A biodegradable bio-based polyurethane foam and its preparation method

Abstract

This invention relates to the field of biodegradable bio-based polyurethane foam preparation technology, specifically disclosing a biodegradable bio-based polyurethane foam and its preparation method. The raw materials for preparing this polyurethane foam include bio-based polyols, chain extenders, functional fillers, foaming agents, catalysts, foam stabilizers, and isocyanates. This invention synthesizes a bio-based polyol possessing both a rigid framework and dynamic covalent bonds through a grafting reaction of rosin-based maleic anhydride adduct, cystamine dihydrochloride, and epoxidized soybean oil; functional fillers are prepared by crosslinking aminated nanocrystalline cellulose with phytic acid; and the finished product is obtained by ultrasonic dispersion premixing, emulsification, and high-speed shear foaming and curing. This invention uses a one-step foaming process to prepare the foam, which is simple, controllable, and easy to scale up for industrial production. The resulting foam has a high bio-based content, excellent mechanical properties, flame retardant and smoke-suppressing properties, and controllable biodegradability. It is environmentally friendly and can be widely used in cushioning packaging, bedding, agricultural insulation, and other fields.

Description

Technical Field

[0001] This invention relates to the field of polyurethane foam preparation technology, and more specifically, to a biodegradable bio-based polyurethane foam and its preparation method. Background Technology

[0002] Polyurethane foam, due to its excellent physical properties such as thermal insulation, cushioning, and sound absorption, has been widely used in many fields, including packaging, construction, bedding, and automobile manufacturing. However, traditional polyurethane foam mainly relies on non-renewable petroleum-based raw materials for synthesis. With the increasing depletion of fossil resources and the growing global awareness of environmental protection, traditional thermosetting polyurethane foam cannot biodegrade naturally after disposal, easily causing serious white pollution problems. Therefore, using renewable biomass resources to replace traditional petroleum-based raw materials to prepare environmentally friendly polyurethane materials has become an important development trend in this field.

[0003] Currently, bio-based raw materials such as vegetable oils and rosin have been attempted to be introduced into polyurethane foaming systems. However, foams prepared directly from vegetable oil polyols often suffer from low mechanical support and poor dimensional stability after foaming due to their molecular skeleton being mostly flexible long-chain fatty acids, making it difficult to meet the requirements of applications with high mechanical performance. Secondly, the dense three-dimensional cross-linked network inside polyurethane foam makes it extremely difficult to degrade in natural environments, resulting in very low recycling rates after disposal. In addition, the inherent flammability of polyurethane foam is also a key obstacle limiting its high-end applications. During combustion, this material not only releases a large amount of heat but also produces deadly toxic fumes. Traditional solutions typically involve adding halogenated or phosphate-based flame retardants through physical blending, but this often damages the microscopic pore structure inside the foam, leading to a significant decrease in the material's mechanical properties and posing risks of flame retardant leaching and environmental toxicity. In summary, there is an urgent need to develop a novel bio-based polyurethane foam preparation method to solve the aforementioned technical problems. Summary of the Invention

[0004] The purpose of this invention is to provide a biodegradable bio-based polyurethane foam and its preparation method. The resulting foam has a high bio-based content and possesses excellent mechanical properties, flame retardant and smoke-suppressing properties, and controllable biodegradability. It is green and environmentally friendly and can be widely used in cushioning packaging, bedding, agricultural insulation and other fields.

[0005] To address the aforementioned technical problems, this invention provides a biodegradable bio-based polyurethane foam, employing the following technical solution:

[0006] The raw materials for its preparation, by weight, include 80-100 parts of bio-based polyol, 5-10 parts of chain extender, 5-10 parts of functional filler, 2-5 parts of deionized water foaming agent, 0.6-0.9 parts of catalyst, 1-3 parts of foam stabilizer, and 140-170 parts of isocyanate; wherein the isocyanate is selected from any one of polymeric diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, or dicyclohexylmethane diisocyanate.

[0007] Preferably, the preparation steps of the bio-based polyol are as follows:

[0008] S1. Rosin is heated to 100-110℃ under nitrogen protection, and then the temperature is raised to 190-200℃. Maleic anhydride and hydroquinone are added in 3-4 batches, with an interval of 45-50 min between each batch. The reaction is carried out at a constant temperature of 300-400 rpm for 4-6 h. After the reaction is completed, the temperature is lowered to 70-75℃, and anhydrous ethanol is added and stirred until completely miscible. The mixture is filtered while hot, and the filtrate is allowed to stand at 0-5℃ for crystallization for 12-15 h. The rosin-based maleic anhydride adduct is obtained by vacuum filtration, washing, and vacuum drying.

[0009] S2. Dissolve the rosin-based maleic anhydride adduct in anhydrous N,N-dimethylformamide to obtain a homogeneous and transparent solution. In a separate reaction vessel, add cystamine dihydrochloride and triethylamine to anhydrous N,N-dimethylformamide and stir at room temperature for 1-1.5 h to fully neutralize and remove hydrochloric acid. Filter to remove the generated triethylamine hydrochloride precipitate to obtain an anhydrous DMF solution of free cystamine. Add the anhydrous DMF solution of cystamine to the above rosin-based maleic anhydride adduct solution at a uniform rate over 30-40 min. After the addition is complete, stir the reaction at room temperature in the dark for 2-3 h, then raise the temperature to 60-70℃ and stir at 400-500 rpm for 10-12 h. After the reaction is complete, add the reaction solution to deionized water and stir to precipitate. After filtration, wash and vacuum dry the precipitate to obtain a bifunctional crosslinking intermediate.

[0010] S3. Heat the epoxidized soybean oil to 100-120℃, add the bifunctional crosslinking intermediate prepared in S2 and 1-2 parts of tetrabutylammonium bromide under stirring, and perform a constant temperature grafting reaction at 400-450 rpm for 6-8 hours under nitrogen protection. Cool down and discharge to obtain bio-based polyol.

[0011] Preferably, in step S1, the components by weight are 100-120 parts rosin, 30-40 parts maleic anhydride, and 0.2-0.4 parts hydroquinone, the reaction temperature is 190-200℃, and the crystallization temperature is 0-5℃.

[0012] Preferably, in step S2, the components by weight are 50-60 parts of rosin-based maleic anhydride adduct, 200-240 parts of anhydrous N,N-dimethylformamide, 12-16 parts of cystamine dihydrochloride, 18-24 parts of triethylamine, and 100-120 parts of anhydrous N,N-dimethylformamide, and the reaction temperature is 60-70°C.

[0013] Preferably, in step S3, the components by weight are 100-120 parts of epoxidized soybean oil, 30-50 parts of a bifunctional crosslinking intermediate, and 1-2 parts of tetrabutylammonium bromide phase transfer catalyst, and the reaction temperature is 100-120℃.

[0014] Preferably, the preparation steps of the functional filler are as follows:

[0015] A1. Disperse nanocrystalline cellulose in an aqueous ethanol solution and sonicate at 40-50 kHz for 30-40 min at room temperature to form a suspension. Adjust the pH to 8.0-8.5 with ammonia. Separately, add 3-aminopropyltriethoxysilane to an aqueous ethanol solution of the same concentration and stir at room temperature for 15-20 min to pre-hydrolyze it. Add the pre-hydrolyzed cellulose dropwise to the suspension at 1-3 ml / min and reflux at 70-75℃ and 300-400 rpm for 6-8 h. Centrifuge, wash, and freeze-dry the product to obtain aminated nanocellulose powder.

[0016] A2. Disperse aminated nanocellulose powder in deionized water, adjust the pH to 6.0-6.5 with hydrochloric acid while stirring at 260-300 rpm, add phytic acid aqueous solution dropwise at a uniform rate over 20-30 min, adjust the pH to 6.0-6.5 again after the addition is complete, heat to 60-70℃ and stir for 4-6 h. After filtration and washing with water until neutral, vacuum dry the product and grind it through a 200-300 mesh sieve to obtain the functional filler.

[0017] Preferably, in step A1, the following components are used by weight: 10-15 parts of nanocrystalline cellulose, 95-100 parts of 80-85 wt% ethanol aqueous solution, 3-6 parts of 3-aminopropyltriethoxysilane, and 30-40 parts of ethanol aqueous solution of the same concentration; in step A2, the following components are used by weight: 15-20 parts of aminated nanocrystalline cellulose powder, 95-105 parts of deionized water, and 8-12 parts of 35-45 wt% phytic acid aqueous solution.

[0018] A method for preparing biodegradable bio-based polyurethane foam includes the following steps:

[0019] According to the above mass ratio, mix 80-100 parts of bio-based polyol with 3-5 parts of chain extender evenly, add 5-15 parts of functional filler, and ultrasonically disperse at 50-60KHz for 10-15min to form a uniform suspension premix; then add 2-4 parts of deionized water, 0.3-0.8 parts of catalyst, and 1-2 parts of foam stabilizer to the premix, and premix at 800-1000rpm for 2-3min to form a uniformly emulsified white material system; finally, pour the metered isocyanate into the white material, and shear mix at 2500-3000rpm for 10-15s, then pour it into a mold preheated to 40-50℃ for free stretching and foaming. After the initial foaming is completed, transfer it to an oven at 70-80℃ for deep curing and crosslinking for 12-24h, and demold to obtain bio-based polyurethane foam.

[0020] Preferably, the chain extender is selected from any one of glycerol, ethylene glycol, 1,4-butanediol or pentaerythritol, and the catalyst is selected from at least one of dibutyltin dilaurate, stannous octoate and triethylenediamine.

[0021] Preferably, the foam stabilizer is selected from at least one of fatty alcohol polyoxyethylene ether, octylphenol polyoxyethylene ether, and sodium dodecylbenzene sulfonate.

[0022] In summary, the present invention has the following beneficial effects:

[0023] 1. This invention uses bio-based polyols and functional fillers as core raw materials, combined with chain extenders, foaming agents, catalysts, foam stabilizers, and isocyanates, and employs a one-step foaming process involving ultrasonic dispersion premixing, emulsification, high-speed shear foaming, and curing to prepare biodegradable bio-based polyurethane foam. This preparation method features a simple and controllable process flow, mild reaction conditions, and the use of environmentally friendly renewable raw materials throughout the system, with no toxic or harmful components added, thus reducing the environmental impact of the product from the source. Through the molecular structure design of the core functional raw materials and the synergistic effect between components, the invention achieves a synergistic improvement in the bio-based content, mechanical properties, flame retardant and smoke-suppressing properties, and controllable biodegradability of the foam material. This effectively overcomes the technical shortcomings of existing bio-based polyurethane foams, such as difficulty in achieving a balance of various properties, complex preparation processes, and poor scalability.

[0024] 2. This invention prepares a bio-based polyol by combining rosin with maleic anhydride, then introducing cystamine containing free disulfide bonds to obtain a crosslinking intermediate, and finally grafting it onto the macromolecular chain of epoxidized soybean oil. The rosin-based rigid tricyclic phenanthrene backbone introduced into the bio-based polyol molecular chain can construct a stable rigid support structure in the polyurethane crosslinking network, effectively solving the problems of insufficient mechanical load-bearing capacity and poor dimensional stability of foam materials caused by the excessive proportion of flexible fatty long chains in traditional plant oil-based polyols. This significantly improves the mechanical strength and deformation resistance of the polyurethane matrix. The precisely interlocked dynamic disulfide bonds in the molecular chain can form a dynamic and reversible covalent crosslinking network in the polyurethane system, ensuring the structural stability and performance durability of the material during normal use, and enabling the controllable breakage of the crosslinking network in specific degradation environments. This greatly improves the biodegradability of the material and solves the industry pain point of the dense crosslinking network of traditional thermosetting polyurethane foam, which is difficult to degrade in natural environments. At the same time, this polyol uses renewable forest products and oil processing by-products as core raw materials, which greatly increases the bio-based proportion of the product, realizes the high-value utilization of biomass resources, and effectively reduces the dependence of polyurethane materials on non-renewable petroleum-based raw materials.

[0025] 3. This invention uses nanocrystalline cellulose as a matrix, first preparing aminated nanocellulose powder by modification with a silane coupling agent, and then preparing functional fillers through phytic acid crosslinking reaction. This functional filler uses nanocrystalline cellulose as a reinforcing core, which can form uniform heterogeneous nucleation sites during polyurethane foaming, optimize the microscopic cell structure inside the foam, and further improve the mechanical properties and dimensional stability of the material. Through the amination modification of silane coupling agent, active amino groups that can participate in the polyurethane reaction are introduced on the surface of cellulose, which improves the interfacial compatibility and bonding force between the filler and the polyurethane matrix, effectively avoiding the problem of easy agglomeration and uneven dispersion of inorganic fillers in the polymer matrix, and solving the defects of traditional physical blend fillers that easily damage the foam matrix structure and lead to a decrease in the mechanical properties of the material. At the same time, through the ionic cross-linking and hydrogen bond network of phytic acid molecules and amino groups on the surface of cellulose, the bio-based phosphorus and nitrogen synergistic flame retardant components are stably immobilized on the cellulose matrix. This not only plays an efficient role in char formation, flame retardancy and smoke suppression during the combustion of the material, but also fundamentally solves the problems of easy migration and precipitation and poor functional durability of traditional physical additive flame retardants. Moreover, it adopts a fully bio-based halogen-free flame retardant system, with no environmental toxicity risks, and achieves an integrated and synergistic improvement of the material's mechanical reinforcement and flame retardant and smoke suppression functions. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the experimental materials used, unless otherwise specified, were all purchased from conventional biochemical reagent stores. All quantitative experiments in the following examples were performed in triplicate, and the data are the average of the three replicates or the average ± standard deviation.

[0028] Polymeric diphenylmethane diisocyanate, purchased from Hubei Xinrunde Chemical Co., Ltd., CAS No. 101-68-8;

[0029] Rosin, purchased from Shandong Shengjing New Material Technology Co., Ltd.;

[0030] Cystamine dihydrochloride, purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number S31097;

[0031] Epoxidized soybean oil, purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number S50881;

[0032] Nanocrystalline cellulose was purchased from Angxing New Carbon Materials Changzhou Co., Ltd.

[0033] Example 1

[0034] This embodiment provides a method for preparing biodegradable bio-based polyurethane foam, using the following technical solution:

[0035] By weight, 80 parts of bio-based polyol and 3 parts of pentaerythritol were mixed evenly, and 5 parts of functional filler were added. The mixture was ultrasonically dispersed at 50 kHz for 15 min to form a uniform suspension premix. Then, 2 parts of deionized water, 0.3 parts of triethylenediamine and 1-2 parts of sodium dodecylbenzenesulfonate were added to the premix, and the mixture was premixed at 800 rpm for 3 min to form a uniformly emulsified white material system. Finally, 140 parts of dicyclohexylmethane diisocyanate were poured into the white material, and the mixture was sheared and mixed at 2500 rpm for 15 s. The mixture was then poured into a mold preheated to 40 ℃ for free stretching and foaming. After the initial foaming was completed, the mixture was transferred to a 70 ℃ oven for deep curing and crosslinking for 24 h. The bio-based polyurethane foam was then demolded.

[0036] The preparation steps of the functional filler are as follows:

[0037] A1. Disperse 10 parts of nanocrystalline cellulose in 95 parts of 85wt% ethanol aqueous solution, and sonicate at 40KHz for 40min at room temperature to form a suspension. Adjust the pH to 8.0 with ammonia. Separately, add 3 parts of 3-aminopropyltriethoxysilane to 30 parts of ethanol aqueous solution of the same concentration, stir and pre-hydrolyze at room temperature for 15min, and add it dropwise to the suspension at 1ml / min. Reflux at 70℃ and 300rpm for 8h. The product is centrifuged, washed, and freeze-dried to obtain aminated nanocellulose powder.

[0038] A2. Disperse 15 parts of aminated nanocellulose powder in 95 parts of deionized water, adjust the pH to 6.0 with hydrochloric acid while stirring at 260 rpm, add 8 parts of 45 wt% phytic acid aqueous solution dropwise at a uniform rate over 20 min, adjust the pH to 6.0 again after the addition is complete, heat to 60℃ and stir for 6 h, filter the product, wash with water until neutral, vacuum dry, grind through a 200 mesh sieve to obtain the functional filler.

[0039] The preparation steps of the bio-based polyol are as follows:

[0040] S1. Under nitrogen protection, 100 parts of rosin were heated to 100°C and then heated to 190°C. 30 parts of maleic anhydride and 0.2 parts of hydroquinone were added in 3 batches with an interval of 45 min between each batch. The reaction was carried out at a constant temperature of 300 rpm for 6 h. After the reaction was completed, the temperature was lowered to 70°C and anhydrous ethanol was added and stirred until completely miscible. The mixture was filtered while hot and the filtrate was allowed to stand at 5°C for crystallization for 15 h. The rosin-based maleic anhydride adduct was obtained by vacuum filtration, washing and vacuum drying.

[0041] S2. Dissolve 50 parts of rosin-based maleic anhydride adduct in 200 parts of anhydrous N,N-dimethylformamide to obtain a homogeneous and transparent solution. In a separate reaction vessel, add 12 parts of cystamine dihydrochloride and 18 parts of triethylamine to 100 parts of anhydrous N,N-dimethylformamide. Stir at room temperature for 1 hour to fully neutralize and remove hydrochloric acid. Filter to remove the generated triethylamine hydrochloride precipitate to obtain an anhydrous DMF solution of free cystamine. Add the anhydrous DMF solution of cystamine to the above rosin-based maleic anhydride adduct solution at a uniform rate over 30 minutes. After the addition is complete, stir the reaction at room temperature in the dark for 2 hours, then raise the temperature to 60°C and stir at 400 rpm for 12 hours. After the reaction is complete, add the reaction solution to deionized water and stir to precipitate. After filtration, wash and vacuum dry the precipitate to obtain a bifunctional crosslinked intermediate.

[0042] S3. Heat 100 parts of epoxidized soybean oil to 100℃, add 30 parts of the bifunctional crosslinking intermediate prepared in S2 and 1 part of tetrabutylammonium bromide under stirring, and perform a grafting reaction at a constant temperature of 400 rpm for 8 hours under nitrogen protection. Cool down and discharge to obtain bio-based polyol.

[0043] Example 2

[0044] This embodiment provides a method for preparing biodegradable bio-based polyurethane foam, using the following technical solution:

[0045] According to the mass fraction, 90 parts of bio-based polyol and 4 parts of 1,4-butanediol were mixed evenly, and 8 parts of functional filler were added. The mixture was ultrasonically dispersed at 52 kHz for 14 min to form a uniform suspension premix. Then, 3 parts of deionized water, 0.4 parts of stannous octoate, and 1.5 parts of octylphenol polyoxyethylene ether were added to the premix. The mixture was premixed at 900 rpm for 2.6 min to form a uniformly emulsified white material system. Finally, 145 parts of hexamethylene diisocyanate were poured into the white material and sheared at 2700 rpm for 14 s. The mixture was then poured into a mold preheated to 45 ℃ for free stretching and foaming. After the initial foaming was completed, the mixture was transferred to a 75 ℃ oven for deep curing and crosslinking for 20 h. The bio-based polyurethane foam was then demolded.

[0046] The preparation steps of the functional filler are as follows:

[0047] A1. Disperse 12 parts of nanocrystalline cellulose in 98 parts of 84wt% ethanol aqueous solution, and sonicate at 45KHz for 38min at room temperature to form a suspension. Adjust the pH to 8.2 with ammonia. Separately, add 4 parts of 3-aminopropyltriethoxysilane to 35 parts of ethanol aqueous solution of the same concentration, stir and pre-hydrolyze at room temperature for 18min, and add it dropwise to the suspension at 2ml / min. Reflux at 72℃ and 320rpm for 7.5h. The product is centrifuged, washed, and freeze-dried to obtain aminated nanocellulose powder.

[0048] A2. Disperse 17 parts of aminated nanocellulose powder in 97 parts of deionized water. Adjust the pH to 6.2 with hydrochloric acid while stirring at 275 rpm. Add 9 parts of 42 wt% phytic acid aqueous solution dropwise at a uniform rate over 25 min. After the addition is complete, adjust the pH to 6.2 again. Heat to 65℃ and stir for 5.7 h. After filtration and washing with water until neutral, the product is vacuum dried and ground through a 250-mesh sieve to obtain the functional filler.

[0049] Preferably, the preparation steps of the bio-based polyol are as follows:

[0050] S1. Under nitrogen protection, 105 parts of rosin were heated to melt at 105°C, and then the temperature was raised to 195°C. 35 parts of maleic anhydride and 0.3 parts of hydroquinone were added in three batches, with an interval of 46 min between each batch. The reaction was carried out at a constant temperature of 320 rpm for 5.8 h. After the reaction was completed, the temperature was lowered to 72°C, and anhydrous ethanol was added and stirred until completely miscible. The mixture was filtered while hot, and the filtrate was allowed to stand at 4°C for crystallization for 14.5 h. The rosin-based maleic anhydride adduct was obtained by vacuum filtration, washing, and vacuum drying.

[0051] S2. Dissolve 52 parts of rosin-based maleic anhydride adduct in 210 parts of anhydrous N,N-dimethylformamide to obtain a homogeneous and transparent solution. In a separate reaction vessel, add 13 parts of cystamine dihydrochloride and 19 parts of triethylamine to 105 parts of anhydrous N,N-dimethylformamide. Stir at room temperature for 1.2 h to fully neutralize and remove hydrochloric acid. Filter to remove the generated triethylamine hydrochloride precipitate to obtain an anhydrous DMF solution of free cystamine. Add the anhydrous DMF solution of cystamine to the above rosin-based maleic anhydride adduct solution at a uniform rate over 32 min. After the addition is complete, stir the reaction at room temperature in the dark for 2.2 h, then raise the temperature to 65℃ and stir at 420 rpm for 11.5 h. After the reaction is completed, add the reaction solution to deionized water and stir to precipitate. After filtration, wash and vacuum dry the precipitate to obtain a bifunctional crosslinking intermediate.

[0052] S3. Heat 105 parts of epoxidized soybean oil to 110°C, add 35 parts of the bifunctional crosslinking intermediate prepared in S2 and 1.5 parts of tetrabutylammonium bromide under stirring, and perform a grafting reaction at a constant temperature of 420 rpm for 7.8 h under nitrogen protection. Cool down and discharge to obtain bio-based polyol.

[0053] Example 3

[0054] This embodiment provides a method for preparing biodegradable bio-based polyurethane foam, using the following technical solution:

[0055] By weight, 100 parts of bio-based polyol and 5 parts of glycerol were mixed evenly, and 15 parts of functional filler were added. The mixture was ultrasonically dispersed at 60 kHz for 10 min to form a uniform suspension premix. Then, 4 parts of deionized water, 0.8 parts of dibutyltin dilaurate, and 2 parts of fatty alcohol polyoxyethylene ether were added to the premix. The mixture was premixed at 1000 rpm for 2 min to form a uniformly emulsified white material system. Finally, 170 parts of polymerized diphenylmethane diisocyanate were poured into the white material and sheared at 3000 rpm for 10 s. The mixture was then poured into a mold preheated to 50 ℃ for free stretching and foaming. After the initial foaming was completed, the mixture was transferred to an 80 ℃ oven for deep curing and crosslinking for 12 h. The bio-based polyurethane foam was then demolded.

[0056] The preparation steps of the functional filler are as follows:

[0057] A1. Disperse 15 parts of nanocrystalline cellulose in 100 parts of 80wt% ethanol aqueous solution, sonicate at 50KHz for 30min at room temperature to form a suspension, and adjust the pH to 8.5 with ammonia; separately add 6 parts of 3-aminopropyltriethoxysilane to 40 parts of ethanol aqueous solution of the same concentration, stir at room temperature for 20min for pre-hydrolysis, add dropwise to the suspension at 3ml / min, reflux at 75℃ and 400rpm for 6h, and centrifuge, wash and freeze dry the product to obtain aminated nanocellulose powder;

[0058] A2. Disperse 20 parts of aminated nanocellulose powder in 105 parts of deionized water. Adjust the pH to 6.5 with hydrochloric acid while stirring at 300 rpm. Add 12 parts of 35 wt% phytic acid aqueous solution dropwise at a uniform rate over 20 min. After the addition is complete, adjust the pH to 6.5 again. Heat to 70℃ and stir for 4 h. After filtration and washing with water until neutral, vacuum dry and grind through a 300-mesh sieve to obtain the functional filler.

[0059] The preparation steps of the bio-based polyol are as follows:

[0060] S1. Under nitrogen protection, 120 parts of rosin were heated to melt at 110°C, and then the temperature was raised to 200°C. 40 parts of maleic anhydride and 0.4 parts of hydroquinone were added in 4 batches with an interval of 50 min between each batch. The reaction was carried out at a constant temperature of 400 rpm for 4 h. After the reaction was completed, the temperature was lowered to 75°C, and anhydrous ethanol was added and stirred until completely miscible. The mixture was filtered while hot, and the filtrate was allowed to stand at 0°C for crystallization for 12 h. The rosin-based maleic anhydride adduct was obtained by vacuum filtration, washing, and vacuum drying.

[0061] S2. Dissolve 60 parts of rosin-based maleic anhydride adduct in 240 parts of anhydrous N,N-dimethylformamide to obtain a homogeneous and transparent solution. In a separate reaction vessel, add 16 parts of cystamine dihydrochloride and 24 parts of triethylamine to 120 parts of anhydrous N,N-dimethylformamide. Stir at room temperature for 1.5 h to fully neutralize and remove hydrochloric acid. Filter to remove the generated triethylamine hydrochloride precipitate to obtain an anhydrous DMF solution of free cystamine. Add the anhydrous DMF solution of cystamine to the above rosin-based maleic anhydride adduct solution at a uniform rate over 40 min. After the addition is complete, stir the reaction at room temperature in the dark for 3 h, then raise the temperature to 70℃ and stir at 500 rpm for 10 h. After the reaction is completed, add the reaction solution to deionized water and stir to precipitate. After filtration, wash and vacuum dry the precipitate to obtain a bifunctional crosslinking intermediate.

[0062] S3. Heat 120 parts of epoxidized soybean oil to 120°C, add 50 parts of the bifunctional crosslinking intermediate prepared in S2 and 2 parts of tetrabutylammonium bromide under stirring, and perform a grafting reaction at a constant temperature of 450 rpm for 6 hours under nitrogen protection. Cool down and discharge to obtain bio-based polyol.

[0063] Example 4

[0064] This embodiment provides a method for preparing biodegradable bio-based polyurethane foam, using the following technical solution:

[0065] By weight, 100 parts of bio-based polyol and 3 parts of ethylene glycol were mixed evenly, and 13 parts of functional filler were added. The mixture was ultrasonically dispersed at 60 kHz for 12 min to form a uniform suspension premix. Then, 4 parts of deionized water, 0.7 parts of dibutyltin dilaurate, and 2 parts of octylphenol polyoxyethylene ether were added to the premix. The mixture was premixed at 1000 rpm for 2 min to form a uniformly emulsified white material system. Finally, 165 parts of isophorone diisocyanate were poured into the white material and sheared at 3000 rpm for 12 s. The mixture was then poured into a mold preheated to 50 ℃ for free stretching and foaming. After the initial foaming was completed, the mixture was transferred to an 80 ℃ oven for deep curing and crosslinking for 18 h. The bio-based polyurethane foam was then demolded.

[0066] The preparation steps of the functional filler are as follows:

[0067] A1. Disperse 15 parts of nanocrystalline cellulose in 100 parts of 84wt% ethanol aqueous solution, sonicate at 50KHz for 32min at room temperature to form a suspension, and adjust the pH to 8.5 with ammonia; separately add 5 parts of 3-aminopropyltriethoxysilane to 36 parts of ethanol aqueous solution of the same concentration, stir at room temperature for 20min for pre-hydrolysis, add dropwise to the suspension at 3ml / min, reflux at 75℃ and 400rpm for 6h, and centrifuge, wash and freeze dry the product to obtain aminated nanocellulose powder;

[0068] A2. Disperse 20 parts of aminated nanocellulose powder in 105 parts of deionized water. Adjust the pH to 6.5 with hydrochloric acid while stirring at 300 rpm. Add 11 parts of 36wt% phytic acid aqueous solution dropwise at a uniform rate over 26 min. After the addition is complete, adjust the pH to 6.5 again. Heat to 70℃ and stir for 4.5 h. After filtration and washing with water until neutral, vacuum dry and grind through a 300-mesh sieve to obtain the functional filler.

[0069] The preparation steps of the bio-based polyol are as follows:

[0070] S1. Under nitrogen protection, 120 parts of rosin were heated to melt at 110°C, and then the temperature was raised to 200°C. 40 parts of maleic anhydride and 0.3 parts of hydroquinone were added in 4 batches, with an interval of 50 min between each batch. The reaction was carried out at a constant temperature of 400 rpm for 4.5 h. After the reaction was completed, the temperature was lowered to 75°C, and anhydrous ethanol was added and stirred until completely miscible. The mixture was filtered while hot, and the filtrate was allowed to stand at 0°C for crystallization for 14 h. The rosin-based maleic anhydride adduct was obtained by vacuum filtration, washing, and vacuum drying.

[0071] S2. Dissolve 60 parts of rosin-based maleic anhydride adduct in 240 parts of anhydrous N,N-dimethylformamide to obtain a homogeneous and transparent solution. In a separate reaction vessel, add 16 parts of cystamine dihydrochloride and 24 parts of triethylamine to 120 parts of anhydrous N,N-dimethylformamide. Stir at room temperature for 1.4 h to fully neutralize and remove hydrochloric acid. Filter to remove the generated triethylamine hydrochloride precipitate to obtain an anhydrous DMF solution of free cystamine. Add the anhydrous DMF solution of cystamine to the above rosin-based maleic anhydride adduct solution at a uniform rate over 40 min. After the addition is complete, stir the reaction at room temperature in the dark for 2.5 h, then raise the temperature to 70 °C and stir at 500 rpm for 10.2 h. After the reaction is complete, add the reaction solution to deionized water and stir to precipitate. After filtration, wash and vacuum dry the precipitate to obtain a bifunctional crosslinking intermediate.

[0072] S3. Heat 120 parts of epoxidized soybean oil to 120°C, add 45 parts of the bifunctional crosslinking intermediate prepared in S2 and 1.5 parts of tetrabutylammonium bromide under stirring, and perform a grafting reaction at a constant temperature of 450 rpm for 6.8 h under nitrogen protection. Cool down and discharge to obtain bio-based polyol.

[0073] Comparative Example 1

[0074] The difference between this comparative example and Example 4 is that cystamine dihydrochloride was not introduced in the preparation process of the bio-based polyol. That is, in step S2, an equimolar amount of hexamethylenediamine was used to replace cystamine dihydrochloride in the reaction to prepare the crosslinking intermediate. Other preparation conditions and raw material ratios are the same as in Example 4.

[0075] Comparative Example 2

[0076] The difference between this comparative example and Example 4 is that the rosin-based rigid framework was not introduced in the preparation process of the bio-based polyol, that is, step S1 was omitted. Specifically, in step S2, adipic acid, which provides an equimolar amount of carboxyl groups, was used to replace the rosin-based maleic anhydride adduct in the reaction to prepare the crosslinking intermediate. Other preparation conditions and raw material ratios were the same as in Example 4.

[0077] Comparative Example 3

[0078] The difference between this comparative example and Example 4 is that: the cellulose modified by ammoniation and phytic acid crosslinking was not used in the preparation of the functional filler, that is, steps A1 and A2 of the preparation of the functional filler were omitted. Specifically, unmodified nanocrystalline cellulose was directly added in the step of preparing biodegradable bio-based polyurethane foam, and other conditions were the same as in Example 4.

[0079] Comparative Example 4

[0080] The difference between this comparative example and Example 4 is that: phytic acid aqueous solution was not introduced for cross-linking and flame retardant modification during the preparation of the functional filler, that is, step A2 was omitted, and the aminated nanocellulose powder prepared in step A1 was directly added to the polyurethane foaming system as a functional filler. Other preparation conditions and raw material ratios are the same as in Example 4.

[0081] Comparative Example 5

[0082] The difference between this comparative example and Example 4 is that 3-aminopropyltriethoxysilane was not introduced for surface activation modification during the preparation of the functional filler. That is, in step A1, 3-aminopropyltriethoxysilane and ethanol aqueous solution for pre-hydrolysis were not added. After ultrasonic dispersion of nanocrystalline cellulose and pH adjustment, the phytic acid crosslinking operation in the subsequent step A2 was carried out directly. Other preparation conditions and raw material ratios were the same as in Example 4.

[0083] Performance testing

[0084] 1. Apparent density test

[0085] The apparent density (kg / m³) of the biodegradable bio-based polyurethane foams prepared in Examples 1-4 and Comparative Examples 1-5 was determined according to GB / T6343-2009 standard. 3 The test results are shown in Table 1.

[0086] 2. Compression performance test

[0087] The compressive strength (Kpa) of the biodegradable bio-based polyurethane foams prepared in Examples 1-4 and Comparative Examples 1-5 was tested according to GB / T8813-2008 standard. The test results are shown in Table 1.

[0088] 3. Dimensional stability test

[0089] The dimensional stability (%) of the biodegradable bio-based polyurethane foams prepared in Examples 1-4 and Comparative Examples 1-5 was tested according to GB / T8811-2008 standard. The test results are shown in Table 1.

[0090] 4. Flame retardant performance test

[0091] The flame retardant properties, i.e. oxygen index (%), of the biodegradable bio-based polyurethane foams prepared in Examples 1-4 and Comparative Examples 1-5 were tested according to GB / T2406.2-2009 standard. The test results are shown in Table 1.

[0092] 5. Biodegradability test

[0093] The biodegradability of biodegradable polyurethane foams prepared in Examples 1-4 and Comparative Examples 1-5 was tested according to the standard GB / T19277.1-2025, "Determination of the final aerobic biodegradability of materials under controlled composting conditions by measuring the amount of carbon dioxide released". The test period was 6 months, and the biodegradability (%) of the test samples was recorded.

[0094] Table 1

[0095] Test Project <![CDATA[Apparent density kg / m 3 > Compressive strength (kPa) Dimensional stability% Oxygen index (%) Biodegradation rate (%) Example 1 45.2 270.6 0.15 29.8 78.4 Example 2 44.5 276.2 0.13 30.6 81.5 Example 3 43.1 281.8 0.10 31.5 83.2 Example 4 42.3 285.4 0.08 32.4 85.6 Comparative Example 1 46.5 266.3 0.16 29.2 40.5 Comparative Example 2 54.8 177.5 0.68 28.9 76.5 Comparative Example 3 57.6 197.4 0.52 22.3 62.4 Comparative Example 4 48.2 263.7 0.21 24.1 73.2 Comparative Example 5 50.4 230.2 0.34 26.5 68.7

[0096] A comprehensive comparison and analysis of various test data shows that the biodegradable bio-based polyurethane foam prepared in the embodiments of this invention exhibits superior comprehensive advantages in core properties such as apparent density, compressive strength, dimensional stability, oxygen index, and biodegradation rate. Furthermore, with continuous optimization of the formulation, Example 4 achieved the optimal performance state. This invention, through precise molecular structure design, simultaneously introduces a rosin-based rigid tricyclic phenanthrene skeleton and dynamic reversible disulfide bonds into a bio-based polyol. Simultaneously, functionalized nanocellulose fillers are prepared through silane coupling agent amination modification and phytic acid crosslinking. This achieves a synergistic improvement in the mechanical load-bearing capacity, dimensional stability, flame retardancy and smoke suppression, and controllable biodegradability of the foam material. The core performance indicators of all embodiments are superior to the control examples, fully verifying the advanced nature and engineering practicality of this technical solution.

[0097] Due to adjustments in core process steps and raw material molecular structures, each comparative example exhibited performance degradation in different dimensions. Comparative Example 1, which replaced cystamine dihydrochloride with hexamethylenediamine, eliminated the dynamic disulfide bond degradation switch in the polyurethane crosslinking network. Although it still maintained good mechanical properties, flame retardant properties, and dimensional stability, its biodegradation rate dropped sharply, far lower than all other examples, fully demonstrating the core regulatory role of dynamic disulfide bonds in the controllable biodegradability of the material. Comparative Example 2, which replaced rosin-based maleic anhydride adduct with adipic acid, completely removed the rigid tricyclic phenanthrene backbone in the molecular chain, resulting in a significant weakening of the rigid support capacity of the polyurethane matrix, a significant reduction in compressive strength, and a disruption of the dynamic balance between foaming and gelation reactions. This led to poorer cell structure stability, a significant increase in apparent density, and a substantial deterioration in dimensional stability, verifying the crucial supporting role of the rosin rigid backbone in the material's mechanical properties and dimensional stability. Comparative Examples 3, 4, and 5 all lacked steps in the preparation process of the functional filler. Comparative Example 3 directly used unmodified nanocrystalline cellulose, resulting in severe agglomeration of the filler in the polyurethane matrix. This prevented the filler from effectively performing heterogeneous nucleation and mechanical reinforcement, and also lacked the support of the phytic acid-phosphorus-nitrogen synergistic flame retardant system. Consequently, the apparent density increased, mechanical properties decreased, and flame retardant performance showed the most significant deterioration. Comparative Example 4 omitted the phytic acid crosslinking modification step, missing the core phosphorus-nitrogen flame retardant components, leading to a significant decline in flame retardant performance. At the same time, the interfacial bonding force between the filler and the matrix decreased, and various properties deteriorated to varying degrees. Comparative Example 5 omitted the silane coupling agent amination modification step. The cellulose surface lacked active groups that could participate in the matrix crosslinking reaction, resulting in poor interfacial compatibility with the polyurethane matrix and decreased filler dispersion uniformity. Ultimately, this led to simultaneous deterioration of mechanical properties, dimensional stability, flame retardant performance, and biodegradability.

[0098] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A biodegradable bio-based polyurethane foam, characterized in that, The raw materials for its preparation, by weight, include 80-100 parts of bio-based polyol, 5-10 parts of chain extender, 5-10 parts of functional filler, 2-5 parts of deionized water foaming agent, 0.6-0.9 parts of catalyst, 1-3 parts of foam stabilizer and 140-170 parts of isocyanate; The isocyanate is selected from any one of polydiphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, or dicyclohexylmethane diisocyanate.

2. The biodegradable bio-based polyurethane foam according to claim 1, characterized in that, The preparation steps of the bio-based polyol are as follows: S1. Rosin is heated and melted under nitrogen protection. Maleic anhydride and hydroquinone are added in batches after the temperature is raised. The reaction is carried out at a constant temperature. After the reaction is completed, anhydrous ethanol is added after cooling. The mixture is filtered while hot and the filtrate is allowed to stand to crystallize. After post-treatment, rosin-based maleic anhydride adduct is obtained. S2. The rosin-based maleic anhydride adduct was dissolved in anhydrous N,N-dimethylformamide to obtain a homogeneous solution. Cystamine dihydrochloride and triethylamine were added to anhydrous N,N-dimethylformamide, stirred and neutralized at room temperature, and then filtered to obtain an anhydrous DMF solution of free cystamine. This solution was added dropwise to the rosin-based maleic anhydride adduct solution. After the addition was complete, the reaction was stirred at room temperature in the dark, and then heated and stirred at a constant temperature. After the reaction was completed, the reaction solution was precipitated and post-treated to obtain a bifunctional cross-linked intermediate. S3. Heat the epoxidized soybean oil, add a bifunctional cross-linking intermediate and a phase transfer catalyst while stirring, and perform a constant-temperature grafting reaction under nitrogen protection. Cool down and discharge the product to obtain a bio-based polyol.

3. The biodegradable bio-based polyurethane foam according to claim 2, characterized in that, In step S1, the ingredients are 100-120 parts by weight of rosin, 30-40 parts by weight of maleic anhydride and 0.2-0.4 parts by weight of hydroquinone, the reaction temperature is 190-200℃ and the crystallization temperature is 0-5℃.

4. The biodegradable bio-based polyurethane foam according to claim 2, characterized in that, In step S2, the ingredients are 50-60 parts by weight of rosin-based maleic anhydride adduct, 200-240 parts of anhydrous N,N-dimethylformamide, 12-16 parts of cystamine dihydrochloride, 18-24 parts of triethylamine, and 100-120 parts of anhydrous N,N-dimethylformamide, and the reaction temperature is 60-70℃.

5. The biodegradable bio-based polyurethane foam according to claim 2, characterized in that, In step S3, the ingredients are 100-120 parts by weight of epoxidized soybean oil, 30-50 parts of bifunctional crosslinking intermediate, and 1-2 parts of tetrabutylammonium bromide phase transfer catalyst, and the reaction temperature is 100-120℃.

6. The biodegradable bio-based polyurethane foam according to claim 1, characterized in that, The preparation steps of the functional filler are as follows: A1. Disperse nanocrystalline cellulose in an aqueous ethanol solution, sonicate to form a suspension, and adjust the pH value with ammonia. Separately, add 3-aminopropyltriethoxysilane to an aqueous ethanol solution of the same concentration, stir to pre-hydrolyze, and then add it dropwise to the suspension. Reflux the reaction, and the product is post-treated to obtain aminated nanocellulose powder. A2. Disperse aminated nanocellulose powder in deionized water, adjust the pH value with hydrochloric acid while stirring, add phytic acid aqueous solution dropwise, adjust the pH value again after the addition is complete, raise the temperature and stir the reaction at a constant temperature, and obtain the functional filler after post-treatment of the product.

7. The biodegradable bio-based polyurethane foam according to claim 6, characterized in that, In step A1, 10-15 parts by weight of nanocrystalline cellulose, 95-100 parts by weight of 80-85 wt% ethanol aqueous solution, 3-6 parts by weight of 3-aminopropyltriethoxysilane, and 30-40 parts by weight of ethanol aqueous solution of the same concentration are used; in step A2, 15-20 parts by weight of aminated nanocrystalline cellulose powder, 95-105 parts by weight of deionized water, and 8-12 parts by weight of 35-45 wt% phytic acid aqueous solution are used.

8. A method for preparing the biodegradable bio-based polyurethane foam according to any one of claims 1-7, characterized in that, Includes the following steps: Bio-based polyols and chain extenders are mixed evenly, functional fillers are added, and ultrasonic dispersion is performed to form a uniform suspension premix. Deionized water, catalyst, and foam stabilizer are added to the premix, and high-speed premixing is performed to form a uniformly emulsified white material system. Isocyanate is added to the white material, and after high-speed shearing and mixing, it is poured into a preheated mold for free extension and foaming. After the initial foaming is completed, deep curing and crosslinking are performed, and the bio-based polyurethane foam is obtained by demolding.

9. The biodegradable bio-based polyurethane foam according to claim 1, characterized in that, The chain extender is selected from any one of glycerol, ethylene glycol, 1,4-butanediol or pentaerythritol, and the catalyst is selected from at least one of dibutyltin dilaurate, stannous octoate and triethylenediamine.

10. The biodegradable bio-based polyurethane foam according to claim 1, characterized in that, The foam stabilizer is selected from at least one of fatty alcohol polyoxyethylene ether, octylphenol polyoxyethylene ether, and sodium dodecylbenzene sulfonate.