Easily-processed high-strength bamboo stick and preparation method thereof

Abstract

The invention relates to the technical field of bamboo sticks, in particular to a high-strength bamboo stick easy to process and a preparation method thereof. The preparation method of the high-strength bamboo stick easy to process comprises the steps of preparation of the modified nanocellulose, preparation of a bamboo stick rough blank and preparation of the bamboo stick. The water-based phenolic resin prepolymer, the nano silicon dioxide and the modified nano cellulose are used as reinforcing modifiers and permeate into the bamboo wood through vacuum pressurization, a synergistic reinforcing structure is formed after thermocuring, the bending strength is improved, the moisture and mildewing phenomena are reduced, the modified nano cellulose is good in hydrophobicity and uniform in dispersion, the toughness can be improved through a flexible interface layer of the modified nano cellulose, and the service life of the bamboo wood is prolonged. And the bamboo canes are subjected to freeze thawing to construct pores and then are subjected to impurity removal by using the composite bio-enzyme, so that the modifier can be assisted to permeate and reinforce the combination, and a'medium temperature-high temperature-medium temperature 'gradient drying is adopted, so that the moisture is controlled, the cracking deformation is prevented, and the yield is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bamboo stick preparation, in particular to an easy-to-process high-strength bamboo stick and a preparation method thereof. BACKGROUND

[0002] As a strip-shaped product made of natural bamboo strips, bamboo sticks occupy a core position in the incense production field due to their advantages of wide source, low cost, and good biocompatibility. They are the core supporting framework of various types of incense sticks and stick incense. The performance of bamboo sticks for incense directly determines the quality and use experience of finished incense products. In the production of incense, bamboo sticks need to be pretreated before being compounded with raw materials such as incense powder and adhesives. During the transportation, storage, and burning of finished incense products, bamboo sticks need to provide continuous structural support to prevent the incense body from breaking and falling apart. At the same time, some incense burns for several hours, and bamboo sticks also need to have certain high-temperature stability to prevent deformation or brittle fracture at high temperatures.

[0003] The structural defects of natural bamboo strips result in insufficient strength and poor stability. The anisotropy of bamboo strip fibers and the density difference between bamboo joints, green bamboo, and yellow bamboo make the mechanical properties of bamboo sticks uneven. Local high temperatures during incense burning can exacerbate the decline in fiber bonding, leading to brittle fracture of bamboo sticks when the incense body burns to the middle, causing the incense body to fall off. At the same time, natural bamboo strips are prone to develop microcracks after drying due to water loss. These cracks can quickly expand when the incense body is under the weight of the incense body or impacted, leading to the breaking of the bamboo stick and the high breakage rate of the finished incense product. Moreover, the storage environment of incense is often humid in temples and ancestral halls. The existing bamboo sticks are prone to mold due to the absorption of moisture in the air, which not only affects the appearance but also leads to a decrease in strength. These problems not only increase the raw material loss and production cost of incense production enterprises but also affect the use experience of consumers. Therefore, we propose an easy-to-process high-strength bamboo stick and a preparation method thereof to solve the above problems. SUMMARY

[0004] In view of the deficiencies in the prior art, the purpose of the present application is to provide an easy-to-process high-strength bamboo stick and a preparation method thereof.

[0005] The present application provides a preparation method of an easy-to-process high-strength bamboo stick, comprising: S1: preparation of modified nanocellulose; TEMPO-oxidized nanocellulose is added to HAc-NaAc buffer solution, followed by the addition of sodium periodate and deionized water, shaking reaction, then adding ethylene glycol and standing, and then dialysis to neutral, rotary evaporation, to obtain 1-2wt% T-DANF suspension, then reacting with n-hexylamine, then adding sodium borohydride for further reaction, dialysis, rotary evaporation, and freeze-drying to obtain modified nanocellulose; S2: preparation of bamboo stick rough blank; Select 3-5 year old moso bamboo to make bamboo strips, clean, polish and dry them, vacuum soak and freeze-thaw treatment, then soak them in a compound biological enzyme solution, ultrasonically clean the soaked bamboo strips with deionized water, then cut, grind and round them, dry them to make bamboo sticks with uniform diameter. S3: Preparation of bamboo skewers; Mix 100-120 parts by weight of waterborne phenolic resin prepolymer with 10-15 parts by weight of nano-silica and 8-10 parts by weight of modified nanocellulose to prepare a reinforcing modifier. Vacuum impregnate the bamboo skewer blank with the reinforcing modifier and pressurize it. After removal, heat cure it and polish it to obtain the finished bamboo skewer.

[0006] As a preferred aspect, S1: the preparation of modified nanocellulose specifically includes the following steps: S1.1: Add 1-2 parts by weight of TEMPO oxidized nanocellulose to 25-30 parts by weight of HAc-NaAc buffer solution with pH 3.5, then add sodium periodate, with a molar ratio of sodium periodate to TEMPO oxidized nanocellulose of 6:1, then add 180-200 parts by weight of deionized water, and then react with shaking at 45-50℃ under light-protected conditions for 48-50 h. After the reaction is completed, add 20-22 parts by weight of ethylene glycol, let stand for 10-12 min, then dialyze to neutral using a dialysis bag, and finally rotary evaporate to prepare a 1-2 wt% T-DANF suspension. S1.2: Add n-hexylamine to 8-10 parts by weight of 1-2 wt% T-DANF suspension at a ratio of aldehyde to amino of 1:1, stir and react in a water bath at 30-40℃ for 6-8 h. After the reaction is complete, add 1-2 parts by weight of sodium borohydride, continue stirring and react for 3-5 h. After the reaction is complete, dialyze to neutral, then rotary evaporate and freeze dry to obtain modified nanocellulose.

[0007] As a preferred aspect, S2: the preparation of the bamboo skewer blanks specifically includes the following steps: S2.1: Select bamboo that is 3-5 years old, with uniform wall thickness, no mold, and no cracks. Split the bamboo tube into strips, remove the inner and outer nodes, and sand it with sandpaper for 10-15 minutes. After cleaning the bamboo strips with deionized water, completely immerse the bamboo strips in deionized water and soak them under a vacuum of 0.08MPa for 30-40 minutes. Drain the surface water and freeze-thaw the soaked bamboo strips to obtain freeze-thawed bamboo strips. S2.2: Immerse the freeze-thawed bamboo strips in a compound bio-enzyme solution, and then soak them at 50-55℃ and pH 5.0-5.5 for 8-10 hours to obtain pretreated bamboo strips; S2.3: The pre-treated bamboo strips are ultrasonically cleaned with deionized water at 60-70℃ for 15-20 minutes, then shaved and rounded, and dried using a gradient drying method of "medium temperature-high temperature-medium temperature" to produce bamboo stick blanks with uniform diameter.

[0008] As a preferred aspect, the freeze-thaw treatment in step S2.1 specifically involves freezing at -32 to -34°C for 3 to 4 hours, followed by thawing at room temperature for 12 to 14 hours.

[0009] As a preferred aspect, the complex bio-enzyme solution in step S2.2 contains 120-140 U / mL of amylase, 80-100 U / mL of hemicellulase, and 50-70 U / mL of pectinase.

[0010] As a preferred aspect, the "medium temperature-high temperature-medium temperature" gradient drying method in step S2.3 involves drying at 40-45℃ and 50-60% humidity to a moisture content of 30%; then raising the temperature to 70-75℃ and 30-40% humidity to dry to a moisture content of 10-12%; and finally lowering the temperature to 50-55℃ and 40-50% humidity to dry to a final moisture content of 5-8%.

[0011] As a preferred aspect, S3: the preparation of bamboo skewers specifically includes the following steps: S3.1: Mix 100-120 parts by weight of waterborne phenolic resin prepolymer, 10-15 parts by weight of nano-silica and 8-10 parts by weight of modified nanocellulose, and then stir and disperse to obtain a reinforcing modifier; S3.2: Place the bamboo skewer blanks in an impregnation tank, evacuate to -0.09MPa and maintain for 20-40 minutes. Then, add the reinforcing modifier under vacuum to completely submerge the bamboo skewer blanks. After that, restore normal pressure and apply a pressure of 0.4-0.8MPa, hold for 130-150 minutes. After that, take out the impregnated bamboo skewers, drain off the excess liquid droplets on the surface, heat cure, and finally grind and polish to obtain the finished bamboo skewer.

[0012] As a preferred aspect, the stirring and dispersing in step S3.1 specifically involves first stirring and mixing at 500-800 rpm for 20-30 min, and then ultrasonically dispersing at 20-30 kHz for 10-20 min.

[0013] As a preferred aspect, the temperature for heat curing in step S3.2 is 120-130℃, and the time is 1-2h.

[0014] The present invention also provides an easy-to-process high-strength bamboo skewer, which is prepared by any of the methods described in the present invention for preparing an easy-to-process high-strength bamboo skewer.

[0015] The present invention has the following advantages: 1. This invention utilizes a reinforcing modifier composed of water-based phenolic resin prepolymer, nano-silica, and modified nanocellulose. This modifier can be vacuum-pressurized to deeply penetrate the bamboo material. The prepolymer structure chemically cross-links with the bamboo fibers during subsequent thermosetting, forming a robust resin-cellulose composite network. The one-dimensional nanostructure of the modified nanocellulose forms "fiber bridges" within the resin matrix. Through cross-linking reactions between the amine groups and the hydroxymethyl and phenolic hydroxyl groups of the phenolic resin prepolymer, a dense organic cross-linked network is constructed, significantly enhancing the mechanical load-bearing capacity of the matrix. Nano-silica, as an inorganic reinforcing phase, fills the tiny pores between the water-based phenolic resin and the bamboo fibers. Simultaneously, it forms hydrogen bonds with the amine groups of the modified nanocellulose and the hydroxyl groups of the resin, creating a synergistic reinforcing structure of "organic fiber network - inorganic filler particles." This significantly improves the bending strength of the bamboo sticks, preventing breakage. Furthermore, the highly cross-linked network formed after the phenolic resin cures, along with the filling of nanoparticles, effectively seals the hydrophilic hydroxyl groups and internal pores of the bamboo fibers, significantly reducing the moisture absorption and expansion rate of the bamboo sticks. The finished product is less prone to deformation and mold growth in humid environments.

[0016] 2. This invention modifies nanocellulose, making it hydrophobic, which allows it to better intertwine and fuse with phenolic resin molecular chains, achieving uniform dispersion at the nanoscale and avoiding stress concentration caused by agglomeration. Furthermore, the hexylamine long chains introduced through grafting modification possess a certain degree of flexibility, forming a flexible interface layer between the nanocellulose and the resin matrix. When the material is subjected to external force, this flexible interface layer can deform, effectively absorbing and dissipating energy, thereby significantly improving the toughness of the bamboo skewers and avoiding the contradiction of increased strength but increased brittleness. After modification, the nanocellulose... The surface of the modified nanocellulose still retains some active groups, and the introduction of amino groups also increases the reaction sites. These active groups can be tightly adsorbed and bound to the bamboo fiber through hydrogen bonding and other interactions. This makes the modified nanocellulose a strong "nanobridge" connecting natural bamboo fiber and synthetic resin, binding the two more firmly into a whole, significantly improving stress transmission efficiency, and thus effectively improving the mechanical properties of bamboo sticks. In addition, the alkyl chains on the surface of the modified nanocellulose reduce the hydrophilicity of the bamboo sticks, and the cross-linking network formed by it and the resin can seal the pores and hydroxyl groups of the bamboo, reducing the water penetration channels and preventing the bamboo sticks from getting damp and moldy.

[0017] 3. This invention first involves freeze-thawing the bamboo strips. This process, through physical and mechanical action, constructs a network of interconnected pores and loosens non-cellulose components, providing a "channel" and "exposed substrate" for the rapid penetration and efficient catalysis of the bio-enzyme solution. Simultaneously, it facilitates the rapid penetration of subsequent reinforcing and modifying agents into the bamboo strips. The subsequent composite bio-enzyme treatment involves amylase degrading starch granules stored in the bamboo cells, significantly improving the bamboo strips' resistance to mold and insects. Hemicellulase breaks down the hemicellulose that encapsulates and connects the cellulose microfibrils in the bamboo strips, opening up the more microscopic fiber structure and exposing more cellulose surface. Pectinase degrades pectin in the intercellular layer and cell walls, softening and loosening the bamboo. The loose bamboo structure further promotes the separation of components and the expansion of pores. Specific catalysis removes loosened non-cellulose impurities after freeze-thaw cycles, avoiding pore blockage caused by impurity residues. It also further optimizes the bamboo strip structure, laying the foundation for the deep penetration of subsequent reinforcing modifiers. After removing impurities such as starch and hemicellulose, the exposed cellulose surface contains a large number of free hydroxyl groups. These highly active groups can form stronger hydrogen bonds or chemical bonds with phenolic resins and modified nanocellulose in the reinforcing modifiers, thereby improving the interfacial bonding between the bamboo strips and the reinforcing resin. This achieves a chemical bond and physical interweaving between the "bamboo strip matrix and reinforcing modifier," effectively improving the mechanical properties of the bamboo sticks.

[0018] 4. This invention employs a "medium-high-medium temperature" gradient drying method to dry bamboo skewers. In the first stage, drying is carried out at a lower temperature in a higher humidity environment, ensuring that the evaporation rates of moisture inside and on the surface of the bamboo skewer are similar. Moisture can be gently discharged through the channels opened during pre-treatment, preventing premature closure of capillaries due to excessively rapid drying. This maintains unobstructed channels for subsequent deep drying. This stage safely reduces the moisture content to near the fiber saturation point, achieving a gradual removal of free water while preventing the formation of a hard surface crust. After pre-drying, the moisture gradient between the inside and outside of the bamboo skewer decreases. At this point, raising the temperature to a high temperature and lowering the humidity accelerates moisture evaporation, rapidly reducing the moisture content. Simultaneously, the medium humidity environment prevents excessively rapid evaporation at high temperatures, which could lead to moisture loss. When bamboo skewer fibers shrink excessively and are dried quickly, a tiny moisture gradient remains inside the skewer. This stage involves adjusting to a medium temperature and humidity environment, allowing the residual moisture inside the skewer to diffuse evenly and evaporate slowly. The temperature is lowered from high temperature, and the humidity is appropriately increased, creating a mild "aging" environment. This effectively relaxes and homogenizes the internal stress that was not fully released in the previous stage, preventing deformation due to residual stress during use. The gradient drying method ensures that the micro-nano channels opened by freeze-thaw and enzyme treatment are not damaged or collapsed during the entire process of moisture removal. Furthermore, by effectively controlling the drying stress, the final bamboo skewer blanks are free of cracks and deformation, which can effectively improve the yield rate. Attached Figure Description

[0019] Figure 1This is a process flow diagram of the preparation method of easy-to-process high-strength bamboo sticks used in the embodiments of the present invention. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention.

[0021] Example 1: A method for preparing easily processed, high-strength bamboo skewers, refer to... Figure 1 ,include: S1: Preparation of modified nanocellulose S1.1: 1 part by weight of TEMPO oxidized nanocellulose was added to 25 parts by weight of HAc-NaAc buffer solution with pH 3.5, followed by the addition of sodium periodate. The molar ratio of sodium periodate to TEMPO oxidized nanocellulose was 6:1. Then, 180 parts by weight of deionized water was added. The mixture was then reacted with shaking at 45°C for 48 h in the dark. After the reaction was completed, 20 parts by weight of ethylene glycol were added, and the mixture was allowed to stand for 10 min. Then, the mixture was dialyzed to neutral using a dialysis bag. Finally, the mixture was rotary evaporated to prepare a 1 wt% T-DANF suspension. S1.2: Add n-hexylamine to 8 parts by weight of 1 wt% T-DANF suspension at a ratio of aldehyde group to amino group of 1:1, stir and react in a 30°C water bath for 6 h, add 1 part by weight of sodium borohydride after the reaction is completed, continue stirring and react for 3 h, dialyze to neutral after the reaction is completed, then rotary evaporate and freeze dry to obtain modified nanocellulose. S2: Preparation of bamboo skewer blanks S2.1: Select bamboo with an age of 3-5 years, uniform wall thickness, no mold, and no cracks. Split the bamboo tube into bamboo strips, remove the inner and outer nodes, sand with sandpaper for 10 minutes, clean the bamboo strips with deionized water, then completely immerse the bamboo strips in deionized water and soak them under a vacuum of 0.08MPa for 30 minutes. Drain the surface water, freeze the soaked bamboo strips at -32℃ for 3 hours, then take them out and thaw them in a room temperature environment for 12 hours to obtain freeze-thawed bamboo strips. S2.2: The freeze-thawed bamboo strips were immersed in a compound bio-enzyme solution and then soaked at 50℃ and pH 5.0 for 8 hours to obtain pretreated bamboo strips; wherein, the compound bio-enzyme solution contained 120 U / mL amylase, 80 U / mL hemicellulase and 50 U / mL pectinase. S2.3: The pre-treated bamboo strips are ultrasonically cleaned with 60℃ deionized water for 15 minutes, then shaved, ground, and dried to make bamboo skewer blanks with uniform diameter. A gradient drying method of "medium temperature-high temperature-medium temperature" was adopted: drying was carried out at 40℃ and 50% humidity until the moisture content was 30%; then the temperature was increased to 70℃ and 30% humidity, and drying was carried out until the moisture content was 10%; finally, the temperature was reduced back to 50℃ and 40% humidity, and drying was carried out until the final moisture content was 5%. S3: Preparation of bamboo skewers S3.1: Mix 100 parts by weight of waterborne phenolic resin prepolymer, 10 parts by weight of nano-silica and 8 parts by weight of modified nanocellulose, then stir and mix at 500 rpm for 20 min, and then ultrasonically disperse at 20 kHz for 10 min to obtain the reinforcing modifier. S3.2: Place the bamboo skewer blanks in an impregnation tank, evacuate to -0.09MPa and maintain for 20 minutes. Then, add the reinforcing modifier under vacuum to completely submerge the bamboo skewer blanks. After that, restore normal pressure and apply a pressure of 0.4MPa, maintain the pressure for 130 minutes. Then, take out the impregnated bamboo skewers, drain off the excess liquid droplets on the surface, heat cure at 120℃ for 1 hour, and finally grind and polish to obtain the finished bamboo skewer.

[0022] Example 2, a method for preparing an easy-to-process, high-strength bamboo skewer, see [link to example]. Figure 1 ,include: S1: Preparation of modified nanocellulose S1.1: 2 parts by weight of TEMPO oxidized nanocellulose were added to 30 parts by weight of HAc-NaAc buffer solution with pH 3.5, followed by the addition of sodium periodate. The molar ratio of sodium periodate to TEMPO oxidized nanocellulose was 6:1. Then, 200 parts by weight of deionized water were added. The mixture was then reacted with shaking at 50°C for 50 h in the dark. After the reaction was completed, 22 parts by weight of ethylene glycol were added, and the mixture was allowed to stand for 12 min. Then, the mixture was dialyzed to neutral using a dialysis bag. Finally, the mixture was rotary evaporated to prepare a 2 wt% T-DANF suspension. S1.2: Add n-hexylamine to 10 parts by weight of 2wt% T-DANF suspension at a ratio of aldehyde group to amino group of 1:1, stir and react in a 40℃ water bath for 8 hours. After the reaction is completed, add 2 parts by weight of sodium borohydride, continue stirring and react for 5 hours. After the reaction is completed, dialyze to neutral, then rotary evaporate and freeze dry to obtain modified nanocellulose. S2: Preparation of bamboo skewer blanks S2.1: Select bamboo with an age of 3-5 years, uniform wall thickness, no mold, and no cracks. Split the bamboo tube into bamboo strips, remove the inner and outer nodes, sand with sandpaper for 15 minutes, clean the bamboo strips with deionized water, then completely immerse the bamboo strips in deionized water and soak them under a vacuum of 0.08MPa for 40 minutes. Drain the surface water, freeze the soaked bamboo strips at -34℃ for 4 hours, then take them out and thaw them in a room temperature environment for 14 hours to obtain freeze-thawed bamboo strips. S2.2: The freeze-thawed bamboo strips were immersed in a compound bio-enzyme solution and then soaked at 55℃ and pH 5.5 for 10 hours to obtain pretreated bamboo strips; wherein, the compound bio-enzyme solution contained 140 U / mL amylase, 100 U / mL hemicellulase and 70 U / mL pectinase. S2.3: The pre-treated bamboo strips are ultrasonically cleaned with 70℃ deionized water for 20 minutes, then shaved, ground, and dried to make bamboo skewer blanks with uniform diameter. A gradient drying method of "medium temperature-high temperature-medium temperature" was adopted: drying was carried out at 45℃ and 60% humidity to a moisture content of 30%; then the temperature was increased to 75℃ and 40% humidity, and drying was carried out to a moisture content of 12%; finally, the temperature was adjusted back to 55℃ and 50% humidity, and drying was carried out to a final moisture content of 8%. S3: Preparation of bamboo skewers S3.1: Mix 120 parts by weight of waterborne phenolic resin prepolymer, 15 parts by weight of nano-silica and 10 parts by weight of modified nanocellulose, then stir and mix at 800 rpm for 30 min, and then ultrasonically disperse at 30 kHz for 20 min to obtain the reinforcing modifier. S3.2: Place the bamboo skewer blanks in an impregnation tank, evacuate to -0.09MPa and maintain for 40 minutes. Then, add the reinforcing modifier under vacuum to completely submerge the bamboo skewer blanks. After that, restore normal pressure and apply a pressure of 0.8MPa, and maintain the pressure for 150 minutes. Then, take out the impregnated bamboo skewers, drain off the excess liquid droplets on the surface, and heat cure at 130℃ for 2 hours. Finally, grind and polish to obtain the finished bamboo skewer.

[0023] Example 3, a method for preparing an easy-to-process high-strength bamboo skewer, see [link to example]. Figure 1 ,include: S1: Preparation of modified nanocellulose S1.1: 1.5 parts by weight of TEMPO oxidized nanocellulose was added to 27.5 parts by weight of HAc-NaAc buffer solution with pH 3.5, followed by the addition of sodium periodate. The molar ratio of sodium periodate to TEMPO oxidized nanocellulose was 6:1. Then, 190 parts by weight of deionized water was added. The mixture was then reacted with shaking at 47.5°C for 49 h in the dark. After the reaction was completed, 21 parts by weight of ethylene glycol were added, and the mixture was allowed to stand for 11 min. The mixture was then dialyzed to neutral using a dialysis bag, and finally, it was rotary evaporated to prepare a 1.5 wt% T-DANF suspension. S1.2: Add n-hexylamine to 9 parts by weight of 1.5 wt% T-DANF suspension at a ratio of aldehyde group to amino group of 1:1, stir and react in a water bath at 35°C for 7 h, add 1.5 parts by weight of sodium borohydride after the reaction is completed, continue stirring and react for 4 h, dialyze to neutral after the reaction is completed, and then rotary evaporate and freeze dry to obtain modified nanocellulose. S2: Preparation of bamboo skewer blanks S2.1: Select bamboo with an age of 3-5 years, uniform wall thickness, no mold, and no cracks. Split the bamboo tube into bamboo strips, remove the inner and outer nodes, and sand with sandpaper for 12.5 minutes. Clean the bamboo strips with deionized water, then completely immerse the bamboo strips in deionized water and soak them under a vacuum of 0.08 MPa for 35 minutes. Drain the surface water, freeze the soaked bamboo strips at -33°C for 3.5 hours, and then take them out and thaw them in a room temperature environment for 13 hours to obtain freeze-thawed bamboo strips. S2.2: The freeze-thawed bamboo strips were immersed in a compound bio-enzyme solution and then soaked at 52.5℃ and pH 5.25 for 9 hours to obtain pretreated bamboo strips; wherein, the compound bio-enzyme solution contained 130 U / mL amylase, 90 U / mL hemicellulase and 60 U / mL pectinase. S2.3: The pre-treated bamboo strips are ultrasonically cleaned with 65℃ deionized water for 17.5 minutes, then shaved, ground, and dried to make bamboo skewer blanks with uniform diameter. A gradient drying method of "medium temperature-high temperature-medium temperature" was adopted: drying was carried out at 42.5℃ and 55% humidity until the moisture content was 30%; then the temperature was increased to 72.5℃ and 35% humidity, and drying was carried out until the moisture content was 11%; finally, the temperature was adjusted back to 52.5℃ and 45% humidity, and drying was carried out until the final moisture content was 6.5%. S3: Preparation of bamboo skewers S3.1: Mix 110 parts by weight of waterborne phenolic resin prepolymer, 12.5 parts by weight of nano-silica and 9 parts by weight of modified nanocellulose, then stir and mix at 650 rpm for 25 min, and then ultrasonically disperse at 25 kHz for 15 min to obtain the reinforcing modifier. S3.2: Place the bamboo skewer blanks in an impregnation tank, evacuate to -0.09MPa and maintain for 30 minutes. Then, add the reinforcing modifier under vacuum to completely submerge the bamboo skewer blanks. After that, restore normal pressure and apply a pressure of 0.6MPa, and maintain the pressure for 140 minutes. Then, take out the impregnated bamboo skewers, drain off the excess liquid droplets on the surface, and heat cure at 125℃ for 1.5 hours. Finally, grind and polish to obtain the finished bamboo skewer.

[0024] Comparative Example 1 differs from Example 1 in that step S1 is removed, and the modified nanocellulose in step S3.1 is replaced with an equal amount of nanocellulose, while the remaining steps remain unchanged to prepare the bamboo skewer product. This is referred to as Comparative Example 1.

[0025] Comparative Example 2 differs from Example 1 in that step S1 is removed, and the modified nanocellulose in step S3.1 is replaced with an equal amount of nano-silica, while the remaining steps remain unchanged to prepare the bamboo skewer product. This is referred to as Comparative Example 2.

[0026] Comparative Example 3 differs from Example 1 in that, in Comparative Example 2, the nano-silica in step S3.1 was replaced with an equal amount of modified nanocellulose, while the remaining steps remained unchanged in preparing the bamboo skewer product. This is referred to as Comparative Example 3.

[0027] Comparative Example 4 differs from Example 1 in that the freeze-thaw treatment in step S2.1 is removed, and the bamboo strips subjected to freeze-thaw treatment in step S2.2 are replaced with bamboo strips cleaned with an equal amount of deionized water in step S2.1. The remaining steps are unchanged in preparing the finished bamboo sticks, and this is referred to as Comparative Example 4.

[0028] Comparative Example 5 differs from Example 1 in that step S2 is replaced by "selecting bamboo aged 3-5 years, with uniform wall thickness, no mold, and no cracks, splitting the bamboo tube into strips, removing the inner and outer nodes, sanding with sandpaper for 10 minutes, cleaning the bamboo strips with deionized water, then completely immersing the bamboo strips in a 5wt% sodium hydroxide solution, then heating at 100°C for 3 hours, then washing with deionized water until neutral, then shaving, grinding, and drying to produce a bamboo skewer blank with a uniform diameter". The remaining steps are unchanged to prepare the finished bamboo skewer, and this is referred to as Comparative Example 5.

[0029] Comparative Example 6 differs from Example 1 in that the "medium temperature-high temperature-medium temperature" gradient drying in step S2.3 is replaced with drying at 90°C to a moisture content of 5%, while the remaining steps remain unchanged to prepare the bamboo skewers. This is referred to as Comparative Example 6.

[0030] Comparative Example 7 differs from Example 1 in that it uses commercially available incense sticks and is referred to as Comparative Example 7.

[0031] Comparative Example 8 differs from Example 1 in that steps S1 and S3 are removed, while the remaining steps remain unchanged to prepare the bamboo skewer blank, which is the finished bamboo skewer. This is referred to as Comparative Example 8.

[0032] The bamboo skewers of Examples 1-3 and Comparative Examples 1-7 had a diameter of 2.0±0.1mm and a length of 150±2mm. The bending strength of each group of bamboo skewers was determined according to GB / T15780-1995 "Test Methods for Physical and Mechanical Properties of Bamboo". The test was conducted three times and the average value was taken. The test results are shown in Table 1.

[0033] Table 1. Results of flexural strength tests in Examples 1-3 and Comparative Examples 1-7

[0034] As can be seen from the data in Table 1, compared with Comparative Example 7, the bamboo skewers prepared by this invention have good bending strength. The data from Comparative Example 1 shows that modification of nanocellulose can effectively improve the bending strength of bamboo skewers and reduce the risk of breakage. The data from Comparative Examples 2-3 show that the bending strength significantly decreases when either nano-silica or modified nanocellulose is missing, indicating that the two can form a synergistic reinforcing structure of "organic fiber network - inorganic filler particles," greatly improving the bending strength of bamboo skewers. The data from Comparative Examples 4 and 5 show that freeze-thaw treatment followed by composite bio-enzyme treatment of bamboo strips is beneficial to improving the bending strength of bamboo skewers. The data from Comparative Example 6 shows that using a "medium-high-medium temperature" gradient drying method to dry bamboo skewers has a positive effect on improving their bending strength.

[0035] The bamboo sticks prepared in Examples 1-3 and Comparative Examples 1, 4-5, and 7-8 were tested for mildew resistance in accordance with GB / T18261-2013. The test results are shown in Table 2.

[0036] Potato dextrose agar medium was prepared and inoculated with a mixed mold spore suspension (Aspergillus niger, Penicillium, and Trichoderma in a mass ratio of 1:1:1). Sterilized bamboo sticks were placed in their respective media and cultured for 28 days in an incubator at 28±1℃ and relative humidity >90%. The mycelial growth area on the bamboo stick surface was observed: Grade 0: no mold; Grade 1: moldy area <10%; Grade 2: moldy area 10-30%; Grade 3: moldy area 30-60%; Grade 4: moldy area 60-80%; Grade 5: moldy area >80%.

[0037] Table 2. Results of mildew resistance test in Examples 1-3 and Comparative Examples 1, 4-5, and 7-8

[0038] As can be seen from the data in Table 2, compared with Comparative Example 7, the bamboo skewers prepared by this invention have excellent anti-mold properties. The poor anti-mold level of Comparative Example 1 indicates that the modification treatment of nanocellulose reduces the hydrophilicity of the bamboo skewers by the alkyl chains on their surface, thus preventing the bamboo skewers from getting damp and moldy. As can be seen from the data of Comparative Examples 4-5, the bamboo skewers treated with freeze-thaw process have better anti-mold effects because freeze-thaw process facilitates subsequent enzymatic hydrolysis, thereby improving the anti-mold and anti-insect capabilities of the bamboo skewers. Moreover, compared with alkaline boiling treatment, freeze-thaw enzymatic hydrolysis treatment has a better anti-mold effect. As can be seen from the data of Comparative Example 8, the bamboo skewers prepared by modifying them with a reinforcing modifier composed of water-based phenolic resin prepolymer, nano-silica, and modified nanocellulose are less prone to mold.

[0039] 10,000 bamboo skewers with a diameter of 2.0±0.1 mm and a length of 150±2 mm were produced using the processes of Examples 1-3 and Comparative Example 6, respectively. The defect rate was measured, and the results are shown in Table 3. Cracks / Friction: Under sufficient light, any visible cracks or fissures on the surface or end of the bamboo skewer indicate a defective product.

[0040] Bending and Deformation: Place the bamboo skewer on a horizontal glass plate and roll it gently. If the maximum gap between the bamboo skewer and the glass plate exceeds 1 / 5 of the bamboo skewer's diameter, or if there is obvious bending visible to the naked eye, it is a defective product.

[0041] Mold and stains: Any visible mold spots, discoloration, or unremovable stains on the surface indicate a defective product.

[0042] Defect rate (%) = Total number of bamboo skewers judged as defective / Total number of bamboo skewers × 100%.

[0043] Table 3. Results of residual rate determination in Examples 1-3 and Comparative Example 6

[0044] As can be seen from the data in Table 3, the gradient drying method of the present invention can significantly reduce the defect rate of bamboo sticks in the production process and effectively improve the yield rate compared with the high temperature drying method of the prior art.

[0045] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Parts not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A method for preparing easily processed, high-strength bamboo skewers, characterized in that, include: S1: Preparation of modified nanocellulose; TEMPO-oxidized nanocellulose was added to HAc-NaAc buffer, followed by sodium periodate and deionized water. The mixture was shaken and reacted, then ethylene glycol was added and allowed to stand before dialyzing to neutral. The mixture was then rotary evaporated to obtain a 1-2 wt% T-DANF suspension, which was then reacted with n-hexylamine. Sodium borohydride was added and the reaction was continued before dialyzing, rotary evaporation, and lyophilization to obtain modified nanocellulose. S2: Preparation of bamboo skewer blanks; Select 3-5 year old moso bamboo to make bamboo strips, clean and polish them and then dry them. After soaking and freeze-thaw treatment, soak them in a compound biological enzyme solution. After soaking, clean the bamboo strips with deionized water using ultrasonic cleaning. Then, cut, grind, and dry them to make bamboo sticks with uniform diameter. S3: Preparation of bamboo skewers; Mix 100-120 parts by weight of waterborne phenolic resin prepolymer with 10-15 parts by weight of nano-silica and 8-10 parts by weight of modified nanocellulose to prepare a reinforcing modifier. Vacuum impregnate the bamboo skewer blank with the reinforcing modifier and pressurize it. After removal, heat cure it and polish it to obtain the finished bamboo skewer.

2. The method for preparing an easily processed, high-strength bamboo skewer according to claim 1, characterized in that, S1: The preparation of modified nanocellulose includes the following steps: S1.1: Add 1-2 parts by weight of TEMPO oxidized nanocellulose to 25-30 parts by weight of HAc-NaAc buffer solution with pH 3.5, then add sodium periodate, with a molar ratio of sodium periodate to TEMPO oxidized nanocellulose of 6:1, then add 180-200 parts by weight of deionized water, and then react with shaking at 45-50℃ under light-protected conditions for 48-50 h. After the reaction is completed, add 20-22 parts by weight of ethylene glycol, let stand for 10-12 min, then dialyze to neutral using a dialysis bag, and finally rotary evaporate to prepare a 1-2 wt% T-DANF suspension. S1.2: Add n-hexylamine to 8-10 parts by weight of 1-2 wt% T-DANF suspension at a ratio of aldehyde to amino of 1:1, stir and react in a water bath at 30-40℃ for 6-8 h. After the reaction is complete, add 1-2 parts by weight of sodium borohydride, continue stirring and react for 3-5 h. After the reaction is complete, dialyze to neutral, then rotary evaporate and freeze dry to obtain modified nanocellulose.

3. The method for preparing an easily processed, high-strength bamboo skewer according to claim 1, characterized in that, S2: Preparation of the rough bamboo skewer blanks, specifically including the following steps: S2.1: Select bamboo that is 3-5 years old, with uniform wall thickness, no mold, and no cracks. Split the bamboo tube into strips, remove the inner and outer nodes, and sand it with sandpaper for 10-15 minutes. After cleaning the bamboo strips with deionized water, completely immerse the bamboo strips in deionized water and soak them under a vacuum of 0.08MPa for 30-40 minutes. Drain the surface water and freeze-thaw the soaked bamboo strips to obtain freeze-thawed bamboo strips. S2.2: Immerse the freeze-thawed bamboo strips in a compound bio-enzyme solution, and then soak them at 50-55℃ and pH 5.0-5.5 for 8-10 hours to obtain pretreated bamboo strips; S2.3: The pre-treated bamboo strips are ultrasonically cleaned with deionized water at 60-70℃ for 15-20 minutes, then shaved and rounded, and dried using a "medium temperature-high temperature-medium temperature" gradient drying method to produce bamboo stick blanks with uniform diameter.

4. The method for preparing an easily processed, high-strength bamboo skewer according to claim 3, characterized in that, The freeze-thaw treatment in step S2.1 specifically involves freezing at -32 to -34°C for 3-4 hours, followed by thawing at room temperature for 12-14 hours.

5. The method for preparing an easily processed, high-strength bamboo skewer according to claim 3, characterized in that, The compound bio-enzyme solution in step S2.2 contains 120-140 U / mL of amylase, 80-100 U / mL of hemicellulase, and 50-70 U / mL of pectinase.

6. The method for preparing an easily processed, high-strength bamboo skewer according to claim 3, characterized in that, In step S2.3, the "medium temperature-high temperature-medium temperature" gradient drying method involves drying at 40-45℃ and 50-60% humidity to a moisture content of 30%; then raising the temperature to 70-75℃ and 30-40% humidity to a moisture content of 10-12%; and finally lowering the temperature to 50-55℃ and 40-50% humidity to a final moisture content of 5-8%.

7. The method for preparing an easily processed, high-strength bamboo skewer according to claim 1, characterized in that, S3: Preparation of bamboo skewers, specifically including the following steps: S3.1: Mix 100-120 parts by weight of waterborne phenolic resin prepolymer, 10-15 parts by weight of nano-silica and 8-10 parts by weight of modified nanocellulose, and then stir and disperse to obtain a reinforcing modifier; S3.2: Place the bamboo skewer blanks in an impregnation tank, evacuate to -0.09MPa and maintain for 20-40 minutes. Then, add the reinforcing modifier under vacuum to completely submerge the bamboo skewer blanks. After that, restore normal pressure and apply a pressure of 0.4-0.8MPa, hold for 130-150 minutes. After that, take out the impregnated bamboo skewers, drain off the excess liquid droplets on the surface, heat cure, and finally grind and polish to obtain the finished bamboo skewer.

8. The method for preparing an easy-to-process, high-strength bamboo skewer according to claim 7, characterized in that, In step S3.1, the stirring and dispersing process involves first stirring and mixing at 500-800 rpm for 20-30 min, and then ultrasonically dispersing at 20-30 kHz for 10-20 min.

9. The method for preparing an easily processed, high-strength bamboo skewer according to claim 7, characterized in that, In step S3.2, the temperature for heat curing is 120-130℃ and the time is 1-2 hours.

10. A high-strength bamboo skewer that is easy to process, characterized in that, It is prepared by the method for preparing an easy-to-process, high-strength bamboo skewer as described in any one of claims 1-9.

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