Phosphorus-containing flame-retardant epoxy resin and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses phosphorus-containing flame-retardant epoxy resin and a preparation method thereof, the phosphorus-containing flame-retardant epoxy resin comprises the following components by weight: 50-65 parts of bisphenol A epoxy resin, 4-6 parts of phosphorus-containing modified benzimidazole, 2-3 parts of epoxy sulfathiazole, and 2-4 parts of a m-phenylenediamine curing agent. The preparation method comprises the following steps: adding bisphenol A epoxy resin into a stirrer, heating, continuously adding phosphorus-containing modified benzimidazole and epoxy sulfathiazole, cooling, continuously adding a m-phenylenediamine curing agent, and curing to obtain the phosphorus-containing flame-retardant epoxy resin. The phosphorus-containing flame-retardant epoxy resin disclosed by the invention has a relatively good flame-retardant effect.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and specifically relates to a phosphorus-containing flame-retardant epoxy resin and a preparation method thereof. Background Art

[0002] Epoxy resin is an important thermosetting polymer material, which has excellent mechanical properties, adhesiveness, chemical corrosion resistance and electrical insulation properties, and is widely used in fields such as electronic packaging, composite materials, coatings, adhesives, etc. However, the limiting oxygen index (LOI) of traditional epoxy resins is usually only 19% - 21%, which is highly flammable and greatly limits its applications. For example, in the Chinese invention patent application with the publication number CN110790897A, an epoxy resin and a preparation method thereof, the epoxy resin of the present invention has good anti-corrosion ability and mechanical strength, but its flame-retardant effect has not been improved. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides a phosphorus-containing flame-retardant epoxy resin and a preparation method thereof, which have good flame-retardant effects.

[0004] To achieve the above object, the present invention provides the following technical solutions: A phosphorus-containing flame-retardant epoxy resin, comprising the following weight components: 50 - 65 parts by weight of bisphenol A epoxy resin, 4 - 6 parts by weight of phosphorus-modified benzimidazole, 2 - 3 parts by weight of epoxy group sulfathiazole, and 2 - 4 parts by weight of m-phenylenediamine curing agent.

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

[0006] S1. Mix 1.2 - 1.3 g of o-phenylenediamine and 90 - 100 mL of dichloromethane, add 1.15 - 1.26 g of phosphorus oxychloride under the condition of a temperature of 20 - 22 °C. After the dropping is completed, raise the temperature to 50 - 55 °C for reflux reaction. After the reaction is completed, cool to room temperature, then wash with acetonitrile and vacuum dry to constant weight to obtain an intermediate.

[0007]

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

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

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

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

[0012] Step 1: First, dissolve 7.62 - 7.66 g of sulfathiazole in 140 - 150 mL of absolute ethanol, then add 2.81 - 2.88 g of 5 - hydroxymethylfurfural, stir at 70 - 80 °C for 6 - 8 h, then add 6.44 - 6.49 g of DOPO, and continuously stir at 80 - 85 °C for 20 - 24 h. After the reaction, cool, wash with absolute ethanol, and dry to obtain hydroxyl - modified sulfathiazole;

[0013] Step 2: Add 4.52 - 5.33 g of hydroxyl - modified sulfathiazole and 0.11 - 0.21 g of the catalyst to 30 - 40 mL of epichlorohydrin, react at 80 - 82 °C for 4 - 5 h, then cool to 55 - 60 °C, and continue to add 1.21 - 1.24 g of sodium hydroxide aqueous solution. Carry out a ring - closing reaction at 60 - 65 °C for 3 - 4 h. After completion, cool, filter by suction, and wash to obtain epoxy group sulfathiazole.

[0014] Further, in Step 2, the catalyst is tetrabutylammonium bromide.

[0015] Further, the mass concentration of the sodium hydroxide aqueous solution in Step 2 is 20%.

[0016] Further, the preparation method of the phosphorus - containing flame - retardant epoxy resin is as follows: Add bisphenol A epoxy resin to a stirrer, heat up to 150 - 160 °C, continue to add phosphorus - containing modified benzimidazole and epoxy group sulfathiazole, cool to 90 - 95 °C, continue to add m - phenylenediamine curing agent, and cure at 100 °C for 2 h to obtain the phosphorus - containing flame - retardant epoxy resin.

[0017] In the present invention, bisphenol A epoxy resin is added to a stirrer, heated up, phosphorus - containing modified benzimidazole and epoxy group sulfathiazole are continuously added thereto, cooled, m - phenylenediamine curing agent is continuously added, and cured to obtain the phosphorus - containing flame - retardant epoxy resin.

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

[0019] Phosphorus, sulfur and nitrogen contained in phosphorus-modified benzimidazole and epoxysulfathiazole all have good flame retardant effects. Phosphorus can generate polyphosphoric acid and metaphosphoric acid with strong dehydration when burning. Since polyphosphoric acid and metaphosphoric acid are not easy to volatilize, they form a dense protective layer on the surface resin material, thus playing a flame retardant effect; sulfur can promote the formation of a carbon layer on the surface of the material at high temperature, isolate oxygen, and thus slow down the combustion speed; nitrogen can generate difficult-to-burn gas when heated, which can not only dilute the concentration of flammable gas, but also take away some heat, further limiting the combustion of the material. The Schiff base structure (-CH=N-) in epoxysulfathiazole has excellent carbonization performance, which can promote carbonization when epoxy resin burns and play a good flame retardant effect. During the curing process, the benzimidazole structure in the phosphorus-modified benzimidazole and the active secondary amine in the epoxysulfathiazole can catalyze the curing of the epoxy resin and form a curing system with the curing agent. The epoxy group in the epoxysulfathiazole also participates in the curing reaction, which improves the compatibility between them and makes the flame retardant elements more evenly distributed in the resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the hydrogen NMR spectrum of phosphorus-modified benzimidazole.

[0021] Figure 2 This is the H NMR spectrum of epoxysulfathiazole. 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, and 1.15 g of phosphorus oxychloride was added at 20 ° C. After the addition was completed, the temperature was raised to 50 ° C and refluxed for 4 h. After the reaction was completed, it was cooled to room temperature, then washed with acetonitrile, and vacuum dried to constant weight to obtain an intermediate;

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

[0026] S3. First, dissolve 7.62 g of sulfathiazole in 140 mL of absolute ethanol, then add 2.81 g of 5-hydroxymethylfurfural, stir at 70 °C for 6 h, then add 6.44 g of DOPO, and continuously stir at 80 °C for 20 h. After the reaction, cool it, wash it with absolute ethanol, and dry it to obtain hydroxyl-modified sulfathiazole;

[0027] S4. Add 4.52 g of hydroxyl-modified sulfathiazole and 0.11 g of tetrabutylammonium bromide to 30 mL of epichlorohydrin, react at 80 °C for 4 h, then cool down to 55 °C, and continue to add 1.21 g of 20% sodium hydroxide aqueous solution to it. Carry out a ring-closure reaction at 60 °C for 3 h. After completion, cool it, filter it by suction, and wash it to obtain epoxy-group sulfathiazole;

[0028] S5. Add 50 parts by weight of bisphenol A epoxy resin to a stirrer, heat up to 150 °C, continue to add 4 parts by weight of phosphorus-containing modified benzimidazole and 2 parts by weight of epoxy-group sulfathiazole to it, cool down to 90 °C, and continue to add 2 parts by weight of m-phenylenediamine curing agent. Cure at 100 °C for 2 h to obtain phosphorus-containing flame-retardant epoxy resin.

[0029] Example 2

[0030] S1. Mix 1.3 g of o-phenylenediamine and 100 mL of dichloromethane, add 1.26 g of phosphorus oxychloride at a temperature of 22 °C. After the dropping is completed, raise the temperature to 55 °C and reflux for 6 h. After the reaction, cool it to room temperature, then wash it with acetonitrile and vacuum dry it to constant weight to obtain an intermediate;

[0031] S2. At 25 °C, add 6.03 g of 2-mercaptobenzimidazole, 160 mL of acetonitrile and 8 mL of triethylamine to a stirrer, stir and mix, then continue to add 10.6 g of the intermediate to it, react at room temperature for 4 h, then raise the temperature to 85 °C and react for 10 h. After completion, cool it to room temperature, wash it with saturated sodium bicarbonate solution and deionized water respectively, and dry it to obtain phosphorus-containing modified benzimidazole;

[0032] S3. First, dissolve 7.66 g of sulfathiazole in 150 mL of absolute ethanol, then add 2.88 g of 5-hydroxymethylfurfural, stir at 80 °C for 8 h, then add 6.49 g of DOPO, and continuously stir at 85 °C for 24 h. After the reaction, cool it, wash it with absolute ethanol, and dry it to obtain hydroxyl-modified sulfathiazole;

[0033]

[0034] S4. Add 5.33 g of hydroxyl-modified sulfathiazole and 0.21 g of tetrabutylammonium bromide to 40 mL of epichlorohydrin, react at 82 °C for 5 h, then cool to 60 °C, and continue to add 1.24 g of 20% sodium hydroxide aqueous solution thereto. Carry out a ring-closing reaction at 65 °C for 4 h. After completion, cool, filter by suction, and wash to obtain epoxy-group sulfathiazole;

[0035]

[0036] S5. Add 65 parts by weight of bisphenol A epoxy resin to a stirrer, heat up to 160 °C, and continue to add 6 parts by weight of phosphorus-containing modified benzimidazole and 3 parts by weight of epoxy-group sulfathiazole. Cool to 95 °C, and then continue to add 4 parts by weight of m-phenylenediamine curing agent. Cure at 100 °C for 2 h to obtain phosphorus-containing flame-retardant epoxy resin.

[0037] Example 3

[0038] S1. Mix 1.25 g of o-phenylenediamine and 95 mL of dichloromethane, add 1.21 g of phosphorus oxychloride at 21 °C. After the dropping is completed, raise the temperature to 53 °C and reflux for 5 h. After the reaction is completed, cool to room temperature, then wash with acetonitrile and vacuum dry to constant weight to obtain an intermediate;

[0039] S2. At 22 °C, add 6.02 g of 2-mercaptobenzimidazole, 155 mL of acetonitrile and 7 mL of triethylamine to a stirrer, stir and mix, and then continue to add 9.8 g of the intermediate thereto. React at room temperature for 4 h, then raise the temperature to 84 °C and react for 9 h. After completion, cool to room temperature, wash with saturated sodium bicarbonate solution and deionized water respectively, and dry to obtain phosphorus-containing modified benzimidazole;

[0040] S3. First dissolve 7.65 g of sulfathiazole in 145 mL of absolute ethanol, then add 2.83 g of 5-hydroxymethylfurfural, stir at 76 °C for 7 h, then add 6.47 g of DOPO, and continue to stir at 83 °C for 22 h. After the reaction, cool, wash with absolute ethanol, and dry to obtain hydroxyl-modified sulfathiazole;

[0041] S4. Add 4.91 g of hydroxyl-modified sulfathiazole and 0.16 g of tetrabutylammonium bromide to 35 mL of epichlorohydrin, react at 81 °C for 5 h, then cool to 57 °C, and continue to add 1.22 g of 20% sodium hydroxide aqueous solution thereto. Carry out a ring-closing reaction at 63 °C for 4 h. After completion, cool, filter by suction, and wash to obtain epoxy-group sulfathiazole;

[0042] S5. Add 60 parts by weight of bisphenol A epoxy resin to a stirrer, heat up to 155 °C, and then continue to add 5 parts by weight of phosphorus-modified benzimidazole and 3 parts by weight of epoxy group-containing sulfathiazole. Cool to 94 °C, and then continue to add 3 parts by weight of m-phenylenediamine curing agent. Cure at 100 °C for 2 h to obtain a phosphorus-containing flame-retardant epoxy resin.

[0043] Example 4

[0044] S1. Mix 1.2 g of o-phenylenediamine and 90 mL of dichloromethane, and add 1.15 g of phosphorus oxychloride at 20 °C. After the addition is complete, raise the temperature to 50 °C and reflux for 4 h. After the reaction is completed, cool to room temperature, then wash with acetonitrile and vacuum dry to constant weight to obtain an intermediate.

[0045] S2. At 20 °C, add 6.01 g of 2-mercaptobenzimidazole, 150 mL of acetonitrile and 6 mL of triethylamine to a stirrer, stir and mix, and then continue to add 9.5 g of the intermediate. React at room temperature for 3 h, then raise the temperature to 80 °C and react for 8 h. After completion, cool to room temperature, wash with saturated sodium bicarbonate solution and deionized water respectively, and dry to obtain phosphorus-modified benzimidazole.

[0046] S3. First dissolve 7.66 g of sulfathiazole in 150 mL of absolute ethanol, then add 2.88 g of 5-hydroxymethylfurfural, stir at 80 °C for 8 h, then add 6.49 g of DOPO, and continue to stir at 85 °C for 24 h. After the reaction, cool, wash with absolute ethanol, and dry to obtain hydroxy-modified sulfathiazole.

[0047] S4. Add 4.91 g of hydroxy-modified sulfathiazole and 0.16 g of tetrabutylammonium bromide to 35 mL of epichlorohydrin, react at 81 °C for 5 h, then cool to 57 °C, and continue to add 1.22 g of 20% sodium hydroxide aqueous solution. Carry out a ring-closing reaction at 63 °C for 4 h. After completion, cool, filter by suction, and wash to obtain epoxy group-containing sulfathiazole.

[0048] S5. Add 60 parts by weight of bisphenol A epoxy resin to a stirrer, heat up to 155 °C, and then continue to add 5 parts by weight of phosphorus-modified benzimidazole and 3 parts by weight of epoxy group-containing sulfathiazole. Cool to 94 °C, and then continue to add 3 parts by weight of m-phenylenediamine curing agent. Cure at 100 °C for 2 h to obtain a phosphorus-containing flame-retardant epoxy resin.

[0049] Example 5

[0050] S1. Mix 1.3 g of o-phenylenediamine with 100 mL of dichloromethane. At a temperature of 22 °C, add 1.26 g of phosphorus oxychloride. After the dropping is completed, raise the temperature to 55 °C and reflux for 6 h. After the reaction is completed, cool to room temperature, then wash with acetonitrile and vacuum dry to constant weight to obtain an intermediate;

[0051] S2. At 25 °C, add 6.03 g of 2-mercaptobenzimidazole, 160 mL of acetonitrile and 8 mL of triethylamine to a stirrer, stir and mix, then continue to add 10.6 g of the intermediate thereto, react at room temperature for 4 h, then raise the temperature to 85 °C and react for 10 h. After completion, cool to room temperature and wash with saturated sodium bicarbonate solution and deionized water respectively, and dry to obtain phosphorus-modified benzimidazole;

[0052] S3. First dissolve 7.65 g of sulfathiazole in 145 mL of absolute ethanol, then add 2.83 g of 5-hydroxymethylfurfural, stir at 76 °C for 7 h, then add 6.47 g of DOPO and continue to stir at 83 °C for 22 h. After the reaction, cool, wash with absolute ethanol and dry to obtain hydroxy-modified sulfathiazole;

[0053] S4. Add 4.91 g of hydroxy-modified sulfathiazole and 0.16 g of tetrabutylammonium bromide to 35 mL of epichlorohydrin, react at 81 °C for 5 h, then cool to 57 °C, and continue to add 1.22 g of a 20% sodium hydroxide aqueous solution thereto, and carry out a ring-closure reaction at 63 °C for 4 h. After completion, cool, filter by suction and wash to obtain epoxy-group sulfathiazole;

[0054] S5. Add 50 parts by weight of bisphenol A epoxy resin to a stirrer, raise the temperature to 150 °C, continue to add 4 parts by weight of phosphorus-modified benzimidazole and 2 parts by weight of epoxy-group sulfathiazole thereto, cool to 90 °C, and continue to add 2 parts by weight of m-phenylenediamine curing agent, and cure at 100 °C for 2 h to obtain a phosphorus-containing flame-retardant epoxy resin.

[0055] Comparative Example 1

[0056] The difference between this comparative example and Example 5 is that the intermediate is used instead of phosphorus-modified benzimidazole.

[0057] Comparative Example 2

[0058] The difference between this comparative example and Example 5 is that sulfathiazole is used instead of epoxy-group sulfathiazole.

[0059] Comparative Example 3

[0060] The difference between this comparative example and Example 5 is that phosphorus-modified benzimidazole is not added

[0061] Comparative Example 4

[0062] This comparative example is different from Example 5 in that epoxy sulfathiazole is not added.

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

[0064] Table 1: Flame retardancy test.

[0065]

[0066]

[0067] As can be seen from Table 1, Examples 1-5 of the present invention have better flame retardancy effects compared to Comparative Examples 1-4.

[0068] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can well understand and utilize the present invention.

Claims

1. A phosphorus-containing flame-retardant epoxy resin, characterized in that, It includes the following weight components: 50-65 parts by weight of bisphenol A epoxy resin, 4-6 parts by weight of phosphorus-modified benzimidazole, 2-3 parts by weight of epoxy sulfathiazole, and 2-4 parts by weight of m-phenylenediamine curing agent.

2. The phosphorus-containing flame-retardant epoxy resin according to claim 1, wherein The preparation method of the phosphorus-modified benzimidazole is as follows: S1. Mix 1.2-1.3 g of o-phenylenediamine and 90-100 mL of dichloromethane, add 1.15-1.26 g of phosphorus oxychloride under the condition of a temperature of 20-22 °C. After the dropping is completed, raise the temperature to 50-55 °C for reflux reaction. After the reaction is completed, cool to room temperature, then wash with acetonitrile and vacuum dry to constant weight to obtain an intermediate. S2. At 20-25 °C, add 6.01-6.03 g of 2-mercaptobenzimidazole, 150-160 mL of acetonitrile and 6-8 mL of a catalyst to a stirrer, stir and mix, then continue to add 9.5-10.6 g of the intermediate thereto, react at room temperature for 3-4 h, then raise the temperature to 80-85 °C and react for 8-10 h. After completion, cool to room temperature, wash with saturated sodium bicarbonate solution and deionized water respectively, and dry to obtain phosphorus-modified benzimidazole.

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

4. The phosphorus-containing flame-retardant epoxy resin according to claim 2, wherein The catalyst in S2 is triethylamine.

5. The phosphorus-containing flame-retardant epoxy resin according to claim 1, wherein The preparation method of the epoxy sulfathiazole is as follows: Step 1: First dissolve 7.62-7.66 g of sulfathiazole in 140-150 mL of absolute ethanol, then add 2.81-2.88 g of 5-hydroxymethylfurfural, stir at 70-80 °C for 6-8 h, then add 6.44-6.49 g of DOPO, and continuously stir at 80-85 °C for 20-24 h. After the reaction, cool, wash with absolute ethanol, and dry to obtain hydroxy-modified sulfathiazole. Step 2: Add 4.52-5.33 g of hydroxy-modified sulfathiazole and 0.11-0.21 g of a catalyst to 30-40 mL of epichlorohydrin, react at 80-82 °C for 4-5 h, then cool to 55-60 °C, continue to add 1.21-1.24 g of sodium hydroxide aqueous solution thereto, and carry out a ring-closure reaction at 60-65 °C for 3-4 h. After completion, cool, filter by suction, and wash to obtain epoxy sulfathiazole.

6. The phosphorus-containing flame-retardant epoxy resin according to claim 5, wherein The catalyst in Step 2 is tetrabutylammonium bromide.

7. The phosphorus-containing flame-retardant epoxy resin according to claim 5, wherein The mass concentration of the sodium hydroxide aqueous solution in Step 2 is 20%.

8. A preparation method of a phosphorus-containing flame-retardant epoxy resin according to any one of claims 1-7, characterized in that, The preparation method of the phosphorus-containing flame-retardant epoxy resin is as follows: Add bisphenol A epoxy resin to a stirrer, raise the temperature to 150-160 °C, continue to add phosphorus-modified benzimidazole and epoxy sulfathiazole thereto, cool to 90-95 °C, continue to add m-phenylenediamine curing agent, and cure at 100 °C for 2 h to obtain the phosphorus-containing flame-retardant epoxy resin.

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