Preparation method of nano cellulose composite raw material containing antibacterial agent

Abstract

The invention discloses a preparation method of a nano-crystalline cellulose composite raw material containing an antibacterial agent, and relates to the technical field of material preparation, the preparation method comprises preparation of the nano-crystalline cellulose composite raw material, and the preparation method of the nano-crystalline cellulose composite raw material containing the antibacterial agent comprises the steps of raw material preparation, antibacterial agent loading and composite forming. The raw materials comprise a natural fiber raw material, tea polyphenol, a chitosan acetic acid solution, a nano cellulose suspension and plant essential oil, the natural cellulose raw material comprises wood pulp, bamboo pulp and cotton fibers, an antibacterial agent is loaded in-situ polymerization, and the composite molding comprises functional additive mixing and hot press molding drying. In the hot pressing process, nanocellulose molecular chains are rearranged and interwoven under the action of temperature and pressure, meanwhile, reinforcing agents such as lignin and the like are further fused with nanocellulose, and a glycerol plasticizer plays a role, so that the material has better flexibility and plasticity, and finally a compact blocky composite raw material is formed.

Description

Technical Field

[0001] The present invention relates to the technical field of material preparation, in particular to a method for preparing a nano-cellulose composite raw material containing an antibacterial agent. Background Art

[0002] As people pay more and more attention to environmental protection and health, the development and application of green natural materials have become a research hotspot. Nanocellulose, as a new type of nanomaterial derived from natural cellulose, has the advantages of high strength, high specific surface area, good biocompatibility and degradability, and has shown great application potential in many fields. However, the antibacterial properties of pure nanocellulose itself are limited, which limits its application in some fields with high requirements for antibacterial properties, such as food packaging, medical and health care, etc. At present, although there are some methods to compound antimicrobial agents with nanocellulose, there are problems such as uneven distribution of antimicrobial agents, unstable binding with nanocellulose, and complex and environmentally unfriendly preparation process, which leads to the inability to fully improve the performance and added value of the composite raw materials. To this end, we propose a method for preparing nanocellulose composite raw materials containing antimicrobial agents. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing a nanocellulose composite raw material containing an antibacterial agent.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solutions: a method for preparing a nanocellulose composite raw material containing an antimicrobial agent, comprising preparing a nanocellulose composite raw material, wherein the method for preparing a nanocellulose composite raw material containing an antimicrobial agent comprises raw material preparation, antimicrobial agent loading, and composite molding, wherein the raw materials comprise natural fiber raw materials, tea polyphenols, chitosan acetic acid solution, nanocellulose suspension, and plant essential oils, wherein the natural cellulose raw materials comprise wood pulp, bamboo pulp, and cotton fiber, wherein the antimicrobial agent loading is performed by in-situ polymerization, wherein the composite molding comprises mixing functional additives and hot pressing and drying, and wherein the microencapsulation is mainly prepared by chitosan loading.

[0005] As a further solution of the present invention: the natural cellulose raw material pretreatment is to select wood pulp, bamboo pulp and cotton fiber as natural cellulose raw materials, put 1000g of wood pulp into a large stirring and cleaning tank, add 10L of deionized water, turn on the stirring device, stir at a speed of 200r / min for 30min-40min, remove surface impurities and then transfer to a filtration device, filter to remove the washed sewage, repeat the cleaning and filtration 3 times, after completion, place the washed wood pulp in an alkali treatment container, add 5L of 3% sodium hydroxide solution by mass, and The reaction was stirred at a temperature of 60°C for 2 hours, and the stirring speed was controlled at 150 r / min. After the reaction was completed, the reaction solution was filtered using a filter device, and the wood pulp was rinsed with deionized water. The deionized water after rinsing was tested, and the rinsing was stopped when the pH value of the deionized water was between 6.5 and 7.5. The pretreatment method of bamboo pulp and cotton fiber was the same as that of wood pulp fiber. When treating bamboo pulp, the alkali treatment concentration needed to be set to 4%, and the reaction time was 1.5 hours. When treating cotton fiber, the alkali treatment concentration needed to be set to 2.5%, and the reaction time was 2.5 hours.

[0006] As a further solution of the present invention: the specific steps for preparing the nanocellulose suspension are as follows:

[0007] 100g of pretreated wood pulp was added to a special enzymatic hydrolysis reactor, and 1.5g of a buffer solution of characteristic cellulase was added thereto. The reactor temperature was set to 52°C, and the reaction was stirred at a speed of 100r / min for 14h. After the reaction was completed, the reaction liquid was transferred to a high-speed centrifuge and centrifuged at a speed of 10000r / min for 20min-30min to remove the unreacted residue. The supernatant was taken out and passed through a 0.22um microporous filter membrane to obtain a nanocellulose suspension.

[0008] As a further solution of the present invention: the specific operation of adding tea polyphenols is as follows:

[0009] Weigh 50 g of 98% pure tea polyphenol crystals, dissolve them in 500 mL of anhydrous ethanol, and ultrasonically treat for 15 minutes at an ultrasonic power of 200 W to obtain a uniform tea polyphenol ethanol solution for later use. Add 50 mL of the prepared tea polyphenol ethanol solution to 500 mL of the prepared nanocellulose suspension, and add 0.3 g of initiator ammonium persulfate at the same time. Transfer the mixed solution to a reaction flask with a condenser reflux device, and stir the reaction at a speed of 120 r / min in an oil bath at a temperature of 60°C for 4 hours. During the reaction, after the reaction is completed, use a rotary evaporator to distill under reduced pressure at 40°C to remove most of the anhydrous ethanol solvent, and then dialyze the remaining solution with deionized water. The dialysis bag has a molecular weight cutoff of 3 kDa. Dialysis is performed for 24 hours to remove unreacted tea polyphenols and impurities to obtain a nanocellulose suspension loaded with tea polyphenols.

[0010] As a further solution of the present invention: the antibacterial agent is loaded by an in-situ polymerization method, the prepared nanocellulose suspension is added to the prepared chitosan acetic acid solution, and 0.5 g of initiator ammonium persulfate is added at the same time. After mixing, it is transferred to a polymerization reaction bottle with a condensation reflux device, and stirred at a speed of 150 r / min in an oil bath at a temperature of 65°C for 5 hours. After the reaction is completed, a rotary evaporator is used to perform reduced pressure distillation at 40°C to remove acetic acid and ethanol solvents. The remaining solution is dialyzed with deionized water, and the dialysis bag has a molecular weight cutoff of 5 kDa. After 24 hours of dialysis to remove the reacted monomers and impurities, a nanocellulose suspension loaded with chitosan is obtained, which is mixed with a nanocellulose suspension loaded with tea polyphenols to obtain a mixed nanocellulose suspension.

[0011] As a further solution of the present invention: the functional additive mixing includes the addition of a plasticizer and the addition of a reinforcing agent. The specific operation of adding the plasticizer is to select a magnetic stirrer with a power of 100W, equipped with a polytetrafluoroethylene magnetic stirrer with a diameter of 30mm, prepare a 500mL glass beaker, transfer the mixed nanocellulose suspension to the glass beaker, and pour 500mL of the prepared mixed nanocellulose suspension loaded with an antibacterial agent into the prepared glass beaker. During the operation, a glass funnel is used to assist the transfer, 20g of natural glycerol is weighed and slowly poured into a 100mL glass measuring cylinder, and the glass beaker containing the suspension is placed on the magnetic stirrer. The magnetic stirrer is turned on and the speed is set to 80r / min. After the stirrer rotates stably, the glycerol in the measuring cylinder is slowly poured into the suspension along the wall of the beaker. After the addition is completed, stirring is continued for 30min to fully mix the glycerol and the mixed nanocellulose suspension. During the stirring process, the bottom and wall of the beaker are gently stirred with a glass rod every 5min to prevent glycerol aggregation.

[0012] As a further solution of the present invention: the specific operation of adding and mixing the enhancer is to weigh 15g of lignin, select a high-speed grinder to preliminarily grind the lignin, put the lignin into the hopper of the grinder, set the grinding time to 3min, and the grinding speed to 10000r / min. After the grinding is completed, the lignin powder is transferred to a sealed plastic container, and a vibrating screening machine equipped with a 200-mesh screen is used to screen the crushed lignin powder. The lignin powder is slowly poured into the feed port of the vibrating screening machine, the screening machine is started, the vibration frequency is set to 50Hz, and the screening time is 20000r / min. The mixture was stirred for 10 minutes, and large particles of lignin were sieved to remove them. The lignin powder under the sieve was collected in a clean sealed bag for later use. After the plasticizer was added and stirred, the magnetic stirrer was kept running at a speed of 100 r / min. A small hole was cut in the sealed bag containing the lignin powder, and the lignin powder was slowly added to the mixed nanocellulose suspension containing glycerol using a small spoon. The addition process should be slow and uniform. After the addition is completed, stirring was continued for 1 hour. During the stirring process, a glass rod was used to penetrate into the bottom of the suspension and gently stir it every 15 minutes to obtain a uniformly mixed composite suspension.

[0013] As a further solution of the present invention: the specific operation of the hot pressing forming and drying is as follows:

[0014] A precision hot press was selected, with a heating plate size of 300mm×300mm, a temperature control accuracy of ±1°C, a pressure adjustment range of 0MPa-50MPa, and a mold internal size of 200mm×200mm×5mm. The mold surface was polished, and the mold was placed in an oven and baked at 120°C for 2h to remove moisture and impurities that may be adsorbed on the mold surface. The suspension after adding plasticizer and enhancer and stirring was transferred to a vacuum degassing device, the vacuum degree was set to -0.09MPa, and the degassing time was 15min.

[0015] As a further solution of the present invention: after the vacuum degassing is completed, the degassed composite suspension is slowly poured into a mold preheated to 60°C, and the pouring amount is up to 80% of the mold volume. The mold containing the suspension is quickly placed between the heating plates of a hot press, the hot press is closed, the hot pressing temperature is set to 150°C, the pressure is set to 10 MPa, and the holding time is 30 minutes. During the heating process, the temperature is slowly increased at a rate of 5°C / min. After the hot pressing is completed, the hot press pressure is maintained unchanged, the cooling system is turned on, and the mold is cooled to room temperature at a rate of 3°C / min. After the cooling is completed, the hot press pressure is slowly released, the mold is removed, and a demolding tool is used to remove the formed nano-cellulose composite raw material from the mold to obtain a nano-cellulose composite raw material.

[0016] By adopting the above technical solution, compared with the prior art, the beneficial effects of the present invention are:

[0017] 1. The present invention is formed by hot pressing. During the hot pressing process, the nanocellulose molecular chains are rearranged and intertwined under the action of temperature and pressure. At the same time, reinforcing agents such as lignin are further fused with the nanocellulose, and the glycerol plasticizer plays a role, making the material have better flexibility and plasticity, and finally forming a dense block composite raw material. By loading tea polyphenols and chitosan on the nanocellulose and microencapsulating and loading plant essential oils, the composite raw material is endowed with strong antibacterial ability. Taking tea polyphenols as an example, it has dual antioxidant and antibacterial effects. Under the action of an initiator, it is tightly bound to the surface of the nanocellulose through in situ polymerization. The formed complex can effectively inhibit the growth of microorganisms.

[0018] 2. The present invention adds antibacterial substances such as tea polyphenols and chitosan acetic acid solution, and its inhibition rate on common bacteria such as Escherichia coli and Staphylococcus aureus reaches more than 90%. This makes the composite raw material have reliable application value in fields such as food packaging and medical health that have extremely high requirements for antibacterial performance, can significantly extend the shelf life of food, ensure food quality and safety, and can be used in the medical field to manufacture antibacterial dressings, surgical sutures, etc., reduce the risk of infection, and improve the performance and safety of medical products. Moreover, the antibacterial substances are all natural antibacterial agents, which meet the requirements of green environmental protection and health and safety. Compared with traditional chemical synthetic antibacterial agents, they reduce environmental pollution and potential harm to the human body. Green chemical methods and natural raw materials are used in the entire preparation process, which reduces environmental pollution. Compared with traditional chemical methods, the enzymatic hydrolysis and dilute acid hydrolysis methods for preparing nanocellulose reduce energy consumption and the use of chemical reagents. The use of natural antibacterial agents and functional additives meets environmental protection and health requirements. In addition, the nanocellulose itself is degradable, so that the composite raw material can be naturally decomposed after use and will not cause long-term environmental burden.

[0019] 3. The nanocellulose composite raw material prepared by the present invention combines the excellent properties of nanocellulose and the antibacterial properties of antibacterial agents, broadening its application range. In the field of food packaging, it can extend the shelf life of food, reduce food waste, and increase the added value of food. In the field of medical and health care, it can be used to manufacture antibacterial dressings, surgical sutures, etc., to improve the performance and safety of medical products and create higher economic value. At the same time, due to its green and environmentally friendly characteristics, it meets the market demand for sustainable products and enhances the competitiveness of products in the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart for preparing the antibacterial nanocellulose composite raw material in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention.

[0022] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Please see the attached Figure 1 The present invention provides a method for preparing a nano-cellulose composite raw material containing an antimicrobial agent, including the preparation of the nano-cellulose composite raw material. The method for preparing the nano-cellulose composite raw material containing an antimicrobial agent includes raw material preparation, antimicrobial agent loading and composite molding. The raw materials include natural fiber raw materials, tea polyphenols, chitosan acetic acid solution, nano-cellulose suspension and plant essential oil. The natural cellulose raw materials include wood pulp, bamboo pulp and cotton fiber. The antimicrobial agent is loaded by in-situ polymerization. The composite molding includes mixing functional additives and hot pressing and drying. The microencapsulation is mainly prepared by chitosan loading.

[0024] In one embodiment of the present invention: the natural cellulose raw material is pretreated by selecting wood pulp, bamboo pulp and cotton fiber as natural cellulose raw materials, putting 1000g of wood pulp into a large stirring and cleaning tank, adding 10L of deionized water, turning on the stirring device, stirring at a speed of 200r / min for 30min-40min, removing surface impurities and transferring it to a filtering device, filtering to remove the cleaned sewage, repeating the cleaning and filtration 3 times, and after completion, placing the cleaned wood pulp in an alkali treatment container, adding 5L of sodium hydroxide solution with a mass fraction of 3%, stirring and reacting at a temperature of 60°C for 2h, and controlling the stirring speed at 150r / min. After the reaction is completed, the reaction solution is filtered using a filtering device, and the wood pulp is rinsed with deionized water. The deionized water after rinsing is tested, and the rinsing is stopped when the pH value of the deionized water is between 6.5-7.5. The pretreatment method of bamboo pulp and cotton fiber is the same as that of wood pulp fiber. When treating bamboo pulp, the alkali treatment concentration needs to be set to 4% and the reaction time is 1.5h. When treating cotton fiber, the alkali treatment concentration needs to be set to 2.5% and the reaction time is 2.5h.

[0025] In one embodiment of the present invention, the specific steps for preparing the nanocellulose suspension are as follows:

[0026] 100g of pretreated wood pulp was added to a special enzymatic hydrolysis reactor, and 1.5g of a buffer solution of characteristic cellulase was added thereto. The reactor temperature was set to 52°C, and the reaction was stirred at a speed of 100r / min for 14h. After the reaction was completed, the reaction liquid was transferred to a high-speed centrifuge and centrifuged at a speed of 10000r / min for 20min-30min to remove the unreacted residue. The supernatant was taken out and passed through a 0.22um microporous filter membrane to obtain a nanocellulose suspension.

[0027] In one embodiment of the present invention, the specific operation of adding tea polyphenols is as follows:

[0028] Weigh 50 g of 98% pure tea polyphenol crystals, dissolve them in 500 mL of anhydrous ethanol, and ultrasonically treat for 15 minutes at an ultrasonic power of 200 W to obtain a uniform tea polyphenol ethanol solution for later use. Add 50 mL of the prepared tea polyphenol ethanol solution to 500 mL of the prepared nanocellulose suspension, and add 0.3 g of initiator ammonium persulfate at the same time. Transfer the mixed solution to a reaction flask with a condenser reflux device, and stir the reaction at a speed of 120 r / min in an oil bath at a temperature of 60°C for 4 hours. During the reaction, after the reaction is completed, use a rotary evaporator to distill under reduced pressure at 40°C to remove most of the anhydrous ethanol solvent, and then dialyze the remaining solution with deionized water. The dialysis bag has a molecular weight cutoff of 3 kDa. Dialysis is performed for 24 hours to remove unreacted tea polyphenols and impurities to obtain a nanocellulose suspension loaded with tea polyphenols.

[0029] In one embodiment of the present invention: the antibacterial agent is loaded by an in-situ polymerization method, and the prepared nanocellulose suspension is added to the prepared chitosan acetic acid solution, and 0.5 g of initiator ammonium persulfate is added at the same time. After mixing, it is transferred to a polymerization reaction bottle with a condensation reflux device, and the reaction is stirred at a speed of 150 r / min in an oil bath at a temperature of 65°C for 5 hours. After the reaction is completed, a rotary evaporator is used to perform reduced pressure distillation at 40°C to remove acetic acid and ethanol solvents. The remaining solution is dialyzed with deionized water, and the dialysis bag has a molecular weight cutoff of 5 kDa. After 24 hours of dialysis to remove the reacted monomers and impurities, a nanocellulose suspension loaded with chitosan is obtained, which is mixed with a nanocellulose suspension loaded with tea polyphenols to obtain a mixed nanocellulose suspension.

[0030] In one embodiment of the present invention: the mixing of functional additives includes the addition of plasticizers and the addition of reinforcing agents. The specific operation of adding the plasticizer is to select a magnetic stirrer with a power of 100W, equipped with a polytetrafluoroethylene magnetic stirrer with a diameter of 30mm, prepare a 500mL glass beaker, transfer the mixed nanocellulose suspension to the glass beaker, and pour 500mL of the prepared mixed nanocellulose suspension loaded with an antibacterial agent into the prepared glass beaker. During the operation, a glass funnel is used to assist the transfer, 20g of natural glycerol is weighed and slowly poured into a 100mL glass measuring cylinder, and the glass beaker containing the suspension is placed on the magnetic stirrer. The magnetic stirrer is turned on and the speed is set to 80r / min. After the stirrer rotates stably, the glycerol in the measuring cylinder is slowly poured into the suspension along the wall of the beaker. After the addition is completed, stirring is continued for 30min to fully mix the glycerol and the mixed nanocellulose suspension. During the stirring process, the bottom and wall of the beaker are gently stirred with a glass rod every 5min to prevent glycerol aggregation.

[0031] In one embodiment of the present invention, the specific operation of adding and mixing the enhancer is to weigh 15g of lignin, select a high-speed grinder to perform preliminary crushing on the lignin, put the lignin into the hopper of the grinder, set the crushing time to 3min, and the crushing speed to 10000r / min. After the crushing is completed, the lignin powder is transferred to a sealed plastic container, and a vibrating screening machine equipped with a 200-mesh screen is used to screen the crushed lignin powder. The lignin powder is slowly poured into the feed port of the vibrating screening machine, the screening machine is started, the vibration frequency is set to 50Hz, and the screening time is 10min, sieve to remove large particles of lignin, collect the sieved lignin powder in a clean sealed bag for later use, after the plasticizer is added and stirred, keep the magnetic stirrer running at a speed of 100r / min, cut a small hole in the sealed bag containing the lignin powder, and use a small spoon to slowly add the lignin powder to the mixed nanocellulose suspension containing glycerol. The addition process should be slow and even. After the addition is completed, continue stirring for 1h. During the stirring process, use a glass rod to go deep into the bottom of the suspension and stir gently every 15min to obtain a uniformly mixed composite suspension.

[0032] In one embodiment of the present invention, the specific operation of hot pressing and drying is as follows:

[0033] A precision hot press was selected, with a heating plate size of 300mm×300mm, a temperature control accuracy of ±1°C, a pressure adjustment range of 0MPa-50MPa, and a mold internal size of 200mm×200mm×5mm. The mold surface was polished, and the mold was placed in an oven and baked at 120°C for 2h to remove moisture and impurities that may be adsorbed on the mold surface. The suspension after adding plasticizer and enhancer and stirring was transferred to a vacuum degassing device, the vacuum degree was set to -0.09MPa, and the degassing time was 15min.

[0034] In one embodiment of the present invention: after vacuum degassing is completed, the degassed composite suspension is slowly poured into a mold preheated to 60°C, and the pouring amount is up to 80% of the mold volume. The mold containing the suspension is quickly placed between the heating plates of a hot press, the hot press is closed, and the hot pressing temperature is set to 150°C, the pressure is 10 MPa, and the holding time is 30 minutes. During the heating process, the temperature is slowly increased at a rate of 5°C / min. After the hot pressing is completed, the hot press pressure is kept unchanged, the cooling system is turned on, and the mold is cooled to room temperature at a rate of 3°C / min. After the cooling is completed, the hot press pressure is slowly released, the mold is removed, and a demolding tool is used to remove the formed nano-cellulose composite raw material from the mold to obtain a nano-cellulose composite raw material.

[0035] For example, please see the attached Figure 1 ;

[0036] 1000g of wood pulp was selected and put into a large stirring and cleaning tank, 10L of deionized water was added, the stirring device was turned on and stirred at a speed of 200r / min for 35min. After the surface impurities were removed, the wood pulp was transferred to the filtration device for filtration to remove the sewage, and the cleaning and filtration were repeated 3 times. Then, the cleaned wood pulp was placed in an alkali treatment container, 5L of a 3% sodium hydroxide solution was added, and the mixture was reacted at a temperature of 60°C and a stirring speed of 150r / min for 2h. After the reaction was completed, the wood pulp was filtered with a filtration device and rinsed with deionized water until the pH value of the deionized water after rinsing was between 6.5-7.5. The rinsing was stopped, and 100g of the pretreated wood pulp was added to a special enzymatic hydrolysis reactor, to which 1.5g of a buffer solution of a characteristic cellulase was added. The reaction kettle temperature was set to 52 ° C, and the reaction was stirred at a speed of 100 r / min for 14 hours. After the reaction was completed, the reaction solution was transferred to a high-speed centrifuge and centrifuged at a speed of 10000 r / min for 25 minutes to remove the unreacted residue. The supernatant was taken and passed through a 0.22 μm microporous filter membrane to obtain a nanocellulose suspension. 50 g of tea polyphenol crystals with a purity of 98% were weighed and dissolved in 500 mL of anhydrous ethanol. After ultrasonic treatment for 15 minutes (ultrasonic power 200 W), a uniform tea polyphenol ethanol solution was prepared for standby use. A certain amount of chitosan was weighed (the specific amount was determined according to actual needs and subsequent reactions) and dissolved in a 2% by mass acetic acid solution to prepare a chitosan acetic acid solution.

[0037] In 500mL of the prepared nanocellulose suspension, 50mL of the prepared tea polyphenol ethanol solution was added, and 0.3g of the initiator ammonium persulfate was added at the same time. The mixed solution was transferred to a reaction bottle with a condensation reflux device, and stirred at a speed of 120r / min in an oil bath at a temperature of 60°C for 4h. After the reaction, most of the anhydrous ethanol solvent was removed by reduced pressure distillation at 40°C using a rotary evaporator, and the remaining solution was dialyzed with deionized water (the molecular weight cutoff of the dialysis bag was 3kDa) for 24h to remove unreacted tea polyphenols and impurities to obtain a nanocellulose suspension loaded with tea polyphenols. The prepared nanocellulose suspension was added to the prepared The chitosan acetic acid solution was prepared, and 0.5 g of ammonium persulfate as an initiator was added at the same time. After mixing, the mixture was transferred to a polymerization reaction bottle with a condensation reflux device, and the reaction was stirred at a speed of 150 r / min in an oil bath at a temperature of 65°C for 5 hours. After the reaction was completed, the acetic acid and ethanol solvents were removed by vacuum distillation using a rotary evaporator at 40°C. The remaining solution was dialyzed with deionized water (the dialysis bag had a molecular weight cut-off of 5 kDa) for 24 hours to remove the reacted monomers and impurities, thereby obtaining a nanocellulose suspension loaded with chitosan. The nanocellulose suspension loaded with tea polyphenols was mixed with the nanocellulose suspension loaded with chitosan to obtain a mixed nanocellulose suspension.

[0038] A 100W magnetic stirrer was selected, equipped with a 30mm diameter polytetrafluoroethylene magnetic stirrer, a 500mL glass beaker was prepared, and the mixed nanocellulose suspension was transferred to the glass beaker. A glass funnel was used to assist the transfer during the operation. 20g of natural glycerol was weighed and slowly poured into a 100mL glass measuring cylinder. The glass beaker containing the suspension was placed on the magnetic stirrer, the magnetic stirrer was turned on and the speed was set to 80r / min. After the stirrer rotated stably, the glycerol in the measuring cylinder was slowly poured into the suspension along the wall of the beaker. After the addition was completed, stirring was continued for 30 minutes. During this period, the bottom and wall of the beaker were gently stirred with a glass rod every 5 minutes to prevent glycerol from agglomerating, so that the glycerol and the mixed nanocellulose suspension were fully mixed. 15g of lignin was weighed and preliminarily crushed with a high-speed crusher. The lignin was placed in the crusher hopper and the crushing time was set to 3 minutes. The speed is 10000r / min. After the crushing is completed, the lignin powder is transferred to a sealed plastic container and sieved using a vibrating screening machine (equipped with a 200 mesh screen). The lignin powder is slowly poured into the feed port of the vibrating screening machine, the screening machine is started, the vibration frequency is set to 50Hz, the sieving time is 10min, and large particles of lignin are removed by sieving. The lignin fine powder under the sieve is collected in a clean sealed bag for standby use. After the plasticizer is added and stirred, the magnetic stirrer is kept running at a speed of 100r / min. A small opening is cut in the sealed bag containing the lignin fine powder. The lignin powder is slowly added to the mixed nanocellulose suspension containing glycerol with a small spoon. The addition process should be slow and uniform. After the addition is completed, stirring is continued for 1h. During the stirring process, a glass rod is used to go deep into the bottom of the suspension and gently stir every 15min to obtain a mixed composite suspension.

[0039] A precision hot press is selected, the size of its heating plate is 300mm×300mm, the temperature control accuracy can reach ±1℃, the pressure adjustment range is 0MPa-50MPa, the internal size of the supporting mold is 200mm×200mm×5mm, the mold surface is polished, the mold is placed in an oven, and baked at 120℃ for 2h to remove moisture and impurities that may be adsorbed on the mold surface. The suspension after adding plasticizer and enhancer and stirring is transferred to a vacuum degassing device, the vacuum degree is set to -0.09MPa, the degassing time is 15min, and after the vacuum degassing is completed, the degassed composite suspension is slowly poured into the oven. Pour the suspension into a mold preheated to 60°C, pour it into 80% of the mold volume, quickly place the mold containing the suspension between the heating plates of the hot press, turn off the hot press, set the hot pressing temperature to 150°C, the pressure to 10 MPa, and the holding time to 30 minutes. During the heating process, slowly increase the temperature at a rate of 5°C / min. After the hot pressing is completed, keep the hot press pressure unchanged, turn on the cooling system, and cool the mold to room temperature at a rate of 3°C / min. After the cooling is completed, slowly release the hot press pressure, take out the mold, and use a demoulding tool to remove the formed nanocellulose composite raw material from the mold to obtain a nanocellulose composite raw material.

[0040] Nanocellulose composite raw materials can be used in food packaging, medical care, textiles, agriculture, construction and other fields due to their antibacterial and biocompatible properties.

[0041] Although the present invention is disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modifications, equivalent variations, and modifications made to the above embodiments in accordance with the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a nanocellulose composite material containing an antimicrobial agent, comprising preparing the nanocellulose composite material, characterized in that: The method for preparing a nanocellulose composite raw material containing an antimicrobial agent includes raw material preparation, antimicrobial agent loading, and composite molding. The raw materials include natural fiber raw materials, tea polyphenols, chitosan acetic acid solution, nanocellulose suspension, and plant essential oils. The natural cellulose raw materials include wood pulp, bamboo pulp, and cotton fiber. The antimicrobial agent is loaded by in-situ polymerization. The composite molding includes mixing functional additives and hot pressing and drying. The microencapsulation is mainly prepared by chitosan loading.

2. The method for preparing a nanocellulose composite material containing an antibacterial agent according to claim 1, wherein: The natural cellulose raw material pretreatment is to select wood pulp, bamboo pulp and cotton fiber as natural cellulose raw materials, put 1000g of wood pulp into a large stirring and cleaning tank, add 10L of deionized water, turn on the stirring device, stir at a speed of 200r / min for 30min-40min, remove surface impurities and transfer to a filtering device, filter to remove the cleaned sewage, repeat the cleaning and filtration 3 times, after completion, place the cleaned wood pulp in an alkali treatment container, add 5L of sodium hydroxide solution with a mass fraction of 3%, stir and react at a temperature of 60°C for 2h, and control the stirring speed at 150r / min. After the reaction is completed, use a filtering device to filter the reaction solution, and rinse the wood pulp with deionized water, detect the deionized water after rinsing, and stop rinsing when the pH value of the deionized water is between 6.5-7.

5. The pretreatment method of bamboo pulp and cotton fiber is the same as that of wood pulp fiber. When treating bamboo pulp, the alkali treatment concentration needs to be set to 4% and the reaction time is 1.5h. When treating cotton fiber, the alkali treatment concentration needs to be set to 2.5% and the reaction time is 2.5h.

3. The method for preparing a nanocellulose composite material containing an antibacterial agent according to claim 1, wherein: The specific steps for preparing the nanocellulose suspension are as follows: 100g of pretreated wood pulp was added to a special enzymatic hydrolysis reactor, and 1.5g of a buffer solution of characteristic cellulase was added thereto. The reactor temperature was set to 52°C, and the reaction was stirred at a speed of 100r / min for 14h. After the reaction was completed, the reaction liquid was transferred to a high-speed centrifuge and centrifuged at a speed of 10000r / min for 20min-30min to remove the unreacted residue. The supernatant was taken out and passed through a 0.22um microporous filter membrane to obtain a nanocellulose suspension.

4. The method for preparing a nanocellulose composite material containing an antimicrobial agent according to claim 1, wherein: The specific operation of adding tea polyphenols is as follows: Weigh 50 g of 98% pure tea polyphenol crystals, dissolve them in 500 mL of anhydrous ethanol, and ultrasonically treat for 15 minutes at an ultrasonic power of 200 W to obtain a uniform tea polyphenol ethanol solution for later use. Add 50 mL of the prepared tea polyphenol ethanol solution to 500 mL of the prepared nanocellulose suspension, and add 0.3 g of initiator ammonium persulfate at the same time. Transfer the mixed solution to a reaction flask with a condenser reflux device, and stir the reaction at a speed of 120 r / min in an oil bath at a temperature of 60°C for 4 hours. During the reaction, after the reaction is completed, use a rotary evaporator to distill under reduced pressure at 40°C to remove most of the anhydrous ethanol solvent, and then dialyze the remaining solution with deionized water. The dialysis bag has a molecular weight cutoff of 3 kDa. Dialysis is performed for 24 hours to remove unreacted tea polyphenols and impurities to obtain a nanocellulose suspension loaded with tea polyphenols.

5. The method for preparing a nanocellulose composite material containing an antimicrobial agent according to claim 1, wherein: The antimicrobial agent loading is carried out by an in-situ polymerization method, wherein the prepared nanocellulose suspension is added to the prepared chitosan acetic acid solution, and 0.5 g of initiator ammonium persulfate is added at the same time. After mixing, the suspension is transferred to a polymerization reaction bottle equipped with a condensation reflux device, and stirred at a speed of 150 r / min in an oil bath at a temperature of 65° C. for 5 hours. After the reaction is completed, a rotary evaporator is used to perform reduced pressure distillation at 40° C. to remove acetic acid and ethanol solvents, and the remaining solution is dialyzed with deionized water with a dialysis bag having a molecular weight cutoff of 5 kDa. After dialyzing for 24 hours to remove the reacted monomers and impurities, a nanocellulose suspension loaded with chitosan is obtained, which is mixed with a nanocellulose suspension loaded with tea polyphenols to obtain a mixed nanocellulose suspension.

6. The method for preparing a nanocellulose composite material containing an antimicrobial agent according to claim 1, wherein: The functional additive mixing includes the addition of plasticizers and reinforcing agents. The specific operation of adding the plasticizer is to select a magnetic stirrer with a power of 100W, equipped with a polytetrafluoroethylene magnetic stirrer with a diameter of 30mm, prepare a 500mL glass beaker, transfer the mixed nanocellulose suspension to the glass beaker, and pour 500mL of the prepared mixed nanocellulose suspension loaded with an antibacterial agent into the prepared glass beaker. During the operation, a glass funnel is used to assist the transfer, 20g of natural glycerol is weighed and slowly poured into a 100mL glass measuring cylinder, and the glass beaker containing the suspension is placed on the magnetic stirrer. The magnetic stirrer is turned on and the speed is set to 80r / min. After the stirrer rotates stably, the glycerol in the measuring cylinder is slowly poured into the suspension along the wall of the beaker. After the addition is completed, stirring is continued for 30min to fully mix the glycerol and the mixed nanocellulose suspension. During the stirring process, the bottom and wall of the beaker are gently stirred with a glass rod every 5min to prevent glycerol aggregation.

7. The method for preparing a nanocellulose composite material containing an antimicrobial agent according to claim 1, wherein: The specific operation of adding and mixing the enhancer is to weigh 15g of lignin, use a high-speed grinder to preliminarily grind the lignin, put the lignin into the hopper of the grinder, set the grinding time to 3 minutes, and the grinding speed to 10000r / min. After the grinding is completed, the lignin powder is transferred to a sealed plastic container, and a vibration screening machine equipped with a 200-mesh screen is used to screen the crushed lignin powder. The lignin powder is slowly poured into the feed port of the vibration screening machine, the screening machine is started, the vibration frequency is set to 50Hz, and the screening time is 10 minutes. , sieve to remove large particles of lignin, collect the sieved lignin fine powder in a clean sealed bag for later use, after the plasticizer is added and stirred, keep the magnetic stirrer running at a speed of 100r / min, cut a small hole in the sealed bag containing the lignin fine powder, use a small spoon to slowly add the lignin powder to the mixed nanocellulose suspension containing glycerol, the addition process should be slow and even, after the addition is completed, continue stirring for 1h, during the stirring process, use a glass rod to go deep into the bottom of the suspension and stir gently every 15min to obtain a mixed composite suspension.

8. The method for preparing a nanocellulose composite material containing an antimicrobial agent according to claim 1, wherein: The specific operation of the hot pressing forming and drying is as follows: A precision hot press was selected, with a heating plate size of 300mm×300mm, a temperature control accuracy of ±1°C, a pressure adjustment range of 0MPa-50MPa, and a mold internal size of 200mm×200mm×5mm. The mold surface was polished, and the mold was placed in an oven and baked at 120°C for 2h to remove moisture and impurities that may be adsorbed on the mold surface. The suspension after adding plasticizer and enhancer and stirring was transferred to a vacuum degassing device, the vacuum degree was set to -0.09MPa, and the degassing time was 15min.

9. The method for preparing a nanocellulose composite material containing an antimicrobial agent according to claim 1, wherein: After the vacuum degassing is completed, the degassed composite suspension is slowly poured into a mold preheated to 60° C., and the pouring amount is up to 80% of the mold volume. The mold containing the suspension is quickly placed between the heating plates of a hot press, the hot press is closed, the hot pressing temperature is set to 150° C., the pressure is set to 10 MPa, and the holding time is 30 minutes. During the heating process, the temperature is slowly increased at a rate of 5° C. / min. After the hot pressing is completed, the hot press pressure is maintained unchanged, the cooling system is turned on, and the mold is cooled to room temperature at a rate of 3° C. / min. After the cooling is completed, the hot press pressure is slowly released, the mold is removed, and a demolding tool is used to remove the formed nano-cellulose composite raw material from the mold to obtain a nano-cellulose composite raw material.

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