Degradable paper pulp leather containing camellia oil residue and preparation process thereof

Abstract

The application belongs to the field of environmental protection materials, and discloses a degradable paper pulp leather containing camellia oil residue and a preparation process thereof. The degradable paper pulp leather comprises the following raw materials: oil tea shell fiber, cotton pulp, modified nanocellulose, tea saponin iron complex, polyvinyl alcohol, glutaraldehyde and plant-based fatting agent. The modified nanocellulose is cellulose butyrate after surface grafting of an aromatic molecule containing a disulfide bond. The tea saponin iron complex is a stable metal-polyphenol coordination network formed by the surface ortho-phenolic hydroxyl group of tea saponin and trivalent iron. The oil tea shell fiber, nanocellulose and tea saponin are obtained by step-by-step extraction of camellia oil residue. The oil tea shell fiber and tea saponin are extracted from oil tea processing waste, and the extracted nanocellulose and tea saponin are modified, and then combined with the oil tea shell fiber and cotton pulp to prepare the degradable paper pulp leather. The degradable paper pulp leather has good comprehensive performance, realizes high-value utilization of the oil tea processing waste, and has significant environmental and economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection materials technology, specifically relating to a biodegradable pulp leather containing camellia oil residue and its preparation process. Background Technology

[0002] The production of petroleum-based synthetic leather (such as PU and PVC leather) uses large amounts of organic solvents, which are difficult to degrade after disposal, causing serious white pollution. The preparation of natural leather involves high carbon emissions from animal husbandry and heavy metal pollution from chrome tanning processes. Therefore, developing bio-based leather alternatives that combine good performance with environmental friendliness has become a hot topic in the industry. Pulp leather is an environmentally friendly material made from natural plant fibers, attracting attention due to its renewable and biodegradable raw materials. However, existing pulp leathers generally suffer from insufficient mechanical strength, poor flexibility, and poor water resistance. Furthermore, its functionality is limited, lacking intelligent properties such as self-healing and antibacterial properties.

[0003] The processing of camellia oil in my country generates millions of tons of waste (camellia fruit shells and camellia seed meal) annually, most of which is currently incinerated or discarded. Camellia fruit shells are rich in cellulose, and camellia seed meal is rich in tea saponins. However, current technologies primarily utilize camellia waste for low-value purposes, with no reports of its use for functional modification of pulp and leather. While nanocellulose can be used as a reinforcing filler, ordinary nanocellulose is highly hydrophilic, has poor compatibility with the matrix, is prone to aggregation, and cannot impart self-healing functions to materials. Although tea saponins possess natural antibacterial activity, they are easily inactivated and lost during composite material processing, and have weak bonding with the fiber matrix.

[0004] Therefore, how to utilize camellia oil waste to develop biodegradable pulp leather with high strength, good hydrophobicity, self-healing and antibacterial functions is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the shortcomings mentioned in the background art, the present invention aims to provide a biodegradable pulp leather containing camellia oil residue and its preparation process. The present invention extracts camellia shell fiber and tea saponin from camellia oil processing waste, and then modifies the extracted nanocellulose and tea saponin, and prepares biodegradable pulp leather by combining it with camellia shell fiber and cotton pulp. This biodegradable pulp leather has good comprehensive performance, realizes the high-value utilization of camellia oil processing waste, and has significant environmental and economic benefits.

[0006] The objective of this invention can be achieved through the following technical solutions: A biodegradable pulp leather containing camellia oil residue comprises the following raw materials in parts by weight: 30-50 parts camellia shell fiber, 50-70 parts cotton pulp, 3-8 parts modified nanocellulose, 4-8 parts tea saponin iron complex, 5-10 parts polyvinyl alcohol, 0.5-1 parts glutaraldehyde, and 2-5 parts plant-based fatliquoring agent. The modified nanocellulose is obtained by butyrate esterification of nanocellulose obtained from camellia oil residue, followed by grafting of aromatic molecules containing disulfide bonds onto its surface; the tea saponin iron complex is obtained by separating tea saponin from camellia oil residue, utilizing the ortho- and ferric hydroxyl groups on its surface to form a stable metal-polyphenol coordination network with trivalent iron.

[0007] Preferably, the plant-based fatliquoring agent is soybean lecithin.

[0008] Preferably, camellia shell fiber, nanocellulose, and tea saponin are obtained through stepwise extraction from camellia oil residue.

[0009] Preferably, the stepwise extraction process of camellia oil residue specifically includes the following steps: (1) The camellia oil residue was crushed and passed through a 40-60 mesh sieve. It was added to 60-70 Vol% ethanol at a solid-liquid ratio of 1:8-12 g / mL and extracted by reflux at 70-80℃ for 1-2 hours. The extraction was repeated 2-3 times. The extracts were combined and concentrated by rotary evaporation to 1 / 5-1 / 10 of the original volume. Then, 3-5 times the volume of 85-95 Vol% ethanol was added to the concentrate for alcohol precipitation. The solution was treated at 60-80℃ for 1-3 hours. The precipitate was collected by centrifugation and dried to obtain crude tea saponin. Tea saponin was obtained by recrystallization using a water-containing ethanol-acetone composite solvent. (2) Wash and dry the camellia oil residue after alcohol extraction in step (1), add sodium hydroxide / sodium sulfite mixed solution at a solid-liquid ratio of 1:10~15 g / mL, stir at 50~90℃ for 1~3h, filter and wash until neutral while hot, then add sodium hydroxide solution at a solid-liquid ratio of 1:10~15 g / mL, stir at 50~80℃ for 1~2h, filter and wash until neutral while hot, and vacuum dry to obtain camellia shell fiber; (3) The camellia shell fiber obtained in step (2) is added to a 65wt% sulfuric acid solution pre-cooled to 10℃ at a solid-liquid ratio of 1:10~20 g / mL. The temperature is raised to 45℃ and hydrolyzed by stirring at a constant temperature for 20~40 min. A large amount of ice water is added to terminate the reaction. The mixture is centrifuged and washed with deionized water 3~5 times until the pH of the supernatant is 6~7. The suspension is placed in a dialysis bag and dialyzed with deionized water until neutral. The nanocellulose is dispersed by ultrasonication and then freeze-dried to obtain nanocellulose.

[0010] Preferably, the method for preparing modified nanocellulose includes the following steps: A. The nanocellulose obtained from camellia oil residue was dispersed in anhydrous pyridine, excess butyric anhydride was added, and the reaction was carried out at 60℃ for 20-24h. After centrifugation, the precipitate was washed and dried to obtain butyric acid esterified nanocellulose. B. Butylated nanocellulose and 4,4'-dithiodiphenylamine were added to anhydrous dichloromethane and stirred to dissolve in a nitrogen atmosphere. Dicyclohexylcarbodiimide was then added and the mixture was stirred at 40°C for 8-12 hours. C. After the reaction is complete, precipitate with excess anhydrous ethanol, filter and separate, wash with anhydrous ethanol 3-5 times to remove unreacted small molecules, and vacuum dry to obtain modified nanocellulose.

[0011] Preferably, the mass ratio of butyrate-esterified nanocellulose, 4,4'-dithiodiphenylamine, and dicyclohexylcarbodiimide is 10:1:0.4.

[0012] Preferably, the preparation method of the tea saponin iron complex includes the following steps: a. Dissolve tea saponin extracted from camellia oil residue in a glycerol / PEG400 mixed solvent, add 1wt% sulfuric acid solution to adjust the pH to 3~4.5, react at 140℃ for 1~2h to obtain liquefied tea saponin; b. Cool the liquefied tea saponin to room temperature, and slowly add 0.1~0.15 mol / L ferric chloride solution dropwise. After the addition is complete, stir at room temperature for 30~50 min. c. After the reaction is complete, adjust the pH of the system to 6.5-7.0 with 5wt% ammonia water, centrifuge to collect the bottom precipitate, and obtain the tea saponin iron coordination complex.

[0013] Preferably, the molar ratio of tea saponin to ferric chloride is 2~3:1.

[0014] A method for preparing biodegradable pulp leather containing camellia oil residue includes the following steps: S1. Add camellia shell fiber, cotton pulp, modified nanocellulose, and tea saponin iron complex to an appropriate amount of water, and disperse them in a standard fiber disintegrator for 10-15 minutes until a uniform slurry suspension is formed. S2. Transfer the pulp to the paper machine, add polyvinyl alcohol, homogenize with bubbles for 2-3 minutes, remove water, transfer the wet paper blank to a vacuum platen dryer, and dry it at 80-100℃ and 0.3-0.5 MPa for 10-15 minutes to obtain the base material; S3. Dissolve glutaraldehyde in phosphate buffer solution with pH 5.0~6.0 to prepare a 0.5~1.5wt% glutaraldehyde solution. Immerse the substrate material in the glutaraldehyde solution and immerse it at room temperature for 30~60 min. After immersion, rinse it with deionized water 2~3 times and dry it with a forced air to obtain the crosslinked modified substrate material. S4. Emulsify and dilute the plant-based fatliquoring agent with hot water at 45~55℃, apply it evenly to the surface of the cross-linked base material by spraying or dipping, dry and cure, and emboss it by heating a steel roller to obtain biodegradable pulp leather containing camellia oil residue.

[0015] Preferably, in step S1, camellia husk fiber, cotton pulp, modified nanocellulose, and tea saponin iron complex are added to water at a solid-liquid ratio of 1:20 g / mL.

[0016] The beneficial effects of this invention are: This invention first extracts camellia shell fiber and tea saponin from camellia oil processing waste, and then modifies the extracted nanocellulose by butyrate esterification and dynamic disulfide bond grafting to prepare dynamically disulfide bond modified nanocellulose; simultaneously, the tea saponin is subjected to Fe... 3+ Coordination modification was performed to prepare a tea saponin iron coordination complex. The two modified additives were then combined with camellia oleifera shell fiber and cotton pulp, and processed through papermaking, cross-linking, and fatliquoring to obtain biodegradable pulp leather. The pulp leather obtained by this invention not only possesses excellent mechanical properties and hydrophobicity, but also exhibits intelligent functions such as self-healing and antibacterial properties. Simultaneously, it achieves high-value utilization of camellia oleifera processing waste, demonstrating significant environmental and economic benefits.

[0017] This invention modifies nanocellulose through dynamic disulfide bonds on its surface, allowing for reversible breakage and recombination under external forces, effectively dissipating energy and delaying crack propagation. The disulfide bonds undergo an exchange reaction at 50-60°C, reconnecting damaged interfaces. Butyrate modification transforms the nanocellulose from hydrophilic to amphiphilic, reducing aggregation and resulting in superior reinforcing effects compared to ordinary nanocellulose. Butyrate modification and the densification of the dynamic network also contribute to reducing water absorption and increasing char content.

[0018] Fe in the iron complex of tea saponin of this invention 3+ The coordination network formed with tea saponins constitutes a physical barrier on the fiber surface and in the interstitial spaces, hindering the entry of water molecules. The tea saponin-iron complex acts as a molecular bridge, simultaneously anchoring hydrophilic fibers and hydrophobic matrices (PVA, fatliquoring agents), enhancing interfacial bonding. The tea saponins in the tea saponin-iron complex disrupt bacterial cell membranes, and the Fe... 3+ It generates reactive oxygen species, forming a dual antibacterial mechanism, and the iron complex of tea saponin stabilizes the activity of tea saponin, preventing inactivation and loss during processing. 3+ Catalytic dehydration and carbonization of cellulose at high temperatures forms a protective carbon layer, which improves thermal stability.

[0019] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Example 1

[0021] A stepwise extraction process for camellia oil residue includes the following steps: (1) The camellia oil residue was crushed and passed through a 40-60 mesh sieve. It was added to 65 Vol% ethanol at a solid-liquid ratio of 1:10 g / mL and extracted by reflux at 75℃ for 1.5h. The extraction was repeated 2-3 times. The extracts were combined and concentrated to 1 / 8 of the original volume by rotary evaporation. Then, 4 times the volume of 90 Vol% ethanol was added to the concentrate for alcohol precipitation. The mixture was treated at 70℃ for 2h. The precipitate was collected by centrifugation and dried to obtain crude tea saponin. Tea saponin was obtained by recrystallization using a water-containing ethanol-acetone composite solvent. (2) Wash and dry the camellia oil residue after alcohol extraction in step (1), add a mixed solution of sodium hydroxide (2.5wt%) / sodium sulfite (2wt%) at a solid-liquid ratio of 1:12 g / mL, stir at 70℃ for 2h, filter and wash until neutral while hot, then add sodium hydroxide solution (15wt%) at a solid-liquid ratio of 1:12 g / mL, stir at 65℃ for 1.5h, filter and wash until neutral while hot, and vacuum dry to obtain camellia shell fiber; (3) The camellia shell fiber obtained in step (2) was added to a 65wt% sulfuric acid solution pre-cooled to 10℃ at a solid-liquid ratio of 1:15 g / mL. The temperature was raised to 45℃ and hydrolyzed by stirring at a constant temperature for 30 min. A large amount of ice water was added to terminate the reaction. The mixture was centrifuged and washed with deionized water 3 to 5 times until the pH of the supernatant was 6 to 7. The suspension was placed in a dialysis bag and dialyzed with deionized water until neutral. The nanocellulose was dispersed by ultrasonication and then freeze-dried to obtain nanocellulose. Example 2

[0022] A modified nanocellulose, which is obtained from the butyrate separation of camellia oil residue in Example 1, has its surface grafted with aromatic molecules containing disulfide bonds after butyrate esterification. Its preparation method includes the following steps: A. Nanocellulose obtained from camellia oil residue was dispersed in anhydrous pyridine, excess butyric anhydride was added, the reaction was carried out at 60℃ for 22h, centrifuged, the precipitate was washed and dried to obtain butyric acid esterified nanocellulose. B. In a nitrogen atmosphere, 5g of butyrate-esterified nanocellulose and 0.5g of 4,4'-dithiodiphenylamine were added to 50mL of anhydrous dichloromethane and stirred until dissolved. Then, 0.2g of dicyclohexylcarbodiimide was added, and the mixture was stirred at 40℃ for 10h. C. After the reaction is complete, precipitate with excess anhydrous ethanol, filter and separate, wash with anhydrous ethanol 3-5 times to remove unreacted small molecules, and vacuum dry to obtain modified nanocellulose. Example 3

[0023] A tea saponin iron complex, which is a stable metal-polyphenol coordination network formed by the tea saponin obtained from the camellia oil residue separation in Example 1, utilizes the ortho- and ferric hydroxyl groups on its surface to form a complex. The preparation method includes the following steps: a. Dissolve 10g of tea saponin extracted from camellia oil residue in 50mL of glycerol / PEG400 (v:v=1:1) mixed solvent, add 1wt% sulfuric acid solution to adjust pH to 3~4.5, react at 140℃ for 1.5h to obtain liquefied tea saponin; b. Cool the liquefied tea saponin to room temperature, and slowly add 20 mL of 0.12 mol / L ferric chloride solution. After the addition is complete, stir at room temperature for 40 min. c. After the reaction is complete, adjust the pH of the system to 6.5-7.0 with 5wt% ammonia water, centrifuge to collect the bottom precipitate, and obtain the tea saponin iron coordination complex. Example 4

[0024] A biodegradable pulp leather containing camellia oil residue comprises the following raw materials in parts by weight: 30 parts camellia shell fiber, 50 parts cotton pulp, 3 parts modified nanocellulose, 4 parts tea saponin iron complex, 5 parts polyvinyl alcohol, 0.5 parts glutaraldehyde, and 2 parts plant-based fatliquoring agent; the camellia shell fiber is obtained by separating camellia oil residue in Example 1, the modified nanocellulose is prepared in Example 2, and the tea saponin iron complex is prepared in Example 3.

[0025] The above-mentioned method for preparing biodegradable pulp leather containing camellia oil residue includes the following steps: S1. Add camellia shell fiber, cotton pulp, modified nanocellulose, and tea saponin iron complex to water at a solid-liquid ratio of 1:20 g / mL, and disperse in a standard fiber dispersant for 10 min until a uniform slurry suspension is formed. S2. Transfer the pulp to the paper machine, add polyvinyl alcohol, homogenize with bubbles for 2 minutes, remove water, transfer the wet paper blank to a vacuum platen dryer, and dry it at 80℃ and 0.3MPa for 10 minutes to obtain the base material. S3. Dissolve glutaraldehyde in phosphate buffer solution with pH 5.0-6.0 to prepare a 0.5wt% glutaraldehyde solution. Immerse the substrate material in the glutaraldehyde solution and treat it at room temperature for 30 minutes. After removing it, rinse it with deionized water 2-3 times and dry it with a forced air to obtain the crosslinked modified substrate material. S4. The plant-based fatliquoring agent is emulsified and diluted with hot water at 45°C, and then applied evenly to the surface of the cross-linked base material by spraying or dipping. After drying and curing, the material is embossed by heating a steel roller to obtain the biodegradable pulp leather containing camellia oil residue. Example 5

[0026] A biodegradable pulp leather containing camellia oil residue comprises the following raw materials in parts by weight: 50 parts camellia shell fiber, 70 parts cotton pulp, 8 parts modified nanocellulose, 8 parts tea saponin iron complex, 10 parts polyvinyl alcohol, 1 part glutaraldehyde, and 5 parts plant-based fatliquoring agent; the camellia shell fiber is obtained by separating camellia oil residue in Example 1, the modified nanocellulose is prepared in Example 2, and the tea saponin iron complex is prepared in Example 3.

[0027] The above-mentioned method for preparing biodegradable pulp leather containing camellia oil residue includes the following steps: S1. Add camellia shell fiber, cotton pulp, modified nanocellulose, and tea saponin iron complex to water at a solid-liquid ratio of 1g / 20mL, and disperse in a standard fiber dispersant for 15min until a uniform slurry suspension is formed. S2. Transfer the pulp to the paper machine, add polyvinyl alcohol, homogenize with bubbles for 3 minutes, remove the water, transfer the wet paper blank to a vacuum platen dryer, and dry it at 100℃ and 0.5MPa for 15 minutes to obtain the base material. S3. Dissolve glutaraldehyde in phosphate buffer solution with pH 5.0-6.0 to prepare a 1.5wt% glutaraldehyde solution. Immerse the substrate material in the glutaraldehyde solution and immerse it at room temperature for 60 minutes. After immersion, rinse it with deionized water 2-3 times and dry it with a forced air to obtain the crosslinked modified substrate material. S4. The plant-based fatliquoring agent is emulsified and diluted with hot water at 55°C, and then applied evenly to the surface of the cross-linked base material by spraying or dipping. After drying and curing, the material is embossed by heating a steel roller to obtain the biodegradable pulp leather containing camellia oil residue. Example 6

[0028] A biodegradable pulp leather containing camellia oil residue comprises the following raw materials in parts by weight: 40 parts camellia shell fiber, 60 parts cotton pulp, 5.5 parts modified nanocellulose, 6 parts tea saponin iron complex, 7.5 parts polyvinyl alcohol, 0.8 parts glutaraldehyde, and 3.5 parts plant-based fatliquoring agent; the camellia shell fiber is obtained by separating camellia oil residue in Example 1, the modified nanocellulose is prepared in Example 2, and the tea saponin iron complex is prepared in Example 3.

[0029] The above-mentioned method for preparing biodegradable pulp leather containing camellia oil residue includes the following steps: S1. Add camellia husk fiber, cotton pulp, modified nanocellulose, and tea saponin iron complex to water at a solid-liquid ratio of 1g / 20mL, and disperse in a standard fiber dispersant for 12min until a uniform slurry suspension is formed. S2. Transfer the pulp to the paper machine, add polyvinyl alcohol, homogenize with bubbles for 2.5 min, remove water, transfer the wet paper blank to a vacuum platen dryer, and dry at 90℃ and 0.4MPa for 12 min to obtain the base material; S3. Dissolve glutaraldehyde in phosphate buffer solution with pH 5.0~6.0 to prepare a 1wt% glutaraldehyde solution. Immerse the substrate material in the glutaraldehyde solution and immerse it at room temperature for 45 minutes. After immersion, rinse it with deionized water 2~3 times and dry it with a forced air to obtain the crosslinked modified substrate material. S4. The plant-based fatliquoring agent is emulsified and diluted with hot water at 50°C, and then applied evenly to the surface of the cross-linked base material by spraying or dipping. After drying and curing, the material is embossed by heating a steel roller to obtain the biodegradable pulp leather containing camellia oil residue.

[0030] Comparative Example 1 A biodegradable pulp leather containing camellia oil residue comprises the following raw materials in parts by weight: 40 parts camellia shell fiber, 60 parts cotton pulp, 5.5 parts nanocellulose, 6 parts tea saponin iron complex, 7.5 parts polyvinyl alcohol, 0.8 parts glutaraldehyde, and 3.5 parts plant-based fatliquoring agent; the camellia shell fiber is obtained by separating camellia oil residue in Example 1, the nanocellulose is prepared in Example 1, and the tea saponin iron complex is prepared in Example 3.

[0031] The preparation method of the biodegradable pulp leather containing camellia oil residue is the same as that in Example 6, except that in step S1, the modified nanocellulose is replaced with an equal amount of unmodified nanocellulose (prepared in Example 1).

[0032] Comparative Example 2 A biodegradable pulp leather containing camellia oil residue comprises the following raw materials in parts by weight: 40 parts camellia shell fiber, 60 parts cotton pulp, 5.5 parts modified nanocellulose, 6 parts tea saponin, 7.5 parts polyvinyl alcohol, 0.8 parts glutaraldehyde, and 3.5 parts plant-based fatliquoring agent; the camellia shell fiber is obtained by separating camellia oil residue in Example 1, the modified nanocellulose is prepared in Example 2, and the tea saponin is prepared in Example 1.

[0033] The preparation method of biodegradable pulp leather containing camellia oil residue is the same as in Example 6, except that in step S1, the tea saponin iron complex is replaced with an equal amount of unmodified tea saponin (prepared in Example 1).

[0034] Performance testing To verify the performance-enhancing effect of the modified nanocellulose and tea saponin iron complex, the biodegradable pulp leather containing camellia oil residue prepared in Examples 4-6 and Comparative Examples 1-2 were subjected to the following performance tests: (1) Tensile strength and elongation at break Referring to GB / T 1040.3-2006 (Determination of tensile properties of plastics) and GB / T 12914-2018 (Determination of tensile strength of paper and paperboard), the specimens were cut into dumbbell shapes (100 mm in length and 10 mm in width at the narrow end). A universal testing machine was used to conduct a tensile test at a tensile speed of 10 mm / min. The maximum force (F_max) and the gauge length increment at break (ΔL) were recorded, and the tensile strength and elongation at break were calculated. (2) Flexural endurance Referring to GB / T457-2008 (Determination of folding endurance of paper and paperboard - MIT method), the sample was cut into a standard sample of 150mm×15mm, the sample was fixed on the MIT folding endurance tester, and folded at a speed of 175 times / min with a folding angle of 135°. The number of double folds when the sample broke was recorded. If the test did not break after more than 5000 times, the test could be terminated and recorded as >5000 times. (3) Water absorption Referring to GB / T 1540-2002 (Determination of water absorption of paper and paperboard - Cobb method), the sample was cut into a circular standard sample with a diameter of 125 mm. The dry weight of the sample was weighed, and the measurement points (100 mm gauge length) were marked. The sample was fixed between the cylinder and the base of the Cobb absorbency tester, and 100 mL of distilled water was poured in. After 24 hours, the water was poured out, the free water on the surface was absorbed, and the wet weight was weighed immediately. The length change was measured, and the water absorption rate (%) and dimensional change rate (%) were calculated. Water absorption rate = (weight of sample after moisture absorption - weight of dry sample) / weight of dry sample × 100%, dimensional change rate = (length of sample after moisture absorption - length of dry sample) / length of dry sample × 100%. (4) Self-healing performance The repair efficiency is quantified by comparing the mechanical properties (tensile strength) before and after repair. The specimen is cut into a standard tensile specimen (dumbbell shape), the initial tensile strength is tested, and then a 10mm incision is made perpendicular to the tensile direction with a scalpel. The incision depth is 50-70% of the material thickness. The specimen is then placed in a constant temperature and humidity chamber at 50-60℃ and 40-60%RH for 8 hours. The tensile strength after repair is then tested, and the repair efficiency (%) is calculated as follows: Repair efficiency = (Tensile strength of the repaired specimen / Initial tensile strength) × 100%. (5) Thermal properties Thermogravimetric analysis was performed in accordance with GB / T 13464-2008 (Thermogravimetric Analysis). A thermogravimetric analyzer was used. 10 mg of sample was weighed and heated from room temperature to 800 °C at a rate of 10 °C / min. The temperature at which the mass loss was 5% and the char residue (the remaining mass fraction after constant weight) were recorded. (6) Antibacterial properties According to GB / T 20944.3-2008 (Evaluation of Antimicrobial Properties of Textiles - Shaking Method), the antimicrobial properties against Staphylococcus aureus (ATCC 6538) and Escherichia coli (ATCC 8739) were tested. Standard strains were inoculated onto nutrient agar slants and incubated at 37℃ for 18-24 h. The bacterial growth was washed off with 0.03 mol / L phosphate-buffered saline (PBS) and diluted to 10⁻⁶. 6 ~10 7 CFU / mL, cut 0.5g of sample (accurately), sterilize, add the sample to an Erlenmeyer flask containing 5mL of bacterial solution, shake at 24℃ and 150rpm for 18~24h, take the contact solution for serial dilution, spread on plates, incubate at 37℃ for 24~48h, count the number of colonies, set up a blank cotton cloth as a negative control, calculate the inhibition rate (%), inhibition rate = (number of viable bacteria in blank control group - number of viable bacteria in experimental group) / number of viable bacteria in blank control group × 100%.

[0035] The obtained data is shown in Table 1 below.

[0036] Table 1. Test results of biodegradable pulp and leather containing camellia oil residue. Tensile strength (MPa) 3.05 4.18 3.62 2.71 2.48 Elongation at break (%) 6.8 11.5 8.9 5.2 4.1 Flexural endurance (times) 890 1820 1380 710 480 24-hour water absorption rate (%) 72.8 48.3 56.8 91.2 98.5 Dimensional change rate (%) 3.6 1.8 2.5 5.3 5.8 Self-repair rate (%) 64 88 79 8 6 T5%（℃） 188 207 198 182 177 Carbon residue rate (%) 14.2 19.6 16.8 12.5 10.2 Staphylococcus aureus inhibition rate (%) 76.3 91.2 86.5 71.8 27.3 Escherichia coli inhibition rate (%) 71.5 86.8 81.2 66.2 23.6 As shown in Table 1, the tensile strength of Examples 4-6 is significantly better than that of Comparative Examples 1-2. Furthermore, the tensile strength in Examples 4-6 is directly proportional to the content of modified nanocellulose and the tea saponin iron complex, indicating a synergistic reinforcing effect. Nanocellulose has an extremely high aspect ratio, enabling it to form numerous hydrogen bonds and physical entanglements with the fiber matrix. With increasing addition, the bridging effect of nanocellulose becomes denser, effectively transferring and dispersing stress, thereby improving tensile strength. The Fe in the tea saponin iron complex... 3+ The coordination network formed with tea saponin can establish molecular bridges between the fiber and the matrix, increasing the interfacial bonding force. As the amount added increases, the density of interfacial bonding points also increases.

[0037] The elongation at break and flexural endurance of Examples 5 and 6 were significantly higher than those of Comparative Examples 1 and 2. Furthermore, the higher the content of modified nanocellulose, the higher the toughness index, indicating that modified nanocellulose is key to improving toughness. The disulfide bonds (-SS-) grafted onto the surface of modified nanocellulose can undergo reversible fracture and recombination when the material is subjected to stress. This process dissipates energy and prevents rapid crack propagation. Higher addition amounts result in a greater density of dynamic crosslinking points and stronger energy dissipation capacity, thus significantly improving elongation at break and flexural endurance.

[0038] The water absorption rates of Examples 4-6 were significantly lower than those of Comparative Examples 1-2. The higher the content of the tea saponin iron complex, the lower the water absorption rate. Dimensional stability followed the same trend as water absorption rate. The Fe in the tea saponin iron complex... 3+The coordination network formed with tea saponin constitutes a three-dimensional hydrophobic barrier. This network covers the fiber surface and the gaps between fibers, physically blocking the pathway for water molecules to enter the material's interior. The hydrophobic triterpenoid saponin skeleton contained in tea saponin itself also contributes to the hydrophobic properties. The greater the amount added, the denser the hydrophobic network and the lower the water absorption rate. The butyrate modification of the modified nanocellulose also introduces a certain degree of hydrophobicity (butyrate groups). When the contents of both modified nanocellulose and tea saponin iron complex in Example 5 are relatively high, the reduction in water absorption is greater than the simple sum of their independent effects, indicating a synergistic hydrophobic effect between the two substances. The nanofilling of the modified nanocellulose further densifies the micropores in the tea saponin iron complex network.

[0039] Only Examples 4-6 exhibit self-healing capabilities. Higher modified nanocellulose content results in higher repair rates and shorter repair times, while Comparative Examples 1 and 2 show virtually no self-healing. This directly reflects the reversible exchange reaction of dynamic disulfide bonds (-SS-). Under heating conditions of 50-60°C, disulfide bonds break and recombine. When microcracks appear on the material surface, the exposed dynamic disulfide bonds on both sides of the crack undergo an exchange reaction under thermal excitation, reconnecting into a network, thereby achieving healing. Higher modified nanocellulose concentrations result in a greater number of dynamic disulfide bonds per unit volume, denser healing sites, and higher repair efficiency and speed. Modified nanocellulose is an irreplaceable contributor to self-healing performance; tea saponin iron complexes contribute almost nothing to this function.

[0040] Examples 4-6 exhibit better thermal stability than Comparative Examples 1-2. Higher content of the tea saponin iron complex results in a higher T5%, and the modified composition shows a significantly higher char rate than the unmodified group. The tea saponin iron complex dominates char formation, with modified nanocellulose as an auxiliary agent. The Fe content in the tea saponin iron complex... 3+ It has a catalytic effect on carbonization at high temperatures. Fe 3+ The modified nanocellulose promotes the dehydration and carbonization reaction of cellulose, forming a protective carbon layer and inhibiting further thermal degradation. Although it does not have a direct catalytic effect, its uniform dispersion enhances the overall network structure and delays the release of volatile products during thermal decomposition. The dual structure of coordination network and dynamic cross-linked network also provides a certain skeletal support at high temperatures.

[0041] Example 5 showed an inhibition rate of over 90% against Staphylococcus aureus. The higher the content of the tea saponin iron complex, the higher the inhibition rate; the tea saponin iron complex was the sole contributor to the antibacterial performance. Tea saponin itself possesses surface activity, capable of disrupting the integrity of bacterial cell membranes, leading to leakage of intracellular substances. 3+ After coordination, the antibacterial activity of tea saponins may be enhanced through the following mechanisms: ① the coordination structure stabilizes the active conformation of tea saponins; ② Fe 3+It has a certain antibacterial effect (Fenton reaction produces reactive oxygen species). As the concentration of tea saponin iron complex increases, the density of antibacterial sites increases and the antibacterial rate rises; however, when the surface coverage becomes saturated, further increasing the dosage reduces the effect.

[0042] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0043] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A biodegradable pulp leather containing camellia oil residue, characterized in that, The raw materials include the following parts by weight: 30-50 parts of camellia shell fiber, 50-70 parts of cotton pulp, 3-8 parts of modified nanocellulose, 4-8 parts of tea saponin iron complex, 5-10 parts of polyvinyl alcohol, 0.5-1 part of glutaraldehyde, and 2-5 parts of plant-based fatliquoring agent; The modified nanocellulose is nanocellulose obtained from camellia oil residue, which is butyrate-treated and then grafted with aromatic molecules containing disulfide bonds on its surface; the tea saponin iron complex is tea saponin obtained from camellia oil residue, which utilizes the ortho- and ferric hydroxyl groups on its surface to form a stable metal-polyphenol coordination network with trivalent iron.

2. The biodegradable pulp leather containing camellia oil residue according to claim 1, characterized in that, The plant-based fatliquoring agent is soybean lecithin.

3. The biodegradable pulp leather containing camellia oil residue according to claim 1, characterized in that, The camellia shell fiber, nanocellulose, and tea saponin were obtained through stepwise extraction from camellia oil residue.

4. The biodegradable pulp leather containing camellia oil residue according to claim 3, characterized in that, The stepwise extraction process for camellia oil residue specifically includes the following steps: (1) The camellia oil residue was crushed and passed through a 40-60 mesh sieve. It was added to 60-70 Vol% ethanol at a solid-liquid ratio of 1:8-12 g / mL and extracted by reflux at 70-80℃ for 1-2 hours. The extraction was repeated 2-3 times. The extracts were combined and concentrated by rotary evaporation to 1 / 5-1 / 10 of the original volume. Then, 3-5 times the volume of 85-95 Vol% ethanol was added to the concentrate for alcohol precipitation. The solution was treated at 60-80℃ for 1-3 hours. The precipitate was collected by centrifugation and dried to obtain crude tea saponin. Tea saponin was obtained by recrystallization using a water-containing ethanol-acetone composite solvent. (2) Wash and dry the camellia oil residue after alcohol extraction in step (1), add sodium hydroxide / sodium sulfite mixed solution at a solid-liquid ratio of 1:10~15 g / mL, stir at 50~90℃ for 1~3h, filter and wash until neutral while hot, then add sodium hydroxide solution at a solid-liquid ratio of 1:10~15 g / mL, stir at 50~80℃ for 1~2h, filter and wash until neutral while hot, and vacuum dry to obtain camellia shell fiber; (3) The camellia shell fiber obtained in step (2) is added to a 65wt% sulfuric acid solution pre-cooled to 10℃ at a solid-liquid ratio of 1:10~20 g / mL. The temperature is raised to 45℃ and hydrolyzed by stirring at a constant temperature for 20~40 min. A large amount of ice water is added to terminate the reaction. The mixture is centrifuged and washed with deionized water 3~5 times until the pH of the supernatant is 6~7. The suspension is placed in a dialysis bag and dialyzed with deionized water until neutral. The nanocellulose is dispersed by ultrasonication and freeze-dried to obtain nanocellulose.

5. The biodegradable pulp leather containing camellia oil residue according to claim 1, characterized in that, The preparation method of the modified nanocellulose includes the following steps: A. The nanocellulose obtained from camellia oil residue was dispersed in anhydrous pyridine, excess butyric anhydride was added, and the reaction was carried out at 60℃ for 20-24h. After centrifugation, the precipitate was washed and dried to obtain butyric acid esterified nanocellulose. B. Butylated nanocellulose and 4,4'-dithiodiphenylamine were added to anhydrous dichloromethane and stirred to dissolve in a nitrogen atmosphere. Dicyclohexylcarbodiimide was then added and the mixture was stirred at 40°C for 8-12 hours. C. After the reaction is complete, precipitate with excess anhydrous ethanol, filter and separate, wash with anhydrous ethanol 3-5 times to remove unreacted small molecules, and vacuum dry to obtain modified nanocellulose.

6. The biodegradable pulp leather containing camellia oil residue according to claim 5, characterized in that, The mass ratio of butyrate-esterified nanocellulose, 4,4'-dithiodiphenylamine, and dicyclohexylcarbodiimide is 10:1:0.

4.

7. The biodegradable pulp leather containing camellia oil residue according to claim 1, characterized in that, The preparation method of the tea saponin iron complex includes the following steps: a. Dissolve tea saponin extracted from camellia oil residue in a glycerol / PEG400 mixed solvent, add 1wt% sulfuric acid solution to adjust the pH to 3~4.5, react at 140℃ for 1~2h to obtain liquefied tea saponin; b. Cool the liquefied tea saponin to room temperature, and slowly add 0.1~0.15 mol / L ferric chloride solution dropwise. After the addition is complete, stir at room temperature for 30~50 min. c. After the reaction is complete, adjust the pH of the system to 6.5-7.0 with 5wt% ammonia water, centrifuge to collect the bottom precipitate, and obtain the tea saponin iron coordination complex.

8. The biodegradable pulp leather containing camellia oil residue according to claim 7, characterized in that, The molar ratio of tea saponin to ferric chloride is 2~3:

1.

9. The method for preparing biodegradable pulp leather containing camellia oil residue as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Add camellia shell fiber, cotton pulp, modified nanocellulose, and tea saponin iron complex to an appropriate amount of water, and disperse them in a standard fiber disintegrator for 10-15 minutes until a uniform slurry suspension is formed. S2. Transfer the pulp to the paper machine, add polyvinyl alcohol, homogenize with bubbles for 2-3 minutes, remove water, transfer the wet paper blank to a vacuum platen dryer, and dry it at 80-100℃ and 0.3-0.5 MPa for 10-15 minutes to obtain the base material; S3. Dissolve glutaraldehyde in phosphate buffer solution with pH 5.0~6.0 to prepare a 0.5~1.5wt% glutaraldehyde solution. Immerse the substrate material in the glutaraldehyde solution and immerse it at room temperature for 30~60 min. After immersion, rinse it with deionized water 2~3 times and dry it with a forced air to obtain the crosslinked modified substrate material. S4. The plant-based fatliquoring agent is emulsified and diluted with hot water at 45~55℃, and applied evenly to the surface of the cross-linked base material by spraying or dipping. After drying and curing, the material is embossed by heating a steel roller to obtain the biodegradable pulp leather containing camellia oil residue.

10. The method for preparing biodegradable pulp leather containing camellia oil residue according to claim 9, characterized in that, In step S1, camellia husk fiber, cotton pulp, modified nanocellulose, and tea saponin iron complex are added to water at a solid-liquid ratio of 1:20 g / mL.