Degradable waterproof foam packaging box and preparation method thereof

Abstract

This invention discloses a biodegradable waterproof foam packaging box and its preparation method, belonging to the field of packaging material technology. It includes drying and sieving polylactic acid (PLA), then adding modified hydrogenated castor oil, flame retardant, maleic anhydride-grafted PLA, epoxy chain extender, and foaming agent, all dried together, into a high-speed mixer to obtain a mixture. The mixture is then placed in a mold preheated to 130-140°C, subjected to a pressure of 3-5 MPa, and the mold temperature is rapidly raised to 170-175°C and held for 2-4 minutes. The pressure is then quickly released and the mold is opened, and the box is cooled under pressure at 50-60°C for 5-7 minutes before demolding to obtain the biodegradable waterproof foam packaging box. This invention's biodegradable waterproof foam packaging box is made from a biodegradable substrate and possesses excellent waterproof and flame-retardant properties.

Description

Technical Field

[0001] This invention belongs to the field of packaging materials technology, and more specifically, relates to a biodegradable waterproof foam packaging box and its preparation method. Background Technology

[0002] With the booming development of the logistics and transportation industry, foam packaging boxes have been widely used in the field of transport packaging due to their low cost and excellent cushioning and shock absorption performance. However, the chemical structure of traditional petroleum-based foam packaging materials is exceptionally stable and difficult to degrade in the natural environment, posing a long-term threat to the ecosystem. Although existing biodegradable foam materials have alleviated environmental pressure to some extent, they have problems such as weak waterproof performance and are prone to moisture absorption and deformation in humid environments, affecting logistics and transportation. Therefore, how to avoid this phenomenon is the key to solving the problem. For example, the invention patent application with publication number CN112608511A discloses a foam packaging box with high surface hardening strength EPP heat-resistant beads and its preparation method. The raw materials used in this foam packaging box are green and environmentally friendly, and the finished EPP beads have high surface strength, low production cost, and good economic benefits. However, the waterproof performance needs to be improved. Summary of the Invention

[0003] Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a biodegradable waterproof foam packaging box and its preparation method. The biodegradable waterproof foam packaging box is made from a biodegradable substrate and has good waterproof and flame-retardant properties.

[0004] Technical solution To solve the above problems, the technical solution adopted by the present invention is as follows: The present invention discloses a method for preparing a biodegradable waterproof foam packaging box, which includes the following steps: (1) Preparation of modified hydrogenated castor oil; (2) Preparation of flame retardants; (3) Dry 90-100 parts by weight of polylactic acid at 50-60℃ for 6-8h, pass through a 180-200 mesh sieve, dry 3-5 parts by weight of modified hydrogenated castor oil, 8-10 parts by weight of flame retardant, 5-8 parts by weight of maleic anhydride grafted polylactic acid, 0.3-0.5 parts by weight of epoxy chain extender, and 1-1.5 parts by weight of Span 60 at 80-90℃ for 6-8h, dry 8-12 parts by weight of foaming agent at 60-70℃ for 4-6h, and then add them together to a high-speed mixer and mix at 30-40℃ for 5-10min to obtain a mixture. (4) Place the mixture into a mold preheated to 130-140℃, apply a pressure of 3-5MPa, and quickly raise the mold temperature to 170-175℃. Keep it warm for 2-4 minutes, then quickly release the pressure and open the mold. Keep it under pressure and cool for 5-7 minutes at 50-60℃. Demold the mold to obtain a biodegradable waterproof foam packaging box.

[0005] Further, in step (1), the method for preparing modified hydrogenated castor oil is as follows: Step 1: Under nitrogen protection, hydrogenated castor oil and ethanolamine are added to the reactor and heated in an oil bath at 115-125℃ for 4-6 hours. After the reaction is completed, the mixture is cooled to room temperature, distilled under reduced pressure, and solidified to obtain intermediate 1. Step 2: Under nitrogen protection, add intermediate 1, dibutyltin dilaurate catalyst, to toluene solvent, stir to dissolve, heat to 105-110℃, azeotropically remove water for 30-60 min, then cool to 80-90℃, add methyltrimethoxysilane dropwise, after the addition is complete, reflux at 105-110℃ for 4-6 h, after the reaction is complete, wash and dry, distill under reduced pressure, and purify to obtain modified hydrogenated castor oil.

[0006] In the above steps, hydrogenated castor oil and ethanolamine undergo an aminolysis reaction under heating conditions. The primary amino group of ethanolamine nucleophilically attacks the carbonyl carbon of the ester bond, causing the ester bond to break and generate an amide bond, yielding intermediate 1 with an amide group and a hydroxyl group. Subsequently, the hydroxyl group on intermediate 1 and the methoxy group on methyltrimethoxysilane undergo a dealcolytic condensation reaction under the action of dibutyltin dilaurate catalyst to obtain modified hydrogenated castor oil.

[0007] Furthermore, in step one, the ratio of hydrogenated castor oil to ethanolamine is 10-10.5g:2-2.15g.

[0008] Furthermore, in step two, the ratio of toluene, intermediate 1, dibutyltin dilaurate catalyst, and methyltrimethoxysilane is 50-60 mL: 5-5.1 g: 0.03-0.04 g: 2.5-2.6 g.

[0009] Furthermore, in step (2), the flame retardant is prepared by the following method: S1: Add vanillin to deionized water, heat to 80-90℃ and stir to dissolve. Then slowly add sodium persulfate and ferrous sulfate heptahydrate to the reaction system and maintain the reaction at 80-90℃ for 1-2 hours. After the reaction is complete, filter, wash and dry to obtain intermediate 2. S2: Under nitrogen protection, intermediate 2 and octadecylamine are added to ethanol solvent, mixed evenly, and reacted at 60-80℃ for 12-16h. After the reaction is completed, the solvent is removed by rotary evaporation and dried to obtain intermediate 3. S3: Under nitrogen protection, intermediate 3 is added to toluene solvent and stirred. Then, diethyl phosphite is added dropwise and the mixture is refluxed at 100-120℃ for 10-12 h. After the reaction is completed, the mixture is cooled to room temperature, filtered, washed and dried to obtain the flame retardant.

[0010] Further, in step S1, the ratio of deionized water, vanillin, sodium persulfate, and ferrous sulfate heptahydrate is 150-160mL: 2.4-2.5g: 2-2.1g: 0.08-0.09g.

[0011] Furthermore, in step S2, the ratio of ethanol, intermediate 2, and octadecylamine is 50-60 mL: 2.5-2.6 g: 5.2-5.3 g.

[0012] Furthermore, in step S3, the ratio of toluene, intermediate 3, and diethyl phosphite is 70-80 mL: 3.8-3.9 g: 1.5-1.6 g.

[0013] Furthermore, the foaming agent is composed of sodium bicarbonate and citric acid, with a molar ratio of 2.8-3.2:1.

[0014] The present invention also protects a biodegradable waterproof foam packaging box, which is prepared by any of the preparation methods described above.

[0015] Beneficial technical effects Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Hydrogenated castor oil is modified by grafting siloxane groups onto its molecular chain to enhance its interfacial bonding with polylactic acid matrix. The long-chain alkyl groups in hydrogenated castor oil will physically entangle with the long carbon chains in the flame retardant, enhancing the mechanical properties of the foam packaging box. The long chain can also work synergistically with the siloxane groups to construct a composite hydrophobic network with low surface energy, improving the waterproof performance of the foam packaging box. An intermediate 2 with a rigid aromatic ring structure is synthesized from vanillin to provide thermal stability and a char skeleton. Subsequently, it reacts with octadecylamine and diethyl phosphite to obtain a complete phosphorus-nitrogen synergistic flame retardant structure. The char layer promoted by this structure during combustion can work synergistically with the silicon element in the siloxane groups to form a stable silicon-carbon protective layer, which isolates heat and oxygen, thus improving the flame retardant performance of the foam packaging box. Moreover, the base material and raw materials used are all environmentally friendly and do not contain heavy metals or persistent organic pollutants that are difficult to degrade, ensuring the overall biodegradability of the foam packaging box and conforming to the direction of green development.

[0016] (2) The biodegradable waterproof foam packaging box of the present invention is obtained by the preparation method of the present invention and has all the beneficial effects of the preparation method of the present invention. Attached Figure Description

[0017] Figure 1 It is the synthesis reaction formula for flame retardants. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0019] To better understand the above technical solutions, the following will provide a detailed description of the technical solutions in conjunction with the accompanying drawings and specific embodiments.

[0020] The reagents used in the following specific embodiments are of analytical grade. Additionally: Polylactic acid: purity 95%, molecular weight 50,000, purchased from Guangzhou Weihua Biotechnology Co., Ltd. Maleic anhydride-grafted polylactic acid: purchased from Dongguan Zhangmutou Hengtai Plastic Raw Material Business Department, model PLA-121701; Epoxy chain extender: selected from BASF, Germany, model ADR4032D.

[0021] Example 1 This embodiment provides a biodegradable waterproof foam packaging box, the preparation method of which specifically includes the following steps: (1) Under nitrogen protection, 10g of hydrogenated castor oil and 2g of ethanolamine were added to the reactor and heated in an oil bath at 115°C for 4 hours. After the reaction was completed, the mixture was cooled to room temperature, distilled under reduced pressure, and solidified to obtain intermediate 1. (2) Under nitrogen protection, 5g of intermediate 1 and 0.03g of dibutyltin dilaurate catalyst were added to 50mL of toluene solvent, stirred and dissolved, heated to 105℃, azeotropically removed water for 30min, and then cooled to 80℃. 2.5g of methyltrimethoxysilane was added dropwise. After the addition was complete, the mixture was refluxed at 105℃ for 4h. After the reaction was completed, the mixture was washed and dried, and purified by vacuum distillation to obtain modified hydrogenated castor oil. (3) Add 2.4g of vanillin to 150mL of deionized water, heat to 80℃ and stir to dissolve. Then slowly add 2g of sodium persulfate and 0.08g of ferrous sulfate heptahydrate to the reaction system and keep the reaction at 80℃ for 1h. After the reaction is completed, filter, wash and dry to obtain intermediate 2. (4) Under nitrogen protection, 2.5g of intermediate 2 and 5.2g of octadecylamine were added to 50mL of ethanol solvent, mixed evenly, and reacted at 60℃ for 12h. After the reaction was completed, the solvent was removed by rotary evaporation and dried to obtain intermediate 3. (5) Under nitrogen protection, 3.8 g of intermediate 3 was added to 70 mL of toluene solvent and stirred. Then, 1.5 g of diethyl phosphite was added dropwise, and the mixture was refluxed at 100 °C for 10 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed, and dried to obtain the flame retardant, as shown below. Figure 1 As shown; (6) Dry 90 parts by weight of polylactic acid at 50°C for 6 hours and pass it through a 180-mesh sieve. Dry 3 parts by weight of modified hydrogenated castor oil, 8 parts by weight of flame retardant, 5 parts by weight of maleic anhydride-grafted polylactic acid, 0.3 parts by weight of epoxy chain extender, and 1 part by weight of Span 60 at 80°C for 6 hours. Dry 8 parts by weight of foaming agent at 60°C for 4 hours. Then add them together to a high-speed mixer and mix at 30°C for 5 minutes to obtain a mixture. (7) Place the mixture into a mold preheated to 130°C, apply a pressure of 3MPa, and quickly raise the mold temperature to 170°C. Hold the temperature for 2 minutes, then quickly release the pressure and open the mold. Hold the pressure at 50°C and cool for 5 minutes. Demold the mold to obtain a biodegradable waterproof foam packaging box.

[0022] The foaming agent is composed of sodium bicarbonate and citric acid in a molar ratio of 2.8:1.

[0023] Example 2 This embodiment provides a biodegradable waterproof foam packaging box, the preparation method of which specifically includes the following steps: (1) Under nitrogen protection, 10.5g of hydrogenated castor oil and 2.15g of ethanolamine were added to the reactor and heated in an oil bath at 125°C for 6 hours. After the reaction was completed, the mixture was cooled to room temperature, distilled under reduced pressure, and solidified to obtain intermediate 1. (2) Under nitrogen protection, 5.1 g of intermediate 1 and 0.04 g of dibutyltin dilaurate catalyst were added to 60 mL of toluene solvent, stirred and dissolved, heated to 110 °C, azeotropically removed water for 60 min, and then cooled to 90 °C. 2.6 g of methyltrimethoxysilane was added dropwise. After the addition was complete, the mixture was refluxed at 110 °C for 6 h. After the reaction was completed, the mixture was washed and dried, and purified by vacuum distillation to obtain modified hydrogenated castor oil. (3) Add 2.5g of vanillin to 160mL of deionized water, heat to 90℃ and stir to dissolve. Then slowly add 2.1g of sodium persulfate and 0.09g of ferrous sulfate heptahydrate to the reaction system and keep the reaction at 90℃ for 2h. After the reaction is completed, filter, wash and dry to obtain intermediate 2. (4) Under nitrogen protection, 2.6 g of intermediate 2 and 5.3 g of octadecylamine were added to 60 mL of ethanol solvent, mixed evenly, and reacted at 80 °C for 16 h. After the reaction was completed, the solvent was removed by rotary evaporation and dried to obtain intermediate 3. (5) Under nitrogen protection, 3.9 g of intermediate 3 was added to 80 mL of toluene solvent and stirred. Then, 1.6 g of diethyl phosphite was added dropwise and the mixture was refluxed at 120 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed and dried to obtain the flame retardant. (6) Dry 100 parts by weight of polylactic acid at 60°C for 8 hours and pass it through a 200-mesh sieve. Dry 5 parts by weight of modified hydrogenated castor oil, 10 parts by weight of flame retardant, 8 parts by weight of maleic anhydride-grafted polylactic acid, 0.5 parts by weight of epoxy chain extender, and 1.5 parts by weight of Span 60 at 90°C for 8 hours. Dry 12 parts by weight of foaming agent at 70°C for 6 hours. Then add them together to a high-speed mixer and mix at 40°C for 10 minutes to obtain a mixture. (7) Place the mixture into a mold preheated to 140°C, apply a pressure of 5MPa, and quickly raise the mold temperature to 175°C. Keep it warm for 4 minutes, then quickly release the pressure and open the mold. Keep it under pressure at 60°C for 7 minutes and demold to obtain a biodegradable waterproof foam packaging box.

[0024] The foaming agent is composed of sodium bicarbonate and citric acid in a molar ratio of 3.2:1.

[0025] Example 3 This embodiment provides a biodegradable waterproof foam packaging box, the preparation method of which specifically includes the following steps: (1) Under nitrogen protection, 10.25g of hydrogenated castor oil and 2.07g of ethanolamine were added to the reactor. The mixture was heated in an oil bath at 120°C for 5 hours. After the reaction was completed, the mixture was cooled to room temperature, distilled under reduced pressure, and solidified to obtain intermediate 1. (2) Under nitrogen protection, 5.05 g of intermediate 1 and 0.03 g of dibutyltin dilaurate catalyst were added to 55 mL of toluene solvent, stirred and dissolved, heated to 108 °C, azeotropically removed water for 45 min, and then cooled to 85 °C. 2.55 g of methyltrimethoxysilane was added dropwise. After the addition was complete, the mixture was refluxed at 108 °C for 5 h. After the reaction was completed, the mixture was washed and dried, and purified by vacuum distillation to obtain modified hydrogenated castor oil. (3) Add 2.45g of vanillin to 155mL of deionized water, heat to 85℃ and stir to dissolve. Then slowly add 2.05g of sodium persulfate and 0.08g of ferrous sulfate heptahydrate to the reaction system and keep the reaction at 85℃ for 1.5h. After the reaction is completed, filter, wash and dry to obtain intermediate 2. (4) Under nitrogen protection, 2.55 g of intermediate 2 and 5.25 g of octadecylamine were added to 55 mL of ethanol solvent, mixed evenly, and reacted at 70 °C for 14 h. After the reaction was completed, the solvent was removed by rotary evaporation and dried to obtain intermediate 3. (5) Under nitrogen protection, 3.85 g of intermediate 3 was added to 75 mL of toluene solvent and stirred. Then, 1.55 g of diethyl phosphite was added dropwise and the mixture was refluxed at 110 °C for 11 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed and dried to obtain the flame retardant. (6) Dry 95 parts by weight of polylactic acid at 55°C for 7 hours and pass it through a 190-mesh sieve. Dry 4 parts by weight of modified hydrogenated castor oil, 9 parts by weight of flame retardant, 6 parts by weight of maleic anhydride-grafted polylactic acid, 0.4 parts by weight of epoxy chain extender, and 1.2 parts by weight of Span 60 at 85°C for 7 hours. Dry 10 parts by weight of foaming agent at 65°C for 5 hours. Then add them together to a high-speed mixer and mix at 35°C for 8 minutes to obtain a mixture. (7) Place the mixture into a mold preheated to 135°C, apply a pressure of 4MPa, and quickly raise the mold temperature to 172°C. Hold the temperature for 3 minutes, then quickly release the pressure and open the mold. Hold the pressure at 55°C and cool for 6 minutes. Demold the mold to obtain a biodegradable waterproof foam packaging box.

[0026] The foaming agent is composed of sodium bicarbonate and citric acid in a molar ratio of 3:1.

[0027] Example 4 This embodiment provides a biodegradable waterproof foam packaging box, the preparation method of which specifically includes the following steps: (1) Under nitrogen protection, 10.2 g of hydrogenated castor oil and 2.05 g of ethanolamine were added to the reactor and heated in an oil bath at 118 °C for 4 h. After the reaction was completed, the mixture was cooled to room temperature, distilled under reduced pressure, and solidified to obtain intermediate 1. (2) Under nitrogen protection, 5.02 g of intermediate 1 and 0.03 g of dibutyltin dilaurate catalyst were added to 52 mL of toluene solvent, stirred and dissolved, heated to 106 °C, azeotropically removed water for 40 min, and then cooled to 82 °C. 2.52 g of methyltrimethoxysilane was added dropwise. After the addition was complete, the mixture was refluxed at 106 °C for 4 h. After the reaction was completed, the mixture was washed and dried, and purified by vacuum distillation to obtain modified hydrogenated castor oil. (3) Add 2.42 g of vanillin to 152 mL of deionized water, heat to 82 °C and stir to dissolve. Then slowly add 2.02 g of sodium persulfate and 0.08 g of ferrous sulfate heptahydrate to the reaction system and keep the reaction at 82 °C for 1 h. After the reaction is completed, filter, wash and dry to obtain intermediate 2. (4) Under nitrogen protection, 2.52 g of intermediate 2 and 5.22 g of octadecylamine were added to 52 mL of ethanol solvent, mixed evenly, and reacted at 65 °C for 13 h. After the reaction was completed, the solvent was removed by rotary evaporation and dried to obtain intermediate 3. (5) Under nitrogen protection, 3.82 g of intermediate 3 was added to 72 mL of toluene solvent and stirred. Then, 1.52 g of diethyl phosphite was added dropwise and the mixture was refluxed at 105 °C for 10 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed and dried to obtain the flame retardant. (6) Dry 92 parts by weight of polylactic acid at 52°C for 6 hours and pass it through a 180-mesh sieve. Dry 3 parts by weight of modified hydrogenated castor oil, 8 parts by weight of flame retardant, 6 parts by weight of maleic anhydride-grafted polylactic acid, 0.3 parts by weight of epoxy chain extender, and 1 part by weight of Span 60 at 82°C for 6 hours. Dry 9 parts by weight of foaming agent at 62°C for 4 hours. Then add them together to a high-speed mixer and mix at 32°C for 6 minutes to obtain a mixture. (7) Place the mixture into a mold preheated to 132°C, apply a pressure of 3MPa, and quickly raise the mold temperature to 170°C. Hold the temperature for 2 minutes, then quickly release the pressure and open the mold. Hold the pressure at 52°C and cool for 5 minutes. Demold the mold to obtain a biodegradable waterproof foam packaging box.

[0028] The foaming agent is composed of sodium bicarbonate and citric acid in a molar ratio of 2.9:1.

[0029] Example 5 This embodiment provides a biodegradable waterproof foam packaging box, the preparation method of which specifically includes the following steps: (1) Under nitrogen protection, 10.4 g of hydrogenated castor oil and 2.1 g of ethanolamine were added to the reactor and heated in an oil bath at 122 °C for 6 h. After the reaction was completed, the mixture was cooled to room temperature, distilled under reduced pressure, and solidified to obtain intermediate 1. (2) Under nitrogen protection, 5.08 g of intermediate 1 and 0.04 g of dibutyltin dilaurate catalyst were added to 58 mL of toluene solvent, stirred and dissolved, heated to 108 °C, azeotropically removed water for 50 min, and then cooled to 88 °C. 2.58 g of methyltrimethoxysilane was added dropwise. After the addition was complete, the mixture was refluxed at 110 °C for 6 h. After the reaction was completed, the mixture was washed and dried, and purified by vacuum distillation to obtain modified hydrogenated castor oil. (3) Add 2.48 g of vanillin to 158 mL of deionized water, heat to 88 °C and stir to dissolve. Then slowly add 2.08 g of sodium persulfate and 0.09 g of ferrous sulfate heptahydrate to the reaction system and keep the reaction at 88 °C for 2 h. After the reaction is completed, filter, wash and dry to obtain intermediate 2. (4) Under nitrogen protection, 2.58 g of intermediate 2 and 5.28 g of octadecylamine were added to 58 mL of ethanol solvent, mixed evenly, and reacted at 75 °C for 15 h. After the reaction was completed, the solvent was removed by rotary evaporation and dried to obtain intermediate 3. (5) Under nitrogen protection, 3.88 g of intermediate 3 was added to 78 mL of toluene solvent and stirred. Then, 1.58 g of diethyl phosphite was added dropwise and the mixture was refluxed at 115 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed and dried to obtain the flame retardant. (6) Dry 98 parts by weight of polylactic acid at 58°C for 8 hours and pass it through a 200-mesh sieve. Dry 5 parts by weight of modified hydrogenated castor oil, 10 parts by weight of flame retardant, 7 parts by weight of maleic anhydride-grafted polylactic acid, 0.5 parts by weight of epoxy chain extender, and 1.5 parts by weight of Span 60 at 88°C for 8 hours. Dry 11 parts by weight of foaming agent at 68°C for 6 hours. Then add them together to a high-speed mixer and mix at 38°C for 9 minutes to obtain a mixture. (7) Place the mixture into a mold preheated to 140°C, apply a pressure of 5MPa, and quickly raise the mold temperature to 175°C. Hold the temperature for 4 minutes, then quickly release the pressure and open the mold. Hold the pressure at 58°C and cool for 7 minutes. Demold the mold to obtain a biodegradable waterproof foam packaging box.

[0030] The foaming agent is composed of sodium bicarbonate and citric acid in a molar ratio of 3.1:1.

[0031] Comparative Example 1 The main difference between this comparative example and Example 5 is that intermediate 1 is used instead of modified hydrogenated castor oil.

[0032] Comparative Example 2 The main difference between this comparative example and Example 5 is that intermediate 3 is used instead of the flame retardant.

[0033] Performance testing (1) Mechanical property testing: The biodegradable waterproof foam packaging boxes prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to mechanical property testing. The compressive strength was tested according to standard GB / T8813-2020, and the tensile strength and elongation at break were tested according to standard GB / T9641-1988. The test results are shown in Table 1.

[0034] Table 1: Mechanical Performance Tests project Compressive strength (kPa) Tensile strength (kPa) Elongation at break (%) Example 1 172 257 30 Example 2 175 260 33 Example 3 174 258 31 Example 4 173 258 31 Example 5 175 259 32 Comparative Example 1 159 233 26 Comparative Example 2 164 242 28 As can be seen from Table 1, the biodegradable waterproof foam packaging boxes prepared in Examples 1-5 have good mechanical properties.

[0035] (2) Flame retardant performance test: The biodegradable waterproof foam packaging boxes prepared in Examples 1-5 and Comparative Examples 1-2 were cut into 120mm×10mm×10mm samples, and the oxygen index of the samples was tested according to standard GB / T2406.2-2009. The test results are shown in Table 2.

[0036] Table 2: Flame retardant performance test project Oxygen index (%) Example 1 32.4 Example 2 32.8 Example 3 32.5 Example 4 32.5 Example 5 32.7 Comparative Example 1 29.4 Comparative Example 2 28.1 As can be seen from Table 2, the biodegradable waterproof foam packaging boxes prepared in Examples 1-5 have good flame retardant properties.

[0037] (3) Waterproof performance test: The waterproof performance of the biodegradable waterproof foam packaging boxes prepared in Examples 1-5 and Comparative Examples 1-2 was evaluated with reference to standard GB / T30693-2014. The larger the water contact angle, the better the waterproof performance. The test results are shown in Table 3.

[0038] Table 3: Waterproofing Performance Test project Water contact angle (°) Example 1 120.48 Example 2 123.64 Example 3 121.92 Example 4 121.30 Example 5 123.27 Comparative Example 1 109.24 Comparative Example 2 116.38 As can be seen from Table 3, the biodegradable waterproof foam packaging boxes prepared in Examples 1-5 have good waterproof performance.

[0039] The comparison shows that Comparative Example 1, due to the use of unmodified intermediate 1, lacks the siloxane groups and hydrophobic components that enhance interfacial bonding, resulting in lower mechanical properties, flame retardant properties, and waterproof properties compared to the Example. Comparative Example 2 uses intermediate 3 instead of flame retardant, and the lack of phosphorus in its molecular structure leads to a significant decrease in flame retardant efficiency. The Schiff base structure of intermediate 3 has poor polarity matching with the polylactic acid matrix, affecting its interfacial bonding ability in the polylactic acid matrix, resulting in decreased mechanical and waterproof properties. However, since it still retains the siloxane groups and hydrophobic long chains, its mechanical and waterproof properties are between those of the Example and Comparative Example 1.

[0040] It should be noted that, in this document, 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 limitation, 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.

[0041] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0042] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing a biodegradable waterproof foam packaging box, characterized in that, Includes the following steps: (1) Preparation of modified hydrogenated castor oil; (2) Preparation of flame retardants; (3) Dry 90-100 parts by weight of polylactic acid at 50-60℃ for 6-8h, pass through a 180-200 mesh sieve, dry 3-5 parts by weight of modified hydrogenated castor oil, 8-10 parts by weight of flame retardant, 5-8 parts by weight of maleic anhydride grafted polylactic acid, 0.3-0.5 parts by weight of epoxy chain extender, and 1-1.5 parts by weight of Span 60 at 80-90℃ for 6-8h, dry 8-12 parts by weight of foaming agent at 60-70℃ for 4-6h, and then add them together to a high-speed mixer and mix at 30-40℃ for 5-10min to obtain a mixture. (4) Place the mixture into a mold preheated to 130-140℃, apply a pressure of 3-5MPa, and quickly raise the mold temperature to 170-175℃. Keep it warm for 2-4 minutes, then quickly release the pressure and open the mold. Keep it under pressure and cool for 5-7 minutes at 50-60℃. Demold the mold to obtain a biodegradable waterproof foam packaging box.

2. The method for preparing the biodegradable waterproof foam packaging box according to claim 1, characterized in that, In step (1), the method for preparing modified hydrogenated castor oil is as follows: Step 1: Under nitrogen protection, hydrogenated castor oil and ethanolamine are added to the reactor and heated in an oil bath at 115-125℃ for 4-6 hours. After the reaction is completed, the mixture is cooled to room temperature, distilled under reduced pressure, and solidified to obtain intermediate 1. Step 2: Under nitrogen protection, add intermediate 1, dibutyltin dilaurate catalyst, to toluene solvent, stir to dissolve, heat to 105-110℃, azeotropically remove water for 30-60 min, then cool to 80-90℃, add methyltrimethoxysilane dropwise, after the addition is complete, reflux at 105-110℃ for 4-6 h, after the reaction is complete, wash and dry, distill under reduced pressure, and purify to obtain modified hydrogenated castor oil.

3. The method for preparing the biodegradable waterproof foam packaging box according to claim 2, characterized in that, In step one, the ratio of hydrogenated castor oil to ethanolamine is 10-10.5g: 2-2.15g.

4. The method for preparing the biodegradable waterproof foam packaging box according to claim 2, characterized in that, In step two, the ratio of toluene, intermediate 1, dibutyltin dilaurate catalyst, and methyltrimethoxysilane is 50-60 mL: 5-5.1 g: 0.03-0.04 g: 2.5-2.6 g.

5. The method for preparing the biodegradable waterproof foam packaging box according to claim 1, characterized in that, In step (2), the flame retardant is prepared by the following method: S1: Add vanillin to deionized water, heat to 80-90℃ and stir to dissolve. Then slowly add sodium persulfate and ferrous sulfate heptahydrate to the reaction system and maintain the reaction at 80-90℃ for 1-2 hours. After the reaction is complete, filter, wash and dry to obtain intermediate 2. S2: Under nitrogen protection, intermediate 2 and octadecylamine are added to ethanol solvent, mixed evenly, and reacted at 60-80℃ for 12-16h. After the reaction is completed, the solvent is removed by rotary evaporation and dried to obtain intermediate 3. S3: Under nitrogen protection, intermediate 3 is added to toluene solvent and stirred. Then, diethyl phosphite is added dropwise and the mixture is refluxed at 100-120℃ for 10-12 h. After the reaction is completed, the mixture is cooled to room temperature, filtered, washed and dried to obtain the flame retardant.

6. The method for preparing the biodegradable waterproof foam packaging box according to claim 5, characterized in that, In step S1, the ratio of deionized water, vanillin, sodium persulfate, and ferrous sulfate heptahydrate is 150-160 mL: 2.4-2.5 g: 2-2.1 g: 0.08-0.09 g.

7. The method for preparing the biodegradable waterproof foam packaging box according to claim 5, characterized in that, In step S2, the ratio of ethanol, intermediate 2, and octadecylamine is 50-60 mL: 2.5-2.6 g: 5.2-5.3 g.

8. The method for preparing the biodegradable waterproof foam packaging box according to claim 5, characterized in that, In step S3, the ratio of toluene, intermediate 3, and diethyl phosphite is 70-80 mL: 3.8-3.9 g: 1.5-1.6 g.

9. The method for preparing the biodegradable waterproof foam packaging box according to claim 1, characterized in that, The foaming agent is composed of sodium bicarbonate and citric acid, with a molar ratio of 2.8-3.2:

1.

10. A biodegradable waterproof foam packaging box, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

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