 rpm for 60 minutes. Then, add 20 parts of nano-calcium carbonate to the system, keep the speed constant and continue stirring for 3 hours, vacuum degas the mixture, fill it into a packaging container, and fill it with dry nitrogen to seal it to obtain component A.
[0035] Step 4: 8 parts of methyltrimethoxysilane, 2 parts of bis(3-trimethoxysilylpropyl)amine, 0.6 parts of dibutyltin dilaurate, 4 parts of dimethyl silicone oil, and 0.3 parts of formylated ultraviolet absorber were mixed by mass and added to a planetary mixer. The mixture was stirred and dispersed for 3 hours under nitrogen protection, a stirring rate of 100 rpm, and a dispersion rate of 1000 rpm. After vacuum degassing, the mixture was filled into a packaging container and sealed with dry nitrogen to obtain component B.
[0036] Step 5: Component A and component B are mixed in a mass ratio of 86:14 to obtain the silicone sealant.
[0037] Example 2
[0038] A process for preparing silicone sealant comprises the following steps:
[0039] The first step is to mix 2 parts of ultraviolet absorber UV-P, 2.1 parts of N-bromosuccinimide, 0.25 parts of azobisisobutyronitrile, and 35 parts of chloroform in a three-necked flask equipped with a condenser, a thermometer, and a magnetic stirrer, and react at a temperature of 60°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the remaining solid is washed with deionized water and then dried to obtain a brominated ultraviolet absorber;
[0040] The second step, by weight, 2 parts of brominated ultraviolet absorber, 1.3 parts of hexamethylenetetramine, and 35 parts of chloroform were mixed in a three-necked flask equipped with a condenser, a thermometer, and a magnetic stirrer, and the mixture was reacted at a temperature of 55 ° C for 7 hours. After that, the three-necked flask was cooled in an ice-water bath to precipitate crystals. After vacuum filtration, the obtained solid was mixed with 25 parts of a 50% by weight aqueous glacial acetic acid solution in a three-necked flask equipped with a condenser, a thermometer, and a magnetic stirrer, and the mixture was reacted at a temperature of 95 ° C for 3.5 hours. After the reaction, the mixture was extracted with dichloromethane, and the organic phase was separated with a separatory funnel. The organic phase was washed with a saturated sodium bicarbonate solution and a saturated brine in sequence and dried, and then the solvent was removed by rotary evaporation to obtain a formylated ultraviolet absorber;
[0041] Step 3: Mix 95 parts of silicone rubber with a viscosity of 100,000 mPa·s107, 20 parts of dimethyl silicone oil, and 1.5 parts of JKCIDE-ST200 mildew inhibitor, by mass, and add them to a planetary mixer. Stir and disperse them at a stirring rate of 125 rpm and a dispersion rate of 1800 rpm for 50 minutes. Then, add 40 parts of nano-calcium carbonate to the system, keep the speed constant and continue stirring for 3.5 hours, vacuum degas the mixture, fill it into a packaging container, and fill it with dry nitrogen to seal it to obtain component A.
[0042] Step 4: 10 parts of methyltrimethoxysilane, 3 parts of bis(3-trimethoxysilylpropyl)amine, 0.9 parts of dimethyltin dineodecanoate, 6 parts of dimethyl silicone oil, and 0.4 parts of formylated ultraviolet absorber were mixed by mass and added to a planetary mixer. After stirring and dispersing for 3.5 hours under nitrogen protection, a stirring rate of 125 rpm and a dispersion rate of 1200 rpm, the mixture was vacuum degassed and filled into a packaging container, which was then sealed with dry nitrogen to obtain component B.
[0043] Step 5: Mix component A and component B in a mass ratio of 89:11 to obtain the silicone sealant.
[0044] Example 3
[0045] A process for preparing silicone sealant comprises the following steps:
[0046] The first step is to mix 2.25 parts of ultraviolet absorber UV-P, 2.4 parts of N-bromosuccinimide, 0.3 parts of azobisisobutyronitrile, and 40 parts of chloroform in a three-necked flask equipped with a condenser, a thermometer, and a magnetic stirrer, and react at a temperature of 60°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the remaining solid is washed with deionized water and then dried to obtain a brominated ultraviolet absorber;
[0047] The second step, by weight, 2.2 parts of brominated ultraviolet absorber, 1.5 parts of hexamethylenetetramine, and 40 parts of chloroform were mixed in a three-necked flask equipped with a condenser, a thermometer, and a magnetic stirrer, and the mixture was reacted at a temperature of 60 ° C for 6 hours. After that, the three-necked flask was cooled in an ice-water bath to precipitate crystals. After vacuum filtration, the obtained solid and 30 parts of a 40% by weight aqueous glacial acetic acid solution were mixed together in a three-necked flask equipped with a condenser, a thermometer, and a magnetic stirrer. The mixture was reacted at a temperature of 100 ° C for 3 hours. After the reaction was completed, the mixture was extracted with dichloromethane, and the organic phase was separated with a separatory funnel. The organic phase was washed with a saturated sodium bicarbonate solution and a saturated brine, dried, and then evaporated to remove the solvent to obtain a formylated ultraviolet absorber;
[0048] Step 3: 100 parts of silicone rubber with a viscosity of 80,000 mPa·s107, 25 parts of dimethyl silicone oil, and 1.8 parts of JKCIDE-ST200 mildew inhibitor were mixed by weight and added to a planetary mixer. The mixture was stirred and dispersed at a stirring rate of 150 rpm and a dispersion rate of 2000 rpm for 40 minutes. Then, 60 parts of nano-calcium carbonate were added to the system. The stirring speed was kept constant and the stirring was continued for 4 hours. After vacuum degassing, the mixture was filled into a packaging container and sealed with dry nitrogen to obtain component A.
[0049] Step 4: 12 parts of methyltrimethoxysilane, 4 parts of bis(3-trimethoxysilylpropyl)amine, 1.2 parts of dibutyltin dioctoate, 8 parts of dimethyl silicone oil, and 0.5 parts of formylated ultraviolet absorber were mixed by mass and added to a planetary mixer. After stirring and dispersing for 3 hours under nitrogen protection, a stirring rate of 150 rpm and a dispersion rate of 1400 rpm, the mixture was vacuum degassed and filled into a packaging container, which was then sealed with dry nitrogen to obtain component B.
[0050] Step 5: Mix component A and component B in a mass ratio of 92:8 to obtain the silicone sealant.
[0051] Comparative Example 1
[0052] The secondary cross-linking agent bis(3-trimethoxysilylpropyl)amine in Example 3 was replaced with an equal mass of the primary cross-linking agent methyltrimethoxysilane, and the ultraviolet absorber UV-P was not modified.
[0053] The first step is to mix 100 parts of silicone rubber with a viscosity specification of 80,000 mPa·s107, 25 parts of dimethyl silicone oil, and 1.8 parts of JKCIDE-ST200 mildew inhibitor, by mass, and add them to a planetary mixer. Stir and disperse them at a stirring rate of 150 rpm and a dispersion rate of 2000 rpm for 40 minutes. Then, 60 parts of nano-calcium carbonate are added to the system. After stirring for 4 hours at a constant speed, the mixture is vacuum degassed and filled into a packaging container. The container is then sealed with dry nitrogen to obtain component A.
[0054] Step 2: 16 parts of methyltrimethoxysilane, 1.2 parts of dibutyltin dioctoate, 8 parts of dimethyl silicone oil, and 0.5 parts of ultraviolet absorber UV-P were mixed by mass and added to a planetary mixer. The mixture was stirred and dispersed for 3 hours under nitrogen protection at a stirring rate of 150 rpm and a dispersion rate of 1400 rpm. After vacuum degassing, the mixture was filled into a packaging container and sealed with dry nitrogen to obtain component B.
[0055] In the third step, component A and component B are mixed in a mass ratio of 92:8 to obtain the silicone sealant.
[0056] Experimental Example 1
[0057] The silicone sealants in Examples 1 to 3 and Comparative Example 1 were respectively subjected to UV resistance test and mildew resistance test. The test results are shown in Table 1.
[0058] UV resistance test: Refer to the national standard GB / T14683-2017 "Silicone and modified silicone building sealants" to test and record the tensile strength of each component silicone sealant. Then, all silicone sealants are added to the UV aging test chamber and UV aged for 168 hours under 1000W mercury lamp conditions. The tensile strength of each component silicone sealant after aging is tested and recorded, and the tensile strength loss rate is calculated. The lower the loss rate, the better the UV resistance.
[0059] Anti-mildew performance test: Performance test is carried out in accordance with the standard JC / T885-2001 "Anti-mildew sealant for construction".
[0060] Table 1
[0061] project Initial tensile strength Tensile strength after aging Tensile strength loss rate Mildew resistance level Example 1 2.32MPa 1.91 17.67% 0 Example 2 2.47MPa 2.04 17.41% 0 Example 3 2.38MPa 1.99 16.39% 0 Comparative Example 1 2.37MPa 1.83 22.78% 1
[0062] As can be seen from Table 1, the silicone sealants prepared by the preparation methods in Examples 1 to 3 of the present invention have good anti-mildew and anti-ultraviolet properties, and can be widely used in the field of building exterior walls.
[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A process for preparing silicone sealant, characterized in that: The following steps are involved: UV rays Absorbent modification: UV absorber UV-P, N-bromosuccinimide, and azobisisobutyronitrile are mixed and subjected to a halogenation reaction to obtain a brominated UV absorber. Subsequently, the brominated UV absorber, hexamethylenetetramine, and glacial acetic acid solution are mixed and subjected to a Sommelet reaction to obtain a formylated UV absorber. Preparation process of silicone sealant: 107 silicone rubber, dimethyl silicone oil, liquid mildew inhibitor, and nano-calcium carbonate are mixed and stirred and dispersed to obtain component A; a main cross-linking agent, a secondary cross-linking agent, a catalyst, dimethyl silicone oil, and a formylated ultraviolet absorber are mixed and stirred and dispersed to obtain component B; then components A and B are mixed to obtain the silicone sealant.
2. A process for preparing a silicone sealant according to claim 1, characterized in that The glacial acetic acid solution is a glacial acetic acid aqueous solution with a mass fraction of 40 to 60%.
3. A process for preparing silicone sealant according to claim 1, characterized in that: The viscosity specification of 107 silicone rubber is 80,000 to 120,000 mPa·s, and it is one of the liquid mildew inhibitors JKCIDE-ST3200 and JKCIDE-ST200.
4. A process for preparing silicone sealant according to claim 1, characterized in that: The main cross-linking agent is methyltrimethoxysilane, and the secondary cross-linking agent is bis(3-trimethoxysilylpropyl)amine.
5. The process for preparing a silicone sealant according to claim 1, wherein: The catalyst is one of dibutyltin dilaurate, dimethyltin diceneodecanoate and dibutyltin dioctoate.
6. The process for preparing a silicone sealant according to claim 1, wherein: The mass ratio of the ultraviolet absorber UV-P, N-bromosuccinimide and azobisisobutyronitrile is 1.75-2.25:1.8-2.4:0.2-0.
3.
7. The process for preparing a silicone sealant according to claim 1, characterized in that: The mass ratio of the brominated ultraviolet absorber, hexamethylenetetramine and glacial acetic acid solution is 1.8-2.2:1.1-1.5:20-30.
8. The process for preparing silicone sealant according to claim 1, characterized in that: The mass ratio of 107 silicone rubber, dimethyl silicone oil, mildew inhibitor and nano calcium carbonate in component A is 90-100:15-25:1.2-1.8:20-60.
9. The process for preparing silicone sealant according to claim 1, characterized in that: The mass ratio of the main cross-linking agent, the secondary cross-linking agent, the catalyst, the dimethyl silicone oil and the formylated ultraviolet absorber in component B is 8-12:2-4:0.6-1.2:4-8:0.3-0.
5.
10. The process for preparing silicone sealant according to claim 1, characterized in that: The stirring and dispersing conditions of component A are as follows: 107 silicone rubber, dimethyl silicone oil and liquid mildew inhibitor are mixed and stirred and dispersed at a stirring rate of 100-150 rpm and a dispersion rate of 1600-2000 rpm for 40-60 minutes, and then nano calcium carbonate is added to the system and stirring is continued for 3-4 hours while keeping the speed unchanged; the stirring and dispersing conditions of component B are as follows: stirring and dispersing for 3-4 hours under nitrogen protection, a stirring rate of 100-150 rpm and a dispersion rate of 1000-1400 rpm.