Mildew-proof silicone adhesive and preparation method thereof

Abstract

The invention discloses a mildew-proof silicone adhesive and a preparation method thereof, belongs to the technical field of polymer sealing materials, and aims to solve the problems of short mildew-proof life and environmental pollution of the existing mildew-proof sealant. The mildew-proof silicone adhesive is prepared from the following raw materials in parts by weight: 100 parts of basic adhesive, 10 to 25 parts of plasticizer, 5 to 12 parts of reinforcing filler, 40 to 80 parts of filling filler, 4 to 8 parts of cross-linking agent, 1 to 3 parts of biological avoidance modifier, 0.5 to 2.0 parts of phase separation inducer A, 0.75 to 3.0 parts of phase separation inducer B and 0.05 to 0.2 part of catalyst, the phase separation inducer A is perfluoropolyether modified silane; the phase separation inducer B is long-chain alkyl silane; the biological avoidance modifier is salicylate modified silane; the reinforcing filler is fumed silica; the filling filler is nano calcium carbonate. The waterproof mildew-proof paint does not contain heavy metals and toxic mildew-proof components, has excellent hydrophobic self-cleaning property and long-acting mildew-proof property, and is particularly suitable for joint sealing in high-humidity environments such as kitchens and toilets in building decoration.

Description

Technical Field

[0001] This invention relates to the field of polymer sealing materials technology, and in particular to an anti-mildew silicone sealant and its preparation method. Background Technology

[0002] Room temperature vulcanizing (RTV) silicone sealants are widely used in building joint sealing due to their excellent weather resistance, good adhesion, and elasticity. However, in environments with high humidity and abundant nutrients, such as kitchens and bathrooms, ordinary silicone sealants are prone to mold growth, causing the sealant to turn black or yellow. This not only affects aesthetics but also releases spores that can harm human health. Existing anti-mold strategies mainly fall into the following categories: (1) Add traditional organic antifungal agents: such as carbendazim, isothiazolinone, etc. These antifungal agents mainly rely on migrating to the colloidal surface and releasing toxic substances to kill mold. The problem is that the antifungal agents will be lost over time, resulting in antifungal failure. They usually have a lifespan of only 1-2 years, and the released toxins are harmful to the environment and human body.

[0003] (2) Add inorganic antibacterial agents: such as silver-loaded zeolite, nano zinc oxide, nano titanium dioxide, etc. Although the volatility problem is solved, inorganic powders are difficult to disperse in organosilicon matrix, are prone to agglomeration, and depend on the release of metal ions.

[0004] (3) Quaternary ammonium salt or chitosan modification: using positive charge adsorption for sterilization. However, quaternary ammonium salts have poor temperature resistance, easily cause colloidal yellowing, and are highly toxic to aquatic organisms.

[0005] Chinese patent CN113185922A discloses a fast-drying, mildew-resistant neutral silicone weather-resistant adhesive and its preparation method. The core technology involves adding a mixture of diatomaceous earth and chitosan as an antibacterial agent to the silicone adhesive system through physical blending, utilizing the bio-antibacterial properties of chitosan to achieve the mildew-resistant effect. This mildew-resistant system falls under the category of physical blending of additives. The chitosan antibacterial agent degrades or wears away over time, resulting in insufficient long-term mildew resistance. Furthermore, this technology does not alter the surface properties of the adhesive itself; the surface remains easily wetted and adheres to dirt, providing a breeding ground for mold growth.

[0006] In summary, existing technologies generally present a contradiction between long-lasting anti-mold performance and environmental safety, and most neglect the anti-fouling properties of the sealant surface. If the sealant surface has high surface energy, it easily attracts nutrients, providing a breeding ground for mold, and relying solely on bactericides is insufficient to address the problem at its root. Therefore, developing a non-toxic, non-releasing anti-mold sealant with high hydrophobicity and biorepellency is an urgent need for the industry. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide an anti-mildew silicone sealant and its preparation method.

[0008] The specific technical solution is as follows: An anti-mildew silicone sealant, comprising the following raw materials in parts by weight: 100 parts base adhesive, 10-25 parts plasticizer, 5-12 parts reinforcing filler, 40-80 parts filler, 4-8 parts crosslinking agent, 1-3 parts bio-repellent modifier, 0.5-2.0 parts phase separation inducing agent A, 0.75-3.0 parts phase separation inducing agent B, and 0.05-0.2 parts catalyst; wherein phase separation inducing agent A is a perfluoropolyether modified silane; phase separation inducing agent B is a long-chain alkyl silane; bio-repellent modifier is a salicylate modified silane; reinforcing filler is fumed silica; and filler is nano-calcium carbonate.

[0009] Furthermore, the perfluoropolyether modified silane is a compound whose molecular chain contains a perfluoropolyether segment at one end and a trialkoxysilyl group at the other end; the long-chain alkylsilane is hexadecyltrimethoxysilane or octadecyltrimethoxysilane.

[0010] Furthermore, the preparation method of the perfluoropolyether modified silane is as follows: take a carboxyl-terminated perfluoropolyether, add an equimolar amount of γ-aminopropyltriethoxysilane, and finally add a catalyst. Under nitrogen protection, heat to 120-145℃ and continue the reaction. The reaction process is carried out under vacuum until the acid value of the reaction system is lower than 2 mg KOH / g, and then cool down and discharge the material. The number average molecular weight of the carboxyl-terminated perfluoropolyether is 1500 g / mol. The catalyst is dibutyltin oxide, and its addition amount is 0.1% of the weight of the carboxyl-terminated perfluoropolyether.

[0011] Furthermore, the salicylate-modified silane molecule contains salicylate structural units linked by covalent bonds; the preparation method of the salicylate-modified silane is as follows: take γ-glycidoxypropyltrimethoxysilane, heat to 90°C, add an equimolar amount of salicylic acid, and finally add a catalyst. Under nitrogen protection, heat to 95-100°C and continue the reaction. The reaction process is carried out under vacuum until the acid value drops below 10 mg KOH / g, and then the material is cooled and discharged; the catalyst is tetrabutylammonium bromide, and its addition amount is 2% of the weight of γ-glycidoxypropyltrimethoxysilane.

[0012] Furthermore, the base adhesive is α,ω-dihydroxypolydimethylsiloxane; the plasticizer is dimethyl silicone oil; the crosslinking agent is methyltributanone oxime silane or vinyltributanone oxime silane; and the catalyst is dibutyltin dilaurate or dibutyltin diacetate.

[0013] Furthermore, the preparation method of the anti-mildew silicone sealant includes the following steps: S1: Mix the base adhesive, plasticizer and filler, and dehydrate under vacuum heating. After dehydration, cool to below 40°C to obtain the base material. S2: Add reinforcing filler to the above base material and stir under vacuum for 15 minutes; then, under anhydrous and air-isolated conditions, add crosslinking agent, bio-repellent modifier, phase separation inducer A, and phase separation inducer B in sequence, mix for 10 minutes, and then add catalyst; S3: After high-speed shearing dispersion and vacuum degassing, the product is discharged and packaged.

[0014] Furthermore, the vacuum heating conditions in step S1 are: temperature 110℃ and vacuum degree -0.098MPa.

[0015] Furthermore, in step S2, the weight ratio of phase separation inducing agent A to phase separation inducing agent B is 1:1.5.

[0016] Furthermore, the high-speed shear dispersion conditions described in step S3 are as follows: high-speed shear dispersion is performed for 20 minutes at a rotation speed of 30-45Hz.

[0017] Furthermore, the vacuum degassing conditions in step S3 are as follows: degassing for 10 minutes under a vacuum of -0.098 MPa.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) Synergistic effect of physical anti-mildew and chemical repulsion: By making the surface of the silicone glue highly hydrophobic and self-cleaning after curing, the water and nutrient sources required for the growth of mold are blocked; at the same time, groups with biological repulsion function are fixed in the silane molecules, thereby inhibiting hyphal attachment and achieving a synergistic anti-mildew effect of physical isolation and chemical repulsion.

[0019] (2) Long-lasting and non-leaking: The functional additives used in this invention all contain hydrolyzable alkoxysilane groups, which participate in the cross-linking network during the curing process and become part of the polymer. They will not migrate and be lost over time like traditional antifungal agents, thus achieving antifungal protection throughout the entire life cycle.

[0020] (3) Environmentally friendly: This invention does not contain heavy metals, quaternary ammonium salts, or pesticide components such as carbendazim, and has no reproductive toxicity, which is in line with the development trend of green building materials. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the preparation process of an anti-mildew silicone sealant according to the present invention. Figure 2 The images show the surface water contact angles of the anti-mildew silicone sealants prepared in Examples 1-3 and Comparative Examples 1-3 after curing. Detailed Implementation

[0022] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0023] The present invention proposes an anti-mildew silicone sealant, as shown in the attached figure. Figure 1 The diagram shows the preparation process flow chart of the anti-mildew silicone sealant. The anti-mildew silicone sealant is made from the following components in parts by weight: 100 parts base adhesive, 10-25 parts plasticizer, 5-12 parts reinforcing filler, 40-80 parts filler, 4-8 parts crosslinking agent, 1-3 parts bio-repellent modifier, 0.5-2.0 parts phase separation inducing agent A, 0.75-3.0 parts phase separation inducing agent B, and 0.05-0.2 parts catalyst.

[0024] The phase separation inducing agent A is a perfluoropolyether-modified silane, a compound whose molecular chain contains perfluoropolyether segments at one end and trialkoxysilane groups at the other end. During the curing process of silicone sealant, the perfluoropolyether-modified silane spontaneously migrates to the surface of the sealant under thermodynamic drive, forming a low surface energy enriched layer rich in perfluoropolyether segments. This provides excellent oleophobicity, preventing soap scum, dander, grease, and other mold nutrients from adhering to the sealant surface. The preparation steps of the perfluoropolyether-modified silane are as follows: Take the number average molecular weight M n A carboxyl-terminated perfluoropolyether (PFPE-COOH) of 1500 g / mol was mixed with an equimolar amount of γ-aminopropyltriethoxysilane (KH-550) and 0.1% by weight of dibutyltin oxide (DBTO) as a catalyst. The mixture was heated to 120-145 °C under nitrogen protection and the reaction was continued. During the reaction, low-molecular-weight byproducts generated during the reaction were continuously removed by vacuum decompression. The reaction was continued until the acid value of the reaction system was lower than 2 mg KOH / g. The mixture was then cooled and discharged to obtain a perfluoropolyether-modified silane.

[0025] The phase separation inducing agent B is a long-chain alkylsilane, preferably hexadecyltrimethoxysilane or octadecyltrimethoxysilane.

[0026] The bio-repellent modifier is a salicylic acid ester-modified silane. Through the participation of trialkoxysilane groups in the crosslinking network of silicone sealant, salicylic acid ester molecules with repellent properties are covalently anchored in the colloidal backbone. Unlike the killing mechanism of traditional antifungal agents, this adjuvant continuously releases bioprotective signals, inhibiting the bioattachment and anchoring of fungal hyphae, and does not dissipate over time, ensuring long-lasting effectiveness and environmental friendliness. The preparation steps of the salicylic acid ester-modified silane are as follows: γ-glycidoxypropyltrimethoxysilane (KH-560) was heated to 90°C, and an equimolar amount of salicylic acid and 2% (by weight of KH-560) of tetrabutylammonium bromide were added as a catalyst. Under nitrogen protection, the temperature was maintained at 95-100°C, and the reaction was continued. Low-molecular-weight byproducts generated during the reaction were continuously removed by vacuum reduction until the acid value of the reaction system dropped below 10 mg KOH / g, at which point the reaction was terminated. The product was then cooled and discharged, yielding a biorepellent modifier. This reaction anchors the bioactive salicylic acid structure to the silane via ester bonds.

[0027] The method for determining the acid value of the reaction system is as follows: Accurately weigh a certain amount of the reaction solution to be tested, add it to a pre-prepared neutral ethanol-toluene mixed solvent, and dissolve it completely at room temperature to form a homogeneous solution. Add phenolphthalein indicator to the solution, and titrate with a standard concentration of potassium hydroxide ethanol solution until the solution reaches a pale red endpoint that does not fade for 30 seconds. Simultaneously, perform a blank control titration and record the volume of potassium hydroxide solution consumed in the blank system. Based on the difference in the volume of potassium hydroxide solution consumed by the sample and blank titrations, calculate the mass of potassium hydroxide required to neutralize free carboxyl groups per gram of sample, and obtain the acid value of the system, expressed in mgKOH / g.

[0028] The base adhesive is α,ω-dihydroxypolydimethylsiloxane (107 adhesive); the plasticizer is dimethyl silicone oil; the reinforcing filler is fumed silica; the filler is nano-calcium carbonate; the crosslinking agent is methyltributanone oxime silane or vinyltributanone oxime silane; and the catalyst is dibutyltin dilaurate or dibutyltin diacetate.

[0029] During the curing process of the silicone sealant, low surface energy perfluoropolyether segments spontaneously migrate and accumulate towards the colloid-air interface under thermodynamic drive. These segments, along with long-chain alkyl segments, participate in surface phase regulation, resulting in a surface layer rich in low surface energy groups. Simultaneously, fumed silica and nano-calcium carbonate fillers introduce surface undulations during curing, amplifying the hydrophobic properties based on the low surface energy chemical composition. This results in a stable, highly hydrophobic surface with excellent self-cleaning ability, physically reducing moisture retention and inhibiting mold growth by physically isolating the moisture required for mold growth.

[0030] The preparation method of the above-mentioned anti-mildew silicone sealant includes the following steps: (1) Base material preparation: The metered base adhesive, plasticizer, and filler are put into a double planetary power mixer. First, low-speed stirring is started to completely wet the powder, and then high-speed dispersion is started. At the same time, the temperature is raised to 110°C and dynamic dehydration stirring is carried out for 2 hours under a vacuum of -0.098MPa. This step aims to completely remove the physically adsorbed water in the raw materials to prevent the subsequent crosslinking agent from hydrolyzing prematurely. After dehydration is completed, the temperature is lowered to below 40°C to obtain the base material for later use.

[0031] (2) Mixing and preparing the adhesive: Add reinforcing filler to the cooled base material, and alternately stir at low speed and crush at high speed under vacuum for 15 minutes until the adhesive is fine and free of visible particles. Then, under anhydrous and air-isolated conditions, add crosslinking agent, bio-repellent modifier, phase separation inducer A, and phase separation inducer B in sequence, mix at low speed for 10 minutes to allow the functional monomers to diffuse fully; finally, add catalyst. The weight ratio of phase separation inducer A to phase separation inducer B is 1:1.5.

[0032] (3) High-speed shear dispersion and vacuum packaging: Turn on the high-speed disperser at a speed of 30-45 Hz and perform high-speed shear dispersion for 20 minutes to ensure that all functional components are uniformly dispersed at the molecular level in the colloid, and to further break up filler agglomerates. Finally, maintain a vacuum of -0.098 MPa for vacuum degassing for 10 minutes to eliminate microbubbles introduced during mixing. Dispense into sealed cartridges and store in a light-proof container.

[0033] Table 1. Reagents used in the examples and comparative examples.

[0034] Example 1 1. Preparation of perfluoropolyether modified silanes Take 150 parts of PFPE-COOH, add 23 parts of KH-550 and 0.15 parts of DBTO, and heat to 120-145℃ under nitrogen protection to carry out the reaction. During the reaction, low molecular weight byproducts generated during the reaction are continuously removed by vacuum decompression. After 6 hours of reaction, the acid value of the reaction system is 1.8 mgKOH / g. Cool down and discharge to obtain perfluoropolyether modified silane for later use.

[0035] 2. Preparation of biological repellent modifiers Take 24 parts of KH-560 and heat it to 90℃. Add 14 parts of salicylic acid and 0.48 parts of tetrabutylammonium bromide. Under nitrogen protection, heat to 95-100℃ for reaction. During the reaction, continuously remove low-molecular-weight byproducts generated during the reaction by vacuum decompression. After 4 hours of reaction, the acid value of the reaction system decreases by 8.5 mg KOH / g. Cool down and discharge to obtain salicylic ester modified silane for later use.

[0036] 3. Preparation of anti-mildew silicone sealant (1) 100 parts of 107 glue, 17.5 parts of dimethyl silicone oil and 60 parts of nano calcium carbonate were put into a double planetary power mixer and dehydrated and stirred for 2 hours under vacuum conditions of 110℃ and -0.098MPa. The base material was obtained by cooling to below 40℃.

[0037] (2) Add 8 parts of fumed silica to the above base material and alternately stir at low speed and crush at high speed under vacuum for 15 minutes. Under anhydrous and air-isolated conditions, add 6 parts of methyl tributanone oxime silane, 2 parts of salicylate-modified silane, 1 part of perfluoropolyether-modified silane, and 1.5 parts of hexadecyltrimethoxysilane in sequence, mix at low speed for 10 minutes, and then add 0.1 parts of dibutyltin dilaurate. Disperse rapidly at high shear at 40 Hz for 20 minutes. Finally, after vacuum degassing at -0.098 MPa for 10 minutes, dispense into sealed cartridges.

[0038] Example 2 The perfluoropolyether-modified silane and salicylate-modified silane were from the same batch as in Example 1. The formulation of the anti-mildew silicone sealant was as follows: 100 parts of 107 sealant, 10 parts of dimethyl silicone oil, 5 parts of fumed silica, 40 parts of nano-calcium carbonate, 4 parts of vinyltributylone oxime silane, 1 part of salicylate-modified silane, 0.5 parts of perfluoropolyether-modified silane, 0.75 parts of octadecyltrimethoxysilane, and 0.05 parts of dibutyltin diacetate. The preparation process was the same as in Example 1.

[0039] Example 3 The perfluoropolyether-modified silane and salicylate-modified silane were from the same batch as in Example 1. The formulation of the anti-mildew silicone sealant was as follows: 100 parts of 107 sealant, 25 parts of dimethyl silicone oil, 12 parts of fumed silica, 80 parts of nano-calcium carbonate, 8 parts of methyl tributanone oxime silane, 3 parts of salicylate-modified silane, 2 parts of perfluoropolyether-modified silane, 3 parts of hexadecyltrimethoxysilane, and 0.2 parts of dibutyltin dilaurate. The preparation process was the same as in Example 1.

[0040] Comparative Example 1 Meanwhile, in Example 1, the difference is that salicylate-modified silane, perfluoropolyether-modified silane, and hexadecyltrimethoxysilane were not added. Instead, 2 parts of carbendazim and 3 parts of conventional aminosilane coupling agent KH-550 were added to prepare a traditional anti-mildew silicone sealant.

[0041] Comparative Example 2 Same as Example 1, except that no perfluoropolyether modified silane was added.

[0042] Comparative Example 3 Same as Example 1, except that hexadecyltrimethoxysilane was not added.

[0043] Comparative Example 4 Same as Example 1, except that no salicylate-modified silane was added.

[0044] Performance testing 1. Basic physicochemical property testing Refer to GB / T 14683-2017 "Silicone and Modified Silicone Building Sealants".

[0045] Test objective: To verify that the anti-mildew modification does not significantly affect the basic physicochemical properties.

[0046] Surface drying time test: The sample is extruded into a strip with a thickness of about 2 mm under standard test conditions, and the time it takes for the glass rod to lightly touch the surface of the film without adhesion is recorded in minutes.

[0047] Tensile property test: After the test sample adhesive is cured for 21 days under standard test conditions, dumbbell-shaped specimens are prepared. The tensile strength (MPa) and elongation at break (%) are recorded using an electronic tensile testing machine at a tensile speed of 500 mm / min.

[0048] Sagging test: Tested in a standard U-shaped groove. After the sample has been cured for 7 days under standard test conditions, it is placed vertically for 30 minutes and the sag distance of the colloid is observed. The unit is mm.

[0049] Extrudability test: Tests the volume of colloid extruded from a standard nozzle per unit time under standard conditions, in mL / min.

[0050] Elastic recovery rate test: The sample, cured for 21 days under standard test conditions, is stretched to 100% of its original length, held for 1 hour, and then released. Its recovery is measured and the elastic recovery rate (%) is calculated.

[0051] Water immersion adhesion test: After the adhesive is bonded to a standard substrate and cured under standard conditions, it is immersed in water at 23±2℃ for 7 days. After removal, a 100% elongation test is performed to observe whether the bonding interface is damaged.

[0052] Cold-stretch-hot-press adhesion test: The adhesive is bonded to a standard substrate and cured under standard conditions. It is then placed in a -20°C low-temperature chamber, stretched to 100% displacement, and held for 3 hours. Next, it is transferred to a 70°C oven and compressed to 25% displacement, held for 3 hours. This constitutes one cycle. After repeating this cycle 10 times, a 100% constant elongation test is performed under standard conditions to observe whether the bond interface is damaged. This test simulates the long-term bonding durability of the sealant after experiencing winter and summer temperature cycles and joint displacement.

[0053] 2. Surface hydrophobicity test Refer to GB / T 30693-2014 "Measurement of the contact angle between plastic film and water".

[0054] Test objective: To verify the formation of low surface energy hydrophobic surfaces.

[0055] Sample preparation: The adhesive sample to be tested is cured for 7 days under standard test conditions to make a flat film.

[0056] Testing instrument: Contact angle measuring instrument.

[0057] Specific steps: Drop 5 μL of deionized water onto the film surface, measure and record the static contact angle of the water droplet on the film surface. Test 5 different locations for each sample and take the average value.

[0058] 3. Anti-mildew performance test Refer to GB / T 1741-2020 "Determination of resistance to mold in paint films".

[0059] Test objective: To verify the anti-mildew effect.

[0060] Sample preparation: After the adhesive to be tested is cured for 7 days under standard test conditions, a 50mm×50mm test piece is prepared.

[0061] Specific steps: Place the test piece in a petri dish containing inorganic salt medium. Use a spray method to evenly inoculate the surface of the test piece with a mixed spore suspension of Aspergillus niger and Aspergillus flavus. Place the petri dish in a constant temperature and humidity incubator and incubate for 28 days at 28±1℃ and relative humidity ≥95%. After incubation, observe the mold growth level: level 0 indicates no mold growth, and level 4 indicates severe mold growth.

[0062] 4. Long-lasting simulation (anti-mold after soaking): Test objective: To verify the non-migration and long-lasting effectiveness of the anti-mildew structure.

[0063] Specific steps: After curing the adhesive sample to be tested for 7 days under standard test conditions, soak it in 50℃ warm water for 14 days to simulate long-term showering. After taking out the sample, use filter paper to absorb the surface moisture, place it under standard conditions for 24 hours to allow it to recover, and then conduct the above anti-mold culture test again.

[0064] Table 2. Basic physicochemical performance test results of the examples and comparative examples.

[0065] Table 3. Basic physicochemical performance test results of the examples and comparative examples.

[0066] Table 4. Test results of surface hydrophobicity and antifungal properties of the examples and comparative examples.

[0067] Results Analysis (1) As shown in Tables 2 and 3, the sag, extrudability, surface drying time, mechanical properties, elastic recovery rate, and durability of Examples 1-3 of the present invention fully meet the requirements for high-quality silicone building sealants in GB / T 14683-2017. In particular, in the stringent durability test, the sample of the examples also passed the tests of adhesion after water immersion and adhesion after cold stretching-hot pressing. This shows that the perfluoropolyether modified silane, long-chain alkyl silane, and salicylate modified silane introduced in the present invention have good compatibility with the basic formulation system. They not only do not have a negative impact on the workability and basic mechanical properties of the product, but also do not weaken its bonding stability and durability under harsh environments such as long-term water immersion, high and low temperature cycling, and repeated displacement. In contrast, Comparative Example 1, which uses a combination of traditional small-molecule antifungal agents and conventional coupling agents, is similar to the example in some basic mechanical properties, but shows signs of adhesion failure in durability tests. This indicates that under long-term water immersion and thermo-mechanical coupling conditions, this type of antifungal system is difficult to simultaneously achieve both antifungal effect and adhesion stability.

[0068] (2) As shown in Table 4, the cured surfaces of the samples in Examples 1-3 all exhibited excellent hydrophobic properties, with water contact angles significantly higher than those of Comparative Example 1, which did not contain perfluoropolyether-modified silane or long-chain alkyl silane, as shown in the attached table. Figure 2 The results indicate that while fumed silica and nano-calcium carbonate fillers provide basic support for the surface morphology, they are insufficient on their own to impart high hydrophobicity to the material. Only when low surface energy components are effectively enriched on the surface can the surface undulations introduced by the fillers amplify the hydrophobic properties. Meanwhile, Comparative Examples 2 and 3, lacking either perfluoropolyether-modified silane or long-chain alkyl silane respectively, exhibited significantly reduced hydrophobicity on their cured surfaces, failing to achieve a highly hydrophobic state. In summary, the results show that perfluoropolyether-modified silane and long-chain alkyl silane have a significant synergistic effect in enhancing the hydrophobicity of the cured surface in the system of this invention, and are crucial factors in achieving a high hydrophobic effect.

[0069] (3) As shown in Table 4, after soaking in hot water, the small molecule bactericide in Comparative Example 1 precipitated and was lost, resulting in a significant decrease in the anti-mold effect. In the embodiments of the present invention, since the salicylate and fluorosilicone segments are fixed on the colloidal organosilicon network by chemical bonds, the water washability is excellent, and the anti-mold effect remains at level 0 after soaking. Although Comparative Example 4 also constructed a highly hydrophobic surface, level 1 mold growth appeared in both the initial and post-soaking anti-mold tests. This indicates that although a simple physical hydrophobic barrier can block most molds, there is still a risk of hyphae anchoring and growth on some stubborn species or on accidentally formed micro-contamination points. The bonded salicylate-modified silane introduced in the embodiments can sustainably form a biosignal barrier on the colloidal surface, actively avoiding hyphae attachment and significantly improving the anti-mold performance.

[0070] In summary, this invention introduces perfluoropolyether-modified silanes, long-chain alkyl silanes, and salicylate-modified silanes into the silicone sealant system. By utilizing spontaneous microphase separation during the curing process, a stable, highly hydrophobic surface is constructed. Simultaneously, bio-repellent functional groups are anchored through chemical bonding. This synergistic effect of physical isolation and chemical repellency endows the silicone sealant with excellent and long-lasting anti-mold properties. The product of this invention achieves highly hydrophobic self-cleaning and long-lasting anti-mold properties without affecting the basic physical properties, and the functional components do not migrate or leak, solving the technical problems of short lifespan and poor environmental performance of existing anti-mold sealants.

Claims

1. A mildew-resistant silicone sealant, characterized in that, The silicone sealant is composed of the following raw materials in parts by weight: 100 parts base adhesive, 10-25 parts plasticizer, 5-12 parts reinforcing filler, 40-80 parts filler, 4-8 parts crosslinking agent, 1-3 parts bio-repellent modifier, 0.5-2.0 parts phase separation inducing agent A, 0.75-3.0 parts phase separation inducing agent B, and 0.05-0.2 parts catalyst; wherein phase separation inducing agent A is perfluoropolyether modified silane; phase separation inducing agent B is long-chain alkyl silane; bio-repellent modifier is salicylate modified silane; reinforcing filler is fumed silica; and filler is nano-calcium carbonate.

2. The anti-mildew silicone sealant as described in claim 1, characterized in that, The perfluoropolyether modified silane is a compound whose molecular chain contains a perfluoropolyether segment at one end and a trialkoxysilane group at the other end; the long-chain alkylsilane is hexadecyltrimethoxysilane or octadecyltrimethoxysilane.

3. The anti-mildew silicone sealant as described in claim 2, characterized in that, The preparation method of the perfluoropolyether modified silane is as follows: take a carboxyl-terminated perfluoropolyether, add an equimolar amount of γ-aminopropyltriethoxysilane, and finally add a catalyst. Under nitrogen protection, heat to 120-145℃ and continue the reaction. The reaction process is carried out under vacuum until the acid value of the reaction system is lower than 2mgKOH / g, and then the material is discharged after cooling. The number average molecular weight of the carboxyl-terminated perfluoropolyether is 1500g / mol. The catalyst is dibutyltin oxide, and its addition amount is 0.1% of the weight of the carboxyl-terminated perfluoropolyether.

4. The anti-mildew silicone sealant as described in claim 1, characterized in that, The salicylate-modified silane molecule contains salicylate structural units linked by covalent bonds; the preparation method of the salicylate-modified silane is as follows: take γ-glycidoxypropyltrimethoxysilane, heat to 90°C, add an equimolar amount of salicylic acid, and finally add a catalyst. Under nitrogen protection, heat to 95-100°C and continue the reaction. The reaction process is carried out under vacuum until the acid value drops below 10 mg KOH / g, and then the material is discharged after cooling; the catalyst is tetrabutylammonium bromide, and its addition amount is 2% of the weight of γ-glycidoxypropyltrimethoxysilane.

5. The anti-mildew silicone sealant as described in claim 1, characterized in that, The base adhesive is α,ω-dihydroxypolydimethylsiloxane; the plasticizer is dimethyl silicone oil; the crosslinking agent is methyltributanone oxime silane or vinyltributanone oxime silane; and the catalyst is dibutyltin dilaurate or dibutyltin diacetate.

6. A method for preparing an anti-mildew silicone sealant according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Mix the base adhesive, plasticizer and filler, and dehydrate under vacuum heating. After dehydration, cool to below 40°C to obtain the base material. S2: Add reinforcing filler to the above base material and stir under vacuum for 15 minutes; then, under anhydrous and air-isolated conditions, add crosslinking agent, bio-repellent modifier, phase separation inducer A, and phase separation inducer B in sequence, mix for 10 minutes, and then add catalyst; S3: After high-speed shearing dispersion and vacuum degassing, the product is discharged and packaged.

7. The method for preparing an anti-mildew silicone sealant as described in claim 6, characterized in that, The vacuum heating conditions described in step S1 are: temperature 110℃ and vacuum degree -0.098MPa.

8. The method for preparing an anti-mildew silicone sealant as described in claim 6, characterized in that, In step S2, the weight ratio of phase separation inducing agent A to phase separation inducing agent B is 1:1.

5.

9. The method for preparing an anti-mildew silicone sealant as described in claim 6, characterized in that, The high-speed shear dispersion conditions described in step S3 are: high-speed shear dispersion for 20 minutes at a rotation speed of 30-45Hz.

10. The method for preparing an anti-mildew silicone sealant as described in claim 6, characterized in that, The vacuum degassing conditions described in step S3 are: degassing for 10 minutes under a vacuum of -0.098 MPa.

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