A quick-curing antibacterial and mildew-proof silicone sealant and a preparation method thereof

Abstract

The application discloses a kind of quick curing antibacterial mildew-proof silicone sealant and preparation method thereof, the sealant includes alpha, omega-dihydroxy polydimethylsiloxane, methyl silicone oil, filler, crosslinking agent, silane coupling agent, catalyst, zinc pyrithione, carbendazim and shrinkage response microsphere.Shrinkage response microsphere includes borosilicate glass microsphere and flexible coating layer coated on its surface, and flexible coating layer contains oligomeric siloxane segment and hydrolysable condensation alkoxysilane group.Shrinkage response microsphere can adjust the interface state between microsphere and silicone matrix by using shrinkage during sealant curing process, provide transient transport path for moisture migration to the interior of colloid, and improve interface integrity after curing by subsequent hydrolysis condensation of alkoxysilane group in coating layer, thereby improving deep curing capacity while maintaining faster surface drying speed.

Description

Technical Field

[0001] This invention belongs to the field of silicone sealant technology, and relates to a fast-curing antibacterial and mildew-proof silicone sealant and its preparation method. Background Technology

[0002] Silicone sealant, commonly known as glass glue, is a type of material that uses polysiloxane as the main film-forming substance. After cross-linking and curing, it forms an elastic sealant. It has good weather resistance, high and low temperature resistance, elasticity, and bonding and sealing performance, and is widely used in building doors and windows, glass assembly, interior decoration, kitchens, and bathrooms. For applications in humid environments, silicone sealant is usually required to have certain antibacterial and anti-mildew properties to reduce mold growth on its surface.

[0003] Existing single-component room-temperature curing silicone sealants typically rely on moisture in the air for cross-linking and curing. Moisture first contacts the surface of the sealant and then gradually diffuses inward, allowing the sealant to cure from the surface inwards. To shorten surface drying time and improve construction efficiency, current technologies often accelerate the curing reaction by increasing the activity of the cross-linking system and the amount of catalyst. However, when the surface cross-linking reaction is too rapid, a highly cross-linked and dense cured layer easily forms on the sealant surface in a short time. This hinders the continued diffusion of external moisture into the sealant, resulting in insufficient moisture for the internal cross-linking reaction and a slower deep curing rate. This is especially problematic when the sealant layer is thick, the construction joints are deep, or air circulation is poor, leading to a situation where the surface has cured while the interior remains incompletely cured.

[0004] If the diffusion of moisture into the colloid is improved by reducing catalytic activity or slowing down the surface cross-linking reaction, the surface drying time and initial curing time of the sealant will be prolonged, reducing construction efficiency and making it difficult to meet the needs of rapid construction. Therefore, existing silicone sealants have the problem of not being able to achieve both rapid curing and deep curing. How to enable silicone sealants to maintain good deep curing ability while having a relatively fast curing speed is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a fast-curing antibacterial and mildew-resistant silicone sealant and its preparation method, aiming to solve the technical problem that it is difficult to achieve both rapid surface drying and deep curing in single-component silicone sealants, while giving the sealant good antibacterial and mildew-resistant properties.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a fast-curing antibacterial and mildew-resistant silicone sealant, comprising the following raw materials in parts by weight: 100 parts of α,ω-dihydroxypolydimethylsiloxane, 8-10 parts of methyl silicone oil, 55-65 parts of nano-activated calcium carbonate, 4-6 parts of hydrophobic fumed silica, 5.0-5.8 parts of methyltrimethoxysilane, 0.8-1.2 parts of vinyltrimethoxysilane, 0.45-0.65 parts of γ-aminopropyltriethoxysilane, 0.10-0.14 parts of dibutyltin dilaurate, 0.25-0.35 parts of zinc pyridinethione, 0.10-0.18 parts of carbendazim, and 3.0-4.0 parts of shrinkage-responsive microspheres;

[0008] The shrinkage-responsive microspheres comprise borosilicate glass microspheres and a flexible coating layer covering the surface of the borosilicate glass microspheres. The flexible coating layer contains oligomeric siloxane segments and hydrolyzable alkoxysilane groups.

[0009] Preferably, the shrinkage-responsive microspheres are made from raw materials comprising the following parts by weight: 100 parts borosilicate glass microspheres, 2.5-3.5 parts hydroxyl-terminated oligomeric dimethylsiloxane, 0.35-0.50 parts methyltrimethoxysilane, 0.15-0.25 parts vinyltrimethoxysilane, 0.003-0.006 parts dibutyltin dilaurate, and 150-180 parts anhydrous n-heptane.

[0010] Preferably, the preparation steps of the shrinkage-responsive microspheres are as follows: after drying borosilicate glass microspheres, they are coated with a coating solution formed by dissolving hydroxyl-terminated oligomeric dimethylsiloxane, methyltrimethoxysilane, vinyltrimethoxysilane, and dibutyltin dilaurate in anhydrous n-heptane; then the temperature is raised to 55-60°C and reacted under anhydrous conditions for 60-80 minutes to allow partial condensation of the coating components and retention of hydrolyzable alkoxysilane groups; finally, the solvent is removed and the microspheres are dried to obtain the shrinkage-responsive microspheres.

[0011] Preferably, the D50 of the borosilicate glass microspheres is 8-12 μm.

[0012] Preferably, the viscosity of the α,ω-dihydroxy polydimethylsiloxane at 25°C is 50,000-80,000 mPa·s; the viscosity of the methyl silicone oil at 25°C is 100-350 mPa·s; and the viscosity of the hydroxyl-terminated oligomeric dimethylsiloxane at 25°C is 50-100 mPa·s.

[0013] Preferably, the mass ratio of methyltrimethoxysilane to vinyltrimethoxysilane is (4-6.5):1.

[0014] Preferably, the average particle size of the nano-active calcium carbonate is 60-100 nm.

[0015] Preferably, the specific surface area of ​​the hydrophobic fumed silica is 150-250 m² / g.

[0016] Preferably, the mass ratio of zinc pyrithione to carbendazim is (1.5-3):1.

[0017] In a second aspect, the present invention provides a method for preparing a rapid-curing antibacterial and antifungal silicone sealant as described in the first aspect, comprising the following steps:

[0018] S1. Add α,ω-dihydroxy polydimethylsiloxane, methyl silicone oil, nano-activated calcium carbonate and hydrophobic fumed silica to a kneader and knead and dehydrate under vacuum at 110-120℃ until the water content of the mixture is less than 500 ppm, and then cool down to below 40℃.

[0019] S2. Add the shrinkage-responsive microspheres and mix at 100-200 r / min for 20-30 minutes.

[0020] S3. Add methyltrimethoxysilane, vinyltrimethoxysilane and γ-aminopropyltriethoxysilane in sequence, and mix under vacuum for 20-30 minutes;

[0021] S4. Add zinc pyrithione, carbendazim and dibutyltin dilaurate, and mix for 15-20 minutes under vacuum at a temperature not exceeding 35°C to remove air bubbles.

[0022] S5. Fill the container into a moisture-proof and sealed container in a dry nitrogen environment to obtain a fast-curing antibacterial and mildew-proof silicone sealant.

[0023] The beneficial effects of this invention are:

[0024] (1) This invention introduces shrinkage-responsive microspheres into the sealant, utilizing the shrinkage difference between the rigid core of the borosilicate glass microspheres and the silicone matrix during the curing process to regulate the interfacial state between the microspheres and the matrix. After the sealant is extruded, the surface layer first comes into contact with moisture in the air and undergoes hydrolytic condensation crosslinking. As the crosslinking network gradually forms, the silicone matrix experiences a certain degree of curing shrinkage, while the size change of the borosilicate glass microspheres is relatively small, resulting in shrinkage mismatch at the microsphere-matrix interface. The oligomeric siloxane flexible coating layer on the surface of the microspheres can regulate the stress response of the interface, forming a transient interfacial region around the microspheres during the curing process that is conducive to moisture migration. This promotes the further transfer of external moisture into the interior of the sealant, providing moisture for the internal crosslinking reaction and improving the deep curing rate of the sealant. Thus, this invention can improve the deep curing performance of the sealant without significantly prolonging the surface drying time.

[0025] (2) The flexible coating layer of the shrinkage-responsive microspheres contains oligomeric siloxane segments and hydrolyzable alkoxysilane groups. By controlling the degree of condensation reaction during the coating stage, the coating layer retains some active groups that can continue to hydrolyze and condense while maintaining a certain degree of flexibility. In the early stage of curing, the microsphere interface is conducive to the migration of water into the colloid; as water is further transferred into the interior and the sealant curing reaction continues, the alkoxysilane groups retained in the coating layer can gradually undergo hydrolysis and subsequent condensation reactions, and form further interfacial bonds with the surface of the microspheres and the surrounding silicone network. This helps to improve the interfacial integrity between the microspheres and the matrix after curing and reduce the adverse effects of the transient interfacial structure on the final mechanical properties of the sealant.

[0026] (3) The present invention uses zinc pyrithione and carbendazim in combination to give the sealant antibacterial and anti-mildew functions, which helps to reduce the risk of microbial growth and surface mold growth in the sealant in long-term humid environments such as kitchens and bathrooms. Detailed Implementation

[0027] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0028] The following descriptions of some of the raw materials used in the examples and comparative examples are as follows:

[0029] α,ω-Dihydroxypolydimethylsiloxane (107 glue): viscosity at 25℃ is 50000-80000 mPa·s;

[0030] Methyl silicone oil: viscosity at 25℃ is 100-350 mPa·s;

[0031] Hydroxyl-terminated oligomeric dimethylsiloxane (hydroxyl silicone oil): viscosity at 25℃ is 50-100 mPa·s;

[0032] Nano-activated calcium carbonate: average particle size is 60-100 nm;

[0033] Hydrophobic fumed silica: specific surface area of ​​150-250 m² / g, primary particle size of 10-40 nm;

[0034] Borosilicate glass microspheres: D50 is 8-12 μm;

[0035] Except for the raw materials explicitly mentioned above, all other raw materials not specifically mentioned are conventional industrial-grade products that can be easily obtained through commercial channels.

[0036] Example 1

[0037] A fast-curing antibacterial and mildew-resistant silicone sealant comprises the following raw materials in parts by weight: 100 parts of α,ω-dihydroxypolydimethylsiloxane (107 adhesive, viscosity 80000 mPa·s at 25℃), 9 parts of methyl silicone oil (viscosity 200 mPa·s at 25℃), 60 parts of nano-activated calcium carbonate (average particle size 80 nm), 4.5 parts of hydrophobic fumed silica (specific surface area 200 m² / g, native particle size 25 nm), 5.4 parts of methyltrimethoxysilane, 1.0 part of vinyltrimethoxysilane, 0.55 parts of γ-aminopropyltriethoxysilane (KH-550), 0.12 parts of dibutyltin dilaurate, 0.30 parts of zinc pyridinethione, 0.14 parts of carbendazim, and 3.5 parts of shrinkage-responsive microspheres.

[0038] The preparation of shrinkage-responsive microspheres includes the following steps:

[0039] A1. Weigh 100 parts by weight of borosilicate glass microspheres (D50 is 10 μm), place them in a vacuum drying oven, dry them for 3 hours at 110℃ and a vacuum degree below -0.090 MPa, cool them to below 40℃, and seal them for later use under dry nitrogen protection.

[0040] A2. Add 160 parts of anhydrous n-heptane, 3.0 parts of hydroxyl-terminated oligomeric dimethylsiloxane (hydroxyl silicone oil, viscosity 80 mPa·s at 25℃), 0.40 parts of methyltrimethoxysilane, 0.20 parts of vinyltrimethoxysilane, and 0.005 parts of dibutyltin dilaurate to a dry reaction vessel. Stir at 400 r / min for 25 minutes under nitrogen protection to obtain a uniform coating solution.

[0041] A3. The dried borosilicate glass microspheres were slowly added to the coating solution and stirred at 250 r / min and 42℃ for 75 minutes under nitrogen protection. Then the temperature was raised to 58℃ and the reaction was continued for 70 minutes under nitrogen protection to allow partial condensation of the coating component. After the reaction was completed, n-heptane was removed under reduced pressure at 45℃ and -0.090 MPa, followed by vacuum drying at 60℃ for 2 hours to obtain the shrinkage-responsive microspheres.

[0042] The preparation of a fast-curing antibacterial and antifungal silicone sealant includes the following steps:

[0043] S1. Add α,ω-dihydroxypolydimethylsiloxane, methyl silicone oil, nano-activated calcium carbonate and hydrophobic fumed silica to a vacuum kneader and knead and dehydrate at 115℃ and -0.095 MPa for 2.5 hours until the water content of the mixture is less than 500 ppm. Cool down to below 40℃ and introduce dry nitrogen gas.

[0044] S2. Add the shrinkage-responsive microspheres and mix at a low speed of 150 r / min for 25 minutes;

[0045] S3. Add methyltrimethoxysilane, vinyltrimethoxysilane and γ-aminopropyltriethoxysilane in sequence, and mix under vacuum for 25 minutes;

[0046] S4. Add zinc pyrithione, carbendazim and dibutyltin dilaurate, and mix for 18 minutes at a temperature not exceeding 35°C and a vacuum degree of -0.095 MPa to remove air bubbles.

[0047] S5. Fill the container into a moisture-proof and sealed container in a dry nitrogen environment to obtain a fast-curing antibacterial and mildew-proof silicone sealant.

[0048] Example 2

[0049] A fast-curing antibacterial and mildew-resistant silicone sealant comprises the following raw materials in parts by weight: 100 parts of α,ω-dihydroxypolydimethylsiloxane (107 adhesive, viscosity 50000 mPa·s at 25℃), 8 parts of methyl silicone oil (viscosity 100 mPa·s at 25℃), 55 parts of nano-activated calcium carbonate (average particle size 60 nm), 4 parts of hydrophobic fumed silica (specific surface area 150 m² / g, native particle size 40 nm), 5.0 parts of methyltrimethoxysilane, 0.8 parts of vinyltrimethoxysilane, 0.45 parts of γ-aminopropyltriethoxysilane (KH-550), 0.10 parts of dibutyltin dilaurate, 0.25 parts of zinc pyridinethione, 0.10 parts of carbendazim, and 3.0 parts of shrinkage-responsive microspheres.

[0050] The preparation of shrinkage-responsive microspheres includes the following steps:

[0051] A1. Weigh 100 parts by weight of borosilicate glass microspheres (D50 is 8 μm), place them in a vacuum drying oven, dry them for 3 hours at 110℃ and a vacuum degree below -0.090 MPa, cool them to below 40℃, and seal them for later use under dry nitrogen protection.

[0052] A2. Add 150 parts of anhydrous n-heptane, 2.5 parts of hydroxyl-terminated oligomeric dimethylsiloxane (hydroxyl silicone oil, viscosity 50 mPa·s at 25℃), 0.35 parts of methyltrimethoxysilane, 0.15 parts of vinyltrimethoxysilane, and 0.003 parts of dibutyltin dilaurate to a dry reaction vessel. Stir at 300 r / min for 20 minutes under nitrogen protection to obtain a uniform coating solution.

[0053] A3. The dried borosilicate glass microspheres were slowly added to the coating solution and stirred at 200 r / min and 40℃ for 60 minutes under nitrogen protection. Then the temperature was raised to 55℃ and the reaction was continued for 60 minutes under nitrogen protection to allow partial condensation of the coating components. After the reaction was completed, n-heptane was removed under reduced pressure at 40℃ and -0.085 MPa. Then the microspheres were vacuum dried at 60℃ for 2 hours to obtain the shrinkage-responsive microspheres.

[0054] The preparation of a fast-curing antibacterial and antifungal silicone sealant includes the following steps:

[0055] S1. Add α,ω-dihydroxy polydimethylsiloxane, methyl silicone oil, nano-activated calcium carbonate and hydrophobic fumed silica to a vacuum kneader and knead and dehydrate at 110℃ and -0.090 MPa for 2 hours until the water content of the mixture is less than 500 ppm. Cool down to below 40℃ and introduce dry nitrogen.

[0056] S2. Add the shrinkage-responsive microspheres and mix at a low speed of 100 r / min for 20 minutes;

[0057] S3. Add methyltrimethoxysilane, vinyltrimethoxysilane and γ-aminopropyltriethoxysilane in sequence, and mix under vacuum for 20 minutes.

[0058] S4. Add zinc pyrithione, carbendazim and dibutyltin dilaurate, and mix for 15 minutes at a temperature not exceeding 35°C and a vacuum degree of -0.090 MPa to remove air bubbles.

[0059] S5. Fill the container into a moisture-proof and sealed container in a dry nitrogen environment to obtain a fast-curing antibacterial and mildew-proof silicone sealant.

[0060] Example 3

[0061] A fast-curing antibacterial and mildew-resistant silicone sealant comprises the following raw materials in parts by weight: 100 parts of α,ω-dihydroxypolydimethylsiloxane (107 adhesive, viscosity 65000 mPa·s at 25℃), 10 parts of methyl silicone oil (viscosity 350 mPa·s at 25℃), 65 parts of nano-activated calcium carbonate (average particle size 100 nm), 6 parts of hydrophobic fumed silica (specific surface area 250 m² / g, native particle size 10 nm), 5.8 parts of methyltrimethoxysilane, 1.2 parts of vinyltrimethoxysilane, 0.65 parts of γ-aminopropyltriethoxysilane (KH-550), 0.14 parts of dibutyltin dilaurate, 0.35 parts of zinc pyridinethione, 0.18 parts of carbendazim, and 4.0 parts of shrinkage-responsive microspheres.

[0062] The preparation of shrinkage-responsive microspheres includes the following steps:

[0063] A1. Weigh 100 parts by weight of borosilicate glass microspheres (D50 is 12 μm), place them in a vacuum drying oven, dry them for 4 hours at 120℃ and a vacuum degree below -0.090 MPa, cool them to below 40℃, and seal them for later use under dry nitrogen protection.

[0064] A2. Add 180 parts of anhydrous n-heptane, 3.5 parts of hydroxyl-terminated oligomeric dimethylsiloxane (hydroxyl silicone oil, viscosity 100 mPa·s at 25℃), 0.50 parts of methyltrimethoxysilane, 0.25 parts of vinyltrimethoxysilane, and 0.006 parts of dibutyltin dilaurate to a dry reaction vessel. Stir at 500 r / min for 30 minutes under nitrogen protection to obtain a uniform coating solution.

[0065] A3. The dried borosilicate glass microspheres were slowly added to the coating solution and stirred at 300 r / min and 45℃ for 90 minutes under nitrogen protection. Then the temperature was raised to 60℃ and the reaction was continued for 80 minutes under nitrogen protection to allow partial condensation of the coating components. After the reaction was completed, n-heptane was removed under reduced pressure at 50℃ and -0.095 MPa. Then the microspheres were vacuum dried at 60℃ for 2 hours to obtain the shrinkage-responsive microspheres.

[0066] The preparation of a fast-curing antibacterial and antifungal silicone sealant includes the following steps:

[0067] S1. Add α,ω-dihydroxypolydimethylsiloxane, methyl silicone oil, nano-activated calcium carbonate and hydrophobic fumed silica to a vacuum kneader and knead and dehydrate at 120℃ and -0.098 MPa for 3 hours until the water content of the mixture is less than 500 ppm. Cool down to below 40℃ and introduce dry nitrogen gas.

[0068] S2. Add shrinkage-responsive microspheres and mix at a low speed of 200 r / min for 30 minutes.

[0069] S3. Add methyltrimethoxysilane, vinyltrimethoxysilane and γ-aminopropyltriethoxysilane in sequence, and mix under vacuum for 30 minutes;

[0070] S4. Add zinc pyrithione, carbendazim and dibutyltin dilaurate, and mix for 20 minutes at a temperature not exceeding 35°C and a vacuum degree of -0.098 MPa to remove air bubbles;

[0071] S5. Fill the container into a moisture-proof and sealed container in a dry nitrogen environment to obtain a fast-curing antibacterial and mildew-proof silicone sealant.

[0072] Comparative Example 1

[0073] The difference from Example 1 is that shrinkage-responsive microspheres are not added, while the other raw materials, amounts, and preparation processes are the same as in Example 1.

[0074] Comparative Example 2

[0075] The difference from Example 1 is that an equal amount of uncoated borosilicate glass microspheres (D50 of 10 μm) are used instead of shrinkage-responsive microspheres. The borosilicate glass microspheres are dried according to step A1 of Example 1, but without the coating and partial condensation treatment described in steps A2-A3; they are added directly in step S2. The types and amounts of other raw materials and the preparation process are the same as in Example 1.

[0076] Comparative Example 3

[0077] The difference from Example 1 is that methyltrimethoxysilane and vinyltrimethoxysilane are not added in microsphere preparation step A2. The coating solution consists of 160 parts of anhydrous n-heptane, 3.0 parts of hydroxyl-terminated oligomeric dimethylsiloxane (viscosity 80 mPa·s at 25°C), and 0.005 parts of dibutyltin dilaurate. The borosilicate glass microspheres dried in step A1 are added to the above treatment solution and treated under the same stirring, heating, solvent removal, and drying conditions as in step A3 of Example 1. The resulting microspheres are used in step S2. The types and amounts of other raw materials and the sealant preparation process are the same as in Example 1.

[0078] Comparative Example 4

[0079] The difference from Example 1 is that hydroxyl-terminated oligodimethylsiloxane is not added in step A2 of the preparation of shrinkage-responsive microspheres. The coating solution consists of 160 parts of anhydrous n-heptane, 0.40 parts of methyltrimethoxysilane, 0.20 parts of vinyltrimethoxysilane, and 0.005 parts of dibutyltin dilaurate. The other microsphere preparation conditions, raw material types, amounts, and sealant preparation processes are the same as in Example 1.

[0080] Comparative Example 5

[0081] The difference from Example 1 is that in step A3 of preparing the shrinkage-responsive microspheres, the reaction time of 70 minutes at 58°C was changed to 4 hours at 80°C to improve the degree of condensation reaction of the coating layer. The other raw material types, amounts and preparation processes are the same as in Example 1.

[0082] Test case

[0083] (1) Surface drying time

[0084] The test was conducted according to Method A in GB / T 13477.5-2002 "Test Methods for Building Sealing Materials Part 5: Determination of Surface Drying Time", and the time required for the sealant surface to become tacky was recorded.

[0085] (2) Depth of deep curing

[0086] Each silicone sealant to be tested was filled into a polytetrafluoroethylene (PTFE) tank with an inner dimension of 100 mm in length, 20 mm in width, and 15 mm in depth, ensuring the sealant filled the tank and the top surface was smoothed, leaving only the top surface of the sealant layer exposed to air. The prepared specimens were cured at a temperature of (23±2)℃ and a relative humidity of (50±5)%. After curing for 24 h, 48 h, and 72 h, the specimens were cut at least 30 mm from the end, perpendicular to the exposed surface of the sealant layer. After cutting, the uncured sealant that was still flowing or obviously pasty and could not maintain its shape was gently scraped away from the cross-section, leaving the remaining elastic, shape-maintaining, and non-plastic cured sealant layer as the cured area. The vertical distance from the air-exposed surface of the sealant layer to the boundary between the cured and uncured areas was measured using vernier calipers, and this distance was taken as the deep curing depth at the corresponding curing time. For the same cross-section, measurements were taken at no fewer than three locations along the width direction, and the average value was taken as the curing depth of the specimen. For each group of samples, five parallel specimens were set up at each curing time point, and the arithmetic mean of the five specimen measurements was taken as the final test result. When the adhesive layer was completely cured along the thickness direction and no uncured paste-like area was observed in the cross-section, the curing depth was recorded as 15 mm.

[0087] (3) Tensile strength and elongation at break

[0088] The sealant was prepared into 2 mm thick sheet specimens under standard conditions. After curing for 7 days, the specimens were cut into dumbbell shapes (Type 1) according to GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber". The tensile strength and elongation at break were tested at a tensile speed of 500 mm / min. Five specimens were tested in each group, and the arithmetic mean was taken.

[0089] 2. Test Results

[0090] The test results of each embodiment and comparative example are shown in Table 1.

[0091] Table 1

[0092]

[0093] The test results in Table 1 show that:

[0094] (1) Regarding the surface drying time, the surface drying time of Examples 1-3 was 13-18 min, which was basically the same as that of Comparative Examples 1 and 2. This indicates that the addition of the shrinkage-responsive microspheres of the present invention did not significantly inhibit the hydrolysis and condensation reaction of the sealant surface layer, and the sealant still maintained a relatively fast surface drying speed. The surface drying times of Comparative Examples 4 and 5 were extended to 45 min and 38 min, respectively, indicating that the composition of the coating layer and the condensation reaction conditions during the coating stage would have a certain impact on the initial curing behavior of the sealant.

[0095] (2) Regarding the depth of deep curing, the curing depth of Examples 1-3 at each test time point was significantly higher than that of Comparative Example 1. Taking Example 3 as an example, the curing depth was 4.8 mm at 24 h, increased to 9.0 mm at 48 h, and further reached 13.0 mm at 72 h, indicating that the shrinkage-responsive microspheres used in this invention can significantly promote the curing process of the sealant from the surface to the interior. Comparative Example 1 did not add microspheres, and the curing depth at 72 h was only 5.0 mm; Comparative Example 2 used uncoated borosilicate glass microspheres, and its curing depth at 72 h was 6.5 mm, which was higher than that of Comparative Example 1, but still significantly lower than that of Example 1, indicating that simply adding rigid glass microspheres cannot obtain the same deep curing promotion effect as the shrinkage-responsive microspheres of this invention, and the flexible coating structure on the surface of the microspheres has an important influence on exerting this effect. Comparative Example 4 did not add hydroxyl-terminated oligodimethylsiloxane to the coating system, and its curing depth at each time point was significantly lower than that of Example 1, indicating that the oligodimethylsiloxane segments play an important role in regulating the microsphere interface state and promoting deep curing. Comparative Example 5 increased the reaction temperature and significantly prolonged the reaction time during the coating stage, but its 72-hour curing depth was only 5.5 mm, significantly lower than that of Example 1. This indicates that the appropriate degree of condensation reaction in the coating layer has a significant impact on the effect of shrinkage-responsive microspheres in promoting deep curing. It is noteworthy that Comparative Example 3, without the addition of methyltrimethoxysilane and vinyltrimethoxysilane to the microsphere coating system, still achieved a 72-hour curing depth of 8.5 mm, indicating that the interfacial structure formed by the oligomeric siloxane treatment can promote the migration of moisture into the colloid to a certain extent. However, its tensile strength and elongation at break after complete curing decreased significantly, indicating that the lack of alkoxysilane groups that can continue to undergo hydrolysis and condensation reactions is detrimental to the integrity of the interface and the maintenance of the material's mechanical properties after curing.

[0096] (3) Regarding tensile strength and elongation at break, Examples 1-3 all maintained good mechanical properties, with tensile strengths all exceeding 1.0 MPa and elongation at break all exceeding 600%. Compared with Comparative Example 1, which did not contain shrinkage-responsive microspheres, there was no significant deterioration, indicating that the shrinkage-responsive microspheres used in this invention did not significantly adversely affect the bulk mechanical properties of the sealant after complete curing while promoting deep curing. In Comparative Example 3, since the microsphere surface treatment system did not contain methyltrimethoxysilane and vinyltrimethoxysilane, its tensile strength decreased to 0.6 MPa and its elongation at break decreased to 350%, significantly lower than that of Example 1. This indicates that the lack of alkoxysilane groups that can continue to undergo hydrolysis and condensation reactions is not conducive to the integrity of the interface between the microspheres and the silicone matrix and the maintenance of the material's mechanical properties after curing. Combining the results of Comparative Example 3 showing a certain deep curing promotion effect, it can be seen that while promoting the migration of moisture into the colloid, maintaining the interfacial bonding after curing through the hydrolyzable condensation groups in the coating layer plays an important role in balancing deep curing performance and final mechanical properties. Comparative Example 2 uses uncoated glass microspheres, and its tensile strength and elongation at break are lower than those of Example 1, further illustrating that a well-designed flexible coating structure on the surface of the microspheres is beneficial to balancing deep curing performance and final mechanical properties.

[0097] In summary, this invention introduces borosilicate glass microspheres with a specific surface coating structure into a silicone sealant system. Utilizing the shrinkage difference between the rigid microspheres and the silicone matrix during curing, as well as the interfacial modulation effect of the flexible coating layer, a transient interfacial state is formed that facilitates the migration of moisture into the sealant, thereby improving the deep curing rate of the sealant. The oligomeric siloxane segments in the coating layer help regulate the interfacial response between the microspheres and the matrix, while the retained hydrolyzable condensable alkoxysilane groups help maintain the interfacial integrity after curing, allowing the sealant to achieve good deep curing performance while maintaining good mechanical properties. Test results show that this invention can significantly improve deep curing performance while maintaining a relatively fast surface drying rate, and also takes into account the mechanical properties after complete curing, thus solving the problem of existing single-component silicone sealants struggling to achieve both rapid surface drying and deep curing.

[0098] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A fast-curing antibacterial and mildew-resistant silicone sealant, characterized in that, The raw materials include the following parts by weight: 100 parts α,ω-dihydroxypolydimethylsiloxane, 8-10 parts methyl silicone oil, 55-65 parts nano-activated calcium carbonate, 4-6 parts hydrophobic fumed silica, 5.0-5.8 parts methyltrimethoxysilane, 0.8-1.2 parts vinyltrimethoxysilane, 0.45-0.65 parts γ-aminopropyltriethoxysilane, 0.10-0.14 parts dibutyltin dilaurate, 0.25-0.35 parts zinc pyridinethione, 0.10-0.18 parts carbendazim, and 3.0-4.0 parts shrinkage-responsive microspheres; The shrinkage-responsive microspheres comprise borosilicate glass microspheres and a flexible coating layer covering the surface of the borosilicate glass microspheres. The flexible coating layer contains oligomeric siloxane segments and hydrolyzable alkoxysilane groups.

2. The fast-curing antibacterial and mildew-resistant silicone sealant according to claim 1, characterized in that, The shrinkage-responsive microspheres are prepared from raw materials comprising the following parts by weight: 100 parts borosilicate glass microspheres, 2.5-3.5 parts hydroxyl-terminated oligomeric dimethylsiloxane, 0.35-0.50 parts methyltrimethoxysilane, 0.15-0.25 parts vinyltrimethoxysilane, 0.003-0.006 parts dibutyltin dilaurate, and 150-180 parts anhydrous n-heptane.

3. The rapid-curing antibacterial and mildew-resistant silicone sealant according to claim 2, characterized in that, The preparation steps of the shrinkage-responsive microspheres are as follows: after drying borosilicate glass microspheres, they are coated with a coating solution formed by dissolving hydroxyl-terminated oligomeric dimethylsiloxane, methyltrimethoxysilane, vinyltrimethoxysilane, and dibutyltin dilaurate in anhydrous n-heptane; then the temperature is raised to 55-60℃ and reacted under anhydrous conditions for 60-80 minutes to allow partial condensation of the coating components and retention of hydrolyzable alkoxysilane groups; finally, the solvent is removed and the microspheres are dried to obtain the shrinkage-responsive microspheres.

4. The rapid-curing antibacterial and mildew-resistant silicone sealant according to claim 1, characterized in that, The D50 of the borosilicate glass microspheres is 8-12 μm.

5. The rapid-curing antibacterial and mildew-resistant silicone sealant according to claim 1, characterized in that, The viscosity of the α,ω-dihydroxy polydimethylsiloxane at 25°C is 50,000-80,000 mPa·s; the viscosity of the methyl silicone oil at 25°C is 100-350 mPa·s; and the viscosity of the hydroxyl-terminated oligomeric dimethylsiloxane at 25°C is 50-100 mPa·s.

6. The rapid-curing antibacterial and mildew-resistant silicone sealant according to claim 1, characterized in that, The mass ratio of methyltrimethoxysilane to vinyltrimethoxysilane is (4-6.5):

1.

7. The rapid-curing antibacterial and mildew-resistant silicone sealant according to claim 1, characterized in that, The average particle size of the nano-active calcium carbonate is 60-100 nm.

8. The rapid-curing antibacterial and mildew-resistant silicone sealant according to claim 1, characterized in that, The specific surface area of ​​the hydrophobic fumed silica is 150-250 m² / g.

9. The rapid-curing antibacterial and mildew-resistant silicone sealant according to claim 1, characterized in that, The mass ratio of zinc pyrithione to carbendazim is (1.5-3):

1.

10. A method for preparing a rapid-curing antibacterial and antifungal silicone sealant as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Add α,ω-dihydroxy polydimethylsiloxane, methyl silicone oil, nano-activated calcium carbonate and hydrophobic fumed silica to a kneader and knead and dehydrate under vacuum at 110-120℃ until the water content of the mixture is less than 500 ppm, and then cool down to below 40℃. S2. Add the shrinkage-responsive microspheres and mix at 100-200 r / min for 20-30 minutes. S3. Add methyltrimethoxysilane, vinyltrimethoxysilane and γ-aminopropyltriethoxysilane in sequence, and mix under vacuum for 20-30 minutes; S4. Add zinc pyrithione, carbendazim and dibutyltin dilaurate, and mix for 15-20 minutes under vacuum at a temperature not exceeding 35°C to remove air bubbles. S5. Fill the container into a moisture-proof and sealed container in a dry nitrogen environment to obtain a fast-curing antibacterial and mildew-proof silicone sealant.

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