Silicon-phosphorus flame retardant, preparation method, composition and application

Abstract

This invention provides a silicon-phosphorus flame retardant, its preparation method, composition, and application. The silicon-phosphorus flame retardant is mainly composed of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and a vinyl ladder-shaped silsesquioxane epoxy resin. The proposed silicon-phosphorus synergistic flame-retardant epoxy resin composition, by weight, comprises: 80-100 parts epoxy resin; 80-100 parts curing agent; 5-30 parts toughening agent; 1-5 parts accelerator; and 1-15 parts silicon-phosphorus flame retardant. The silicon-phosphorus flame retardant is a composite phosphorus-silicon element flame retardant with high flame retardant efficiency and good flame retardant effect on the epoxy resin composition. The flame-retardant epoxy resin composition of the present invention has a viscosity of 5000 mPa·s to 8000 mPa·s, which gives the epoxy resin composition excellent flame-retardant properties, reaching V-0 rating. At the same time, it has low viscosity and good fiber impregnation properties, and can be applied to fiber impregnation and winding molding structural parts of electrical equipment.

Description

Technical Field

[0001] This invention belongs to the field of epoxy resin impregnation flame retardant technology, specifically relating to a silicon-phosphorus flame retardant, its preparation method, composition, and application. Background Technology

[0002] Epoxy resin has long been widely used as the main matrix material for impregnation and encapsulation of electrical equipment (such as transformers, instrument transformers, and insulators) due to its excellent electrical insulation properties, good mechanical strength, low curing shrinkage, and mature processing technology. In recent years, with the rapid development of high-voltage and ultra-high-voltage power transmission technologies and the upgrading of power grids, electrical equipment is evolving towards larger capacity, smaller size, and higher reliability. This places more stringent requirements on the comprehensive performance of epoxy resin materials used for encapsulation. Especially under high-temperature operating conditions, epoxy resin materials are not only required to maintain their original insulation and mechanical properties, but also need to possess excellent flame-retardant properties to prevent fires caused by electrical faults and ensure the safe operation of the power grid.

[0003] However, pure epoxy resin cured products are flammable materials with a typically low limiting oxygen index (LOI). They tend to continue burning after the flame is removed, releasing large amounts of heat and dense smoke, making them unsuitable for meeting the fire safety standards of high-voltage electrical equipment. Therefore, flame-retardant modification of epoxy resin is necessary. While halogenated flame retardants offer high flame-retardant efficiency in traditional flame-retardant technologies, they release toxic and corrosive hydrogen halide gases during combustion, polluting the environment and easily corroding delicate internal components of electrical equipment. Their application is facing increasingly stringent restrictions. Inorganic flame retardants (such as aluminum hydroxide and magnesium hydroxide), while environmentally friendly and non-toxic, typically require extremely high proportions to achieve ideal flame-retardant effects. This significantly increases the viscosity of the resin system, causing the material to lose its processing fluidity and severely deteriorating the mechanical and electrical properties of the epoxy resin.

[0004] As an environmentally friendly alternative, organic phosphorus-containing flame retardants have become a research hotspot in the field of halogen-free flame retardants for epoxy resins. Among them, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and its derivatives exhibit excellent flame retardant performance due to their unique cyclic phosphate ester structure. Their flame retardant mechanism mainly involves decomposition in the gas phase to generate PO· and other free radicals, which capture H· and OH· free radicals in the combustion chain reaction, thereby interrupting the combustion process. However, in practical applications, existing DOPO-type flame retardants are usually directly and physically blended into epoxy resins in the form of small molecule compounds. This simple physical doping method has significant drawbacks: on the one hand, small molecule flame retardants often have poor compatibility with epoxy resin matrices and are prone to migration and precipitation during curing or long-term use, affecting the long-term stability and dielectric properties of the material; on the other hand, in order to achieve a high flame retardancy rating of V-0 for epoxy resins, it is usually necessary to add a large mass fraction of DOPO-type flame retardants, but excessive addition will significantly increase the viscosity of the system, destroy the integrity of the resin curing crosslinking network, and lead to a significant decrease in key mechanical and thermal properties of the material, such as impact toughness and glass transition temperature.

[0005] Furthermore, in certain specific applications of electrical equipment, such as the fiber impregnation and winding process for insulating structural components, epoxy resin compositions are required to possess not only high flame retardancy and high toughness, but also to maintain a low initial viscosity to ensure that the resin can fully and uniformly penetrate into the fiber-reinforced material. In existing technologies, simply increasing the amount of DOPO-type flame retardants or compounding with conventional rigid fillers often results in a dramatic increase in system viscosity, which cannot meet the dual requirements of low viscosity and high penetration in fiber impregnation processes. Therefore, how to achieve highly efficient flame retardancy in epoxy resin compositions with extremely low addition amounts, without significantly increasing system viscosity or compromising material toughness and mechanical strength, is a highly challenging technical problem currently facing those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to solve the problem that the flame retardant properties of epoxy resin in the prior art are insufficient and cannot be applied to high-voltage electrical equipment.

[0007] The objective of this invention is achieved through the following technical solution: A silicon-phosphorus flame retardant has the following chemical structural formula: . Based on the same inventive concept, the present invention also provides a method for preparing a silicon-phosphorus flame retardant, the method comprising the following steps: A phenyl silane coupling agent and a vinyl silane coupling agent are subjected to a hydrolysis-condensation reaction in the presence of a solvent, deionized water and a catalyst to obtain a phenyl-containing vinyl ladder-shaped silsesquioxane. The phenyl-containing vinyl ladder silsesquioxane was grafted with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in the presence of an initiator to obtain the silicon-phosphorus flame retardant.

[0008] Preferably, the chemical structural formula of the vinyl ladder-shaped silsesquioxane is as follows: .

[0009] Preferably, the phenylsilane coupling agent is one of phenyltrimethoxysilane, phenyltrichlorosilane, and phenyltriethoxysilane.

[0010] Preferably, the vinyl silane coupling agent is one of vinyltrimethoxysilane, vinyltrichlorosilane, and vinyltriethoxysilane.

[0011] Preferably, the molar ratio of the phenylsilane coupling agent to the vinylsilane coupling agent is 0.5 to 1.

[0012] Preferably, the solvent is tetrahydrofuran (THF), and the mass ratio of tetrahydrofuran to water is 4:1 to 1:1.

[0013] Preferably, the catalyst is tetramethylammonium hydroxide, and its addition amount is 1% to 3% of the total mass of the silane coupling agent.

[0014] Preferably, the hydrolysis-condensation reaction takes 24 to 36 hours at room temperature.

[0015] Preferably, the molar ratio of the vinyl group in the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to the vinyl group in the phenyl-containing vinyl ladder silsesquioxane is 0.3 to 0.8.

[0016] Preferably, the initiator is azobisisobutyronitrile, and its addition amount is 0.1% to 0.3% of the mass of the phenyl-containing vinyl ladder silsesquioxane.

[0017] Preferably, the total mass of the phenylsilane coupling agent and the vinylsilane coupling agent accounts for 30% to 50% of the total mass of tetrahydrofuran and deionized water.

[0018] Preferably, the grafting reaction is carried out in tetrahydrofuran, and the mass ratio of reactant to tetrahydrofuran is 1:2 to 1:4.

[0019] Preferably, the grafting reaction is carried out at a temperature of 80°C to 100°C for 8 to 24 hours.

[0020] Based on the same inventive concept, the present invention also provides a flame-retardant epoxy resin composition, comprising, by weight parts: 80-100 parts of epoxy resin; 80-100 parts of curing agent; 1-15 parts of the silicon-phosphorus flame retardant mentioned above; Toughening agent 5-25 parts; Accelerator 1-5 parts.

[0021] Preferably, the epoxy resin is one or more of bisphenol A glycidyl ether, bisphenol F glycidyl ether, and hydantoin epoxy resin.

[0022] Preferably, the epoxy value of the epoxy resin is 0.4 to 0.7.

[0023] Preferably, the curing agent is one or more of tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, methylhexahydrophthalic anhydride, and methyltetrahydrophthalic anhydride.

[0024] Preferably, the accelerator is one or more of phenol, imidazole, and dimethylaminobenzamine.

[0025] Preferably, the toughening agent is one or more of nano-silica, nano-alumina, hydroxyapatite, and core-shell rubber.

[0026] Preferably, at 25°C, the overall viscosity of the flame-retardant epoxy resin composition is 5000 mPa·s to 8000 mPa·s.

[0027] Based on the same inventive concept, the present invention also provides the application of the flame-retardant epoxy resin composition as described in Example 12 in fiber impregnation molding products.

[0028] Preferably, the fiber-impregnated and wound parts are heat-cured at a temperature of 80~100℃ for 2~4 hours, followed by treatment at 120~130℃ for 2~3 hours.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention constructs a silicon-phosphorus synergistic flame-retardant molecular structure by grafting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) onto a phenyl-containing vinyl ladder-shaped silsesquioxane. This core design overcomes the limitation of traditional flame retardants having only a single function. From the perspective of the flame-retardant mechanism, during combustion, the grafted DOPO group decomposes upon heating, releasing phosphorus-containing free radicals such as PO· and PO2·. These highly reactive free radicals can efficiently capture H· and OH· free radicals in the gas-phase combustion zone, thereby blocking the chain reaction of gas-phase free radicals. At the same time, the decomposition of the phosphorus-containing group also absorbs heat and promotes the dehydration of organic groups to form a dense carbon layer. Meanwhile, the silicon element in the ladder-shaped silsesquioxane migrates to the surface during combustion, generating a silicon-oxygen protective layer rich in silica. This not only improves the residual mass of combustion but also synergizes with the carbon layer promoted by the phosphorus element to form an aerogel-like barrier, effectively isolating oxygen and heat transfer. This dual mechanism of gas-phase free radical quenching and condensed-phase barrier enhancement enables the silicon-phosphorus flame retardant to achieve excellent V-0 flame retardant performance in epoxy resin compositions with a low dosage of only 1-15 parts, avoiding the dilution of the inherent properties of the matrix resin caused by adding large amounts of flame retardant. Furthermore, the phenyl-containing trapezoidal silsesquioxane skeleton possesses both rigidity and flexibility. Its rigid trapezoidal structure is highly compatible with the highly cross-linked network mechanical properties of epoxy resin, preventing stress concentration, while the inherent flexibility of the silicon-oxygen bond provides a toughness buffer for the system. The introduction of the benzene ring significantly improves the compatibility between the flame retardant and epoxy resin through the principle of similar compatibility and π-π interactions. Thus, the flame-retardant epoxy resin composition achieves extreme flame retardant performance while maintaining an impact strength of 16-20 kJ / m², completely solving the industry pain point of the difficulty in simultaneously achieving flame retardancy and toughening.

[0030] In terms of precise control of the preparation process and formulation parameters, this invention further ensures the stable realization of the aforementioned excellent properties. In the synthesis of trapezoidal silsesquioxanes, controlling the molar ratio of phenylsilane coupling agent to vinylsilane coupling agent to be 0.5–1, and conducting a long-term hydrolysis-condensation reaction at a mild temperature of 5–35°C for 20–28 hours, avoids amorphous cross-linking caused by high temperatures, providing sufficient kinetic conditions for the ordered self-assembly of silicon-oxygen bonds, thereby ensuring the formation of a regular trapezoidal cage structure. Furthermore, controlling the total mass of the silane coupling agent to be 30%–50% of the mixed solvent and the catalyst dosage to 1%–3% maintains suitable reaction concentrations and catalytic activity, avoids premature gelation, and ensures the integrity and purity of the product structure. In the grafting reaction, the molar ratio of DOPO to vinyl groups was limited to 0.3–0.8. This ensured sufficient phosphorus introduction to maintain efficient gas-phase flame retardancy while preserving the intact skeleton of unreacted vinyl groups and ladder-like siloxanes, maintaining molecular rigidity and avoiding steric hindrance and phase separation caused by excessive grafting. The addition of 0.1%–0.3% of the initiator azobisisobutyronitrile (AIBN) matched the grafting reaction temperature of 100℃–160℃, ensuring stable initiation of free radicals and chain growth, making the grafting reaction complete and controllable. Regarding the epoxy resin composition, epoxy resins with an epoxy value of 0.4–0.7 were selected and combined with a specific ratio of curing agent to construct a three-dimensional network with moderate crosslinking density. This not only provided a fundamental guarantee for mechanical properties and electrical insulation but also, thanks to the high molecular compatibility of the flame retardant and the synergistic effect of the toughening agent, kept the overall viscosity of the composition within the extremely low range of 5000–8000 mPa·s at 25℃. This low viscosity characteristic endows the epoxy composition with extremely excellent flowability and wettability, perfectly meeting the stringent requirements of deep resin penetration and full wetting in the fiber impregnation and winding molding process of electrical equipment. At the same time, the setting of the thermosetting process (treatment at 80~100℃ for 2~4 hours followed by treatment at 120~130℃ for 2~3 hours) takes into account the slow wetting at low viscosity and the subsequent high temperature rapid curing and shaping, ultimately achieving a perfect unity of flame retardancy, high toughness, low viscosity and excellent processability. Detailed Implementation

[0031] To further understand the technical solution of the present invention, some embodiments are provided below, which are not limited to the preferred embodiments and do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by anyone under the guidance of the present invention or by combining the present invention with other prior art features, falls within the protection scope of the present invention.

[0032] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0033] The epoxy resins used in the examples and comparative examples were all Hongchang resins, with an epoxy value of 0.4~0.7 and a viscosity of 8000mPa·s~10000mPa·s@25℃.

[0034] The molar ratio of vinyl to phenyl in the ladder-shaped silsesquioxane used in the examples and comparative examples was 0.8. Preparation method: A mixture of deionized water and tetrahydrofuran was added to a reaction vessel in a mass ratio of 2:1. Vinylsilane coupling agent and phenylsilane coupling agent were then added dropwise to the reaction vessel. The total mass of the silane coupling agent was twice that of the solution. Tetramethylammonium hydroxide was added at a mass of 1% of the silane coupling agent. The molar ratio of the two was 0.8. The reaction was carried out at room temperature for 24 hours. After the reaction was completed, the mixture was extracted and purified to obtain the sesquioxane with the target ladder structure.

[0035] Example 1 This invention provides a silicon-phosphorus flame retardant having the following chemical structural formula: .

[0036] Based on the same inventive concept, the present invention also provides a method for preparing a silicon-phosphorus flame retardant, the method comprising the following steps: A phenyl silane coupling agent and a vinyl silane coupling agent are subjected to a hydrolysis-condensation reaction in the presence of a solvent, deionized water and a catalyst to obtain a phenyl-containing vinyl ladder-shaped silsesquioxane. The phenyl-containing vinyl ladder silsesquioxane was grafted with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in the presence of an initiator to obtain the silicon-phosphorus flame retardant.

[0037] Preferably, the chemical structural formula of the vinyl ladder-shaped silsesquioxane is as follows: .

[0038] The specific implementation process of this embodiment is as follows: DOPO and ladder-shaped silsesquioxane epoxy were added to a reaction vessel, dissolved in THF (tetrahydrofuran), and azobisisobutyronitrile (AIBN) was added at a mass of 0.1% of the total mass of DOPO and ladder-shaped silsesquioxane epoxy. The mixture was heated to 100°C and reacted for 16 hours to obtain the final product. The amount of DOPO added was 50% of the vinyl content in the ladder-shaped silsesquioxane.

[0039] The silicon-phosphorus flame retardant epoxy resin composition of this embodiment includes: 100 parts of bisphenol A epoxy resin, 90 parts of methyl nadic anhydride, 5 parts of nano silica, 1 part of dimethylaminobenzamine, and 1 part of silicon-phosphorus flame retardant.

[0040] Sample test pieces were prepared by casting the well-mixed silicon-phosphorus flame retardant epoxy resin composition. The curing process was a heat curing treatment at 100℃ for 3 hours and 130℃ for 2 hours.

[0041] Example 2 The preparation method of the silicon-phosphorus flame retardant in this embodiment is as follows: DOPO and ladder-shaped silsesquioxane epoxy were added to a reaction vessel, dissolved in THF (tetrahydrofuran), and azobisisobutyronitrile (AIBN) was added at a mass of 0.1% of the total mass of DOPO and ladder-shaped silsesquioxane epoxy. The mixture was heated to 100°C and reacted for 16 hours to obtain the final product. The amount of DOPO added was 50% of the vinyl content in the ladder-shaped silsesquioxane.

[0042] The silicon-phosphorus flame retardant epoxy resin composition of this embodiment includes: 100 parts of bisphenol A epoxy resin, 90 parts of methyl nadic anhydride, 5 parts of nano silica, 1 part of dimethylaminobenzamine, and 7 parts of silicon-phosphorus flame retardant.

[0043] Sample test pieces were prepared by casting the well-mixed silicon-phosphorus flame retardant epoxy resin composition. The curing process was a heat curing treatment at 100℃ for 3 hours and 130℃ for 2 hours.

[0044] Example 3 The preparation method of the silicon-phosphorus flame retardant in this embodiment is as follows: DOPO and ladder-shaped silsesquioxane epoxy were added to a reaction vessel, dissolved in THF (tetrahydrofuran), and azobisisobutyronitrile (AIBN) was added at a mass of 0.1% of the total mass of DOPO and ladder-shaped silsesquioxane epoxy. The mixture was heated to 100°C and reacted for 16 hours to obtain the final product. The amount of DOPO added was 50% of the vinyl content in the ladder-shaped silsesquioxane.

[0045] The silicon-phosphorus flame retardant epoxy resin composition of this embodiment includes: 100 parts of bisphenol A epoxy resin, 90 parts of methyl nadic anhydride, 5 parts of nano silica, 1 part of dimethylaminobenzamine, and 15 parts of silicon-phosphorus flame retardant.

[0046] Sample test pieces were prepared by casting the well-mixed silicon-phosphorus flame retardant epoxy resin composition. The curing process was a heat curing treatment at 100℃ for 3 hours and 130℃ for 2 hours.

[0047] Example 4 The preparation method of the silicon-phosphorus flame retardant in this embodiment is as follows: DOPO and ladder-shaped silsesquioxane epoxy were added to a reaction vessel, dissolved in THF (tetrahydrofuran), and azobisisobutyronitrile (AIBN) was added at a mass of 0.3% of the total mass of DOPO and ladder-shaped silsesquioxane epoxy. The mixture was heated to 100°C and reacted for 24 hours to obtain the final product. The amount of DOPO added was 80% of the vinyl content in the ladder-shaped silsesquioxane.

[0048] The silicon-phosphorus flame retardant epoxy resin composition of this embodiment includes: 100 parts of bisphenol A epoxy resin, 90 parts of methyl nadic anhydride, 5 parts of nano silica, 1 part of dimethylaminobenzamine, and 7 parts of silicon-phosphorus flame retardant.

[0049] Sample test pieces were prepared by casting the well-mixed silicon-phosphorus flame retardant epoxy resin composition. The curing process was a heat curing treatment at 100℃ for 3 hours and 130℃ for 2 hours.

[0050] Example 5 The preparation method of the silicon-phosphorus flame retardant in this embodiment is as follows: DOPO and ladder-shaped silsesquioxane epoxy were added to a reaction vessel, dissolved in THF (tetrahydrofuran), and azobisisobutyronitrile (AIBN) was added at a mass of 0.1% of the total mass of DOPO and ladder-shaped silsesquioxane epoxy. The mixture was heated to 80°C and reacted for 16 hours to obtain the final product. The amount of DOPO added was 30% of the vinyl content in the ladder-shaped silsesquioxane.

[0051] The silicon-phosphorus flame retardant epoxy resin composition of this embodiment includes: 100 parts of bisphenol A epoxy resin, 90 parts of methyl nadic anhydride, 5 parts of nano silica, 1 part of dimethylaminobenzamine, and 7 parts of silicon-phosphorus flame retardant.

[0052] Sample test pieces were prepared by casting the well-mixed silicon-phosphorus flame retardant epoxy resin composition. The curing process was a heat curing treatment at 100℃ for 3 hours and 130℃ for 2 hours.

[0053] Example 6 The preparation method of the silicon-phosphorus flame retardant in this embodiment is as follows: DOPO and ladder-shaped silsesquioxane epoxy were added to a reaction vessel, dissolved in THF (tetrahydrofuran), and azobisisobutyronitrile (AIBN) was added at a mass of 0.2% of the total mass of DOPO and ladder-shaped silsesquioxane epoxy. The mixture was heated to 100°C and reacted for 16 hours to obtain the final product. The amount of DOPO added was 50% of the vinyl content in the ladder-shaped silsesquioxane.

[0054] The silicon-phosphorus flame retardant epoxy resin composition of this embodiment includes: 100 parts of bisphenol A epoxy resin, 80 parts of methyl nadic anhydride, 5 parts of nano silica, 1 part of dimethylaminobenzamine, and 3 parts of silicon-phosphorus flame retardant.

[0055] Sample test pieces were prepared by casting the well-mixed silicon-phosphorus flame retardant epoxy resin composition. The curing process was a heat curing treatment at 100℃ for 3 hours and 130℃ for 2 hours.

[0056] Example 7 The preparation method of the silicon-phosphorus flame retardant in this embodiment is as follows: DOPO and ladder-shaped silsesquioxane epoxy were added to a reaction vessel, dissolved in THF (tetrahydrofuran), and azobisisobutyronitrile (AIBN) was added at a mass of 0.2% of the total mass of DOPO and ladder-shaped silsesquioxane epoxy. The mixture was heated to 100°C and reacted for 16 hours to obtain the final product. The amount of DOPO added was 50% of the vinyl content in the ladder-shaped silsesquioxane.

[0057] The silicon-phosphorus flame retardant epoxy resin composition of this embodiment includes: 100 parts of bisphenol A epoxy resin, 95 parts of methyl nadic anhydride, 5 parts of nano silica, 1 part of dimethylaminobenzamine, and 3 parts of silicon-phosphorus flame retardant.

[0058] Sample test pieces were prepared by casting the well-mixed silicon-phosphorus flame retardant epoxy resin composition. The curing process was a heat curing treatment at 100℃ for 3 hours and 130℃ for 2 hours.

[0059] Example 8 The preparation method of the silicon-phosphorus flame retardant in this embodiment is as follows: DOPO and ladder-shaped silsesquioxane epoxy were added to a reaction vessel, dissolved in THF (tetrahydrofuran), and azobisisobutyronitrile (AIBN) was added at a mass of 0.1% of the total mass of DOPO and ladder-shaped silsesquioxane epoxy. The mixture was heated to 100°C and reacted for 16 hours to obtain the final product. The amount of DOPO added was 50% of the vinyl content in the ladder-shaped silsesquioxane.

[0060] The silicon-phosphorus flame retardant epoxy resin composition of this embodiment includes: 90 parts of bisphenol A epoxy resin, 90 parts of methyl nadic anhydride, 10 parts of nano silica, 3 parts of dimethylaminobenzamine, and 7 parts of silicon-phosphorus flame retardant.

[0061] Sample test pieces were prepared by casting the well-mixed silicon-phosphorus flame retardant epoxy resin composition. The curing process was a heat curing treatment at 100℃ for 3 hours and 130℃ for 2 hours.

[0062] Example 9 The preparation method of the silicon-phosphorus flame retardant in this embodiment is as follows: DOPO and ladder-shaped silsesquioxane epoxy were added to a reaction vessel, dissolved in THF (tetrahydrofuran), and azobisisobutyronitrile (AIBN) was added at a mass of 0.1% of the total mass of DOPO and ladder-shaped silsesquioxane epoxy. The mixture was heated to 100°C and reacted for 16 hours to obtain the final product. The amount of DOPO added was 50% of the vinyl content in the ladder-shaped silsesquioxane.

[0063] The silicon-phosphorus flame retardant epoxy resin composition of this embodiment includes: 100 parts of bisphenol A epoxy resin, 90 parts of methyl nadic anhydride, 10 parts of nano silica, 1 part of dimethylaminobenzamine, and 3 parts of silicon-phosphorus flame retardant.

[0064] Sample test pieces were prepared by casting the well-mixed silicon-phosphorus flame retardant epoxy resin composition. The curing process was a heat curing treatment at 100℃ for 3 hours and 130℃ for 2 hours.

[0065] Example 10 The preparation method of the silicon-phosphorus flame retardant in this embodiment is as follows: DOPO and ladder-shaped silsesquioxane epoxy were added to a reaction vessel, dissolved in THF (tetrahydrofuran), and azobisisobutyronitrile (AIBN) was added at a mass of 0.1% of the total mass of DOPO and ladder-shaped silsesquioxane epoxy. The mixture was heated to 100°C and reacted for 16 hours to obtain the final product. The amount of DOPO added was 50% of the vinyl content in the ladder-shaped silsesquioxane.

[0066] The silicon-phosphorus flame retardant epoxy resin composition of this embodiment includes: 80 parts of bisphenol A epoxy resin, 20 parts of hydantoin epoxy resin, 90 parts of methyl nadic anhydride, 5 parts of nano silica, 1 part of dimethylaminobenzamine, and 3 parts of silicon-phosphorus flame retardant.

[0067] Sample test pieces were prepared by casting the well-mixed silicon-phosphorus flame retardant epoxy resin composition. The curing process was a heat curing treatment at 100℃ for 3 hours and 130℃ for 2 hours.

[0068] Example 11 The preparation method of the silicon-phosphorus flame retardant in this embodiment is as follows: DOPO and ladder-shaped silsesquioxane epoxy were added to a reaction vessel, dissolved in THF (tetrahydrofuran), and azobisisobutyronitrile (AIBN) was added at a mass of 0.1% of the total mass of DOPO and ladder-shaped silsesquioxane epoxy. The mixture was heated to 100°C and reacted for 16 hours to obtain the final product. The amount of DOPO added was 50% of the vinyl content in the ladder-shaped silsesquioxane.

[0069] The silicon-phosphorus flame retardant epoxy resin composition of this embodiment includes: 100 parts of bisphenol A epoxy resin, 90 parts of methyl nadic anhydride, 25 parts of nano silica, 3 parts of dimethylaminobenzamine, and 3 parts of silicon-phosphorus flame retardant.

[0070] Sample test pieces were prepared by casting the well-mixed silicon-phosphorus flame retardant epoxy resin composition. The curing process was a heat curing treatment at 100℃ for 3 hours and 130℃ for 2 hours.

[0071] Comparative Example 1 The epoxy resin composition of this comparative example includes: 100 parts of bisphenol A epoxy resin, 90 parts of methyl nadic anhydride, 5 parts of nano silica, and 5 parts of dimethylaminobenzamine.

[0072] The mixed epoxy resin composition was used to prepare sample test pieces by casting. The curing process was a heat curing treatment at 100℃ for 3 hours and 130℃ for 2 hours.

[0073] Comparative Example 2 The preparation method of the silicon-phosphorus flame retardant in this comparative example is as follows: The epoxy resin composition of this comparative example includes: 100 parts of bisphenol A epoxy resin, 90 parts of methyl nadic anhydride, 5 parts of nano silica, 3 parts of dimethylaminoaniline, and 3 parts of trapezoidal silsesquioxane.

[0074] The mixed epoxy resin composition was used to prepare sample test pieces by casting. The curing process was a heat curing treatment at 100℃ for 3 hours and 130℃ for 2 hours.

[0075] Test case The Limiting Oxygen Index (LOI) test reference standard GB 2406-80, with a sample size of 120mm×6.5mm×3.5mm.

[0076] The vertical burning (VBT) test references the standard FMVSS 302 / ZSO 3975, with a sample size of 127mm × 12.5mm × 3mm.

[0077] Impact strength was tested according to the national standard GB / T2571-1995. The test was conducted using the ZLCFD-5.5 composite impact testing machine manufactured by Jinan Zhongluchang Testing Machine Manufacturing Co., Ltd. The test temperature was 25℃. Each sample was tested 5 times, and the average value of the measurement results was taken.

[0078] The dielectric performance testing process was conducted according to the national standard GB / T1409-2006, "Recommended Methods for Measuring Permittivity and Dielectric Loss Factor of Electrical Insulation Materials at Power Frequency, Audio Frequency and High Frequency." A dielectric performance tester was used to test the dielectric constant and dielectric loss of the samples. The samples were circular discs with a diameter of 100 mm and a thickness of 1 mm. The test frequency was 50 Hz, the temperature was 25℃, and the voltage was 1 kV. Each sample was tested five times, and the average value of the results was taken.

[0079] The test results are shown in Table 1.

[0080]

[0081] As can be seen from the comparison of Examples 1-11 with Comparative Examples 1 and 2, the epoxy resin composition using the silicon-phosphorus flame retardant of the present invention has better flame retardant performance and a higher flame retardant rating, while also having excellent impact strength and a low dielectric constant, thus solving the problem of epoxy resin being flammable and not flame retardant.

[0082] Example 12 The preparation method of the silicon-phosphorus flame retardant in this embodiment is as follows: Phenyltrichlorosilane and vinyltrichlorosilane were subjected to a hydrolysis-condensation reaction in the presence of tetrahydrofuran, deionized water, and tetramethylammonium hydroxide. The molar ratio of phenylsilane to vinylsilane was 0.5, the mass ratio of tetrahydrofuran to water was 4:1, the total mass of silane coupling agent accounted for 30% of the total mass of tetrahydrofuran and deionized water, and the amount of catalyst added was 1% of the total mass of silane. The reaction was carried out at room temperature for 24 h to obtain a phenyl-containing vinyl ladder-shaped silsesquioxane. DOPO was grafted with the above-mentioned silsesquioxane in THF under the initiation of azobisisobutyronitrile; wherein the molar ratio of DOPO to vinyl group was 0.5, the initiator was 0.1% of the mass of silsesquioxane, the mass ratio of reactant to THF was 1:2, and the reaction was carried out at 80°C for 8 hours to obtain a silicon-phosphorus flame retardant.

[0083] The composition formulation in this embodiment is the same as that in Example 2.

[0084] Example 13 The preparation method of the silicon-phosphorus flame retardant in this embodiment is as follows: Phenyltriethoxysilane and vinyltriethoxysilane were subjected to a hydrolysis-condensation reaction in the presence of tetrahydrofuran, deionized water, and tetramethylammonium hydroxide. The molar ratio of phenylsilane to vinylsilane was 1.0, the mass ratio of tetrahydrofuran to water was 1:1, the total mass of silane coupling agent accounted for 50% of the total mass of tetrahydrofuran and deionized water, and the amount of catalyst added was 3% of the total mass of silane. The reaction was carried out at room temperature for 36 h to obtain a phenyl-containing vinyl ladder-shaped silsesquioxane. DOPO was grafted with the above-mentioned silsesquioxane in THF (tetrahydrofuran) under the initiation of azobisisobutyronitrile; wherein the molar ratio of DOPO to vinyl group was 0.8, the initiator was 0.3% of the mass of silsesquioxane, the mass ratio of reactant to THF was 1:4, and the reaction was carried out at 100°C for 24 h to obtain a silicon-phosphorus flame retardant.

[0085] The composition formulation in this embodiment is the same as that in Example 2.

[0086] Example 14 The preparation method of the silicon-phosphorus flame retardant in this embodiment is as follows: Phenyltrimethoxysilane and vinyltrimethoxysilane were subjected to a hydrolysis-condensation reaction in the presence of tetrahydrofuran, deionized water, and tetramethylammonium hydroxide. The molar ratio of phenylsilane to vinylsilane was 0.75, the mass ratio of tetrahydrofuran to water was 2.5:1, the total mass of silane coupling agent accounted for 40% of the total mass of tetrahydrofuran and deionized water, and the amount of catalyst added was 2% of the total mass of silane. The reaction was carried out at room temperature for 30 h to obtain a phenyl-containing vinyl ladder-shaped silsesquioxane. DOPO was grafted with the above-mentioned silsesquioxane in THF under the initiation of azobisisobutyronitrile; wherein the molar ratio of DOPO to vinyl group was 0.55, the initiator was 0.2% of the mass of silsesquioxane, the mass ratio of reactant to THF was 1:3, and the reaction was carried out at 90°C for 16 h to obtain a silicon-phosphorus flame retardant.

[0087] The composition formulation in this embodiment is the same as that in Example 2.

[0088] Example 15 The preparation method of the silicon-phosphorus flame retardant in this embodiment is as follows: Phenyltrimethoxysilane and vinyltriethoxysilane were subjected to a hydrolysis-condensation reaction in the presence of tetrahydrofuran, deionized water, and tetramethylammonium hydroxide. The molar ratio of phenylsilane to vinylsilane was 0.5, the mass ratio of tetrahydrofuran to water was 4:1, the total mass of silane coupling agent accounted for 30% of the total mass of tetrahydrofuran and deionized water, and the amount of catalyst added was 1% of the total mass of silane. The reaction was carried out at room temperature for 24 h to obtain a phenyl-containing vinyl ladder-shaped silsesquioxane. DOPO was grafted with the above-mentioned silsesquioxane in THF under the initiation of azobisisobutyronitrile; wherein the molar ratio of DOPO to vinyl group was 0.3, the initiator was 0.1% of the mass of silsesquioxane, the mass ratio of reactant to THF was 1:2, and the reaction was carried out at 80°C for 8 hours to obtain a silicon-phosphorus flame retardant.

[0089] The composition formulation in this embodiment is the same as that in Example 2.

[0090] Example 16 The preparation method of the silicon-phosphorus flame retardant in this embodiment is as follows: Phenyltrichlorosilane and vinyltrimethoxysilane were subjected to a hydrolysis-condensation reaction in the presence of tetrahydrofuran, deionized water, and tetramethylammonium hydroxide. The molar ratio of phenylsilane to vinylsilane was 1.0, the mass ratio of tetrahydrofuran to water was 1:1, the total mass of silane coupling agent accounted for 50% of the total mass of tetrahydrofuran and deionized water, and the amount of catalyst added was 3% of the total mass of silane. The reaction was carried out at room temperature for 36 h to obtain a phenyl-containing vinyl ladder-shaped silsesquioxane. DOPO was grafted with the above-mentioned silsesquioxane in THF and initiated by azobisisobutyronitrile; wherein the molar ratio of DOPO to vinyl group was 0.8, the initiator was 0.3% of the mass of silsesquioxane, the mass ratio of reactant to THF was 1:4, and the reaction was carried out at 100°C for 24 h to obtain a silicon-phosphorus flame retardant.

[0091] The composition formulation in this embodiment is the same as that in Example 2.

[0092] Example 17 Based on the same inventive concept, the present invention also provides a flame-retardant epoxy resin composition, comprising, by weight parts: 80-100 parts of epoxy resin; 80-100 parts of curing agent; 1-15 parts of the silicon-phosphorus flame retardant described in any one of Examples 1-11; Toughening agent 5-25 parts; Accelerator 1-5 parts.

[0093] Preferably, the epoxy resin is one or more of bisphenol A glycidyl ether, bisphenol F glycidyl ether, and hydantoin epoxy resin.

[0094] Preferably, the epoxy value of the epoxy resin is 0.4 to 0.7.

[0095] Preferably, the curing agent is one or more of tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, methylhexahydrophthalic anhydride, and methyltetrahydrophthalic anhydride.

[0096] Preferably, the accelerator is one or more of phenol, imidazole, and dimethylaminoaniline.

[0097] Preferably, the toughening agent is one or more of nano-silica, nano-alumina, hydroxyapatite, and core-shell rubber.

[0098] Preferably, at 25°C, the overall viscosity of the flame-retardant epoxy resin composition is 5000 mPa·s to 8000 mPa·s.

[0099] A typical implementation ratio is as follows: calculated by mass parts, including: Bisphenol A glycidyl ether (epoxide value 0.5) 90 parts; methyltetrahydrophthalic anhydride 90 parts; silicon-phosphorus flame retardant obtained in Example 1 10 parts; nano silica 15 parts; imidazole 3 parts.

[0100] Example 18 (Investigation of lower limit of epoxy resin, upper limit of flame retardant, and bisphenol F type) A flame-retardant epoxy resin composition, by weight parts, comprises: 80 parts of bisphenol F glycidyl ether (epoxy value 0.6); 80 parts of hexahydrophthalic anhydride; 15 parts of the silicophosphorus flame retardant obtained in Example 1; 10 parts of core-shell rubber; and 2 parts of phenol.

[0101] Example 19 (Investigation of upper limit of epoxy resin, lower limit of flame retardant, and high epoxy value of hydantoin type) A flame-retardant epoxy resin composition, by weight parts, comprises: 100 parts of hydantoin epoxy resin (epoxy value 0.7); 100 parts of tetrahydrophthalic anhydride; 1 part of the silicon-phosphorus flame retardant obtained in Example 1; 25 parts of nano-alumina; and 5 parts of dimethylaminoaniline.

[0102] Example 20 (Investigation of the lower limits of epoxy resin low epoxy value, multi-component curing agent, and toughening agent) A flame-retardant epoxy resin composition, by weight parts, comprises: 100 parts of bisphenol A glycidyl ether (epoxy value 0.4); 50 parts of methyl hexahydrophthalic anhydride and 50 parts of methyl nadic anhydride (total 100 parts); 5 parts of the silicophosphorus flame retardant obtained in Example 1; 5 parts of hydroxyapatite; 1 part of imidazole and 1 part of phenol (total 2 parts).

[0103] Example 21 (Examination of multi-component epoxy resin compound and multi-component toughening agent compound) A flame-retardant epoxy resin composition, by weight parts, comprises: 50 parts of bisphenol A glycidyl ether (epoxy value 0.5), 40 parts of hydantoin epoxy resin (epoxy value 0.6) (total 90 parts); 90 parts of methyl nadic anhydride; 8 parts of the silicon-phosphorus flame retardant obtained in Example 1; 10 parts of nano silica; 5 parts of core-shell rubber (total 15 parts); and 3 parts of dimethylaminoaniline.

[0104] Example 22 (Examining the lower limit of curing agent and the upper limit of accelerator) A flame-retardant epoxy resin composition, by weight parts, comprises: 85 parts of bisphenol F glycidyl ether (epoxy value 0.5); 50 parts of hexahydrophthalic anhydride and 30 parts of tetrahydrophthalic anhydride (total 80 parts); 12 parts of the silicophosphorus flame retardant obtained in Example 1; 5 parts of nano-alumina and 10 parts of hydroxyapatite (total 15 parts); 2 parts of imidazole and 3 parts of dimethylaminoaniline (total 5 parts).

[0105] Example 23 (Investigating the upper limit of toughening agents and multi-component accelerators) A flame-retardant epoxy resin composition, by weight parts, comprises: 95 parts of bisphenol A glycidyl ether (epoxy value 0.6); 95 parts of methyltetrahydrophthalic anhydride; 7 parts of the silicon-phosphorus flame retardant obtained in Example 1; 15 parts of core-shell rubber; 10 parts of nano-silica (total 25 parts); 2 parts of phenol; and 2 parts of dimethylaminoaniline (total 4 parts).

[0106] Example 24 (Comprehensive Median Combination) A flame-retardant epoxy resin composition, by weight parts, comprises: 40 parts of bisphenol F glycidyl ether (epoxy value 0.5), 50 parts of bisphenol A glycidyl ether (epoxy value 0.5) (total 90 parts); 70 parts of methylhexahydrophthalic anhydride, 20 parts of methyltetrahydrophthalic anhydride (total 90 parts); 14 parts of the silicophosphorus flame retardant obtained in Example 1; and 20 parts of hydroxyapatite. Imidazole 1.5 parts, phenol 1.5 parts (total 3 parts).

[0107] Example 25 Based on the same inventive concept, the present invention also provides the application of the flame-retardant epoxy resin composition as described in any of Examples 17-24 in fiber impregnation molding products.

[0108] Preferably, the fiber-impregnated and wound parts are heat-cured at a temperature of 80~100℃ for 2~4 hours, followed by treatment at 120~130℃ for 2~3 hours.

[0109] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of the claims of the present invention.

Claims

1. A silicon-phosphorus flame retardant, characterized in that, It has the following chemical structural formula: 。 2. The method for preparing a silicon-phosphorus flame retardant as described in claim 1, characterized in that, Includes the following steps: A phenyl silane coupling agent and a vinyl silane coupling agent are subjected to a hydrolysis-condensation reaction in the presence of a solvent, deionized water and a catalyst to obtain a phenyl-containing vinyl ladder-shaped silsesquioxane. The phenyl-containing vinyl ladder silsesquioxane was grafted with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in the presence of an initiator to obtain the silicon-phosphorus flame retardant.

3. The method for preparing a silicon-phosphorus flame retardant as described in claim 2, characterized in that, The chemical structural formula of the vinyl ladder-shaped silsesquioxane is as follows: 。 4. The method for preparing a silicon-phosphorus flame retardant as described in claim 2, characterized in that, The phenylsilane coupling agent is one of phenyltrimethoxysilane, phenyltrichlorosilane, and phenyltriethoxysilane.

5. The method for preparing a silicon-phosphorus flame retardant as described in claim 2, characterized in that, The vinyl silane coupling agent is one of vinyltrimethoxysilane, vinyltrichlorosilane, and vinyltriethoxysilane.

6. The method for preparing a silicon-phosphorus flame retardant as described in claim 2, characterized in that, The molar ratio of the phenylsilane coupling agent to the vinylsilane coupling agent is 0.5~1.

7. The method for preparing a silicon-phosphorus flame retardant as described in claim 2, characterized in that, The solvent is tetrahydrofuran, and the mass ratio of tetrahydrofuran to water is 4:1 to 1:

1.

8. The method for preparing a silicon-phosphorus flame retardant as described in claim 2, characterized in that, The catalyst is tetramethylammonium hydroxide, and its addition amount is 1% to 3% of the total mass of the silane coupling agent.

9. The method for preparing a silicon-phosphorus flame retardant as described in claim 2, characterized in that, The hydrolysis-condensation reaction takes 24-36 hours at room temperature.

10. The method for preparing a silicon-phosphorus flame retardant as described in claim 2, characterized in that, The molar ratio of vinyl groups in the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to the phenyl-containing vinyl ladder silsesquioxane is 0.3 to 0.

8.

11. The method for preparing a silicon-phosphorus flame retardant as described in claim 2, characterized in that, The initiator is azobisisobutyronitrile, and its addition amount is 0.1% to 0.3% of the mass of the phenyl-containing vinyl ladder silsesquioxane.

12. The method for preparing a silicon-phosphorus flame retardant as described in claim 2, characterized in that, The total mass of the phenylsilane coupling agent and the vinylsilane coupling agent accounts for 30% to 50% of the total mass of tetrahydrofuran and deionized water.

13. The method for preparing a silicon-phosphorus flame retardant as described in claim 2, characterized in that, The grafting reaction is carried out in tetrahydrofuran, with a reactant-to-tetrahydrofuran mass ratio of 1:2 to 1:

4.

14. The method for preparing a silicon-phosphorus flame retardant as described in claim 13, characterized in that, The grafting reaction is carried out at a temperature of 80℃~100℃ for 8~24 hours.

15. A flame-retardant epoxy resin composition, characterized in that, Calculated by parts by weight, including: 80-100 parts of epoxy resin; 80-100 parts of curing agent; 1-15 parts of the silicon-phosphorus flame retardant according to claim 1; Toughening agent 5-25 parts; Accelerator 1-5 parts.

16. The flame-retardant epoxy resin composition according to claim 15, characterized in that, The epoxy resin is one or more of bisphenol A glycidyl ether, bisphenol F glycidyl ether, and hydantoin epoxy resin.

17. The flame-retardant epoxy resin composition according to claim 15, characterized in that, The epoxy value of the epoxy resin is 0.4 to 0.

7.

18. The flame-retardant epoxy resin composition as described in claim 15, characterized in that, The curing agent is one or more of tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylnadic anhydride, methylhexahydrophthalic anhydride, and methyltetrahydrophthalic anhydride.

19. The flame-retardant epoxy resin composition according to claim 15, characterized in that, The accelerator is one or more of phenol, imidazole, and dimethylaminobenzylamine.

20. The flame-retardant epoxy resin composition according to claim 15, characterized in that, The toughening agent is one or more of nano-silica, nano-alumina, hydroxyapatite, and core-shell rubber.

21. The flame-retardant epoxy resin composition according to claim 15, characterized in that, At 25°C, the overall viscosity of the flame-retardant epoxy resin composition is 5000 mPa·s to 8000 mPa·s.

22. The use of a flame-retardant epoxy resin composition as described in any one of claims 15-21 in fiber impregnation molded products.

23. The application as described in claim 22, characterized in that, For fiber-impregnated and wound parts, heat curing is performed at a temperature of 80~100℃ for 2~4 hours, followed by treatment at 120~130℃ for 2~3 hours.

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