Dopo phosphorus boron durable flame retardant and preparation method thereof

Abstract

The application belongs to the technical field of flame retardant synthesis, and particularly relates to a DOPO phosphorus-boron durable flame retardant and a preparation method thereof. The DOPO and alkenyl phenol are dissolved in anhydrous ethanol, heated and stirred in a protective atmosphere until a light yellow precipitate is generated; when the precipitate is no longer continuously generated, the solid intermediate is obtained by pouring, filtering, washing, purifying and drying; boric acid is added into a three-necked flask containing the solvent and the solid intermediate, high-temperature heating is performed to promote etherification and dehydration of the reaction system; when no water vapor is generated in the system, the target flame retardant is obtained by drying the substances in the flask. The target flame retardant contains alkenyl phenol, DOPO and boric acid structures in the molecule, solid-phase catalytic charring, and gas-phase free radical quenching to reduce heat release, so that the flame retardance of fibers can be effectively improved. The preparation method is simple, the conditions are easy to realize, the solvent can be recycled and reused, environmental pollution is reduced, and the cost is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of flame retardant synthesis, and particularly relates to a DOPO phosphorus-boron durable flame retardant and a preparation method thereof. BACKGROUND

[0002] Cotton fabric occupies an important part in our daily life and production field due to its excellent physical performance and low production cost, and with the development of economy, the development space of cotton fabric is further expanded, and has a broad development prospect. However, its natural flammability still has potential threats and negative effects on people's life and property. Therefore, it is particularly important to perform flame-retardant functional treatment on cotton fabric.

[0003] At present, more halogen flame retardants are added in the actual application of flame retardants, and this type of flame retardant has high flame-retardant efficiency and good heat resistance, but a large amount of polluting halogen-containing products are generated in the gas phase flame-retardant process. Although the flame-retardant treatment of the material is achieved, the polluting products have strong negative effects on the environment and people's health. Therefore, it is extremely urgent to develop a new type of green halogen-free flame retardant.

[0004] Using alkenyl phenol (such as eugenol) as a flame retardant synthesis raw material is one of the effective ways to realize the environmental protection of flame retardant synthesis. The rich active group types of alkenyl phenol can react with various flame-retardant compounds to achieve the collocation of different structures, and then realize the regulation of different effects. For example, DOPO can adduct with C=C in alkenyl phenol, and boric acid can be etherified and dehydrated with phenolic hydroxyl groups in the presence of a dehydrating agent. 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is a high-efficiency phosphorus-containing flame retardant, which is often applied to polymer flame-retardant modification and is one of the effective substitutes for halogen flame retardants. The degradation products of DOPO in a high-temperature environment can terminate the chain reaction in the air through quenching. Boric acid is a common environmentally friendly flame retardant, which has excellent catalytic carbonization ability and can increase the thickness of the protective carbon layer on the fiber surface and strengthen the protection of the elastic layer. The structure of alkenyl phenol, DOPO and boric acid is complementary, which can effectively realize the efficient flame retardation of cotton fabric, but such research is still rare. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a DOPO phosphorus-boron durable flame retardant and a preparation method thereof. Alkenyl phenol is used as a carbon source and a medium to realize the combination of DOPO and boric acid with bio-based substances, solid-phase catalytic carbonization, and gas-phase free-radical quenching to reduce heat release. The flame resistance and heat release inhibition capacity of the cotton fabric treated by the flame retardant are greatly enhanced.

[0006] The technical scheme adopted is:

[0007] A DOPO phosphorus boron durable flame retardant, the chemical structure of which is as follows:

[0008]

[0009] In the formula, R1 is hydrogen, methyl, ethyl, methoxy, ethoxy, trifluoromethyl, hydroxyl.

[0010] A preparation method of a DOPO phosphorus boron durable flame retardant, comprising the following synthesis steps:

[0011] (1) adding DOPO and alkenyl phenol into anhydrous ethanol, and then stirring until the mixture becomes a uniform solution;

[0012] (2) transferring the mixed solution in step (1) into a reaction device, introducing a protective gas until the air in the device is completely excluded, heating the reaction system and stirring to make the reaction system generate a light yellow precipitate; when the precipitate no longer continues to generate, the mixture is poured out, filtered, washed, purified, dried, and then a light yellow powder-shaped solid intermediate is obtained;

[0013] (3) adding boric acid into a three-necked flask containing the solvent and the solid intermediate, mixing, heating and stirring until no liquid drops are evaporated in the reaction device;

[0014] (4) transferring the product in the flask into an oven and drying to a constant weight, and then the target flame retardant is obtained.

[0015] The reaction device used in the application, such as a three-necked flask, is connected with a gas inlet pipe, a reflux condensing device, a stirrer and a thermometer.

[0016] Preferably, step (1) is operated at room temperature, and the molar ratio of DOPO to alkenyl phenol is 4-1:1.

[0017] Preferably, in step (1), the mass ratio of the total mass of DOPO and alkenyl phenol to the mass of anhydrous ethanol is 1:5-15.

[0018] Preferably, in step (1), the alkenyl phenol is any one of eugenol, 3-allyl phenol, 2-allyl phenol, 4-allyl phenol, 2-vinyl phenol, 3-vinyl phenol, 4-vinyl phenol and 4-vinyl-3-methyl phenol.

[0019] Preferably, the protective gas in step (2) is nitrogen or high-purity argon.

[0020] Preferably, in step (2), the heating temperature is 50-200℃, the stirring time is 1-20h, and the reaction temperature is kept at 50-200℃.

[0021] Preferably, in the step (2), the solvent used for washing is anhydrous ethanol or anhydrous methanol, and the washing is repeated for 3-5 times.

[0022] Preferably, in the step (3), the molar ratio of boric acid to the solid intermediate is 1:1-2, and the temperature for heating reaction is 85-120℃.

[0023] Preferably, in the step (3), the solvent used is toluene, and the mass ratio of toluene to boric acid is 10-3:1.

[0024] Preferably, in the step (4), the drying temperature is 40-60℃, and the drying time is 12h or more.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] The DOPO phosphorus-boron durable flame retardant of the present application uses alkenyl phenol as a carbon source and a medium, realizes the combination of DOPO and boric acid with bio-based substances, and realizes solid-phase catalytic carbonization and gas-phase free radical quenching to reduce heat release. The flame resistance and heat release capacity of the cotton fabric treated with the flame retardant are greatly enhanced.

[0027] The preparation method of the present application is simple, the conditions are easy to realize, the solvent toluene used can be recycled and reused, environmental pollution is reduced, and the cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The figure is the change curve of the total heat release (a figure) and the heat release rate (b figure) of the cotton fabric and pure cotton treated with the bio-based halogen-free flame retardant synthesized in Example 1 with time;

[0029] Figure 2 The figure is the real-time acquisition comparison chart of the vertical flammability test of the cotton fabric treated with the bio-based halogen-free flame retardant synthesized in Example 1 and the pure cotton fabric; wherein a1 is the combustion test chart of the pure cotton fabric, a2 is the combustion test chart of the fabric treated with the flame retardant with a weight gain of 5%, a3 is the combustion test chart of the fabric treated with the flame retardant with a weight gain of 10%, and a4 is the combustion test chart of the fabric treated with the flame retardant with a weight gain of 15%. DETAILED DESCRIPTION

[0030] The drawings are only used for illustrative description; it should be understood that the well-known common knowledge or prior art in the examples can be omitted; the cases mentioned below are only used to explain the present application, and are used to facilitate the description of the present application and simplify the description, and therefore, cannot be understood as a limitation on the present application.

[0031] The present application will be described in detail below in combination with examples.

[0032] Example 1

[0033] At 25°C, 0.04 mol DOPO and 0.02 mol eugenol were added to 60 mL of anhydrous ethanol and stirred until the liquid was homogeneous and transparent. Then the mixture was transferred to a three-necked flask and nitrogen gas was introduced for 5 minutes. The gas vent and outlet were then sealed, and the temperature of the reaction system was raised to 70°C. The mixture was stirred continuously for 3 hours until no more pale yellow precipitate was produced in the solution.

[0034] The mixture was poured out and filtered. The filtered product was washed three times with anhydrous ethanol, then transferred to a forced-air drying oven and dried at 60°C for 12 hours to obtain a solid intermediate. The solid intermediate was then mixed with 5 g of toluene and 1.2 g of boric acid and stirred at 120°C for 1 hour. The product in the bottle was transferred to a forced-air drying oven and dried to constant weight to obtain 8.33 g of the target flame retardant with a eugenol conversion rate of 98%.

[0035] Figure 1 The display shows the heat release of pure cotton and cotton fabrics treated with flame retardants. First Figure 1 In Figure a, the total heat release (THR) of pure cotton was 10.1 MJ / m², while the total heat release of the samples treated with flame retardants all decreased to varying degrees: the THRs of samples with weight gains of 5%, 10%, and 15% were 9.3, 8.9, and 4.6 MJ / m², respectively. 2 Compared to pure cotton, the percentages decreased by 8%, 12%, and 55% respectively, indicating that flame retardants have a significant inhibitory effect on the heat release behavior of cotton fabrics. Furthermore, Figure 1 Similarly, in Figure b, the maximum heat release rate (HRR) of pure cotton is 344.3 KW / m². 2 The HRRs for samples with weight gains of 5%, 10%, and 15% were 165.8, 100.6, and 30.3 KW / m, respectively. 2 The HRR of these materials was only 48.2%, 29.2%, and 8.8% of that of pure cotton, respectively, which demonstrates that the flame retardant effectively mitigated heat release behavior and reduced the heat release rate of cotton fabrics.

[0036] like Figure 2As shown, al is a series of images taken at 0s, 5s, 10s, 15s, 20s, 25s, 30s of vertical flammability test of pure cotton fabric, a2 exhibits a series of images taken at 0s, 5s, 10s, 15s, 20s, 25s, 30s of the sample with 5% retardant weight gain, a3 exhibits a series of images taken at 0s, 5s, 10s, 15s, 20s, 25s, 30s of the sample with 10% retardant weight gain, and a4 exhibits a series of images taken at 0s, 5s, 10s, 15s, 20s, 25s, 30s of the sample with 15% retardant weight gain. It is obvious that the pure cotton burns rapidly as soon as it is ignited, and the flame spreads rapidly, while the sample of cotton fabric with 10% weight gain of the retardant has a slow flame spread and is not burned through, which demonstrates the effectiveness of the retardant treatment. The damaged part remains a large amount of char, and the length of the char decreases with the increase of the weight gain of the retardant, which demonstrates the good protection of the retardant to the cotton fabric.

[0037] Example 2

[0038] At 25°C, 0.1 mol DOPO and 0.025 mol 4-allylphenol were added into 60 mL anhydrous ethanol, stirred until the liquid was uniform and transparent, then added into a three-necked flask, argon was introduced for 5 minutes, then the gas inlet tube and gas outlet were closed, the temperature of the reaction system was raised to 65°C, and stirred for 2.5 h until no more yellowish precipitate was produced in the solution.

[0039] The mixture was poured out and filtered, the product obtained by filtration was washed with anhydrous methanol for three times, then transferred into a vacuum drying oven, dried at 60°C for 12 h to obtain a solid intermediate. The solid intermediate was then mixed with 6.5 g of toluene and 1.5 g of boric acid, stirred at 105°C for 1.5 h, and the product in the bottle was transferred to a forced air drying oven to dry to constant weight, to obtain the target retardant 9.3 g, with a 4-allylphenol conversion rate of 95%.

[0040] Example 3

[0041] At 25°C, 0.06 mol DOPO and 0.025 mol 3-allylphenol were added into 60 mL anhydrous ethanol, stirred until the liquid was uniform and transparent, then added into a three-necked flask, argon was introduced for 5 minutes, then the gas inlet tube and gas outlet were closed, the temperature of the reaction system was raised to 60°C, and stirred for 2.5 h until no more yellowish precipitate was produced in the solution.

[0042] The mixture was poured into a filter funnel and the product was washed with anhydrous methanol three times and then transferred to a vacuum oven and dried at 60°C for 12 h to obtain a solid intermediate. The solid intermediate was then mixed with 6.0 g of toluene and 1.5 g of boric acid and stirred at 105°C for 1.5 h. The product in the flask was transferred to a forced air oven and dried to constant weight to obtain the target flame retardant 9.1 g with a 3-allylphenol conversion of 92%.

[0043] Example 4

[0044] At 25°C, 0.3 mol of DOPO and 0.1 mol of 2-allylphenol were added to 60 mL of anhydrous ethanol and stirred until the liquid was uniformly transparent. The mixture was then added to a three-necked flask, argon was bubbled for 5 min, and then the gas inlet tube and outlet were closed. The temperature of the reaction system was raised to 55°C, and stirring was continued for 3 h until no more yellowish precipitate was produced in the solution.

[0045] The mixture was poured into a filter funnel and the product was washed with anhydrous methanol three times and then transferred to a vacuum oven and dried at 60°C for 16 h to obtain a solid intermediate. The solid intermediate was then mixed with 17.6 g of toluene and 6.0 g of boric acid and stirred at 110°C for 1 h. The product in the flask was transferred to a forced air oven and dried to constant weight to obtain the target flame retardant 37.8 g with a 2-allylphenol conversion of 96%.

[0046] Example 5

[0047] At 25°C, 0.28 mol of DOPO and 0.08 mol of 2-vinylphenol were added to 60 mL of anhydrous ethanol and stirred until the liquid was uniformly transparent. The mixture was then added to a three-necked flask, argon was bubbled for 5 min, and then the gas inlet tube and outlet were closed. The temperature of the reaction system was raised to 70°C, and stirring was continued for 2.5 h until no more yellowish precipitate was produced in the solution.

[0048] The mixture was poured into a filter funnel and the product was washed with anhydrous ethanol three times and then transferred to a vacuum oven and dried at 60°C for 15 h to obtain a solid intermediate. The solid intermediate was then mixed with 12.8 g of toluene and 4.94 g of boric acid and stirred at 115°C for 1 h. The product in the flask was transferred to a forced air oven and dried to constant weight to obtain the target flame retardant 28.9 g with a 2-vinylphenol conversion of 95%.

[0049] Example 6

[0050] At 25°C, 0.28 mol of DOPO and 0.08 mol of 3-vinylphenol were added to 60 mL of anhydrous ethanol and stirred until the liquid was uniformly transparent. The mixture was then added to a three-necked flask, argon was bubbled for 5 min, and then the gas inlet tube and outlet were closed. The temperature of the reaction system was raised to 70°C, and stirring was continued for 2.5 h until no more yellowish precipitate was produced in the solution.

[0051] The mixture was poured into a filter funnel and the product was washed with absolute ethanol three times. The product was then transferred to a vacuum oven and dried at 60°C for 15 hours to give a solid intermediate. The solid intermediate was then mixed with 12.8 g of toluene and 4.94 g of phosphoric acid and stirred at 115°C for 1 hour. The product in the flask was then transferred to a forced air oven and dried to constant weight to give the target flame retardant 27.6 g with a 4-vinylphenol conversion of 91%.

[0052] Example 7

[0053] At 25°C, 0.28 mol of DOPO and 0.08 mol of 4-vinylphenol were added to 60 mL of absolute ethanol and stirred until the liquid was uniformly transparent. The mixture was then added to a three-necked flask, argon was bubbled through for 5 minutes, and then the gas inlet tube and outlet were closed. The temperature of the reaction system was raised to 70°C and stirring was continued for 2.5 hours until no more yellowish precipitate was produced in the solution.

[0054] The mixture was poured into a filter funnel and the product was washed with absolute ethanol three times. The product was then transferred to a vacuum oven and dried at 60°C for 15 hours to give a solid intermediate. The solid intermediate was then mixed with 12.8 g of toluene and 4.94 g of phosphoric acid and stirred at 115°C for 1 hour. The product in the flask was then transferred to a forced air oven and dried to constant weight to give the target flame retardant 27.6 g with a 4-vinylphenol conversion of 91%.

[0055] Example 8

[0056] At 25°C, 0.28 mol of DOPO and 0.08 mol of 4-vinylphenol were added to 60 mL of absolute ethanol and stirred until the liquid was uniformly transparent. The mixture was then added to a three-necked flask, argon was bubbled through for 5 minutes, and then the gas inlet tube and outlet were closed. The temperature of the reaction system was raised to 70°C and stirring was continued for 2.5 hours until no more yellowish precipitate was produced in the solution.

[0057] The mixture was poured into a filter funnel and the product was washed with absolute ethanol three times. The product was then transferred to a vacuum oven and dried at 60°C for 15 hours to give a solid intermediate. The solid intermediate was then mixed with 12.8 g of toluene and 4.94 g of phosphoric acid and stirred at 115°C for 1 hour. The product in the flask was then transferred to a forced air oven and dried to constant weight to give the target flame retardant 27.6 g with a 4-vinylphenol conversion of 91%.

[0058] The reaction apparatus in each stage of each example is a conventional reactor apparatus in actual operation, such as a three-necked flask, and thus is not described in detail.

[0059] Of course, the above description is not a limitation of the present application, and the present application is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the spirit and scope of the present application should also be included in the protection scope of the present application.

Claims

1. A DOPO phosphorus boron durable flame retardant characterized by, The chemical structure of the DOPO phosphorus boron durable flame retardant is as follows: In the formula, R1 is hydrogen, methyl, ethyl, methoxy, ethoxy, trifluoromethyl, hydroxyl.

2. A process for the preparation of DOPO phosphorus boron durable flame retardant as claimed in claim 1, wherein, The synthesis steps include: (1) adding DOPO and alkenyl phenol into anhydrous ethanol, and then stirring until the mixture becomes a uniform solution; (2) transferring the mixed solution in step (1) into a reaction device, introducing a protective gas until the air in the device is completely excluded, heating the reaction system and stirring to make the reaction system generate a light yellow precipitate; when the precipitate no longer continues to generate, the mixture is poured out, filtered, washed, purified, dried, and then a light yellow powder-shaped solid intermediate is obtained; (3) adding boric acid into a three-neck flask containing the solvent and the solid intermediate, mixing, heating and stirring until no liquid drops are evaporated in the reaction device; (4) transferring the product in the flask into an oven and drying to a constant weight, and then the target flame retardant is obtained.

3. The method for preparing DOPO phosphorus-boron durable flame retardant according to claim 2, characterized in that, The step (1) is operated at room temperature, the molar ratio of DOPO to alkenyl phenol is 4-1:1, and the total mass ratio of DOPO and alkenyl phenol to the mass of anhydrous ethanol is 1:5-15.

4. The method for preparing DOPO phosphorus-boron durable flame retardant according to claim 2, characterized in that, In the step (1), the alkenyl phenol is any one of eugenol, 3-allyl phenol, 2-allyl phenol, 4-allyl phenol, 2-vinyl phenol, 3-vinyl phenol, 4-vinyl phenol, and 4-vinyl-3-methyl phenol.

5. The preparation method of a DOPO phosphorus boron durable flame retardant according to claim 2, characterized in that, The protective gas in the step (2) is nitrogen or high-purity argon.

6. The method for preparing DOPO phosphorus-boron durable flame retardant according to claim 2, characterized in that, In the step (2), the heating temperature is 50-200°C, the stirring time is 1-20h, and the reaction temperature is kept at 50-200°C.

7. The method for preparing a DOPO phosphorus boron durable flame retardant according to claim 2, characterized in that, In the step (2), the solvent used for washing is anhydrous ethanol or anhydrous methanol, and the washing is repeated for 3-5 times.

8. The method for preparing a DOPO phosphorus-boron durable flame retardant according to claim 2, characterized in that, In the step (3), the molar ratio of boric acid to the solid intermediate is 1:1-2, and the heating reaction temperature is 85-120°C.

9. The preparation method of a DOPO phosphorus boron durable flame retardant according to claim 2, characterized in that, In the step (3), the solvent used is toluene, and the mass ratio of toluene to boric acid is 10-3:

1.

10. A process for the preparation of DOPO phosphorus boron durable flame retardant according to claim 2, characterized by, In the step (4), the drying temperature is 40-60°C, and the drying time is more than 12h.

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