A phosphorus-nitrogen-boron durable flame retardant and a preparation method thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- QINGDAO UNIV
- Filing Date
- 2023-09-11
- Publication Date
- 2026-07-21
Smart Images
Figure CN117430638B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of functional additives, specifically relating to a phosphorus-nitrogen-boron durable flame retardant and its preparation method. Background Technology
[0002] Cotton fabrics are widely used in clothing, decoration, military, and industrial textiles due to their excellent softness, moisture absorption, and breathability. However, cotton fabrics are highly flammable, and the combustible materials produced during combustion can exacerbate the burning process. Therefore, it is necessary to introduce suitable flame retardants to prevent the decomposition and combustion of cotton fabrics.
[0003] To date, numerous reports have been published on major flame-retardant elements such as halogens, phosphorus, nitrogen, silicon, boron, and metals. Halogens are largely banned due to their corrosive and carcinogenic properties. Flame retardants containing silicon, boron, and metals have smoke-suppressing properties but suffer from low flame-retardant efficiency. Environmentally friendly flame retardants such as those containing proteins and DNA, which have emerged in recent years, also face challenges due to their high cost and difficulty in obtaining raw materials. Therefore, phosphorus-based flame retardants have attracted attention. Patent CN116289200A discloses an intumescent flame retardant synthesized by an epoxy ring-opening addition reaction of phytic acid and tris(epoxypropyl)isocyanurate. After treatment, the physical properties of cotton fabrics did not change significantly; however, the limiting oxygen index only increased to 32.0%, indicating low flame-retardant efficiency, and this structure lacks smoke-suppressing functionality. Although significant progress has been made in the development of flame-retardant cotton fabrics, a challenge in this field is that fabrics gradually lose their flame-retardant properties after washing. Currently, the most commonly used durable flame retardants for cotton fabrics on the market are Proban and Pyrovatex CP, but both of these flame retardants have the problem of releasing free formaldehyde. While the reactive phosphorus-nitrogen-boron synergistic flame retardant disclosed in patent CN114671916A possesses low smoke, low toxicity, environmental friendliness, and high flame retardancy, its washability still needs improvement. Therefore, it is necessary to provide a flame retardant with better durability and its preparation method to further enhance the flame retardant properties of fabrics over a longer period. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a phosphorus-nitrogen-boron durable flame retardant and its preparation method. By adding more water-resistant reactive groups to the molecule, the durability of the flame retardant is improved, and it is green and environmentally friendly, with no formaldehyde release and high product purity.
[0005] The technical solution adopted is as follows:
[0006] A phosphorus-nitrogen-boron durable flame retardant, the chemical structure of which is as follows:
[0007]
[0008] The preparation method of the above-mentioned phosphorus-nitrogen-boron durable flame retardant includes the following synthesis steps:
[0009] (1) Add paraformaldehyde and ethanolamine in a certain molar ratio together with the solvent into the reaction apparatus, and heat to 50-100℃ and stir.
[0010] (2) Dissolve a certain amount of phosphorous acid in a solvent and slowly add it to the reaction apparatus in step (1), heat it to 60-100℃ and continue the reaction for 4-8 hours;
[0011] (3) Take another molar amount of urea, dissolve it in a solvent, add it to the reaction apparatus in step (2), heat it to the reflux temperature and stir the reaction for 1 to 5 hours;
[0012] (4) The product obtained in step (3) is subjected to vacuum distillation to remove the solvent, then washed, purified and dried to obtain the intermediate product;
[0013] (5) Boric acid and pentaerythritol in a certain molar ratio were used to synthesize boron spirocyclic rings in toluene solvent for later use;
[0014] (6) Add a certain molar amount of cyanuric chloride and solvent together into the reaction apparatus, heat to 40-60°C and stir until dissolved;
[0015] (7) Take a certain molar of intermediate product, dissolve it in the corresponding solvent, and add it to the reaction apparatus in step (6). Heat it to 40-60℃ and continue the reaction for 4-5 hours.
[0016] (8) Take a certain molar of the boron spirocyclic synthesized in step (5), dissolve it in the corresponding solvent, add it to the reaction apparatus in step (7), heat it to 70-100℃ and continue the reaction for 4-8 hours;
[0017] (9) The product obtained in step (8) is subjected to vacuum distillation to remove the solvent, then washed, purified and dried to obtain the final product.
[0018] Preferably, the molar ratio of paraformaldehyde, phosphorous acid and ethanolamine is 2:2:1, wherein the number of moles of paraformaldehyde is calculated based on the formaldehyde monomer contained therein.
[0019] Preferably, the molar ratio of phosphorous acid to urea is 2:3 to 5.
[0020] Preferably, the solvent in steps (1), (2) and (3) is any one of deionized water, ethanol and isopropanol or a mixture thereof in any proportion.
[0021] Preferably, the solvent in steps (6), (7) and (8) is any one of deionized water, tetrahydrofuran and isopropanol or a mixture thereof in any proportion.
[0022] Preferably, the solvent used for washing and purification in steps (4) and (9) is at least one of tetrahydrofuran, dimethyl sulfoxide, and acetonitrile.
[0023] Preferably, the reflux temperature in step (3) is the boiling point temperature of the mixture in the reaction apparatus.
[0024] Preferably, in step (5), the molar ratio of boric acid to pentaerythritol is 2 to 2.2:1.
[0025] Preferably, the molar ratio of the cyanuric chloride, intermediate product and boron spirocyclic ring is 2 to 3:4:1.
[0026] Preferably, the method for synthesizing boron spirocyclic rings is as follows: boric acid, pentaerythritol, and toluene are placed in a reaction apparatus, heated and stirred under reflux until no more water is generated, and the reaction is stopped; the solvent toluene is removed by separation to obtain a yellow viscous liquid, which is thoroughly washed with tetrahydrofuran until it is colorless and transparent, and then dried under vacuum at 45°C to obtain a yellow transparent viscous liquid, which is the final product.
[0027] Compared with the prior art, the advantages of the present invention are:
[0028] The present invention provides a phosphorus-nitrogen-boron durable flame retardant, which, as can be seen from its chemical structure, possesses more reactive groups. On the one hand, the flame retardant forms more chemical bonds with the fabric, resulting in a stronger bond and effectively improving the wash resistance of the flame retardant. On the other hand, the excess reactive groups will play a role during combustion, leading to a better and more efficient flame retardant effect.
[0029] The preparation method provided by this invention has the advantages of simple synthesis process, mild conditions, no formaldehyde release, green and environmentally friendly, and high product purity. Attached Figure Description
[0030] Figure 1 The images show a comparative scanning electron microscope images of the reactive phosphorus-nitrogen-boron synergistic flame retardant prepared in this invention on pure cotton fabric, treated cotton fabric, and the char residue after burning treated cotton.
[0031] Figure 2 The limiting oxygen index value is the value of the cotton fabric treated with the synthetic flame retardant in Example 1 of this invention.
[0032] Figure 3 The images show the limiting oxygen index test results and scanning electron microscope images of the cotton fabric after washing following treatment with the synthetic flame retardant according to this invention. Detailed Implementation
[0033] The accompanying drawings are for illustrative purposes only; it should be understood that common knowledge or prior art in the embodiments may be omitted; the examples mentioned below are only used to explain the present invention, in order to facilitate the description of the present invention and simplify the description, and therefore should not be construed as limiting the present invention.
[0034] The present invention will now be described in detail with reference to the embodiments.
[0035] Example 1:
[0036] In a 250 mL three-necked flask equipped with an oil-water separator and a spherical condenser, 18.6 g of boric acid, 22.4 g of pentaerythritol, and 40 mL of toluene were added. The mixture was heated and stirred under reflux until no more water was generated, at which point the reaction was terminated. The solvent toluene was removed by separation, yielding a clear, viscous liquid. This liquid was thoroughly washed with tetrahydrofuran until colorless and transparent, and then dried under vacuum at 45 °C to obtain 28.2 g of a colorless, clear, viscous liquid, with a yield of approximately 68%. The obtained boron spirocyclic rings were reserved for later use.
[0037] Add 12g of paraformaldehyde, 12.37g of ethanolamine, and 80mL of deionized water to a three-necked flask equipped with a thermometer, magnetic stirrer, and spherical condenser. Heat the flask to 100℃. Dissolve 32.80g of phosphorous acid in 50mL of deionized water and add it to the flask. Stir the reaction for 4 hours. Dissolve 36g of urea in 200mL of deionized water and add it to the flask. Heat the flask to reflux and stir the reaction for 3 hours. Remove the solvent by vacuum distillation, then wash with acetonitrile for purification and dry to obtain the intermediate product for later use.
[0038] 18.4 g of cyanuric chloride and 80 mL of tetrahydrofuran were added to a three-necked flask equipped with a thermometer, magnetic stirrer, and spherical condenser. The temperature was raised to 60 °C, and 63.4 g of the intermediate product was dissolved in 100 mL of deionized water and added to the flask. The mixture was stirred and reacted for 4 h. Subsequently, the temperature was raised to 100 °C, and 9.35 g of boron spirocyclic compound was dissolved in 100 mL of deionized water and added to the flask. The mixture was stirred and reacted for 4 h. The resulting product was purified with acetonitrile and dried under vacuum at 50 °C to obtain a yellow, transparent, high-viscosity liquid, which is the reactive phosphorus-nitrogen-boron synergistic flame retardant.
[0039] The reaction apparatus at each stage is standard equipment used in actual operation, such as a three-necked flask, and therefore will not be described in detail.
[0040] Example 2:
[0041] In a 250 mL three-necked flask equipped with an oil-water separator and a spherical condenser, 20.46 g of boric acid, 22.4 g of pentaerythritol, and 40 mL of toluene were added. The mixture was heated and stirred under reflux until no more water was generated, at which point the reaction was terminated. The solvent toluene was removed by separation, yielding a clear, viscous liquid. This liquid was thoroughly washed with tetrahydrofuran until colorless and transparent, and then dried under vacuum at 45 °C to obtain 28.2 g of a colorless, clear, viscous liquid, with a yield of approximately 68%. The obtained boron spirocyclic rings were reserved for later use.
[0042] 24 g of paraformaldehyde, 24.8 g of ethanolamine, and 160 mL of isopropanol were added to a three-necked flask equipped with a thermometer, a magnetic stirrer, and a spherical condenser. The temperature was raised to 80 °C. 65.6 g of phosphorous acid was dissolved in 100 mL of isopropanol and added to the flask. The mixture was stirred and reacted for 4 h. 97 g of urea was dissolved in 200 mL of isopropanol and added to the flask. The temperature was raised to reflux and the mixture was stirred and reacted for 3 h. The solvent was removed by vacuum distillation, and the product was then washed with acetonitrile and dried to obtain the intermediate product for later use.
[0043] 9.2 g of cyanuric chloride and 40 mL of tetrahydrofuran were added to a three-necked flask equipped with a thermometer, magnetic stirrer, and spherical condenser. The temperature was raised to 60 °C, and 31.7 g of the intermediate product was dissolved in 50 mL of isopropanol and added to the flask. The mixture was stirred and reacted for 4 h. Subsequently, the temperature was raised to 100 °C, and 4.68 g of boron spirocyclic compound was dissolved in 100 mL of isopropanol and then dissolved in deionized water and added to the flask. The mixture was stirred and reacted for 4 h. The resulting product was purified with acetonitrile and dried under vacuum at 50 °C to obtain a yellow, transparent, high-viscosity liquid, which is the reactive phosphorus-nitrogen-boron synergistic flame retardant.
[0044] Example 3:
[0045] The synthesis method of boron spirocyclic ring is the same as in Example 1.
[0046] 24 g of paraformaldehyde, 24.8 g of ethanolamine, and 160 mL of ethanol were added to a three-necked flask equipped with a thermometer, a magnetic stirrer, and a spherical condenser. The temperature was raised to 100 °C. 65.6 g of phosphorous acid was dissolved in 100 mL of ethanol and added to the flask. The mixture was stirred and reacted for 4 h. 120 g of urea was dissolved in 200 mL of ethanol and added to the flask. The temperature was raised to reflux and the mixture was stirred and reacted for 3 h. The solvent was removed by vacuum distillation. The product was then washed with dimethyl sulfoxide and dried to obtain the intermediate product for later use.
[0047] 18.4 g of cyanuric chloride and 80 mL of tetrahydrofuran were added to a three-necked flask equipped with a thermometer, magnetic stirrer, and spherical condenser. The temperature was raised to 60 °C, and 63.4 g of the intermediate product was dissolved in 100 mL of isopropanol and added to the flask. The mixture was stirred and reacted for 4 h. Subsequently, the temperature was raised to 100 °C, and 9.35 g of boron spirocyclic compound was dissolved in 100 mL of ethanol and added to the flask. The mixture was stirred and reacted for 4 h. The resulting product was purified with dimethyl sulfoxide and dried under vacuum at 50 °C to obtain a yellow, transparent, high-viscosity liquid, which is the reactive phosphorus-nitrogen-boron synergistic flame retardant.
[0048] Example 4:
[0049] The synthesis method of boron spirocyclic ring is the same as in Example 1.
[0050] 24 g of paraformaldehyde, 24.8 g of ethanolamine, and 160 mL of ethanol were added to a three-necked flask equipped with a thermometer, a magnetic stirrer, and a spherical condenser. The temperature was raised to 100 °C. 65.6 g of phosphorous acid was dissolved in 100 mL of ethanol and added to the flask. The mixture was stirred and reacted for 8 h. 120 g of urea was dissolved in 200 mL of ethanol and added to the flask. The temperature was raised to reflux and the mixture was stirred and reacted for 3 h. The solvent was removed by vacuum distillation. The product was then washed with dimethyl sulfoxide and dried to obtain the intermediate product for later use.
[0051] 27.6 g of cyanuric chloride and 80 mL of tetrahydrofuran were added to a three-necked flask equipped with a thermometer, magnetic stirrer, and spherical condenser. The temperature was raised to 60 °C, and 63.4 g of the intermediate product was dissolved in 100 mL of isopropanol and added to the flask. The mixture was stirred and reacted for 5 h. Subsequently, the temperature was raised to 100 °C, and 9.35 g of boron spirocyclic compound was dissolved in 100 mL of ethanol and added to the flask. The mixture was stirred and reacted for 8 h. The resulting product was purified with dimethyl sulfoxide and dried under vacuum at 50 °C to obtain a yellow, transparent, high-viscosity liquid, which is the reactive phosphorus-nitrogen-boron synergistic flame retardant.
[0052] Example 5:
[0053] The synthesis method of boron spirocyclic ring is the same as in Example 1.
[0054] Add 24g of paraformaldehyde, 24.8g of ethanolamine, and 160mL of isopropanol to a three-necked flask equipped with a thermometer, magnetic stirrer, and spherical condenser. Heat to 100℃ and stir for 1 hour. Dissolve 65.6g of phosphorous acid in 100mL of isopropanol and add it to the flask. Stir and react for 6 hours. Dissolve 96g of urea in 200mL of isopropanol. Heat to reflux and stir for 3 hours. Remove the solvent by vacuum distillation, then wash with acetonitrile for purification and dry to obtain the intermediate product for later use.
[0055] 27.6 g of cyanuric chloride and 80 mL of tetrahydrofuran were added to a three-necked flask equipped with a thermometer, magnetic stirrer, and spherical condenser. The temperature was raised to 60 °C, and 63.4 g of the intermediate product was dissolved in 100 mL of isopropanol and added to the flask. The mixture was stirred and reacted for 5 h. Subsequently, the temperature was raised to 100 °C, and 9.35 g of boron spirocyclic compound was dissolved in 100 mL of isopropanol and added to the flask. The mixture was stirred and reacted for 6 h. The resulting product was purified with acetonitrile and dried under vacuum at 50 °C to obtain a yellow, transparent, high-viscosity liquid, which is the reactive phosphorus-nitrogen-boron synergistic flame retardant.
[0056] like Figure 1As shown, the left image is a scanning electron microscope (SEM) image of pure cotton fabric, the middle image is a SEM image of cotton fabric treated with a flame retardant, and the right image is a SEM image of the char residue from the combustion of the treated cotton fabric. The images show that the surface of the treated fabric fibers is rougher than that of pure cotton fabric, which is a result of the flame retardant adhesion. After combustion, the treated fabric retained a complete and continuous char residue, and the fabric structure was not damaged, while the pure cotton fabric left almost no char residue after combustion. The results indicate that the use of this flame retardant significantly improved the char formation performance of the fabric.
[0057] like Figure 2 The figure shows the limiting oxygen index (LOI) test results of cotton fabric treated with the synthetic flame retardant in Example 1. The LOI of the untreated fabric is approximately 18.4%, making it highly flammable in the atmosphere. When the weight gain after treatment is 10.1%, the LOI of the fabric increases to 30.0%, enabling it to self-extinguish in air and meeting the standard for flame-retardant fabrics. Further increasing the flame retardant concentration further increases the LOI of the fabric; when the weight gain reaches 29.7%, the LOI reaches 48.8%. The flame retardant involved in this invention has a good flame-retardant effect on cotton fabrics, requires a small amount, and has high flame-retardant efficiency.
[0058] like Figure 3 The figure shows the limiting oxygen index (LOI) test results and scanning electron microscope (SEM) images of flame-retardant cotton fabrics with different weight gain rates after washing. The cotton fabric treated with the synthetic flame retardant was placed in a 250 ml Erlenmeyer flask, and then 200 ml of water containing 0.15 wt% was added. The flask was placed in a shaking water bath at 80 rpm and a temperature of 48 °C. Five washing cycles were defined as 45 min. When the washing cycle was 10, the LOI value decreased compared to the unwashed flame-retardant-treated cotton fabric. This is because some flame retardants agglomerated on the fiber surface and did not react with the cotton. After washing, these agglomerates disappeared, leading to a decrease in the flame-retardant properties of the synthetic flame-retardant-treated cotton fabric. After 50 washing cycles, the LOI value of the synthetic flame-retardant-treated cotton fabric was not significantly different from that after 10 washes. The values decreased by 3.4%, 4.1%, and 4.8%, respectively. The SEM image of the fabric with a 30% weight gain after 50 washing cycles is shown in the figure. The fiber surface is smooth yet still possesses excellent flame-retardant properties, indicating that the flame retardant has penetrated the fiber interior and reacted chemically with the cellulose. The flame retardant involved in this invention provides better flame-retardant durability for cotton fabrics.
[0059] 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 phosphorus-nitrogen-boron durable flame retardant, characterized in that, The chemical structure of the phosphorus-nitrogen-boron durable flame retardant is as follows: 。 2. The method for preparing a phosphorus-nitrogen-boron durable flame retardant as described in claim 1, characterized in that, The synthesis steps are as follows: (1) Add paraformaldehyde and ethanolamine in a certain molar ratio together with the solvent into the reaction apparatus, heat to 70-100℃ and stir until dissolved; (2) Dissolve a certain mole of phosphorous acid in a solvent and slowly add it to the reaction apparatus in step (1), heat to 70-100 °C and continue the reaction for 4-8 h; (3) Take another molar amount of urea, dissolve it in a solvent, add it to the reaction apparatus in step (2), heat it to the reflux temperature and stir the reaction for 1~5 h; (4) The product obtained in step (3) is subjected to vacuum distillation to remove the solvent, then washed, purified and dried to obtain the intermediate product; (5) Boric acid and pentaerythritol in a certain molar ratio are used to synthesize boron spirocyclic compounds in toluene solvent for later use; (6) Add a certain molar amount of cyanuric chloride and solvent together to the reaction apparatus, heat to 40-60 °C and stir until dissolved; (7) Take a certain molar amount of intermediate product, dissolve it in the corresponding solvent, and add it to the reaction apparatus in step (6). Heat it to 40-60 °C and continue the reaction for 4-5 h. (8) Take a certain molar of the boron spirocyclic synthesized in step (5), dissolve it in the corresponding solvent, add it to the reaction apparatus in step (7), heat it to 70-100 °C and continue the reaction for 4-8 h; (9) The product obtained in step (8) is subjected to vacuum distillation to remove the solvent, then washed, purified and dried to obtain the final product; In steps (1), (2), and (3), the solvent is deionized water; in steps (6), (7), and (8), the solvent is any one of deionized water, tetrahydrofuran, and isopropanol, or a mixture thereof in any proportion.
3. The method for preparing a phosphorus-nitrogen-boron durable flame retardant according to claim 2, characterized in that, The molar ratio of paraformaldehyde, phosphorous acid and ethanolamine is 2:2:1, wherein the number of moles of paraformaldehyde is calculated based on the formaldehyde monomer contained therein.
4. The method for preparing a phosphorus-nitrogen-boron durable flame retardant according to claim 2, characterized in that, The molar ratio of phosphorous acid to urea is 2:3~5.
5. The method for preparing a phosphorus-nitrogen-boron durable flame retardant according to claim 2, characterized in that, The solvent used for washing and purification in steps (4) and (9) is at least one of tetrahydrofuran, dimethyl sulfoxide, and acetonitrile.
6. The method for preparing a phosphorus-nitrogen-boron durable flame retardant according to claim 2, characterized in that, The reflux temperature in step (3) is the boiling point temperature of the mixture in the reaction apparatus.
7. The method for preparing a phosphorus-nitrogen-boron durable flame retardant according to claim 2, characterized in that, In step (5), the molar ratio of boric acid to pentaerythritol is 2~2.2:
1.
8. The method for preparing a phosphorus-nitrogen-boron durable flame retardant according to claim 2, characterized in that, The molar ratio of cyanuric chloride, intermediate product and boron spirocyclic compound is 2~3:4:1.