Durable smoke-suppressing flame retardant and method of making same

Abstract

The present application belongs to the field of functional auxiliaries, and particularly relates to a durable smoke-suppressing flame retardant and a preparation method thereof. In the preparation of the flame retardant, tricyanogen chloride is first added into a reaction device together with a solvent, stirred until the tricyanogen chloride is completely dissolved, and heated to a reflux temperature; a corresponding molar amount of boron spiro ring is dissolved in the solvent and then dropped into the reaction device; after complete reaction, phosphoric acid is diluted with the solvent and then dropped into the reaction device, and then heated, reacted, distilled under reduced pressure, washed, purified, and dried to obtain the target flame retardant. The flame retardant has more reaction groups, forms a more stable chemical bond with the fabric, effectively improves the water washing resistance of the flame retardant, and has a better synergistic effect between the smoke-suppressing component and the flame-retardant component, effectively improving the smoke-suppressing performance of the flame retardant.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of functional auxiliaries, and particularly relates to a durable smoke-inhibiting flame retardant and a preparation method thereof. BACKGROUND

[0002] Cotton fabric is widely used in clothing fabrics, industrial fabrics, home textiles and other special fields due to its excellent moisture absorption and ventilation, biocompatibility, and wide source, and is a renewable resource product. However, cotton fabric contains a large amount of carbon-hydrogen structure which is easy to ignite and cause fire, so it needs to be treated with flame retardant to meet the high-value application in many fields. Phosphorus-containing flame retardant is highly valued in the cotton flame retardant market due to its excellent flame retardance and durability. The cotton fabric treated with the commonly used Proban and Pyrovatex CP flame retardants has the advantages of colorless, low strength loss, high durability at the initial stage of use. However, with the increase of storage time, the formaldehyde content gradually increases, which endangers the life and health of the user.

[0003] In order to overcome the problem of formaldehyde release of the durable flame retardant, current advanced research work indicates some feasible flame-retardant finishing schemes for cotton fabric, such as using polysiloxane coating, multi-carboxylic acid crosslinking, and chlorinated reagent substitution, but these schemes do not show the inhibition effect on smoke release. Patent CN118288377A discloses a scheme for realizing the flame-retardant and smoke-inhibiting effect of wood by impregnating the wood with ammonium dihydrogen phosphate and nano-silicon dioxide. The peak heat release rate of the wood prepared by the scheme is reduced from 460.1 KW / m 2 to 38.2 KW / m 2 , and the smoke release amount is reduced from 4.36 m 2 to 1.55 m 2 . Ammonium dihydrogen phosphate is the flame-retardant component, and silicon dioxide is the main smoke-inhibiting component, but the smoke-inhibiting effect is not significant. Patent CN118257134A discloses a scheme for preparing flame-retardant and smoke-inhibiting cotton fabric by impregnating the pretreated cotton fabric with a zirconium tetrachloride aqueous solution. The LOI value of the cotton fabric prepared by the scheme is as high as 32.7%, and the maximum specific optical density is as low as 22.1. However, heavy metal elements not only pose a threat to human life and health, but also some metal flame retardants use rare earth elements, which is not in line with the concept of sustainable development. Therefore, it is necessary to provide a flame retardant with better durability, better smoke-inhibiting property and the ability to maintain the mechanical properties of cotton fabric, and a preparation method thereof. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a durable smoke-inhibiting flame retardant and a preparation method thereof. By increasing more wash-resistant reaction groups and more smoke-inhibiting elements in the molecule, the durability and smoke-inhibiting property of the flame retardant are improved, and the product is green, environmentally friendly, formaldehyde-free, and high in purity.

[0005] The technical scheme adopted is as follows:

[0006] A durable smoke-suppressing flame retardant, the chemical structure of which is as follows:

[0007]

[0008] The preparation method of the above-mentioned durable smoke-suppressing flame retardant, the synthesis steps of which are as follows:

[0009] (1) Synthesizing boron spiro ring by using boric acid and pentaerythritol in an organic solvent, for standby use;

[0010] (2) Adding cyanuric chloride and an organic solvent into a reaction device, and heating to reflux temperature while introducing nitrogen;

[0011] (3) Dissolving the boron spiro ring synthesized in step (1) in an organic solvent, and adding into the reaction device in step (2) for reaction;

[0012] (4) Dissolving and diluting phosphoric acid with an organic solvent, and adding dropwise into the reaction device for reaction while heating, and adjusting the pH of the reaction system to 6.5-7.0 during the whole reaction process;

[0013] (5) Removing the solvent from the product obtained in step (4) by reduced pressure distillation, and then washing, purifying and drying, to obtain.

[0014] Preferably, in step (1), the molar ratio of boric acid to pentaerythritol is 2-2.3:1; and the organic solvent is any one of toluene, n-hexane, cyclohexane, dimethylbenzene and benzene.

[0015] Preferably, in step (1), the boric acid and pentaerythritol are heated and stirred to reflux until no water is generated, and then the reaction is ended; the organic solvent is removed by liquid separation, and the obtained transparent viscous liquid is washed with tetrahydrofuran until it is colorless and transparent, and then vacuum dried.

[0016] Preferably, in step (1), the molar ratio of boric acid to pentaerythritol is 2-2.3:1

[0017] Preferably, in step (2), the reflux temperature is the boiling point temperature of the mixed liquid in the reaction device, and the organic solvent is any one of tetrahydrofuran, ethanol and acetone.

[0018] Preferably, in step (3), the organic solvent is tetrahydrofuran, ethanol or acetone, and the reaction time is 8-12 h.

[0019] Preferably, in steps (2) and (3), the molar ratio of cyanuric chloride, boron spiro ring and phosphoric acid used is 1:3:3.

[0020] Preferably, in the step (4), the organic solvent is tetrahydrofuran, ethanol or acetone, and the dropping speed is 1-10 drops / min.

[0021] Preferably, in the step (4), the heating temperature is 110-130℃, and the reaction time is 4-8h; the basic substance used is ammonia.

[0022] Preferably, in the step (5), the solvent used for washing and purification is at least one of tetrahydrofuran, dimethyl sulfoxide and acetonitrile.

[0023] Compared with the prior art, the present application has the advantages of:

[0024] The durable smoke-suppressing flame retardant provided by the present application has more smoke-suppressing groups and reaction groups, as can be seen from the chemical structural formula. On the one hand, the flame retardant and the fabric produce more chemical connections, and are more firmly combined with the fabric, which can effectively improve the wash-resistant performance of the flame retardant. On the other hand, the excess reaction groups will act during combustion, and the flame-retardant and smoke-suppressing effects are also better and more efficient. The preparation method provided by the present application has the advantages of simple synthesis process, mild conditions, no formaldehyde release, green environmental protection, high product purity and the like. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The figure is a comparison of the scanning electron microscope photos of the pure cotton fabric, the treated cotton fabric and the residual carbon after the treated cotton fabric is burned, which are treated by the durable smoke-suppressing flame retardant prepared by the present application.

[0026] Figure 2 The figure is the limiting oxygen index value of the cotton fabric treated by the flame retardant synthesized in Example 1.

[0027] Figure 3 The figure is the limiting oxygen index test result of the cotton fabric treated by the flame retardant after washing. 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 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 of the present application.

[0029] The present application will be described in detail below in combination with examples.

[0030] Example 1:

[0031] In a 250 mL three-necked flask equipped with a water separator and a spherical condenser, 20.3 g of boric acid and 22.4 g of pentaerythritol and 40 mL of cyclohexane were added, heated and stirred to reflux until no water was generated, and the reaction was terminated. The solvent toluene was removed by liquid separation, and a transparent viscous liquid was obtained. The liquid was washed with tetrahydrofuran until it was colorless and transparent, and was dried at 45°C under vacuum to obtain 28.2 g of a colorless transparent viscous liquid, with a yield of about 65.2%. The obtained boron spiro ring was ready for use.

[0032] In a three-necked flask equipped with a thermometer, a magnetic stirrer and a spherical condenser, 18.44 g of cyanuric chloride was added to 200 mL of tetrahydrofuran as a solvent, and was heated and stirred under the protection of nitrogen until the cyanuric chloride was completely dissolved and the temperature was raised to the refluxing temperature. Separately, 2.82 g of the boron spiro ring was dissolved in tetrahydrofuran and was added to the reaction device, and was reacted for 8 h. 14.7 g of phosphoric acid was dissolved in tetrahydrofuran and was slowly added dropwise into the reaction device, and the temperature was raised to 130°C, and was reacted for 4 h. During the whole reaction process, the pH of the reaction system was adjusted to 6.5 by using ammonia water. Subsequently, the liquid in the reaction device was distilled under reduced pressure to remove the solvent, and was washed and purified with tetrahydrofuran and was dried, to obtain a durable smoke suppression flame retardant, with a yield of 86.6%.

[0033] Example 2:

[0034] In a 250 mL three-necked flask equipped with a water separator and a spherical condenser, 23.4 g of boric acid and 22.4 g of pentaerythritol and 40 mL of dimethylbenzene were added, heated and stirred to reflux until no water was generated, and the reaction was terminated. The solvent toluene was removed by liquid separation, and a transparent viscous liquid was obtained. The liquid was washed with tetrahydrofuran until it was colorless and transparent, and was dried at 45°C under vacuum to obtain 28.6 g of a colorless transparent viscous liquid, with a yield of about 64.8%. The obtained boron spiro ring was ready for use.

[0035] In a three-necked flask equipped with a thermometer, a magnetic stirrer and a spherical condenser, 18.44 g of cyanuric chloride was added to 200 mL of tetrahydrofuran as a solvent, and was heated and stirred under the protection of nitrogen until the cyanuric chloride was completely dissolved and the temperature was raised to the refluxing temperature. Separately, 2.82 g of the boron spiro ring was dissolved in tetrahydrofuran and was added to the reaction device, and was reacted for 8 h. 14.7 g of phosphoric acid was dissolved in tetrahydrofuran and was slowly added dropwise into the reaction device, and the temperature was raised to 130°C, and was reacted for 4 h. During the whole reaction process, the pH of the reaction system was adjusted to 6.5 by using ammonia water. Subsequently, the liquid in the reaction device was distilled under reduced pressure to remove the solvent, and was washed and purified with tetrahydrofuran and was dried, to obtain a durable smoke suppression flame retardant, with a yield of 86.6%.

[0036] Example 3:

[0037] In a 250 mL three-necked flask equipped with a water separator and a spherical condenser, 23.4 g of boric acid and 22.4 g of pentaerythritol and 40 mL of benzene were added, heated and stirred to reflux until no water was generated, and the reaction was terminated. The solvent toluene was removed by liquid separation, and a transparent viscous liquid was obtained. The transparent viscous liquid was washed with tetrahydrofuran until it was colorless and transparent. The transparent viscous liquid was dried at 45°C under vacuum to obtain 28.6 g of colorless transparent viscous liquid, with a yield of about 65.7%. The obtained boron spiro ring was ready for use.

[0038] In a three-necked flask equipped with a thermometer, a magnetic stirrer and a spherical condenser, 18.44 g of cyanuric chloride was added to 200 mL of acetone as a solvent. The cyanuric chloride was completely dissolved by heating and stirring under the protection of nitrogen, and the temperature was raised to the refluxing temperature. 2.82 g of boron spiro ring was dissolved in acetone and added to the reaction device. The reaction was carried out for 10 h. 14.7 g of phosphoric acid was dissolved in acetone and diluted, and then slowly added dropwise into the reaction device. The temperature was raised to 120°C, and the reaction was carried out for 6 h. During the whole reaction process, the pH of the reaction system was adjusted to 6.8 by using ammonia water. Subsequently, the liquid in the reaction device was distilled under reduced pressure to remove the solvent, and then washed and purified with tetrahydrofuran and dried to obtain a durable smoke suppression flame retardant, with a yield of 85.2%.

[0039] Example 4:

[0040] In a 250 mL three-necked flask equipped with a water separator and a spherical condenser, 23.4 g of boric acid and 22.4 g of pentaerythritol and 40 mL of benzene were added, heated and stirred to reflux until no water was generated, and the reaction was terminated. The solvent toluene was removed by liquid separation, and a transparent viscous liquid was obtained. The transparent viscous liquid was washed with tetrahydrofuran until it was colorless and transparent. The transparent viscous liquid was dried at 45°C under vacuum to obtain 28.6 g of colorless transparent viscous liquid, with a yield of about 65.7%. The obtained boron spiro ring was ready for use.

[0041] In a three-necked flask equipped with a thermometer, a magnetic stirrer and a spherical condenser, 18.44 g of cyanuric chloride was added to 200 mL of acetone as a solvent. The cyanuric chloride was completely dissolved by heating and stirring under the protection of nitrogen, and the temperature was raised to the refluxing temperature. 2.82 g of boron spiro ring was dissolved in acetone and added to the reaction device. The reaction was carried out for 10 h. 14.7 g of phosphoric acid was dissolved in acetone and diluted, and then slowly added dropwise into the reaction device. The temperature was raised to 120°C, and the reaction was carried out for 6 h. During the whole reaction process, the pH of the reaction system was adjusted to 6.8 by using ammonia water. Subsequently, the liquid in the reaction device was distilled under reduced pressure to remove the solvent, and then washed and purified with tetrahydrofuran and dried to obtain a durable smoke suppression flame retardant, with a yield of 85.2%.

[0042] Example 5:

[0043] In a 250 mL three-necked flask equipped with a water separator and a spherical condenser, 23.4 g of boric acid and 22.4 g of pentaerythritol were added, and 40 mL of n-hexane was added. The mixture was heated and stirred under reflux until no water was generated, and the reaction was terminated. The solvent, toluene, was removed by liquid separation, and a transparent viscous liquid was obtained. The liquid was washed with tetrahydrofuran until it became colorless and transparent. The liquid was dried under vacuum at 45°C to obtain 28.6 g of a colorless transparent viscous liquid, and the yield was about 62.4%. The obtained boron spiro ring was ready for use.

[0044] In a three-necked flask equipped with a thermometer, a magnetic stirrer and a spherical condenser, 18.44 g of cyanuric chloride was added to 200 mL of acetone as a solvent. The mixture was heated and stirred under nitrogen until cyanuric chloride was completely dissolved, and the temperature was raised to the reflux temperature. Separately, 2.82 g of the boron spiro ring was dissolved in acetone and added to the reaction device. The reaction was carried out for 12 h. 14.7 g of phosphoric acid was dissolved in tetrahydrofuran and slowly added to the reaction device. The temperature was raised to 110°C, and the reaction was carried out for 8 h. During the reaction, the pH of the reaction system was adjusted to 6.9 using ammonia water. Subsequently, the liquid in the reaction device was distilled under reduced pressure to remove the solvent, and the product was purified by washing with acetonitrile and drying. Thus, a durable smoke-suppressing flame retardant was obtained, and the yield was 78.6%.

[0045] In a three-necked flask equipped with a thermometer, a magnetic stirrer and a spherical condenser, 18.44 g of cyanuric chloride was added to 200 mL of acetone as a solvent. The mixture was heated and stirred under nitrogen until cyanuric chloride was completely dissolved, and the temperature was raised to the reflux temperature. Separately, 2.82 g of the boron spiro ring was dissolved in acetone and added to the reaction device. The reaction was carried out for 12 h. 14.7 g of phosphoric acid was dissolved in tetrahydrofuran and slowly added to the reaction device. The temperature was raised to 110°C, and the reaction was carried out for 8 h. During the reaction, the pH of the reaction system was adjusted to 6.9 using ammonia water. Subsequently, the liquid in the reaction device was distilled under reduced pressure to remove the solvent, and the product was purified by washing with acetonitrile and drying. Thus, a durable smoke-suppressing flame retardant was obtained, and the yield was 78.6%.

[0046] In a three-necked flask equipped with a thermometer, a magnetic stirrer and a spherical condenser, 18.44 g of cyanuric chloride was added to 200 mL of acetone as a solvent. The mixture was heated and stirred under nitrogen until cyanuric chloride was completely dissolved, and the temperature was raised to the reflux temperature. Separately, 2.82 g of the boron spiro ring was dissolved in acetone and added to the reaction device. The reaction was carried out for 12 h. 14.7 g of phosphoric acid was dissolved in tetrahydrofuran and slowly added to the reaction device. The temperature was raised to 110°C, and the reaction was carried out for 8 h. During the reaction, the pH of the reaction system was adjusted to 6.9 using ammonia water. Subsequently, the liquid in the reaction device was distilled under reduced pressure to remove the solvent, and the product was purified by washing with acetonitrile and drying. Thus, a durable smoke-suppressing flame retardant was obtained, and the yield was 78.6%.

[0047] The reaction device in each stage was a conventional reactor used in actual operation, such as a three-necked flask, and thus a detailed description thereof is omitted.

[0048] Comparative Example 2: In a 250 mL three-necked flask equipped with an oil-water separator and a spherical condenser, 23.4 g of boric acid and 22.4 g of pentaerythritol were added, and 40 mL of n-hexane was added, and the reaction was heated and stirred under reflux until no water was generated, and the reaction was terminated. The solvent toluene was removed by liquid separation, and a transparent viscous liquid was obtained, which was washed with tetrahydrofuran until it was colorless and transparent, and was dried at 45°C under vacuum to obtain 28.6 g of a colorless transparent viscous liquid, with a yield of about 62.4%, and the obtained boron spiro ring was reserved.

[0049] In a three-necked flask equipped with a thermometer, a magnetic stirrer and a spherical condenser, 18.44 g of cyanuric chloride was added to 200 mL of tetrahydrofuran as a solvent, and the cyanuric chloride was completely dissolved under stirring under the protection of nitrogen. Separately, 2.82 g of boron spiro ring was dissolved in tetrahydrofuran and added to the reaction device, and the reaction was carried out for 9 h. 14.7 g of phosphoric acid was dissolved in tetrahydrofuran and diluted, and was slowly added dropwise into the reaction device, and the temperature was increased to 120°C, and the reaction was carried out for 5 h, and during the whole reaction process, the pH of the reaction system was adjusted to 7 by using ammonia water. Subsequently, the liquid in the reaction device was distilled under reduced pressure to remove the solvent, and was washed and purified with dimethyl sulfoxide and dried, and the yield of the durable smoke suppression flame retardant was 30%.

[0050] As shown in Figure 1 , the left picture is a scanning electron microscope photograph of a pure cotton fabric, the middle picture is a scanning electron microscope photograph of the cotton fabric after being treated with the flame retardant, and the right picture is a scanning electron microscope photograph of the carbon residue after the treated cotton fabric is burned. As can be seen from the figure, the organization structure of the cotton fabric is regular, the fiber surface is smooth, there are natural twists and cracks, and the microfibril structure can be observed after magnification. After finishing, the organization structure of the fabric is regular and orderly, there is a film-like substance on the fiber surface, and there are crystalline substances attached to the outer layer, and after magnification, it can be observed that the original microfibril structure of the fiber is covered, indicating that the flame retardant has been successfully finished on the surface of the cotton fabric. After burning, the finished fabric retains the complete and continuous carbon residue, and the fabric weaving structure is not damaged, and there is no obvious crystallization and air chamber on the surface of the carbon residue. The pure cotton fabric is almost left without carbon residue after burning. The results show that the use of the flame retardant significantly improves the carbonization performance of the fabric.

[0051] As shown in Figure 2 , it is the limiting oxygen index test result of the cotton fabric finished with the flame retardant synthesized in Example 1. The LOI value of the fabric without finishing is about 18.0%, which is extremely flammable in the atmospheric environment. When the weight gain rate after finishing is 9.8%, the LOI value of the fabric increases to 31.5%, which can achieve self-extinguishing in air, reaching the standard of flame-retardant fabric. Continue to increase the concentration of the flame retardant, the LOI value of the fabric continues to increase, and when the weight gain rate reaches 29.9%, the LOI value of the fabric reaches 49.0%. The flame retardant involved in the present application has good flame-retardant effect on cotton fabric, and the addition amount is small, and the flame-retardant efficiency is high.

[0052] As Figure 3 shown, are the results of the limiting oxygen index test and scanning electron microscope photos of the washed flame-retardant cotton fabric with different weight gain rates. The synthetic flame-retardant finished cotton fabric was placed in a 250ml conical flask, then 200ml of water containing 0.15wt% was added, and the conical flask was placed in a shaking water bath at 80rpm, the temperature was 48℃, 45min was defined as 5 washing cycles. When the washing cycle was 10 times, compared with the un-washed flame-retardant finished cotton fabric, the LOI value decreased. This is because some flame retardants are agglomerated on the surface of the fiber and do not react with the cotton. After washing, these agglomerates disappear, resulting in a decrease in the flame retardant performance of the synthetic flame-retardant finished cotton fabric. After 50 washing cycles, the LOI value of the synthetic flame-retardant finished cotton fabric showed no significant difference from that of 10 washes. Respectively decreased by 2.4%, 4.5% and 3.0%. The flame retardant involved in the present application has better flame retardant durability for cotton fabric.

[0053] Those skilled in the art will appreciate that the experimental examples shown herein are intended to help the reader understand the principles of the present application, and it should be understood that the scope of protection of the present application is not limited to such specific statements and examples. Those skilled in the art can make various other aspect modifications without departing from the essence of the present application according to the technical inspiration disclosed in the present application, and these modifications are still within the scope of protection of the present application.

Claims

1. A durable smoke-suppressing flame retardant characterized by, The chemical structure of the durable smoke-suppressing flame retardant is as follows:

2. A process for the preparation of a durable smoke suppressing flame retardant as claimed in claim 1, wherein, The synthesis steps are as follows: (1) Boric acid and pentaerythritol are used to synthesize boron spiro ring in an organic solvent, which is prepared for use; (2) Tricyanuric chloride and an organic solvent are added into a reaction device, nitrogen is introduced, and heating is performed to the reflux temperature; (3) The boron spiro ring synthesized in step (1) is dissolved in an organic solvent, and then added into the reaction device in step (2) to perform reaction; (4) Phosphoric acid is dissolved and diluted in an organic solvent, and then added dropwise into the reaction device to perform reaction, and ammonia water is used to adjust the pH of the reaction system to 6.5-7.0 during the whole reaction process; (5) The product obtained in step (4) is subjected to vacuum distillation to remove the solvent, and then washed, purified and dried, and the durable smoke-suppressing flame retardant is obtained.

3. A process for the preparation of a durable smoke suppressing flame retardant according to claim 2, characterized in that, In step (1), the molar ratio of boric acid to pentaerythritol is 2-2.3:1; and the organic solvent is any one of toluene, n-hexane, cyclohexane, dimethylbenzene and benzene.

4. The method of claim 2, wherein the method is characterized by, In step (1), boric acid and pentaerythritol are heated to perform reaction, and stirring reflux is performed until no water is generated, and then the reaction is ended; the organic solvent is removed by liquid separation, and the obtained transparent viscous liquid is washed with tetrahydrofuran until it is colorless and transparent, and then vacuum dried.

5. The method for preparing a durable smoke-suppressing flame retardant according to claim 2, characterized in that, In step (2), the reflux temperature is the boiling point temperature of the mixed liquid in the reaction device, and the organic solvent is any one of tetrahydrofuran, ethanol and acetone.

6. A process for the preparation of a durable smoke suppressing flame retardant according to claim 2, characterized by, In step (3), the organic solvent is tetrahydrofuran, ethanol or acetone, and the reaction time is 8-12 h.

7. The method for preparing a durable smoke-suppressing flame retardant according to claim 2, characterized in that, In steps (2) and (3), the molar ratio of tricyanuric chloride, boron spiro ring and phosphoric acid used is 1:3:

3.

8. The method for preparing a durable smoke-suppressing flame retardant according to claim 2, characterized in that, In step (4), the organic solvent is tetrahydrofuran, ethanol or acetone, and the dropwise speed is 1-10 drops / min.

9. The method of claim 8, wherein the method is characterized by, The heating temperature is 110-130℃, and the reaction time is 4-8 h.

10. A process for the preparation of a durable smoke suppressing flame retardant according to claim 2, characterized by, In step (5), the solvent used for washing and purification is at least one of tetrahydrofuran, dimethyl sulfoxide and acetonitrile.

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