A phosphorus-containing flame retardant for epoxy resins and a method for preparing the same

Abstract

The application discloses a phosphorus-containing flame retardant for epoxy resin and a preparation method thereof, and belongs to the flame retardant field. The preparation method of the phosphorus-containing flame retardant comprises the following steps: mixing diphenyl phosphine oxide and 4-aminoacetophenone, and heating to a reaction temperature; then adding a catalyst, and performing heat preservation reaction; and obtaining the phosphorus-containing flame retardant after the reaction is completed. The phosphorus-containing flame retardant designed and synthesized by the application contains a primary amine group and a phosphorus-containing flame retardant group. The primary amine group can provide protons to react with an epoxy group to achieve the function of curing and cross-linking. The carbon layer and free radicals generated by the thermal decomposition of the phosphorus-containing flame retardant group can achieve the function of flame retardation. The primary amine is located in the polymer molecular chain after curing, and there is no migration problem. Meanwhile, the epoxy resin flame retardant material with the advantages of low odor, low toxicity, good stability, good hardness and the like can be obtained by using the phosphorus-containing flame retardant.

Description

Technical Field

[0001] This invention relates to the field of flame retardants, and more specifically to a phosphorus-containing flame retardant for epoxy resins, and a method for preparing the phosphorus-containing flame retardant. Background Technology

[0002] Epoxy resin is an important polymer material widely used in industrial applications such as coatings, adhesives, and composite materials. However, epoxy resin faces challenges in flame retardancy during application. Flame retardancy is a key performance indicator for materials, especially under high-temperature conditions, such as in the event of a fire. Reactive flame retardants are low-molecular-weight compounds with terminal reactive functional groups, possessing the dual functions of curing crosslinking and flame retardancy.

[0003] Reactive phosphorus-containing flame retardants achieve their effect by reacting with epoxy resin through reactive functional groups at their ends, thus allowing the flame retardant molecules to integrate into the epoxy resin backbone. The flame retardant molecules first decompose at high temperatures, promoting the carbonization of the material and forming a stable char layer. When the material is heated, the phosphorus-containing flame retardant decomposes and releases phosphorus compounds, which react at high temperatures to form char. Once the char layer is formed, it effectively isolates the flame from oxygen, preventing the spread of fire. It can also produce some non-flammable gases, such as ammonia and ammonia compounds. These gases help dilute the oxygen in the combustion zone during a fire, reducing the fire's intensity and inhibiting its spread. Summary of the Invention

[0004] The purpose of this invention is to provide a phosphorus-containing flame retardant for epoxy resins, and a method for preparing the phosphorus-containing flame retardant.

[0005] The technical solution adopted in this invention is:

[0006] A phosphorus-containing flame retardant for epoxy resins, which is a compound having the following structure:

[0007]

[0008] The preparation method of the phosphorus-containing flame retardant as described above includes the following steps:

[0009] (1) Diphenylphosphine oxide and 4-aminoacetophenone were selected as the reaction raw materials;

[0010] (2) Mix diphenylphosphine oxide and 4-aminoacetophenone and heat to the reaction temperature; then add a catalyst and carry out the reaction at a constant temperature. After the reaction is completed, a phosphorus-containing flame retardant is obtained.

[0011] Preferably, the molar ratio of diphenylphosphine oxide to 4-aminoacetophenone is (1-2.5):(1-2).

[0012] Preferably, the molar ratio of the diphenylphosphine oxide to the catalyst is (1-2.5):(0.03-0.2).

[0013] Preferably, the catalyst is p-toluenesulfonic acid.

[0014] Preferably, the molar ratio of diphenylphosphine oxide, 4-aminoacetophenone, and p-toluenesulfonic acid is 2.1:1:0.05.

[0015] Preferably, the reaction temperature is 100℃-160℃ and the reaction time is 10-24h. More preferably, the reaction temperature is 125℃ and the reaction time is 12h.

[0016] Preferably, after the reaction is completed, a separation and purification step is also included, in which ethyl acetate is added to the crude product generated by the reaction, the amount of ethyl acetate added is 5-10 times the weight of the crude product, and then the product is placed at low temperature for 1-6 hours to allow the product to fully crystallize and precipitate, thereby obtaining a phosphorus-containing flame retardant.

[0017] After recrystallization, the product can be further washed with methanol to remove impurities and purify the product.

[0018] The application of phosphorus-containing flame retardants as described above in the preparation of flame-retardant materials.

[0019] A flame-retardant epoxy resin comprising, as described above, a phosphorus-containing flame retardant, 4,4'-diaminodiphenyl sulfone, and an epoxy resin, wherein the phosphorus-containing flame retardant accounts for 0.1%-1.5% of the mass of the epoxy resin.

[0020] The beneficial technical effects of this invention are:

[0021] The phosphorus-containing flame retardant designed and synthesized in this invention (named DPO2-NH2) contains primary amine groups and phosphorus-containing flame retardant groups. This phosphorus-containing flame retardant achieves curing and cross-linking through the reaction of protons provided by the primary amine groups with epoxy groups, and achieves flame retardancy through the char layer and free radicals generated by the thermal decomposition of the phosphorus-containing flame retardant groups. No additional co-initiator is required in this process, and the primary amine remains within the polymer molecular chain after curing, eliminating migration issues. Furthermore, using the phosphorus-containing flame retardant disclosed in this invention can yield epoxy resin flame-retardant materials with advantages such as low odor, low toxicity, good stability, and excellent hardness. Attached Figure Description

[0022] Figure 1 MS image of the phosphorus-containing flame retardant prepared in Example 1 of this invention;

[0023] Figure 2 The phosphorus-containing flame retardant prepared in Example 1 of this invention 1 H NMR spectrum;

[0024] Figure 3The phosphorus-containing flame retardant prepared in Example 1 of this invention 13 C NMR spectrum;

[0025] Figure 4 The phosphorus-containing flame retardant prepared in Example 1 of this invention 31 P NMR spectrum. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0027] Example 1

[0028] DPO (0.2 mol, 40.4 g), 4-aminoacetophenone (0.1 mol, 13.5 g) and p-toluenesulfonic acid (0.005 mol, 0.86 g) were weighed separately and used as reaction raw materials.

[0029] First, place DPO and 4-aminoacetophenone into a 1000 mL three-necked flask. The flask is equipped with a mechanical stirrer, a reflux condenser, and a thermometer to control and monitor the reaction process.

[0030] Raise the temperature to 150°C, then start stirring and mixing, and maintain this reaction condition for 12 hours.

[0031] After the reaction is complete, 500 mL of ethyl acetate is added to the crude reaction product, which helps to dissolve the product in the mixture and obtain the reaction solution.

[0032] Cool the reaction solution to room temperature. Recrystallize at room temperature to allow the resulting substance to recrystallize into a solid.

[0033] The recrystallized mixture was filtered to separate the product. It was then washed with methanol to remove impurities and purify the product. Finally, 20.78 g of DPO2-NH2 was collected as a light yellow powder, with a yield of 39.9%.

[0034] Example 2

[0035] DPO (0.21 mol, 42.42 g), 4-aminoacetophenone (0.1 mol, 13.5 g) and p-toluenesulfonic acid (0.05 mol, 8.6 g) were weighed separately and used as reaction raw materials.

[0036] First, place DPO and 4-aminoacetophenone into a 1000 mL three-necked flask.

[0037] Raise the temperature to 120°C, then start stirring and mixing, and maintain this reaction condition for 12 hours.

[0038] After the reaction was completed, 500 mL of ethyl acetate was added to the crude reaction product to obtain the reaction solution.

[0039] Cool the reaction solution to room temperature. Recrystallize at room temperature to allow the resulting substance to recrystallize into a solid.

[0040] The recrystallized mixture was filtered to separate the product. It was then washed with methanol to remove impurities and purify the product. Finally, 33.08 g of DPO2-NH2 was collected as a light yellow powder, with a yield of 63.5%.

[0041] Example 3

[0042] DPO (0.1 mol, 20.2 g), 4-aminoacetophenone (0.1 mol, 13.5 g) and p-toluenesulfonic acid (0.05 mol, 8.6 g) were weighed separately and used as reaction raw materials.

[0043] First, place DPO and 4-aminoacetophenone into a 1000 mL three-necked flask.

[0044] Raise the temperature to 160°C, then start stirring and mixing, and maintain this reaction condition for 20 hours.

[0045] After the reaction was completed, 500 mL of ethyl acetate was added to the crude reaction product to obtain the reaction solution.

[0046] Cool the reaction solution to room temperature. Recrystallize at room temperature to allow the resulting substance to recrystallize into a solid.

[0047] The recrystallized mixture was filtered to separate the product. It was then washed with methanol to remove impurities and purify the product. Finally, 22.35 g of DPO2-NH2 was collected as a pale yellow powder, with a yield of 42.9%.

[0048] Example 4

[0049] DPO (0.15 mol, 30.3 g), 4-aminoacetophenone (0.1 mol, 13.5 g) and p-toluenesulfonic acid (0.1 mol, 17.2 g) were weighed separately and used as reaction raw materials.

[0050] First, place DPO and 4-aminoacetophenone into a 1000 mL three-necked flask.

[0051] Raise the temperature to 100°C, then start stirring and mixing, and maintain this reaction condition for 18 hours.

[0052] After the reaction was completed, 700 mL of ethyl acetate was added to the crude reaction product to obtain the reaction solution.

[0053] Cool the reaction solution to room temperature. Recrystallize at room temperature to allow the resulting substance to recrystallize into a solid.

[0054] The recrystallized mixture was filtered to separate the product. It was then washed with methanol to remove impurities and purify the product. Finally, 21.15 g of DPO2-NH2 was collected as a light yellow powder, with a yield of 40.6%.

[0055] Figure 1 The image shows the MS spectrum of the phosphorus-containing flame retardant prepared in Example 1. The relative molecular mass of the phosphorus-containing flame retardant was calculated to be 521.2. The peak at 522.2 in the image is a quasi-molecular ion peak, which is the sample molecular mass plus the mass of hydrogen (M+H).

[0056] Figure 2 The phosphorus-containing flame retardant prepared in Example 1 1 The 1H NMR spectrum shows the chemical shifts of H atoms on the four monosubstituted benzene rings at δ = 8.32–8.76 (m, 20H) ppm, the peak at δ = 7.38 (d, 2H) ppm, the peak at δ = 7.96 (d, 2H) ppm, the peak at δ = 7.96 (d, 2H) ppm, the peak at δ = 4.44 (s, 3H) ppm, and the peak at δ = 4.44 (s, 3 ...), and the peak at δ = 4.44 (s, 3H), the peak at δ = 4.44 (s, 3H), and

[0057] Figure 3 The phosphorus-containing flame retardant prepared in Example 1 of this invention 13 C NMR spectrum; Figure 4 The phosphorus-containing flame retardant prepared in Example 1 of this invention 31 P NMR spectrum.

[0058] Combining MS and 1 ¹H NMR spectra and other data proved that the synthesized substance is a phosphorus-containing flame retardant.

[0059] Furthermore, the synthesized phosphorus-containing flame retardant prepared according to this invention exhibits good flowability. The phosphorus-containing flame retardant can be further used to prepare flame-retardant epoxy resin.

[0060] Example 5

[0061] Preparation of epoxy resin samples:

[0062] The formulations of the epoxy resin cured samples are shown in Table 1. First, DGEBA and DPO2-NH2 were heated to 150°C and stirred until DPO2-NH2 was completely dissolved in DGEBA. Then, DDS was added and mixed. After the DDS dissolved in DGEBA, the mixture was poured into a preheated mold and cured at 125°C for 2 hours, followed by curing at 180°C for 2 hours. The prepared samples were labeled according to their flame retardant properties and the mass content of phosphorus (P) in the epoxy thermosetting resin. For example, EP / DPO2-NH2-P-0.9 indicates that the flame retardant is DPO2-NH2 and the mass content of phosphorus in the thermosetting material is 0.9 wt%.

[0063] Comparative Example 1

[0064] Preparation of epoxy resin samples

[0065] The formulations of the UV-cured samples are shown in Table 1. DGEBA and DDS were heated to 150°C and mixed, stirring until transparent. After the DDS dissolved in the DGEBA, the mixture was poured into a preheated mold and cured at 125°C for 2 hours, followed by curing at 180°C for 2 hours.

[0066] Flame retardancy rating test

[0067] According to UL-94, the flame retardancy rating results are shown in Table 2.

[0068] Table 1 shows the formulations of epoxy resin thermosetting materials.

[0069] Table 1

[0070]

[0071] Table 2 shows the UL-94 test results.

[0072] Table 2

[0073]

[0074] As can be seen from Tables 1 and 2, the phosphorus-containing flame retardant prepared by the present invention can significantly improve the flame retardant properties of epoxy resin.

[0075] For any parts not mentioned above, existing technologies can be adopted or referenced.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A phosphorus-containing flame retardant for epoxy resins, characterized in that: Compounds having the following structures: 。 2. The preparation method of the phosphorus-containing flame retardant as described in claim 1, characterized in that... Includes the following steps: (1) Diphenylphosphine oxide and 4-aminoacetophenone were selected as the reaction raw materials; (2) Mix diphenylphosphine oxide and 4-aminoacetophenone, heat to the reaction temperature; then add a catalyst and carry out the reaction at a constant temperature. After the reaction is completed, a phosphorus-containing flame retardant is obtained. The catalyst is p-toluenesulfonic acid; the reaction temperature is 100℃-160℃. The molar ratio of diphenylphosphine oxide to 4-aminoacetophenone is (1-2.5):(1-2). The molar ratio of the diphenyloxyphosphine to the catalyst is (1-2.5):(0.03-0.2). The reaction time is 10-24 hours.

3. The method for preparing the phosphorus-containing flame retardant according to claim 2, characterized in that: The molar ratio of diphenylphosphine oxide, 4-aminoacetophenone, and p-toluenesulfonic acid is 2.1:1:0.

05.

4. The method for preparing the phosphorus-containing flame retardant according to claim 2, characterized in that: After the reaction is completed, a separation and purification step is also included. Ethyl acetate is added to the crude product generated by the reaction. The amount of ethyl acetate added is 5-10 times the weight of the crude product. Then, it is placed at low temperature for 1-6 hours to allow the product to fully crystallize and precipitate, thus obtaining a phosphorus-containing flame retardant.

5. The application of the phosphorus-containing flame retardant as described in claim 1 in the preparation of flame-retardant materials.

6. A flame-retardant epoxy resin, characterized in that: The mixture includes the phosphorus-containing flame retardant as described in claim 1, 4,4'-diaminodiphenyl sulfone, and epoxy resin, wherein the phosphorus-containing flame retardant accounts for 0.1%-1.5% of the mass of the epoxy resin.

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