Bio-based polyurethane flame-retardant protective material and application thereof in safety helmet

Abstract

The invention discloses a bio-based polyurethane flame-retardant protective material and application thereof in safety helmets, and belongs to the technical field of safety helmet materials.The bio-based polyurethane flame-retardant protective material is prepared from, by weight, 95-110 parts of modified bio-based PN flame-retardant polyester diol, 10-20 parts of a chain extender, 0.8-1.5 parts of a surfactant and 2-6 parts of a water foaming agent, 60 to 90 parts of diisocyanate, 0.1 to 0.5 part of an organic tin catalyst and 0.2 to 0.5 part of an organic amine catalyst; the modified bio-based PN flame-retardant polyester diol is prepared by grafting PN flame-retardant components including melamine, diethyl phenyl phosphate and benzotriazole to a biological matrix castor oil; the bio-based polyurethane flame-retardant protective material provided by the invention has excellent flame retardancy and impact resistance, and can be used in the preparation of safety helmets.

Description

Technical Field

[0001] The present invention relates to the technical field of helmet materials, in particular to a bio-based polyurethane flame retardant protective material and application thereof in helmets. Background Art

[0002] In high-risk work environments like petrochemicals, metallurgy, and firefighting, where open flames, high temperatures, or molten material splashing are common, hard hats are essential protective equipment, protecting workers' heads and preventing secondary injuries. Hard hats are often made of rigid polyurethane foam, a polymer material made from long-chain polyols and polyisocyanates repeatedly linked by urethane segments. Rigid polyurethane foam offers excellent and tunable mechanical properties, is lightweight, and its porous elasticity imparts excellent impact resistance. Traditional polyurethane foam primarily relies on petroleum-based feedstock, but increasingly scarce petroleum resources have given rise to the development of biomass-based polyurethane foam. Rigid polyurethane foam is also highly flammable due to its rich content of elements such as C, H, and O. Its porous structure creates airflow channels, further promoting combustion and potentially causing more serious fires. Therefore, the development of biomass-based polyurethane materials with flame retardancy is crucial.

[0003] Researchers generally add flame retardants of elements such as N, P, and B as additives to polyurethane foam, which greatly improves the flame retardant properties. However, the flame retardant properties are closely related to the amount added. Increasing the amount added can effectively improve the flame retardancy, but its incompatibility with polyurethane will also cause it to precipitate, making the polyurethane material brittle and unable to be used in safety helmets. At the same time, the flame retardant components will also migrate and lose as the material is used, thereby losing the flame retardant properties. Summary of the Invention

[0004] To overcome the shortcomings of the above-mentioned prior art, the present invention provides a bio-based polyurethane flame-retardant protective material and its application in safety helmets. The bio-based polyurethane flame-retardant protective material is prepared from a rigid polyurethane foam comprising a modified bio-based PN flame-retardant polyester diol, a chain extender, a surfactant, a water-based foaming agent, a diisocyanate, an organotin catalyst, and an organoamine catalyst. Castor oil, as a bio-based material, is environmentally friendly. The modified bio-based PN flame-retardant polydiol is prepared by grafting flame-retardant molecular structures containing N and P elements—melamine, diethyl phenyl phosphate, and benzotriazole—onto the bio-based castor oil. The combustion of the phosphate groups not only decomposes a viscous semi-solid substance that coats the polyurethane surface, but also promotes dehydration and carbonization of the polyurethane, isolating it from oxygen infiltration and heat transfer. Simultaneously, the nitrogen-containing groups decompose upon heating to release non-flammable gases such as nitrogen, nitrogen oxides, and water vapor, which not only dilute the oxygen concentration but also decompose to remove energy. The PN catalyst acts synergistically to improve the flame retardant properties of the polyurethane. Furthermore, the flame retardant groups are grafted into the polyurethane chain, making it less susceptible to flame retardant component loss.

[0005] The purpose of the present invention is to provide a bio-based polyurethane flame retardant protective material and its use in a safety helmet.

[0006] The present invention is achieved through the following technical solutions: A bio-based polyurethane flame-retardant protective material, comprising the following components by weight: 95-110 parts of a modified bio-based PN flame-retardant polyester diol, 10-20 parts of a chain extender, 0.8-1.5 parts of a surfactant, 2-6 parts of a water-blowing agent, 60-90 parts of a diisocyanate, 0.1-0.5 parts of an organotin catalyst, and 0.2-0.5 parts of an organic amine catalyst; the modified bio-based PN flame-retardant polyester diol has a structure as shown in Formula 1: Formula 1.

[0007] In a specific embodiment, the chain extender is one of ethylene glycol, propylene glycol, and butanediol; In a specific embodiment, the surfactant is an organosilicon foam stabilizer AK8805; In a specific embodiment, the diisocyanate is 4,4'-methylenebis(phenyl isocyanate); In a specific embodiment, the organotin catalyst is dibutyltin dilaurate; In a specific embodiment, the organic amine catalyst is triethylenediamine; In a specific embodiment, the modified bio-based PN flame retardant polyester diol is homemade, and the preparation steps are as follows: S1. Under a nitrogen atmosphere, melamine, 5-bromo-1H-benzotriazole, an inorganic base, and the ligand Ruphos were dissolved in toluene; Pd2(dba)3 was added as a catalyst, the temperature was raised to 100-110°C, and the reaction was stirred for 18-24 hours. The reaction was then cooled, purified by column chromatography, concentrated, and dried to obtain product A. S2. Under a nitrogen atmosphere, product A, diethyl 4-chlorophenyl phosphate, a base, and the ligand Xphos were dissolved in toluene; Pd(OAc)2 was added as a catalyst, the temperature was raised to 100-110°C, and the reaction was stirred for 24-36 hours; the reaction was cooled, purified by column chromatography, concentrated, and dried to obtain product B; S3. Under a nitrogen atmosphere, product B, 4-bromobenzoic acid, an inorganic base, and the ligand Ruphos were dissolved in toluene; Pd2(dba)3 was added as a catalyst, the temperature was raised to 95-115 ° C, the reaction was stirred for 20-24 hours, cooled, purified by column chromatography, concentrated, and dried to obtain product C; S4. Dissolve product C in anhydrous dichloromethane, cool to 0°C, and sequentially add an organic base and di-tert-butyl dicarbonate; warm to room temperature and stir for 10-16 hours; wash the reaction solution with 1M HCl, and concentrate and dry the organic phase to obtain product D; S5. Dissolve product D in anhydrous dichloromethane, cool to 0°C, add oxalyl chloride dropwise, and then add 1-2 drops of DMF dropwise; warm to room temperature and stir to react for 1-3 hours; concentrate the reaction solution and dry to obtain crude product E; S6. Product E was dissolved in anhydrous dichloromethane, cooled to 0°C in an ice bath, and triethylamine was added. Trimethylsilyl trifluoromethanesulfonate was then slowly added dropwise and stirred for 0.5-2 hours. Saturated NaHCO3 solution was added, and the organic phase was concentrated, purified by column chromatography, concentrated, and dried to obtain product F. S7. Dissolve the bio-based polyol castor oil in anhydrous dichloromethane, cool to 0°C, and add triethylamine. Then, dropwise add F solution dissolved in a small amount of dichloromethane and react at room temperature for 1-4 hours. Wash the reaction solution with 1M HCl and saturated NaHCO3 solution, sequentially. The organic phase is concentrated, separated, and purified to obtain the modified bio-based PN flame-retardant diol. S8. Esterification and polycondensation The modified bio-based PN flame-retardant diol was dissolved in anhydrous dichloromethane, cooled to 0°C in an ice bath, triethylamine was added, and then a solution of malonyl chloride dissolved in a small amount of dichloromethane was added dropwise, and stirred at room temperature for 4-10 hours. 1M HCl and saturated NaHCO3 solution were added sequentially to wash the reaction solution until neutral. The organic phase was concentrated and cold methanol was added dropwise to precipitate the polymer. The polymer was filtered and dried to obtain a modified bio-based PN flame-retardant polyester diol with a hydroxyl value of 28.05-56.1 mg KOH / g.

[0008] In a specific embodiment, in step S1, the amount of 5-bromo-1H-benzotriazole is 0.95-1 times the molar amount of melamine; the inorganic base is potassium phosphate or cesium carbonate, and the amount is 3-5 times the molar amount of melamine; the amount of the ligand Ruphos is 0.1 wt% of the melamine; In a specific embodiment, in step S2, the amount of 4-chlorophenyl diethyl phosphate is 0.95-1 times the molar amount of A; the base is potassium tert-butoxide or sodium tert-butoxide, and the amount is 3-5 times the molar amount of A; the amount of the ligand Xphos is 0.1 wt% of A; In a specific embodiment, in step S3, the amount of 4-bromobenzoic acid is 0.95-1 times the molar amount of B; the inorganic base is cesium carbonate, and the amount is 3-5 times the molar amount of B; the amount of the ligand Ruphos is 0.1 wt% of B; In a specific embodiment, in step S4, the organic base is triethylamine or 4-dimethylaminopyridine, and the amount used is 4.5-5 times the molar amount of C; the amount of di-tert-butyl dicarbonate is 4.1-4.5 times the molar amount of C; In a specific embodiment, in step S5, the amount of oxalyl chloride is 1.3-1.5 times the molar amount of D; In a specific embodiment, in step S6, the amount of triethylamine used is 5-7 times the molar amount of E; the amount of trimethylsilyl trifluoromethanesulfonate used is 4.1-4.5 times the molar amount of E; In a specific embodiment, in step S7, the amount of triethylamine used is 1.5-2 times the molar amount of bio-based polyol castor oil; the amount of F used is 0.95-1 times the molar amount of bio-based polyol castor oil; In a specific embodiment, in step S8, the amount of the modified bio-based PN flame retardant diol is 2.01-2.3 times the molar amount of malonyl chloride; the amount of triethylamine is 2.5-3 times the molar amount of malonyl chloride; and the number average molecular weight of the modified bio-based flame retardant polyester diol is 2000-4000.

[0009] Another object of the present invention is to protect the application of the bio-based polyurethane flame retardant protective material in safety helmets.

[0010] The present invention also discloses a method for preparing a bio-based polyurethane flame-retardant protective material, comprising the following steps: pouring a modified bio-based PN flame-retardant polyester diol, a chain extender, a surfactant, and a water-blowing agent into a container, stirring at a low speed (300-500 rpm) for 5-10 minutes; adding a catalyst and stirring for 2-3 minutes; then adding diisocyanate and stirring at a high speed for 8-15 seconds, quickly pouring the mixture into a mold preheated to 40-50°C, foaming for 10-15 minutes, curing and shaping, demolding, and then aging at 80°C for 8-10 hours to obtain the bio-based polyurethane flame-retardant protective material.

[0011] Beneficial effects

[0012] The present invention provides a bio-based polyurethane flame-retardant protective material and its application in safety helmets. The bio-based polyurethane flame-retardant protective material is a rigid polyurethane foam prepared by the combined action of a modified bio-based PN flame-retardant polyester diol, a chain extender, a surfactant, a water-blowing agent, a diisocyanate, an organotin catalyst, and an organoamine catalyst. Castor oil, as a bio-based material, is environmentally friendly. The modified bio-based PN flame-retardant polydiol is prepared by grafting flame-retardant molecular structures containing N and P elements—melamine, diethyl phenyl phosphate, and benzotriazole—onto bio-based castor oil. The combustion of the phosphate groups not only decomposes a viscous semi-solid substance that coats the polyurethane surface, but also promotes dehydration and carbonization of the polyurethane, isolating it from oxygen infiltration and heat transfer. Simultaneously, the nitrogen-containing groups decompose upon heating to release non-flammable gases such as nitrogen, nitrogen oxides, and water vapor, which not only dilute the oxygen concentration but also remove energy from the decomposition process. The synergistic effect of PN gives polyurethane excellent flame retardant properties and low smoke density, which effectively protects the safety of workers; and the flame retardant group is grafted into the polyurethane chain, which is not prone to loss of flame retardant components, ensuring the long-term usability of the material. The bio-based polyurethane flame retardant protective material prepared by the present invention has the advantages of environmental protection, impact resistance, high energy absorption and flame retardancy, and is particularly suitable for use in the inner protective layer of safety helmets. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Provides a synthetic route for bio-based polyurethane flame retardant protective materials; Figure 2 is the H NMR spectrum of intermediate product F; Figure 3 The infrared spectra of castor oil, modified bio-based PN flame-retardant polyester diol, and flame-retardant polyurethane; DETAILED DESCRIPTION

[0014] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0015] In the examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0016] The raw materials used in the embodiments and comparative examples are now described as follows: Melamine: Product No. M766808, purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd. 5-Bromo-1H-benzotriazole: 98%, product number B857816, purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd. 4-Chlorophenyl diethyl phosphate: 98%, product number A021341, purchased from Shanghai Anaiji Chemical Co., Ltd. 4-Bromobenzoic acid: 97%, product number A010083, purchased from Shanghai Anaiji Chemical Co., Ltd. Malonyl chloride: 98%, product number W810324, purchased from Shanghai Anaiji Chemical Co., Ltd. Tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3): 98%, product number BD21135, purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd.; 2-Dicyclohexylphosphino-2',6'-diisopropoxy-1,1'-biphenyl (Ruphos): 97%, product number BD74362, purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd.; Palladium acetate (Pd(OAc)2): Product No. P815382, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; 2-Dicyclohexylphosphino-2,4,6-triisopropylbiphenyl (XPhos): 97%, product number D806579, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Triethylamine (TEA): 99%, product number T818772, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Di-tert-butyl dicarbonate ((Boc)2O): 98%, product number D806924, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Oxalyl chloride ((COCl)2): 98%, product number O815154, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Trimethylsilyl trifluoromethanesulfonate (TMSOTf): 98%, product number T819078, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Diisocyanate: 4,4'-methylenebis(phenyl isocyanate) (MDI), 98%, product number M813280, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Chain extender: butanediol, 98%, product number B802727, purchased from Shanghai MacLean Biochemical Technology Co., Ltd. Organotin catalyst: dibutyltin dilaurate (DBTDL), 95%, product number D806313, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Organic amine catalyst: triethylenediamine (A33), industrial grade, American Gas Company; Surfactant: organic silicon foam stabilizer (AK8805), industrial grade, Nanjing Meside Chemical Co., Ltd. Modified bio-based PN flame retardant diol: homemade, the preparation steps are as follows: S1. Under a nitrogen atmosphere, melamine (1 equivalent), 0.95 equivalents of 5-bromo-1H-benzotriazole), 4 equivalents of cesium carbonate, and the ligand Ruphos (0.1 wt%) were dissolved in toluene and bubbling was performed for 30 minutes. The catalyst Pd2(dba)3 was added and bubbling was continued for another 10 minutes. The temperature was raised to 100°C and stirred for 24 hours. The reaction was then terminated. The reaction mixture was cooled to room temperature, purified by column chromatography, concentrated, and dried to obtain product A. S2. Under a nitrogen atmosphere, product A (1 equivalent), diethyl 4-chlorophenyl phosphate (0.95 equivalent), sodium tert-butoxide (3 equivalents), and the ligand Xphos (0.1 wt%) were dissolved in toluene and bubbling was performed for 30 minutes. The catalyst Pd(OAc)2 was added and bubbling was continued for another 10 minutes. The temperature was raised to 110°C and stirred for 24 hours before the reaction was completed. The reaction mixture was cooled to room temperature, purified by column chromatography, concentrated, and dried to obtain product B. S3. Under a nitrogen atmosphere, product B (1 equivalent), 4-bromobenzoic acid (0.95 equivalent), cesium carbonate (4 equivalents), and the ligand Ruphos (0.1 wt%) were dissolved in toluene and bubbling was performed for 30 minutes. The catalyst Pd2(dba)3 was added and bubbling was continued for another 10 minutes. The temperature was raised to 100°C and stirred for 24 hours. The reaction was terminated. The reaction mixture was cooled to room temperature, purified by column chromatography, concentrated, and dried to obtain product C. S4. Dissolve product C (1 equivalent) in anhydrous dichloromethane, cool to 0°C, and sequentially add triethylamine (4.5 equivalents) and di-tert-butyl dicarbonate (4.2 equivalents). Slowly warm to room temperature with stirring and react. Monitor the reaction by TLC until starting material C disappears (8 h). Wash the reaction solution with 1 M HCl, and the organic phase is concentrated and dried to obtain product D. S5. Dissolve product D (1 equivalent) in anhydrous dichloromethane, cool to 0°C, and add oxalyl chloride (1.3 equivalents) dropwise, followed by 1-2 drops of DMF. Slowly warm to room temperature and stir for 3 h to complete the reaction. Concentrate the reaction solution and dry to obtain the crude product E. S6. Dissolve product E (1 equivalent) in anhydrous dichloromethane, cool to 0°C, add triethylamine (5-7 equivalents), and stir for 5 minutes. Then, slowly add trimethylsilyl trifluoromethanesulfonate (TMSOTf, 4.3 equivalents) dropwise and stir for 1.5 hours to complete the reaction. Add saturated NaHCO₃ solution, concentrate the organic phase, purify by column chromatography, concentrate the solution, and dry to obtain product F. S7. Dissolve bio-based polyol castor oil (1 equivalent) in anhydrous dichloromethane, cool to 0°C, and slowly add triethylamine (1.8 equivalents) with stirring for 10 minutes. Then, dropwise add F solution (0.95 equivalents) dissolved in a small amount of dichloromethane, warm to room temperature, and stir for 3 hours to complete the reaction. Wash the reaction solution with 1M HCl and saturated NaHCO3 solution, sequentially. The organic phase is concentrated, separated, and purified to obtain modified bio-based PN flame-retardant diol.

[0017] Modified bio-based PN flame retardant polyester diol: homemade, the preparation steps are as follows: The modified bio-based PN flame-retardant diol (2.1 equivalents) was dissolved in anhydrous dichloromethane, cooled to 0°C, and triethylamine (2.5 equivalents) was slowly added and stirred for 10 minutes. Then, a solution of malonyl chloride (1 equivalent) dissolved in a small amount of dichloromethane was added dropwise, and the temperature was raised to room temperature and stirred for 8 hours to complete the reaction. 1M HCl and saturated NaHCO3 solution were added sequentially to wash the reaction solution until neutral. The organic phase was concentrated and cold methanol was added dropwise to precipitate the polymer. The polymer was filtered and dried to obtain a modified bio-based PN flame-retardant polyester diol with a hydroxyl value of 44.88 mg KOH / g and a number average molecular weight of 2500.

[0018] Modified bio-based P flame-retardant polyester diol: homemade, the preparation method is the same as that of bio-based PN flame-retardant polyester diol, the difference is that the P flame-retardant component 4-chlorophenyl diethyl phosphate is grafted onto castor oil to obtain a modified bio-based P flame-retardant polyester diol with a hydroxyl value of 32.06 mgKOH / g and a number average molecular weight of 3500.

[0019] Bio-based polyester diol: Homemade, the preparation method is the same as that of bio-based PN flame-retardant diol, except that the flame-retardant component is not modified on castor oil, and the obtained bio-based polyester diol has a hydroxyl value of 28.05 mg KOH / g and a number average molecular weight of 4000.

[0020] It should be noted that the “equivalent” used in the present invention refers to “molar equivalent”.

[0021] Unless otherwise specified, the components and raw materials used in the examples and comparative examples of the present invention are all commercially available raw materials, and the components and raw materials used in each parallel experiment are all of the same kind.

[0022] Examples and Comparative Examples A bio-based polyurethane flame retardant protective material, the weight formula of which is shown in Table 1, and the preparation method is as follows: Pour the modified bio-based PN flame-retardant polyester diol, chain extender, surfactant, and water-blowing agent into a container and mix at low speed (300-500 rpm) for 5-10 minutes; add a catalyst and stir for 2-3 minutes; then add diisocyanate and stir at high speed for 8-15 seconds. The mixture is quickly poured into a mold preheated to 40-50°C for foaming for 10-15 minutes, curing and shaping, demolding, and then aging at 80°C for 8-10 hours to obtain a bio-based polyurethane flame-retardant protective material.

[0023] Table 1 Bio-based polyurethane flame retardant protective materials (parts by weight)

[0024] The bio-based polyurethane flame retardant protective material prepared in the examples and comparative examples was subjected to the following performance tests, and the results are shown in the accompanying drawings and Table 2, respectively.

[0025] 1. Infrared Spectroscopy: Modified bio-based PN flame-retardant polyester diol and bio-based polyurethane flame-retardant protective material were mixed with potassium bromide at a ratio of 1:50 to form a pellet. This test was performed using an Avatar 380 spectrometer. The sample was pressed into the potassium bromide pellet. Before the test, a blank background was scanned, and then the pellet sample was placed in the test. The scanning range was 500-4000 cm -1 , the results are as follows Figure 1 shown.

[0026] 2. Compression Strength: A universal testing machine was used to test the compressive strength of bio-based polyurethane flame retardant protective materials. Testing was performed according to the test method in GB / T 8813-2008, "Rigid Foam Plastics - Determination of Compression Properties." Polyurethane was cut into 10 cm x 10 cm x 10 cm strips. Testing was performed at a rate of 5 mm / min using the universal testing machine. The average of the test results was calculated.

[0027] 3. Impact resistance (peak force): Tested using a drop weight impact tester in accordance with ISO 6603. Cut the polyurethane into 5 cm x 5 cm x 2 cm strips. Set the impact energy to 15 J and record the maximum impact force that the strip can withstand.

[0028] 4. Oxygen Index Test (LOI): According to the test method of GB / T 2406.2-2009 standard "Plastics - Determination of Burning Behavior by Oxygen Index Method - Part 2: Room Temperature Test", the polyurethane was cut into sample strips of 10 cm * 1 cm * 1 cm for testing.

[0029] 5. Vertical Flame Test: According to the test method in GB / T 2408-2008, "Plastics - Determination of Combustion Properties - Horizontal and Vertical Methods," polyurethane was cut into 12.5 cm x 1.3 cm x 1 cm strips for testing. The bottom end of the strip was placed 1 cm above the center of the flame. After igniting the strip for 10 seconds, the flame was immediately removed. The time it took for the afterflame to extinguish, t1, was recorded. This procedure was repeated, and the time it took for the second extinguishing flame, t2, was recorded. Each sample was tested five times.

[0030] 6. UL-94 vertical burning grade judgment standard: The UL-94 grade is judged based on the ratio of t1 to t2. V-0: (t1 / t2) for a single sample strip ≤ 10 s, t1+t2 for all sample strips ≤ 50 s, indicating that the sample is not completely burned and the molten droplets do not ignite the cotton; V-1: (t1 / t2) for a single sample strip ≤ 30 s, t1+t2 for all sample strips ≤ 250 s, indicating that the sample is not completely burned and the molten droplets do not ignite the cotton; V-2: (t1 / t2) for a single sample strip ≤ 30 s, t1+t2 for all sample strips ≤ 250 s, indicating that the sample is not completely burned and the molten droplets ignite the cotton.

[0031] 7. Smoke density test (Dm): According to the test standard of GB / T8323.2-2008 "Plastics Smoke Generation Part 2: Single Chamber Test Method for Determination of Smoke Density", the polyurethane was cut into 7.5 cm * 7.5 cm * 0.1 cm sample strips for testing. The test was conducted using an NBS smoke density test chamber, placed under the radiation cone, and the heat radiation power was set to 25 kW / m 2 , the box temperature is 35℃, test for 25 minutes, and record the results.

[0032] Table 2 Performance test results of bio-based polyurethane flame retardant protective materials

[0033] From the attached Figure 2 From the H-NMR spectrum, we can see that the integral is consistent with the number of hydrogen atoms in the molecule, and the displacement of each hydrogen atom in the spectrum is consistent with the chemical environment, indicating that the intermediate product F was successfully synthesized.

[0034] From the attached Figure 3 It can be seen that the peak appears at 3490 cm -1 The peaks near the stretching vibration of -OH appear at 2980-2850 cm -1 The peak value at 1161 cm-1 is attributed to the stretching vibration of CH. -1 The stretching vibration of ester COC is at 1675-1500 cm -1 The signal peak at 3382 cm belongs to the vibration of C=C. -1A new peak appears near the CN absorption peak; at 1675-1500 cm -1 The absorption signals of the secondary amine -NH- and -N=N- in benzotriazole are in the range of 1239 cm -1 The characteristic peak of phosphate-P=O, 903 cm -1 is the characteristic peak of -POC, 1215 cm -1 The stretching vibration of -NN- in benzotriazole is also observed. At the same time, the para-substituted benzene at 830 cm -1 The unique signal at 3400-3300 cm indicates that the flame retardant components melamine, diethyl phenyl phosphate and benzotriazole have been successfully connected to bio-based castor oil. In the flame retardant polyurethane spectrum, the -OH signal disappears, and the signal at 3400-3300 cm -1 A broad peak appears at 2270-2250 cm, which is the stretching vibration peak of -NHCOO and NH in the original flame retardant polyglycol. -1 No asymmetric vibration peak belonging to -NCO in isocyanate MDI was seen nearby, and the characteristic signal of flame retardant polyglycol was also contained, indicating that flame retardant polyglycol and MDI reacted to prepare flame retardant polyurethane.

[0035] As can be seen from Table 2, compared with Comparative Examples 1 and 2, the polyurethane obtained by introducing melamine, diethyl phenyl phosphate, and benzotriazole into the bio-based castor oil structure to prepare the modified bio-based PN flame-retardant polyglycol has a stable three-dimensional cross-linked network and greatly improved mechanical strength of the polyurethane foam due to the effective increase in cross-linking density of the polyurethane due to the introduction of rigid benzene rings and polar -NH- groups. At the same time, the flexible long-chain structure of castor oil allows it to retain a certain degree of elasticity, resulting in good impact resistance and high energy absorption.

[0036] On the other hand, when polyurethane foam burns, the combustion of the phosphate groups can not only decompose the sticky semi-solid substance covering the polyurethane surface, but also promote the dehydration and carbonization of the polyurethane, isolating oxygen infiltration and heat transfer; at the same time, the nitrogen-containing melamine and benzotriazole flame retardant groups decompose under heat to release nitrogen, nitrogen oxides, water vapor and other difficult-to-burn gases, which not only dilute the oxygen concentration but also take away energy during the decomposition process. The synergistic effect of PN gives the polyurethane a shorter burning time and low smoke density, showing good flame retardant properties. When only the P flame retardant group is present, the flame retardancy of the polyurethane is greatly reduced, indicating the excellent flame retardancy of the PN synergistic flame retardant.

[0037] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A bio-based polyurethane flame-retardant protective material, comprising the following components by weight: 95-110 parts of a modified bio-based PN flame-retardant polyester diol, 10-20 parts of a chain extender, 0.8-1.5 parts of a surfactant, 2-6 parts of a water-blowing agent, 60-90 parts of a diisocyanate, 0.1-0.5 parts of an organotin catalyst, and 0.2-0.5 parts of an organic amine catalyst; the modified bio-based PN flame-retardant polyester diol has a structure as shown in Formula 1: Formula 1.

2. The bio-based polyurethane flame retardant protective material according to claim 1, characterized in that: The chain extender is one of ethylene glycol, propylene glycol and butanediol; the surfactant is an organosilicon foam stabilizer; the diisocyanate is 4,4'-methylenebis(phenyl isocyanate); the organotin catalyst is dibutyltin dilaurate; and the organoamine catalyst is triethylenediamine.

3. The bio-based polyurethane flame retardant protective material according to claim 1, characterized in that: The preparation steps of the modified bio-based PN flame retardant polyester diol are as follows: S1. Under a nitrogen atmosphere, melamine, 5-bromo-1H-benzotriazole, an inorganic base, and a ligand Ruphos were dissolved in toluene; Pd2(dba)3 was added as a catalyst, the temperature was raised to 100-110 °C, and the reaction was stirred for 18-24 hours; Cooling, column chromatography purification, concentration, and drying to obtain product A; S2. Under a nitrogen atmosphere, product A, 4-chlorophenyl diethyl phosphate, a base, and a ligand Xphos were dissolved in toluene; Pd(OAc)2 was added as a catalyst, the temperature was raised to 100-110 °C, and the reaction was stirred for 24-36 hours; Cooling, column chromatography purification, concentration, and drying to obtain product B; S3. Under a nitrogen atmosphere, product B, 4-bromobenzoic acid, an inorganic base, and the ligand Ruphos were dissolved in toluene; Pd2(dba)3 was added as a catalyst, the temperature was raised to 95-115 ° C, the reaction was stirred for 20-24 hours, cooled, purified by column chromatography, concentrated, and dried to obtain product C; S4. The product C was dissolved in anhydrous dichloromethane, ice bath, followed by the addition of an organic base and di-tert-butyl dicarbonate; the reaction was stirred at room temperature for 10-16h; the reaction solution was washed with 1M HCl, and the organic phase was concentrated and dried to obtain product D; S5. Dissolve product D in anhydrous dichloromethane, cool on ice, add oxalyl chloride dropwise, and then add 1-2 drops of DMF dropwise; warm to room temperature and stir for 1-3 h; concentrate the reaction solution and dry to obtain crude product E; S6. The product E was dissolved in anhydrous dichloromethane, ice bath, and triethylamine was added; trimethylsilyl trifluoromethanesulfonate was then slowly added dropwise and stirred for 0.5-2 hours; a saturated NaHCO3 solution was added, and the organic phase was concentrated, purified by column chromatography, concentrated, and dried to obtain product F; S7 castor oil was dissolved in anhydrous dichloromethane, ice bath, triethylamine was added; then a small amount of dichloromethane was dissolved in the F solution was added dropwise and the reaction was allowed to react at room temperature for 1-4 hours; HCl was added sequentially to wash the reaction solution and saturated NaHCO3 solution, the organic phase was concentrated, separated and purified to obtain a modified bio-based PN flame retardant diol; S8. Esterification and polycondensation The modified bio-based PN flame-retardant diol was dissolved in anhydrous dichloromethane, ice-bathed, triethylamine was added, and then a solution of malonyl chloride dissolved in a small amount of dichloromethane was added dropwise, and stirred at room temperature for 4-10 hours; HCl was added to wash the reaction solution and a saturated NaHCO3 solution was added sequentially until neutral, the organic phase was concentrated and cold methanol was added dropwise to precipitate the polymer, which was filtered and dried to obtain a modified bio-based PN flame-retardant polyester diol with a hydroxyl value of 28.05-56.1 mg KOH / g.

4. The bio-based polyurethane flame retardant protective material according to claim 3, characterized in that: In step S1, the amount of 5-bromo-1H-benzotriazole is 0.95-1 times the molar amount of melamine; the inorganic base is potassium phosphate or cesium carbonate, and the amount is 3-5 times the molar amount of melamine; the amount of the ligand Ruphos is 0.1 wt% of melamine.

5. The bio-based polyurethane flame retardant protective material according to claim 3, characterized in that: In step S2, the amount of 4-chlorophenyl diethyl phosphate is 0.95-1 times the molar amount of A; the base is potassium tert-butoxide or sodium tert-butoxide, and the amount is 3-5 times the molar amount of A; the amount of the ligand Xphos is 0.1 wt% of A.

6. The bio-based polyurethane flame retardant protective material according to claim 3, characterized in that: In step S3, the amount of 4-bromobenzoic acid is 0.95-1 times the molar amount of B; the inorganic base is cesium carbonate, and the amount is 3-5 times the molar amount of B; The amount of the ligand Ruphos is 0.1 wt% of B.

7. The bio-based polyurethane flame retardant protective material according to claim 3, characterized in that: In step S4, the organic base is triethylamine or 4-dimethylaminopyridine, and the amount used is 4.5-5 times the molar amount of C; the amount of di-tert-butyl dicarbonate used is 4.1-4.5 times the molar amount of C; in step S5, the amount of oxalyl chloride used is 1.3-1.5 times the molar amount of D; in step S6, the amount of triethylamine used is 5-7 times the molar amount of E; and the amount of trimethylsilyl trifluoromethanesulfonate used is 4.1-4.5 times the molar amount of E.

8. The bio-based polyurethane flame-retardant protective material according to claim 3, wherein in step S8, the amount of the modified bio-based PN flame-retardant diol is 2.01-2.3 times the molar amount of malonyl chloride; the amount of triethylamine is 2.5-3 times the molar amount of malonyl chloride; and the number average molecular weight of the modified bio-based PN flame-retardant polyester diol is 2000-4000.

9. Use of the bio-based polyurethane flame retardant protective material according to any one of claims 1 to 8 in a safety helmet.

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