A process for the production of non-isocyanate polyurethane foams from castor oil and non-isocyanate polyurethane foams and uses

Abstract

This invention belongs to the field of bio-based polymer materials, specifically disclosing a method for preparing non-isocyanate polyurethane foam using castor oil. This invention utilizes castor oil to prepare non-isocyanate polyurethane foam, endowing the material with safety, self-antibacterial properties, and controllable biodegradability. Structural performance testing yielded a non-isocyanate polyurethane foam with an apparent density of 0.15~0.22 g / cm³. 3 It boasts a compressive strength of 0.25~0.41 MPa and a thermal conductivity as low as 0.037~0.042 W / (m·K), with no isocyanate residue. This material combines lightweight and high strength with excellent thermal insulation properties, making it widely applicable in plant growth substrates, insulation materials, automotive interiors, medical dressings, and cushioning packaging. It overcomes the application bottlenecks of traditional polyurethane materials, such as residue, poor degradation, susceptibility to bacteria, and difficulty in balancing mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of bio-based polymer materials technology, specifically relating to a method for preparing non-isocyanate polyurethane foam from castor oil, as well as the non-isocyanate polyurethane foam and its applications. Background Technology

[0002] Polyurethane (PU) foam, with its unique microporous structure, excellent mechanical properties, controllable density, and good chemical stability, has become one of the most widely used multifunctional materials in the field of polymer materials. By adjusting the types and ratios of isocyanates and polyols, polyurethane foam can exhibit various forms, ranging from soft and highly elastic to rigid and high-strength, and is widely used in many fields such as building energy-saving insulation, automotive interior sound absorption, packaging cushioning, and biomedical scaffolds. Especially in applications requiring a balance between lightweight, porous structure, and certain mechanical support, polyurethane foam has taken a dominant position due to its mature foaming process and cost advantages.

[0003] With the rapid development of facility agriculture and soilless cultivation technology, polyurethane foam materials, due to their excellent water and fertilizer retention capacity, suitable gas-liquid ratio, and lightweight and easy transportation characteristics, have been gradually introduced and developed as an ideal substitute for traditional soil, serving as plant growth substrates. For example, CN118126293A discloses a multidimensional plant growth substrate material. This scheme attempts to improve the nutrient solution adsorption capacity of the substrate by introducing bio-oil-based polyols into the polyurethane molecular chain and compounding it with diatomaceous earth fillers that have undergone complex modifications through multiple steps such as acid washing, silanization, and microemulsion coating. Furthermore, related prior art also discloses various modification strategies to improve the permeability, compressive modulus, or slow-release properties of the substrate by dispersing nanocellulose, straw powder, or porous inorganic particles. However, this method relies on toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), or polyisocyanate (PMDI) as core reactant monomers. The raw materials inherently have low safety, posing a risk of highly toxic residues. During long-term use of the substrate, these residues directly contact and inhibit plant seed germination, damage seedling root tip cells, and even affect the safety of agricultural products for consumption. Furthermore, the carbamate bonds formed by isocyanates have extremely high chemical stability and are very difficult to break in natural soil environments. The so-called "bio-based" aspect often only manifests in the polyol components, while the cross-linked network remains difficult to mineralize, ultimately easily disintegrating into microplastics that remain in the soil, causing long-term white pollution and contradicting the original intention of sustainable agriculture. Summary of the Invention

[0004] To address the technical challenges of existing polyurethane foams used in plant growth substrates, which rely on highly toxic isocyanate monomers, resulting in low raw material safety, residues that inhibit seed germination and damage plant roots, and the difficulty in natural mineralization due to their stable chemical structure, leading to long-term soil microplastic pollution, a non-isocyanate polyurethane foam material is developed. This material possesses non-toxic and environmentally friendly properties, excellent self-antibacterial function, good biodegradability potential, and suitable mechanical support strength.

[0005] The technical solution adopted by this invention to solve its technical problem is to provide a method for preparing non-isocyanate polyurethane foam from castor oil, comprising the following steps: Castor oil, carboxylic acid, and hydrogen peroxide were subjected to an epoxidation reaction in the presence of catalyst A to obtain epoxidized castor oil. The epoxidized castor oil was subjected to a cycloaddition reaction with carbon dioxide in the presence of catalyst B to obtain castor oil-based cyclic carbonate. The polyamine compound was functionalized by reacting it with a guanidine-modifying agent to obtain guanidine-functionalized polyamines. Bamboo powder is silanized with a silane coupling agent to obtain modified bamboo powder. The castor oil-based cyclic carbonate, the guanidine-functionalized polyamine, and the modified bamboo powder are mixed, a foaming agent is added, and a foaming and curing reaction is carried out to obtain the non-isocyanate polyurethane foam.

[0006] Preferably, the catalyst A is selected from at least one of sulfuric acid, phosphoric acid, p-toluenesulfonic acid, or a strong acid ion exchange resin.

[0007] Preferably, the epoxidation reaction is carried out at a temperature of 50-80°C, a pressure of 0.09-0.11 MPa, and a reaction time of 4-12 h.

[0008] Preferably, the molar ratio of hydrogen peroxide to carbon-carbon double bonds in castor oil is 1.0:1 to 1.5:1; The molar ratio of the carboxylic acid to hydrogen peroxide is 0.8:1 to 1.2:1.

[0009] Preferably, the catalyst B is selected from at least one of potassium bromide, potassium iodide, tetrabutylammonium bromide, and 1,8-diazabicycloundec-7-ene; The cycloaddition reaction is carried out at a pressure of 0.5~5.0 MPa, a temperature of 80~160℃, and a time of 2~12 h.

[0010] Preferably, the polyamine compound is selected from at least one of ethylenediamine, diethylenetriamine, triethylenetetramine, isophorone diamine, or polyetheramine; The guanidinizing agent is selected from at least one of guanidine hydrochloride, guanidine sulfate, dicyandiamide, guanidine nitrate, or guanidinoacetic acid.

[0011] Preferably, the molar ratio of the cyclic carbonate group in the castor oil-based cyclic carbonate to the amino group in the guanidine-functionalized polyamine is 1:0.8~1.5; Preferably, the amount of modified bamboo powder added is 5-28% of the total mass of castor oil-based cyclic carbonate and guanidine-functionalized polyamine.

[0012] Preferably, the foaming agent includes water, catalyst C, and a nonionic surfactant; The amount of water added is 1-10% of the mass of castor oil-based cyclic carbonate; Preferably, the catalyst C is selected from at least one of organic bases, organic zinc compounds, or quaternary ammonium salt ionic liquids.

[0013] This invention also provides a non-isocyanate polyurethane foam prepared from castor oil, which is prepared by the preparation method described in the above technical solution and has the following properties: Apparent density: 0.15~0.22 g / cm³ 3 The compressive strength is 0.25~0.41 MPa, and the thermal conductivity is 0.037~0.042 W / (m·K).

[0014] The present invention also provides the use of the non-isocyanate polyurethane foam prepared by the above preparation method or the non-isocyanate polyurethane foam described in the above technical solution in the preparation of thermal insulation materials, automotive interior parts, cushioning packaging materials, biomedical dressings or plant growth substrates.

[0015] This invention provides a method for preparing non-isocyanate polyurethane foam from castor oil, as well as the non-isocyanate polyurethane foam and its applications. The method for preparing non-isocyanate polyurethane foam from castor oil includes castor oil-based cyclic carbonate, guanidine-functionalized polyamine, modified bamboo powder, and a foaming agent. The modified bamboo powder is obtained by surface treatment of bamboo powder with a silane coupling agent, and the guanidine-functionalized polyamine is obtained by reacting a polyamine compound with a guanidine-functionalizing agent. This invention utilizes the stepwise polymerization of castor oil-based cyclic carbonate and guanidine-functionalized polyamine to construct a non-isocyanate polyurethane network, completely eliminating the use of highly toxic raw materials such as toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI) from the source. This effectively avoids the inhibition of plant seed germination and the toxic damage to seedling root tip cells caused by free isocyanate residues in traditional polyurethane foam, solving the core pain point of low substrate safety in facility agriculture. Furthermore, this invention introduces guanidine functional groups through guanidine-functionalized polyamines, endowing the material with broad-spectrum and long-lasting antibacterial activity. This significantly inhibits the growth of mold and pathogens in humid environments, preventing plant root rot. Simultaneously, silanization modification uniformly disperses bamboo powder and chemically bonds it to the polymer matrix, not only improving the foam's compressive strength and dimensional stability but also introducing biodegradable natural components, improving the material's final fate in soil environments, and alleviating the white pollution problems associated with traditional petroleum-based foams, such as difficulty in mineralization and the formation of microplastics. The results of the embodiments show that the non-isocyanate polyurethane foam provided by this invention is non-toxic and harmless, significantly improves the germination rate of plant seeds compared to traditional PU matrices, effectively inhibits Staphylococcus aureus and Escherichia coli, achieves a compressive strength of 0.25~0.41 MPa with excellent resilience, and exhibits controllable biodegradability in simulated soil burial experiments. In applications such as soilless cultivation, seed breeding, and ecological planting in facility agriculture, it can provide excellent water retention, air permeability, and mechanical support, while ensuring the safety of agricultural products and the sustainability of the soil ecological environment. It is significantly superior to existing plant growth substrates containing isocyanates and has great potential for green agricultural applications and market promotion value.

[0016] Furthermore, the non-isocyanate polyurethane foam material prepared by the method of this invention has excellent environmental friendliness, safety and non-toxicity, self-antibacterial properties and multi-functional applicability. Its application scope is not limited to plant growth substrates, but can also be widely extended to other fields with extremely high requirements for safety and environmental protection, such as facility agriculture, building energy conservation, automotive industry, logistics packaging and biomedicine, which have broad application prospects and market value. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 The non-isocyanate polyurethane foam prepared in Example 3. Detailed Implementation

[0019] In this invention, unless otherwise specified, all raw materials / processing reagents are commercially available products or conventional reagents well known to those skilled in the art; all equipment used in this invention is conventional equipment well known in the art; and all processing methods used in this invention are conventional processing methods in the art.

[0020] This invention discloses a method for preparing non-isocyanate polyurethane foam from castor oil, comprising the following steps: Castor oil, carboxylic acid, and hydrogen peroxide were subjected to an epoxidation reaction in the presence of catalyst A to obtain epoxidized castor oil. The epoxidized castor oil was subjected to a cycloaddition reaction with carbon dioxide in the presence of catalyst B to obtain castor oil-based cyclic carbonate. The polyamine compound was functionalized by reacting it with a guanidine-modifying agent to obtain guanidine-functionalized polyamines. Bamboo powder is silanized with a silane coupling agent to obtain modified bamboo powder. The castor oil-based cyclic carbonate, the guanidine-functionalized polyamine, and the modified bamboo powder are mixed, a foaming agent is added, and a foaming and curing reaction is carried out to obtain the non-isocyanate polyurethane foam.

[0021] Through the above steps, this invention achieves efficient utilization of castor oil and prepares environmentally friendly non-isocyanate polyurethane foam with no isocyanate residue.

[0022] In this invention, catalyst A is preferably selected from at least one of sulfuric acid, phosphoric acid, p-toluenesulfonic acid, or a strong acidic ion exchange resin. When catalyst A is composed of multiple substances mentioned above, there are no special requirements for the ratio of each catalyst A; any ratio is acceptable. In this invention, the core function of catalyst A is to catalyze the epoxidation reaction of castor oil with hydrogen peroxide, accelerate the reaction rate, promote the conversion of carbon-carbon double bonds in castor oil molecules into epoxy groups, and ensure that the epoxidation reaction proceeds fully. In this invention, the amount of catalyst A added is preferably 1.5 to 2.5% of the mass of castor oil. In this invention, controlling the amount of catalyst A within the aforementioned range ensures both the catalytic effect on the epoxidation reaction and provides a sufficient acidic catalytic environment for the complete epoxidation of carbon-carbon double bonds in castor oil, while avoiding raw material waste due to excessive addition. It also avoids the problems of increased side reactions and more difficult product post-processing caused by excessive catalyst. If the addition amount is less than 1.5% of the castor oil mass, the catalytic activity is insufficient, the reaction rate is too slow, and the epoxidation reaction is incomplete. If the addition amount is more than 2.5% of the castor oil mass, it easily triggers side reactions such as excessive decomposition of hydrogen peroxide and carbonization of castor oil. In this invention, different types of catalyst A can all provide the acidic catalytic environment required for the epoxidation reaction, and their catalytic mechanisms are similar, all effectively activating hydrogen peroxide and promoting the epoxidation of carbon-carbon double bonds. Therefore, when multiple catalysts are used in combination, their specific ratios are not limited, and any ratio can achieve the catalytic effect of this invention.

[0023] In this invention, the temperature of the epoxidation reaction is preferably 50-80°C, more preferably 60-80°C, and even more preferably 60°C. The pressure of the epoxidation reaction is preferably 0.09-0.11 MPa. The time of the epoxidation reaction is preferably 4-12 h, more preferably 6-8 h, and even more preferably 8 h. In this invention, the core functions of reaction temperature, pressure, and time are to ensure the smooth progress of the epoxidation reaction, control the reaction rate, ensure the complete epoxidation of carbon-carbon double bonds, and avoid side reactions. Controlling the reaction conditions within the above ranges ensures the catalytic activity of catalyst A, allowing the epoxidation reaction to proceed fully, while avoiding side reactions such as excessively rapid decomposition of hydrogen peroxide and carbonization of castor oil due to excessively high temperature or time, and also avoids problems such as excessively slow reaction rates and incomplete reactions due to excessively low temperature or short time. In this invention, the preferred reaction pressure is 0.09~0.11 MPa, eliminating the need for high-pressure reaction equipment, simplifying the production process, reducing equipment investment and energy consumption, and meeting the requirements of the epoxidation reaction under normal pressure. No pressure parameter adjustment is needed between different batches, and there are no additional pressure limitations. In a specific embodiment of this invention, the epoxy value can be stably maintained within the range of 0.29~0.33 mol / 100 g, meeting the requirements of the subsequent cycloaddition reaction. After the epoxidation reaction, the process preferably includes allowing the mixture to stand and separate into layers, discarding the aqueous phase, washing the organic phase with deionized water until neutral, and then vacuum drying to obtain epoxidized castor oil. In this invention, the vacuum drying conditions are conventional in the art, as long as sufficient moisture and volatile components are removed. In a specific embodiment of this invention, the vacuum drying conditions can be 80°C and -0.08 MPa for 2 h.

[0024] In this invention, the hydrogen peroxide is preferably added to the reaction system in batches or dropwise in the form of an aqueous solution. In this invention, the hydrogen peroxide aqueous solution is preferably a 30% (w / w) hydrogen peroxide aqueous solution. In this invention, the dropwise addition time of the hydrogen peroxide aqueous solution is preferably 1-1.5 h, more preferably 1 h. In this invention, the core function of hydrogen peroxide is as an oxidant in the epoxidation reaction, providing an oxygen source for the epoxidation of carbon-carbon double bonds in castor oil molecules, thus promoting the epoxidation reaction. In this invention, the amount of the 30% (w / w) hydrogen peroxide aqueous solution added is 32-48% of the mass of castor oil, corresponding to a molar ratio of hydrogen peroxide to carbon-carbon double bonds in castor oil of 1.0:1-1.5:1. In this invention, the amount of hydrogen peroxide aqueous solution added is controlled within the aforementioned range. This ensures sufficient oxygen supply for the epoxidation of carbon-carbon double bonds, allowing the epoxidation reaction to proceed fully, while preventing the decomposition and waste of hydrogen peroxide due to excess, and avoiding incomplete reaction due to insufficient hydrogen peroxide. Controlling the dropping time to 1-1.5 hours allows hydrogen peroxide to be uniformly dispersed in the reaction system, ensuring sufficient contact with castor oil and carboxylic acid, guaranteeing a stable reaction and preventing side reactions caused by excessively high local concentrations. In this invention, the hydrogen peroxide aqueous solution can be added in batches or dropwise. Both methods achieve uniform addition of hydrogen peroxide, with the core objective of avoiding excessively high local concentrations. Therefore, there are no special limitations on the choice between the two addition methods, and adjustments can be made flexibly according to actual production needs. If multiple addition methods are combined, there are no special requirements for their specific proportions; any combination can achieve the effects of this invention. In this invention, a 30% (w / w) hydrogen peroxide aqueous solution is chosen because at this concentration, the oxidizing activity of hydrogen peroxide is moderate, which can meet the requirements of the epoxidation reaction while reducing its own decomposition. Furthermore, this concentration perfectly matches the actual dosage used in the examples, eliminating the need for additional concentration adjustments. In this invention, the addition of the hydrogen peroxide aqueous solution is preferably achieved by real-time monitoring of the reaction system temperature, maintaining the reaction temperature within a preset range. If the temperature exceeds the preset upper limit, the dropping rate is immediately slowed down or the dropping is paused, while the stirring speed is appropriately increased to dissipate heat promptly and prevent a sudden temperature rise that could trigger side reactions. To avoid rapid decomposition of hydrogen peroxide and subsequent material overflow, the dropping rate, reaction temperature, and catalyst A dosage must be controlled, and the system must be well stirred. If signs of material overflow appear, the dropping is immediately stopped, heating is turned off, and operation is resumed only after the system stabilizes, ensuring a stable and controllable reaction and the stable acquisition of a qualified intermediate.

[0025] In this invention, the molar ratio of the carboxylic acid to hydrogen peroxide is preferably 0.8:1 to 1.2:1, more preferably 0.9:1 to 1.1:1, and even more preferably 1.0:1; the carboxylic acid is preferably a short-chain fatty acid, more preferably one or more of acetic acid, formic acid, or propionic acid. In this invention, the core function of the molar ratio of carboxylic acid to hydrogen peroxide is to promote the decomposition of hydrogen peroxide, improve the efficiency of the epoxidation reaction, and reduce the formation of byproducts. Controlling the molar ratio of carboxylic acid to hydrogen peroxide at 0.8:1 to 1.2:1 in this invention maximizes the decomposition of hydrogen peroxide into reactive oxygen species while avoiding the increased difficulty of subsequent product washing due to excessive carboxylic acid or the low reaction efficiency due to insufficient carboxylic acid. In this invention, the carboxylic acid is selected from one or more of acetic acid, formic acid, or propionic acid. When the carboxylic acid is multiple of the above substances, this invention does not have special requirements for the ratio of each carboxylic acid; any ratio is acceptable. Since acetic acid, formic acid, and propionic acid are all organic acids, their core function is to promote the decomposition of hydrogen peroxide and provide the acidic environment required for the epoxidation reaction. Their catalytic mechanisms are similar, and the reaction effect will not be affected by different mixing ratios. Therefore, there is no limitation on their mixing ratio.

[0026] In this invention, catalyst B is preferably selected from at least one of potassium bromide, potassium iodide, tetrabutylammonium bromide, and 1,8-diazabicycloundec-7-ene (DBU), more preferably tetrabutylammonium bromide or DBU, and even more preferably tetrabutylammonium bromide. When catalyst B is multiple of the above substances, this invention does not have special requirements on the ratio of each catalyst B, and any ratio is acceptable. In this invention, the core function of catalyst B is to catalyze the cycloaddition reaction of epoxidized castor oil with carbon dioxide, lower the activation energy of the reaction, promote the combination of epoxy groups with carbon dioxide to convert them into cyclic carbonate groups, and at the same time improve the conversion rate of the cycloaddition reaction. In this invention, the amount of catalyst B added is preferably 2-4% of the mass of epoxidized castor oil. In this invention, controlling the amount of catalyst B within the aforementioned range ensures catalytic activity, accelerates the cycloaddition reaction rate, and increases the yield of cyclic carbonates, while avoiding raw material waste due to excessive addition. It also avoids problems such as increased side reactions and more difficult product post-processing caused by excessive catalyst. If the addition amount is less than 2% of the mass of epoxidized castor oil, the catalytic activity is insufficient, resulting in a low cycloaddition conversion rate. If the addition amount is more than 4% of the mass of epoxidized castor oil, it easily triggers side reactions such as epoxy group degradation, affecting product quality. In this invention, different types of catalyst B can effectively activate epoxy groups and promote carbon dioxide insertion reactions. Their catalytic mechanisms are similar, and they can all achieve efficient cycloaddition reactions. Therefore, when multiple catalysts are used in combination, their specific ratios are not limited; any ratio can achieve the catalytic effect of this invention. In a specific embodiment of this invention, tetrabutylammonium bromide is selected as catalyst B. This catalyst has high catalytic efficiency, mild reaction conditions, and a cycloaddition conversion rate of up to 92.3%, making it more suitable for large-scale industrial production.

[0027] In this invention, the pressure of the cycloaddition reaction is preferably 0.5~5.0 MPa, more preferably 2.0~5.0 MPa, and even more preferably 2.0 MPa. The temperature of the cycloaddition reaction is preferably 80~160℃, more preferably 120~160℃, and even more preferably 120℃. The time of the cycloaddition reaction is preferably 2~12 h, more preferably 6~8 h, and even more preferably 6 h. In this invention, the key functions of the pressure, temperature, and time of the cycloaddition reaction are to ensure the complete cycloaddition reaction between the epoxy group and carbon dioxide, thereby improving the yield and purity of the cyclic carbonate. Within the range of the above reaction conditions, this invention ensures that carbon dioxide has appropriate solubility and reactivity, and also ensures the catalytic activity of catalyst B, allowing the epoxy group to be fully converted into cyclic carbonate groups. Simultaneously, it avoids problems such as increased equipment requirements and product degradation due to excessively high pressure, high temperature, or long time, and also avoids problems such as excessively low reaction rate and low conversion rate due to excessively low pressure, low temperature, or short time. In this invention, industrial-grade carbon dioxide (purity ≥99.5%) is used, requiring no special purification. Different batches of industrial-grade carbon dioxide can meet the reaction requirements, and there are no additional limitations on its purity. In this invention, after the cycloaddition reaction, the product is preferably vacuum-dried to obtain castor oil-based cyclic carbonate. The vacuum drying conditions described in this invention are conventional conditions in the art, and this invention does not particularly limit the specific drying conditions. In a specific embodiment of this invention, the vacuum drying conditions can be 80°C and -0.08 MPa for 1 h.

[0028] In this invention, the polyamine compound is preferably at least one selected from ethylenediamine, diethylenetriamine, triethylenetetramine, isophorone diamine, or polyetheramine, more preferably diethylenetriamine, isophorone diamine, or polyetheramine D230, and even more preferably diethylenetriamine. When the polyamine compound is multiple of the above substances, this invention does not have special requirements on the ratio of each polyamine compound, and any ratio is acceptable. In this invention, the core function of the polyamine compound is to undergo a functionalization modification reaction with the guanidine-modifying agent, introduce guanidine groups, and prepare guanidine-functionalized polyamines. Simultaneously, the amino groups in its molecule can undergo a ring-opening reaction with the cyclic carbonate groups in castor oil-based cyclic carbonates to form a cross-linked structure, constituting the skeleton of the polyurethane foam and determining the mechanical properties of the foam. In this invention, the mass ratio of the guanidine-modifying agent to the polyamine compound is preferably 110:100 to 130:100. In this invention, controlling the mass ratio of the polyamine compound to the guanidinizing agent within the aforementioned range ensures sufficient reaction between the polyamine compound and the guanidinizing agent, resulting in the preparation of guanidinofunctionalized polyamines with qualified amino content. It also avoids the possibility of unreacted amino residues due to excessive polyamine compound, affecting foam stability, or incomplete guanidinization reaction due to insufficient polyamine compound, affecting subsequent ring-opening crosslinking reactions. In this invention, different types of polyamine compounds all contain amino groups and can undergo functionalization modification reactions with the guanidinizing agent. Furthermore, all amino groups participate in subsequent ring-opening reactions, exhibiting consistent core functions and similar catalytic mechanisms. Therefore, when multiple polyamine compounds are used in combination, their specific ratios are not limited, and any ratio can achieve the effects of this invention. In this invention, the preferred preparation steps for guanidinofunctionalized polyamines include: adding the polyamine compound and the guanidinizing agent to a solvent, heating and stirring to carry out the functionalization modification reaction, and removing the solvent and unreacted raw materials by vacuum distillation after the reaction to obtain the guanidinofunctionalized polyamine. In this invention, the preferred heating temperature is 65-85°C. In this invention, the vacuum distillation conditions are conventional conditions in the art, and this invention does not impose any special limitations, as long as the solvent and unreacted raw materials can be removed.

[0029] In the preparation of the guanidinofunctionalized polyamine, alcohols or glycols are preferably used as solvents, and more preferably anhydrous ethanol, isopropanol, or ethylene glycol. In this invention, alcohols or glycols have good compatibility with the polyamine compound and the guanidinolation reagent, and have moderate boiling points, facilitating subsequent removal by vacuum distillation. They also do not participate in the reaction and do not affect the purity of the product. In this invention, to ensure precise control of the molar ratio of castor oil-based cyclic carbonate to guanidinofunctionalized polyamine, the amino content of the prepared guanidinofunctionalized polyamine needs to be determined. Acid-base titration is preferred for determining the amino content. The subsequent feed amount is adjusted based on the determination results to ensure that the molar ratio of cyclic carbonate groups to amino groups meets the requirements.

[0030] In this invention, the guanidinizing agent is preferably at least one selected from guanidine hydrochloride, guanidine sulfate, dicyandiamide, guanidine nitrate, or guanidinoacetic acid, more preferably guanidine hydrochloride, guanidine sulfate, or dicyandiamide, and even more preferably guanidine hydrochloride. When the guanidinizing agent is multiple of the above substances, this invention does not have special requirements on the ratio of each guanidinizing agent, and any ratio is acceptable. In this invention, the core function of the guanidinizing agent is to undergo a functionalization modification reaction with the polyamine compound, introducing a guanidin group into the polyamine molecule, endowing the guanidin-functionalized polyamine with good antibacterial activity. At the same time, the amino group in the guanidin group can participate in the subsequent ring-opening reaction with the cyclic carbonate group, further improving the crosslinking density and mechanical properties of the foam. In this invention, the mass ratio of the guanidinizing agent to the polyamine compound is 110:100 to 130:100. In this invention, the mass ratio of guanidinizing agent to polyamine compound is controlled within the aforementioned range. This ensures sufficient reaction between the guanidinizing agent and polyamine compound, introducing adequate guanidin groups, while avoiding unreacted reagent residue due to excessive guanidinizing agent, which increases the difficulty of post-processing, or insufficient guanidinizing agent, which leads to insufficient guanidin group introduction and affects the antibacterial and mechanical properties of the foam. In this invention, different types of guanidinizing agents all contain guanidin groups and can undergo functionalization modification reactions with polyamine compounds. They share the same core function and similar catalytic mechanisms. Therefore, when multiple guanidinizing agents are used in combination, their specific ratio is not limited; any ratio can achieve the effects of this invention.

[0031] In this invention, the molar ratio of the cyclic carbonate group in the castor oil-based cyclic carbonate to the amino group in the guanidine-functionalized polyamine is 1:0.8~1.5, preferably 1:1.0~1.5, and more preferably 1:1.0. The core function of this molar ratio in this invention is to ensure that the cyclic carbonate group and the amino group can fully undergo a ring-opening reaction to form a uniform and stable cross-linked structure, thereby determining the mechanical properties, cell structure, and stability of the non-isocyanate polyurethane foam. In this invention, controlling this molar ratio within the range of 1:0.8~1.5 ensures that the cyclic carbonate group and the amino group fully react to form a dense and uniform cross-linked network, while avoiding unreacted amino residues due to excessive amino groups, which could reduce the foam's water resistance and stability, or insufficient amino groups that could prevent complete reaction of the cyclic carbonate group, resulting in excessively low cross-linking density and poor mechanical properties. In this invention, the content of cyclic carbonate groups and amino groups in castor oil-based cyclic carbonates and guanidine-functionalized polyamines prepared in different batches may vary slightly. It is sufficient to adjust the amount of both according to the actual content so that the molar ratio falls within the above range. There are no special requirements for the specific adjustment ratio.

[0032] In this invention, the modified bamboo powder is preferably added at 5-28% of the total mass of castor oil-based cyclic carbonate and guanidine-functionalized polyamine, more preferably 12-28%. The core function of the modified bamboo powder in this invention is as a filler, enhancing the mechanical properties of non-isocyanate polyurethane foam while simultaneously imparting good biodegradability, reducing production costs, and achieving resource recycling. Controlling the amount of modified bamboo powder added within the range of 5-28% ensures its full reinforcing and degradation effects, improving the foam's mechanical properties and environmental friendliness, while avoiding excessive addition leading to bamboo powder agglomeration, causing pores and defects within the foam, affecting its appearance and mechanical properties, or insufficient addition preventing it from fully exerting its function. In this invention, the modified bamboo powder is prepared from bamboo powder via a silanization reaction. Different batches of modified bamboo powder may have slight differences in dispersibility and compatibility; as long as the addition amount is controlled within the above range, the effects of this invention can be achieved, and there are no special limitations on specific batches of modified bamboo powder.

[0033] In this invention, the bamboo powder is subjected to a silanization reaction with a silane coupling agent to obtain modified bamboo powder. The preferred process of silanizing the bamboo powder with the silane coupling agent includes: first, sieving the bamboo powder to remove impurities and large particles to ensure uniform particle size; then, adding the sieved bamboo powder to deionized water and ultrasonically dispersing it to ensure uniform dispersion and prevent agglomeration; subsequently, adding a predetermined amount of silane coupling agent and controlling the temperature while stirring to carry out the silanization reaction, allowing the silane coupling agent to fully react with the hydroxyl groups on the surface of the bamboo powder; after the reaction, filtering and washing the product to remove unreacted silane coupling agent and impurities; and finally, vacuum drying to obtain modified bamboo powder. In this invention, the ultrasonic dispersion is preferably performed using an ultrasonic cleaner with a power of 200~400W, and the ultrasonic dispersion time is preferably 25~35min to ensure that the bamboo powder is uniformly dispersed in the aqueous phase and to avoid agglomeration; the temperature of the silanization reaction is preferably 55~65℃, and the reaction time is preferably 2~4h; the temperature of the vacuum drying is preferably 75~85℃, the vacuum degree is preferably -0.07~-0.09 MPa, and the drying time is preferably 3~5h.

[0034] In this invention, the silane coupling agent is preferably KH-550, KH-560, or KH-570. When the silane coupling agent is multiple of the above substances, this invention does not have special requirements on the ratio of each silane coupling agent, and any ratio is acceptable. In this invention, before the bamboo powder undergoes the silanization reaction, it is preferable to further include the steps of passing it through an 80-mesh sieve and adding deionized water for ultrasonic dispersion. In this invention, after the silanization reaction is completed, it is preferable to further include filtration, washing, and vacuum drying. In this invention, the vacuum drying conditions are conventional conditions in the art. In this invention, the core function of the silane coupling agent is to modify the surface of the bamboo powder, improve the compatibility of bamboo powder with organic systems such as castor oil-based cyclic carbonates and guanidine-functionalized polyamines, prevent bamboo powder agglomeration, enhance the bonding force between bamboo powder and the foam matrix, and thus improve the mechanical properties and stability of the foam. In this invention, the amount of silane coupling agent added is 4-8% of the mass of bamboo powder. In this invention, controlling the amount of silane coupling agent added within the aforementioned range ensures the modification effect, allowing sufficient organic groups to form on the bamboo powder surface and improving its compatibility with the organic system. It also avoids the effects of excessive addition leading to silane coupling agent agglomeration and affecting the modification effect, or insufficient addition resulting in inadequate modification and continued agglomeration of the bamboo powder. In this invention, KH-550, KH-560, and KH-570 are all commonly used silane coupling agents. They can all react with the hydroxyl groups on the bamboo powder surface to form chemical bonds. Simultaneously, the organic groups at their other ends are compatible with the organic system. Their core functions and modification mechanisms are similar; therefore, when multiple silane coupling agents are used in combination, their specific ratios are not limited, and any ratio can achieve the modification effect of this invention.

[0035] In this invention, the foaming aid includes water, catalyst C, and a nonionic surfactant. The amount of water added is 1-10% of the mass of castor oil-based cyclic carbonate, preferably 5-10%, and more preferably 5%. In this invention, the core function of water is as a physical foaming agent. During the foaming and curing reaction, it reacts with active groups in the system to generate gas, causing the reaction system to foam, forming a foam structure, and determining the foam density and pore size. In this invention, controlling the amount of water added within the range of 1-10% of the mass of castor oil-based cyclic carbonate ensures that an appropriate amount of gas is generated, forming a uniform and fine pore structure, guaranteeing the foam's heat insulation and buffering performance. It also avoids excessive gas leading to oversized pores and pore collapse, or insufficient gas leading to excessive foam density, which would fail to meet practical application requirements. In this invention, water, as the core component of the foaming aid, has a single and clear function; deionized water from different sources can meet the requirements, and there are no special limitations on it. In this invention, the nonionic surfactant is preferably an organosilicon nonionic surfactant. In this invention, the nonionic surfactant functions to stabilize the foam cells and improve their uniformity, resulting in fine, uniform foam cells that are less prone to collapse. The preferred amount of the added organosilicon nonionic surfactant is 1.0-3.0% of the mass of castor oil-based cyclic carbonate, more preferably 1.5-2.5%, and even more preferably 2.0%.

[0036] In this invention, the preferred amount of catalyst C is 0.8-1.5% of the mass of castor oil-based cyclic carbonate. Controlling the amount of catalyst C within this range ensures catalytic efficiency, accelerates the ring-opening reaction and foaming / curing rate, and enables rapid foam formation. It also avoids excessive addition leading to an overly rapid reaction rate, uneven cell structure, or cell collapse, or insufficient addition resulting in an overly slow reaction rate, incomplete foam curing, and poor mechanical properties. In this invention, catalyst C is selected from at least one of organic bases, organozinc compounds, or quaternary ammonium salt ionic liquids, preferably DBU, zinc isooctanoate, or tetrabutylammonium bromide, more preferably DBU. When catalyst C is multiple substances from the above categories, there are no special requirements for the ratio of each catalyst C; any ratio is acceptable. In this invention, the core function of catalyst C is to catalyze the ring-opening reaction between castor oil-based cyclic carbonate and guanidine-functionalized polyamine, accelerating the foaming / curing reaction rate, shortening the reaction time, and promoting complete reaction to ensure rapid foam curing and improve the structural stability of the foam. In this invention, different types of catalyst C can effectively activate cyclic carbonate groups and amino groups, accelerate the ring-opening reaction rate, and have similar catalytic mechanisms. They can all achieve efficient foaming and curing reactions. Therefore, when multiple catalysts are used in combination, there is no limitation on their specific ratio, and any ratio can achieve the catalytic effect of this invention.

[0037] In this invention, the castor oil-based cyclic carbonate, the guanidine-functionalized polyamine, and the modified bamboo powder are mixed, a foaming agent is added, and a foaming and curing reaction is carried out to obtain the non-isocyanate polyurethane foam. In this invention, the foaming and curing reaction time is preferably 2-4 hours, more preferably 3 hours. In this invention, the foaming and curing reaction temperature is preferably 80-90°C. In this invention, the above reaction conditions enable the foam to form rapidly while ensuring structural stability and excellent mechanical properties. In this invention, controlling the reaction time within the range of 2-4 hours ensures the catalytic activity of catalyst C, accelerates the foaming and curing rate, and forms a uniform and fine cell structure, while avoiding foam degradation and aging due to excessively high temperature and time, or incomplete curing and easy deformation due to excessively low temperature and time. In this invention, the foaming and curing reaction can be carried out in a conventional mold. Molds made of different materials, such as cast aluminum, steel, and acrylic sheets, can meet the requirements, and there is no special limitation on the mold material. Before using the mold, a release agent can be applied. Different types of release agents can achieve the demolding effect, and there is no special limitation on their type.

[0038] This invention provides a non-isocyanate polyurethane foam prepared from castor oil, obtained by the preparation method described in the above technical solution. The core advantages of this non-isocyanate polyurethane foam are that it is odorless, leaves no isocyanate residue, is environmentally friendly, and possesses excellent mechanical properties, antibacterial properties, and biodegradability. Its isocyanate-free characteristic avoids the toxic residue problems of traditional isocyanate-based polyurethane foams, resulting in higher safety and suitability for applications with high safety requirements, such as biomedicine and automotive interiors. Its excellent mechanical properties enable it to meet practical application needs such as insulation, cushioning, and automotive interiors. Its excellent antibacterial properties inhibit the growth of harmful bacteria such as Escherichia coli and Staphylococcus aureus, expanding its application scenarios. Its excellent biodegradability allows it to completely degrade into harmless substances in the natural environment, leaving no microplastic residue, reducing environmental pollution, and conforming to the concept of green development. In this invention, the performance parameters of the foam are all verified based on examples, specifically: apparent density 0.15~0.22 g / cm³. 3 The foam exhibits a compressive strength of 0.25~0.41 MPa, a thermal conductivity of 0.037~0.042 W / (m·K), an antibacterial rate of ≥87% against both Escherichia coli and Staphylococcus aureus, and a degradation rate of ≥32% after 90 days of simulated soil burial. This performance range can meet the needs of different application scenarios. Foams prepared in different batches can all fall within the above range as long as the preparation method of this invention is strictly followed, and there are no special limitations on specific batches.

[0039] This invention provides the use of the non-isocyanate polyurethane foam in the preparation of thermal insulation materials, automotive interior parts, cushioning packaging materials, biomedical dressings, or plant growth substrates. When the foam is used for these multiple applications, this invention does not specify a particular application ratio; any ratio is acceptable. The core application of this foam in this invention is based on its advantages of being non-toxic, environmentally friendly, possessing excellent mechanical properties, antibacterial properties, and biodegradability, making it suitable for the needs of different fields. The thermal insulation material is preferably used for building insulation or appliance insulation because the foam has good thermal insulation performance and is environmentally friendly, capable of replacing traditional insulation materials and reducing environmental pollution. The cushioning packaging material is preferably used for electronic product cushioning packaging because the foam has good cushioning performance, effectively protecting electronic products, and is biodegradable, reducing packaging waste pollution. Furthermore, its good antibacterial and biocompatibility make it suitable for preparing biomedical dressings, and its biodegradability makes it suitable for preparing plant growth substrates without polluting the soil. In this invention, when the foam is used for different purposes, there is no need to adjust the performance parameters. It can be processed into the corresponding shape according to the requirements of the purpose. There is no conflict between different purposes. Therefore, the proportion of mixed application of multiple purposes is not limited and can be flexibly adjusted according to actual production needs. Figure 1 The attached figure shows a physical image of the non-isocyanate polyurethane foam prepared in Example 3 of the present invention. As can be clearly seen from the attached figure, the non-isocyanate polyurethane foam prepared by the present invention has a regular appearance, no collapsed cells or cracks, uniform cell distribution, good macroscopic morphology, and exhibits excellent structural stability.

[0040] To further illustrate the present invention, the following detailed description, in conjunction with the accompanying drawings and embodiments, describes a non-isocyanate polyurethane foam prepared from castor oil, its preparation method, and its application, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0041] Example 1 This embodiment provides a method for preparing a non-isocyanate polyurethane foam product A, the specific steps of which are as follows: 1. Preparation of epoxidized castor oil 100g castor oil (industrial grade, Shandong Huiying Chemical, double bond content ≈ 0.32 mol), 23.0 g acetic acid (analytical grade, Sinopharm Group, molar ratio of hydrogen peroxide to hydrogen peroxide 1.0:1), and 2g p-toluenesulfonic acid (catalyst A, analytical grade, Aladdin reagent) were stirred evenly with an electric stirrer (JJ-1 type precision booster). The mixture was heated to 60℃ and heated to 0.09 MPa. 43.5 g of 30% hydrogen peroxide aqueous solution (Sinopharm Group, molar ratio of hydrogen peroxide to carbon-carbon double bonds in castor oil 1.2:1) was slowly added dropwise through a dropping funnel over 1 h. After the addition was complete, the reaction was continued at this temperature for 8 h. After the reaction was complete, the mixture was allowed to stand and separate into layers. The aqueous phase was discarded, and the organic phase was washed with deionized water until neutral. The organic phase was then vacuum dried in a vacuum drying oven (DZF-6050 type vacuum drying oven) at 80℃, -0.08 MPa for 2 h to obtain epoxidized castor oil. The epoxy value was measured to be 0.31. mol / 100g. The epoxy value described in this invention is determined according to the hydrochloric acid-acetone method in GB / T1677-2008 "Determination of Epoxy Value of Plasticizers".

[0042] 2. Preparation of castor oil-based cyclic carbonates 100 g of the epoxidized castor oil prepared above was added to a high-pressure reactor, along with 3 g of tetrabutylammonium bromide (catalyst B, analytical grade, Aladdin reagent). The reactor was sealed, and the air inside was replaced with carbon dioxide three times. Then, carbon dioxide was introduced to a pressure of 2.0 MPa, and the temperature was raised to 120 °C. The mixture was stirred for 6 h. After the reaction was completed, the temperature was lowered to room temperature, the pressure was released, the product was removed, and vacuum dried (80 °C, -0.08 MPa) for 1 h to obtain castor oil-based cyclic carbonate. The cycloaddition conversion rate was measured to be 92.3%.

[0043] 3. Preparation of guanidinofunctionalized polyamines 50 g of diethylenetriamine (analytical grade, Sinopharm Group) and 60 g of guanidine hydrochloride (analytical grade, Aladdin reagent) were added to 100 mL of anhydrous ethanol as solvent. The mixture was heated to 70 °C and stirred for 4 h to carry out the functionalization modification reaction. After the reaction was completed, the solvent and unreacted raw materials were removed by vacuum distillation using a rotary evaporator (RE-52AA type) to obtain guanidine-functionalized polyamines. The amino content was measured to be 8.2 mmol / g.

[0044] 4. Preparation of modified bamboo powder Take 50g of bamboo powder (Zhejiang Anji Bamboo Art, passed through an 80-mesh sieve), add 200 mL of deionized water, and ultrasonically disperse for 30 min using an ultrasonic cleaner (KQ-500DE type). Add 3 g of silane coupling agent KH-550 (Nanjing Chuangshi Chemical), heat to 60℃, and stir to carry out silanization reaction for 3 h. After the reaction is completed, filter, wash, and vacuum dry (80℃, -0.08 MPa) for 4 h to obtain modified bamboo powder.

[0045] 5. Foaming and curing of non-isocyanate polyurethane foam Using a high-speed disperser (GFJ-1100 type), 100 g of castor oil-based cyclic carbonate, 34.9 g of guanidine-functionalized polyamine (molar ratio of cyclic carbonate groups in castor oil-based cyclic carbonate to amino groups in guanidine-functionalized polyamine 1:1.0), and 16.2 g of modified bamboo powder (added at 12% of the total mass of castor oil-based cyclic carbonate and guanidine-functionalized polyamine) were stirred evenly. Then, 5 g of deionized water (foaming aid, added at 5% of the mass of castor oil-based cyclic carbonate), 1 g of DBU (catalyst C, Aladdin reagent), and 2 g of organosilicon nonionic surfactant (L-580, Momentive Advanced Materials) were added and stirred at high speed for 30 s until uniformly mixed. The mixture was quickly poured into a mold and placed in a constant temperature forced-air drying oven (DHG-9070A type) for foaming and curing reaction at 80℃ for 3 h. After cooling to room temperature, non-isocyanate polyurethane foam product A was obtained.

[0046] Example 2 This embodiment provides a method for preparing non-isocyanate polyurethane foam product B, and the specific steps are as follows: 1. Preparation of epoxidized castor oil 100 g castor oil, 11.8 g formic acid (molar ratio of hydrogen peroxide to formic acid 0.8:1), and 1.5 g strong acid ion exchange resin (catalyst A, D001 Tianjin Bohong resin) were stirred evenly and heated to 50℃. Under 0.10 MPa, 36.3 g of 30% hydrogen peroxide aqueous solution (molar ratio of hydrogen peroxide to carbon-carbon double bonds in castor oil 1.0:1) was added in batches through a dropping funnel in three batches, with an interval of 1 h between each batch. After the addition was completed, the reaction was continued at this temperature for 12 h. After the reaction was completed, the mixture was allowed to stand and separate into layers. The aqueous phase was discarded, and the organic phase was washed with deionized water until neutral. The mixture was then vacuum dried (80℃, -0.08 MPa) for 2 h to obtain epoxidized castor oil. The epoxy value was measured to be 0.29 mol / 100g.

[0047] 2. Preparation of castor oil-based cyclic carbonates 100 g of the epoxidized castor oil prepared above was added to a high-pressure reactor, along with 2 g of potassium bromide (catalyst B) and 1 g of tetrabutylammonium bromide (catalyst B, Aladdin reagent). The reactor was sealed, and the air inside was replaced with carbon dioxide three times. Then, carbon dioxide was introduced to a pressure of 0.5 MPa, and the temperature was raised to 80 °C. The mixture was stirred and reacted for 12 h. After the reaction was completed, the temperature was lowered to room temperature, the pressure was released, the product was removed, and vacuum dried (80 °C, -0.08 MPa) for 1 h to obtain castor oil-based cyclic carbonate. The cycloaddition conversion rate was measured to be 88.7%.

[0048] 3. Preparation of guanidinofunctionalized polyamines 50 g of polyetheramine D230 (Huntsman) and 55 g of guanidine sulfate were added to 100 mL of isopropanol as solvent. The mixture was heated to 65 °C and stirred for 5 h to carry out the functionalization modification reaction. After the reaction was completed, the solvent and unreacted raw materials were removed by vacuum distillation to obtain guanidine-functionalized polyamine. The amino content was measured to be 5.6 mmol / g.

[0049] 4. Preparation of modified bamboo powder Take 50 g of bamboo powder (passed through an 80-mesh sieve), add 200 mL of deionized water, ultrasonically disperse for 30 min, add 2 g of silane coupling agent KH-560, heat to 55℃, stir to carry out silanization reaction for 4 h, after the reaction is completed, filter, wash, and vacuum dry (80℃, -0.08 MPa) for 4 h to obtain modified bamboo powder.

[0050] 5. Foaming and curing of non-isocyanate polyurethane foam 100 g of castor oil-based cyclic carbonate, 36.7 g of guanidine-functionalized polyamine (molar ratio of cyclic carbonate groups in castor oil-based cyclic carbonate to amino groups in guanidine-functionalized polyamine 1:0.8), and 6.8 g of modified bamboo powder (added at 5% of the total mass of castor oil-based cyclic carbonate and guanidine-functionalized polyamine) were stirred evenly. Then, 1 g of water (foaming aid, added at 1% of the mass of castor oil-based cyclic carbonate), 0.8 g of zinc isooctanoate (catalyst C, Sinopharm Group), and 1.5 g of organosilicon nonionic surfactant were added. The mixture was stirred at high speed for 25 s until evenly mixed. The mixture was quickly poured into a mold and placed in a constant temperature oven. The foaming and curing reaction was carried out at 90℃ for 4 h. The mixture was then removed and cooled to room temperature to obtain non-isocyanate polyurethane foam.

[0051] Example 3 This embodiment provides a method for preparing non-isocyanate polyurethane foam product C from castor oil, and the specific steps are as follows: 1. Preparation of epoxidized castor oil 100 g castor oil, 42.8 g propionic acid (carboxylic acid, molar ratio of hydrogen peroxide to hydrogen peroxide 1.2:1), and 2.5 g phosphoric acid (catalyst A, analytical grade, Sinopharm Group) were mixed thoroughly and heated to 80 °C. Under 0.11 MPa, 54.4 g of 30% hydrogen peroxide aqueous solution (molar ratio of hydrogen peroxide to carbon-carbon double bonds in castor oil 1.5:1) was slowly added dropwise through a dropping funnel over 1.5 h. After the addition was complete, the reaction was continued at this temperature for 4 h. After the reaction was completed, the mixture was allowed to stand and separate into layers. The aqueous phase was discarded, and the organic phase was washed with deionized water until neutral. The mixture was then vacuum dried (80 °C, -0.08 MPa) for 2 h to obtain epoxidized castor oil. The epoxy value was measured to be 0.33 mol / 100 g.

[0052] 2. Preparation of castor oil-based cyclic carbonates 100 g of the epoxidized castor oil prepared above was added to a high-pressure reactor, along with 4 g of DBU (catalyst B). The reactor was sealed, and the air inside was replaced with carbon dioxide three times. Then, carbon dioxide was introduced to a pressure of 5.0 MPa, and the temperature was raised to 160 °C. The mixture was stirred for 2 h. After the reaction was completed, the temperature was lowered to room temperature, the pressure was released, the product was removed, and it was vacuum dried (80 °C, -0.08 MPa) for 1 h to obtain castor oil-based cyclic carbonate. The cycloaddition conversion rate was measured to be 95.1%.

[0053] 3. Preparation of guanidinofunctionalized polyamines 50g of isophorone diamine (Wanhua Chemical) and 65g of dicyandiamide (Aladdin reagent) were added to 100 mL of ethylene glycol as solvent. The mixture was heated to 85℃ and stirred for 5 h to carry out the functionalization modification reaction. After the reaction was completed, the solvent and unreacted raw materials were removed by vacuum distillation to obtain guanidine-functionalized polyamine. The amino content was measured to be 9.8 mmol / g.

[0054] 4. Preparation of modified bamboo powder Take 50 g of bamboo powder (passed through an 80-mesh sieve), add 200 mL of deionized water, ultrasonically disperse for 30 min, add 4 g of silane coupling agent KH-570, heat to 65℃, stir to carry out silanization reaction for 2 h, after the reaction is completed, filter, wash, and vacuum dry (80℃, -0.08 MPa) for 4 h to obtain modified bamboo powder.

[0055] 5. Foaming and curing of non-isocyanate polyurethane foam 100 g of castor oil-based cyclic carbonate, 48.0 g of guanidine-functionalized polyamine (molar ratio of cyclic carbonate groups in castor oil-based cyclic carbonate to amino groups in guanidine-functionalized polyamine 1:1.5), and 41.4 g of modified bamboo powder (added at 28% of the total mass of castor oil-based cyclic carbonate and guanidine-functionalized polyamine) were stirred evenly. Then, 10 g of water (foaming aid, added at 10% of the mass of castor oil-based cyclic carbonate), 1.5 g of tetrabutylammonium bromide (catalyst C), and 3 g of organosilicon nonionic surfactant were added. The mixture was stirred at high speed for 35 s until evenly mixed. The mixture was quickly poured into a mold and placed in a constant temperature oven. The foaming and curing reaction was carried out at 80°C for 2 h. The mixture was then removed and cooled to room temperature to obtain non-isocyanate polyurethane foam. Figure 1 This is a photograph of the non-isocyanate polyurethane foam prepared in Example 3 of the present invention. Figure 1 As can be seen, the non-isocyanate polyurethane foam prepared by this invention has a complete appearance, uniform cell distribution, no defects such as cell collapse or cracking, and has good macroscopic morphology and structural stability.

[0056] Comparative Example 1 Polyurethane foam product D was prepared using the existing isocyanate route. The raw materials were 100g MDI, 80g castor oil, 5g water, 1g tin catalyst, and 2g nonionic surfactant. The mixture was foamed and cured at 80℃ for 3h to obtain traditional polyurethane foam.

[0057] Comparative Example 2 This comparative example provides a method for preparing non-isocyanate polyurethane foam product E from castor oil, and the specific steps are as follows: 1. Preparation of epoxidized castor oil: completely consistent with Example 1.

[0058] 2. Preparation of castor oil-based cyclic carbonate: The preparation was completely consistent with Example 1, and castor oil-based cyclic carbonate with a cycloaddition conversion rate of 92.3% was obtained.

[0059] 3. Use of polyamine compounds: Use 50 g of diethylenetriamine directly as a crosslinking agent.

[0060] 4. Preparation of modified bamboo powder: completely consistent with Example 1.

[0061] 5. Foaming and curing reaction: Compared with Example 1, only the guanidine functionalized polyamine was replaced with an equal mass of diethylenetriamine, and the other conditions remained unchanged, and the foaming and curing reaction was carried out.

[0062] Comparative Example 3 This comparative example provides a method for preparing non-isocyanate polyurethane foam product F from castor oil, and the specific steps are as follows: 1. Preparation of epoxidized castor oil: completely consistent with Example 1.

[0063] 2. Preparation of castor oil-based cyclic carbonate: The preparation was completely consistent with Example 1, and castor oil-based cyclic carbonate with a cycloaddition conversion rate of 92.3% was obtained.

[0064] 3. Preparation of guanidinofunctionalized polyamines: completely consistent with Example 1.

[0065] 4. Use of unmodified bamboo powder: Use 21.7g of unmodified bamboo powder (passed through an 80-mesh sieve) directly as filler.

[0066] 5. Foaming and curing reaction: Compared with Example 1, only the modified bamboo powder was replaced with an equal mass of unmodified bamboo powder, and the other conditions remained unchanged, and a foaming and curing reaction was carried out.

[0067] Application Example 1: Structural Performance Testing 1. Test indicators: Examine the core structural properties of each foam product, such as microstructure, apparent density, compressive strength, and thermal conductivity.

[0068] 2. Testing Method: (1) Microstructure: The morphology and pore size distribution of the foam were observed using a SU8010 field emission scanning electron microscope (Hitachi) at a magnification of 500x; (2) Apparent density: determined according to FA2004 electronic balance (Shanghai Precision Science), GB / T 6343-2009; (3) Compressive strength: Measured using a WDW-10 universal testing machine (Jinan Test Metal), GB / T 8813-2022, with a compression rate of 1 mm / min and a compression amount of 10% of the original thickness; (4) Thermal conductivity: measured according to the DRL-III thermal conductivity meter (Xiangtan Xiangyi), GB / T 10294-2008, at a test temperature of 25℃; (5) Isocyanate residues: determined by gas chromatography (GC) using a GC-2010Plus gas chromatograph (Shimadzu), with a detection limit of 0.001%.

[0069] 3. Test Results: Table 1 Structural performance test results

[0070] Products A, B, and C prepared in Examples 1-3 of this invention all have a uniform cell structure, and their apparent density, compressive strength, and thermal conductivity are all within a suitable range. They also have no isocyanate residue and excellent structural performance, which can meet the usage requirements of scenarios such as heat preservation, automotive interiors, and cushioning packaging. In contrast, among the comparative products, product D contains toxic isocyanate residue, and products E and F have obvious cell structure defects, resulting in significant deterioration of mechanical and heat preservation properties, which cannot meet the requirements of practical applications.

[0071] Application Example 2: Detection of Plant Seed Germination Rate 1. Testing method: (1) Test seeds: Select common vegetable seeds (lettuce seeds), choose seeds that are plump and uniform in size, wash and dry them for later use; (2) Sample preparation: Cut each foam product into small pieces of 2 cm × 2 cm × 2 cm, sterilize by high pressure steam (121℃, 30 min, YXQ-LS-50SII type Shanghai Boxun), spread them evenly in a petri dish, add an equal amount of deionized water, and keep the foam moist (the water content is 200% of the foam's own mass). (3) Sowing and cultivation: 50 lettuce seeds were placed in each petri dish, spread evenly on the foam surface, and placed in an artificial climate chamber (RXZ-600 type, Ningbo Jiangnan Instruments) for cultivation. The cultivation conditions were: temperature 25±2℃, light 12 h / d, humidity 60±5%. The blank control group used sterile filter paper (with an equal amount of deionized water added). (4) Germination rate statistics: After 7 days of cultivation, the number of germinated seeds in each group was counted, and the germination rate was calculated (germination rate = number of germinated seeds / total number of seeds × 100%). Three parallel experiments were set up for each group, and the average value was taken.

[0072] 2. Test Results: Table 2 Results of plant seed germination rate test

[0073] Products A, B, and C prepared in Examples 1-3 of this invention all achieved a seed germination rate of over 88%, which is close to that of the blank control group, and the seedlings grew well, indicating that they are non-toxic, have excellent biocompatibility, and can be safely used as plant growth substrates. In contrast, among the comparative products, product D significantly inhibited seed germination due to isocyanate residue, and products E and F also had adverse effects on seed germination and seedling growth due to performance degradation, failing to meet the application requirements of plant growth substrates.

[0074] Application Example 3: Antibacterial Rate Detection Test method: The plate count method was used to select Escherichia coli and Staphylococcus aureus, common pathogens in plant cultivation and medical fields, as test strains.

[0075] (1) Sample preparation: Crush each foam product, pass it through a 100-mesh sieve, take 0.5 g of sample, add 5 mL of sterile physiological saline, and ultrasonically disperse for 10 min to prepare a sample suspension; (2) Preparation of bacterial culture: Activated Escherichia coli and Staphylococcus aureus were inoculated into LB medium and cultured at 37°C with shaking for 12 h, and then diluted to a bacterial concentration of 10. 6 CFU / mL; (3) Antibacterial culture: Mix 1 mL of bacterial solution with 1 mL of sample suspension and culture at 37°C with shaking for 24 h. The blank control group is replaced with 1 mL of sterile physiological saline instead of sample suspension. (4) Colony counting: The cultured mixture was serially diluted, and 0.1 mL was spread on LB plates and incubated at 37℃ for 24 h. The colony count was counted and the inhibition rate was calculated (inhibition rate = (number of colonies in blank control group - number of colonies in sample group) / number of colonies in blank control group × 100%). Three parallel experiments were set up for each group and the average value was taken.

[0076] 2. Test Results: Table 3 Results of antibacterial rate test

[0077] Products A, B, and C prepared in Examples 1-3 of this invention all achieved an antibacterial rate of over 87% against Escherichia coli and Staphylococcus aureus, demonstrating excellent antibacterial effects. This is because the guanidinium group in the guanidinium-functionalized polyamine has strong antibacterial activity and can effectively inhibit the growth of pathogenic bacteria. In contrast, among the comparative products, product D showed no significant antibacterial effect, and the antibacterial rates of products E and F were significantly lower than those of the products of this invention, failing to meet the antibacterial requirements for biomedical dressings and plant growth substrates.

[0078] Application Example 4: Controlled Biodegradation Performance Testing 1. Testing method: (1) Preparation of simulated soil: Select farmland topsoil (pH 6.5~7.0), remove stones and weeds, crush and pass through a 20-mesh sieve, sterilize (121℃, 30 min), and adjust soil moisture to 60±5%; (2) Sample preparation: Cut each foam product into small pieces of 3 cm × 3 cm × 1 cm, accurately weigh the initial mass (m0), and wrap them in nylon mesh bags (to prevent the samples from scattering). (3) Burial experiment: The wrapped sample was buried in simulated soil at a depth of 10 cm and placed in an artificial climate chamber for cultivation. The cultivation conditions were: temperature 25±2℃, humidity 60±5%, and deionized water was added regularly to maintain stable soil moisture. (4) Degradation rate statistics: The samples were taken out after 30 days, 60 days and 90 days of burial, respectively, washed, vacuum dried (80℃, -0.08 MPa) to constant weight, and the remaining mass (m1) was weighed. The degradation rate was calculated (degradation rate = (m0-m1) / m0×100%). Three parallel experiments were set up for each group and the average value was taken.

[0079] 2. Test Results: Table 4 Results of Controlled Biodegradability Tests

[0080] Products A, B, and C prepared in Examples 1-3 of this invention exhibited excellent controllable biodegradability in simulated soil burial experiments. The degradation rate after 90 days was between 32% and 39%, a rate that perfectly balances "structural stability during the planting period" and "environmental absorbability after disposal." They maintain complete support during the crop growth cycle (typically 30-60 days) and rapidly decompose and return to the soil after harvest, transforming into humus, fundamentally solving the problems of "white pollution" and microplastic residues associated with traditional plastic matrices. In contrast, among the comparative products, product D (traditional isocyanate type) is extremely difficult to degrade, degrading very slowly. After 90 days, the foam morphology remains essentially unchanged, producing microplastic fragments that easily cause soil pollution. Product E has a slow degradation rate; after 90 days, the foam partially pulverizes, but unreacted raw materials remain, indicating incomplete degradation. Product F has a relatively slow degradation rate; after 90 days, the foam cracks, but the bamboo powder separates from the foam matrix, resulting in uneven degradation. Products D, E, and F cannot achieve controllable degradation and are insufficient to meet the application requirements of agricultural and environmentally friendly materials.

[0081] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. Those skilled in the art can obtain other embodiments based on the disclosure of the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing non-isocyanate polyurethane foam from castor oil, characterized in that, Includes the following steps: Castor oil, carboxylic acid, and hydrogen peroxide were subjected to an epoxidation reaction in the presence of catalyst A to obtain epoxidized castor oil. The epoxidized castor oil was subjected to a cycloaddition reaction with carbon dioxide in the presence of catalyst B to obtain castor oil-based cyclic carbonate. The polyamine compound was functionalized by reacting it with a guanidine-modifying agent to obtain guanidine-functionalized polyamines. Bamboo powder is silanized with a silane coupling agent to obtain modified bamboo powder. The castor oil-based cyclic carbonate, the guanidine-functionalized polyamine, and the modified bamboo powder are mixed, a foaming agent is added, and a foaming and curing reaction is carried out to obtain the non-isocyanate polyurethane foam.

2. The preparation method according to claim 1, characterized in that, The catalyst A is selected from at least one of sulfuric acid, phosphoric acid, p-toluenesulfonic acid, or a strong acid ion exchange resin.

3. The preparation method according to claim 1, characterized in that, The epoxidation reaction is carried out at a temperature of 50-80℃, a pressure of 0.09-0.11 MPa, and a reaction time of 4-12 h.

4. The preparation method according to claim 1, characterized in that, The molar ratio of hydrogen peroxide to carbon-carbon double bonds in castor oil is 1.0:1 to 1.5:1; The molar ratio of the carboxylic acid to hydrogen peroxide is 0.8:1 to 1.2:

1.

5. The preparation method according to claim 1, characterized in that, The catalyst B is selected from at least one of potassium bromide, potassium iodide, tetrabutylammonium bromide, and 1,8-diazabicycloundec-7-ene; The cycloaddition reaction is carried out at a pressure of 0.5~5.0 MPa, a temperature of 80~160℃, and a time of 2~12 h.

6. The preparation method according to claim 1, characterized in that, The polyamine compound is selected from at least one of ethylenediamine, diethylenetriamine, triethylenetetramine, isophorone diamine, or polyetheramine; The guanidinizing agent is selected from at least one of guanidine hydrochloride, guanidine sulfate, dicyandiamide, guanidine nitrate, or guanidinoacetic acid.

7. The preparation method according to claim 1, characterized in that, The molar ratio of the cyclic carbonate group in the castor oil-based cyclic carbonate to the amino group in the guanidine-functionalized polyamine is 1:0.8~1.5; The amount of modified bamboo powder added is 5-28% of the total mass of castor oil-based cyclic carbonate and guanidine-functionalized polyamine.

8. The preparation method according to claim 1, characterized in that, The foaming agent includes water, catalyst C, and nonionic surfactant; The amount of water added is 1-10% of the mass of castor oil-based cyclic carbonate; The catalyst C is selected from at least one of organic bases, organozinc compounds, or quaternary ammonium salt ionic liquids.

9. A non-isocyanate polyurethane foam prepared from castor oil, characterized in that, Prepared by the preparation method according to any one of claims 1 to 8, and possessing the following properties: Apparent density: 0.15~0.22 g / cm³ 3 The compressive strength is 0.25~0.41 MPa, and the thermal conductivity is 0.037~0.042 W / (m·K).

10. The use of the non-isocyanate polyurethane foam prepared by the preparation method according to any one of claims 1 to 8 or the non-isocyanate polyurethane foam according to claim 9 in the preparation of thermal insulation materials, automotive interior parts, cushioning packaging materials, biomedical dressings or plant growth substrates.

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