Microporous low-density fireproof sealant as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of sealants, and particularly provides a microporous low-density fireproof sealant and a preparation method and application thereof.The microporous low-density fireproof sealant is prepared from, by weight, 80-100 parts of alpha, omega-dihydroxy polydimethylsiloxane, 25-35 parts of simethicone, 25-40 parts of a composite flame retardant, 10-20 parts of modified calcium carbonate and 15-30 parts of a cross-linking agent; 2-6 parts of a coupling agent and 0.1-0.5 part of a catalyst. The sealant disclosed by the invention has excellent flame retardance, relatively high cohesiveness, fire resistance, aging resistance, illumination resistance and corrosion resistance, does not contain asbestos, and has the characteristics of no toxicity, no halogen and low smoke.

Description

Technical Field

[0001] The invention belongs to the technical field of sealants, and in particular relates to a microporous low-density fireproof sealant and a preparation method and application thereof. Background Art

[0002] As a key material to ensure the sealing performance of marine engineering cables, their joints and terminals, the quality of sealants is directly related to the safe and stable operation of the entire system. With the advancement of design and construction technology in the field of ships, the increase in the types of ships, and the expansion of hulls, the use of ship fireproof and thermal insulation materials has become increasingly important. Silicone elastic material is one of the common main materials for sealants. Its classification is mainly based on different packaging methods and is divided into two types: single-component and two-component. Single-component silicone sealants can spontaneously undergo cross-linking and curing reactions at room temperature through contact with moisture in the air. Two-component silicone sealants are composed of two independent components A and B. Curing cannot be achieved by using either component alone. When the two components are mixed together, they will quickly undergo a cross-linking reaction and thus cure into shape.

[0003] Sealant is known for its excellent stability and aging resistance. However, silicone-based sealants are inherently flammable and can cause serious damage in the event of a fire. Therefore, during the preparation process, it is usually necessary to add appropriate flame retardants or other reinforcing materials to improve their flame retardancy and adhesion.

[0004] Chinese patent CN 118599475 A discloses a silicone fireproof sealant and a preparation method thereof. The sealant comprises the following raw materials in parts by weight: 100-200 parts of base glue, 30-60 parts of flame retardant, 30-60 parts of smoke suppressant, 60-100 parts of filler, 10-20 parts of crosslinking agent, 0.01-1 parts of catalyst, and 0.5-5 parts of tackifier. The sealant provided by this invention has the characteristics of low smoke, non-toxicity and fire prevention. However, the flame retardant is aluminum hydroxide and / or magnesium hydroxide. The hydroxide has poor compatibility with the polymer substrate and is prone to agglomeration after long-term storage, which leads to uneven flame retardant effect and affects the overall flame retardancy of the sealant.

[0005] Therefore, there is an urgent need for a microporous, low-density sealant that has excellent flame retardancy and high adhesion. Summary of the invention

[0006] In view of the existing technical problems, the purpose of the present invention is to provide a microporous low-density fireproof sealant and its preparation method and application. The sealant of the present invention has excellent flame retardancy, high adhesion, fire resistance, aging resistance, light resistance, corrosion resistance, does not contain asbestos, and has the characteristics of non-toxicity, halogen-free and low smoke.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] On the one hand, the present invention provides a microporous low-density fireproof sealant, which comprises the following raw materials in parts by weight: 80-100 parts of α, ω-dihydroxy polydimethylsiloxane, 25-35 parts of dimethyl silicone oil, 25-40 parts of composite flame retardant, 10-20 parts of modified calcium carbonate, 15-30 parts of cross-linking agent, 2-6 parts of coupling agent and 0.1-0.5 parts of catalyst.

[0009] The reaction mechanism and effects of the present invention are as follows:

[0010] 1. In recent years, the public's attention to safety and environmental protection has been increasing, which has led to widespread attention to halogen-free flame retardant technology in sealants. Traditional halogen-free flame retardants, such as magnesium hydroxide and aluminum hydroxide, can enhance the flame retardant effect of polymer materials, but because they need to be added in large quantities and have poor compatibility with polymer substrates, they often significantly weaken the mechanical properties of the materials, resulting in a significant decrease in the overall performance of the materials. Intumescent flame retardants are halogen-free flame retardants with excellent flame retardant properties. They have the characteristics of low smoke, low toxicity, and high fire retardant efficiency during the flame retardant process. Among the current intumescent flame retardants, ammonium polyphosphate / melamine / pentaerythritol (acid source / gas source / carbon source) is still the mainstream choice, but ammonium polyphosphate has problems with poor hygroscopicity, processing performance and thermal stability, and pentaerythritol has the disadvantages of high water solubility and poor thermal stability, which all affect the actual application of intumescent flame retardants.

[0011] The present invention uses phytic acid, N-formamidopiperidine and 2,3-dihydroxypropyl calcium phosphate to form a new type of intumescent flame retardant, so that the flame retardant efficiency is good. Intumescent flame retardants produce chemical reaction expansion under high temperature conditions, and a large number of fine micropores are generated inside the product, which reduces the overall thermal conductivity, delays the transmission of heat, and also plays a vital role in the fireproofing and heat insulation of the entire system. The applicant uses phytic acid to replace ammonium polyphosphate, which can play the role of high phosphorus content in phytic acid, promote 2,3-dihydroxypropyl calcium phosphate to form carbon, and form a porous low-density intumescent carbon layer, further improving the flame retardant effect; at the same time, 2,3-dihydroxypropyl calcium phosphate is used as a carbon source to effectively improve the foaming performance, so that more and more fine micropores are generated inside, and the porosity is improved. Further, the applicant adds a nonionic surfactant during the preparation process, which helps to evenly disperse the ingredients, improve the uniformity of the final product, and then improve the flame retardancy. In addition, the applicant unexpectedly found that the addition of N-formamidopiperidine can reduce the amount of 2,3-dihydroxypropyl calcium phosphate added, saving the amount of raw materials.

[0012] 2. Calcium carbonate has good mechanical properties and thermal insulation properties, and can be used as a reinforcing material to improve the overall performance of sealants. However, the surface of calcium carbonate is hydrophilic due to the presence of hydroxyl groups, and its uniform dispersion in the lipophilic silicone matrix is ​​poor.

[0013] The present invention first modifies calcium carbonate with sodium myristic acid, which can be firmly bonded to the surface of calcium carbonate to produce an active coating layer, increase the distance between particles, reduce the interaction of van der Waals forces, make the dispersion system more stable, reduce the agglomeration phenomenon between calcium carbonate particles, and then convert the surface of calcium carbonate from hydrophilic to oleophobic, thereby improving its compatibility with silicone. Then, the applicant further modifies it with cocamidopropyl trimethyl ammonium chloride and ultraviolet absorber, effectively ensuring the mechanical properties, aging resistance, corrosion resistance and adhesion of the product. The positive charge carried by cocamidopropyltrimethylammonium chloride will bond with the negative charge on the sodium myristate on the surface of calcium carbonate through mutual attraction of heterogeneous charges, which not only reduces the surface energy of calcium carbonate particles, improves dispersibility, and improves the interfacial bonding force between calcium carbonate and the silicone matrix, thereby enhancing the adhesion of the sealant, improving the tensile elongation properties of the sealant, but also makes the sealant have good antibacterial, anti-corrosion and anti-fouling properties; at the same time, the addition of ultraviolet absorbers can significantly enhance the ultraviolet absorption capacity of calcium carbonate, thereby improving the aging resistance and light resistance of the sealant, allowing the sealant to maintain stability for a longer time in harsh environments.

[0014] In some embodiments, the viscosity of the α,ω-dihydroxy polydimethylsiloxane at 25° C. ranges from 10,000 to 80,000 cps.

[0015] In some embodiments, the composite flame retardant is a combination of a silicone resin flame retardant and an intumescent flame retardant.

[0016] Preferably, the mass ratio of the silicone resin flame retardant to the intumescent flame retardant is 1:(0.8-1.2).

[0017] Further preferably, the silicone resin flame retardant is selected from any one of SFR-100 flame retardant, DCRM flame retardant and X-40-9243 flame retardant.

[0018] In some embodiments, the method for preparing the intumescent flame retardant comprises the following steps:

[0019] The acid source, gas source and carbon source are mixed and added into a reaction kettle, a nonionic surfactant is added, the mixture is heated to 65-78° C., high-speed dispersed at 6000-9000 r / min for 30-60 min, dried and crushed to obtain an intumescent flame retardant.

[0020] In some embodiments, the acid source, gas source and carbon source are phytic acid, N-formamidopiperidine and 2,3-dihydroxypropyl calcium phosphate, respectively, and the mass ratio of the three is (3.2-3.8):1:(0.7-0.9).

[0021] In some embodiments, the nonionic surfactant accounts for 5-7% of the total mass of the acid source, the gas source and the carbon source.

[0022] Preferably, the nonionic surfactant is alkylphenol polyoxyethylene ether TX-10.

[0023] In some embodiments, the method for preparing the modified calcium carbonate comprises the following steps:

[0024] H1. Mix calcium carbonate and anhydrous ethanol, disperse by ultrasonication, add sodium myristic acid, heat to 60-80°C for reaction for 50-70 minutes, cool, wash, and dry to obtain a product;

[0025] H2. The product obtained in step H1 is mixed with anhydrous ethanol and ultrasonically dispersed to obtain a dispersion having a mass fraction of 10-15%;

[0026] H3. Add the dispersion obtained in step H2 to a reactor, heat to 70-80° C., add cocamidopropyl trimethylammonium chloride and a UV absorber, perform mechanical stirring, cool, and dry to obtain modified calcium carbonate.

[0027] In some embodiments, the mass ratio of calcium carbonate to sodium myristate in step H1 is 10:

[0028] (0.4-0.6).

[0029] In some embodiments, the mass ratio of the product, cocoamidopropyltrimethylammonium chloride, and ultraviolet absorber in the dispersion in step H3 is 10:(0.4-0.7):(0.2-0.4).

[0030] Preferably, the calcium carbonate is nano calcium carbonate with an average particle size of 60-100 nm.

[0031] In some embodiments, the crosslinking agent is any one or more of methyltributylacetoximosilane, vinyltributylacetoximosilane and tetrabutylketoximesilane.

[0032] In some embodiments, the coupling agent is any one or more of methyltriethoxysilane, di-tert-butoxydiacetoxysilane, γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane.

[0033] In some embodiments, the catalyst is any one or more of dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate and stannous octoate.

[0034] The present invention also provides a method for preparing a microporous low-density fireproof sealant, comprising the following steps:

[0035] Q1. Add α,ω-dihydroxy polydimethylsiloxane, dimethyl silicone oil and composite flame retardant into a reaction kettle and mix, then add modified calcium carbonate and mix, vacuum degassing for 20-30 minutes, the vacuum degree is -0.08~-0.1MPa, and obtain the base material;

[0036] Q2. Mix the crosslinking agent and coupling agent and add them to the base material obtained in step Q1, mix and stir, then add the catalyst and stir to obtain a sealant.

[0037] The third aspect of the present invention provides an application of a microporous low-density fireproof sealant, which is applied to a light-duty cable penetration fireproof sealing device.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. The sealant of the present invention has excellent flame retardancy, high adhesion, fire resistance, aging resistance, light resistance, corrosion resistance, does not contain asbestos, and has the characteristics of being non-toxic, halogen-free, and low in smoke.

[0040] 2. The present invention uses phytic acid, N-formamidopiperidine and 2,3-dihydroxypropyl calcium phosphate to form a new type of intumescent flame retardant, which has excellent flame retardant efficiency. The applicant uses phytic acid to replace ammonium polyphosphate, which can play the role of high phosphorus content in phytic acid, promote 2,3-dihydroxypropyl calcium phosphate to form carbon, and form a porous low-density intumescent carbon layer, further improving the flame retardant effect; at the same time, the addition of 2,3-dihydroxypropyl calcium phosphate improves the porosity; in addition, the addition of nonionic surfactants during the preparation process helps to evenly disperse the ingredients, thereby improving flame retardancy.

[0041] 3. The present invention first modifies calcium carbonate with sodium myristic acid, and sodium myristic acid improves the compatibility of calcium carbonate with organosilicon; then, the applicant further modifies it with cocamidopropyl trimethyl ammonium chloride and ultraviolet absorber, effectively ensuring the mechanical properties, aging resistance, corrosion resistance and adhesion of the product. Cocoamidopropyl trimethyl ammonium chloride not only reduces the surface energy, improves the interfacial bonding force between calcium carbonate and the organosilicon matrix, and then enhances the adhesion and tensile elongation properties of the sealant, but also enables the sealant to have good antibacterial, corrosion resistance and antifouling properties; at the same time, the addition of ultraviolet absorber enhances the ultraviolet absorption capacity of calcium carbonate, and then improves the aging resistance and light resistance of the sealant. DETAILED DESCRIPTION

[0042] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, rather than to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0043] According to the ratios of the raw materials and the preparation methods specified in the following examples and comparative examples, various sealants were prepared.

[0044] In order to facilitate those skilled in the art to implement the present invention, some raw material manufacturers of the embodiments and comparative examples are described as follows:

[0045] α,ω-dihydroxypolydimethylsiloxane: purchased from Hubei Chengfeng Chemical Co., Ltd., with a viscosity of 50,000 cps at 25°C;

[0046] Dimethyl silicone oil: purchased from Jinan Silicon Port Chemical Co., Ltd., with a viscosity of 500 cps at 25°C;

[0047] Ammonium polyphosphate: purchased from Henan Mingzhixin Chemical Products Co., Ltd.;

[0048] Alkylphenol polyoxyethylene ether TX-10: purchased from Shandong Jinli Chemical Co., Ltd.;

[0049] Nano calcium carbonate: 80nm;

[0050] Other raw materials are not specially specified and can be purchased from the market.

[0051] Preparation Example 1

[0052] The preparation method of intumescent flame retardant A comprises the following steps:

[0053] 35 g of phytic acid, 10 g of N-formamidopiperidine and 8 g of 2,3-dihydroxypropyl calcium phosphate were mixed and added to a reactor, 3.18 g of alkylphenol polyoxyethylene ether TX-10 was added, heated to 75°C, high-speed dispersed at 8000 r / min for 45 min, dried at 85°C for 24 h, and crushed to obtain intumescent flame retardant A.

[0054] Preparation Example 2

[0055] The preparation method of the intumescent flame retardant B comprises the following steps:

[0056] 29 g of phytic acid, 10 g of N-formamidopiperidine and 8 g of 2,3-dihydroxypropyl calcium phosphate were mixed and added to a reactor, 2.82 g of alkylphenol polyoxyethylene ether TX-10 was added, the mixture was heated to 75°C, high-speed dispersed at 8000 r / min for 45 min, dried at 85°C for 24 h, and crushed to obtain intumescent flame retardant B.

[0057] Preparation Example 3

[0058] The preparation method of the intumescent flame retardant C comprises the following steps:

[0059] 35 g of phytic acid, 10 g of N-formamidopiperidine and 6 g of 2,3-dihydroxypropyl calcium phosphate were mixed and added to a reactor, 3.06 g of alkylphenol polyoxyethylene ether TX-10 was added, the mixture was heated to 75° C., high-speed dispersed at 8000 r / min for 45 min, dried at 85° C. for 24 h, and crushed to obtain an intumescent flame retardant C.

[0060] Preparation Example 4

[0061] The preparation method of the intumescent flame retardant D comprises the following steps:

[0062] 35 g of phytic acid, 10 g of N-formamidopiperidine and 8 g of 2,3-dihydroxypropyl calcium phosphate were mixed and added to a reactor, and 2.12 g of alkylphenol polyoxyethylene ether TX-10 was added. The mixture was heated to 75° C., dispersed at a high speed of 8000 r / min for 45 min, dried at 85° C. for 24 h, and crushed to obtain an intumescent flame retardant D.

[0063] Preparation Example 5

[0064] The preparation method of the intumescent flame retardant E comprises the following steps:

[0065] 35 g of ammonium polyphosphate, 10 g of melamine and 8 g of pentaerythritol were mixed and added to a reactor, and 3.18 g of alkylphenol polyoxyethylene ether TX-10 was added. The mixture was heated to 75° C., dispersed at a high speed of 8000 r / min for 45 min, dried at 85° C. for 24 h, and crushed to obtain an intumescent flame retardant E.

[0066] Preparation Example 6

[0067] The preparation method of modified calcium carbonate A comprises the following steps:

[0068] H1. Mix 200g of nano calcium carbonate and 1200mL of anhydrous ethanol, disperse by ultrasonic for 40min, add 10g of sodium myristic acid, heat to 70℃ for 60min, cool to room temperature, wash with anhydrous ethanol 3 times, and dry at 85℃ for 6h to obtain the product;

[0069] H2. 150 g of the product obtained in step H1 and 1150 mL of anhydrous ethanol were mixed and ultrasonically dispersed for 45 min to obtain a dispersion;

[0070] H3. The dispersion obtained in step H2 was added to a reactor, heated to 75°C, 8.25 g of cocoamidopropyl trimethylammonium chloride and 4.5 g of ultraviolet absorber UV-1164 were added, mechanically stirred for 80 min, cooled to room temperature, and dried at 85°C to constant weight to obtain modified calcium carbonate A.

[0071] Preparation Example 7

[0072] The preparation method of modified calcium carbonate B is the same as that of Preparation Example 6, except that the amount of sodium myristic acid added in step H1 is 7.2 g.

[0073] Preparation Example 8

[0074] The preparation method of modified calcium carbonate C is the same as that of Preparation Example 6, except that the amount of cocoamidopropyltrimethylammonium chloride added in step H2 is 5.7 g.

[0075] Example 1

[0076] A microporous low-density fireproof sealant, which comprises the following raw materials by weight: 90 parts of α,ω-dihydroxy polydimethylsiloxane, 30 parts of dimethyl silicone oil, 32.5 parts of composite flame retardant, 15 parts of modified calcium carbonate A, 22.5 parts of vinyl tributylidene oxime silane, 4 parts of γ-aminopropyl trimethoxy silane, and 0.3 parts of dibutyltin dilaurate; wherein,

[0077] The composite flame retardant is SFR-100 flame retardant and intumescent flame retardant A, and the mass ratio of the two is 1:1.

[0078] The preparation method of the sealant of this embodiment comprises the following steps:

[0079] Q1. α,ω-dihydroxy polydimethylsiloxane, dimethyl silicone oil and composite flame retardant were added to the reaction kettle and mixed, and then modified calcium carbonate A was added and mixed, stirred for 60 minutes, and vacuum degassed for 25 minutes, with a vacuum degree of -0.09MPa, to obtain a base material;

[0080] Q2. Vinyl trisbutyl ketoxime silane and γ-aminopropyl trimethoxy silane were mixed and added to the base material obtained in step Q1, and stirred for 30 minutes. Then, dibutyl tin dilaurate was added and stirred for 60 minutes to obtain a sealant.

[0081] Example 2

[0082] A microporous low-density fireproof sealant, which comprises the following raw materials by weight: 80 parts of α,ω-dihydroxy polydimethylsiloxane, 25 parts of dimethyl silicone oil, 25 parts of composite flame retardant, 10 parts of modified calcium carbonate A, 15 parts of vinyl tributylidene oxime silane, 2 parts of γ-aminopropyl trimethoxy silane, and 0.1 parts of dibutyltin dilaurate; wherein,

[0083] The composite flame retardant is SFR-100 flame retardant and intumescent flame retardant A, and the mass ratio of the two is 1:0.8.

[0084] The preparation method of the sealant of this embodiment comprises the following steps:

[0085] Q1. α,ω-dihydroxy polydimethylsiloxane, dimethyl silicone oil and composite flame retardant were added to the reaction kettle and mixed, and then modified calcium carbonate A was added and mixed, stirred for 60 minutes, and vacuum degassed for 20 minutes with a vacuum degree of -0.08MPa to obtain a base material;

[0086] Q2. Vinyl trisbutyl ketoxime silane and γ-aminopropyl trimethoxy silane were mixed and added to the base material obtained in step Q1, and stirred for 30 minutes. Then, dibutyl tin dilaurate was added and stirred for 60 minutes to obtain a sealant.

[0087] Example 3

[0088] A microporous low-density fireproof sealant, which comprises the following raw materials by weight: 100 parts of α,ω-dihydroxy polydimethylsiloxane, 35 parts of dimethyl silicone oil, 40 parts of composite flame retardant, 20 parts of modified calcium carbonate A, 30 parts of vinyl tributylidene oxime silane, 6 parts of γ-aminopropyl trimethoxy silane, and 0.5 parts of dibutyltin dilaurate; wherein,

[0089] The composite flame retardant is SFR-100 flame retardant and intumescent flame retardant A, and the mass ratio of the two is 1:1.2.

[0090] The preparation method of the sealant of this embodiment comprises the following steps:

[0091] Q1. Add α,ω-dihydroxy polydimethylsiloxane, dimethyl silicone oil and composite flame retardant into a reactor and mix, then add modified calcium carbonate A and mix, stir for 60 minutes, vacuum degassing for 30 minutes, the vacuum degree is -0.1MPa, and obtain the base material;

[0092] Q2. Vinyl trisbutyl ketoxime silane and γ-aminopropyl trimethoxy silane were mixed and added to the base material obtained in step Q1, and stirred for 30 minutes. Then, dibutyl tin dilaurate was added and stirred for 60 minutes to obtain a sealant.

[0093] Example 4

[0094] A microporous low-density fireproof sealant and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of intumescent flame retardant B is used to replace intumescent flame retardant A.

[0095] Example 5

[0096] A microporous low-density fireproof sealant and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of intumescent flame retardant C is used to replace intumescent flame retardant A.

[0097] Example 6

[0098] A microporous low-density fireproof sealant and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of intumescent flame retardant D is used to replace intumescent flame retardant A.

[0099] Example 7

[0100] A microporous low-density fireproof sealant and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of intumescent flame retardant E is used to replace intumescent flame retardant A.

[0101] Example 8

[0102] A microporous low-density fireproof sealant and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified calcium carbonate B is used to replace modified calcium carbonate A.

[0103] Example 9

[0104] A microporous low-density fireproof sealant and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified calcium carbonate C is used to replace modified calcium carbonate A.

[0105] Comparative Example 1

[0106] A microporous low-density fireproof sealant and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of commercially available nano calcium carbonate is used to replace modified calcium carbonate A.

[0107] Effect evaluation:

[0108] The sealants prepared in the above-mentioned Examples 1-9 and Comparative Example 1 were tested and analyzed, and the specific results are shown in Table 1.

[0109] Performance Test:

[0110] The performance test was carried out after curing for 14 days under standard test conditions of temperature (23±2)°C and relative humidity (50±5)%.

[0111] (1) Corrosion resistance: The salt spray corrosion resistance of the sealant was tested according to GB / T 1771-2007. The sample preparation and experimental process of the salt spray test were as follows: the test samples were all 150 mm × 100 mm × 1 mm steel plates. The surface was degreased with solvent and polished with sandpaper. The sealant was applied to the steel plate and the thickness controller was used to evenly apply the sealant on the front, back and side surfaces of the steel plate so that the sealant completely covered the steel plate. The thickness of the sealant was controlled at (150 ± 10) μm.

[0112] The sealants prepared in Examples 1-3 were subjected to a salt spray corrosion test, and it was found that the surfaces of the steel plates were not corroded and were intact without any rust.

[0113] (2) Flame retardancy: Oxygen index test is carried out. The higher the oxygen index, the better the flame retardant effect. The test is carried out according to the method in GB / T10707-2008 "Determination of combustion performance of rubber". The sample size is 80mm×10mm×4mm;

[0114] (3) Tensile bond strength: The test is based on GB16776-2005 "Silicone structural sealant for construction".

[0115] Table 1 Performance test

[0116] Serial number Oxygen index / % Tensile bond strength / MPa Example 1 58 1.97 Example 2 55 1.75 Example 3 59 1.86 Example 4 49 1.96 Example 5 48 1.97 Example 6 53 1.95 Example 7 42 1.92 Example 8 56 1.54 Example 9 56 1.52 Comparative Example 1 54 1.29

[0117] It can be seen from the results in Table 1 that the sealants prepared in Examples 1-3 have good flame retardancy and excellent tensile bonding strength.

[0118] Compared with Example 1, when preparing the intumescent flame retardant, Example 4-5 changed the mass ratio of the acid source, gas source and carbon source (phytic acid, N-formamidopiperidine and 2,3-dihydroxypropyl calcium phosphate), and the low-density intumescent carbon layer formed was reduced, which made the flame retardancy worse. Example 6 changed the amount of non-ionic surfactant added, and the uniform dispersion of the components was poor, which reduced the flame retardancy of the intumescent flame retardant. Example 7 used conventional acid source, gas source and carbon source (ammonium polyphosphate, melamine and pentaerythritol), with poor thermal stability and greatly reduced flame retardancy; and the tensile bonding strength of the sealant prepared by Example 4-7 showed almost no obvious change.

[0119] Compared with Example 1, when preparing modified calcium carbonate in Examples 8-9, Example 8 changed the mass ratio of calcium carbonate and sodium myristic acid, and the calcium carbonate dispersion system was unstable. Example 9 changed the mass ratio of the product, cocoamidopropyl trimethyl ammonium chloride, and ultraviolet absorber in the dispersion liquid, so that the surface energy of the calcium carbonate particles was high. Compared with Example 1, Comparative Example 1 used an equal amount of commercially available nano calcium carbonate to replace modified calcium carbonate A, which made its dispersibility and compatibility worse, both of which would affect the tensile bonding strength of the sealant and also had a certain degree of influence on its flame retardancy.

[0120] The above is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present application. Although the present application is disclosed as above in the preferred embodiment, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution.

Claims

1. A microporous low-density fireproof sealant, characterized in that: The sealant comprises the following raw materials by weight: 80-100 parts of α,ω-dihydroxypolydimethylsiloxane, 25-35 parts of dimethyl silicone oil, 25-40 parts of composite flame retardant, 10-20 parts of modified calcium carbonate, 15-30 parts of crosslinking agent, 2-6 parts of coupling agent and 0.1-0.5 parts of catalyst.

2. A microporous low-density fireproof sealant according to claim 1, characterized in that: The composite flame retardant is a composition of an organic silicon resin flame retardant and an intumescent flame retardant.

3. A microporous low-density fireproof sealant according to claim 2, characterized in that: The preparation method of the intumescent flame retardant comprises the following steps: The acid source, gas source and carbon source are mixed and added into a reaction kettle, a nonionic surfactant is added, the mixture is heated to 65-78° C., high-speed dispersed at 6000-9000 r / min for 30-60 min, dried and crushed to obtain an intumescent flame retardant.

4. A microporous low-density fireproof sealant according to claim 3, characterized in that: The acid source, gas source and carbon source are phytic acid, N-formamidopiperidine and 2,3-dihydroxypropyl calcium phosphate in sequence, and the mass ratio of the three is (3.2-3.8):1:(0.7-0.9).

5. A microporous low-density fireproof sealant according to claim 3, characterized in that: The nonionic surfactant accounts for 5-7% of the total mass of the acid source, the gas source and the carbon source.

6. A microporous low-density fireproof sealant according to claim 1, characterized in that: The preparation method of the modified calcium carbonate comprises the following steps: H1. Mix calcium carbonate and anhydrous ethanol, disperse by ultrasonication, add sodium myristic acid, heat to 60-80°C for reaction for 50-70 minutes, cool, wash, and dry to obtain a product; H2. The product obtained in step H1 is mixed with anhydrous ethanol and ultrasonically dispersed to obtain a dispersion having a mass fraction of 10-15%; H3. Add the dispersion obtained in step H2 to a reactor, heat to 70-80° C., add cocamidopropyl trimethylammonium chloride and a UV absorber, perform mechanical stirring, cool, and dry to obtain modified calcium carbonate.

7. A microporous low-density fireproof sealant according to claim 6, characterized in that: The mass ratio of calcium carbonate to sodium myristic acid in step H1 is 10:(0.4-0.6).

8. A microporous low-density fireproof sealant according to claim 6, characterized in that: The mass ratio of the product, cocoamidopropyltrimethylammonium chloride and ultraviolet absorber in the dispersion in step H3 is 10:(0.4-0.7):(0.2-0.4).

9. A method for preparing the microporous low-density fireproof sealant according to any one of claims 1 to 8, characterized in that: The following steps are included: Q1. Add α,ω-dihydroxy polydimethylsiloxane, dimethyl silicone oil and composite flame retardant into a reaction kettle and mix, then add modified calcium carbonate and mix, vacuum degassing for 20-30 minutes, the vacuum degree is -0.08~-0.1MPa, and obtain the base material; Q2. Mix the crosslinking agent and coupling agent and add them to the base material obtained in step Q1, mix and stir, then add the catalyst and stir to obtain a sealant.

10. An application of the microporous low-density fireproof sealant according to any one of claims 1 to 8, characterized in that: Used in light cable penetration fire resistant sealing devices.