Preparation of boron-containing chitosan-based monocomponent intumescent flame retardant and its application in rigid polyurethane foam
A single-component intumescent flame retardant based on boron and phosphorus synergy was synthesized by hydrothermal method, which solved the problem of flammability of rigid polyurethane foam, achieved high flame retardant effect and improved limiting oxygen index, and the preparation process is simple and the raw materials are widely available.
Patent Information
- Application Number
- CN202410013010.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-04
- Publication Date
- 2026-08-25
- Estimated Expiration
- 2044-01-04
AI Technical Summary
Rigid polyurethane foam has a low limiting oxygen index, burns quickly, and releases a large amount of heat and toxic gases when burning. Existing flame retardants are insufficient in improving flame retardant efficiency.
A single-component, intumescent flame retardant based on boron and phosphorus synergy was synthesized using a hydrothermal one-pot method. Using chitosan, self-made boron phosphate, and melamine as raw materials, the flame retardant was prepared by rationally designing the reaction route. It integrates acid, carbon, and gas sources and controls the boron-to-phosphorus ratio to achieve synergistic effects.
The prepared flame retardant exhibits highly efficient flame retardant effect in rigid polyurethane foam, achieving a flame retardant rating of UL94 V-0, increasing the limiting oxygen index to 28%, and exhibiting high residual carbon content, thus significantly improving the flame retardant performance of polyurethane foam.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of biomass-based polymer flame retardant technology, specifically relating to a boron-phosphorus synergistic chitosan-based single-component intumescent flame retardant, its preparation method, and its application in rigid polyurethane foam. Background Technology
[0002] Rigid polyurethane foam is a novel synthetic material with thermal insulation and waterproofing functions. It possesses numerous advantages, including sound insulation, shock absorption, electrical insulation, heat resistance, cold resistance, solvent resistance, low density, and good abrasion resistance. It has been widely used in building exterior wall insulation, integrated roof waterproofing and insulation, cold storage insulation, pipe insulation materials, building panels, refrigerated truck and cold storage insulation materials, and automotive roofs, among many other fields. However, rigid polyurethane foam has a very low limiting oxygen index (approximately 16%), making it flammable upon contact with fire, and the flame spreads extremely rapidly. During combustion, it releases a large amount of heat, smoke, and toxic gases, seriously threatening people's property and lives. Therefore, efficient flame-retardant modification of rigid polyurethane foam has become a current research focus and hot topic.
[0003] Currently, flame retardants used in rigid polyurethane foam are mainly classified into two categories according to their application methods: additive flame retardants and reactive flame retardants. Additive flame retardants mainly include halogen-based, phosphorus-based, nitrogen-based, boron-based, inorganic hydroxide, and intumescent flame retardants; reactive flame retardants mainly include phosphorus- and nitrogen-containing polyols and boron-containing polyols.
[0004] Chitosan is produced by removing some acetyl groups from chitin. It is the only natural alkaline polysaccharide. Because its molecular structure contains abundant active hydroxyl and amino groups, it can be used as a carbon source and gas source for intumescent flame retardants. Furthermore, these active functional groups can be used to further modify the molecular chain by introducing flame retardant elements such as B, P, and N, thereby improving its flame retardant efficiency.
[0005] Boron phosphate (BP) is a white, microcrystalline solid acid characterized by its insolubility in water and high thermal stability. The three-dimensional structure of BP contains a large amount of... The acid sites and Lewis acid sites are formed by tetrahedral phosphorus-oxygen and tetrahedral boron-oxygen sharing oxygen atoms. By controlling the molar ratio of elements B and P (B / P value), the flame-retardant synergy between B and P can be fully utilized, and more active acid sites can be obtained for further chemical modification, introducing more flame-retardant elements and improving its flame-retardant performance.
[0006] This invention utilizes chitosan, self-made boron phosphate, and melamine as raw materials, and through a rationally designed reaction route, prepares a boron-phosphorus synergistic chitosan-based single-component intumescent flame retardant using a hydrothermal one-pot method. Summary of the Invention
[0007] This invention provides a method for preparing a boron-phosphorus synergistic chitosan-based single-component intumescent flame retardant and its application in rigid polyurethane foam. The synthesis of this flame retardant is completed in the aqueous phase, the preparation process is simple and the raw materials are widely available. The flame retardant integrates an acid source (boron phosphate), a carbon source (chitosan), and a gas source (melamine), and the boron-phosphorus ratio and the ratio of the three sources are easily adjustable. It has good thermal stability, good compatibility with RPUF, and high flame retardant efficiency, and has broad application prospects in flame-retardant RPUF.
[0008] To achieve the above objectives, the present invention adopts the following technical solution:
[0009] A method for preparing a boron-containing chitosan-based single-component intumescent flame retardant includes the following steps:
[0010] (1) Weigh an appropriate amount of chitosan and dissolve it in a dilute acid solution of a certain concentration. Obtain a chitosan solution by magnetic stirring and ultrasonic vibration.
[0011] (2) Boric acid and phosphoric acid are stirred and mixed evenly at a certain molar ratio, and then calcined in a muffle furnace at a certain temperature for a certain time to obtain boron phosphate blocks. After being ball-milled into powder, deionized water is added to prepare a 4% boron phosphate solution.
[0012] (3) Add a certain amount of melamine to an appropriate amount of deionized water and stir magnetically at a certain temperature to prepare a melamine solution;
[0013] (4) Add a certain amount of boron phosphate solution from step (2) to the melamine solution from step (3) and stir the reaction at a certain temperature for a certain time to obtain a boron phosphate modified melamine solution.
[0014] (5) Add the chitosan solution obtained in step (1) to the boron phosphate modified melamine solution in step (4), stir and react for a certain time at a certain temperature to obtain a boron phosphate modified melamine turbid liquid of chitosan. After cooling and standing for aging, vacuum filter the filtered product, dry, crush and sieve it to obtain a white powder product, which is a boron-containing chitosan-based single-component intumescent flame retardant.
[0015] Further, the dilute acid in step (1) is one or more of acetic acid, hydrochloric acid, and citric acid, and the mass concentration of the dilute acid solution is 1 wt%; the mass ratio of the dilute acid to chitosan is 3:10-3:5.
[0016] Furthermore, in step (2), the molar ratio of phosphoric acid and boric acid is 1:1-1:3, the calcination temperature is 150-250℃, and the calcination time is 4h-12h.
[0017] Furthermore, in step (3), the amount of melamine used is (0.03-0.09mol) / 10g chitosan, the amount of deionized water used is 50mL / g melamine, and the dissolution temperature is 80-95℃.
[0018] Furthermore, in step (4), the amount of boron phosphate solution used is 200mL-500mL / 10g chitosan, the reaction temperature is 70-95℃, the reaction time is 2-6h, and the stirring rate is 300-500rpm.
[0019] Furthermore, in step (5), the reaction temperature is 70-95℃, the reaction time is 6-18h, the stirring rate is 300-500rpm, the aging time is 6-24h, the drying temperature is 70-90℃, and the drying time is 8-24h.
[0020] Add the boron-phosphorus synergistic chitosan-based single-component intumescent flame retardant prepared by any one of steps (1)-(5) to rigid polyurethane foam.
[0021] The application of the above-mentioned boron-phosphorus synergistic chitosan-based single-component intumescent flame retardant in rigid polyurethane foam (RPUF) includes the following steps: 100 parts of polyether polyol (LY4110), 2 parts of triethylenediamine catalyst, 2 parts of silicone oil foam stabilizer, 2 parts of blowing agent, and flame retardant are mixed and stirred evenly to obtain mixed component A. 145 parts of polyaryl polymethylene isocyanate (PM200) are weighed as component B. Then, component B is poured into component A and stirred quickly for 10 seconds with a manual stirrer. The mixture is poured into a mold and allowed to foam freely until it stops. The mold is then placed in an oven and cured at 60°C for 24 hours. Finally, the mold is demolded to obtain rigid polyurethane foam containing 10% to 20% flame retardant.
[0022] The significant advantages of this invention are:
[0023] (1) The boron-containing chitosan-based flame retardant of the present invention uses natural high molecular weight chitosan, which is abundant in nature, as the main raw material. The raw material source is wide and green and environmentally friendly. The synthesis of the flame retardant is completed in the aqueous phase. The preparation process is simple and easy to realize industrial production.
[0024] (2) The flame retardant prepared by the present invention uses chitosan as a carbon source, hydroxyl boron phosphate as an acid source, and melamine as a gas source. The ratio and composition of these three sources are easy to control, and by controlling the boron-phosphorus ratio, the flame retardant synergistic effect between B and P can be fully utilized, which greatly improves its flame retardant efficiency.
[0025] (3) The boron-containing chitosan-based flame retardant of the present invention shows good flame retardant effect in RPUF. When the amount added to RPUF is 15wt%, the flame retardant rating can reach UL94 V-0 and the LOI reaches 28%. Attached Figure Description
[0026] Figure 1 FT-IR images of chitosan, melamine, and the boron-containing chitosan-based single-component intumescent flame retardant prepared in Example 1;
[0027] Figure 2 SEM image of the char layer after combustion of the flame-retardant sample prepared in Example 1;
[0028] Figure 3 SEM image of the char layer after combustion of the flame-retardant sample prepared in Example 2;
[0029] Figure 4 To compare the SEM images of the char layer after combustion of the flame-retardant sample prepared in Application Example 1.
[0030] Figure 5 SEM images of the carbon layer after combustion of the pure RPUF combustion sample prepared in Application Example 2 are shown for comparison.
[0031] Figure 6 This is a synthetic route diagram for boron phosphate.
[0032] Figure 7 This is a synthetic route diagram for boron-containing chitosan-based intumescent flame retardants. Detailed Implementation
[0033] A synthetic route for a boron-containing chitosan-based single-component intumescent flame retardant includes the following steps:
[0034] The synthetic route for boron phosphate is as follows: Figure 6 As shown.
[0035] The synthetic route of boron-containing chitosan-based intumescent flame retardants is as follows: Figure 7 As shown.
[0036] Example 1
[0037] Weigh 3.6 g (0.03 mol) of acetic acid into a beaker, add deionized water to prepare a 1 wt% acetic acid solution, add 10 g of chitosan to the acetic acid solution, and stir magnetically until the chitosan is completely dissolved. Keep warm at 60°C for later use. Mix phosphoric acid and boric acid in a molar ratio of 1:1.2 at 120°C until homogeneous, then calcine in a muffle furnace at 150°C for 4 hours to obtain boron phosphate. Grind the boron phosphate into powder, add deionized water to prepare a 4% boron phosphate solution for later use. Weigh 8.8 g (0.07 mol) of melamine and pour it into a three-necked flask equipped with a magnetic stirrer, reflux condenser, and 450 mL of deionized water. Under stirring at 300 rpm, raise the temperature of the water bath to 80°C, and slowly add 308 mL of the boron phosphate solution dropwise to the three-necked flask containing the melamine solution using a separatory funnel. React for 4 hours. The water bath was then heated to 85°C, and chitosan solution was slowly added dropwise to a three-necked flask with stirring at 500 rpm for 12 hours. After the reaction suspension was aged for 12 hours, it was vacuum filtered. The filtered product was dried in an oven at 60°C for 12 hours, crushed, and passed through a 200-mesh sieve to obtain boron-containing chitosan-based intumescent flame retardant CS-BP-MEL-1.
[0038] Example 2
[0039] Weigh 5.7 g (0.03 mol) of citric acid into a beaker, add deionized water to prepare a 1 wt% citric acid solution, add 10 g of chitosan to the citric acid solution, and stir magnetically until the chitosan is completely dissolved. Keep warm at 60°C for later use. Mix phosphoric acid and boric acid in a 1:1.5 ratio at 120°C until homogeneous, then calcine in a muffle furnace at 200°C for 8 hours to obtain boron phosphate. Grind the boron phosphate into powder, add deionized water to prepare a 4% boron phosphate solution for later use. Weigh 6.3 g (0.05 mol) of melamine and pour it into a three-necked flask equipped with a magnetic stirrer, reflux condenser, and 320 ml of water. Under stirring at 300 rpm, raise the temperature of the water bath to 80°C. Measure 462 mL of the boron phosphate solution and slowly add it dropwise to the three-necked flask containing the melamine solution using a separatory funnel. React for 4 hours. The water bath was then heated to 85°C, and chitosan solution was slowly added dropwise to a three-necked flask with stirring at 500 rpm. The reaction was carried out for 12 hours. After the reaction suspension was aged for 12 hours, it was vacuum filtered. The filtered product was dried in an oven at 60°C for 12 hours, crushed, and passed through a 200-mesh sieve to obtain boron-containing chitosan-based intumescent flame retardant CS-BP-MEL-2.
[0040] Comparison Example 1
[0041] An appropriate amount of 85% phosphoric acid was added to a three-necked flask equipped with a reflux condenser. The mixture was stirred and heated to about 50°C. 10g of chitosan was added, and the mixture was magnetically stirred at 120°C for 10 hours to allow the chitosan to undergo an esterification reaction to generate chitosan phosphate ester. The mixture was then cooled, and 100g of a melamine-ethanol mixture was added to continue the reaction. A white precipitate gradually formed in the system. The reaction was stopped after another 3 hours. The reaction suspension was allowed to stand for 12 hours, then vacuum filtered. The filtered product was dried in a 60°C oven for 12 hours, crushed, and passed through a 200-mesh sieve to obtain the chitosan-based intumescent flame retardant CS-P-MEL.
[0042] Application Example 1
[0043] The formulation of a CS-BP-MEL-1 / rigid polyurethane foam composite material is as follows: 100 parts of polyether polyol (LY4110), 2 parts of triethylenediamine catalyst, 2 parts of silicone oil foam stabilizer, 2 parts of foaming agent, and 15 wt% boron-containing chitosan-based flame retardant are mixed and stirred evenly to obtain mixed component A. 145 parts of polyaryl polymethylene isocyanate (PM200) are weighed as component B. Then, component B is poured into component A and stirred rapidly with a mechanical stirrer for 10 seconds. The mixture is poured into a plastic mold and allowed to foam freely until it stops. The mold is then placed in an oven and cured at 60°C for 24 hours. Finally, the mold is demolded to obtain a CS-BP-MEL / rigid polyurethane foam composite material. Standard vertical burning (UL-94), limiting oxygen index (LOI) specimens and standard compressive strength specimens are cut and prepared for testing.
[0044] Application Example 2
[0045] The formulation of a CS-BP-MEL-2 / rigid polyurethane foam composite material is as follows: 100 parts of polyether polyol (LY4110), 2 parts of triethylenediamine catalyst, 2 parts of silicone oil foam stabilizer, 2 parts of foaming agent, and 15 wt% boron-containing chitosan-based flame retardant are mixed and stirred evenly to obtain mixed component A. 145 parts of polyaryl polymethylene isocyanate (PM200) are weighed as component B. Then, component B is poured into component A and stirred rapidly with a mechanical stirrer for 10 seconds. The mixture is poured into a plastic mold and allowed to foam freely until it stops. The mold is then placed in an oven and cured at 60°C for 24 hours. Finally, the mold is demolded to obtain a CS-BP-MEL / rigid polyurethane foam composite material. Standard vertical burning (UL-94), limiting oxygen index (LOI) specimens and standard compressive strength specimens are cut and prepared for testing.
[0046] Comparison Application Example 1
[0047] A formulation for a CS-P-MEL / rigid polyurethane foam composite material is as follows: 100 parts of polyether polyol (LY4110), 2 parts of triethylenediamine catalyst, 2 parts of silicone oil foam stabilizer, 2 parts of blowing agent, and 15 wt% chitosan-based intumescent flame retardant are mixed and stirred evenly to obtain component A. 145 parts of polyaryl polymethylene isocyanate (PM200) are weighed as component B. Then, component B is poured into component A, and the mixture is rapidly stirred for 10 seconds using a mechanical stirrer. The mixture is then poured into a plastic mold and allowed to foam freely until it stops. The mold is then placed in an oven and cured at 60°C for 24 hours. Finally, the mixture is demolded to obtain a CS-P-MEL / rigid polyurethane foam composite material. Standard vertical burning (UL-94), limiting oxygen index (LOI), and standard compressive strength specimens are cut and prepared for testing.
[0048] Compare with application example 2 (pure sample)
[0049] A formulation for a rigid polyurethane foam (control group) is as follows: 100 parts of polyether polyol (LY4110), 2 parts of triethylenediamine catalyst, 2 parts of silicone oil foam stabilizer, and 2 parts of blowing agent are mixed and stirred evenly to obtain component A. 145 parts of polyaryl polymethylene isocyanate (PM200) are weighed as component B. Then, component B is poured into component A, and the mixture is quickly stirred for 10 seconds with a manual stirrer. The mixture is then poured into a mold and allowed to foam freely until it stops. The mold is then placed in an oven and cured at 60°C for 24 hours. Finally, the rigid polyurethane foam is demolded to obtain the final product. Standard vertical burning (UL-94), limiting oxygen index (LOI), and standard compressive strength specimens are cut and prepared for testing.
[0050] The flame-retardant rigid polyurethane foam composite material prepared above with vertical burning specimens, limiting oxygen index specimens, and standard compressive strength specimens were tested for combustion performance and mechanical properties in accordance with GB / T8333-2022, ASTM D2863, and GB / T8813-2008. The test results are shown in Table 1.
[0051] Table 1 Combustion performance and mechanical properties
[0052]
[0053] The test results show that, compared to Application Example 2 (pure RPUF), the vertical burning test rating is NR, the LOI value is 16%, and the residual carbon rate is only 15.4%. Application Example 2, compared to Application Examples 1 and 2, achieves a UL94 V-0 rating in the vertical burning test, with an LOI value increased to 26.5%, a residual carbon rate of 24% after complete combustion at 800℃, and a compressive strength of 168 kPa for the modified rigid polyurethane foam. Application Example 1, compared to Application Examples 1 and 2, achieves a UL94 V-0 rating in the vertical burning test, with an LOI value increased to 28%, a residual carbon rate of 27.5% after complete combustion at 800℃, and a compressive strength of 173 kPa for the modified rigid polyurethane foam. Therefore, the flame retardant prepared in this invention has higher flame retardant efficiency.
[0054] Figure 1 The FT-IR spectra of chitosan, melamine, and the boron-containing chitosan-based single-component intumescent flame retardant prepared in Example 1 are shown in the CS-BP-MEL spectra. At 1014 cm⁻¹... -1 A vibrational absorption peak for POC appears nearby, at 1336 cm⁻¹. -1 The presence of a vibrational absorption peak of BOC nearby indicates that boron phosphate has been successfully modified into the chitosan structure, and a peak at 1103 cm⁻¹ is also observed. -1 A peak for primary amine groups was observed nearby, at 1518 cm⁻¹. -1 A peak for primary amine salts appeared at 1658 cm⁻¹. -1 The presence of a characteristic C=N peak at the position confirms that melamine was successfully modified onto boron phosphate. In summary, infrared structural analysis confirms the successful synthesis of the flame retardant CS-BP-MEL.
[0055] Figure 2 and Figure 3 The images show SEM images of the char layer after combustion of the flame retardants prepared in Examples 1 and 2. The SEM images show that the char layer is dense and compact, which can effectively isolate heat transfer and achieve a good flame retardant effect.
[0056] Figure 4 To compare the SEM images of the char layer after combustion of the combustion sample prepared in Application Example 1, it can be seen from the SEM images that the char layer has poor density after complete combustion, which is not conducive to heat and oxygen insulation and has poor flame retardant effect.
[0057] Figure 5 To compare the SEM images of the char layer after combustion of the pure RPUF combustion sample prepared in Application Example 2, it can be seen from the SEM images that the char layer after complete combustion of pure RPUF is loose and porous, which is not conducive to heat and oxygen insulation and has almost no flame retardant effect.
Claims
1. A method for preparing a boron-containing chitosan-based single-component intumescent flame retardant, characterized in that: Includes the following steps: (1) Chitosan is dissolved in a dilute acid solution and a chitosan solution is obtained by magnetic stirring and ultrasonic vibration; (2) Mix boric acid and phosphoric acid evenly, then calcine them in a muffle furnace to obtain boron phosphate blocks, ball mill them into powder, and add deionized water to prepare a 4% boron phosphate solution; (3) Add melamine to an appropriate amount of deionized water, stir magnetically to dissolve, and prepare a melamine solution; (4) Add the boron phosphate solution from step (2) to the melamine solution from step (3), and stir the reaction at a certain temperature for a certain time to obtain the boron phosphate modified melamine solution; (5) Add the chitosan solution obtained in step (1) to the boron phosphate modified melamine solution in step (4), stir and react for a certain time at a certain temperature to obtain a boron phosphate modified melamine turbid liquid. After cooling and standing for aging, vacuum filter the filtered product, dry, crush and sieve it to obtain a white powder product, which is a boron-containing chitosan-based single-component intumescent flame retardant.
2. The preparation method according to claim 1, characterized in that: The dilute acid mentioned in step (1) is one or more of acetic acid, hydrochloric acid, and citric acid, and the mass concentration of the dilute acid solution is 1 wt%; the mass ratio of the dilute acid to chitosan is 3:10-3:
5.
3. The preparation method according to claim 1, characterized in that: The molar ratio of phosphoric acid and boric acid in step (2) is 1:1-1:3, the calcination temperature is 150-250℃, and the calcination time is 4h-12h.
4. The preparation method according to claim 1, characterized in that: In step (3), the amount of melamine used is 0.03-0.09 mol / 10 g chitosan, the amount of deionized water used is 50 mL / g melamine, and the dissolution temperature is 80-95℃.
5. The preparation method according to claim 1, characterized in that: In step (4), the amount of boron phosphate solution used is 200mL-500mL / 10g chitosan, the temperature of the stirring reaction is 70-95℃, the reaction time is 2-6h, and the stirring rate is 300-500 rpm.
6. The preparation method according to claim 1, characterized in that: The stirring reaction temperature in step (5) is 70-95℃, the reaction time is 6-18 h, the stirring rate is 300-500 rpm, the aging time is 6-24 h, the drying temperature is 70-90℃, and the drying time is 8-24 h.
7. A boron-containing chitosan-based single-component intumescent flame retardant prepared by the preparation method according to any one of claims 1-6.
8. The application of the boron-containing chitosan-based single-component intumescent flame retardant as described in claim 7 in the preparation of rigid polyurethane foam, characterized in that, Specifically, the following steps are included: (1) Mix 100 parts of polyether polyol, 2 parts of triethylenediamine catalyst, 2 parts of silicone oil foam stabilizer, 2 parts of foaming agent, and the boron-containing chitosan-based single-component intumescent flame retardant as described in claim 7 and stir until uniform to obtain component A; (2) Weigh 145 parts of polyaryl polymethylene isocyanate as component B; then pour component B into component A, stir quickly for 10 seconds with a manual stirrer, pour into a mold and let it foam freely until it stops, then put the mold into an oven and cure at 60°C for 24 hours, and finally demold to obtain rigid polyurethane foam containing 10% to 20% single-component intumescent flame retardant.