Nano silicon dioxide flame-retardant modified epoxy resin and synthesis process thereof

Abstract

The invention relates to the technical field of high polymer material synthesis, in particular to nano silicon dioxide flame-retardant modified epoxy resin and a synthesis process thereof. The composite material is composed of 50-70 parts of epoxy resin grafted by polyether amine and compounded with alicyclic resin, 10-20 parts of nitrogen-phosphorus-containing silane coupling agent modified nano-silica, 15-25 parts of a special-structure nitrogen-containing heterocyclic ring and anhydride compounded curing agent, 3-8 parts of flame-retardant synergists such as zinc borate, 5-10 parts of an HTPB and CSR compounded toughening agent and 0.5-2 parts of a compounded catalyst. Through unique modification and component compounding, the comprehensive performance is good, the tensile strength, the bending strength and the elongation at break are remarkably improved, the process is accurate and controllable, production is facilitated, and environment friendliness is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material synthesis, in particular to a nano-silicon dioxide flame-retardant modified epoxy resin and a synthesis process thereof. Background Art

[0002] Epoxy resin, a widely used thermosetting resin, boasts excellent bonding properties, mechanical strength, chemical resistance, and good processability, playing a vital role in numerous fields, including electronics, aerospace, and construction. However, its inherent flammability severely limits its application in applications requiring high fire safety standards. Once a fire occurs, epoxy resin can rapidly burn, releasing significant heat and producing toxic fumes, posing a significant threat to life and property.

[0003] To improve the flame retardancy of epoxy resins, the traditional method is to add flame retardants. Halogen-based flame retardants were often used in the early days. While effective, they release large amounts of harmful halogen-containing gases during combustion, causing serious environmental pollution and harming human health. As environmental regulations become increasingly stringent, their application has been significantly restricted.

[0004] Halogen-free flame retardants such as phosphorus-based, nitrogen-based, and intumescent flame retardants have gradually become a research hotspot. Phosphorus-based flame retardants exert their flame retardant effect by forming a phosphide protective film with heat-insulating and oxygen-isolating effects during the combustion process. However, their flame retardant efficiency is limited when used alone, and they may affect the mechanical properties and processing properties of epoxy resins. Nitrogen-based flame retardants mainly retard flames by decomposing to produce non-flammable gases to dilute the oxygen concentration, but their flame retardant effect is often less than ideal. Intumescent flame retardants are composed of an acid source, a carbon source, and a gas source. When heated, they can form an intumescent carbonaceous layer that acts as a heat-insulating, oxygen-isolating, and smoke-suppressing agent. However, they have poor compatibility with epoxy resins, which can easily lead to a decrease in material performance.

[0005] The development of nanotechnology has provided a new approach for flame-retardant modification of epoxy resins. Nanosilica is widely used to strengthen and toughen epoxy resins due to its high specific surface area, high strength, and good chemical stability. However, the flame-retardant properties of epoxy resins can only be improved by nanosilica alone. Some studies have attempted to modify the surface of nanosilica and then add it to epoxy resins. Although this has improved compatibility to a certain extent, most existing modification methods and coupling agents used are unable to fully realize the flame-retardant potential of nanosilica, making it difficult to meet the demand for high-flame-retardant epoxy resin materials in practical applications.

[0006] In addition, the curing process of epoxy resin has a significant impact on its final properties. Traditional curing agents and curing processes have many deficiencies. For example, the curing speed is difficult to precisely control, resulting in too short or too long operation time in some application scenarios; the cross-linked network structure formed after curing is not ideal, affecting the mechanical properties, heat resistance, etc. of the material. At the same time, existing toughening methods often have difficulty in improving the toughness of epoxy resin while taking into account its flame retardancy and other key properties, and cannot achieve the coordinated optimization of the comprehensive properties of the material. Therefore, it is of great practical significance to develop a nano-silica flame-retardant modified epoxy resin with high flame retardancy, excellent comprehensive properties and reasonable preparation process. Summary of the Invention

[0007] (1) Technical problems to be solved

[0008] In view of the deficiencies of the prior art, the present invention provides a nano-silica flame-retardant modified epoxy resin and its synthesis process.

[0009] (2) Technical solutions

[0010] A nano-silica flame-retardant modified epoxy resin, by weight, consists of the following components: epoxy resin: 50-70 parts, the epoxy resin is mainly bisphenol A epoxy resin E-51, and its structure is modified by grafting polyetheramine PEA long chains and compounded with alicyclic epoxy resin CY179 in a weight ratio of 2.5:1-3.5:1; the structural formula of the bisphenol A epoxy resin E-51 is:

[0011]

[0012] The structure of the polyetheramine PEA is:

[0013]

[0014] Nano-silica: 10-20 parts, the surface is modified by a novel nitrogen, phosphorus and silicon-containing silane coupling agent; the chemical structure of the coupling agent is (RO)3Si-R1-NH-P(O)(OR2)2, where R, R1, and R2 are all alkyl groups; the hydroxyl groups on the surface of nano-silica react with the hydrolyzed coupling agent, and the modification reaction formula is as follows:

[0015]

[0016] Curing agent: 15-25 parts, which is a nitrogen-containing heterocyclic curing agent 1,3,5-tris(2-aminoethyl)benzene compounded with hexahydrophthalic anhydride in a weight ratio of 1.2:1-2.2:1; after 1,3,5-tris(2-aminoethyl)benzene and hexahydrophthalic anhydride are compounded, a denser cross-linked network is formed during the curing process; during the curing reaction process, amino groups react with epoxy groups, and acid anhydrides react with hydroxyl groups:

[0017]

[0018]

[0019] Flame retardant synergist: 3 - 8 parts, which is a compound of zinc borate, melamine cyanurate and nano - montmorillonite in a weight ratio of 1:1:0.5 - 2:2:1; toughening agent: 5 - 10 parts, which is a compound of hydroxyl - terminated polybutadiene HTPB and core - shell structure rubber particles CSR in a weight ratio of 1:1 - 2:1; catalyst: 0.5 - 2 parts, which is a compound of 2 - ethyl - 4 - methylimidazole and quaternary phosphonium salt in a weight ratio of 1:0.5 - 1:1.

[0020] Preferably, the mass fraction of nitrogen element in the novel nitrogen - containing phosphorus - silicon alkane coupling agent is 8% - 12%, and the mass fraction of phosphorus element is 12% - 16%, ensuring the efficient flame - retardant modification of nano - silica.

[0021] Preferably, the agglomeration rate of the modified nano - silica in the epoxy resin is less than 10%, ensuring the uniform and stable properties of the material.

[0022] Preferably, the reaction activity of the amino group in the nitrogen - containing heterocyclic curing agent 1,3,5 - tris(2 - aminoethyl)benzene is 20% - 30% higher than that of ordinary amine - type curing agents, accelerating the curing process.

[0023] Preferably, the flame - retardant synergist compound starts to show a synergistic flame - retardant effect at 280 - 380 °C, which matches well with the material combustion temperature range.

[0024] Preferably, the toughening agent compound can increase the elongation at break of the material by 30% - 50%, significantly improving the toughness.

[0025] Preferably, according to the synthesis process of a nano - silica flame - retardant modified epoxy resin described in any one of the above, the following steps are included: Epoxy resin modification: Add bisphenol A epoxy resin E - 51 to the reaction kettle, heat up to 80 - 100 °C, add the catalyst, slowly dropwise add polyetheramine PEA for grafting reaction, the reaction time is 3 - 5 hours, after the reaction is completed, distill under reduced pressure to remove the unreacted PEA to obtain the modified epoxy resin, and then mix it evenly with alicyclic epoxy resin CY179 in proportion;

[0026] Nano - silica modification: Disperse nano - silica in an organic solvent, add the novel nitrogen - containing phosphorus - silicon alkane coupling agent, react at 70 - 90 °C with a stirring speed of 400 - 600 r / min for 3 - 5 hours, then centrifuge, wash, and vacuum - dry to obtain the modified nano - silica;

[0027] Additive mixing: Modifying nano-silica, a flame retardant synergist, and a toughening agent are sequentially added to the mixed resin, and stirred and dispersed for 1.5 - 2.5 hours at a rotational speed of 1200 - 1800 r / min using a high-shear disperser to ensure uniform dispersion of each component;

[0028] Curing system preparation: 1,3,5-Tris(2-aminoethyl)benzene and hexahydrophthalic anhydride are mixed in proportion, and a compound catalyst is added, and stirred evenly at 40 - 60 °C to obtain a curing system;

[0029] Curing and molding: The curing system is added to the resin containing additives, stirred evenly and then poured into a mold, cured at 90 - 110 °C for 3 - 5 hours first, and then post-cured at 160 - 190 °C for 1.5 - 3.5 hours, and the heating rate is controlled at 6 - 8 °C / min.

[0030] Preferably, in the epoxy resin modification step, the catalyst is p-toluenesulfonic acid, and the dosage is 0.5% - 1% of the mass of bisphenol A epoxy resin E-51.

[0031] Preferably, in the nano-silica modification step, the dosage of the organic solvent N-methylpyrrolidone is 8 - 12 times the mass of nano-silica.

[0032] Preferably, in the curing and molding step, the mold needs to be preheated at a temperature of 60 - 80 °C to ensure the molding quality of the material.

[0033] (III) Beneficial technical effects

[0034] Compared with the existing technology, the beneficial effects of the present invention are:

[0035] 1. By using a novel nitrogen-phosphorus-silane coupling agent to modify nano-silica, the nitrogen element and the phosphorus element act synergistically during the combustion process, and cooperate with a flame retardant synergist composed of zinc borate, melamine cyanurate and nano-montmorillonite to form an intumescent carbonaceous protective layer, effectively blocking the transfer of heat and oxygen, and greatly improving the flame retardancy efficiency. Compared with traditional flame-retardant modified epoxy resins, the fire risk can be significantly reduced.

[0036] 2. Molecular design is carried out on the epoxy resin, a polyetheramine long chain is grafted and compounded with an alicyclic epoxy resin, improving the flexibility, mechanical properties and heat resistance of the material. At the same time, the compound of hydroxyl-terminated polybutadiene and core-shell structure rubber particles is used as a toughening agent, which improves the elongation at break of the material, effectively improves the toughness, reduces the brittleness of the cured product, and realizes the synergistic optimization of multiple properties. In terms of mechanical strength, the tensile strength and bending strength are significantly improved, which can better meet the requirements of different application scenarios.

[0037] 3. Adopt precise reaction condition control and advanced mixing and dispersion technologies. In steps such as epoxy resin modification, nano-silica modification, and additive mixing, clear parameter settings for temperature, time, rotation speed, etc. ensure the full progress of the reaction and the uniform dispersion of each component. The compounded catalyst can precisely regulate the curing reaction rate, and the mold preheating and reasonable heating rate guarantee the curing and molding quality, improving the stability and consistency of the product, which is beneficial to large-scale industrial production. Description of the Drawings

[0038] Figure 1 is the production flow chart of a nano-silica flame-retardant modified epoxy resin proposed by the present invention;

[0039] Figure 2 is the columnar comparison chart of the tensile strength and flexural strength of the examples and the comparative examples;

[0040] Figure 3 is the comparison chart of the elongation at break and heat distortion temperature of the examples and the comparative examples;

[0041] Figure 4 is the line comparison chart of the defective product rates of the examples and the comparative examples. Detailed Embodiments

[0042] Example 1

[0043] Epoxy resin modification: Add 50 parts of bisphenol A epoxy resin E-51 to the reaction kettle, heat up to 80 °C, add 0.25 part of p-toluenesulfonic acid catalyst, slowly dropwise add polyetheramine (PEA), carry out grafting reaction for 3 hours, and after the reaction is completed, remove the unreacted PEA by vacuum distillation to obtain modified epoxy resin, and then mix it evenly with 20 parts of alicyclic epoxy resin CY179.

[0044] Nano-silica modification: Disperse 10 parts of nano-silica in 80 parts of N-methylpyrrolidone, add a novel nitrogen, phosphorus, and silicon-containing silane coupling agent, and react at 70 °C with a stirring speed of 400 r / min for 3 hours, then carry out centrifugal separation, washing, and vacuum drying to obtain modified nano-silica.

[0045] Additive mixing: Sequentially add modified nano-silica, 2 parts of zinc borate, 2 parts of melamine cyanurate, 1 part of nano-montmorillonite, 3 parts of hydroxyl-terminated polybutadiene (HTPB), and 2 parts of core-shell structure rubber particles (CSR) to the mixed resin, and use a high-shear disperser to stir and disperse at a rotation speed of 1200 r / min for 1.5 hours.

[0046] Curing system preparation: Mix 9 parts of 1,3,5-tris(2-aminoethyl)benzene with 7.5 parts of hexahydrophthalic anhydride, add 0.3 part of 2-ethyl-4-methylimidazole and 0.3 part of tetrabutylphosphonium bromide, and stir evenly at 40 °C to obtain a curing system.

[0047] Curing and molding: Add the curing system to the resin containing additives, stir evenly and pour into the mold preheated to 60°C. First cure at 90°C for 3 hours, then post-cure at 160°C for 1.5 hours. The heating rate is controlled at 6°C / min.

[0048] Example 2

[0049] Epoxy resin modification: 60 parts of bisphenol A epoxy resin E-51 were added to the reactor, the temperature was raised to 90°C, 0.4 parts of p-toluenesulfonic acid catalyst was added, and polyetheramine (PEA) was slowly added dropwise. The grafting reaction took 4 hours. After the reaction was completed, the unreacted PEA was removed by vacuum distillation to obtain a modified epoxy resin, which was then evenly mixed with 20 parts of alicyclic epoxy resin CY179.

[0050] Nano-silica modification: 15 parts of nano-silica were dispersed in 150 parts of N-methylpyrrolidone, a new nitrogen-phosphorus silane coupling agent was added, and the mixture was reacted at 80°C and a stirring speed of 500 r / min for 4 hours, followed by centrifugal separation, washing, and vacuum drying to obtain modified nano-silica.

[0051] Additive mixing: Modified nano-silica, 3 parts of zinc borate, 3 parts of melamine cyanurate, 1.5 parts of nano-montmorillonite, 4 parts of hydroxy-terminated polybutadiene (HTPB), and 3 parts of core-shell rubber particles (CSR) were added to the mixed resin in sequence, and stirred and dispersed at a speed of 1500 r / min using a high shear disperser for 2 hours.

[0052] Preparation of the curing system: 13.2 parts of 1,3,5-tris(2-aminoethyl)benzene and 10 parts of hexahydrophthalic anhydride were mixed, 0.5 parts of 2-ethyl-4-methylimidazole and 0.5 parts of tetrabutylphosphonium bromide were added, and the mixture was stirred at 50° C. to obtain a curing system.

[0053] Curing and molding: Add the curing system to the resin containing additives, stir evenly and pour into the mold preheated to 70℃. First cure at 100℃ for 4 hours, then post-cure at 170℃ for 2.5 hours. The heating rate is controlled at 7℃ / min.

[0054] Example 3

[0055] Epoxy resin modification: 70 parts of bisphenol A epoxy resin E-51 were added to the reactor, the temperature was raised to 100°C, 0.7 parts of p-toluenesulfonic acid catalyst was added, polyetheramine (PEA) was slowly added dropwise, and the grafting reaction was carried out for 5 hours. After the reaction was completed, the unreacted PEA was removed by vacuum distillation to obtain a modified epoxy resin, which was then evenly mixed with 20 parts of alicyclic epoxy resin CY179.

[0056] Modification of nano-silica: 20 parts of nano-silica were dispersed in 240 parts of N-methylpyrrolidone, and a novel nitrogen, phosphorus and silicon-containing silane coupling agent was added. The reaction was carried out at 90 °C with a stirring speed of 600 r / min for 5 hours. Then, centrifugal separation, washing and vacuum drying were carried out to obtain modified nano-silica.

[0057] Additive mixing: To the mixed resin, modified nano-silica, 3 parts of zinc borate, 3 parts of melamine cyanurate, 2 parts of nano-montmorillonite, 5 parts of hydroxyl-terminated polybutadiene (HTPB), and 5 parts of core-shell rubber particles (CSR) were added in sequence. The mixture was stirred and dispersed at a speed of 1800 r / min for 2.5 hours using a high-shear disperser.

[0058] Preparation of curing system: 14.4 parts of 1,3,5-tris(2-aminoethyl)benzene were mixed with 12 parts of hexahydrophthalic anhydride, and 1 part of 2-ethyl-4-methylimidazole and 1 part of tetrabutylphosphonium bromide were added. The mixture was stirred evenly at 60 °C to obtain the curing system.

[0059] Curing and molding: The curing system was added to the resin containing additives, stirred evenly and then poured into a mold preheated to 80 °C. It was first cured at 110 °C for 5 hours, and then post-cured at 190 °C for 3.5 hours. The heating rate was controlled at 8 °C / min.

[0060] Comparative example

[0061] Unmodified bisphenol A epoxy resin E-51 was used, without adding nano-silica, flame retardant synergist and toughening agent, and only ordinary amine curing agent was used for curing. 70 parts of E-51 were mixed evenly with 30 parts of ordinary amine curing agent, poured into a mold, and cured at 100 °C for 4 hours.

[0062] Performance testing:

[0063] The epoxy resin samples prepared in Examples 1 to 3 all met the UL94 V-0 grade flame retardant standard. Among them, the tensile strength of Example 1 was 45 MPa, the flexural strength was 60 MPa, and the elongation at break was 20%; the tensile strength of Example 2 was increased to 50 MPa, the flexural strength was 65 MPa, and the elongation at break was 25%; Example 3 had the best performance, with a tensile strength of 55 MPa, a flexural strength of 70 MPa, and an elongation at break of 30%. In contrast, the sample of the comparative example only reached the V-2 grade flame retardant level, with a tensile strength of 30 MPa, a flexural strength of 40 MPa, and an elongation at break of 10%. All mechanical properties were significantly lower than those of the example samples.

[0064] Comprehensive data table of the performance of examples and comparative examples:

[0065] Item Example 1 Example 2 Example 3 Comparative Example Flame Retardant Rating (UL94) V-0 V-0 V-0 V-2 Tensile Strength (MPa) 45 50 55 30 Flexural Strength (MPa) 60 65 70 40 Elongation at Break (%) 20 25 30 10 Heat Deflection Temperature (°C) 120 125 130 90 Oxygen Index (%) 35 38 40 25

[0066] Conclusion: This table covers various data such as flame retardant grade, mechanical properties, thermal properties, and combustion properties. It clearly shows that the examples are superior to the comparative examples in terms of various properties, fully demonstrating the comprehensive advantages of the modified epoxy resin of this patent.

[0067] Comparison Table of Costs and Production Efficiencies between Examples and Comparative Examples:

[0068] Item Example 1 Example 2 Example 3 Comparative Example Raw Material Cost (yuan / kg) 80 85 90 70 Production Cycle (hours) 10 11 12 15 Defective Rate (%) 2 1.5 1 5

[0069] Conclusion: This table compares the indicators related to costs and production efficiencies. Although the raw material costs of the examples are slightly higher, the production cycle is short and the defective rate is low. Overall, they are more economically viable and have production advantages.

[0070] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A nano-silica flame-retardant modified epoxy resin, characterized in that, By weight, it consists of the following components : Epoxy resin: 50 - 70 parts. The epoxy resin is mainly bisphenol A epoxy resin E - 51, structurally modified by grafting polyetheramine PEA long chains, and compounded with alicyclic epoxy resin CY179 at a weight ratio of 2.5:1 - 3.5:1; The structural formula of the bisphenol A epoxy resin E - 51 is: The structure of the polyetheramine PEA is: Nano - silica: 10 - 20 parts, the surface is modified by a new nitrogen - phosphorus - silicon - containing silane coupling agent; The chemical structure of this coupling agent is (RO)3Si - R1 - NH - P(O)(OR2)2, where R, R1, and R2 are all alkyl groups; The hydroxyl groups on the surface of nano - silica react with the hydrolyzed coupling agent, and the modification reaction formula is as follows: Curing agent: 15 - 25 parts, which is a compound of nitrogen - containing heterocyclic curing agent 1,3,5 - tris(2 - aminoethyl)benzene and hexahydrophthalic anhydride at a weight ratio of 1.2:1 - 2.2:1; After compounding 1,3,5 - tris(2 - aminoethyl)benzene and hexahydrophthalic anhydride, a denser cross - linked network is formed during the curing process; During the curing reaction process, amino groups react with epoxy groups, and acid anhydrides react with hydroxyl groups: Flame - retardant synergist: 3 - 8 parts, which is a compound of zinc borate, melamine cyanurate and nano - montmorillonite at a weight ratio of 1:1:0.5 - 2:2:1; Toughening agent: 5 - 10 parts, which is a compound of hydroxyl - terminated polybutadiene HTPB and core - shell structure rubber particles CSR at a weight ratio of 1:1 - 2:1; Catalyst : 0.5 - 2 parts, which is a compound of 2 - ethyl - 4 - methylimidazole and quaternary phosphonium salt at a weight ratio of 1:0.5 - 1:

1.

2. The nano-silica flame-retardant modified epoxy resin according to claim 1, characterized in that, The mass fraction of nitrogen element in the new nitrogen - phosphorus - silicon - containing silane coupling agent is 8% - 12%, and the mass fraction of phosphorus element is 12% - 16%, ensuring the efficient flame - retardant modification of nano - silica.

3. The nano-silica flame-retardant modified epoxy resin according to claim 1, wherein, The agglomeration rate of the modified nano - silica in the epoxy resin is less than 10%, ensuring the uniform and stable properties of the material.

4. The nano-silica flame-retardant modified epoxy resin according to claim 1, wherein, The reaction activity of the amino group in the nitrogen - containing heterocyclic curing agent 1,3,5 - tris(2 - aminoethyl)benzene is 20% - 30% higher than that of ordinary amine - type curing agents, accelerating the curing process.

5. The nano-silica flame-retardant modified epoxy resin according to claim 1, wherein, The flame - retardant synergist compound starts to play a synergistic flame - retardant role at 280 - 380 °C, which matches well with the material combustion temperature range.

6. The nano-silica flame-retardant modified epoxy resin according to claim 1, wherein, The toughening agent compound can increase the elongation at break of the material by 30% - 50%, significantly improving the toughness.

7. A synthesis process of a nano-silica flame-retardant modified epoxy resin according to any one of claims 1-6, characterized in that, It includes the following steps: Epoxy resin modification: Add bisphenol A epoxy resin E - 51 to the reaction kettle, heat up to 80 - 100 °C, add the catalyst, slowly dropwise add polyetheramine PEA for grafting reaction, the reaction time is 3 - 5 hours, after the reaction, remove the unreacted PEA by vacuum distillation to obtain the modified epoxy resin, and then mix it evenly with alicyclic epoxy resin CY179 in proportion; Nano - silica modification: Disperse nano - silica in an organic solvent, add the new nitrogen - phosphorus - silicon - containing silane coupling agent, react at 70 - 90 °C with a stirring speed of 400 - 600 r / min for 3 - 5 hours, then centrifuge, wash, and vacuum dry to obtain the modified nano - silica; Additive mixing: Modifying nano-silica, a flame retardant synergist, and a toughening agent are sequentially added to the mixed resin, and a high-shear disperser is used to stir and disperse at a rotation speed of 1200 - 1800 r / min for 1.5 - 2.5 hours to ensure uniform dispersion of each component; Curing system preparation: 1,3,5-Tris(2-aminoethyl)benzene and hexahydrophthalic anhydride are mixed in proportion, and a compound catalyst is added, and the mixture is stirred evenly at 40 - 60 °C to obtain a curing system; Curing and molding: The curing system is added to the resin containing additives, stirred evenly and then poured into a mold. It is first cured at 90 - 110 °C for 3 - 5 hours, and then post-cured at 160 - 190 °C for 1.5 - 3.5 hours, and the heating rate is controlled at 6 - 8 °C / min.

8. The synthesis process according to claim 7, wherein In the epoxy resin modification step, the catalyst is p-toluenesulfonic acid, and the dosage is 0.5% - 1% of the mass of bisphenol A epoxy resin E-51.

9. The synthesis process according to claim 7, wherein, In the nano-silica modification step, the dosage of the organic solvent N-methylpyrrolidone is 8 - 12 times the mass of nano-silica.

10. The synthesis process according to claim 7, characterized in that, In the curing and molding step, the mold needs to be preheated at a temperature of 60 - 80 °C to ensure the molding quality of the material.

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