Reactive DOPO derivative flame retardant and preparation method thereof

Abstract

The invention discloses a reactive DOPO derivative flame retardant and a preparation method thereof, and belongs to the field of flame retardant preparation. The chemical structural formula of the reactive DOPO derivative flame retardant is # imgabs0, and the reactive DOPO derivative flame retardant is synthesized by taking DOPO-HQ, phosphonitrilic chloride trimer and N, N-dimethyl ethanol quaternary ammonium salt as raw materials through a two-step method. The reactive DOPO derivative flame retardant has the advantages of stable chemical properties, good heat resistance, hydrolysis resistance, migration resistance, efficient flame retardance and the like, has good compatibility after being added into an epoxy resin matrix material, can effectively improve the flame retardance and mechanical properties of the material, and is wide in application range and good in market application prospect.

Description

Technical Field

[0001] The invention belongs to the field of flame retardant preparation, and particularly relates to a reactive DOPO derivative flame retardant and a preparation method thereof. Background Art

[0002] Flame retardants are functional additives that make polymers flame retardant. They are chemical substances that can prevent or slow down the combustion of materials. They exert their flame retardant effects through several mechanisms. Adding flame retardants to polymer materials or using them to modify polymers can effectively inhibit combustion and reduce fire risks. They are widely used in plastics, coatings, textiles, rubber, electronic appliances and other fields.

[0003] Flame retardants can be divided into additive and reactive types based on how they are added. Reactive flame retardants incorporate flame retardant elements into a substrate, then add a curing agent. After curing, the material becomes a link in the polymer chain, exhibiting high flame retardancy without precipitation. While providing a long-lasting flame retardant effect, it also maintains the resin's original thermal and mechanical properties, thus not affecting the subsequent processing of epoxy resins and their application in various fields.

[0004] The DOPO derivative DOPO-HQ (10-(2,5-dihydroxyphenyl)-10-hydrogen-9-oxa-10-phosphaphenanthrene-10-oxide) reacts with the epoxy group of the epoxy resin through the phenolic hydroxyl group and is chemically grafted onto the epoxy resin backbone to form an epoxy resin containing a phosphorus structure. This process does not change the basic classification of the epoxy resin, but can significantly improve its flame retardancy. Summary of the Invention

[0005] In response to the flammability problem of current epoxy resin flame retardants, the present invention proposes a reactive DOPO derivative flame retardant and a preparation method thereof. The reactive DOPO derivative flame retardant has good chemical stability, high heat resistance and flame retardant efficiency, and good compatibility with the epoxy resin matrix, making it particularly suitable for improving the flame retardant properties of epoxy resin systems.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a reactive DOPO derivative flame retardant, the chemical structure of which is shown in Formula I.

[0007]

[0008] In a second aspect, the present invention provides a method for preparing the reactive DOPO derivative flame retardant. The specific synthesis route is as follows:

[0009]

[0010] The specific steps are as follows: (1) Synthesis of flame retardant intermediate DHT: DOPO-HQ was dissolved in an organic solvent to prepare a DOPO-HQ / organic solvent solution. Hexachlorocyclotriphosphazene (HCCP) and an acid-binding agent were added to a three-necked flask. Under the conditions of magnetic stirring and condensation reflux, the DOPO-HQ / organic solvent solution was added dropwise at a constant temperature of 55-60°C. The titration rate was controlled to be one drop per 2-3 seconds. After the addition was completed, the reaction was continued for 10-12 hours to obtain the flame retardant intermediate DHT. (2) Synthesis of flame retardant DHN: After the reaction in step (1) is completed, the temperature is lowered to 50°C, and then N, N-dimethylethanol quaternary ammonium salt is added. The reaction is continued at a constant temperature of 50-55°C for 10-12 hours under the conditions of magnetic stirring and condensation reflux. The reaction is stopped when the solution turns milky white, and the solution is naturally cooled to room temperature. The white solid is then obtained by rotary evaporation, filtration, and multiple washings. The white solid is placed in an oven and dried at 80-110°C to obtain flame retardant DHN.

[0011] As a preferred embodiment of the present invention, in step (1), the constant temperature is controlled to be 60° C. and the reaction time is 12 h.

[0012] As a preferred embodiment of the present invention, in step (2), the constant temperature is controlled to be 55° C. and the reaction time is 12 h.

[0013] As a preferred embodiment of the present invention, the molar ratio of DOPO-HQ, hexachlorocyclotriphosphazene, and N,N-dimethylethanol quaternary ammonium salt is 3.0-3.2:1.0:3.1.

[0014] As a preferred embodiment of the present invention, in step (1), the acid binding agent is at least one of triethylamine, pyridine, potassium carbonate and 4-dimethylaminopyridine.

[0015] As a preferred embodiment of the present invention, in step (1), the organic solvent used is at least one of tetrahydrofuran, N,N-dimethylformamide, methanol, ethanol, acetone, acetonitrile and dichloromethane.

[0016] As a preferred embodiment of the present invention, in step (2), the solvent used for washing is at least one of methanol, ethanol, chloroform, acetonitrile, dichloromethane, tetrahydrofuran and acetone.

[0017] As a preferred embodiment of the present invention, in step (2), the temperature used for drying is 80°C.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects: (1) The reactive DOPO derivative flame retardant provided by the present invention has the advantages of stable chemical properties, good heat resistance, hydrolysis resistance, migration resistance and high flame retardancy. The reactive DOPO derivative flame retardant has good compatibility when added to epoxy resin matrix materials, can effectively improve the flame retardant properties and mechanical properties of the materials, has a wide range of applications, and has good market application prospects.

[0019] (2) The reactive DOPO derivative flame retardant provided by the present invention is prepared by a two-step method, which has many advantages such as a simple preparation process, low cost, and solvent recyclability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the infrared spectrum of the flame retardant intermediate DHT in Example 1; Figure 2 is an infrared spectrum of the reactive DOPO derivative flame retardant DHN in Example 1; Figure 3 1 is the XRD pattern of the reactive DOPO derivative flame retardant DHN in Example 1. DETAILED DESCRIPTION

[0021] The following is a clear and complete description of the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0022] Example 1 Preparation of reactive DOPO derivative flame retardant DHN: 0.3477 g of hexachlorocyclotriphosphazene was weighed and added to a three-necked flask, a magnet was added, and 0.3137 g of triethylamine was added as an acid binding agent; 1.0077 g of DOPO-HQ was placed in a beaker, 105 mL of tetrahydrofuran was measured, a DOPO-HQ / tetrahydrofuran solution was prepared, and the solution was added to a constant pressure burette. Titration was started at 60° C. under magnetic stirring and reflux, and the titration rate was controlled to be one drop per 2-3 seconds; after the titration was completed, the reaction was maintained under the above conditions for 12 hours; after the reaction was completed, the temperature was lowered to 50° C., 0.7011 g of N,N-dimethylethanol quaternary ammonium salt was weighed and added to the three-necked flask containing DHT, and the reaction was continued at 55° C. under magnetic stirring and reflux for 12 hours; the product was filtered, rotary evaporated, filtered with suction, washed, and dried to obtain a white solid powder, which is the reactive DOPO derivative flame retardant DHN of this example.

[0023] Example 2 Preparation of reactive DOPO derivative flame retardant DHN: Weigh 0.3477g hexachlorocyclotriphosphazene and add it to a three-necked flask, add a magnet, and add 0.3756g 4-dimethylaminopyridine as an acid binding agent; take 1.0077g DOPO-HQ and place it in a beaker, measure 35 mL N,N-dimethylformamide, prepare DOPO-HQ / N,N-dimethylformamide solution, add it to a constant pressure burette, and start titration at 60℃, magnetic stirring, and condensation reflux. The titration rate is controlled to be one drop per 2-3 seconds; after the titration is completed, maintain the above conditions for 12 hours; after the reaction is completed, the temperature is reduced to 50℃, and weigh 0.7011g N,N-dimethylethanol quaternary ammonium salt was added to a three-necked flask containing DHT, and the reaction was continued at 55°C under magnetic stirring and reflux for 12 hours. The product was filtered, rotary evaporated, filtered, washed, and dried to obtain a white solid powder, which is the reactive DOPO derivative flame retardant DHN of this embodiment.

[0024] Example 3 Preparation of the reactive DOPO derivative flame retardant DHN: 0.3477 g of hexachlorocyclotriphosphazene was weighed and added to a three-necked flask, a magnet was added, and 0.2452 g of pyridine was added as an acid-binding agent; 1.0077 g of DOPO-HQ was placed in a beaker, 155 mL of acetonitrile was measured, a DOPO-HQ / acetonitrile solution was prepared, and the solution was added to a constant pressure burette. Titration was started at 60°C with magnetic stirring and reflux, and the titration rate was controlled to be one drop per 2-3 seconds. After the titration was completed, the reaction was maintained under the above conditions for 12 hours. After the reaction was completed, the temperature was lowered to 50°C, 0.7011 g of N,N-dimethylethanol quaternary ammonium salt was weighed and added to the three-necked flask containing DHT, and the reaction was continued at 55°C with magnetic stirring and reflux for 12 hours. The product was filtered, rotary evaporated, filtered with suction, washed, and dried to obtain a white solid powder, which is the reactive DOPO derivative flame retardant DHN of this example.

[0025] Example 4 Preparation of the reactive DOPO derivative flame retardant DHN: 0.3477 g of hexachlorocyclotriphosphazene was weighed and added to a three-necked flask, a magnet was added, and 0.2211 g of potassium carbonate was added as an acid-binding agent; 1.0077 g of DOPO-HQ was placed in a beaker, 186 mL of acetone was measured, a DOPO-HQ / acetone solution was prepared, and the solution was added to a constant pressure burette. Titration was started at 60° C. under magnetic stirring and reflux, with a titration rate of one drop per 2-3 seconds; after the titration was completed, the reaction was maintained under the above conditions for 12 hours; after the reaction was completed, the temperature was lowered to 50° C., 0.7011 g of N,N-dimethylethanol quaternary ammonium salt was weighed and added to the three-necked flask containing DHT, and the reaction was continued at 55° C. under magnetic stirring and reflux for 12 hours; the product was filtered, rotary evaporated, filtered with suction, washed, and dried to obtain a white solid powder, which is the reactive DOPO derivative flame retardant DHN of this example.

[0026] Example 5 Preparation of epoxy resin flame-retardant composite material: Weigh 50g of epoxy resin E-51, add 15g of reactive DOPO derivative flame retardant DHN of Example 1, heat to fully disperse the flame retardant DHN in the matrix resin, and after cooling to room temperature, add 35g of curing agent D230. After the three are mixed evenly, a yellow-brown liquid is formed, which is quickly poured into a mold and cured at 100°C. After natural cooling and demolding, the flame retardant performance test and other comprehensive performance tests can be carried out.

[0027] The limiting oxygen index (LOI) value of the sample was measured according to ASTM D-2863 using a 5801 oxygen index meter (Suzhou, China). The sample dimensions were 120 mm long, 10 mm wide, and 4 mm thick. The vertical combustion (UL-94) rating of the sample was tested according to ASTM D-3801 using a CZF-3 vertical combustion tester (Nanjing, China). The sample dimensions were 120 mm long, 13 mm wide, and 3 mm thick. The epoxy resin flame-retardant composite material achieved an LOI value of 28.5%, achieving a UL-94 V-0 rating, demonstrating excellent flame retardancy.

[0028] Example 6 Preparation of epoxy resin flame-retardant composite material: Weigh 40g of epoxy resin E-51, add 25g of reactive DOPO derivative flame retardant DHN of Example 1, heat to fully disperse the flame retardant DHN in the matrix resin, and after cooling to room temperature, add 35g of curing agent D230. After the three are mixed evenly, a yellow-brown liquid is formed, which is quickly poured into a mold and cured at 100°C. After natural cooling and demolding, the flame retardant performance test and other comprehensive performance tests can be carried out.

[0029] The LOI values ​​of the samples were measured according to ASTM D-2863 using a 5801 oxygen index meter (Suzhou, China) with sample dimensions of 120 mm long, 10 mm wide, and 4 mm thick. The UL-94 rating of the samples was determined according to ASTM D-3801 using a CZF-3 vertical combustion tester (Nanjing, China) with sample dimensions of 120 mm long, 13 mm wide, and 3 mm thick. The epoxy flame-retardant composite material achieved an LOI of 31.3%, easily passing the UL-94 V-0 rating. The average reburn time after the first ignition was only 2.8 seconds, demonstrating rapid self-extinguishing properties.

[0030] Example 7 Preparation of epoxy resin flame-retardant composite material: Weigh 62.5g of epoxy resin E-51, add 2.5g of reactive DOPO derivative flame retardant DHN of Example 1, heat to fully disperse the flame retardant DHN in the matrix resin, and after cooling to room temperature, add 35g of curing agent D230. After the three are mixed evenly, a yellow-brown liquid is formed, which is quickly poured into a mold and cured at 100°C. After natural cooling and demolding, the flame retardant performance test and other comprehensive performance tests can be carried out.

[0031] The tensile strength of the samples was tested according to ASTM D-638 using a JHY-5000 electronic universal testing machine (Xiamen, China). The sample size was 80 mm long and 4 mm thick. The impact strength of the samples was tested according to GB / T 1843-2008 using a JHY-XJI-5.5D cantilever beam and simple supported beam combined impact testing machine (Xiamen, China). The sample size was 80 mm long, 10 mm wide, and 4 mm thick. The tensile strength and impact strength of pure epoxy resin were 61.2 MPa and 4.885 kJ / m, respectively. 2 When the addition amount of DHN is 2.5wt%, the tensile strength and impact strength of the flame retardant composite material reach 63.7MPa and 5.102kJ / m respectively. 2 , which were increased by 4.08% and 4.44% respectively compared with pure epoxy resin.

[0032] Example 8 Preparation of epoxy resin flame-retardant composite material: Weigh 60g of epoxy resin E-51, add 5g of reactive DOPO derivative flame retardant DHN of Example 3, heat to fully disperse the flame retardant DHN in the matrix resin, and after cooling to room temperature, add 35g of curing agent D230. After the three are mixed evenly, a yellow-brown liquid is formed, which is quickly poured into a mold and cured at 100°C. After natural cooling and demolding, the flame retardant performance test and other comprehensive performance tests can be carried out.

[0033] The tensile strength of the samples was tested according to the ASTM D-638 test standard using a JHY-5000 electronic universal testing machine (Xiamen, China). The samples were 80 mm long and 4 mm thick. The impact strength of the samples was tested according to the GB / T 1843-2008 test standard using a JHY-XJI-5.5D cantilever beam and simply supported beam combined impact testing machine (Xiamen, China). The samples were 80 mm long, 10 mm wide, and 4 mm thick. The tensile strength and impact strength of the flame-retardant composite material reached 62.1 MPa and 4.926 kJ / m2, respectively, which are 1.47% and 0.84% ​​higher than those of pure epoxy resin, respectively. This shows that a small amount of flame retardant DHN can effectively improve the mechanical properties of epoxy resin.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the technical solution and conceptual invention of the present invention should be included in the scope of protection of the present invention.

Claims

1. A reactive DOPO derivative flame retardant, characterized in that: Its chemical structure is shown in Formula I:

2. A method for preparing a reactive DOPO derivative flame retardant, characterized in that: The specific synthetic route is as follows: ； ； The specific steps are as follows: (1) Synthesis of flame retardant intermediate DHT: DOPO-HQ was dissolved in an organic solvent to prepare a DOPO-HQ / organic solvent solution. Hexachlorocyclotriphosphazene (HCCP) and an acid-binding agent were added to a three-necked flask. Under the conditions of magnetic stirring and condensation reflux, the DOPO-HQ / organic solvent solution was added dropwise at a constant temperature of 55-60°C. The titration rate was controlled to be one drop per 2-3 seconds. After the addition was completed, the reaction was continued for 10-12 hours to obtain the flame retardant intermediate DHT. (2) Synthesis of flame retardant DHN: After the reaction in step (1) is completed, the temperature is lowered to 50°C, and then N, N-dimethylethanol quaternary ammonium salt is added. The reaction is continued at a constant temperature of 50-55°C for 10-12 hours under the conditions of magnetic stirring and condensation reflux. The reaction is stopped when the solution turns milky white, and the solution is naturally cooled to room temperature. The white solid is then obtained by rotary evaporation, filtration, and multiple washings. The white solid is placed in an oven and dried at 80-110°C to obtain flame retardant DHN.

3. The method for preparing a reactive DOPO derivative flame retardant according to claim 2, characterized in that: In step (1), the constant temperature is controlled at 60°C and the reaction time is 12 hours.

4. The method for preparing a reactive DOPO derivative flame retardant according to claim 2, wherein: In step (2), the constant temperature is controlled at 55°C and the reaction time is 12 hours.

5. The method for preparing a reactive DOPO derivative flame retardant according to claim 2, characterized in that: The molar ratio of the DOPO-HQ, hexachlorocyclotriphosphazene and N,N-dimethylethanol quaternary ammonium salt is 3.0-3.2:1.0:3.

1.

6. The method for preparing a reactive DOPO derivative flame retardant according to claim 2, wherein: In step (1), the acid binding agent is at least one of triethylamine, pyridine, potassium carbonate and 4-dimethylaminopyridine.

7. The method for preparing a reactive DOPO derivative flame retardant according to claim 2, characterized in that: In step (1), the organic solvent used is at least one of tetrahydrofuran, N,N-dimethylformamide, methanol, ethanol, acetone, acetonitrile and dichloromethane.

8. The method for preparing a reactive DOPO derivative flame retardant according to claim 2, characterized in that: In step (2), the solvent used for washing is at least one of methanol, ethanol, chloroform, acetonitrile, dichloromethane, tetrahydrofuran and acetone.

9. The method for preparing a reactive DOPO derivative flame retardant according to claim 2, wherein: In step (2), the drying temperature is 80°C.

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