A boron-phosphorus-nitrogen synergistic smoke-suppressing flame retardant and a preparation method thereof

Abstract

The application belongs to the technical field of flame retardant preparation, and particularly relates to a boron-phosphorus-nitrogen synergistic smoke suppression flame retardant and a preparation method thereof. The flame retardant uses pentaerythritol, boric acid, an aqueous solution of aminotri-methylene phosphoric acid and urea as raw materials, and provides a boron-phosphorus-nitrogen synergistic flame retardant. The flame retardant molecule contains various flame-retardant elements, can play a synergistic flame-retardant role, and can obtain higher flame-retardant performance. On the one hand, the flame retardant can be connected to the cotton fabric through a chemical bond, so that the flame-retardant cotton fabric has certain washing resistance. On the other hand, the flame-retardant effect is improved, and the mechanical properties of the fabric are also enhanced. The tensile strength of the cotton fabric treated by the flame retardant is higher than that of pure cotton fabric, and the breaking elongation is also improved. The highest breaking elongation is increased by about 12.9%. The preparation method has the advantages of simple synthesis process, no toxic gas release, high product purity, no harm to the environment and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of flame retardant preparation, and particularly relates to a boron-phosphorus-nitrogen synergistic smoke suppression flame retardant and a preparation method thereof. BACKGROUND

[0002] Cotton fabric woven from cotton fibers has excellent moisture absorption and air permeability, warmth retention, softness and biocompatibility, and is widely used in the fields of medicine, military, construction and daily life. However, cotton fabric has the defect of flammability and is very easy to be ignited. In recent years, the fire caused by cotton fabric is increasing, which brings great hidden danger to people's life and property safety. Therefore, more and more researchers pay attention to endowing cotton fabric with flame retardant properties.

[0003] Now there are various series of flame retardants, such as halogen-based, phosphorus-based, nitrogen-based and boron-based flame retardants. Halogen-based flame retardants are a kind of flame retardants in which halogen atoms play a major role in flame retardation. They have the characteristics of low addition amount, good stability, affordable price and good compatibility with resin materials, and have been widely used in the early stage of the development of flame retardants. Although halogen-based flame retardants have many advantages, due to their special chemical properties, their shortcomings cannot be ignored. They release dense smoke and hydrogen halide gas at high temperature and in the presence of open flame. Nitrogen-based flame retardants have poor flame retardant effect, but can produce non-combustible gas during combustion, which plays a role in gas phase flame retardation. Therefore, nitrogen-based flame retardants are usually used in combination with other flame-retardant elements to achieve synergistic flame retardation effect, which can significantly enhance the flame retardant performance of the flame retardant. Boron-based flame retardants have the effect of inhibiting smoke, but have poor flame retardancy. Phosphorus-based flame retardants have excellent flame retardancy, but also have shortcomings. Therefore, there is an urgent need for a synergistic flame retardant to make the flame retardant more excellent. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a boron-phosphorus-nitrogen synergistic smoke suppression flame retardant and a preparation method thereof. On the basis of boron spiro ring, groups containing phosphorus elements and nitrogen elements are grafted respectively, and the synthesized flame retardant can not only improve the flame retardant performance of cotton fabric, but also improve the physical properties of cotton fabric, and is green and pollution-free with high product purity.

[0005] A boron-phosphorus-nitrogen efficient synergistic flame retardant, the structural formula of the flame retardant is:

[0006]

[0007] A preparation method of a boron-phosphorus-nitrogen efficient synergistic flame retardant, comprising the following steps:

[0008] (1) mixing pentaerythritol and boric acid for reaction, and after the reaction is completed, recrystallization is performed to synthesize intermediate product I for later use; wherein the structural formula of the intermediate product I is:

[0009]

[0010] (2) adding the intermediate product I and the aqueous solution of aminotrimethylenephosphonic acid into a reaction device, heating and stirring until dissolved, reacting, and distilling water vapor until none is distilled out; after cooling, taking out the reaction product, drying in an oven until constant weight, and obtaining a transparent viscous liquid, which is the intermediate product II; the structural formula of the intermediate product II is as follows:

[0011]

[0012] (3) adding urea and the intermediate product II into a reaction container, and adding a solvent, heating and stirring until dissolved;

[0013] (4) after cooling, removing the excess solvent of the product obtained in step (3) through a rotary evaporator, and finally drying to constant weight, and finally obtaining a light yellow oily liquid, which is the final product, i.e., the target flame retardant.

[0014] Preferably, in step (1), the molar ratio of pentaerythritol and boric acid is 1:2-7.

[0015] Preferably, in step (1), the reagent used for recrystallization is any one of acetone or acetonitrile.

[0016] Preferably, in step (2), the molar ratio of the intermediate product I and the aqueous solution of aminotrimethylenephosphonic acid is 1:2-5.

[0017] Preferably, in step (2), the heating temperature of the reaction is 110-130℃; and after cooling, the temperature is 40-60℃.

[0018] Preferably, in step (3), the molar ratio of the intermediate product II and urea is 1:2-5.

[0019] Preferably, in step (3), the solvent used is any one of toluene, ethylbenzene or a mixture of any proportion thereof.

[0020] Preferably, in step (3), the heating temperature is 150-160℃, and the reaction time is 1-5h.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] The application provides a boron-phosphorus-nitrogen synergistic flame retardant, which contains various flame-retardant elements in the flame retardant molecules, can play a synergistic flame-retardant effect, and obtains higher flame-retardant performance. On one hand, the flame retardant can be connected with the cotton fabric through a chemical bond, so that the flame-retadant cotton fabric obtains certain washing resistance, on the other hand, the flame-retardant effect is improved, when the weight gain rate reaches 20.4%, the LOI value of the treated fabric reaches 44.7%, the mechanical properties of the fabric are also enhanced, the tensile strength of the cotton fabric treated by the flame retardant is all higher than that of the pure cotton fabric, and the breaking elongation is also improved, and the highest breaking elongation is increased by about 12.9%.

[0023] The preparation method provided by the application has the advantages of simple synthesis process, no release of toxic gas, high product purity, no harm to the environment and the like. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The application provides a synthesis route of the flame retardant.

[0025] Figure 2 The application provides a boron-phosphorus-nitrogen synergistic flame retardant, which contains various flame-retardant elements in the flame retardant molecules, can play a synergistic flame-retardant effect, and obtains higher flame-retardant performance. On one hand, the flame retardant can be connected with the cotton fabric through a chemical bond, so that the flame-retadant cotton fabric obtains certain washing resistance, on the other hand, the flame-retardant effect is improved, when the weight gain rate reaches 20.4%, the LOI value of the treated fabric reaches 44.7%, the mechanical properties of the fabric are also enhanced, the tensile strength of the cotton fabric treated by the flame retardant is all higher than that of the pure cotton fabric, and the breaking elongation is also improved, and the highest breaking elongation is increased by about 12.9%.

[0026] Figure 3 The application provides a boron-phosphorus-nitrogen synergistic flame retardant, which contains various flame-retardant elements in the flame retardant molecules, can play a synergistic flame-retardant effect, and obtains higher flame-retardant performance. On one hand, the flame retardant can be connected with the cotton fabric through a chemical bond, so that the flame-retadant cotton fabric obtains certain washing resistance, on the other hand, the flame-retardant effect is improved, when the weight gain rate reaches 20.4%, the LOI value of the treated fabric reaches 44.7%, the mechanical properties of the fabric are also enhanced, the tensile strength of the cotton fabric treated by the flame retardant is all higher than that of the pure cotton fabric, and the breaking elongation is also improved, and the highest breaking elongation is increased by about 12.9%.

[0027] Figure 4 The application provides a boron-phosphorus-nitrogen synergistic flame retardant, which contains various flame-retardant elements in the flame retardant molecules, can play a synergistic flame-retardant effect, and obtains higher flame-retardant performance. On one hand, the flame retardant can be connected with the cotton fabric through a chemical bond, so that the flame-retadant cotton fabric obtains certain washing resistance, on the other hand, the flame-retardant effect is improved, when the weight gain rate reaches 20.4%, the LOI value of the treated fabric reaches 44.7%, the mechanical properties of the fabric are also enhanced, the tensile strength of the cotton fabric treated by the flame retardant is all higher than that of the pure cotton fabric, and the breaking elongation is also improved, and the highest breaking elongation is increased by about 12.9%. DETAILED DESCRIPTION

[0028] The accompanying drawings are only used for illustrative purposes; it should be understood that the well-known common knowledge or prior art in the embodiments can be omitted; the cases mentioned below are only used to explain the application, and are used to facilitate the description of the application and simplify the description, therefore, cannot be understood as a limitation of the application.

[0029] The application will be described in detail below in combination with the embodiments.

[0030] Embodiment 1

[0031] As Figure 1As shown, first, 6.801 g (0.11 mol) of boric acid and 9.6 g (0.05 mol) of pentaerythritol were mixed with 50 mL of toluene (Toluece) in a 250 mL single-necked flask, which was connected with a glass water separator connected with a spherical condenser at the top and an oil bath device with a thermometer and a magnetic stirrer at the bottom. After opening the condensate water, the system was reacted at 110°C oil bath until no water was generated in the water separator. Then continue to heat until the toluene in the flask is completely evaporated. After the reaction, the substance in the flask was recrystallized with acetone, and then dried at 50°C to constant weight, finally 9.748 g of white solid was obtained, which was intermediate product I.

[0032] 9.4 g (0.05 mol) of intermediate product I ground into powder and 59.8 g (0.1 mol) of aqueous aminotrimethylene phosphonic acid were added to a three-necked flask, mixed uniformly, and placed in the same device as in step (1). After opening the stirring, the reaction was carried out at 130°C oil bath until no water vapor was distilled out. After the temperature decreased, the transparent viscous liquid was obtained after drying to constant weight in a 50°C oven, which was intermediate product II.

[0033] 37.5 g (0.05 mol) of intermediate product II and 12.12 g (0.2 mol) of urea were added to a three-necked flask, then 100 mL of water was added as a solvent, and the three-necked flask was equipped with a spherical condenser, a magnetic stirrer, and an oil bath device with a thermometer. After opening the condensate water and stirring, the system was heated to reflux at 160°C oil bath for about 2 hours until the solution changed from white emulsion to colorless transparent state. After the solution was cooled, the solution was transferred to a pear-shaped bottle, the excess solvent was removed by a rotary evaporator, and finally dried to constant weight at 50°C, finally a light yellow oily liquid was obtained, which was the final product.

[0034] Example 2

[0035] First, 6.801 g (0.11 mol) of boric acid and 9.6 g (0.05 mol) of pentaerythritol were mixed with 60 mL of ethylbenzene in a 250 mL single-necked flask, which was connected with a glass water separator connected with a spherical condenser at the top and an oil bath device with a thermometer and a magnetic stirrer at the bottom. After opening the condensate water, the system was reacted at 120°C oil bath until no water was generated in the water separator. Then continue to heat until the toluene in the flask is completely evaporated. After the reaction, the substance in the flask was recrystallized with acetone, and then dried at 50°C to constant weight, finally 9.748 g of white solid was obtained, which was intermediate product I.

[0036] Into a three-necked flask, 18.8 g (0.1 mol) of intermediate product I ground into powder and 119.6 g (0.2 mol) of aminotrimethylenephosphonic acid were added. After mixing, the same apparatus as in step (1) was used. After the stirring was started, the reaction was carried out at an oil bath temperature of 140°C until no water vapor was distilled off. After the temperature was lowered, drying to constant weight in an oven at 50°C gave a transparent viscous liquid, which was intermediate product II.

[0037] Into a three-necked flask, 75.0 g (0.1 mol) of intermediate product II and 24.024 g (0.4 mol) of urea were added, and 200 mL of water was added as solvent. The three-necked flask was equipped with a spherical condenser, a magnetic stirrer and an oil bath apparatus with a thermometer. After the condenser and the stirring were started, the system was heated to reflux at an oil bath temperature of 170°C for about 2 hours until the solution changed from a white emulsion to a colorless transparent state. After the solution was cooled, it was transferred to a pear-shaped flask, the excess solvent was removed by a rotary evaporator, and finally dried to constant weight at 50°C. A light yellow oily liquid was obtained, which was the final product.

[0038] Example 3

[0039] The synthesis of intermediate product I was the same as in Example 1.

[0040] Into a three-necked flask, 18.8 g (0.1 mol) of intermediate product I ground into powder and 179.4 g (0.3 mol) of aminotrimethylenephosphonic acid were added. After mixing, the same apparatus as in step (1) was used. After the stirring was started, the reaction was carried out at an oil bath temperature of 140°C until no water vapor was distilled off. After the temperature was lowered, drying to constant weight in an oven at 50°C gave a transparent viscous liquid, which was intermediate product II.

[0041] Into a three-necked flask, 75.0 g (0.1 mol) of intermediate product II and 30.03 g (0.5 mol) of urea were added, and 150 mL of water was added as solvent. The three-necked flask was equipped with a spherical condenser, a magnetic stirrer and an oil bath apparatus with a thermometer. After the condenser and the stirring were started, the system was heated to reflux at an oil bath temperature of 160°C for about 3 hours until the solution changed from a white emulsion to a colorless transparent state. After the solution was cooled, it was transferred to a pear-shaped flask, the excess solvent was removed by a rotary evaporator, and finally dried to constant weight at 50°C. A light yellow oily liquid was obtained, which was the final product.

[0042] Example 4

[0043] The synthesis of intermediate product I was the same as in Example 1.

[0044] Into a three-necked flask, 18.8 g (0.1 mol) of intermediate product I ground into powder and 239.2 g (0.4 mol) of aminotrimethylenephosphonic acid were added, and after mixing, the same apparatus as in step (1) was used. After the stirring was turned on, the reaction was carried out under an oil bath at 120°C until no water vapor was distilled out. After the temperature was lowered, drying was carried out in an oven at 50°C until a constant weight was obtained, and a transparent viscous liquid was obtained, which was intermediate product II.

[0045] Into a three-necked flask, 75.0 g (0.1 mol) of intermediate product II and 36.04 g (0.6 mol) of urea were added, and then 170 mL of water was added as a solvent, and the three-necked flask was equipped with a spherical condenser, a magnetic stirrer, and an oil bath device with a thermometer. After the condensation water and stirring were turned on, the system was heated to reflux under an oil bath at 170°C for about 2 hours until the solution changed from a white emulsion to a colorless transparent state. After the solution was cooled, the solution was transferred to a pear-shaped bottle, the excess solvent was removed by a rotary evaporator, and finally dried to a constant weight at 50°C, and finally a light yellow oily liquid was obtained, which was the final product.

[0046] Example 5

[0047] The synthesis method of intermediate product I is the same as in Example 1.

[0048] Into a three-necked flask, 1.88 g (0.01 mol) of intermediate product I ground into powder and 11.96 g (0.02 mol) of aminotrimethylenephosphonic acid were added, and after mixing, the same apparatus as in step (1) was used. After the stirring was turned on, the reaction was carried out under an oil bath at 120°C until no water vapor was distilled out. After the temperature was lowered, drying was carried out in an oven at 50°C until a constant weight was obtained, and a transparent viscous liquid was obtained, which was intermediate product II.

[0049] Into a three-necked flask, 15 g (0.02 mol) of intermediate product II and 4.805 g (0.08 mol) of urea were added, and then 150 mL of water was added as a solvent, and the three-necked flask was equipped with a spherical condenser, a magnetic stirrer, and an oil bath device with a thermometer. After the condensation water and stirring were turned on, the system was heated to reflux under an oil bath at 170°C for about 2 hours until the solution changed from a white emulsion to a colorless transparent state. After the solution was cooled, the solution was transferred to a pear-shaped bottle, the excess solvent was removed by a rotary evaporator, and finally dried to a constant weight at 50°C, and finally a light yellow oily liquid was obtained, which was the final product.

[0050] As shown in Figure 2 the contrast scanning electron microscope photos of the carbon residue after the combustion of the pure cotton fabric, the treated cotton fabric, and the treated cotton fabric of the flame retardant of the present application. From Figure 2As can be seen, the surface of the fabric fibers treated with the flame retardant is enriched with a layer of particulate matter, indicating that the flame retardant has successfully adhered to the cotton fabric. After combustion, the cotton fibers remain intact, but some small bubbles have appeared on their surface. This is due to the release of ammonia gas from the nitrogen in the unreacted ammonium ions after heating. Further magnification reveals film-like substances and blocky particles on the surface of the cotton fibers. The results show that the use of this flame retardant significantly improves the char formation performance of the fabric.

[0051] like Figure 3 The figure shows the limiting oxygen index (LOI) test results of cotton fabric treated with the synthetic flame retardant in Example 1. Pure cotton fabric is highly flammable in atmospheric conditions, with an LOI value of only 18.3%. When the weight gain of the treated cotton fabric reaches 10.1%, the LOI value increases to 33.2%, and it can self-extinguish under natural conditions, meeting the standard for flame-retardant cotton fabric. Further increasing the flame retardant concentration further increases the LOI value of the fabric; when the weight gain reaches 20.4%, the LOI value of the treated fabric reaches 44.7%. The flame retardant involved in this invention has a good flame-retardant effect on cotton fabrics, and requires a small amount while achieving high flame-retardant efficiency.

[0052] like Figure 4 The figure shows the tensile strength test results of cotton fabric and pure cotton fabric treated with the synthetic flame retardant in Example 1. The warp and weft tensile strengths of the pure cotton fabric were 474 and 437 N, respectively, and the elongation at break were 5.23% and 29.36%, respectively. The tensile strength of the cotton fabric treated with the flame retardant exceeded that of the pure cotton fabric, and the elongation at break was also improved, with the highest increase being approximately 12.9%. This may be because when the flame retardant content is low, all the P-ONH4+ in the flame retardant reacts with the -CH2OH on cellulose, leading to excessive cross-linking. When the flame retardant content increases, the excess flame retardant competes with the -CH2OH on cellulose, causing some voids to be filled by the flame retardant. Under tensile stress, the flame retardant molecules bear part of the load, thereby increasing the tensile strength and increasing the toughness to a certain extent.

[0053] Those skilled in the art will recognize that the experimental examples shown herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various modifications to other aspects of the invention without departing from its spirit, based on the technical teachings disclosed herein, and these modifications are still within the scope of protection of the invention.

Claims

1. A boron-phosphorus-nitrogen synergistic flame retardant, wherein the flame retardant has the following structural formula: 。 2. The preparation method of the boron-phosphorus-nitrogen synergistic flame retardant as described in claim 1, characterized in that, Includes the following steps: (1) Pentaerythritol and boric acid were mixed and reacted. After the reaction was completed, recrystallization was performed to synthesize intermediate product I for later use. The structural formula of intermediate product I is as follows: ； (2) Add intermediate product I and an aqueous solution of aminotrimethylene phosphoric acid to the reaction apparatus, heat and stir until dissolved and reacted, until no water vapor is distilled out; after cooling, remove the reaction product, dry it in an oven to constant weight, and obtain a transparent viscous liquid, which is intermediate product II; the structural formula of intermediate product II is: ； (3) Add urea and intermediate product II into the reaction vessel, add solvent, heat and stir until dissolved; (4) After cooling, the product obtained in step (3) is subjected to a rotary evaporator to remove excess solvent and then dried to constant weight to obtain a pale yellow oily liquid, which is the target flame retardant.

3. The preparation method of a boron-phosphorus-nitrogen synergistic flame retardant according to claim 2, characterized in that, In step (1), the molar ratio of pentaerythritol to boric acid is 1:2~7.

4. The preparation method of a boron-phosphorus-nitrogen synergistic flame retardant according to claim 2, characterized in that, In step (1), the reagent used for recrystallization is either acetone or acetonitrile.

5. The preparation method of a boron-phosphorus-nitrogen synergistic flame retardant according to claim 2, characterized in that, In step (2), the molar ratio of intermediate product I and aqueous aminotrimethylene phosphoric acid is 1:2~5.

6. The preparation method of a boron-phosphorus-nitrogen synergistic flame retardant according to claim 2, characterized in that, In step (2), the reaction is heated to 110~130℃; then cooled to 40~60℃.

7. The preparation method of a boron-phosphorus-nitrogen synergistic flame retardant according to claim 2, characterized in that, In step (3), the molar ratio of intermediate product II to urea is 1:2~5.

8. The preparation method of a boron-phosphorus-nitrogen synergistic flame retardant according to claim 2, characterized in that, In step (3), the solvent used is any one of toluene and ethylbenzene or a mixture thereof in any proportion.

9. The preparation method of a boron-phosphorus-nitrogen synergistic flame retardant according to claim 2, characterized in that, In step (3), the heating temperature is 150~160℃ and the reaction time is 1~5h.

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