A bio-based DOPO derivative flame retardant, its preparation method and application

Abstract

The present invention discloses a bio-based DOPO derivative flame retardant and its preparation method and application. The specific steps of the preparation method are as follows: S1. Weigh DOPO into a container, add a solvent, and stir and mix evenly; S2. Add curcumin and triethylamine into the container and stir evenly under a stirrer; S3. Drop carbon tetrachloride into the container under stirring, and control the temperature within 10 °C during the addition process; S4. React at room temperature for 8 to 12 h; S5. Extract and wash the reaction solution successively with hydrochloric acid, sodium bicarbonate, and deionized water to obtain a viscous liquid in the lower layer; S6. Perform vacuum distillation to obtain a product DOPO-CUR dried in vacuo. In the present invention, when the phosphorus content of DOPO-CUR in epoxy resin only reaches 0.41%, the epoxy resin can reach LOI 32.6% and UL94 V-0 level, and at the same time, the epoxy resin can still maintain good mechanical properties.

Description

Technical Field

[0001] The present invention relates to a bio - based DOPO derivative flame retardant, its preparation method and application, belonging to the technical field of flame retardants. Background Technique

[0002] As a kind of thermosetting plastics, epoxy resin has many advantages and is widely used. However, it has the characteristic of being flammable, so flame retardants are needed to flame - retard epoxy resin.

[0003] Halogen - containing flame retardants are the first kind of flame retardants to be studied. Without changing various properties of the resin matrix, they can also exhibit high - efficiency flame retardancy. However, the large amount of toxic and harmful gases and smoke released during their combustion pose obvious hazards to people's physical health and the natural environment. Therefore, various green and non - toxic environmental - friendly flame retardants need to be developed to replace traditional halogen - containing flame retardants. Phosphorus - containing flame retardants are the most popular type of flame retardants. However, although inorganic phosphorus - based flame retardants can provide flame retardant ability in epoxy resin, due to their poor compatibility with epoxy resin, the flame retardant efficiency is reduced and the mechanical properties decrease significantly, which is unacceptable in actual production and life. Therefore, the organic phosphorus - based flame retardant DOPO has attracted people's attention. However, a single DOPO flame retardant system often requires the addition of a large amount of flame retardant, and the large addition of DOPO will affect the properties such as the mechanical strength of the material. With the increasing requirement for the balance between the flame retardant performance and the overall performance of epoxy resin, constructing a composite system is more conducive to maintaining the overall performance index of the material. Due to the structure and composition of bio - based modified flame retardants themselves, they have the characteristic of rapid char formation, which can greatly improve the combustion resistance of epoxy resin. Therefore, bio - based derivative flame retardants have attracted much attention from researchers. However, bio - based flame retardants also face many problems, such as complex preparation processes, the need to add a large amount to achieve the desired effect, and mostly low thermal stability. So there is still a challenging problem of how to effectively improve the fire - proof performance of epoxy resin at a low addition amount.

[0004] Therefore, it is necessary to design a new bio - based flame retardant to maintain high flame retardant ability and mechanical properties of epoxy resin at a low addition amount. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a bio - based DOPO derivative flame retardant, its preparation method and application, to solve the technical problems of large addition amount of flame retardant and complex synthesis process proposed in the background technique during the preparation of flame - retarded epoxy resin, and the technical problems of poor mechanical properties and poor flame retardant efficiency of the prepared flame - retarded epoxy resin.

[0006] To solve the above - mentioned technical problems, the present invention provides a bio - based DOPO derivative flame retardant, and the structural formula of this flame retardant is Abbreviation: DOPO-CUR.

[0007] The preparation method of a bio-based DOPO derivative flame retardant according to the present invention is specifically as follows:

[0008] S1. Weigh DOPO in a container, add a solvent, and stir to mix evenly;

[0009] S2. Add curcumin and triethylamine to the container and stir evenly under a stirrer;

[0010] S3. Drop carbon tetrachloride into the container under stirring, and control the temperature within 10 °C during the dropping process;

[0011] S4. React at room temperature for 8 - 12 h;

[0012] S5. Extract and wash the reaction solution successively with hydrochloric acid, sodium bicarbonate, and deionized water to obtain a viscous liquid at the bottom layer;

[0013] S6. Subject the separated viscous liquid at the bottom layer to vacuum distillation to remove the solvent in the reaction, and obtain the product DOPO-CUR after precipitation and vacuum drying.

[0014] Preferably, in S2, the molar ratio of curcumin to DOPO is 1:1.8 - 2.2, and the molar ratio of triethylamine to DOPO is 1:0.8 - 1.2; in S3, the molar ratio of carbon tetrachloride to DOPO is 1:0.8 - 1.2.

[0015] Preferably, the molar ratio of curcumin, DOPO, carbon tetrachloride, and triethylamine is 1:2:2:2.

[0016] Preferably, the solvent is one or more of dichloromethane, ethyl acetate, acetonitrile, tetrahydrofuran, and chloroform.

[0017] Preferably, the mass of the solvent used is 3 - 8 times the mass of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0018] Preferably, in S5, the concentration of hydrochloric acid used for extraction and washing is 0.05 - 0.15 mol / L, and the concentration of sodium bicarbonate used for extraction and washing is 0.05 - 0.15 mol / L; each of hydrochloric acid, sodium bicarbonate, and deionized water is used for extraction and washing 2 - 3 times.

[0019] Preferably, the stirrer is a heating magnetic stirrer; in S3, a constant pressure dropping funnel is used for dropping during the dropping process.

[0020] The present invention also provides an application of a bio-based DOPO derivative flame retardant. The bio-based DOPO derivative flame retardant DOPO-CUR is used to prepare a flame-retardant epoxy resin. Among them, the bio-based DOPO derivative flame retardant DOPO-CUR is the bio-based DOPO derivative flame retardant DOPO-CUR described above. Alternatively, the bio-based DOPO derivative flame retardant DOPO-CUR is prepared by the preparation method described above.

[0021] Preferably, the epoxy resin and DOPO-CUR are stirred at 120-150 °C until a uniform solution is obtained, 4,4'-diaminodiphenylmethane is added and stirred until transparent, then poured into a mold, first vacuum dried at 90-110 °C for 2-3 h, and then vacuum dried at 140-160 °C for 3-5 h to obtain the epoxy resin containing DOPO-CUR.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. The present invention synthesizes curcumin and DOPO to prepare a bio-based DOPO derivative flame retardant DOPO-CUR, which solves the technical problems of poor flame retardant performance, high addition amount and complex synthesis process of existing flame retardants. The flame retardant of the present invention has good flame retardant effect, and has the advantages of low smoke, non-toxic and high thermal stability.

[0024] 2. The flame retardant of the present invention has good compatibility with epoxy resin and can maintain high chemical and thermal stability of epoxy resin.

[0025] 3. The present invention combines DOPO and curcumin in a reaction. The molecular structure contains both phosphorus and carbon elements for synergistic flame retardancy. Phosphorus and carbon elements can promote the formation of a carbon layer. The P-O and P=O of DOPO have a gas-phase flame retardant effect. The synergistic effect overcomes the deficiencies of single flame retardant elements, improves the heat resistance and high-temperature char formation rate, and can make the epoxy resin reach LOI 32.6% and UL94 V-0 level when the phosphorus content only reaches 0.41%. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0027] Figure 1 is the FTIR spectrum of a bio-based DOPO derivative flame retardant of the present invention;

[0028] Figure 2 is a bio-based DOPO derivative flame retardant of the present invention 31 P NMR spectrum;

[0029] Figure 3 is the 1 HNMR spectrum of a bio-based DOPO derivative flame retardant of the present invention;

[0030] Figure 4 is a comparison chart of the total smoke production of the epoxy resin containing 5% DOPO-CUR and the pure epoxy resin of the present invention;

[0031] Figure 5 is a comparison chart of the total heat release of the epoxy resin containing 5% DOPO-CUR and the pure epoxy resin of the present invention;

[0032] Figure 6 is a comparison chart of the heat release rate of the epoxy resin containing 5% DOPO-CUR and the pure epoxy resin of the present invention. Detailed implementation manners

[0033] The present invention will be described in detail below in conjunction with embodiments and drawings. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0034] Example 1

[0035] Take 10.16 g of DOPO and dissolve it in a 250 ml three-necked flask containing dichloromethane. Add a magnetic stirrer to the three-necked flask, place the three-necked flask in a heating magnetic stirrer, add ice cubes, control the temperature within 10 °C, and stir for 10 minutes; weigh 6.63 g of curcumin and 5.87 g of triethylamine, dissolve them in the above three-necked flask, weigh 8.92 g of carbon tetrachloride and add it dropwise to the three-necked flask through a constant pressure dropping funnel, controlling the temperature within 10 °C. After the dropping is completed, raise the temperature of the heating magnetic stirrer to room temperature, and the reaction time is 12 h; put the reaction product solution into a separating funnel, and extract and wash it with 0.1 mol / L dilute hydrochloric acid, 0.1 mol / L sodium bicarbonate, and deionized water respectively. After extraction and washing, recover the dichloromethane in the reaction by vacuum distillation of the separated lower viscous liquid, stop the reaction, and vacuum dry the reaction solution to obtain the target compound DOPO-CUR with a yield of 84.5%.

[0036] Analysis results of the infrared spectrum of the compound DOPO-CUR: FT-IR (KBr), v / cm -1 : 1595, 1506 and 1476 cm -1 attributed to the bending vibration absorption peaks of the benzene ring. A new characteristic absorption peak attributed to the P-O-C bond also appears at 932 cm -1 As shown in Figure 1 the change of the characteristic absorption peaks in the FTIR spectrum shown initially confirms the successful synthesis of the target product.

[0037] AsFigure 2 As shown, in the 31 P NMR spectrum of DOPO-CUR, a chemical shift peak at 6.92 ppm can be observed, indicating that a new chemical environment of P element appears in the synthesized DOPO-CUR. The NMR spectrum further confirms that the product synthesized in this experiment is consistent with the target product.

[0038] As Figure 3 shown, in the 1 HNMR spectrum of DOPO-CUR, a total of 30 H atoms can be observed in the peak region where H element is located, which is the same as the number of hydrogen atoms contained in the DOPO-CUR compound, proving that the synthesized product is consistent with the target product.

[0039] This article also provides an application of a bio-based DOPO derivative flame retardant. The bio-based DOPO derivative flame retardant DOPO-CUR is used to prepare a flame-retardant epoxy resin; wherein, the bio-based DOPO derivative flame retardant DOPO-CUR is the bio-based DOPO derivative flame retardant DOPO-CUR described above; or, the bio-based DOPO derivative flame retardant DOPO-CUR is prepared by the preparation method described above.

[0040] Stir the epoxy resin and DOPO-CUR at 120 - 150 °C until a homogeneous solution is obtained, add 4,4`-diaminodiphenylmethane and stir until transparent, pour it into a mold, first vacuum dry at 90 - 110 °C for 2 - 3 h, and then vacuum dry at 140 - 160 °C for 3 - 5 h to obtain an epoxy resin containing DOPO-CUR.

[0041] Compare epoxy resins with different contents of DOPO-CUR:

[0042] 1), Epoxy resin without DOPO-CUR:

[0043] In terms of flame retardant performance, the fire protection UL94 rating is not passed (NR); the LOI value is only 24.0%; the peak heat release rate (PHRR) is 541.3 kW / m 2 ; the total heat release (THR) is 78.5 MJ / m 2 ; the total smoke production (TSP) is 45.2 m 2 .

[0044] In terms of mechanical properties, the elastic modulus is 440.59 Mpa, the elongation at break is 10.45%, the tensile strength is 50.60 Mpa, the flexural modulus is 854.50 Mpa, the flexural strength is 48.65 Mpa, and the impact strength is 17.73 KJ / m 2 .

[0045] 2), Epoxy resin containing 1 wt% of DOPO-CUR:

[0046] In terms of flame retardant performance, the fire protection UL94 rating is not passed (NR); the LOI value is 28.1%.

[0047] 3), Epoxy resin containing 2 wt% of DOPO-CUR:

[0048] In terms of flame retardant performance, the fire protection UL94 rating is V-1; the LOI value is 30.2%.

[0049] 4), Epoxy resin containing 3 wt% of DOPO-CUR:

[0050] In terms of flame retardant performance, the fire protection UL94 rating is V-1; the LOI value is 30.7%.

[0051] 5), Epoxy resin containing 4 wt% of DOPO-CUR:

[0052] In terms of flame retardant performance, the fire protection UL94 rating is V-0; the LOI value is 31.2%.

[0053] 6), Epoxy resin containing 5 wt% of DOPO-CUR:

[0054] Reference Figure 4 、 Figure 5 、 Figure 6 , In terms of flame retardant performance, the fire protection UL94 rating is V-0; the LOI value is 32.6%; the peak heat release rate (PHRR) is 467.2 kW / m 2 ; the total heat release (THR) is 75.1 MJ / m 2 ; the total smoke production (TSP) is 43.6 m 2 .

[0055] In terms of mechanical properties, the elastic modulus is 693.72 Mpa, the elongation at break is 12.51%, the tensile strength is 75.98 Mpa, the flexural modulus is 1470.03 Mpa, the flexural strength is 76.13 Mpa, and the impact strength is 11.90 KJ / m 2 .

[0056] By comparison, it can be seen that the flame retardant performance is significantly improved, and the mechanical properties remain good.

[0057] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions and substitutions can still be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A bio-based DOPO derivative flame retardant, characterized in that: The structural formula of the flame retardant is Abbreviated as DOPO-CUR.

2. The method for preparing a bio-based DOPO derivative flame retardant according to claim 1, wherein: The specific steps are as follows: S1. Weigh DOPO into a container, add solvent, and stir to mix evenly; S2. Add curcumin and triethylamine into a container and stir evenly under a stirrer; S3. Add carbon tetrachloride dropwise into the container under stirring, and control the temperature within 10°C during the addition process; S4, react at room temperature for 8 to 12 hours; S5, extracting and washing the reaction solution with hydrochloric acid, sodium bicarbonate, and deionized water in sequence to obtain a lower layer of viscous liquid; S6. The separated lower layer of viscous liquid is distilled under reduced pressure to remove the solvent in the reaction, thereby obtaining the product DOPO-CUR which is precipitated and then dried under vacuum.

3. The method for preparing a bio-based DOPO derivative flame retardant according to claim 2, wherein: In the S2, the molar ratio of curcumin to DOPO is 1:1.8-2.2, and the molar ratio of triethylamine to DOPO is 1:0.8-1.2; in the S3, the molar ratio of carbon tetrachloride to DOPO is 1:0.8-1.

2.

4. The method for preparing a bio-based DOPO derivative flame retardant according to claim 3, wherein: The molar ratio of the curcumin, DOPO, carbon tetrachloride and triethylamine is 1:2:2:

2.

5. The method for preparing a bio-based DOPO derivative flame retardant according to claim 4, wherein: The solvent is one or more of dichloromethane, ethyl acetate, acetonitrile, tetrahydrofuran, and chloroform.

6. The method for preparing a bio-based DOPO derivative flame retardant according to claim 5, characterized in that: The mass of the solvent used is 3 to 8 times the mass of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

7. The method for preparing a bio-based DOPO derivative flame retardant according to claim 6, wherein: In said S5, the concentration of hydrochloric acid used for extraction and washing is 0.05-0.15 mol / L, and the concentration of sodium bicarbonate used for extraction and washing is 0.05-0.15 mol / L; the extraction and washing are performed 2-3 times with hydrochloric acid, sodium bicarbonate and deionized water respectively.

8. The method for preparing a bio-based DOPO derivative flame retardant according to claim 7, wherein: The stirrer is a heat-collecting magnetic stirrer; in S3, a constant pressure dropping funnel is used for dropwise addition.

9. An application of a bio-based DOPO derivative flame retardant, characterized in that: The bio-based DOPO derivative flame retardant DOPO-CUR is used to prepare a flame-retardant epoxy resin; wherein the bio-based DOPO derivative flame retardant DOPO-CUR is the bio-based DOPO derivative flame retardant DOPO-CUR according to claim 1; or, the bio-based DOPO derivative flame retardant DOPO-CUR is prepared by the preparation method according to any one of claims 2 to 8.

10. The use of a bio-based DOPO derivative flame retardant according to claim 9, characterized in that: The epoxy resin and DOPO-CUR were stirred at 120-150°C to obtain a uniform solution, 4,4'-diaminodiphenylmethane was added and stirred until transparent, and the mixture was poured into a mold. The mixture was first vacuum-dried at 90-110°C for 2-3 hours, and then vacuum-dried at 140-160°C for 3-5 hours to obtain the epoxy resin containing DOPO-CUR.

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