A DOPO-PDCAM flame retardant, its preparation method and modified epoxy resin

Abstract

A DOPO-PDCAM flame retardant, its preparation method and modified epoxy resin, which relate to the technical field of flame retardants. The aforementioned DOPO-PDCAM flame retardant has good flame retardant effects, and can also greatly inhibit the generation amount of smoke during the combustion of epoxy resin composites on the basis of the disclosed addition amount. Moreover, the yield of the DOPO-PDCAM flame retardant prepared by the preparation method of the present invention is relatively high, which can meet the requirements of industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of flame retardants, and particularly to a DOPO-PDCAM flame retardant, a preparation method thereof, and a modified epoxy resin. Background Art

[0002] In recent years, polymer materials have penetrated into all aspects of life. While polymer materials exhibit excellent properties, they also bring quite a number of safety problems. In 2019, the fire problem in China caused an economic loss of 3.612 billion yuan. Among them, fires caused by plastic products accounted for a considerable share. Therefore, the research and development and use of flame retardants are extremely urgent.

[0003] The intake of soot and harmful gases is a major killer in fires. Therefore, while improving the flame resistance of materials, the smoke suppression effect of materials is a key indicator of the comprehensive performance of flame retardants. In addition, with the continuous prominence of environmental problems in recent years, green environmental protection has become an important part of the national economic system. Chinese Patent CN110938236A discloses a DOPO-functionalized molybdenum disulfide flame retardant, which has a good flame retardant effect, but in terms of the degree of smoke suppression, the total smoke generation amount is reduced from 5.93 m 2 to only 4.42 m 2 , and the amount of flue gas generated is still relatively large, and the smoke suppression effect is not ideal enough. Summary of the Invention

[0004] One of the purposes of the present invention is to provide a DOPO-PDCAM flame retardant with a better smoke suppression effect.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions: A DOPO-PDCAM flame retardant, whose structural formula is:

[0006]

[0007] The method for preparing the above DOPO-PDCAM flame retardant includes the following steps:

[0008] First, prepare the intermediate PDCAM according to the following route:

[0009]

[0010] Second, prepare the DOPO-PDCAM flame retardant according to the following route:

[0011]

[0012] Preferably, in Step 1, an appropriate amount of acrylamide is weighed into a beaker, and acetonitrile is added to dissolve it. Then the dissolved acrylamide solution is transferred to a three-necked flask, and an appropriate amount of triethylamine is added dropwise to the three-necked flask. An appropriate amount of phenyl dichlorophosphate is dissolved in acetonitrile and transferred to a constant pressure dropping funnel. The phenyl dichlorophosphate solution is magnetically stirred and slowly added dropwise at 5°C, and the entire reaction device is reacted at 5°C for two hours. After two hours, the temperature is raised to 65°C and the reaction is stopped after 10 hours to obtain a pale yellow solution. The reaction solution is allowed to stand and cool, and colorless transparent needle-like crystals precipitate out. After suction filtration, the filter cake is washed three times with acetonitrile, and finally a transparent crystal-like intermediate PDCAM is obtained.

[0013] More preferably, in Step 2, an appropriate amount of PDCAM is weighed into a three-necked flask, and tetrahydrofuran is added to the three-necked flask as a reaction solvent. The magnetic stirring water bath is heated to 65°C to uniformly disperse PDCAM in the tetrahydrofuran solution. Then an appropriate amount of DOPO is weighed with weighing paper, dissolved in the tetrahydrofuran solution and transferred to the three-necked flask, and the mixture is refluxed for 12 hours to obtain a milky white solution. The reaction is stopped and allowed to stand for precipitation. At this time, a white precipitate appears at the bottom of the beaker. After the precipitate is suction filtered and washed, the filter cake is placed in a drying oven at 45°C for 4 hours to obtain a white product of DOPO-PDCAM flame retardant.

[0014] In addition, the present invention also provides a modified epoxy resin, which contains the above-mentioned DOPO-PDCAM flame retardant.

[0015] Preferably, the mass content of the DOPO-PDCAM flame retardant added to the modified epoxy resin is 1%-7%.

[0016] The DOPO-PDCAM flame retardant provided by the present invention only needs to add a lower dose to the epoxy resin material to have a good flame retardant effect, and can greatly inhibit the generation of smoke. Moreover, the yield of the DOPO-PDCAM flame retardant prepared by the preparation method of the present invention is relatively high, which can meet the requirements of industrial production. Description of the Drawings

[0017] Figure 1 is the 13 C spectrum of the DOPO-PDCAM flame retardant of the present invention;

[0018] Figure 2 is the infrared spectrum of the DOPO-PDCAM flame retardant of the present invention;

[0019] Figure 3 is the thermogravimetric analysis diagram of the composite material added with DOPO-PDCAM flame retardant with different mass fractions. Detailed Embodiments

[0020] For the convenience of those skilled in the art, the present invention will be further described below in conjunction with embodiments and the accompanying drawings. The content mentioned in the embodiments does not limit the present invention.

[0021] A DOPO-PDCAM flame retardant has the following structural formula:

[0022]

[0023] The preparation method of the DOPO-PDCAM flame retardant is as follows:

[0024] I. Prepare the intermediate PDCAM according to the following route:

[0025]

[0026] Weigh 2.84 g (0.04 mol) of acrylamide into a beaker, add 30 mL of acetonitrile to dissolve it, then transfer the dissolved acrylamide solution to a three-necked flask. Then, add 5 mL of triethylamine to the three-necked flask. Measure 3 mL (0.02 mol) of phenyl dichlorophosphate, dissolve it in 20 mL of acetonitrile, and transfer it to a constant pressure dropping funnel. Stir magnetically at 5 °C and slowly add the phenyl dichlorophosphate solution dropwise, and let the entire reaction device react at 5 °C for two hours. After two hours, raise the temperature to 65 °C and react for 10 h, then stop the reaction to obtain a light yellow solution. Let the reaction solution stand and cool, and colorless and transparent needle-like crystals precipitate out. After suction filtration, wash the filter cake three times with acetonitrile. Finally, weigh the obtained transparent crystals, and the weight is 4.65 g, and the yield is 82.4%.

[0027] II. Prepare the DOPO-PDCAM flame retardant according to the following route:

[0028]

[0029] Weigh 1.96 g (about 7 mmol) of PDCAM into a three-necked flask, add 20 mL of tetrahydrofuran to the three-necked flask as the reaction solvent, heat and raise the temperature of the magnetic stirring water bath to 65 °C to make PDCAM evenly dispersed in the tetrahydrofuran solution. Then, weigh 3.24 g (about 15 mmol) of DOPO with a weighing paper, dissolve it in 40 mL of tetrahydrofuran solution, and transfer it to the three-necked flask. Carry out reflux condensation for 12 h to obtain a milky white solution. Stop the reaction and let it stand for precipitation. At this time, white precipitate appears at the bottom of the beaker. Then, filter and wash the precipitate, and put the filter cake into a drying oven at 45 °C and dry it for 4 h to obtain 4.46 g of a white product, and the yield is 89.24%. This yield is close to 90%, which is very high for industrial production and is an ideal flame retardant product suitable for industrial production.

[0030] Figure 2 It is the infrared spectrum diagram of PDCAM / DOPO, 3445.98 cm-1 is the absorption peak of the nitrogen-hydrogen (N-H) stretching vibration in -PONH-, 1170.84 cm -1 is the absorption peak of the III band of -PONH-, 500 - 550 cm -1 There is no absorption peak of the phosphorus-chlorine bond (P-Cl) stretching vibration. The results show that the formation of -PONH- and the disappearance of the original P-Cl in the product prove that acrylamide and phenyl dichlorophosphate have successfully reacted. Figure 2 In, the P-H absorption peak of DOPO and the characteristic absorption peak of the C=C bond in acrylamide do not exist in PDCAM / DOPO, indicating that the P-H bond of DOPO and the C=C double bond of acrylamide have undergone an addition reaction, suggesting that PDCAM has successfully reacted with DOPO to form the PDCAM / DOPO flame retardant.

[0031] Flame Retardant Modification of Epoxy Resin by DOPO-PACAM

[0032] By using an oxygen index tester and a horizontal and vertical burning tester, the oxygen index and UL-94 ratings of the splines with 1%, 3%, 5%, and 7% flame retardant contents were obtained respectively, and then the flame retardant properties of the flame retardant were analyzed. The results are as follows.

[0033] (1) Oxygen Index Test

[0034] Table 1 Influence of Flame Retardant Content on Oxygen Index

[0035]

[0036] As can be seen from Table 1, when the mass fraction of the flame retardant is 1%, the LOI of the epoxy resin composite is 31.2%. When the mass fraction of the flame retardant is 3%, the LOI of the epoxy resin composite is 32.7%. When the mass fraction of the flame retardant is 5%, the LOI of the epoxy resin composite is 32.0%. When the mass fraction of the flame retardant is 7%, the LOI of the epoxy resin composite is 32.2%. The test results show that adding a flame retardant to the epoxy resin can increase its limiting oxygen index, but when the dosage of the flame retardant exceeds 3%wt, the oxygen index decreases to a certain extent. When the mass fraction of the flame retardant is 3%wt, the flame retardant effect is the best.

[0037] (2) Vertical Burning Index Test

[0038] Table 2 Influence of Flame Retardant Content on UL-94 Rating

[0039]

[0040] The epoxy resin blank sample belongs to flammable substances and shows a dripping phenomenon during the vertical burning test. As can be seen from Table 2, after adding different contents of DOPO-PACAM flame retardant to the EP material, the EP composite material has a certain degree of flame retardant effect, but the dripping phenomenon during combustion is still inevitable. As can be seen from Table 2, for the 3% EP composite material, T1 = 22s, T2 = 16s, T1+T2 = 38s, and dripping substances are produced. The vertical burning of the EP composite material with a flame retardant mass fraction of 3% can reach the V-2 level. The research results show that adding this DOPO-PDCAM flame retardant to EP can improve the vertical burning performance of the material when the addition amount of the flame retardant is 3%.

[0041] (3) Smoke suppression effect of the flame retardant

[0042] The epoxy resin blank sample is a substance prone to smoke generation during combustion, and obvious black smoke emerges during the limiting oxygen index test and horizontal and vertical burning. As is well known, the smoke generation amount of materials is crucial for the flame retardant performance of materials. After adding DOPO-PACAM flame retardant, during the LOI and UL-94 test experiments, a significant smoke suppression effect is found. After burning 6 oxygen index specimens, there are still no obvious black smoke stains around the glass cover of the oxygen index instrument, showing a better smoke suppression effect compared to the blank sample. Moreover, the smoke suppression effect increases with the increase in the addition amount of the flame retardant, and the effect is best when the dosage is 7%wt.

[0043] (4) Influence of the dosage of the flame retardant on the thermal stability of modified EP

[0044] The heating range of the thermogravimetric analyzer is 30 - 900 °C, and the programmed heating rate is 20.0 (K / min), carried out in an air atmosphere. The initial mass of the powder sample of the EP flame retardant composite material with a flame retardant mass fraction of 1% is 3.74 mg, the initial mass of the powder sample of the EP flame retardant composite material with a flame retardant mass fraction of 3% is 5.47 mg, the mass of the powder sample of the EP flame retardant composite material with a flame retardant mass fraction of 5% is 4.90 mg, and the mass of the powder sample of the EP flame retardant composite material with a flame retardant mass fraction of 7% is 6.37 mg. As Figure 3 can be seen, the modified material starts to lose weight from 80 °C, probably due to the presence of moisture in the system, which is vaporized at 80 °C. The material undergoes two weight losses. The first weight loss occurs at around 300 °C, and the second weight loss occurs at around 500 °C. When the temperature rises to around 300 °C, the composite material begins to decompose thermally. The EP composite material with a flame retardant mass fraction of 1% shows complete weight loss in an inert atmosphere with no residual mass. The EP composite material with a flame retardant mass fraction of 3wt% shows complete weight loss in an air atmosphere with no residual mass. The EP composite material with a flame retardant mass fraction of 5wt% shows complete weight loss in an air atmosphere with no residual mass. The 7% EP composite material has a residual mass of 0.44% in an inert atmosphere.

[0045] It can be seen from the experimental image analysis that when the mass fraction of the flame retardant is 7 wt%, the thermal stability of the composite material reaches the peak value from 450 °C to 900 °C.

[0046] The DOPO-PDCAM flame retardant provided by the above-mentioned embodiment provides phosphorus element by phenyl dichlorophosphate and nitrogen element by acrylamide to synthesize a phosphorus-nitrogen-based flame retardant intermediate. At the same time, it is combined with DOPO with excellent flame retardant performance to prepare and synthesize a new type of environmentally friendly and excellent flame retardant phosphorus-nitrogen-based intumescent flame retardant, and its flame retardant effect in epoxy resin is also relatively ideal. Especially in terms of smoke suppression, it has achieved better results than the prior art. In addition, a major highlight of the present invention also lies in making further deepening of the reaction between phosphoryl chloride and acrylamide by using the characteristic that DOPO has a high reactivity with olefins, making it a new type of phosphorus-nitrogen-based flame retardant.

[0047] In order to enable those of ordinary skill in the art to more conveniently understand the improvements of the present invention over the prior art, some drawings and descriptions of the present invention have been simplified, and the above-mentioned embodiments are the preferred implementation schemes of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious replacement without departing from the concept of the technical solution of the present invention is within the protection scope of the present invention.

Claims

1. A DOPO-PDCAM flame retardant, characterized in that, The structural formula is as follows:

2. The preparation method of the DOPO-PDCAM flame retardant according to claim 1, characterized in that, It includes the following steps:

1. Prepare the intermediate PDCAM according to the following route:

2. Prepare the DOPO-PDCAM flame retardant according to the following route:

3. The preparation method of the DOPO-PDCAM flame retardant according to claim 2, wherein: In step 1, weigh an appropriate amount of acrylamide in a beaker, add acetonitrile to dissolve it, then transfer the dissolved acrylamide solution to a three-necked flask. Then, add an appropriate amount of triethylamine to the three-necked flask. Weigh an appropriate amount of phenyl dichlorophosphate, dissolve it in acetonitrile and transfer it to a constant pressure dropping funnel. Stir magnetically at 5 °C and slowly add the phenyl dichlorophosphate solution dropwise, and let the entire reaction device react at 5 °C for two hours. After two hours, raise the temperature to 65 °C and react for 10 h, then stop the reaction to obtain a light yellow solution. Let the reaction solution stand and cool, and colorless transparent needle-like crystals will precipitate. After suction filtration, wash the filter cake three times with acetonitrile, and finally obtain a transparent crystal-like intermediate PDCAM.

4. The preparation method of the DOPO-PDCAM flame retardant according to claim 2, wherein: In step 2, weigh an appropriate amount of PDCAM in a three-necked flask, add tetrahydrofuran as the reaction solvent to the three-necked flask, heat the magnetic stirring water bath to 65 °C to uniformly disperse PDCAM in the tetrahydrofuran solution. Then, weigh an appropriate amount of DOPO with a weighing paper, dissolve it in the tetrahydrofuran solution and transfer it to the three-necked flask, and carry out reflux condensation for 12 h to obtain a milky white solution. Stop the reaction and let it stand for precipitation. At this time, white precipitate appears at the bottom of the beaker. After suction filtration and washing of the precipitate, put the filter cake into a drying oven at 45 °C and dry it for 4 h to obtain a white product of DOPO-PDCAM flame retardant.

5. Modified epoxy resin, characterized in that: It contains the DOPO-PDCAM flame retardant described in claim 1.

6. The modified epoxy resin according to claim 5, wherein: The mass content of the added DOPO-PDCAM flame retardant is 1% - 7%.

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