Process for extracting gutta-percha from eucommia ulmoides shells

Abstract

The invention discloses a process for extracting gutta-percha from eucommia ulmoides shells. The process comprises the following steps: crushing a eucommia ulmoides raw material to obtain plant powder; mixing the plant powder with a protective agent solution, and drying to form a coating protective layer on the surfaces of the particles; the plant powder coated with the protective layer is placed in a dynamic oxidation reaction environment, ozone-containing gas is introduced for oxidation treatment, the oxidation treatment process comprises at least two stages, the ozone concentration of the first stage is higher than that of the second stage, and the humidity of the first stage is lower than that of the second stage; removing a protective layer and oxygenolysis products in the oxidized material, separating solids, and drying to obtain crude eucommia ulmoides gum; and extracting the eucommia ulmoides crude rubber by using an organic solvent, and then concentrating, precipitating and drying to obtain the refined eucommia ulmoides rubber. The invention solves the problems of prominent contradiction between purity and yield, poor oxidation selectivity and complex process in the prior art.

Description

Technical Field

[0002] This invention belongs to the field of Eucommia gum preparation technology, and particularly relates to a process for extracting Eucommia gum from Eucommia bark. Background Technology

[0004] Eucommia ulmoides is a precious economic tree species and medicinal plant unique to my country. Its leaves and fruit shells are rich in a natural polymer material called eucommia gum (trans-1,4-polyisoprene). Due to its unique rubber-plastic dual properties, eucommia gum has broad application prospects in tire manufacturing, aerospace, medical materials, and special functional materials. It is regarded as a strategic bio-based material to alleviate the shortage of natural rubber resources in my country.

[0005] Traditional extraction methods struggle to efficiently separate and purify Eucommia ulmoides fruit shells from plant tissues. To improve extraction efficiency, existing technologies, such as Chinese patent application 201610046708.X, disclose a method combining mechanical crushing and ozone oxidation with solvent extraction for Eucommia ulmoides fruit shells. While this method effectively removes lignocellulose, it suffers from the following technical drawbacks: 1) First, obtaining high-purity products often requires prolonged and multi-cycle ozone oxidation, which can lead to excessive oxidation and degradation of Eucommia ulmoides gum molecules, significantly reducing the product yield and creating an irreconcilable conflict between purity and yield; 2) Second, the process involves multiple cycles of crushing, oxidation, and drying, resulting in a lengthy process flow and high energy consumption and processing time; 3) Furthermore, the ozone oxidation process is typically a static, constant-condition treatment, unable to adjust reaction conditions in real-time according to the material's state. The oxidant indiscriminately attacks both lignocellulose and Eucommia ulmoides gum, leading to low oxidation efficiency and poor selectivity.

[0006] Therefore, there is an urgent need for an extraction method that can effectively protect Eucommia gum while efficiently removing impurities and simplifying the process. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the technical defects of the existing Eucommia gum extraction process, such as the prominent contradiction between purity and yield, poor selectivity of oxidation process, and complex and lengthy process.

[0009] To address the aforementioned technical problems, this invention provides a process for extracting high-purity Eucommia gum from Eucommia ulmoides raw materials, the process comprising the following steps:

[0010] S1. Raw material pretreatment: The Eucommia ulmoides raw material is crushed to obtain plant powder;

[0011] S2. Protective layer formation: The plant powder is mixed with a protective agent solution and then dried to form a protective coating on the surface of the plant powder particles;

[0012] S3. Dynamic gradient ozone oxidation: The plant powder coated with the protective layer is placed in a dynamic oxidation reaction environment, and an ozone-containing gas is introduced for oxidation treatment; the oxidation treatment process includes at least two stages, wherein the ozone concentration in the first stage is higher than the ozone concentration in the second stage, and the humidity in the first stage is lower than the humidity in the second stage;

[0013] S4. Protective layer removal and primary extraction: Remove the protective layer and oxidation decomposition products from the oxidized material, separate the solids, and dry to obtain Eucommia ulmoides crude gum;

[0014] S5. Refining: The crude Eucommia gum is extracted using an organic solvent, and then concentrated, precipitated, and dried to obtain refined Eucommia gum.

[0015] Furthermore, the protective agent in step S2 is selected from at least one of water-soluble or alkali-soluble polymeric compounds and nano-inorganic oxides.

[0016] Furthermore, the protective agent is selected from at least one of polyvinyl alcohol, sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose, and silica sol.

[0017] Further, in step S2, the mass concentration of the protectant solution is 1-10 wt%, and the mass ratio of plant powder to protectant solution is 100:200~100:500.

[0018] Furthermore, in step S3, the ozone concentration in the first stage is 40-80 mg / L, and the ozone concentration in the second stage is 10-30 mg / L; the humidity in the first stage is ≤30% RH, and the humidity in the second stage is 50-80% RH.

[0019] Furthermore, in step S3, the total time for oxidation treatment is 1-3 hours, with the first stage of treatment accounting for 30%-60% of the total time.

[0020] Furthermore, in step S3, the dynamic oxidation reaction environment is provided by a fluidized bed reactor or a rotary drum reactor.

[0021] Furthermore, a physical field, such as an ultrasonic field or a microwave field, can be coupled and applied simultaneously with the oxidation treatment for synergistic processing. Preferably, the power of the coupled ultrasonic field is 100-500 W and the frequency is 20-40 kHz; or the power of the coupled microwave field is 300-800 W.

[0022] Furthermore, in step S3, before performing ozone oxidation treatment, a step of evacuating the dynamic oxidation reaction environment is included, with a vacuum degree of -0.08 to -0.095 MPa; when introducing ozone-containing gas, the reaction environment pressure is maintained at -0.01 to -0.03 MPa.

[0023] Further, the organic solvent in step S5 includes a main solvent, a surfactant, and a swelling agent. Preferably, the main solvent is petroleum ether, cyclohexane, or a eutectic solvent, the surfactant is sorbitan monooleate, and the swelling agent is γ-valerolactone; preferably, the volume ratio of petroleum ether, sorbitan monooleate, and γ-valerolactone in the organic solvent is 1:0.05-0.1:0.05-0.2.

[0024] Furthermore, the refining process employs a multi-stage countercurrent extraction method.

[0025] Furthermore, prior to the concentration step, the extract is pre-concentrated using a nanofiltration membrane.

[0026] This invention also provides a high-purity Eucommia ulmoides gum product, which is prepared by any of the processes described above. Furthermore, this invention also provides the application of the aforementioned high-purity Eucommia ulmoides gum product in the preparation of medical devices or cable insulation materials.

[0027] Compared with existing technologies, this invention has at least the following beneficial effects: By constructing a protective coating layer on the plant powder particles before ozone oxidation, this invention physically isolates ozone from direct contact with the eucommia gum, effectively protecting the eucommia gum molecular chains from attack and degradation during the strong oxidation stage. The subsequent dynamic gradient ozone oxidation strategy, using a higher ozone concentration and lower humidity in the initial stage, efficiently attacks and decomposes impurities such as lignocellulose on the surface of the plant powder covered by the protective layer. In the later stage, the ozone concentration is reduced and the ambient humidity is increased. This reduces the intensity of the oxidant, and the high humidity environment helps form a water molecule layer on the material surface, further buffering the oxidant's erosion of the internal eucommia gum, thus achieving highly selective oxidation and removal of impurities. This combination of protective layer isolation and dynamic gradient oxidation directly solves the contradiction between purity and yield caused by indiscriminate oxidation in existing technologies. Because impurities are removed more efficiently and selectively, a single oxidation treatment can achieve the ideal purification effect, avoiding multiple cycles, thereby simplifying the process and reducing energy consumption and processing time. Meanwhile, by optimizing the compound extractant used in the refining process, the synergistic effect of its components can more gently and efficiently dissolve and extract Eucommia gum, further ensuring the acquisition of high-yield and high-purity products. Detailed Implementation

[0029] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0030] In this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0031] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0032] It should be understood that in various embodiments of the present invention, the order of the above-mentioned processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0033] This invention provides a process for extracting high-purity eucommia gum from eucommia bark. This process constructs a protective coating layer on the plant powder particles before ozone oxidation and combines ozone oxidation treatment under dynamic gradient conditions to achieve efficient and selective oxidation removal of impurities such as wood fibers, while effectively protecting the eucommia gum molecular chains. This solves the technical problems of difficulty in balancing purity and yield, poor oxidation selectivity, and lengthy processes in the prior art.

[0034] Embodiments of the present invention provide a process for extracting high-purity eucommia gum from Eucommia ulmoides raw materials, comprising the following steps:

[0035] S1. Raw material pretreatment: The Eucommia ulmoides raw material is crushed to obtain plant powder;

[0036] S2. Protective layer formation: The plant powder is mixed with the protective agent solution and then dried to form a protective coating on the surface of the plant powder particles;

[0037] S3. Dynamic gradient ozone oxidation: Plant powder coated with a protective layer is placed in a dynamic oxidation reaction environment and oxidized by passing ozone-containing gas through it. The oxidation process includes at least two stages, wherein the ozone concentration in the first stage is higher than that in the second stage, and the humidity in the first stage is lower than that in the second stage.

[0038] S4. Protective layer removal and primary extraction: Remove the protective layer and oxidation decomposition products from the oxidized material, separate the solids, and obtain Eucommia ulmoides crude gum after drying;

[0039] S5. Refining: The crude gum of Eucommia ulmoides is extracted using an organic solvent, and then concentrated, precipitated and dried to obtain refined Eucommia ulmoides gum.

[0040] This invention constructs a protective layer in step S2, physically isolating the strong oxidizing ozone from direct contact with the internal eucommia gum. In step S3, dynamic oxidation is performed using gradient-varying ozone concentrations and humidity conditions. In the first stage, the synergistic effect of high ozone concentration (40-80 mg / L) and low humidity (≤30% RH) powerfully and rapidly attacks and decomposes impurities such as lignin and hemicellulose on the surface of the plant powder (the area covered by the protective layer), while the internal eucommia gum is protected by the protective layer. The second stage then proceeds, reducing the ozone concentration (10-30 mg / L) and increasing the humidity (50-80% RH). At this point, the oxidant strength is weakened, and the higher humidity helps form a water film on the outer surface of the material particles. This water film further blocks and consumes residual ozone, effectively buffering its erosion of the internal eucommia gum. Simultaneously, moderate humidity and ozone can continue to treat deep impurities or small molecule products that were not completely decomposed in the first stage. This "protective-gradient oxidation" strategy enables the oxidation reaction to proceed in a controlled manner from the outside to the inside and from strong to weak, significantly improving the selectivity of the oxidation process. This allows for efficient removal of impurities in a single treatment, avoiding multiple cycles of oxidation. As a result, high purity products are obtained while ensuring high extraction yields and simplifying the process.

[0041] In this embodiment, the protective agent in step S2 is selected from at least one of water-soluble or alkali-soluble polymeric compounds and nano-inorganic oxides. When the protective agent is a water-soluble or alkali-soluble polymeric compound, such as at least one of polyvinyl alcohol, sodium carboxymethyl cellulose, or hydroxypropyl methylcellulose, this type of polymer can form a dense, flexible, thin film-like coating layer on the surface of plant powder particles, exhibiting good isolation effect and biocompatibility, and is easily removed by subsequent water washing or alkali washing. When the protective agent is a nano-inorganic oxide, such as silica sol, it can form a porous, rigid inorganic coating layer on the particle surface. This layer structure not only isolates ozone, but its porosity also facilitates the diffusion of ozone and water molecules, making the oxidation reaction more uniform. The above two types of protective agents can be used alone or in combination to obtain better overall performance (such as mechanical strength and permeability). The film layer formed by polyvinyl alcohol has the best flexibility, the film layer formed by sodium carboxymethyl cellulose is most easily removed under alkaline conditions, and the coating layer formed by silica sol has the best ozone permeability resistance and thermal stability.

[0042] In this embodiment, in step S2, the mass concentration of the protective agent solution is preferably 1-10 wt%. If the concentration is below 1 wt%, the formed protective layer will be too thin and may not provide effective isolation protection; if the concentration is above 10 wt%, the solution viscosity will be too high, making mixing difficult and potentially resulting in an excessively thick coating layer, which will affect the effective attack of the oxidant on surface impurities. The mass ratio of plant powder to protective agent solution is preferably 100:200 to 100:500. This ratio ensures that the powder is fully wetted and coated by the solution. A ratio higher than 100:200 may result in incomplete coating, while a ratio lower than 100:500 will cause excess solvent, increasing subsequent drying energy consumption.

[0043] In this embodiment, in step S3, the ozone concentration in the first stage is preferably 40-80 mg / L, and the ozone concentration in the second stage is preferably 10-30 mg / L; the humidity in the first stage is preferably ≤30% RH, and the humidity in the second stage is preferably 50-80% RH. These parameter ranges are optimized intervals verified through extensive experiments. The high ozone concentration (40-80 mg / L) in the first stage is key to the rapid decomposition of stubborn impurities such as lignin, while the low humidity environment (≤30% RH) prevents ozone from reacting prematurely with water molecules to generate more reactive species such as hydroxyl radicals, thus avoiding non-selective attack on the eucommia gum. In the second stage, the ozone concentration is reduced to 10-30 mg / L, and the humidity is increased to 50-80% RH. The increased humidity helps dissolve the oxidation intermediates (such as small molecule organic acids) generated in the first stage and carry them out with the airflow, while the water molecule layer effectively quenches excess ozone, protecting the internal eucommia gum.

[0044] In this embodiment, the total oxidation time in step S3 is preferably 1-3 hours. Too short a total time (<1 hour) may result in incomplete oxidation and excessive impurity residue; too long a total time (>3 hours) may cause the protective layer to be slowly penetrated due to prolonged processing, increasing the risk of oxidation of the eucommia gum. The first stage of processing accounts for 30%-60% of the total time. This proportion ensures that the main stubborn impurities are effectively decomposed in the first stage.

[0045] In this embodiment, in step S3, the dynamic oxidation reaction environment is preferably provided by a fluidized bed reactor or a rotary drum reactor. A fluidized bed reactor keeps the material particles in a suspended fluidized state, achieving high mixing and mass transfer between the gas and solid phases, ensuring sufficient contact between ozone and the protective layer and impurities on the surface of each particle, resulting in uniform and efficient oxidation. A rotary drum reactor, through the slow rotation of the drum, continuously tumbles the material, also achieving dynamic and uniform oxidation. Compared to static reaction vessels, these two devices significantly improve reaction efficiency and uniformity.

[0046] In addition to the above-mentioned methods, in step S3, a physical field can be coupled and applied simultaneously with the oxidation treatment for synergistic processing. This physical field can be an ultrasonic field or a microwave field. When an ultrasonic field is coupled and applied, the cavitation effect and mechanical vibration generated by the ultrasound can continuously "clean" and "impact" the protective layer and oxidation interface on the surface of the material particles, accelerating the diffusion of ozone into the impurities and the removal of oxidation products, thereby further improving the oxidation efficiency. The power of the ultrasonic field is preferably 100-500 W, and the frequency is 20-40 kHz. A power lower than 100 W may not have a significant effect, while a power higher than 500 W may damage the integrity of the protective layer or cause local overheating. When a microwave field is coupled and applied, microwaves can selectively heat polar molecules in the material (such as water, lignin decomposition products, etc.), generating local hot spots and accelerating the oxidation reaction process. The power of the microwave field is preferably 300-800 W. By coupling physical fields, the same or better impurity removal effect can be achieved without increasing the ozone concentration or extending the reaction time, thereby further improving the process efficiency.

[0047] Furthermore, in step S3, before ozone oxidation, a vacuuming step is included to evacuate the dynamic oxidation reaction environment, preferably to a vacuum level of -0.08 to -0.095 MPa. This step removes air from the reactor and material pores, reducing the dilution and interference of ozone by inert gases such as oxygen and nitrogen, ensuring that the subsequently introduced ozone can act more efficiently on the target material. When introducing ozone-containing gas, the reaction environment pressure is maintained at -0.01 to -0.03 MPa (slight negative pressure). Maintaining a slight negative pressure state facilitates the timely removal of gaseous products generated by the reaction (such as CO2, small molecule aldehydes and ketones) from the reaction system by the gas flow, promoting the forward oxidation reaction, while also preventing ozone leakage.

[0048] In this embodiment, the organic solvent in step S5 is a composite extractant, comprising a main solvent, a surfactant, and a swelling agent. The main solvent (such as petroleum ether or cyclohexane) is the primary medium for dissolving Eucommia ulmoides gum. The addition of the surfactant (sorbitan monooleate) reduces the surface tension of the solvent system, improves its wetting and stripping effect on the extremely fine impurities remaining in the crude Eucommia ulmoides gum, and emulsifies a small amount of fat-soluble impurities, making them easier to separate from the gum. The swelling agent (γ-valerolactone) is a highly polar solvent that can penetrate into the network structure of the gum, causing it to swell moderately, thereby breaking the bond between the colloid and residual impurities (such as trace amounts of incompletely oxidized lignin-carbohydrate complexes), allowing the main solvent to more fully contact and dissolve the gum molecules. The synergistic effect of these three components makes the extraction of Eucommia ulmoides gum by this composite extractant more selective and efficient.

[0049] Specifically, the primary solvent is preferably one of petroleum ether, cyclohexane, or a eutectic solvent. Petroleum ether and cyclohexane are traditional nonpolar solvents with good solubility for Eucommia ulmoides gum. Eutectic solvents (e.g., prepared by mixing choline chloride and urea in a certain molar ratio) are green solvents with advantages such as high designability, good solubility, and low volatility. The surfactant is preferably sorbitan monooleate, a common food-grade nonionic surfactant with high safety and good compatibility with the primary solvent. The swelling agent is preferably γ-valerolactone, a bio-based green solvent with good swelling capacity for many polymers.

[0050] More specifically, in the composite extractant composed of petroleum ether, sorbitan monooleate, and γ-valerolactone, the preferred volume ratio of the three is 1:0.05-0.1:0.05-0.2. If the proportion of sorbitan monooleate is below 0.05, the surface activity is insufficient; if it is above 0.1, excessive foaming may occur, affecting the operation. If the proportion of γ-valerolactone is below 0.05, the swelling effect is not significant; if it is above 0.2, it may cause excessive swelling of the eucommia gum or even partial dissolution in γ-valerolactone, affecting the subsequent selective precipitation in the non-polar main solvent.

[0051] In this embodiment, the purification step in step S5 can be carried out using a multi-stage countercurrent extraction method. Fresh solvent is added from the last stage extraction vessel, contacting the material with the lowest gum content in a countercurrent manner; while the material with the highest gum content contacts the solvent rich in eucommia gum after multi-stage extraction in the first stage extraction vessel. This method can maximize the utilization of the solvent's extraction capacity, obtaining a high extraction concentration and extraction rate with less solvent, resulting in significant economic benefits.

[0052] In this embodiment, in step S5, before the concentration step, the extract can be pre-concentrated using a nanofiltration membrane. Nanofiltration membranes can retain large molecules of Eucommia ulmoides gum while allowing most small-molecule solvents (such as petroleum ether) and a small amount of impurities to pass through. Pre-concentration via nanofiltration significantly reduces the amount of solvent required for subsequent evaporation and concentration, thereby greatly reducing energy consumption, shortening process time, and reducing the risk of thermal degradation of Eucommia ulmoides gum during high-temperature concentration.

[0053] This application also provides a composite extractant for extracting Eucommia ulmoides gum. The composite extractant comprises a main solvent, a surfactant, and a swelling agent. This composite extractant is specifically designed for the efficient and selective extraction of Eucommia ulmoides gum from crude Eucommia gum obtained through the aforementioned process. The components and their synergistic mechanism are as described above in the purification step (S5). The main solvent is selected from at least one of petroleum ether, cyclohexane, and eutectic solvents; the surfactant is sorbitan monooleate; and the swelling agent is γ-valerolactone. The volume ratio of petroleum ether, sorbitan monooleate, and γ-valerolactone is 1:0.05-0.1:0.05-0.2.

[0054] This application also provides a high-purity Eucommia ulmoides gum product, which is prepared by any of the processes described above. Benefiting from the effective protection of the Eucommia ulmoides gum molecular chains by the "protective-gradient oxidation" process and the use of a highly efficient composite extractant, this product achieves a purity (characterized by thermogravimetric analysis and 1H NMR spectroscopy) of over 98%, while the extraction yield (based on the theoretical content of Eucommia ulmoides gum in the raw material) can reach over 86%. Furthermore, the molecular weight distribution is more concentrated, indicating a low degree of oxidative degradation.

[0055] This application also provides the application of the above-mentioned high-purity Eucommia ulmoides gum product in the preparation of medical devices or cable insulation materials. Due to its high purity and excellent molecular integrity, this Eucommia ulmoides gum exhibits better biocompatibility and controllable mechanical properties in the field of medical devices (such as biodegradable sutures and drug sustained-release carriers); in the field of cable insulation materials, it demonstrates more stable dielectric properties and a longer service life.

[0056] The technical solution and effects of the present invention are further illustrated below through specific embodiments. Unless otherwise specified, all equipment and raw materials used in the following embodiments are commercially available.

[0057] Example 1

[0058] S1. Raw material pretreatment: Take dried Eucommia bark, crush it with a pulverizer, and pass it through a 60-mesh sieve to obtain plant powder.

[0059] S2. Protective Layer Formation: A 5% (w / w) aqueous solution of polyvinyl alcohol (PVA-1788) was prepared as the protective agent solution. The plant powder was added to the protective agent solution at a mass ratio of 100:300, and mechanically stirred for 30 minutes at 200 rpm in a 50°C water bath to ensure thorough mixing and wetting. The mixture was then dried in an 80°C oven for 6 hours until completely dry, yielding plant powder coated with a PVA protective layer.

[0060] S3. Dynamic Gradient Ozone Oxidation: The coated powder is loaded into a fluidized bed reactor. The total oxidation time is set to 2 hours. First stage (1 hour): A mixed gas with an ozone concentration of 60 mg / L and a humidity of 20% RH is introduced at a flow rate of 5 L / min. Second stage (1 hour): The flow rate is switched to a mixed gas with an ozone concentration of 20 mg / L and a humidity of 70% RH, while maintaining the same flow rate.

[0061] S4. Protective Layer Removal and Primary Extraction: The oxidized material was placed in a 2% sodium hydroxide solution and stirred and washed at 80°C for 1 hour to remove the PVA protective layer and water-soluble oxidation decomposition products. The mixture was then filtered, and the solid was washed with deionized water until neutral. It was then vacuum dried at 60°C to obtain crude Eucommia ulmoides gum.

[0062] S5. Refining: Eucommia ulmoides crude gum was mixed with a compound extractant at a mass ratio of 1:15. The compound extractant was composed of petroleum ether, sorbitan monooleate, and γ-valerolactone in a volume ratio of 1:0.08:0.1. Extraction was carried out by stirring at 60℃ and 150 rpm for 2 hours. The mixture was filtered to obtain the extract. The extract was pre-concentrated by passing it through a nanofiltration membrane with a molecular weight cutoff of 1000 Da, resulting in a volume reduction of approximately 70%. The remaining concentrate was rotary evaporated at 60℃ until it reached a viscous state, and then added dropwise to 5 times its volume of cold ethanol (-10℃) to precipitate. The precipitate was filtered, washed with ethanol, and then vacuum-dried at 40℃ for 24 hours to obtain refined Eucommia ulmoides gum.

[0063] Example 2

[0064] The steps in this embodiment are basically the same as those in Embodiment 1, except that in step S3, during the dynamic gradient ozone oxidation process, an ultrasonic field is simultaneously coupled into the fluidized bed reactor. The ultrasonic power is 300 W and the frequency is 28 kHz. The remaining parameters and operations are the same as in Embodiment 1.

[0065] Example 3

[0066] The steps in this embodiment are basically the same as those in Embodiment 1, except that in step S3, before introducing ozone gas, the fluidized bed reactor containing the material is evacuated to -0.09 MPa and maintained for 5 minutes. Subsequently, when the ozone mixed gas is introduced for oxidation treatment, the pressure inside the reactor is maintained at -0.02 MPa (slight negative pressure) by adjusting the exhaust valve. The remaining parameters and operations are the same as in Embodiment 1.

[0067] Example 4

[0068] Steps S1 to S4 in this embodiment are the same as in embodiment 1.

[0069] S5. Refining: A three-stage countercurrent extraction method was used. Three extraction vessels were set up in series, with the mass ratio of crude Eucommia gum to compound extractant (same as in Example 1) in each vessel being 1:10. Fresh solvent was added from the third-stage extraction vessel and flowed countercurrently to the first stage. The material moved sequentially from the first stage to the third stage. Each extraction was carried out at 60°C for 1.5 hours. The gum-rich extract flowing out of the first-stage extraction vessel was first pre-concentrated by nanofiltration, then subjected to rotary evaporation, ethanol precipitation, and drying to obtain refined Eucommia gum.

[0070] Comparative Example 1

[0071] Step S1 in this comparative example is the same as in Example 1.

[0072] S2. Omit the protective layer formation step and use dry plant powder directly.

[0073] S3. Place the plant powder in a static tray reactor, introduce a mixed gas with an ozone concentration of 40 mg / L and a humidity of 50% RH, and oxidize under constant conditions for 3 hours.

[0074] S4. Wash the oxidized material directly with 2% NaOH solution at 80°C for 1 hour, and then proceed with the same treatment as in Example 1.

[0075] S5. The refining steps are the same as in Example 1.

[0076] Comparative Example 2

[0077] Steps S1 and S2 in this comparative example are the same as in Example 1.

[0078] S3. Place the coated powder in a fluidized bed reactor, but introduce a mixture of ozone gas under constant conditions (ozone concentration 40 mg / L, humidity 50% RH) for oxidation for 2 hours.

[0079] S4 and S5 are the same as in Example 1.

[0080] Comparative Example 3

[0081] Unlike Example 1, this comparative example uses petroleum ether as the sole organic extraction solvent in step S5, the purification step. All other parameters and procedures are the same as in Example 1.

[0082] Product performance testing:

[0083] The purity and yield of the refined Eucommia ulmoides gum products obtained in Examples 1-4 and Comparative Examples 1-3 were determined. Purity was determined by thermogravimetric analysis (TGA). Under a nitrogen atmosphere, the residual ash content at 600°C was considered an impurity. Purity = 100% - ash content%. Yield = (mass of refined Eucommia ulmoides gum obtained / theoretical mass of Eucommia ulmoides gum in the raw material plant powder) × 100%, where the theoretical mass was obtained by standardization of the same batch of raw materials using Soxhlet extraction.

[0084] The test results are shown in Table 1 below:

[0085] Table 1

[0086] Group Product purity (%) Extraction yield (%) Example 1 98.0 86.5 Example 2 99.2 89.1 Example 3 98.8 88.6 Example 4 99.5 90.2 Comparative Example 1 89.5 72.3 Comparative Example 2 91.2 80.4 Comparative Example 3 88.3 76.8

[0087] The test results in Table 1 are analyzed as follows:

[0088] 1) Compared to Comparative Example 1, Example 1 showed a significant improvement in product purity, increasing from 89.5% to 98.0%, and extraction yield, increasing from 72.3% to 86.5%. This indicates that without a protective layer, direct contact between constant, moderate concentrations of ozone and plant powder leads to several issues. First, the lack of physical isolation causes ozone to non-selectively attack both impurities like lignocellulose and the eucommia gum molecular chains, resulting in oxidative degradation of the eucommia gum and a substantial decrease in extraction yield. Second, oxidation under constant conditions lacks specificity; the initial oxidation intensity is insufficient to rapidly and efficiently decompose stubborn impurities, while the subsequent continuous moderate-concentration oxidation causes unnecessary damage to the eucommia gum, resulting in incomplete impurity removal and low purity. Furthermore, the low gas-solid contact efficiency in the static tray reactor further reduces the uniformity and efficiency of oxidation. This comparative result fully demonstrates that the synergistic combination of "protective layer construction," "dynamic gradient ozone oxidation," and "dynamic oxidation reaction environment" in this invention plays a crucial role in simultaneously improving purity and yield.

[0089] 2) Compared to Comparative Example 2, the product purity of Example 1 increased from 91.2% to 98.0%, and the extraction yield increased from 80.4% to 86.5%. Comparing Comparative Example 2 and Comparative Example 1, it can be seen that simply adding a protective layer (Comparative Example 2 compared to Comparative Example 1) increased the purity from 89.5% to 91.2% and the yield from 72.3% to 80.4%, indicating that the protective layer itself already played a certain role in isolation and protection. However, the purity and yield of Comparative Example 2 were still significantly lower than those of Example 1. This indicates that even with a protective layer, if the oxidation conditions are constant and of moderate intensity, on the one hand, the initial oxidation intensity is not high enough to quickly and efficiently decompose stubborn surface impurities, resulting in insufficient purity due to impurity residue; on the other hand, oxidation under constant conditions for a long time will still slowly penetrate the protective layer, causing a certain degree of oxidative degradation of the internal Eucommia gum, affecting the yield. The comparative results fully demonstrate the key technical value of the dynamic gradient oxidation conditions in step S3 of this invention—the first stage of high ozone concentration and low humidity conditions can rapidly and powerfully decompose surface impurities, while the second stage of low ozone concentration and high humidity conditions further protects the eucommia gum and removes residual impurities and oxidation intermediates by forming a water film. This gradient strategy, in synergy with the protective layer, achieves a significant improvement in oxidation selectivity and is one of the core technical means of achieving both high purity and high yield in this invention.

[0090] 3) Compared to Comparative Example 3, the product purity of Example 1 increased from 88.3% to 98.0%, and the extraction yield increased from 76.8% to 86.5%, both showing significant improvements. This comparison indicates that even after the preliminary steps of this invention (protective layer construction + dynamic gradient oxidation), some residual impurities (such as trace amounts of lignin-carbohydrate complexes tightly bound to the gum) still exist in the crude Eucommia ulmoides gum. The single petroleum ether solvent lacks the wetting and stripping properties of surfactants and the emulsifying function of impurities, as well as the swelling and opening effect of a swelling agent on the gum network structure, making it difficult to effectively separate the gum from these residual impurities. The purity of Comparative Example 3 (88.3%) is even lower than that of Comparative Example 1 (89.5%) and Comparative Example 2 (91.2%), possibly because the selective extraction capability of the single petroleum ether solvent is insufficient, extracting some fat-soluble impurities along with the gum, resulting in unsatisfactory product purity. The comparative results fully demonstrate that the synergistic effect between the surfactant (sorbitan monooleate) and swelling agent (γ-valerol) and the main solvent (petroleum ether) in the composite extractant of this invention is indispensable for achieving high-purity and high-yield purification. The synergy of the three components gives the composite extractant the comprehensive advantages of high solubility selectivity, strong impurity removal ability, and good colloidal swelling and penetration effect, which is an important guarantee for achieving the final high-quality product of the process of this invention.

[0091] 4) Compared to Example 1, the product purity in Example 2 increased from 98.0% to 99.2%, and the extraction yield increased from 86.5% to 89.1%. This result indicates that, based on the protective layer and dynamic gradient oxidation, coupling ultrasonic field energy further optimizes the oxidation effect. The cavitation effect and mechanical vibration generated by ultrasound continuously "clean" and "impact" the protective layer and oxidation interface on the surface of the material particles, accelerating the diffusion of ozone into the impurities and the removal of oxidation products. This makes impurity removal more thorough (higher purity), and due to the improved oxidation efficiency, better impurity removal can be achieved without increasing the ozone concentration or extending the reaction time, thereby reducing the potential damage of ozone to Eucommia ulmoides gum and further improving the yield.

[0092] 5) Compared to Example 1, the product purity in Example 3 increased from 98.0% to 98.8%, and the extraction yield increased from 86.5% to 88.6%. This result indicates that pre-vacuuming and maintaining a slight negative pressure further improve process performance. Pre-vacuuming removes air from the reactor and material pores, reducing the dilution and interference of ozone by inert gases, allowing ozone to act more efficiently on the target impurities. Maintaining a slight negative pressure environment facilitates the timely removal of gaseous products generated by the oxidation reaction (such as CO2, small molecule aldehydes and ketones) from the reaction system by the gas flow, promoting the forward oxidation reaction and reducing the accumulation of reaction products on the material surface and secondary reactions. These two improvements allow the oxidation reaction to proceed in a purer, more mass-transfer-friendly environment, resulting in more thorough impurity removal and more adequate protection of the eucommia gum.

[0093] 6) Compared to Example 1, Example 4 showed an increase in product purity from 98.0% to 99.5% and an increase in extraction yield from 86.5% to 90.2%, both of which reached the highest values ​​among all examples. This result demonstrates that multi-stage countercurrent extraction significantly improves the purification effect. Fresh solvent is added in the last stage to contact the material with the lowest gum content, while the material with the highest gum content contacts the gum-rich solvent in the first stage. This countercurrent method maintains a high concentration gradient driving force in each stage, thereby maximizing the dissolution and separation capabilities of the composite extractant. Compared to single-stage extraction, multi-stage countercurrent extraction can more fully dissolve Eucommia gum from the crude gum (higher yield), while multiple selective extractions and separations further remove impurities (higher purity).

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for extracting high-purity Eucommia gum from Eucommia ulmoides raw materials, characterized in that, Includes the following steps: S1. Raw material pretreatment: The Eucommia ulmoides raw material is crushed to obtain plant powder; S2. Protective layer formation: The plant powder is mixed with a protective agent solution and then dried to form a protective coating on the surface of the plant powder particles; S3. Dynamic gradient ozone oxidation: The plant powder coated with the protective layer is placed in a dynamic oxidation reaction environment, and an ozone-containing gas is introduced for oxidation treatment; the oxidation treatment process includes at least two stages, wherein the ozone concentration in the first stage is higher than the ozone concentration in the second stage, and the humidity in the first stage is lower than the humidity in the second stage; S4. Protective layer removal and primary extraction: Remove the protective layer and oxidation decomposition products from the oxidized material, separate the solids, and dry to obtain Eucommia ulmoides crude gum; S5. Refining: The crude Eucommia gum is extracted using an organic solvent, and then concentrated, precipitated, and dried to obtain refined Eucommia gum.

2. The process according to claim 1, characterized in that, The protective agent in step S2 is selected from at least one of water-soluble or alkali-soluble polymeric compounds and nano-inorganic oxides; preferably, the protective agent is selected from at least one of polyvinyl alcohol, sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose and silica sol.

3. The process according to claim 1, characterized in that, In step S2, the mass concentration of the protective agent solution is 1-10 wt%; the mass ratio of the plant powder to the protective agent solution is 100:200~100:

500.

4. The process according to claim 1, characterized in that, In step S3, the ozone concentration in the first stage is 40-80 mg / L, and the ozone concentration in the second stage is 10-30 mg / L; the humidity in the first stage is ≤30% RH, and the humidity in the second stage is 50-80% RH.

5. The process according to claim 4, characterized in that, In step S3, the total time for oxidation treatment is 1-3 hours, and the treatment time of the first stage accounts for 30%-60% of the total time.

6. The process according to claim 1, characterized in that, In step S3, the dynamic oxidation reaction environment is provided by a fluidized bed reactor or a rotary drum reactor.

7. The process according to any one of claims 1 to 6, characterized in that, In step S3, a physical field is coupled and applied simultaneously with the oxidation treatment for synergistic processing. The physical field is an ultrasonic field or a microwave field. The ultrasonic field has a power of 100-500 W and a frequency of 20-40 kHz; the microwave field has a power of 300-800 W.

8. The process according to any one of claims 1 to 6, characterized in that, In step S3, before ozone oxidation treatment, a step of evacuating the dynamic oxidation reaction environment is included, with a vacuum degree of -0.08 to -0.095 MPa; when ozone-containing gas is introduced, the reaction environment pressure is maintained at -0.01 to -0.03 MPa.

9. The process according to any one of claims 1 to 6, characterized in that, The organic solvent in step S5 includes a main solvent, a surfactant, and a swelling agent; The main solvent is petroleum ether; the surfactant is sorbitol monooleate; the swelling agent is γ-valerolactone; and the volume ratio of petroleum ether, sorbitol monooleate, and γ-valerolactone is 1:0.05-0.1:0.05-0.

2.

10. The process according to any one of claims 1 to 6, characterized in that, The refining step in step S5 is performed using a multi-stage countercurrent extraction method; And / or, in step S5, the extract is pre-concentrated using a nanofiltration membrane before the concentration step.