Phosphorus-tin-based flame retardant synergistic flame-retardant epoxy resin composition and preparation method thereof

Abstract

The invention discloses a phosphorus-tin-based flame retardant synergistic flame-retardant epoxy resin composition and a preparation method thereof, and belongs to the technical field of high polymer material modification and flame retardance. The preparation process of the flame-retardant epoxy resin composition comprises the following steps: respectively adding the phosphorus-based flame retardant, the tin-based flame retardant and the curing agent into the epoxy resin, uniformly mixing, pouring into a mold, and curing to obtain the flame-retardant epoxy resin composition. The phosphorus-based flame retardant and tin-based flame retardant synergistic flame-retardant epoxy resin composition has the advantages of good flame retardance, smoke suppression and thermal stability, low carbon, environmental protection and the like. The flame-retardant system overcomes the defect that toxic smoke and corrosive gas can be generated in the combustion process of traditional halogen-series flame retardants, antimony trioxide flame retardants and the like, and becomes one of environment-friendly flame retardants which reduce halogen and replace antimony trioxide.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material modification and flame retardancy, and relates to a phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition and a preparation method thereof. Background Art

[0002] Epoxy resin (EP), a representative of advanced resin-based materials, is a high-molecular-weight polymer, referring to a class of polymers containing two or more epoxy groups. Due to its unique physical and mechanical properties, corrosion resistance, good thermal stability, and ease of processing, it is widely used in various fields of life, including chemical protection, electronics, and machinery manufacturing. However, epoxy resin is a flammable material with a low limiting oxygen index of only 19.5. Therefore, untreated EP is highly flammable, releasing large amounts of black smoke during production, posing a serious threat to human health and safety.

[0003] As global flame retardant regulations and industry standards continue to improve, the use of flame retardants must not only consider reducing fire risks but also their impact on the ecological environment. Traditional flame retardants, such as halogen-based and antimony trioxide, produce toxic smoke and corrosive gases during combustion, which is inconsistent with current environmental and safety requirements. Therefore, finding environmentally friendly flame retardants is crucial to the development of the ecological environment. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention aims to provide a phosphorus-tin-based flame retardant synergistic flame-retardant epoxy resin composition and a preparation method thereof. By optimizing the raw material ratio, etc., the prepared flame-retardant epoxy resin composition has the advantages of good flame retardant effect, good heat resistance and stability, low toxicity and environmental protection.

[0005] In order to achieve the above technical objectives, the present invention is implemented through the following technical solutions:

[0006] A phosphorus-tin-based flame retardant synergistic flame-retardant epoxy resin composition, comprising the following raw materials in parts by mass:

[0007] Epoxy resin: 100 parts;

[0008] Phosphorus flame retardant: 10-25 parts;

[0009] Tin-based flame retardant: 5-20 parts;

[0010] Curing agent: 10-15 parts.

[0011] Preferably, the phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition comprises the following raw materials in parts by mass:

[0012] Epoxy resin: 100 parts;

[0013] Phosphorus flame retardant: 20 parts;

[0014] Tin-based flame retardant: 15 parts;

[0015] Curing agent: 12 parts.

[0016] Preferably, the method for preparing the phosphorus-based flame retardant comprises the following steps:

[0017] (1) Surface modification of nano-SiO2

[0018] Disperse 5-8 parts of nano-SiO2 in 30-40 parts of water, add 1-3 parts of 3-aminopropyltrimethoxysilane, and ultrasonicate for 27-35 minutes at a power of 150-350W. Then adjust the pH to 4-5, and stir the reaction at 72-78°C for 1.8-2.1 hours to obtain modified nano-SiO2.

[0019] (2) Activation of bio-based carbon sources

[0020] Mix 12-18 parts of starch with 5-8 parts of triethanolamine, and treat at a microwave power of 350-550W for 4-12 minutes to prepare activated starch;

[0021] (3) Phosphorus-nitrogen-silicon synergistic reaction

[0022] Add 20-30 parts of ammonium polyphosphate, 10-15 parts of pentaerythritol, and 8-12 parts of melamine to a reactor, heat to 123-135°C, and stir for 25-33 minutes; add modified nano-SiO2 and activated starch, and continue stirring for 0.8-1.2 hours; then add 0.5-2 parts of lecithin, adjust the pH to 6.5-7, raise the reaction temperature to 152-161°C, and maintain for 1.7-2.3 hours to obtain a reaction product;

[0023] (4) Nanoemulsion preparation and drying

[0024] The reaction product is cooled to 64-72° C., 10-20 parts of water are added, and high-speed shear dispersion is performed at 11000-14000 rpm for 13-16 minutes to form a nanoemulsion; and then dried at a vacuum degree of -0.08 to -0.09 MPa and a temperature of 52-60° C. for 8-12 hours to obtain a phosphorus-based flame retardant.

[0025] Preferably, the preparation method of the tin-based flame retardant comprises the following steps:

[0026] 1) Preparation of mixed metal salt solution

[0027] Dissolve 10-15 parts of zinc acetate, 3-5 parts of aluminum nitrate, and 2-4 parts of magnesium nitrate, respectively, in 80-100 parts of water, and stir at 35-42° C. for 21-28 minutes until completely dissolved to prepare a mixed metal salt solution;

[0028] 2) Add the reaction solution dropwise and stir

[0029] Solution A was first added dropwise to the mixed metal salt solution prepared in step 1), and after stirring for 10-15 minutes, solution B was then added dropwise at a rate of 1-2 drops / second. The pH was adjusted to 8.2-9 with aqueous ammonia. After solution B was added dropwise, 2-4 parts of a 5-10% boric acid solution was added, and stirring was continued for 27-32 minutes. The mixture was then heated to 43-48°C and reacted for 2-3 hours to obtain a mixed solution.

[0030] 3) Hydrothermal reaction

[0031] Transfer the mixed solution obtained in step 2) to a hydrothermal reactor and react at 200-240°C for 12-36 hours;

[0032] 4) Centrifugal washing and drying

[0033] After the reaction is completed, the hydrothermal autoclave is cooled to room temperature, the reaction solution is taken out for centrifugal separation, the precipitate is collected, and the precipitate is washed 3-4 times with water and anhydrous ethanol respectively, and then the precipitate is placed in a vacuum drying oven and dried at 85-102°C for 8-11 hours;

[0034] 5) Surface modification

[0035] The dried precipitate is placed in a mixer, and then 1-3 parts of silane coupling agent are diluted with 5-10 parts of anhydrous ethanol, and then dripped into the precipitate in the mixer, and stirred while dripping at a speed of 900-1000 rpm. After dripping, the speed is increased to 1200-1500 rpm, and stirred at a temperature of 62-70°C for 2-2.5 hours to obtain a tin-based flame retardant.

[0036] Preferably, the liquid A in step 2) is obtained by dissolving 12-18 parts of sodium stannate in 30-40 parts of water and stirring until completely dissolved.

[0037] Preferably, the liquid B in step 2) is obtained by dissolving 5-8 parts of ethyl orthosilicate in 10-15 parts of anhydrous ethanol and stirring to form a homogeneous solution.

[0038] Preferably, in step 5), the mass ratio of the alkane coupling agent to anhydrous ethanol is 1:3-5.

[0039] Preferably, the curing agent includes one or more of an amine curing agent, an acid anhydride curing agent, and a polyamide curing agent.

[0040] The present invention also provides a method for preparing a phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition, comprising the following steps: weighing an epoxy resin, a phosphorus-based flame retardant, a tin-based flame retardant, and a synergistic flame retardant compounded with a curing agent, adding the weighed components into a blender and mixing them evenly; then pouring the components into a preheated mold for curing; and demolding the components to obtain the phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition.

[0041] Preferably, the curing temperature in the mold is 60-150°C.

[0042] Technical principle:

[0043] 1. Analysis of the role of raw materials

[0044] (1) Epoxy resin (100 parts): As the matrix material of the composition, it provides basic structural support and mechanical properties for the entire system. Epoxy resin has excellent adhesion, chemical stability, and good processing properties. It can be evenly mixed with various additives. After curing, it forms a hard, wear-resistant, and insulating three-dimensional network structure. It is a key carrier for other functional components to achieve flame retardant effects. It is widely used in many fields such as electronics, aerospace, and other scenarios with stringent requirements on material mechanical properties.

[0045] (2) Phosphorus flame retardant (10-25 parts):

[0046] During heating, the phosphorus-based flame retardant of this invention exerts multiple flame-retardant mechanisms. Firstly, it forms a phosphorus-rich charcoal layer on the surface of the material. This charcoal layer acts as a heat shield, effectively blocking heat transfer to the internal material and slowing the thermal decomposition rate of the polymer. Secondly, the phosphoric acid and other substances produced by the decomposition of the phosphorus compound have a strong dehydrating effect, promoting the dehydration and carbonization of the epoxy resin, further enhancing the stability of the charcoal layer, suppressing the generation of combustible gases, and significantly reducing the flammability of the epoxy resin composition at the condensed phase level.

[0047] (3) Tin-based flame retardant (5-20 parts):

[0048] When exposed to high temperatures, the tin-based flame retardant of this invention decomposes to produce volatile tin compounds. These compounds can capture free radicals generated during combustion, such as hydrogen and hydroxyl radicals, interrupting the combustion chain reaction and preventing the continued spread of flames. Furthermore, when combined with phosphorus-based flame retardants, this compound can compensate for the relative shortcomings of phosphorus-based flame retardants in terms of gas-phase flame retardancy, thus improving the overall flame retardant system.

[0049] (4) Curing agent (10-15 parts):

[0050] These include amine curing agents, anhydride curing agents, and polyamide curing agents. The core function of a curing agent is to undergo a cross-linking reaction with the epoxy resin, causing it to transform from a liquid to a solid state, forming a stable three-dimensional cross-linked network structure. The appropriate amount and type of curing agent not only ensures the degree of cure of the epoxy resin composition and influences its ultimate physical properties such as mechanical strength, hardness, and heat resistance, but also the curing reaction process is intertwined with the presence of flame retardants. The timing and amount of curing agent addition will indirectly affect the dispersion of the flame retardant in the system and its interaction with the epoxy resin, providing a synergistic support for the full realization of flame retardant properties.

[0051] 2. Synergistic mechanism of raw materials

[0052] (1) Synergy between phosphorus-based and tin-based flame retardants:

[0053] When the phosphorus-based flame retardant is heated to form a carbon layer, the tin-containing compounds produced by the decomposition of the tin-based flame retardant inhibit the free radical chain reaction in the gas phase, reducing the heat feedback to the condensed phase, making the carbon layer formed by the phosphorus-based flame retardant more stable and less likely to be destroyed. In turn, the stable carbon layer provides a relatively stable environment for the tin-based flame retardant to capture free radicals, and the two complement each other. For example, in the initial stage of combustion, the tin-based flame retardant quickly captures gas-phase free radicals, slowing the spread of flames and buying time for the phosphorus-based flame retardant to activate the condensed phase flame retardant mechanism. The dense carbon layer subsequently formed by the phosphorus-based flame retardant limits the transfer of combustible gas and heat to the gas phase, further inhibiting the consumption of the decomposition products of the tin-based flame retardant, synergistically enhancing the effect, greatly reducing the heat release rate and total heat release of the epoxy resin composition, making the flame retardant performance far superior to that of a single flame retardant system.

[0054] The optimal mass ratio for combining phosphorus-based flame retardants and tin-based flame retardants is 1:1 to 4:1. Within this range, the flame retardant effects of the two flames in the condensed and vapor phases are optimally balanced. If the phosphorus-based flame retardant ratio is too high, the vapor phase flame retardancy will be relatively weak, resulting in poor flame suppression. Conversely, if the tin-based flame retardant ratio is too high, the formation and stability of the condensed phase carbon layer will be affected, making it unable to effectively block heat transfer and thus achieving effective flame retardancy.

[0055] (2) Flame retardant works with epoxy resin and curing agent:

[0056] Epoxy resin provides a dispersion medium for the flame retardant. Its excellent processing properties ensure uniform distribution of the flame retardant, preventing agglomeration that affects its flame retardant effectiveness. The curing agent facilitates the epoxy resin's curing process, "fixing" the flame retardant molecules in a cross-linked network. This prevents leakage and migration of the flame retardant during use, ensuring long-term flame retardant stability. Furthermore, the three-dimensional network structure formed by curing synergizes with the flame retardant to enhance the material's overall thermal stability. At high temperatures, the network restricts the movement of molecular segments and, in conjunction with the flame retardant, slows thermal decomposition, allowing the material to maintain its structural integrity longer in a fire scenario, buying valuable time for evacuation and firefighting.

[0057] 3. The necessity and importance of raw material dosage control

[0058] (1) Phosphorus flame retardant (10-25 parts) and tin-based flame retardant (5-20 parts):

[0059] If the dosage is too small, it will not form a sufficient flame retardant barrier and capture enough free radicals, making it difficult to achieve the ideal flame retardant level. The material will burn rapidly in a fire, causing serious safety hazards. Especially for fields such as electronic appliances that have extremely high fire protection requirements, even a minor fire may lead to catastrophic consequences.

[0060] Excessive use will, on the one hand, increase costs. The price of flame retardants is usually relatively high, and excessive use will significantly increase the cost of material preparation and reduce the market competitiveness of the product. On the other hand, too much flame retardant may cause the mechanical properties of the epoxy resin composition to deteriorate, such as reduced toughness and increased brittleness, affecting its processability and reliability in practical applications. For example, in aviation components, the material must be both flame retardant and have a certain toughness to withstand flight stress. Unreasonable use of flame retardants will make it unable to meet the use requirements.

[0061] (2) Curing agent (10-15 parts):

[0062] Insufficient curing agent dosage leads to incomplete cross-linking of epoxy resin, making the material soft and low in strength. Not only can it not provide stable support for the flame retardant, but it is also prone to melting and flowing at high temperatures, accelerating the spread of fire. Moreover, the molecular chain of the incompletely cured epoxy resin is highly active and is more likely to decompose and produce combustible substances when burned, which runs counter to the flame retardant goal.

[0063] Excessive curing agent will cause the cross-linking density to be too high, making the material too hard and brittle, and increasing the internal stress, which will also affect the mechanical properties. In addition, the excess curing agent may react with the flame retardant to produce adverse side reactions, interfering with the normal function of the flame retardant and reducing the flame retardant efficiency.

[0064] In summary, by precisely controlling the amounts of each raw material in the phosphorus-tin-based flame retardant synergistic flame-retardant epoxy resin composition, efficient synergy between the raw materials is achieved, and an epoxy resin composition with excellent flame retardant properties, good mechanical properties and stability is prepared, providing a solid guarantee for its safe application in multiple fields and achieving technical effects that are difficult to achieve with traditional flame retardant systems.

[0065] Compared with the prior art, the present invention has the following technical advantages:

[0066] The present invention carefully designs and utilizes the synergistic effect of phosphorus-based flame retardants and tin-based flame retardants to construct a unique flame-retardant epoxy resin composition system. This innovative approach brings many breakthrough advantages, which are specifically reflected in the following key aspects:

[0067] 1. Excellent flame retardant and smoke suppression properties: Traditional halogen flame retardants and antimony trioxide flame retardants often produce a large amount of toxic smoke when the materials burn. These toxic fumes not only seriously obstruct the line of sight and greatly increase the difficulty of evacuating people at the fire scene, but also cause strong irritation to the human respiratory system, eyes, etc., and even endanger life. The phosphorus-based flame retardant of the present invention works synergistically with the tin-based flame retardant to quickly and efficiently suppress the chain process of the combustion reaction when heated or exposed to open flames. Phosphorus-based flame retardants produce phosphorus-containing free radicals through thermal decomposition, capture key free radicals in the combustion process, effectively interrupt the combustion reaction, and at the same time promote the formation of a carbonaceous layer on the surface of the epoxy resin, exerting the effect of heat insulation and oxygen isolation. Tin-based flame retardants further strengthen the carbon layer structure. The two complement each other, significantly reducing the flame propagation speed and greatly reducing the amount of smoke generated, providing reliable protection for fire safety.

[0068] 2. Excellent thermal stability: In practical applications, materials are often faced with the test of high temperature environments. Traditional flame retardants may decompose or react adversely with the matrix material at high temperatures, resulting in a decrease in flame retardant properties and degradation of the material's own performance. The flame retardant epoxy resin composition of the present invention exhibits excellent thermal stability. In a high-temperature environment, phosphorus-based flame retardants and tin-based flame retardants can exist stably and continue to exert a synergistic flame retardant effect, ensuring that the molecular structure and physical properties of the epoxy resin are not significantly affected, maintaining the normal use of the material under high-temperature conditions, and greatly expanding its application scenarios. Whether in electronics, aerospace, and other fields that require extremely high thermal stability of materials, or in daily high-temperature working environments, it can be reliably used.

[0069] 3. Outstanding low-carbon and environmentally friendly characteristics: With the continuous enhancement of environmental awareness, the problem of traditional halogen and antimony trioxide flame retardants releasing corrosive gases during combustion has become increasingly prominent. These corrosive gases will not only cause serious corrosion to the equipment and buildings at the fire scene, accelerate the aging of facilities, and increase maintenance costs, but will also cause long-term pollution to the surrounding environment and destroy the ecological balance. The flame retardant system of the present invention completely abandons harmful components such as halogens and antimony trioxide. During the production, use and combustion process, no toxic smoke and corrosive gases will be generated, reducing pollutant emissions from the source and truly achieving low-carbon environmental protection. This is not only in line with the current global trend of green development, but also provides strong support for the sustainable development of related industries. It is expected to become an important development direction for environmentally friendly flame retardants and lead the flame retardant materials industry into a new era of green and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 Cone calorimetry test curves of epoxy resin flame retardant samples (a: HRR, b: THR, c: SPR, d: TSP, e: COP, f: CO2P), where HRR represents heat release rate, THR represents total heat release, SPR represents smoke generation rate, TSP represents total smoke generation, COP represents carbon monoxide generation rate, and CO2P represents carbon dioxide generation rate.

[0071] Figure 2 TGA and DTG curves of epoxy resin flame retardant samples (a: TGAb:DTG). DETAILED DESCRIPTION

[0072] The present invention is further described below by way of specific embodiments. The following examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following examples.

[0073] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0074] In the embodiment of the present invention, the phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition comprises the following raw materials in parts by mass:

[0075] Epoxy resin: 100 parts;

[0076] Phosphorus flame retardant: 10-25 parts;

[0077] Tin-based flame retardant: 5-20 parts;

[0078] Curing agent: 10-15 parts.

[0079] The preparation method of the phosphorus-based flame retardant comprises the following steps:

[0080] (1) Surface modification of nano-SiO2

[0081] Disperse 5-8 parts of nano-SiO2 in 30-40 parts of water, add 1-3 parts of 3-aminopropyltrimethoxysilane, and ultrasonicate for 27-35 minutes at a power of 150-350W. Then adjust the pH to 4-5, and stir the reaction at 72-78°C for 1.8-2.1 hours to obtain modified nano-SiO2.

[0082] (2) Activation of bio-based carbon sources

[0083] Mix 12-18 parts of starch with 5-8 parts of triethanolamine, and treat at a microwave power of 350-550W for 4-12 minutes to prepare activated starch;

[0084] (3) Phosphorus-nitrogen-silicon synergistic reaction

[0085] Add 20-30 parts of ammonium polyphosphate, 10-15 parts of pentaerythritol, and 8-12 parts of melamine to a reactor, heat to 123-135°C, and stir for 25-33 minutes; add modified nano-SiO2 and activated starch, and continue stirring for 0.8-1.2 hours; then add 0.5-2 parts of lecithin, adjust the pH to 6.5-7, raise the reaction temperature to 152-161°C, and maintain for 1.7-2.3 hours to obtain a reaction product;

[0086] (4) Nanoemulsion preparation and drying

[0087] The reaction product is cooled to 64-72° C., 10-20 parts of water are added, and high-speed shear dispersion is performed at 11000-14000 rpm for 13-16 minutes to form a nanoemulsion; and then dried at a vacuum degree of -0.08 to -0.09 MPa and a temperature of 52-60° C. for 8-12 hours to obtain a phosphorus-based flame retardant.

[0088] The preparation method of the tin-based flame retardant comprises the following steps:

[0089] (1) Preparation of mixed metal salt solution

[0090] Dissolve 10-15 parts of zinc acetate, 3-5 parts of aluminum nitrate, and 2-4 parts of magnesium nitrate, respectively, in 80-100 parts of water, and stir at 35-42° C. for 21-28 minutes until completely dissolved to prepare a mixed metal salt solution;

[0091] (2) Add the reaction solution dropwise and stir

[0092] Solution A was first added dropwise to the mixed metal salt solution prepared in step (1), and after stirring for 10-15 minutes, solution B was then added dropwise at a rate of 1-2 drops / second. At the same time, the pH was adjusted to 8.2-9 with aqueous ammonia. After the addition of solution B was completed, 2-4 parts of a 5-10% boric acid solution was added, and the mixture was stirred for 27-32 minutes. The mixture was then heated to 43-48°C and reacted for 2-3 hours to obtain a mixed solution.

[0093] Solution A: Dissolve 12-18 parts of sodium stannate in 30-40 parts of water and stir until completely dissolved;

[0094] Solution B: Dissolve 5-8 parts of ethyl orthosilicate in 10-15 parts of anhydrous ethanol and stir to form a homogeneous solution;

[0095] (3) Hydrothermal reaction

[0096] Transfer the mixed solution obtained in step (2) to a hydrothermal reactor and react at 200-240°C for 12-36 hours;

[0097] (4) Centrifugal washing and drying

[0098] After the reaction is completed, the hydrothermal autoclave is cooled to room temperature, the reaction solution is taken out for centrifugal separation, the precipitate is collected, and the precipitate is washed 3-4 times with water and anhydrous ethanol respectively, and then the precipitate is placed in a vacuum drying oven and dried at 85-102°C for 8-11 hours;

[0099] (5) Surface modification

[0100] The dried precipitate is placed in a mixer, and then 1-3 parts of a silane coupling agent (KH-550) is diluted with 5-10 parts of anhydrous ethanol (mass ratio of 1:3-5) and then dripped into the precipitate in the mixer while stirring (the speed is 900-1000 rpm). After the dripping is completed, the speed is increased to 1200-1500 rpm and stirred at 62-70°C for 2-2.5 hours to produce a tin-based flame retardant. The curing agent includes one or more of an amine curing agent, an acid anhydride curing agent, and a polyamide curing agent.

[0101] The preparation method of the phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition comprises the following steps: epoxy resin, phosphorus-based flame retardant, tin-based flame retardant, and curing agent are weighed and added into a blender to mix evenly; then, the mixture is poured into a preheated mold for curing at a temperature of 60-150° C.; and demolding is performed to obtain the phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition.

[0102] Performance testing and characterization:

[0103] Tensile performance test: EP specimens were tested according to the national standard GB / T 2567-2008 at a tensile rate of 10 mm / min.

[0104] Vertical combustion test: The vertical combustion performance of the flame retardant EP system is measured using a CZF-5 vertical combustion tester in accordance with GB / T 2408-2021.

[0105] Limiting oxygen index determination: Using JF-3 limiting oxygen index instrument, the flame retardant sample is placed vertically on the top of the instrument to burn, and the flame retardant LOI value is obtained by passing the standard.

[0106] Cone calorimetry: The test sample standard is 100mm×100mm×3mm, and the radiation power of the instrument is selected as 50kW / m 2 ;

[0107] Thermogravimetric analysis (TGA): After the sample is fully dried, 3-5 mg is weighed and placed in a crucible to be tested. In a nitrogen atmosphere, the temperature is raised to the required temperature at a heating rate of 10°C / min to study the weight loss of the sample.

[0108] In order to make the disclosure of the present invention more complete, it is described below through more specific embodiments.

[0109] Example 1

[0110] A phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition comprising the following raw materials:

[0111] Epoxy resin: 100g;

[0112] Phosphorus flame retardant: 20g;

[0113] Tin-based flame retardant: 15g;

[0114] Curing agent: 12g.

[0115] The preparation method of the phosphorus-based flame retardant comprises the following steps:

[0116] (1) Surface modification of nano-SiO2

[0117] 6 parts of nano-SiO2 were dispersed in 34 parts of water, 2 parts of 3-aminopropyltrimethoxysilane were added, and the mixture was ultrasonically treated at a power of 300 W for 30 minutes. Then, the pH was adjusted to 4.6, and the mixture was stirred at 75°C for 2 hours to obtain the modified nano-SiO2.

[0118] (2) Activation of bio-based carbon sources

[0119] Activated starch was prepared by mixing 15 parts of starch with 6.5 parts of triethanolamine and treating the mixture at a microwave power of 400 W for 8 minutes.

[0120] (3) Phosphorus-nitrogen-silicon synergistic reaction

[0121] 26 parts of ammonium polyphosphate, 13 parts of pentaerythritol, and 10 parts of melamine were added to a reactor, heated to 130°C, and stirred for 30 minutes; modified nano-SiO2 and activated starch were added, and stirring was continued for 1 hour; then 1.3 parts of lecithin was added, the pH was adjusted to 6.8, and the reaction temperature was raised to 155°C and maintained for 2 hours to obtain a reaction product;

[0122] (4) Nanoemulsion preparation and drying

[0123] The reaction product was cooled to 70° C., 16 parts of water was added, and high-speed shear dispersion was performed at 13,000 rpm for 15 minutes to form a nanoemulsion; the product was then dried at a vacuum degree of -0.09 MPa and a temperature of 58° C. for 10 hours to obtain a phosphorus-based flame retardant.

[0124] The preparation method of the tin-based flame retardant comprises the following steps:

[0125] (1) Preparation of mixed metal salt solution

[0126] Dissolve 13 parts of zinc acetate, 4 parts of aluminum nitrate, and 3 parts of magnesium nitrate in 90 parts of water, respectively, and stir at 40°C for 25 minutes until completely dissolved to prepare a mixed metal salt solution;

[0127] (2) Add the reaction solution dropwise and stir

[0128] Solution A was first added dropwise to the mixed metal salt solution prepared in step (1), and after stirring for 12 minutes, solution B was then added dropwise at a rate of 2 drops / second. At the same time, the pH was adjusted to 8.5 with aqueous ammonia. After the addition of solution B was completed, 3 parts of 8% boric acid solution was added, and the mixture was stirred for 30 minutes. The mixture was then heated to 45°C and reacted for 2.6 hours to obtain a mixed solution.

[0129] Solution A: Dissolve 15 parts of sodium stannate in 36 parts of water and stir until completely dissolved;

[0130] Solution B: Dissolve 7 parts of ethyl orthosilicate in 12 parts of anhydrous ethanol and stir to form a homogeneous solution;

[0131] (3) Hydrothermal reaction

[0132] The mixed solution obtained in step (2) was transferred to a hydrothermal reactor and reacted at 220°C for 24 hours;

[0133] (4) Centrifugal washing and drying

[0134] After the reaction, the hydrothermal autoclave was cooled to room temperature, the reaction solution was taken out and centrifuged, the precipitate was collected, and the precipitate was washed three times with water and anhydrous ethanol respectively, and then placed in a vacuum drying oven and dried at 95°C for 9 h;

[0135] (5) Surface modification

[0136] The dried precipitate was placed in a mixer, and then 2 parts of silane coupling agent (KH-550) were diluted with 8 parts of anhydrous ethanol (mass ratio 1:4), and then dripped into the precipitate in the mixer while stirring (speed of 1000 rpm). After the dripping was completed, the speed was increased to 1400 rpm and stirred at 68 ° C for 2.2 hours to obtain a tin-based flame retardant.

[0137] The curing agent is m-phenylenediamine.

[0138] The preparation method of the phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition is as follows:

[0139] The epoxy resin, phosphorus flame retardant, tin-based flame retardant and curing agent compounded synergistic flame retardant were weighed and added into a high-speed mixer and mixed evenly, then poured into a preheated polyethylene mold and cured at 80°C, and demolded to obtain a flame-retardant epoxy resin composition.

[0140] Comparative Example 1

[0141] A flame retardant epoxy resin composition comprises the following raw materials:

[0142] Epoxy resin: 100g;

[0143] Phosphorus flame retardant: 20g;

[0144] Curing agent: 12g.

[0145] The preparation method of the phosphorus-based flame retardant comprises the following steps:

[0146] (1) Surface modification of nano-SiO2

[0147] 6 parts of nano-SiO2 were dispersed in 34 parts of water, 2 parts of 3-aminopropyltrimethoxysilane were added, and the mixture was ultrasonically treated at a power of 300 W for 30 minutes. Then, the pH was adjusted to 4.6, and the mixture was stirred at 75°C for 2 hours to obtain the modified nano-SiO2.

[0148] (2) Activation of bio-based carbon sources

[0149] Activated starch was prepared by mixing 15 parts of starch with 6.5 parts of triethanolamine and treating the mixture at a microwave power of 400 W for 8 minutes.

[0150] (3) Phosphorus-nitrogen-silicon synergistic reaction

[0151] 26 parts of ammonium polyphosphate, 13 parts of pentaerythritol, and 10 parts of melamine were added to a reactor, heated to 130°C, and stirred for 30 minutes; modified nano-SiO2 and activated starch were added, and stirring was continued for 1 hour; then 1.3 parts of lecithin was added, the pH was adjusted to 6.8, and the reaction temperature was raised to 155°C and maintained for 2 hours to obtain a reaction product;

[0152] (4) Nanoemulsion preparation and drying

[0153] The reaction product was cooled to 70° C., 16 parts of water was added, and high-speed shear dispersion was performed at 13,000 rpm for 15 minutes to form a nanoemulsion; the product was then dried at a vacuum degree of -0.09 MPa and a temperature of 58° C. for 10 hours to obtain a phosphorus-based flame retardant.

[0154] The curing agent is m-phenylenediamine.

[0155] The preparation method of the flame retardant epoxy resin composition is as follows:

[0156] The epoxy resin, phosphorus-based flame retardant and curing agent compounded synergistic flame retardant were weighed and added into a high-speed mixer and mixed evenly, then poured into a preheated polyethylene mold and cured at 80°C, and demolded to obtain a flame-retardant epoxy resin composition.

[0157] Comparative Example 2

[0158] 100 g of epoxy resin and 12 g of curing agent were weighed and added into a high-speed mixer and mixed evenly. The mixture was then poured into a preheated polyethylene mold and cured at 80° C. The mold was then demolded to obtain a flame-retardant epoxy resin composition.

[0159] The curing agent is m-phenylenediamine.

[0160] The components and properties of the cured products of the Examples and Comparative Examples are shown in Table 1:

[0161] Table 1 Comparison of properties of components and cured products in Examples and Comparative Examples

[0162]

[0163] As can be seen from Table 1, when the tin-based flame retardant and the phosphorus-based flame retardant are compounded in a certain proportion and applied to the epoxy resin composition, the vertical combustion grade (Example 1) can reach V-0 level, and the limiting oxygen index (Example 1) reaches 32.4%, which is 16.5% higher than that of (Comparative Example 1) and 44.6% higher than that of pure EP (Comparative Example 2). This shows that there is a synergistic effect between the epoxy resin and the tin-based flame retardant and the phosphorus-based flame retardant.

[0164] Depend on Figure 1It can be seen that as time increases, the heat release rate, total heat release, smoke generation rate, total smoke generation, carbon monoxide generation rate, and carbon dioxide generation rate of Example 1 all reach minimum values ​​compared to Comparative Examples 1 and 2. The curve also shows that the flame retardant effect produced by the synergistic system of phosphorus-tin-based flame retardants acting on the epoxy resin composition is more significant than the effect of adding a phosphorus-based flame retardant alone to the epoxy resin composition.

[0165] Depend on Figure 2 It can be seen that the weight loss trends of the three epoxy resin flame-retardant samples are basically the same, with all experiencing a period of weight loss. The curves reflect a significant increase in the residual mass of Example 1 compared to Comparative Examples 1 and 2. This is due to the addition of the tin-based flame retardant, which effectively promotes the early decomposition of the epoxy resin composition and catalyzes cross-linking to form carbon, quickly forming a dense carbon layer on its surface. This, to a certain extent, blocks the contact of heat and oxygen with the internal matrix surface, increases the residual carbon content, and improves the flame retardancy of the epoxy resin composition.

Claims

1. A phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition, characterized in that: In parts by mass, it includes the following raw materials: Epoxy resin: 100 parts; Phosphorus flame retardant: 10-25 parts; Tin-based flame retardant: 5-20 parts; Curing agent: 10-15 parts.

2. The phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition according to claim 1, characterized in that: In parts by mass, it includes the following raw materials: Epoxy resin: 100 parts; Phosphorus flame retardant: 20 parts; Tin-based flame retardant: 15 parts; Curing agent: 12 parts.

3. A phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition according to claim 1 or 2, characterized in that: The preparation method of the phosphorus-based flame retardant comprises the following steps: (1) Surface modification of nano-SiO2 Disperse 5-8 parts of nano-SiO2 in 30-40 parts of water, add 1-3 parts of 3-aminopropyltrimethoxysilane, and ultrasonicate for 27-35 minutes at a power of 150-350W. Then adjust the pH to 4-5, and stir the reaction at 72-78°C for 1.8-2.1 hours to obtain modified nano-SiO2. (2) Activation of bio-based carbon sources Mix 12-18 parts of starch with 5-8 parts of triethanolamine, and treat at a microwave power of 350-550W for 4-12 minutes to prepare activated starch; (3) Phosphorus-nitrogen-silicon synergistic reaction Add 20-30 parts of ammonium polyphosphate, 10-15 parts of pentaerythritol, and 8-12 parts of melamine to a reactor, heat to 123-135°C, and stir for 25-33 minutes; add modified nano-SiO2 and activated starch, and continue stirring for 0.8-1.2 hours; then add 0.5-2 parts of lecithin, adjust the pH to 6.5-7, raise the reaction temperature to 152-161°C, and maintain for 1.7-2.3 hours to obtain a reaction product; (4) Nanoemulsion preparation and drying The reaction product is cooled to 64-72° C., 10-20 parts of water are added, and high-speed shear dispersion is performed at 11000-14000 rpm for 13-16 minutes to form a nanoemulsion; and then dried at a vacuum degree of -0.08 to -0.09 MPa and a temperature of 52-60° C. for 8-12 hours to obtain a phosphorus-based flame retardant.

4. A phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition according to claim 1 or 2, characterized in that: The preparation method of the tin-based flame retardant comprises the following steps: 1) Preparation of mixed metal salt solution Dissolve 10-15 parts of zinc acetate, 3-5 parts of aluminum nitrate, and 2-4 parts of magnesium nitrate, respectively, in 80-100 parts of water, and stir at 35-42° C. for 21-28 minutes until completely dissolved to prepare a mixed metal salt solution; 2) Add the reaction solution dropwise and stir Solution A was first added dropwise to the mixed metal salt solution prepared in step 1), and after stirring for 10-15 minutes, solution B was then added dropwise at a rate of 1-2 drops / second. The pH was adjusted to 8.2-9 with aqueous ammonia. After solution B was added dropwise, 2-4 parts of a 5-10% boric acid solution was added, and stirring was continued for 27-32 minutes. The mixture was then heated to 43-48°C and reacted for 2-3 hours to obtain a mixed solution. 3) Hydrothermal reaction Transfer the mixed solution obtained in step 2) to a hydrothermal reactor and react at 200-240°C for 12-36 hours; 4) Centrifugal washing and drying After the reaction is completed, the hydrothermal autoclave is cooled to room temperature, the reaction solution is taken out for centrifugal separation, the precipitate is collected, and the precipitate is washed 3-4 times with water and anhydrous ethanol respectively, and then the precipitate is placed in a vacuum drying oven and dried at 85-102°C for 8-11 hours; 5) Surface modification The dried precipitate is placed in a mixer, and then 1-3 parts of silane coupling agent are diluted with 5-10 parts of anhydrous ethanol, and then dripped into the precipitate in the mixer, and stirred while dripping at a speed of 900-1000 rpm. After dripping, the speed is increased to 1200-1500 rpm, and stirred at a temperature of 62-70°C for 2-2.5 hours to obtain a tin-based flame retardant.

5. The phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition according to claim 4, characterized in that: The solution A in step 2) is obtained by dissolving 12-18 parts of sodium stannate in 30-40 parts of water and stirring until completely dissolved.

6. The phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition according to claim 4, characterized in that: The solution B in step 2) is prepared by dissolving 5-8 parts of ethyl orthosilicate in 10-15 parts of anhydrous ethanol and stirring to form a homogeneous solution.

7. The phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition according to claim 4, characterized in that: The mass ratio of the alkane coupling agent to anhydrous ethanol in step 5) is 1:3-5.

8. The phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition according to claim 1, characterized in that: The curing agent includes one or more of an amine curing agent, an acid anhydride curing agent, and a polyamide curing agent.

9. A method for preparing a phosphorus-tin based flame retardant synergistic flame retardant epoxy resin composition according to any one of claims 1 to 8, characterized in that: The following steps are involved: The synergistic flame retardant compounded of epoxy resin, phosphorus-based flame retardant, tin-based flame retardant and curing agent is weighed and added into a blender for uniform mixing, then poured into a preheated mold for curing, and demolded to obtain a phosphorus-tin-based flame retardant synergistic flame retardant epoxy resin composition.

10. The method for preparing a phosphorus-tin based flame retardant synergistic flame retardant epoxy resin composition according to claim 9, characterized in that: The curing temperature in the mold is 60-150°C.

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