A phosphorus-containing flame-retardant epoxy resin and a preparation method thereof

Abstract

The application relates to the technical field of high polymer materials, and discloses a phosphorus-containing flame-retardant epoxy resin and a preparation method thereof, which comprises the following components by weight: 50-65 parts of bisphenol A type epoxy resin, 4-6 parts of phosphorus-containing modified benzimidazole, 2-3 parts of epoxy-based sulfanilamide thiazole and 2-4 parts of m-phenylenediamine curing agent. The bisphenol A type epoxy resin is added into a stirrer, heated, and then the phosphorus-containing modified benzimidazole and the epoxy-based sulfanilamide thiazole are continuously added into the stirrer; after cooling, the m-phenylenediamine curing agent is continuously added into the stirrer, and then curing is carried out, so that the phosphorus-containing flame-retardant epoxy resin is obtained. The phosphorus-containing flame-retardant epoxy resin has good flame-retardant effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to a phosphorus-containing flame-retardant epoxy resin and a preparation method thereof. BACKGROUND

[0002] Epoxy resin is an important thermosetting polymer material, which has excellent mechanical properties, adhesion, chemical corrosion resistance and electrical insulation, and is widely used in electronic packaging, composite materials, coatings, adhesives and other fields. However, the limiting oxygen index (LOI) of traditional epoxy resin is usually only 19%~21%, which is very flammable, greatly limiting its application. For example, a kind of epoxy resin and its preparation method are disclosed in Chinese patent application No. CN110790897A. The epoxy resin has good corrosion resistance and mechanical strength, but its flame-retardant effect has not been improved. SUMMARY

[0003] In view of the deficiencies of the prior art, the present application provides a phosphorus-containing flame-retardant epoxy resin and a preparation method thereof, which has good flame-retardant effect.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a phosphorus-containing flame-retardant epoxy resin, comprising the following weight components: 50-65 parts by weight of bisphenol A type epoxy resin, 4-6 parts by weight of phosphorus-containing modified benzimidazole, 2-3 parts by weight of epoxy-based sulfanilamide thiazole, and 2-4 parts by weight of m-phenylenediamine curing agent.

[0005] Further, the preparation method of the phosphorus-containing modified benzimidazole is as follows:

[0006] S1. Mix 1.2-1.3g of o-phenylenediamine and 90-100mL of dichloromethane, and add 1.15-1.26g of phosphorus oxychloride at a temperature of 20-22℃. After the addition is completed, the temperature is raised to 50-55℃ for reflux reaction. After the reaction is completed, the temperature is cooled to room temperature, then washed with acetonitrile, and vacuum dried to constant weight to obtain an intermediate;

[0007]

[0008] S2. At 20-25℃, add 6.01-6.03g of 2-mercaptobenzimidazole, 150-160mL of acetonitrile and 6-8mL of catalyst into a stirrer, stir and mix, then continue to add 9.5-10.6g of the intermediate thereto, react at room temperature for 3-4h, then heat to 80-85℃ for 8-10h, then cool to room temperature, wash with saturated sodium bicarbonate solution and deionized water respectively, and dry to obtain the phosphorus-containing modified benzimidazole.

[0009] Further, the reflux reaction time in S1 is 4-6h.

[0010] Further, the catalyst in S2 is triethylamine.

[0011] Further, the preparation method of the epoxy sulfathiazole is:

[0012] Step one: first, 7.62-7.66g of sulfathiazole is dissolved in 140-150mL of anhydrous ethanol, then 2.81-2.88g of 5-hydroxymethyl furfural is added, stirring at 70-80℃ for 6-8h, then 6.44-6.49g of DOPO is added, and stirring is continued at 80-85℃ for 20-24h, after reaction, cooling, washing with anhydrous ethanol, and drying to obtain hydroxyl modified sulfathiazole;

[0013] Step two: 4.52-5.33g of hydroxyl modified sulfathiazole and 0.11-0.21g of catalyst are added to 30-40mL of epichlorohydrin, and the reaction is carried out at 80-82℃ for 4-5h, then the temperature is lowered to 55-60℃, 1.21-1.24g of sodium hydroxide aqueous solution is added, and the ring closing reaction is carried out at 60-65℃ for 3-4h, after the reaction is completed, cooling, and filtration to obtain epoxy sulfathiazole.

[0014] Further, the catalyst in step two is tetrabutylammonium bromide.

[0015] Further, the mass concentration of the sodium hydroxide aqueous solution in step two is 20%.

[0016] Further, the preparation method of the phosphorus-containing flame-retardant epoxy resin is: the bisphenol A type epoxy resin is added to a stirrer, heated to 150-160℃, then the phosphorus-containing modified benzimidazole and the epoxy sulfathiazole are added, cooled to 90-95℃, then the m-phenylenediamine curing agent is added, and cured at 100℃ for 2h to obtain the phosphorus-containing flame-retardant epoxy resin.

[0017] The present application adds the bisphenol A type epoxy resin to a stirrer, heats, then adds the phosphorus-containing modified benzimidazole and the epoxy sulfathiazole, cools, then adds the m-phenylenediamine curing agent, and cures to obtain the phosphorus-containing flame-retardant epoxy resin.

[0018] In the above reaction process, the amine group in o-phenylenediamine reacts with the chlorine in phosphorus oxychloride to obtain an intermediate, then the intermediate reacts with the mercapto group in 2-mercaptobenzimidazole to obtain the phosphorus-containing modified benzimidazole. The amino group in sulfathiazole reacts with the aldehyde group in 5-hydroxymethyl furfural to obtain a Schiff base, then the Schiff base reacts with the phosphorus-hydrogen bond in DOPO to introduce a hydroxyl group, thereby obtaining the hydroxyl modified sulfathiazole, and then the hydroxyl modified sulfathiazole reacts with the chlorine in epichlorohydrin to obtain the epoxy sulfathiazole.

[0019] The phosphorus element, the sulfur element and the nitrogen element contained in the phosphorus-modified benzimidazole and the epoxy-based sulfonamide thiazole have good flame-retardant effect. The phosphorus element can generate polyphosphoric acid and metaphosphoric acid with strong dehydration during combustion. Since the polyphosphoric acid and the metaphosphoric acid are not easy to volatilize, a dense protective layer is formed on the surface of the resin material, thereby achieving the effect of flame retardation. The sulfur element can promote the formation of a carbon layer on the surface of the material at high temperature, thereby insulating oxygen and slowing down the combustion speed. The nitrogen element can generate non-combustible gas when heated, which can not only dilute the concentration of flammable gas, but also take away part of the heat, thereby further limiting the combustion of the material. The Schiff base structure (-CH=N-) in the epoxy-based sulfonamide thiazole has excellent carbon formation performance, which can promote carbon formation during the combustion of the epoxy resin, thereby achieving good flame-retardant effect. During the curing process, the benzimidazole structure in the phosphorus-modified benzimidazole and the active secondary amine in the epoxy-based sulfonamide thiazole can catalyze the curing of the epoxy resin, and form a curing system with the curing agent. The epoxy group in the epoxy-based sulfonamide thiazole also participates in the curing reaction, thereby improving the compatibility between each other and making the flame-retardant elements more uniformly distributed in the resin. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is the nuclear magnetic resonance hydrogen spectrum of the phosphorus-modified benzimidazole.

[0021] Figure 2 is the nuclear magnetic resonance hydrogen spectrum of the epoxy-based sulfonamide thiazole. DETAILED DESCRIPTION

[0022] DOPO: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0023] Example 1

[0024] S1. 1.2 g of o-phenylenediamine and 90 mL of dichloromethane were mixed, 1.15 g of phosphorus oxychloride was added at a temperature of 20°C, after the dropwise addition was completed, the temperature was increased to 50°C and refluxed for 4 h, after the reaction was completed, it was cooled to room temperature, then washed with acetonitrile and dried under vacuum to constant weight to obtain an intermediate;

[0025] S2. 6.01 g of 2-mercaptobenzimidazole, 150 mL of acetonitrile and 6 mL of triethylamine were added to a stirrer at 20°C, the mixture was stirred, then 9.5 g of the intermediate was added thereto, and the reaction was carried out at room temperature for 3 h and then at 80°C for 8 h, after the reaction was completed, it was cooled to room temperature, washed with saturated sodium bicarbonate solution and deionized water respectively, and dried to obtain the phosphorus-modified benzimidazole;

[0026] S3. First, 7.62 g of sulfathiazole was dissolved in 140 mL of anhydrous ethanol, then 2.81 g of 5-hydroxymethylfurfural was added, stirred at 70°C for 6 h, then 6.44 g of DOPO was added and stirred at 80°C for 20 h, after reaction, cooled, washed with anhydrous ethanol, dried to obtain hydroxyl modified sulfathiazole;

[0027] S4. 4.52 g of hydroxyl modified sulfathiazole and 0.11 g of tetrabutylammonium bromide were added to 30 mL of epichlorohydrin, reacted at 80°C for 4 h, then cooled to 55°C, and 1.21 g of 20% mass concentration sodium hydroxide aqueous solution was continuously added, and the ring closing reaction was carried out at 60°C for 3 h, after the end of the reaction, cooled, suction filtered, washed to obtain epoxy sulfathiazole;

[0028] S5. 50 parts by weight of bisphenol A type epoxy resin was added to a stirrer, heated to 150°C, and 4 parts by weight of phosphorus modified benzimidazole, 2 parts by weight of epoxy sulfathiazole was continuously added, cooled to 90°C, and 2 parts by weight of m-phenylenediamine curing agent was continuously added, and cured at 100°C for 2 h to obtain a phosphorus-containing flame-retardant epoxy resin.

[0029] Example 2

[0030] S1. 1.3 g of o-phenylenediamine and 100 mL of dichloromethane were mixed, and 1.26 g of phosphorus oxychloride was added at a temperature of 22°C, after the end of dropwise addition, the temperature was increased to 55°C and refluxed for 6 h, after the reaction was completed, cooled to room temperature, then washed with acetonitrile, and vacuum dried to constant weight to obtain an intermediate;

[0031] S2. 6.03 g of 2-mercaptobenzimidazole, 160 mL of acetonitrile and 8 mL of triethylamine were added to a stirrer at 25°C, stirred and mixed, then 10.6 g of the intermediate was continuously added, reacted at room temperature for 4 h, then heated to 85°C for 10 h, after the end of the reaction, cooled to room temperature, washed with saturated sodium bicarbonate solution and deionized water respectively, and dried to obtain a phosphorus modified benzimidazole;

[0032] S3. First, 7.62 g of sulfathiazole was dissolved in 140 mL of anhydrous ethanol, then 2.81 g of 5-hydroxymethylfurfural was added, stirred at 70°C for 6 h, then 6.44 g of DOPO was added and stirred at 80°C for 20 h, after reaction, cooled, washed with anhydrous ethanol, dried to obtain hydroxyl modified sulfathiazole;

[0033]

[0034] S4. 5.33 g of hydroxyl-modified sulfanilamide thiazole and 0.21 g of tetrabutylammonium bromide were added to 40 mL of epichlorohydrin, and reacted at 82°C for 5 h, then cooled to 60°C, and 1.24 g of a 20% by mass sodium hydroxide aqueous solution was further added, and ring closure reaction was performed at 65°C for 4 h, after which the reaction was cooled, suction filtered, and washed to obtain an epoxy sulfanilamide thiazole;

[0035]

[0036] S5. 65 parts by weight of a bisphenol A type epoxy resin was added to a stirrer, warmed to 160°C, and 6 parts by weight of a phosphorus-modified benzimidazole, 3 parts by weight of an epoxy sulfanilamide thiazole, and 4 parts by weight of a m-phenylenediamine curing agent were further added, and cured at 100°C for 2 h to obtain a phosphorus-containing flame-retardant epoxy resin.

[0037] Example 3

[0038] S1. 1.25 g of o-phenylenediamine and 95 mL of dichloromethane were mixed, and 1.21 g of phosphorus oxychloride was added at a temperature of 21°C, after which the temperature was raised to 53°C and refluxed for 5 h, after which the reaction was cooled to room temperature, washed with acetonitrile, and vacuum dried to constant weight to obtain an intermediate;

[0039] S2. 6.02 g of 2-mercaptobenzimidazole, 155 mL of acetonitrile, and 7 mL of triethylamine were added to a stirrer at 22°C, and the mixture was stirred, and then 9.8 g of the intermediate was further added, and reacted at room temperature for 4 h, and then warmed to 84°C and reacted for 9 h, after which the reaction was cooled to room temperature, washed with saturated sodium bicarbonate solution and deionized water, and dried to obtain a phosphorus-modified benzimidazole;

[0040] S3. 7.65 g of sulfanilamide thiazole was first dissolved in 145 mL of anhydrous ethanol, and then 2.83 g of 5-hydroxymethylfurfural was added, and stirred at 76°C for 7 h, and then 6.47 g of DOPO was added, and continuously stirred at 83°C for 22 h, and after the reaction, washed with anhydrous ethanol and dried to obtain a hydroxyl-modified sulfanilamide thiazole;

[0041] S4. 4.91 g of hydroxyl-modified sulfanilamide thiazole and 0.16 g of tetrabutylammonium bromide were added to 35 mL of epichlorohydrin, and reacted at 81°C for 5 h, then cooled to 57°C, and 1.22 g of a 20% by mass sodium hydroxide aqueous solution was further added, and ring closure reaction was performed at 63°C for 4 h, after which the reaction was cooled, suction filtered, and washed to obtain an epoxy sulfanilamide thiazole;

[0042] S5. 60 parts by weight of bisphenol A type epoxy resin was added into a stirrer, heated to 155°C, 5 parts by weight of phosphorus-containing modified benzimidazole, 3 parts by weight of epoxy sulfoxazole were continuously added, cooled to 94°C, 3 parts by weight of m-phenylenediamine curing agent was continuously added, cured at 100°C for 2h, and a phosphorus-containing flame-retardant epoxy resin was obtained.

[0043] Example 4

[0044] S1. 1.2g of o-phenylenediamine and 90mL of dichloromethane were mixed, 1.15g of phosphorus oxychloride was added at a temperature of 20°C, after the end of dropwise addition, the temperature was raised to 50°C and refluxed for 4h, after the reaction was completed, it was cooled to room temperature, then washed with acetonitrile, and dried under vacuum to constant weight to obtain an intermediate;

[0045] S2. 6.01g of 2-mercaptobenzimidazole, 150mL of acetonitrile and 6mL of triethylamine were added into a stirrer at 20°C, the mixture was stirred, then 9.5g of the intermediate was continuously added, reacted at room temperature for 3h, then heated to 80°C for 8h, after the reaction was completed, it was cooled to room temperature, washed with saturated sodium bicarbonate solution and deionized water respectively, and dried to obtain a phosphorus-containing modified benzimidazole;

[0046] S3. 7.66g of sulfathiazole was first dissolved in 150mL of anhydrous ethanol, then 2.88g of 5-hydroxymethylfurfural was added, stirred at 80°C for 8h, then 6.49g of DOPO was added, and continuously stirred at 85°C for 24h, after the reaction, it was cooled and washed with anhydrous ethanol, and dried to obtain a hydroxyl-modified sulfathiazole;

[0047] S4. 4.91g of hydroxyl-modified sulfathiazole and 0.16g of tetrabutylammonium bromide were added into 35mL of epichlorohydrin, reacted at 81°C for 5h, then cooled to 57°C, 1.22g of 20% mass concentration sodium hydroxide aqueous solution was continuously added, and a ring-closing reaction was carried out at 63°C for 4h, after the reaction was completed, it was cooled and filtered, and washed to obtain an epoxy sulfoxazole;

[0048] S5. 60 parts by weight of bisphenol A type epoxy resin was added into a stirrer, heated to 155°C, 5 parts by weight of phosphorus-containing modified benzimidazole, 3 parts by weight of epoxy sulfoxazole were continuously added, cooled to 94°C, 3 parts by weight of m-phenylenediamine curing agent was continuously added, cured at 100°C for 2h, and a phosphorus-containing flame-retardant epoxy resin was obtained.

[0049] Example 5

[0050] S1. 1.3 g of o-phenylenediamine and 100 mL of dichloromethane were mixed, and 1.26 g of phosphorus oxychloride was added at a temperature of 22°C, after the dropwise addition was completed, the temperature was raised to 55°C and refluxed for 6 h, after the reaction was completed, it was cooled to room temperature, then washed with acetonitrile, and dried under vacuum to constant weight to obtain an intermediate;

[0051] S2. 6.03 g of 2-mercaptobenzimidazole, 160 mL of acetonitrile and 8 mL of triethylamine were added to a stirrer at 25°C, the mixture was stirred, then 10.6 g of the intermediate was added, and the reaction was carried out at room temperature for 4 h, then the temperature was raised to 85°C and the reaction was carried out for 10 h, after the reaction was completed, it was cooled to room temperature, washed with saturated sodium bicarbonate solution and deionized water, and dried to obtain a phosphorus-modified benzimidazole;

[0052] S3. 7.65 g of sulfathiazole was first dissolved in 145 mL of anhydrous ethanol, then 2.83 g of 5-hydroxymethylfurfural was added, stirred at 76°C for 7 h, then 6.47 g of DOPO was added, and stirred at 83°C for 22 h, after the reaction, it was cooled, washed with anhydrous ethanol, and dried to obtain a hydroxyl-modified sulfathiazole;

[0053] S4. 4.91 g of the hydroxyl-modified sulfathiazole and 0.16 g of tetrabutylammonium bromide were added to 35 mL of epichlorohydrin, and the reaction was carried out at 81°C for 5 h, then the temperature was lowered to 57°C, 1.22 g of a 20% by mass sodium hydroxide aqueous solution was further added, and the ring closure reaction was carried out at 63°C for 4 h, after the reaction was completed, it was cooled, filtered, and washed to obtain an epoxy sulfathiazole;

[0054] S5. 50 parts by weight of a bisphenol A type epoxy resin was added to a stirrer, the temperature was raised to 150°C, 4 parts by weight of the phosphorus-modified benzimidazole, 2 parts by weight of the epoxy sulfathiazole, and 2 parts by weight of a m-phenylenediamine curing agent were further added, the temperature was lowered to 90°C, and the curing was carried out at 100°C for 2 h to obtain a phosphorus-containing flame-retardant epoxy resin.

[0055] Comparative Example 1

[0056] This comparative example is different from Example 5 in that the intermediate is used instead of the phosphorus-modified benzimidazole.

[0057] Comparative Example 2

[0058] This comparative example is different from Example 5 in that the sulfathiazole is used instead of the epoxy sulfathiazole.

[0059] Comparative Example 3

[0060] This comparative example is different from Example 5 in that the phosphorus-modified benzimidazole is not added.

[0061] Comparative Example 4

[0062] The comparative example is different from example 5 in that no epoxy sulfonamide thiazole is added.

[0063] The oxygen index of the epoxy resin is tested by using an oxygen index tester, and the combustion grade of the high-temperature-resistant epoxy resin is tested by using a horizontal and vertical combustion tester.

[0064] Table 1: Flame retardant test.

[0065]

[0066]

[0067] As shown in Table 1, examples 1-5 of the present application have better flame retardant effect compared with comparative examples 1-4.

[0068] The preferred embodiments of the present application disclosed above are only used to help explain the present application. The preferred embodiments do not describe all the details and limit the present application to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of the present application. The present application selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well understand and use the present application.

Claims

1. A phosphorus-containing flame-retardant epoxy resin, characterized by comprising, It comprises the following weight components: 50-65 parts by weight of bisphenol A type epoxy resin, 4-6 parts by weight of phosphorus-containing modified benzimidazole, 2-3 parts by weight of epoxy-based sulfathiazole, 2-4 parts by weight of m-phenylenediamine curing agent; The preparation method of the phosphorus-containing modified benzimidazole is: S1. 1.2-1.3g of o-phenylenediamine and 90-100mL of dichloromethane were mixed, 1.15-1.26g of phosphorus oxychloride was added at a temperature of 20-22℃, after the addition was completed, the temperature was raised to 50-55℃ and refluxed, after the reaction was completed, it was cooled to room temperature, then washed with acetonitrile and dried under vacuum to constant weight to obtain an intermediate; S2. 6.01-6.03g of 2-mercaptobenzimidazole, 150-160mL of acetonitrile and 6-8mL of catalyst were added to a stirrer at 20-25℃, the mixture was stirred, then 9.5-10.6g of the intermediate was added, the reaction was carried out at room temperature for 3-4h, then the temperature was raised to 80-85℃ and the reaction was carried out for 8-10h, after the reaction was completed, it was cooled to room temperature, washed with saturated sodium bicarbonate solution and deionized water respectively, and dried to obtain the phosphorus-containing modified benzimidazole; The preparation method of the epoxy-based sulfathiazole is: Step one: 7.62-7.66g of sulfathiazole was dissolved in 140-150mL of anhydrous ethanol, then 2.81-2.88g of 5-hydroxymethylfurfural was added, stirred at 70-80℃ for 6-8h, then 6.44-6.49g of DOPO was added and continuously stirred at 80-85℃ for 20-24h, after the reaction, it was cooled, washed with anhydrous ethanol and dried to obtain hydroxyl-modified sulfathiazole; Step two: 4.52-5.33g of hydroxyl-modified sulfathiazole and 0.11-0.21g of catalyst were added to 30-40mL of epichlorohydrin, the reaction was carried out at 80-82℃ for 4-5h, then the temperature was lowered to 55-60℃, 1.21-1.24g of sodium hydroxide aqueous solution was continuously added, the ring closure reaction was carried out at 60-65℃ for 3-4h, after the reaction was completed, it was cooled, filtered and washed to obtain the epoxy-based sulfathiazole.

2. The phosphorus-containing flame-retardant epoxy resin according to claim 1, characterized in that, The reflux reaction time in S1 is 4-6h.

3. The phosphorus-containing flame-retardant epoxy resin according to claim 1, characterized in that, The catalyst in S2 is triethylamine.

4. The phosphorus-containing flame-retardant epoxy resin according to claim 1, characterized in that, The catalyst in step two is tetrabutylammonium bromide.

5. The phosphorus-containing flame-retardant epoxy resin according to claim 1, characterized in that, The mass concentration of the sodium hydroxide aqueous solution in step two is 20%.

6. A process for the preparation of a phosphorus-containing flame-retardant epoxy resin as claimed in any one of claims 1 to 5, characterized in that, The preparation method of the phosphorus-containing flame-retardant epoxy resin is: bisphenol A type epoxy resin is added to a stirrer, the temperature is raised to 150-160℃, the phosphorus-containing modified benzimidazole and the epoxy-based sulfathiazole are continuously added, the temperature is cooled to 90-95℃, the m-phenylenediamine curing agent is continuously added, and the curing is carried out at 100℃ for 2h to obtain the phosphorus-containing flame-retardant epoxy resin.

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