Modified rice hull powder-straw residue composite degradable food-grade chopsticks and preparation method thereof

Abstract

The invention relates to the technical field of tableware processing, in particular to a modified rice hull powder-straw residue composite degradable food-grade chopstick and a preparation method thereof.The modified rice hull powder-straw residue composite degradable food-grade chopstick comprises a chopstick base material, wherein core raw materials of the chopstick base material are rice hull powder and straw residues which are subjected to citric acid-KH560 dual modification treatment; wherein the citric acid modification ratio of the rice hull powder to citric acid is 10: 1; the food-grade bonding and reinforcing system comprises xanthan gum, flour, wood pulp boards and warm water and is used for mixing and molding the modified rice hull powder and the straw residues to form a stable green body; the PLA degradable coating is coated on the surface of the chopstick base material and is used for improving the wear resistance, smoothness and overall attractiveness of the surface of the chopstick. According to the invention, high-valued utilization of the rice hull powder is realized through chemical modification, the application bottleneck of agricultural and forestry wastes in the tableware field is broken through, the problem of poor consistency of mass-produced products is solved through standardized modification process parameters and raw material ratio, and the defective rate is reduced; the modified rice hull powder and the straw residues are used as core raw materials, so that the consumption of traditional resources is reduced.

Description

Technical Field

[0001] This invention belongs to the field of tableware processing technology, specifically involving the formulation improvement, molding process optimization and functional design of biodegradable food-grade chopsticks with citric acid-KH560 modified rice husk powder and straw residue as core raw materials. It also covers the chemical modification of agricultural and forestry waste and its high-value application in the field of food contact materials. Background Technology

[0002] Chopsticks are long, thin sticks used to pick up food or other items, and are usually made of materials such as wood, bamboo, or metal.

[0003] Traditional chopsticks currently on the market suffer from problems such as material defects, high resource consumption, limited functionality, and poor mass production consistency. Unmodified rice husk powder has poor compatibility with organic adhesive systems and low surface activity, resulting in insufficient toughness and easy cracking of composite tableware substrates. This restricts the large-scale application of rice husk powder in the tableware field. There is an urgent need to improve the interfacial bonding performance of rice husk powder through chemical modification technology to solve the performance shortcomings of composite tableware based on agricultural and forestry waste. Therefore, this paper proposes a modified rice husk powder-straw residue composite biodegradable food-grade chopsticks and its preparation method to solve the above problems. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a modified rice husk powder-straw residue composite biodegradable food-grade chopsticks and its preparation method. This method solves the problem of poor compatibility between unmodified rice husk powder and the adhesive system. By using citric acid-KH560 dual modification to enhance the surface activity of the rice husk powder, it strengthens the toughness and structural stability of the composite substrate. Standardized process parameters and composite raw material ratios for citric acid-KH560 modified rice husk powder are determined, solving the problems of poor product consistency and high defect rate during mass production. The invention balances the biodegradability, high-temperature resistance, and durability of the chopsticks, optimizing the molding, coating, and drying processes. This promotes the high-value utilization of modified agricultural and forestry waste in the food-grade tableware field, reducing dependence on traditional resources such as wood and plastics.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a modified rice husk powder-straw residue composite biodegradable food-grade chopsticks, comprising: Chopstick base material: Its core raw materials are rice husk powder and straw residue that have been double-modified with citric acid-KH560; among them, the citric acid modification ratio of rice husk powder is rice husk powder:citric acid = 10:1; Food-grade adhesive reinforcement system: containing xanthan gum, flour, wood pulp board and warm water, used to mix modified rice husk powder and straw residue to form a stable green body; PLA (polylactic acid) biodegradable coating: applied to the surface of the chopsticks substrate to improve the wear resistance, smoothness and overall aesthetics of the chopsticks surface.

[0006] Furthermore, in the food-grade adhesive reinforcement system, the standard dosage ratios of xanthan gum, flour, wood pulp board, and warm water are as follows: xanthan gum 58.125g, flour 105g, wood pulp board 12g, and warm water approximately 325g.

[0007] Furthermore, the chopstick substrate is biodegradable and can degrade in the natural environment after use, and its tail can be designed as a detachable structure.

[0008] Furthermore, flower seeds can be embedded in the tail of the chopsticks and sealed with biodegradable materials, so that the chopsticks can be disassembled and planted after use.

[0009] Furthermore, a method for preparing modified rice husk powder-straw residue composite biodegradable food-grade chopsticks, comprising the method for preparing modified rice husk powder-straw residue composite biodegradable food-grade chopsticks as described in any one of claims 1-4, includes the following steps: Step 1: Raw material preparation: Purchase and weigh rice husk powder, straw residue, citric acid, KH560, PLA material, xanthan gum, flour, and wood pulp board according to the formula; Step 2: Rice husk powder modification: Complete citric acid esterification modification and KH560 coating modification to obtain active modified rice husk powder; Step 3: Substrate preparation: Mix the double-modified rice husk powder, straw residue, xanthan gum, flour, and wood pulp board evenly, then slowly add about 325g of warm water and stir until a uniform and viscous mixture is formed. Step 4: Molding process: The lumpy mixture is injected into the chopstick forming mold and pressed into a chopstick blank according to the preset mold and pressure parameters; Step 5: Coating Adhesion: Spray PLA coating material evenly onto the surface of the chopstick blank, and dry and cure to ensure that the coating adheres tightly to the substrate; Step 6: Functional processing: Imprint festival / seasonal patterns on the surface of the chopsticks, leave a cavity at the end to embed flower seeds and seal it with biodegradable material; Step 7: Drying and testing: Dry the chopstick blanks in a 40℃ environment for 20 hours, test indicators such as toughness and coating adhesion, and fine-tune the proportions and process parameters to ensure compliance with food-grade standards.

[0010] Furthermore, the modification of rice husk powder in step 2 specifically includes the following steps: Step 201: Dissolve 15g of citric acid in 85g of water to prepare a citric acid solution. Dry the rice husk powder and heat it to 130°C. Slowly add the citric acid solution and stir. Perform an esterification reaction at 140-160°C for 10 minutes. After cooling, wash with hot water until neutral and then grind into a fine powder to complete the citric acid esterification modification. Step 202: Dissolve a quantitative amount of KH560 in ethanol, and then add it to the dried rice husk powder treated in step 201 at 100°C while stirring, so that KH560 is evenly coated on the surface of the rice husk powder, thus completing the KH560 modification.

[0011] Furthermore, the addition of warm water in step 3 specifically includes: slowly adding water multiple times according to the state of the powder until it becomes a viscous, lumpy mixture, with the water content being 40% to 50%.

[0012] Furthermore, in step 4, the lumpy mixture is injected into the chopstick forming mold, and the pressure parameter is 10 to 36 tons, according to the preset mold and pressure parameters.

[0013] Furthermore, in step 5, the PLA coating material is evenly sprayed onto the surface of the chopstick blank, and the temperature needs to be kept constant between 40°C and 50°C.

[0014] Compared with the prior art, the technical solution of this application has the following beneficial effects: 1. The modified rice husk powder-straw residue composite biodegradable food-grade chopsticks and their preparation method. Product performance: Citric acid-KH560 modified rice husk powder significantly improves the toughness and stability of the composite substrate, solving the problem of easy cracking of unmodified rice husk powder-based tableware. The chopsticks have high temperature resistance and biodegradability. The PLA coating has good wear resistance and long service life. 2. The modified rice husk powder-straw residue composite biodegradable food-grade chopsticks and their preparation method, raw material modification: high-value utilization of rice husk powder is achieved through chemical modification, breaking through the bottleneck of the application of agricultural and forestry waste in the tableware field; 3. The modified rice husk powder-straw residue composite biodegradable food-grade chopsticks and their preparation method have the following production efficiency: standardized modification process parameters and raw material ratios solve the problem of poor consistency in mass-produced products and reduce the defect rate; 4. The modified rice husk powder-straw residue composite biodegradable food-grade chopsticks and their preparation method are resource-saving and environmentally friendly: using modified rice husk powder and straw residue as core raw materials, reducing the consumption of traditional resources, and the product can be naturally degraded or replanted after use, which is in line with the trend of green development; 5. The modified rice husk powder-straw residue composite biodegradable food-grade chopsticks and their preparation method have the following functional value: they combine the use of tableware, creative planting, and gift collection value, meeting the diversified needs of consumers and enhancing market competitiveness. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating the preparation method of a modified rice husk powder-straw residue composite biodegradable food-grade chopsticks according to the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Please see Figure 1 The modified rice husk powder-straw residue composite biodegradable food-grade chopsticks in this embodiment include: Chopstick base material: Its core raw materials are rice husk powder and straw residue that have been double-modified with citric acid-KH560; among them, the citric acid modification ratio of rice husk powder is rice husk powder:citric acid = 10:1; Food-grade adhesive reinforcement system: containing xanthan gum, flour, wood pulp board and warm water, used to mix modified rice husk powder and straw residue to form a stable green body; PLA (polylactic acid) biodegradable coating: applied to the surface of the chopsticks substrate to improve the wear resistance, smoothness and overall aesthetics of the chopsticks surface.

[0018] Example 1 This embodiment provides a method for preparing modified rice husk powder-straw residue composite biodegradable food-grade chopsticks suitable for large-scale stable production.

[0019] Step A1: Raw material preparation. Accurately weigh 1000g of dried rice husk powder, 500g of straw residue (ground to 100 mesh), 100g of citric acid, 20g of KH560 silane coupling agent, 200g of PLA polylactic acid granules (for coating), 58.125g of xanthan gum, 105g of flour, and 12g of wood pulp board. Prepare sufficient warm water (approximately 50℃) and an appropriate amount of anhydrous ethanol. Step A2: Citric acid esterification modification of rice husk powder. Dissolve 100g of citric acid powder in 566g of water and stir until completely dissolved to obtain a citric acid solution. Place 1000g of rice husk powder in a heatable and stirred reactor, heat to 130℃ and keep warm for 10 minutes to remove moisture. Under continuous stirring, slowly add the above citric acid solution to the hot rice husk powder, maintain the system temperature at 150℃ (±5℃), and carry out the esterification reaction for 10 minutes. After the reaction is completed, cool the material and wash it repeatedly with a large amount of hot water (60-80℃) until the washing liquid is neutral (pH 6.5-7.5). Then dry the wet material at 80℃ and grind it into fine powder (passing through a 200-mesh sieve) to obtain citric acid modified rice husk powder. Step A3: KH560 silane coupling agent coating modification of rice husk powder. Dissolve 20g of KH560 silane coupling agent in 200g of anhydrous ethanol to prepare a treatment solution. Place the citric acid modified rice husk powder obtained in step A2 in a heatable container and heat it to 100℃. While stirring continuously, slowly and evenly add the KH560-ethanol treatment solution to the hot rice husk powder dropwise. Maintain the temperature at 100℃ and continue stirring for 20 minutes to allow KH560 to fully evaporate the solvent and evenly coat the surface of the rice husk powder particles. Then continue drying at 100℃ for 10 minutes to completely remove residual ethanol, and obtain active rice husk powder that has been dually modified with citric acid and KH560. Step A4: Substrate preparation and mixing. Add the double-modified rice husk powder obtained in step A3, 500g of straw residue powder, 58.125g of xanthan gum, 105g of flour, and 12g of wood pulp board to a high-powered mixer. First, dry mix at low speed for 5 minutes until uniform. Then, while continuing to mix at low speed, slowly add about 325g of warm water (50℃) in a thin stream. Add water in three batches, adding about one-third of the water each time. After the water added in the previous batch has been basically absorbed by the material and the material is moist and granular, add water again. The total mixing time is about 15 minutes. Finally, the material forms a uniform, viscous, non-sticky, and somewhat plastic agglomerated mixture. Step A5: Pressing and molding. The lumpy mixture obtained in step A4 is quickly transferred to a preheated chopstick molding mold at 60°C. A hydraulic press is used for pressing, with a pressing pressure of 20 tons and a holding time of 30 seconds. After demolding, a chopstick blank with a smooth surface and dense structure is obtained. Step A6: PLA coating adhesion and curing. Dissolve 200g of PLA polylactic acid granules in 800g of dichloromethane to prepare a 20% coating solution. Add 5g of triethyl citrate as a plasticizer and stir evenly. Fix the chopstick blank obtained in step A5 on the dip-coating rack and slowly immerse it in the PLA coating solution. After 5 seconds, pull it out at a uniform speed and drain the excess solution. Then, suspend the coated chopsticks in a programmable temperature-controlled oven for gradient curing: first, cure at 45℃ for 1 hour to allow the solvent to evaporate slowly; then raise the temperature to 60℃ and cure for 2 hours. Keep the air circulating in the oven during the curing process. Finally, a transparent, smooth, dense and firmly bonded PLA biodegradable coating is formed on the surface of the chopstick substrate.

[0020] Step A7: Functionalization and Final Processing. Using a hot-press printing mold, auspicious cloud patterns with a Spring Festival theme are embossed onto the surface of the chopsticks after the coating has fully cured. At the end of the chopsticks, a micro-cavity with a diameter of 2mm and a depth of 10mm is pre-drilled using a precision drill bit. A lavender seed is filled into the cavity, and then it is sealed with molten biodegradable PLA material. Finally, all coated chopstick blanks are placed in a constant temperature drying oven at 40℃ for 20 hours for final drying. After drying, random samples are taken to test the chopsticks' three-point bending strength (≥25MPa), PLA coating adhesion (reaching grade 0), hot water resistance (no cracking or coating peeling after immersion in boiling water at 100℃ for 1 hour), and food safety (compliant with GB4806 series standards). Those that pass the tests are the modified rice husk powder-straw residue composite biodegradable food-grade chopsticks product obtained in this embodiment.

[0021] Example 2 Based on Example 1, this embodiment focuses on explaining the specific process parameters for different raw material ratios and the optimization of the "strict control of water addition method".

[0022] In this embodiment, the proportions of the core raw materials and the mixing process are adjusted: The amount of double-modified rice husk powder was adjusted to 1200g, and the amount of straw residue was adjusted to 300g, in order to further improve the toughness and hardness of the substrate.

[0023] In the food-grade adhesive reinforcement system, the amounts of xanthan gum, flour, and wood pulp board remain constant, but the addition of warm water is precisely controlled. A high-speed disperser is used for mixing. After premixing the dry powder, 325g of warm water (45℃) is injected into the center of the mixing dry powder at a constant rate of 5ml / s using a peristaltic pump. The mixing speed is set to initially mix at a low speed of 200rpm, then increase to a high-speed shearing speed of 600rpm for 3 minutes after half the water has been added, and finally decrease to a medium speed of 300rpm until a dough forms. This strictly controlled method of adding water and mixing ensures that the moisture is instantly and evenly dispersed, the material forms a dough quickly, and the dough has better viscoelasticity. The moisture content is precisely controlled at 42% of the total weight of the material, which is beneficial for subsequent high-precision pressing and molding.

[0024] Other preparation steps, such as double modification of rice husk powder (temperature parameters are the same as in Example 1), molding pressure (25 tons in this example), PLA coating and gradient curing, and functional processing such as embedding sunflower seeds at the tail and sealing, are all carried out in accordance with Example 1.

[0025] The chopsticks prepared in this embodiment maintain excellent biodegradability while further improving their bending strength and dimensional stability compared to the product of Example 1.

[0026] Example 3 This embodiment mainly demonstrates a specific implementation scheme of "improving the curing method to achieve integrated bonding between the substrate and the PLA coating", and uses different molding pressures.

[0027] The substrate preparation and mixing process in this embodiment is the same as in embodiment 1. In molding step A5, the pressing pressure is adjusted to 30 tons to obtain a higher density preform, reduce internal porosity, and provide a smoother and more solid base for coating bonding.

[0028] The key steps for improving coating adhesion are as follows: Substrate surface pretreatment: Before PLA coating, the pressed chopstick blank is placed in a low-temperature plasma treatment device and treated for 60 seconds at 100W power under an argon atmosphere. This treatment effectively cleans the surface and introduces oxygen-containing polar groups, significantly improving the surface energy of the substrate.

[0029] Coating and Curing Process: Prepare the PLA coating solution (same as in Example 1). Preheat the plasma-treated blank to 50°C, then perform spraying. The spraying environment temperature is strictly controlled at 45°C. After spraying, a curing method combining far-infrared radiation heating and hot air circulation is used. Specifically: First, radiate heating with far-infrared rays of wavelength 4-10μm at 50°C for 15 minutes, utilizing their penetrating power to simultaneously and gently raise the temperature of the substrate surface and the coating interface, promoting the diffusion of PLA molecular chains into the substrate micropores. Then, transfer to a 60°C hot air circulating oven for curing for 1.5 hours. This improved curing method integrates surface activation, simultaneous interface heating, and molecular diffusion mechanisms. Testing shows that the cross-cut adhesion between the coating and the substrate reaches the highest level (ISO Class 0), achieving a truly integrated and strong bond.

[0030] The remaining functional processing (imprinting Mid-Autumn Festival patterns, embedding osmanthus seeds at the tail) and final drying and testing steps are the same as in Example 1.

[0031] In summary, this modified rice husk powder-straw residue composite biodegradable food-grade chopsticks and their preparation method are described. 1. Product performance: Citric acid-KH560 modified rice husk powder significantly improves the toughness and stability of the composite substrate, solving the problem of cracking in unmodified rice husk powder-based tableware. The chopsticks are also heat-resistant and biodegradable, and the PLA coating has good wear resistance and long service life. 2. Raw material modification: Through chemical modification, rice husk powder is utilized at a high value, breaking through the bottleneck of agricultural and forestry waste in the tableware field; 3. Production efficiency: Standardized modification process parameters and raw material ratios solve the problem of poor consistency in mass-produced products and reduce the defect rate; 4. Resource and environmental protection: Using modified rice husk powder and straw residue as core raw materials, it reduces the consumption of traditional resources. After use, the product can be naturally degraded or used for secondary planting, which is in line with the trend of green development. 5. Functional value: It integrates the value of tableware use, creative planting, and gift collection, meeting the diversified needs of consumers and enhancing market competitiveness.

[0032] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0033] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A modified rice husk powder-straw residue composite biodegradable food-grade chopsticks, characterized in that, include: Chopstick base material: Its core raw materials are rice husk powder and straw residue that have been double-modified with citric acid-KH560; among them, the citric acid modification ratio of rice husk powder is rice husk powder:citric acid = 10:1; Food-grade adhesive reinforcement system: containing xanthan gum, flour, wood pulp board and warm water, used to mix modified rice husk powder and straw residue to form a stable green body; PLA (polylactic acid) biodegradable coating: applied to the surface of the chopsticks substrate to improve the wear resistance, smoothness and overall aesthetics of the chopsticks surface.

2. The modified rice husk powder-straw residue composite biodegradable food-grade chopsticks according to claim 1, characterized in that: In the food-grade adhesive reinforcement system, the standard ratio of xanthan gum, flour, wood pulp board and warm water is as follows: xanthan gum 58.125g, flour 105g, wood pulp board 12g and warm water approximately 325g.

3. The modified rice husk powder-straw residue composite biodegradable food-grade chopsticks according to claim 1, characterized in that: The chopstick substrate is biodegradable and can degrade in the natural environment after use. Furthermore, its tail can be designed as a detachable structure.

4. The modified rice husk powder-straw residue composite biodegradable food-grade chopsticks according to claim 3, characterized in that, Flower seeds can be embedded in the tail of the chopsticks and sealed with biodegradable materials, so that the chopsticks can be disassembled and planted after use.

5. A method for preparing modified rice husk powder-straw residue composite biodegradable food-grade chopsticks, comprising the method for preparing modified rice husk powder-straw residue composite biodegradable food-grade chopsticks according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Raw material preparation: Purchase and weigh rice husk powder, straw residue, citric acid, KH560, PLA material, xanthan gum, flour, and wood pulp board according to the formula; Step 2: Rice husk powder modification: Complete citric acid esterification modification and KH560 coating modification to obtain active modified rice husk powder; Step 3: Substrate preparation: Mix the double-modified rice husk powder, straw residue, xanthan gum, flour, and wood pulp board evenly, then slowly add about 325g of warm water and stir until a uniform and viscous lumpy mixture is formed. Step 4: Molding process: The lumpy mixture is injected into the chopstick forming mold and pressed into a chopstick blank according to the preset mold and pressure parameters; Step 5: Coating Adhesion: Spray PLA coating material evenly onto the surface of the chopstick blank, and dry and cure to ensure that the coating adheres tightly to the substrate; Step 6: Functional processing: Imprint festival / seasonal patterns on the surface of the chopsticks, leave a cavity at the end to embed flower seeds and seal it with biodegradable material; Step 7: Drying and Testing: Place the chopstick blanks in a 40℃ environment to dry for 20 hours, test indicators such as toughness and coating adhesion, and fine-tune the proportions and process parameters to ensure compliance with food-grade standards.

6. The method for preparing a modified rice husk powder-straw residue composite biodegradable food-grade chopsticks according to claim 5, characterized in that: Step 2, the modification of rice husk powder, specifically includes the following steps: Step 201: Dissolve 15g of citric acid in 85g of water to prepare a citric acid solution. Dry the rice husk powder and heat it to 130°C. Slowly add the citric acid solution and stir. Perform an esterification reaction at 140-160°C for 10 minutes. After cooling, wash with hot water until neutral and then grind into fine powder to complete the citric acid esterification modification. Step 202: Dissolve a quantitative amount of KH560 in ethanol, and then add it to the dried rice husk powder treated in step 201 at 100°C while stirring, so that KH560 is evenly coated on the surface of the rice husk powder, thus completing the KH560 modification.

7. The method for preparing a modified rice husk powder-straw residue composite biodegradable food-grade chopsticks according to claim 5, characterized in that: The addition of warm water in step 3 specifically includes: slowly adding water multiple times according to the state of the powder until it becomes a viscous, lumpy mixture, with the water content being 40% to 50%.

8. The method for preparing a modified rice husk powder-straw residue composite biodegradable food-grade chopsticks according to claim 5, characterized in that: In step 4, the lumpy mixture is injected into the chopstick forming mold, and the pressure parameters are set according to the preset mold and pressure parameters, which are 10 to 36 tons.

9. The method for preparing a modified rice husk powder-straw residue composite biodegradable food-grade chopsticks according to claim 5, characterized in that: Step 5, where the PLA coating material is evenly sprayed onto the surface of the chopstick blank, requires maintaining a constant temperature between 40°C and 50°C.

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