P / N / S-containing DOPO derivative flame retardant for V0-grade insulating material as well as preparation method and application of flame retardant

Abstract

The invention discloses a P / N / S-containing DOPO (9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) derivative flame retardant for a V0-grade insulating material as well as a preparation method and application of the flame retardant, and belongs to the technical field of The method comprises the following steps: in a solvent, carrying out a reaction on furfural and 2-amino-5-ethylbenzothiazole at 60-80 DEG C; after the reaction is completed, obtaining an intermediate product, and then adding DOPO; reacting at 80-100 DEG C to obtain a flame retardant; the molar ratio of the furfural to the 2-amino-5-ethylbenzothiazole is 1: (1-2), and the molar ratio of the DOPO to the intermediate product is 1: (1-2). The flame retardant is used in epoxy resin taking 4, 4 '-diaminodiphenylmethane as a curing agent. The flame retardant contains phosphorus, nitrogen and sulfur, can realize phosphorus-nitrogen-sulfur synergistic flame retardance, and has a good flame retardant effect after being applied to an epoxy resin material. The release of heat and smoke in the combustion process of the epoxy resin can be effectively inhibited, the formation of a carbon layer is promoted, and the flame retardant property is remarkable.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardants, and particularly relates to a DOPO derivative flame retardant containing P / N / S for V0 grade insulating materials, a preparation method and application thereof, and is specially used for flame retardancy of epoxy resin. Background Art

[0002] Epoxy resin (EP) has the advantages of excellent electrical insulation, high mechanical properties, good adhesion and chemical corrosion resistance, and is therefore widely used in various industries. However, the flammable nature of EP limits its application in fields with a high fire safety factor. DOPO derivatives have the advantages of low toxicity and low smoke, and are currently widely used in polymer materials including EP, and exhibit excellent flame retardant efficiency. DOPO molecules contain active PH bonds that can react with a variety of functional groups (C=N, C=C, C=O, etc.), so other flame retardant elements (nitrogen, sulfur, boron, etc.) can be introduced through molecular design to synthesize a series of DOPO derivatives to improve their flame retardant efficiency. Prior art 1 synthesized a P / N derivative flame retardant (DOPO-BNM) using DOPO, 2-aminobenzimidazole and 3-nitrobenzaldehyde as raw materials. When the content of DOPO-BNM in epoxy resin is 8wt%, the EP / 8%DOPO-BNM sample passes the V-0 classification in the UL-94 test, and its LOI increases to 32.5%. It is worth noting that the PHRR, THR, PSPR and TSP of the EP / 8%DOPO-BNM sample are 13.0%, 28.8%, 33.3% and 47.9% lower than those of the EP sample, respectively, indicating that DOPO-BNM has an inhibitory effect on the heat and smoke release of EP thermosetting materials. The prior art synthesizes a triazole-containing DOPO derivative (DOPO-SGA) using syringaldehyde, 3,5-diamino-1,2,4-triazole (GA) and DOPO, and introduces it into EP. Only 3 wt% DOPO-SGA is needed to increase the LOI of EP to 33.2%, the UL-94 grade is raised to V-0, and the smoke and heat release of EP is reduced. At the same time, the introduction of DOPO-SGA can also improve the tensile strength and impact strength of EP. Prior art three uses 3,5-diamino-1,2,4-triazole, vanillin and DOPO as raw materials, and synthesizes a DOPO derivative (VDG) containing triazole through nucleophilic addition reaction. And epoxy resin cured product is prepared with DDM as curing agent and VDG as co-curing agent. VDG exhibits super flame retardant properties. 2.0wt% VDG can increase the LOI of EP to 37.0% and pass the UL-94 V-0 rating. At the same time, it also effectively inhibits the release of heat during EP combustion, and PHRR and THR are reduced by 47.5% and 34% respectively. The flame retardant properties of EP are significantly improved. Prior art four uses p-aminobenzonitrile, p-hydroxybenzaldehyde and DOPO as raw materials, and synthesizes a new reactive flame retardant (PABO) through a one-pot reaction, and applies it to EP. Thermogravimetric analysis showed that PABO had a higher degradation temperature, a lower thermal decomposition rate, and Char800 (carbon residue at 800 °C) increased from 1.5% to 26.5wt% compared with DOPO.EP / PABO-5 with only 5wt% PABO content has a LOI value of 32.7% and passes the UL-94 V-0 rating. In addition, the PHRR, THR and TSP of EP / PABO-5 decreased by 19.7%, 19.0% and 19.4% respectively compared with EP. The calculated flame retardant index (FIGRA) shows that the fire safety of EP / PABO-5 is better than that of EP / DOPO-5. Based on the chemical properties of DOPO that can react with a variety of functional groups, the rational introduction of other flame retardant elements into DOPO derivatives is bound to develop more new epoxy resin flame retardants with excellent performance. Summary of the invention

[0003] This patent successfully synthesized a new flame retardant containing P / N / S through the addition reaction of DOPO with an intermediate containing a Schiff base generated by the reaction of 2-amino-5-ethylbenzothiazole and furfural; the flame retardant is effective in epoxy resins with 4,4'-diaminodiphenylmethane as a curing agent. The technical solution is as follows: On the one hand, an embodiment of the present invention provides a DOPO derivative flame retardant containing PNS for B1-class flame-retardant cable materials, and the structural formula is as follows: .

[0004] The flame retardant is a gray powder, contains nitrogen, sulfur and phosphorus elements, has good compatibility with epoxy resin (characterized by not changing the transparency of epoxy resin), and the applicant named it DBF.

[0005] On the other hand, the present invention also provides a method for preparing the flame retardant, comprising: reacting furfural with 2-amino-5-ethylbenzothiazole at 60-80°C in a solvent; after the reaction is completed, an intermediate product is obtained, and then DOPO is added; and reacting at 80-100°C to obtain a flame retardant. The molar ratio of furfural to 2-amino-5-ethylbenzothiazole is 1:1-2, and the molar ratio of DOPO to the intermediate product is 1:1-2.

[0006] Wherein, the solvent is selected from anhydrous ethanol and the like.

[0007] The preparation method provided in this embodiment includes: (1) Furfural and 2-amino-5-ethylbenzothiazole are added to anhydrous ethanol and reacted at 60-80° C. for 12-24 hours to obtain an intermediate product.

[0008] (2) Dissolve DOPO in anhydrous ethanol and add it to the reaction solution of step (1), react at 80-100° C. for 12-24 hours. After the reaction is completed, cool, separate the solid and liquid, wash with ethanol, and dry to obtain a flame retardant.

[0009] Among them, the number of ethanol washings is 3-6 times.

[0010] Among them, the drying temperature is 55-65°C and the drying time is 8-15h.

[0011] Specifically, the preparation method provided in this embodiment includes: (1) Add furfural and 2-amino-5-ethylbenzothiazole to anhydrous ethanol and react at 60-80°C for 12-24 hours to obtain an intermediate product. The molar ratio of furfural to 2-amino-5-ethylbenzothiazole is 1:1-2. The reaction equation is as follows: .

[0012] (2) Dissolve DOPO in anhydrous ethanol and add it to the reaction solution of step (1), react at 80-100°C for 12-24h. After the reaction is completed, cool to room temperature, filter, and wash the residue with ethanol 3-6 times; finally, dry at 55-65°C for 8-15h to obtain the product. The reaction equation is as follows: .

[0013] In another aspect, the present invention also provides the use of the aforementioned flame retardant, which is used in an epoxy resin with 4,4'-diaminodiphenylmethane as a curing agent. The amount of the flame retardant added is 1-6% of the weight of the epoxy resin; specifically, it can be 4%. The epoxy resin is selected from E51 epoxy resin, E54 epoxy resin, etc., specifically, it can be E51 epoxy resin; the amount of the curing agent is 2-30% of the weight of the epoxy resin.

[0014] Specifically, the process of preparing the modified epoxy resin material with a curing agent, a flame retardant and an epoxy resin is as follows: slowly add the flame retardant to the epoxy resin according to the proportion, stir at 125-135°C until transparent, and obtain a uniform mixed liquid; then stir the obtained epoxy resin and 4,4'-diaminodiphenylmethane at 75-85°C until 4,4'-diaminodiphenylmethane is completely dissolved; finally, pour the epoxy resin mixture into a mold for temperature curing, and the curing temperature is 110-160°C. The curing process is specifically: curing at 120°C for 120 minutes and curing at 150°C for 240 minutes.

[0015] The invention has the following advantages: the novel flame retardant DBF obtained by the invention contains a DOPO structural unit with low toxicity, low smoke and obvious flame retardant effect in its molecular structure, and at the same time introduces flame retardant elements such as nitrogen and sulfur, thereby further improving the flame retardant effect of the DOPO structural unit. After being applied to epoxy resin materials, phosphorus-nitrogen-sulfur synergistic flame retardancy can be achieved, and the release of heat and smoke during the combustion of epoxy resin can be effectively suppressed, while the formation of a carbon layer can be promoted, and the flame retardant effect is remarkable. In addition, the flame retardant has good compatibility with epoxy resin and will not have a negative impact on the mechanical properties of the epoxy resin substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the infrared spectrum of the flame retardant prepared in Example 1; Figure 2 This is the H-NMR graph of the flame retardant prepared in Example 1. DETAILED DESCRIPTION

[0017] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0018] Example 1 Embodiment 1 provides a method for preparing a flame retardant, the method comprising the following steps: (1) Furfural (0.02 mol, 1.92 g), 2-amino-5-ethylbenzothiazole (0.02 mol, 3.00 g) and 50 mL of anhydrous ethanol were added to a three-necked flask equipped with a magnetic stirrer and a condenser reflux. The mixture was heated to 65°C and maintained at this temperature for 14 h with constant stirring.

[0019] (2) Add 30 mL of anhydrous ethanol solution containing DOPO (0.02 mol, 4.32 g), raise the system temperature to 84 °C, and continue stirring for 15 h. After the reaction is completed, cool naturally to room temperature, and collect the crude product by suction filtration. The crude product is washed three times with ethanol and vacuum dried at 60 °C for 12 h to obtain a gray powder DBF.

[0020] The infrared spectrum of the prepared DBF is shown in Figure 1 As shown: 2436cm in the infrared spectrum of DBF -1 There is no absorption peak of PH bond at 3226cm -1 The characteristic absorption peak of NH appeared, indicating that the reaction of DOPO with the Schiff base-containing intermediate was complete. -1 and 1478cm -1 There is an absorption signal at 1240cm -1 and 1117cm -1There is also an absorption signal at 932cm -1 and 750cm -1 The absorption peak at is the characteristic absorption peak of PO-Ph. The H-NMR spectrum of the prepared DBF is shown in Figure 2 Shown: H-NMR: 7.94ppm (4H), 7.67-7.28ppm (6H), 7.06ppm (3H), 6.54ppm (1H), 6.40ppm (1H), 6.28ppm (1H), 5.85ppm (1H), 1.28ppm (2H), 0.88ppm (3H).

[0021] Example 2 Embodiment 2 provides a method for preparing a flame retardant, the method comprising the following steps: (1) Furfural (0.02 mol, 1.92 g), 2-amino-5-ethylbenzothiazole (0.03 mol, 4.50 g) and 60 mL of anhydrous ethanol were added to a three-necked flask equipped with a magnetic stirrer and a condenser reflux. The mixture was heated to 70°C and maintained at this temperature for 13 h with constant stirring.

[0022] (2) Add 30 mL of anhydrous ethanol solution containing DOPO (0.024 mol, 5.18 g), raise the system temperature to 85 °C, and continue stirring for 16 h. After the reaction is completed, cool naturally to room temperature, and collect the crude product by suction filtration. The crude product is washed four times with ethanol and vacuum dried at 60 °C for 12 h to obtain a gray powder DBF.

[0023] Example 3 Example 3 provides a method for preparing a modified epoxy resin material, using the flame retardant synthesized in Example 1 as a flame retardant modifier and 4,4'-diaminodiphenylmethane as a curing agent to prepare a modified E51 epoxy resin material. The process is: The flame retardant (1.0 g) prepared in Example 1 was weighed and slowly added to the E51 epoxy resin (39.2 g), and stirred at 130°C until transparent to obtain a uniform mixed solution. The obtained epoxy resin and 4,4'-diaminodiphenylmethane (9.8 g) were then stirred at 80°C for 5 min until the curing agent was completely dissolved. Finally, the epoxy resin mixture was poured into a mold for temperature curing, and the curing procedure was 120°C for 120 min and 150°C for 240 min to prepare a modified epoxy resin material with a flame retardant content of 1.96 wt%.

[0024] In this example, the flame retardant was completely dissolved in the epoxy resin without changing the transparency of the epoxy resin.

[0025] Example 4 Example 4 provides a method for preparing a modified epoxy resin material, using the flame retardant synthesized in Example 1 as a flame retardant modifier and 4,4'-diaminodiphenylmethane as a curing agent to prepare a modified E54 epoxy resin material. The process is: The flame retardant (1.5 g) prepared in Example 1 was weighed and slowly added to the E54 epoxy resin (38.8 g), and stirred at 130°C until transparent to obtain a uniform mixed solution. The obtained epoxy resin and 4,4'-diaminodiphenylmethane (9.7 g) were then stirred at 80°C for 5 min until the curing agent was completely dissolved. Finally, the epoxy resin mixture was poured into a mold for temperature curing, and the curing procedure was 120°C for 120 min and 150°C for 240 min to prepare a modified epoxy resin material with a flame retardant content of 3 wt%.

[0026] In this example, the flame retardant was completely dissolved in the epoxy resin without changing the transparency of the epoxy resin.

[0027] Example 5 Example 5 provides a method for preparing a modified epoxy resin material, using the flame retardant synthesized in Example 1 as a flame retardant modifier and 4,4'-diaminodiphenylmethane as a curing agent to prepare a modified E51 epoxy resin material. The process is: The flame retardant (2.0 g) prepared in Example 1 was weighed and slowly added to the E51 epoxy resin (38.4 g), and stirred at 130°C until transparent to obtain a uniform mixed solution. The obtained epoxy resin and 4,4'-diaminodiphenylmethane (9.6 g) were then stirred at 80°C for 5 min until the curing agent was completely dissolved. Finally, the epoxy resin mixture was poured into a mold for temperature curing, and the curing procedure was 120°C for 120 min and 150°C for 240 min to prepare a modified epoxy resin material with a flame retardant content of 4 wt%.

[0028] Comparative Example 1 Comparative Example 1 provides a method for preparing a modified epoxy resin material, using 4,4'-diaminodiphenylmethane as a curing agent and no flame retardant to prepare an E51 epoxy resin material. The process is: Weigh 38.4g of E51 epoxy resin and stir at 130°C until transparent to obtain a uniform liquid of epoxy resin. Then stir the obtained epoxy resin with 9.6g of 4,4'-diaminodiphenylmethane at 80°C for 5min until the curing agent is completely dissolved to obtain an epoxy resin mixed liquid. Finally, pour the epoxy resin mixed liquid into the mold for temperature curing. The curing procedure is 120°C for 120min and 150°C for 240min, to obtain an epoxy resin material without flame retardant.

[0029] Comparative Example 2 Comparative Example 2 provides a method for preparing a modified epoxy resin material, using DOPO as a flame retardant modifier and 4,4'-diaminodiphenylmethane to prepare a modified E51 epoxy resin material. The process is: Weigh DOPO (2.0 g) and slowly add it to E51 epoxy resin (38.4 g), stir at 130°C until transparent, and obtain a uniform mixed solution. Then stir the obtained epoxy resin and 4,4'-diaminodiphenylmethane (9.6 g) at 80°C for 5 min until the curing agent is completely dissolved. Finally, pour the epoxy resin mixture into the mold for temperature curing. The curing procedure is 120°C for 120 min and 150°C for 240 min to prepare a modified epoxy resin material with a DOPO content of 4 wt%.

[0030] The epoxy resin materials obtained in Comparative Example 1, Comparative Example 2 and Example 5 were tested for flame retardancy, mechanical properties and thermal stability. The UL-94 vertical combustion test was conducted using the GB / T2408 standard; the oxygen index was conducted using the GB / T8924 standard; and the tensile and bending tests were conducted using the GB / T2006 standard. The test results are shown in Table 1: Table 1

[0031] As can be seen from Table 1, for pure epoxy resin, the oxygen index is 26, there is no flame retardant grade, and the tensile strength and flexural strength are 87.7MPa and 112Mpa respectively. When the content of the flame retardant of this patent is 4%, its flexural strength is improved, the tensile strength remains basically unchanged, and the UL-94 vertical combustion can reach V-0 level. The effect of DBF on the mechanical properties of epoxy resin was studied by tensile, bending and notched impact tests. The results show that DBF has no adverse effect on the mechanical properties of EP, and DBF can give EP good flame retardant properties without reducing the mechanical properties. In addition, the sample of Example 5 releases basically no smoke when burning.

[0032] Comparative Example 3 Comparative Example 3 provides a method for preparing a modified epoxy resin material, using the flame retardant synthesized in Example 1 as a flame retardant modifier and dicyandiamide as a curing agent to prepare a modified E51 epoxy resin material. The process is: The flame retardant (2.0 g) prepared in Example 1 was weighed and slowly added to E51 epoxy resin (38.4 g), and stirred at 130° C. until transparent to obtain a uniform mixed solution. The obtained epoxy resin and dicyandiamide (9.6 g) were then stirred at 80° C. for 5 min until the curing agent was completely dissolved. Finally, the epoxy resin mixture was poured into a mold for temperature curing, and the curing procedure was 120° C. for 120 min and 150° C. for 240 min to prepare a modified epoxy resin material with a flame retardant content of 4 wt%.

[0033] Comparative Example 4 Comparative Example 4 provides a method for preparing a modified epoxy resin material, using the flame retardant synthesized in Example 1 as a flame retardant modifier and 4,4'-diaminodiphenyl sulfone as a curing agent to prepare a modified E51 epoxy resin material. The process is: The flame retardant (2.0 g) prepared in Example 1 was weighed and slowly added to the E51 epoxy resin (38.4 g), and stirred at 130°C until transparent to obtain a uniform mixed solution. The obtained epoxy resin and 4,4'-diaminodiphenyl sulfone (9.6 g) were then stirred at 80°C for 5 min until the curing agent was completely dissolved. Finally, the epoxy resin mixture was poured into a mold for temperature curing, and the curing procedure was 120°C for 120 min and 150°C for 240 min to prepare a modified epoxy resin material with a flame retardant content of 4 wt%.

[0034] The epoxy resin materials obtained in Comparative Example 3, Comparative Example 4 and Example 5 were tested for flame retardancy, mechanical properties and thermal stability. The test results are shown in Table 2: Table 2

[0035] As can be seen from Table 2, the flame retardant of this patent is generally effective in epoxy resins with other curing agent systems, and is not as good as in epoxy resins with 4,4'-diaminodiphenylmethane.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A DOPO derivative flame retardant containing P / N / S for V0 grade insulating materials, characterized in that: The structural formula is as follows: 。 2. The method for preparing a flame retardant according to claim 1, characterized in that: The method comprises: in a solvent, reacting furfural and 2-amino-5-ethylbenzothiazole at 60-80°C; after the reaction is completed, an intermediate product is obtained, and then DOPO is added; reacting at 80-100°C to obtain a flame retardant; the molar ratio of the furfural to the 2-amino-5-ethylbenzothiazole is 1:1-2, and the molar ratio of the DOPO to the intermediate product is 1:1-2.

3. The method according to claim 2, characterized in that The solvent is selected from anhydrous ethanol.

4. The method according to claim 2, characterized in that The method comprises: (1) adding furfural and 2-amino-5-ethylbenzothiazole to anhydrous ethanol, and reacting at 60-80° C. for 12-24 hours to obtain an intermediate product; (2) Dissolve DOPO in anhydrous ethanol and add it to the reaction solution of step (1), react at 80-100° C. for 12-24 hours. After the reaction is completed, cool, separate the solid and liquid, wash with ethanol, and dry to obtain a flame retardant.

5. The method according to claim 4, characterized in that The number of ethanol washes is 3-6 times.

6. The method according to claim 4, characterized in that The drying temperature is 55-65℃ and the drying time is 8-15h.

7. Use of the flame retardant according to claim 1 in epoxy resin with 4,4'-diaminodiphenylmethane as a curing agent.

8. The use according to claim 7, characterized in that: The added amount of the flame retardant is 1-6% of the weight of the epoxy resin.

9. The use according to claim 8, characterized in that: The epoxy resin is selected from E51 epoxy resin and E54 epoxy resin, and the amount of the curing agent is 2-30% by weight of the epoxy resin.

10. The use according to claim 9, characterized in that: The process of preparing the modified epoxy resin material with a curing agent, a flame retardant and an epoxy resin is as follows: slowly adding the flame retardant into the epoxy resin according to the ratio, stirring at 125-135°C until it becomes transparent; then stirring the obtained epoxy resin with 4,4'-diaminodiphenylmethane at 75-85°C until 4,4'-diaminodiphenylmethane is completely dissolved; finally, pouring the epoxy resin mixture into a mold for heating and curing, and the curing temperature is 110-160°C.

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