Mildew-proof and antibacterial sealant and preparation method thereof

Abstract

The present application belongs to the technical field of sealant, and particularly relates to a mildew-proof and antibacterial sealant and a preparation method thereof. The mildew-proof and antibacterial sealant comprises the following raw materials: a mildew-proof and antibacterial modification composition, a polyurethane prepolymer, a filler, a coupling agent and an organic titanate catalyst. The preparation method of the mildew-proof and antibacterial modification composition comprises the following steps: S1, polymerizing a polyhydroxy compound with an epoxy pentane to obtain a high polyether polyol; S2, mixing the high polyether polyol, a carboxyl-containing unsaturated monomer and a polymerization inhibitor, and performing esterification under the action of an acid catalyst to obtain an end double bond modified polymer; and S3, mixing the end double bond modified polymer, an antibacterial agent, a silane coupling agent and a solvent, and performing a reaction under light irradiation to obtain the mildew-proof and antibacterial modification composition. By introducing reactive siloxane, quaternary ammonium salt antibacterial groups and hydrophobic side propyl functional structures into the molecular structure, the antibacterial ability and antibacterial durability of the sealant in a humid environment are enhanced, and the intrinsic mildew-proof and antibacterial properties are realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sealant, and particularly relates to a mildew-resistant and antibacterial sealant and a preparation method thereof. BACKGROUND

[0002] In the field of home decoration materials, sealant plays a crucial role. It is widely used in the joints between sanitary wares and countertops in kitchens and bathrooms, and between walls and furniture, bearing the key functions of waterproofing, sealing, and reinforcement. In these application scenarios, sealant is often exposed to harsh environments with high temperature and humidity, high oil pollution, and rich in various surfactants, making its surface vulnerable to mold invasion. Over time, not only does it easily lead to cracking and water leakage of the glue body, but also causes fungal contamination of the indoor environment, further increasing the health risks of the elderly, children, and people with allergic constitution.

[0003] To improve the mildew-resistant and antibacterial properties of sealant, a common approach is to add antibacterial agents. For example, Chinese Patent CN116200158A discloses a preparation method of a silane-modified polyether sealant with mildew-resistant and antibacterial properties. By adding inorganic and organic mildew-resistant agents, the material successfully achieves mildew-resistant and antibacterial effects. Chinese Patent CN118126671A discloses a preparation method of an antibacterial and mildew-resistant silicone sealant. By adding a hydrophobic agent, the sealant not only has hydrophobicity but also excellent antibacterial and mildew-resistant ability. Chinese Patent CN116463103A discloses a preparation method of an antibacterial and mildew-resistant sealant. By using a technical solution of Zn, Ce, and Cu co-doped MgO, the material achieves mildew-resistant and antibacterial properties. However, sealant often contains a large amount of small molecular substances such as silicone oil, alkane plasticizer, and crosslinking agent. When the sealant is exposed to a humid environment for a long time, the mildew-resistant agent will migrate and precipitate with these small molecular substances, resulting in a significant reduction in mildew-resistant effect, and even complete loss over time.

[0004] Therefore, it is an important demand in the field of home decoration sealants to develop a sealant that can stably immobilize mildew-resistant and antibacterial components in the system, effectively solve the problem of mildew-resistant agent migration and precipitation, and have excellent sealing performance and long-term mildew-resistant and antibacterial effect. Chinese Patent CN119193087A discloses a preparation method of an intrinsic antibacterial polyurethane pressure-sensitive adhesive. This method introduces antibacterial groups into the molecular structure through chemical modification, thereby improving the intrinsic antibacterial efficiency of the material. However, the hydrophobicity of this pressure-sensitive adhesive material is poor, which makes it at risk of reduced mold inhibition ability and antibacterial durability in outdoor or humid environments. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application aims to provide a mildew-proof and antibacterial sealant, which introduces reactive siloxane, quaternary ammonium salt bacteriostatic groups and hydrophobic side propyl functional structures in the molecular structure, avoids the problem of performance attenuation caused by migration of bacteriostatic components, improves the hydrophobicity of the sealant, enhances the bacteriostatic ability and antibacterial durability of the sealant in a humid environment, and thus realizes the intrinsic mildew-proof and antibacterial properties.

[0006] Another object of the present application is to provide a preparation method of the mildew-proof and antibacterial sealant, which is simple in process and easy to mass produce.

[0007] The technical solutions adopted by the present application are as follows:

[0008] The mildew-proof and antibacterial sealant comprises the following raw materials in parts by weight:

[0009] Mildew-proof and antibacterial modified composition: 45-55 parts;

[0010] Polyurethane prepolymer: 15-25 parts;

[0011] Filler: 15-39 parts;

[0012] Coupling agent: 1-5 parts;

[0013] Organic titanate catalyst: 0.05-0.15 parts;

[0014] The preparation method of the mildew-proof and antibacterial modified composition comprises the following steps:

[0015] S1, mixing and polymerizing a polyhydroxy compound and an epoxy pentane to obtain a high-governing polyether polyol;

[0016] S2, mixing the high-governing polyether polyol obtained in step S1, a carboxyl-containing unsaturated monomer and a polymerization inhibitor, and performing esterification under the action of an acid catalyst to obtain an end double bond modified polymer;

[0017] S3, mixing the end double bond modified polymer obtained in step S2, a bacteriostatic agent, a silane coupling agent and a solvent, and performing a reaction under the action of a photoinitiator through light irradiation to obtain a mildew-proof and antibacterial modified composition;

[0018] Preferably, the preparation method of the mildew-proof and antibacterial modified composition comprises the following steps:

[0019] S1, mixing a polyhydroxy compound and an epoxy pentane, and performing a polymerization reaction in the presence of an alkaline catalyst to obtain a high-governing polyether polyol;

[0020] S2, mixing the high polyether polyol, the carboxyl-containing unsaturated monomer and the polymerization inhibitor prepared in step S1, and performing esterification reaction under the action of an acid catalyst at 150-180 DEG C, and evaporating small molecule substances to control the mass of the distillate fraction, to prepare an end double bond modified polymer;

[0021] S3, mixing the end double bond modified polymer, the bacteriostatic agent, the silane coupling agent and the solvent prepared in step S2, and performing reaction under the action of a photoinitiator by ultraviolet irradiation to prepare a mildewproof and antibacterial modified composition; the mildewproof and antibacterial modified composition is a silane modified polymer.

[0022] The polyurethane prepolymer is prepared by reacting castor oil, isocyanate and a chain extender.

[0023] In step S1, the polyhydroxy compound is polyglycerol-8 or polyglycerol-6, and the number average molecular weight of the high polyether polyol is 8000-20000.

[0024] In step S2, the carboxyl-containing unsaturated monomer is acrylic acid, the molar ratio of the hydroxyl group in the high polyether polyol to the double bond in the carboxyl-containing unsaturated monomer is 1:(1-1.1), the polymerization inhibitor is chlorophenol, on one hand, the addition of chlorophenol can prevent self-polymerization of acrylic acid, on the other hand, chlorophenol itself has antibacterial property, and can participate in the crosslinking and curing reaction of the sealant due to the active hydrogen structure, and then is embedded into the molecular structure of the sealant, and the acid catalyst is p-toluenesulfonic acid.

[0025] In step S2, the amount of the polymerization inhibitor is 0.1-0.12 wt.% of the total mass of the high polyether polyol, the carboxyl-containing unsaturated monomer and the polymerization inhibitor, and the amount of the acid catalyst is 0.09-0.12 wt.% of the total mass of the high polyether polyol, the carboxyl-containing unsaturated monomer and the polymerization inhibitor.

[0026] In step S3, the bacteriostatic agent is N,N,N-trimethyl-(11-mercapto-undecyl) ammonium chloride, the silane coupling agent is 3-mercaptopropyl trimethoxysilane, the solvent is dimethyl carbonate, and the photoinitiator is benzoin dimethyl ether.

[0027] In step S3, the molar ratio of the bacteriostatic agent to the silane coupling agent is 3:(1.9-2), the molar ratio of the double bond in the end double bond modified polymer to the total mercapto group in the bacteriostatic agent and the silane coupling agent is 1:(1-1.1), and the amount of the photoinitiator is 0.2-0.6% of the total molar amount of the end double bond modified polymer, the bacteriostatic agent and the silane coupling agent.

[0028] In step S3, the amount of the solvent is 9.2-9.8 wt.% of the total mass of the end double bond modified polymer, the bacteriostatic agent, the silane coupling agent and the solvent.

[0029] The preparation method of the polyurethane prepolymer comprises the following steps:

[0030] After the castor oil is mixed with the isocyanate and reacted, a chain extender is added for continuous reaction, so that the polyurethane prepolymer with a content of -NCO of 4.7-4.9 wt.% is prepared.

[0031] Preferably, the preparation method of the polyurethane prepolymer comprises the following steps:

[0032] After the castor oil is mixed with the isocyanate and reacted at 60-70 DEG C for 1 h, a chain extender is added for continuous reaction for 1 h, so that the polyurethane prepolymer with a content of -NCO of 4.7-4.9 wt.% is prepared.

[0033] The isocyanate is hexamethylene diisocyanate, and the chain extender is bis(2-hydroxyethyl)dimethylammonium chloride.

[0034] The molar ratio of the castor oil, the isocyanate and the chain extender is 1:(2.7-2.8):(0.5-0.6).

[0035] The filler is fumed white carbon black or nano titanium dioxide.

[0036] The coupling agent is gamma-aminopropyltrimethoxysilane or gamma-isocyanate propyl triethoxysilane.

[0037] The organic titanate catalyst is tetrabutyl titanate.

[0038] The preparation method of the mildew-proof and antibacterial sealant comprises the following steps:

[0039] The mildew-proof and antibacterial modified composition, the polyurethane prepolymer and the filler are mixed and vacuum degassed, and then the organic titanate catalyst and the coupling agent are added and uniformly dispersed, so that the mildew-proof and antibacterial sealant is obtained.

[0040] Compared with the prior art, the present application has the following beneficial effects:

[0041] (1) In the mildew-proof and antibacterial modified composition adopted in the present application, the high polyether polyol is modified through esterification and click reaction, and the reaction-type siloxane and the quaternary ammonium salt bacteriostatic group are introduced into the molecular structure of the sealant, so that the efficiency attenuation caused by the migration and precipitation of the bacteriostatic component can be avoided.

[0042] (2) In the mildew-proof and antibacterial modified composition adopted in the present application, the hydrophobic side propyl is introduced into the molecular structure, and the hydrophobic long carbon chain bacteriostatic agent is selected, so that the hydrophobicity of the sealant can be significantly improved, and the inhibition capacity and the antibacterial durability of the sealant to the mold in the outdoor humid environment can be improved.

[0043] (3) The mold-proof and antibacterial modification composition used in the application can form silanol after contacting with moisture in the air, can cross-link with silane coupling agent and -NCO group, thereby covalently bonding the mold-proof and antibacterial substance to the cross-linking network structure of the sealant, realizing the intrinsic mold-proof and antibacterial characteristics of the material, and ensuring the long-term and stability of the antibacterial effect;

[0044] (4) The polyurethane prepolymer used in the application takes castor oil, isocyanate and bis(2-hydroxyethyl)dimethylammonium chloride as main raw materials. On the one hand, castor oil itself has hydrophobicity, which can enhance the water resistance of the sealant. On the other hand, the castor oil acid contained in castor oil and the quaternary ammonium salt structure contained in the chain extender have broad-spectrum antibacterial properties, which can synergistically improve the antibacterial range. In addition, the introduction of the polyurethane prepolymer can improve the adhesion of the sealant to the substrate and ensure the stability of the sealing interface. DETAILED DESCRIPTION

[0045] The application will be further described below in combination with examples, but it does not limit the implementation of the application.

[0046] The raw materials used in the examples and comparative examples are all conventional commercially available raw materials unless otherwise specified, and the process methods used in the examples and comparative examples are all conventional methods in the art unless otherwise specified.

[0047] Some of the raw materials used in the examples and comparative examples are described as follows:

[0048] High polyether polyol 1: 462g of polyglycerol-6 was catalyzed to polymerize 8628g of epoxy pentane under the catalysis of 34g of potassium hydroxide, after sufficient reaction, the high polyether polyol 1 was prepared after neutralization with acid water, drying, and adsorption purification treatment, and the number average molecular weight was 8000.

[0049] High polyether polyol 2: 462g of polyglycerol-6 was catalyzed to polymerize 17719g of epoxy pentane under the catalysis of 62g of potassium hydroxide, after sufficient reaction, the high polyether polyol 2 was prepared after neutralization with acid water, drying, and adsorption purification treatment, and the number average molecular weight was 16000.

[0050] High polyether polyol 3: 610g of polyglycerol-8 was catalyzed to polymerize 22129g of epoxy pentane under the catalysis of 65g of potassium hydroxide, after sufficient reaction, the high polyether polyol 3 was prepared after neutralization with acid water, drying, and adsorption purification treatment, and the number average molecular weight was 20000.

[0051] The preparation method of the mold-proof and antibacterial modification composition 1 comprises the following steps:

[0052] S1, high polyether polyol 1 is selected;

[0053] S2, 800 g of high polyether polyol 1, 57.6 g of acrylic acid and 0.86 g of chlorophenol were mixed, and esterification was carried out at 150°C under the catalysis of 0.86 g of p-toluenesulfonic acid, small molecule substances were removed by distillation, and the mass of the fraction was controlled to prepare an end double bond modified polymer;

[0054] S3, 0.5 mol of the end double bond modified polymer prepared in step S2, 2.4 mol of N,N,N-trimethyl-(11-mercapto-undecyl) ammonium chloride, 1.6 mol of 3-mercaptopropyl trimethoxysilane and 490 g of dimethyl carbonate were mixed, and the reaction was initiated by irradiation with 35±15 mW / cm 2 of ultraviolet light in the presence of 0.01 mol of benzoin dimethyl ether, and the reaction was continued until no signal of carbon-carbon double bond peak at 1640-1660 cm -1 was detected by infrared spectrometer, to obtain a mildew-resistant and antibacterial modified composition 1.

[0055] A preparation method of a mildew-resistant and antibacterial modified composition 2, comprising the following steps:

[0056] S1, high polyether polyol 2 was selected;

[0057] S2, 1600 g of high polyether polyol 2, 57.6 g of acrylic acid and 1.66 g of chlorophenol were mixed, and esterification was carried out at 160°C under the catalysis of 1.7 g of p-toluenesulfonic acid, small molecule substances were removed by distillation, and the mass of the fraction was controlled to prepare an end double bond modified polymer;

[0058] S3, 0.5 mol of the end double bond modified polymer prepared in step S2, 2.4 mol of N,N,N-trimethyl-(11-mercapto-undecyl) ammonium chloride, 1.6 mol of 3-mercaptopropyl trimethoxysilane and 1000 g of dimethyl carbonate were mixed, and the reaction was initiated by irradiation with 35±15 mW / cm 2 of ultraviolet light in the presence of 0.02 mol of benzoin dimethyl ether, and the reaction was continued until no signal of carbon-carbon double bond peak at 1640-1660 cm -1 was detected by infrared spectrometer, to obtain a mildew-resistant and antibacterial modified composition 2.

[0059] A preparation method of a mildew-resistant and antibacterial modified composition 3, comprising the following steps:

[0060] S1, high polyether polyol 3 was selected;

[0061] S2, 2000 g of high polyether polyol 3, 72 g of acrylic acid and 2.074 g of chlorophenol were mixed, and esterification was carried out at 180°C under the catalysis of 2 g of p-toluenesulfonic acid, small molecule substances were removed by distillation, and the mass of the fraction was controlled to prepare an end double bond modified polymer;

[0062] S3, mixing 0.5 mol of the terminal double bond modified polymer prepared in step S2, 3 mol of N,N,N-trimethyl-(11-mercapto-undecyl) ammonium chloride, 2 mol of 3-mercaptopropyl trimethoxysilane and 1200 g of dimethyl carbonate in the presence of 0.03 mol of benzoin dimethyl ether, and initiating the reaction by irradiation with 35±15 mW / cm 2 of ultraviolet light, and continuing the reaction until no signal of the carbon-carbon double bond peak at 1640-1660 cm -1 is detected by infrared spectroscopy, to obtain the mildew-resistant and antibacterial modified composition 3.

[0063] Polyurethane prepolymer: 931.5 g of castor oil was mixed with 454.113 g of hexamethylene diisocyanate, and reacted at 65±5°C for 1 h, then 84.5 g of bis(2-hydroxyethyl)dimethyl ammonium chloride was added and reacted for another 1 h, and the reaction was terminated when the -NCO content was 4.85 wt.%, to obtain the polyurethane prepolymer.

[0064] Example 1

[0065] The mildew-resistant and antibacterial sealant comprises the following raw materials in parts by weight:

[0066] Mildew-resistant and antibacterial modified composition 1: 45 parts;

[0067] Polyurethane prepolymer: 15 parts;

[0068] Nano-titanium dioxide: 39 parts;

[0069] γ-aminoethyl aminopropyl trimethoxysilane: 1 part;

[0070] Tetrabutyl titanate: 0.05 parts;

[0071] The preparation method of the mildew-resistant and antibacterial sealant comprises the following steps:

[0072] Mixing the mildew-resistant and antibacterial modified composition 1, the polyurethane prepolymer and the nano-titanium dioxide, vacuum degassing for 1 h under a pressure of ≤-0.093 MPa, then adding tetrabutyl titanate and γ-aminoethyl aminopropyl trimethoxysilane under nitrogen protection, and uniformly dispersing, to obtain the mildew-resistant and antibacterial sealant.

[0073] Example 2

[0074] The mildew-resistant and antibacterial sealant comprises the following raw materials in parts by weight:

[0075] Mildew-resistant and antibacterial modified composition 2: 55 parts;

[0076] Polyurethane prepolymer: 25 parts;

[0077] Fumed white carbon black: 15 parts;

[0078] gamma-aminopropyltrimethoxysilane: 5 parts;

[0079] tetrabutyl titanate: 0.15 parts;

[0080] The preparation method of the mildew-proof and antibacterial sealant is the same as that of Example 1.

[0081] Example 3

[0082] The mildew-proof and antibacterial sealant comprises the following raw materials in parts by weight:

[0083] mildew-proof and antibacterial modified composition 3: 52 parts;

[0084] polyurethane prepolymer: 22 parts;

[0085] fumed white carbon black: 23 parts;

[0086] gamma-isocyanatopropyltriethoxysilane: 3 parts;

[0087] tetrabutyl titanate: 0.1 parts;

[0088] The preparation method of the mildew-proof and antibacterial sealant is the same as that of Example 1.

[0089] Comparative Example 1

[0090] The difference from Example 3 is that:

[0091] The preparation method of the mildew-proof and antibacterial modified composition comprises the following steps:

[0092] S1, using propylene oxide instead of the epoxide in the high polyether polyol 3, to obtain a high polyether polyol with a number average molecular weight of 20000;

[0093] S2, mixing 2000g of the high polyether polyol obtained in step S1, 72g of acrylic acid and 2.074g of chlorophenol, and performing esterification reaction under the catalysis of 2g of p-toluenesulfonic acid at 180℃, and evaporating small molecular substances to control the mass of the fraction, to obtain an end double bond modified polymer;

[0094] S3, mixing 0.5mol of the end double bond modified polymer obtained in step S2, 3mol of N,N,N-trimethyl-(11-mercapto-undecyl) ammonium chloride, 2mol of 3-mercaptopropyltrimethoxysilane and 1200g of dimethyl carbonate in the presence of 0.03mol of benzoin dimethyl ether, and initiating the reaction by ultraviolet light irradiation at 35±15mW / cm 2 , until the infrared spectrometer cannot detect the signal of the carbon-carbon double bond peak at 1640-1660cm -1 , to obtain the mildew-proof and antibacterial modified composition.

[0095] Other than Example 3.

[0096] Comparative Example 2

[0097] The difference from Example 3 is that:

[0098] The preparation method of the polyurethane prepolymer comprises the following steps:

[0099] 931.5 g of glyceryl polyoxypropylene ether is mixed with 454.113 g of hexamethylene diisocyanate, and then reacted at 65±5℃ for 1 h, then 84.5 g of decanediol is added and reacted for 1 h, and the reaction is stopped when the -NCO content is 4.85wt.% to obtain the polyurethane prepolymer;

[0100] The glyceryl polyoxypropylene ether is prepared by polymerization of glycerol and propylene oxide, and the number average molecular weight is 1035.

[0101] Other than Example 3.

[0102] Comparative Example 3

[0103] The difference from Example 3 is that: equal weight of mildew-resistant and antibacterial modified composition 3 is used instead of polyurethane prepolymer, and other conditions are the same as Example 3.

[0104] The sealant prepared in Examples 1-3 and Comparative Examples 1-3 is tested for performance, and the test method is as follows:

[0105] Mildew resistance level: tested according to GB / T 1741-2020;

[0106] Water contact angle: tested according to GB / T 30693-2014;

[0107] Bacterial resistance rate: tested according to QB / T 2591-2003;

[0108] Long-term mildew resistance level (antibacterial performance): tested according to QB / T 2591-2003;

[0109] Adhesion to substrate: tested according to GB 16776-2005.

[0110] The test results are shown in Table 1.

[0111] Table 1 Performance test results

[0112]

[0113] From the test data in Table 1, it can be seen that the antibacterial property, long-term mildew resistance and adhesion to substrate of the sealant prepared in Examples 1-3 are better than those of the comparative examples.

[0114] In Comparative Example 1, the water contact angle of the sealant decreases due to the decrease of the content of the hydrophobic propyl group, which leads to the decrease of the mildew resistance grade after the sealant is placed outdoors for one month.

[0115] In Comparative Example 2, on the one hand, the decrease of the number of the antibacterial groups leads to the decrease of the antibacterial rate; on the other hand, the change of the hydrophobicity of the polyurethane prepolymer leads to the decrease of the water contact angle of the sealant, and the sealant also shows a decreasing trend of the mildew resistance grade after being placed outdoors for one month.

[0116] In Comparative Example 3, the content of the urethane groups and ester bond groups in the finished sealant decreases due to the non-use of the polyurethane prepolymer, which further leads to the decrease of the mechanical properties of the sealant and the decrease of the adhesion to the substrate.

Claims

1. A mildew-proof and antibacterial sealant, characterized by comprising: The raw materials include the following weight parts: Mold and bacteria resistant modified composition: 45-55 parts; Polyurethane prepolymer: 15-25 parts; Filler: 15-39 parts; Coupling agent: 1-5 parts; Organic titanate catalyst: 0.05-0.15 parts; The preparation method of the mold and bacteria resistant modified composition includes the following steps: S1, polymerizing a polyhydroxy compound with an epoxy pentane to obtain a high polyether polyol; S2, mixing the high polyether polyol obtained in step S1, a carboxyl-containing unsaturated monomer and a polymerization inhibitor, and performing esterification under the action of an acid catalyst to obtain an end double bond modified polymer; S3, mixing the end double bond modified polymer obtained in step S2, a bacteriostatic agent, a silane coupling agent and a solvent, and performing a reaction under the action of a photoinitiator through light irradiation to obtain the mold and bacteria resistant modified composition; The polyurethane prepolymer is prepared by reacting castor oil, isocyanate and a chain extender, and the chain extender is bis(2-hydroxyethyl)dimethylammonium chloride.

2. The mildew resistant antimicrobial sealant of claim 1, wherein In step S1, the polyhydroxy compound is polyglycerol-8 or polyglycerol-6, and the number average molecular weight of the high polyether polyol is 8000-20000.

3. The mildew resistant antimicrobial sealant of claim 1, wherein In step S2, the carboxyl-containing unsaturated monomer is acrylic acid, the molar ratio of the hydroxyl group in the high polyether polyol to the double bond in the carboxyl-containing unsaturated monomer is 1:(1-1.1), the polymerization inhibitor is chlorophenol, and the acid catalyst is p-toluenesulfonic acid.

4. The mildew resistant antimicrobial sealant of claim 1, wherein In step S3, the bacteriostatic agent is N,N,N-trimethyl-(11-mercapto-undecyl)ammonium chloride, the silane coupling agent is 3-mercaptopropyltrimethoxysilane, the solvent is dimethyl carbonate, and the photoinitiator is benzoin dimethyl ether.

5. The mildew resistant antimicrobial sealant of claim 4, wherein In step S3, the molar ratio of the bacteriostatic agent to the silane coupling agent is 3:(1.9-2), and the molar ratio of the double bond in the end double bond modified polymer to the total mercapto groups in the bacteriostatic agent and the silane coupling agent is 1:(1-1.1).

6. The mildew and bacteria resistant sealant of claim 1, wherein The preparation method of the polyurethane prepolymer includes the following steps: After mixing and reacting castor oil with isocyanate, a chain extender is added for further reaction to obtain a polyurethane prepolymer with a -NCO content of 4.7-4.9 wt.%; The isocyanate is hexamethylene diisocyanate.

7. The mildew and bacteria resistant sealant of claim 1, wherein The filler is fumed white carbon black or nano titanium dioxide.

8. The mildew and bacteria resistant sealant of claim 1, wherein The coupling agent is γ-aminopropyltrimethoxysilane or γ-isocyanate propyl triethoxysilane.

9. The mildew and bacteria resistant sealant of claim 1, wherein The organic titanate catalyst is tetrabutyl titanate.

10. A method of preparing the mold and mildew resistant antimicrobial sealant of any one of claims 1-9, characterized in that, The method includes the following steps: Mixing the mold and bacteria resistant modified composition, the polyurethane prepolymer and the filler and vacuum degassing, then adding the organic titanate catalyst and the coupling agent and uniformly dispersing to obtain the mold and bacteria resistant sealant.

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