Biodegradable macromolecular cushioning packaging material and preparation method thereof

Abstract

The invention discloses a biodegradable macromolecular cushioning packaging material and a preparation method thereof. The biodegradable macromolecular cushioning packaging material is prepared from the following components in percentage by mass: 40 to 60 percent of biodegradable macromolecular compound, 5 to 15 percent of anti-freezing modifier, 8 to 20 percent of nanoscale elastic particle, 3 to 8 percent of composite pore-forming agent and the balance of functional additive, the biodegradable polymer compound is prepared by compounding polylactic acid and poly (adipic acid) / butylene terephthalate according to a mass ratio of (40-60): (40-60); the nano-scale elastic particles are nano rubber particles or nano polyurethane particles of which the surfaces are grafted with maleic anhydride, and the particle size is 50-200nm; the composite pore-forming agent is prepared by compounding sodium bicarbonate and citric acid in a mass ratio of (2-3): 1. Through the synergistic effect of the anti-freezing modifier and the nanoscale elastic particles, the material can keep stable flexibility at different environment temperatures, and the problem of low-temperature embrittlement of a traditional PLA material is solved; when the buffering material is pressed, external force and energy can be effectively dispersed, and the buffering material plays a key role in damping and buffering in the transportation of fresh high-value agricultural products.

Description

Technical Field

[0001] This invention relates to the field of polymer shock-absorbing packaging technology, and in particular to a biodegradable polymer shock-absorbing packaging material and its preparation method. Background Technology

[0002] With the rapid expansion of global cold chain logistics and e-commerce delivery, packaging materials need to meet three core requirements simultaneously. For example, the loss rate of cold chain fresh food transportation needs to be controlled below 10%, and traditional packaging can no longer adapt to multi-stage transfer and complex environmental temperature changes. In addition, traditional non-degradable plastics (EPS, EPE) are facing elimination due to their long degradation cycle of 200-500 years. This forces producers to balance the performance stability and preparation efficiency of express delivery materials in large-scale production. Existing biodegradable material preparation processes generally suffer from high energy consumption, low yield, and high cost, making it difficult to meet the packaging supply needs of e-commerce. Currently, the mainstream biodegradable cushioning materials on the market are mainly divided into two categories: natural polymer-based and synthetic polymer-based. Both have significant performance shortcomings and cannot simultaneously achieve both temperature resistance and biodegradability. Among them, the tensile strength of natural polymer-based starch-based materials is generally ≤5MPa, the elongation at break is ≤50%, and they are prone to brittleness at low temperatures (≤-5℃). After a 1.5m drop test, the damage reduction rate of glassware is less than 12%. On the other hand, the cushioning performance of cellulose-based materials decreases by more than 60% after absorbing moisture. In the humid environment of e-commerce delivery or the condensation scenario of cold chain, the structure softens within 24 hours and cannot protect the internal items.

[0003] Synthetic polymer-based materials are rigid but lack toughness. Their elongation at break is only 10%-15% at room temperature, and they undergo glass transition at -10℃, making them unable to withstand transportation impacts. Single PBAT materials have excellent toughness but poor rigidity. They are prone to softening and deformation above 40℃, and their compression rebound rate after stacking is only 50%, making them unsuitable for the stacking scenarios in express delivery warehouses. Therefore, developing a biodegradable polymer shock-absorbing packaging material with satisfactory performance, stable process, and controllable cost, as well as its preparation method, is an urgent industry need and has significant application value for cold chain logistics and e-commerce delivery packaging. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the prior art by proposing a biodegradable polymeric shock-absorbing packaging material and its preparation method. To achieve the above objectives, the present invention adopts the following technical solution: This invention comprises the following components by weight percentage: 40%-60% biodegradable polymer compound, 5%-15% antifreeze modifier, 8%-20% nano-sized elastic particles, 3%-8% composite pore-forming agent, and the remainder being functional additives; the biodegradable polymer compound is a mixture of polylactic acid and poly(adipate) / butyl terephthalate in a weight ratio of 40-60:40-60; the nano-sized elastic particles are surface-grafted maleic anhydride nano-rubber particles or nano-polyurethane particles with a particle size of 50-200 nm; the composite pore-forming agent is a mixture of sodium bicarbonate and citric acid in a weight ratio of 2-3:1.

[0005] Furthermore, the antifreeze modifier is a compound of propylene glycol and glycerin in a mass ratio of 1-2:1; the functional additives include 0.5%-2% antioxidant and 0.3%-1% dispersant by mass, wherein the antioxidant is a hindered phenolic antioxidant and the dispersant is zinc stearate.

[0006] Furthermore, the surface grafting rate of the nano-scale elastic particles is 3%-8%, and they are pretreated with a silane coupling agent, the amount of which is 1%-3% of the mass of the nano-scale elastic particles during the pretreatment process. A type of express delivery cushioning granule is produced by extrusion granulation of the aforementioned biodegradable polymer shock-absorbing packaging material. The granules have an irregular polyhedral structure and a particle size of 5-15 mm. Furthermore, the particles are provided with interconnected micropore channels with a diameter of 0.1-0.5 mm, and the micropore channels occupy 15%-30% of the particle volume.

[0007] Compared with the prior art, the beneficial effects of this invention are as follows: This invention utilizes the synergistic effect of antifreeze modifiers and nano-scale elastic particles to enable the material to maintain stable flexibility under different environmental temperatures, thus solving the problem of low-temperature embrittlement of traditional PLA materials. It also improves energy dissipation efficiency, allowing the buffer material to effectively disperse external forces and energy when under pressure, providing shock absorption and cushioning during the transportation of fruits and vegetables. Attached Figure Description

[0008] Figure 1 This is a flowchart of a method for preparing a biodegradable polymer shock-absorbing packaging material according to the present invention. Detailed Implementation

[0009] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Example 1

[0010] A buffer filling granule suitable for packaging small, easily damaged products (such as bayberries and cherries) was prepared. The composition consists of a biodegradable polymer compound: 60% polylactic acid (PLA), 30% polybutylene adipate (PBAT), 30% PBAT, 5% antifreeze modifier, 2.5% propylene glycol (1:1 ratio), 2.5% glycerol, and 8% nano-sized elastic particles. The nano-rubber particles grafted with maleic anhydride have a grafting rate of 3.5% and are pretreated with silane coupling agent KH-550 (added at 1% of the nanoparticle mass). The particle size distribution is mainly in the range of 50-100 nm. The composite pore-forming agent is 3%, sodium bicarbonate is 2% (compound ratio 2:1), citric acid is 1%, functional additives are 24%, antioxidant 1010 (hindered phenol) is 0.5%, dispersant (zinc stearate) is 0.3%, and filler (calcium carbonate) is 23.2%.

[0011] First, the nano-rubber particles and silane coupling agent are pretreated in a high-speed mixer at 80°C for 10 minutes. All components are then added to the high-speed mixer and mixed thoroughly. The mixture is then melt-blended, foamed, and extruded into strips using a twin-screw extruder. The process temperature range is 150-175°C. After cooling in a water-cooling tank, the strips are cut into 5-10mm irregular polyhedral particles using a pelletizer. The particles are then treated in 80°C hot air for 15 minutes, where citric acid and sodium bicarbonate further react, forming partially interconnected microporous channels through gas expansion. Expected product performance includes: high particle density, moderate cushioning performance, basic low-temperature brittleness resistance, significant cost advantage, and a cell density just exceeding 5×10⁻⁶. 5 The number of micropores per cm³ is approximately 15%. Example 2

[0012] A general-purpose, high-performance buffer-filling particle was prepared. The composition consisted of a biodegradable polymer compound: 50% polylactic acid (PLA), 20% (PLA accounts for 40% of the compound), 30% polybutylene adipate / terephthalate (PBAT) (PBAT accounts for 60% of the compound), 10% antifreeze modifier, 6.7% propylene glycol (compound ratio 2:1), 3.3% glycerol, and 15% nano-sized elastic particles. Maleic anhydride-grafted nano-polyurethane elastic particles were selected. The nanoparticles, with a grafting rate of 5.5%, are pretreated with silane coupling agent KH-570 (added at 2% of the nanoparticle mass). The particle size distribution is mainly in the range of 100-150 nm. The composite pore-forming agent is 5.5%, sodium bicarbonate is 3.8% (compound ratio 2.5:1, approximately equal to), citric acid is 1.7%, functional additives are 19.5%, antioxidant 1076 (hindered phenol) is 1.2%, dispersant (zinc stearate) is 0.8%, and processing aids (epoxy compatibilizers) are 17.5%.

[0013] The pretreatment and mixing processes are the same as in Example 1. The twin-screw extrusion process temperature range is 160-170℃. By precisely controlling the die head pressure, the foaming process is made more stable. After pelleting, irregular polyhedral particles of 8-12mm are obtained. These particles are then treated in a 90℃ saturated steam environment for 10 minutes. The heat and moisture promote the complete reaction of the pore-forming agent and form excellent interconnected microporous channels. Expected product performance: moderate particle density, high resilience and energy absorption efficiency, excellent low-temperature performance, uniform and fine cell structure, and a cell density of up to 1×10⁻⁶. 6 The number of micropores per cm³ is approximately 22%. Example 3

[0014] Preparation of filler particles with top-level cushioning and protective performance. Components and proportions (mass percentage): Biodegradable polymer compound: 40% Polylactic acid (PLA): 24% (i.e., PLA accounts for 60% of the compound), Polybutylene adipate / terephthalate (PBAT): 16% (i.e., PBAT accounts for 40% of the compound), Antifreeze modifier: 15% Propylene glycol: 10% (compound ratio 2:1), Glycerol: 5%, Nanoscale elastic particles: 20%, Surface bonding... The nano-rubber particles with maleic anhydride grafting rate of 8% were pretreated with silane coupling agent KH-550 (added at 3% of the nanoparticle mass). The particle size distribution was mainly 150-200nm. The composite pore-forming agent was 8%, sodium bicarbonate was 5.7% (compound ratio 3:1), citric acid was 2.3%, functional additives were 17%, antioxidant 1010 / 1076 complex was 2%, dispersant (zinc stearate) was 1%, and lubricant (EBS) was 14%.

[0015] During the preparation process, such as Figure 1 As shown, the twin-screw extruder process requires stronger shearing and more precise temperature control (155-165℃) to prevent high gas volume from causing cell coalescence. After pelleting, larger particles of 10-15mm are obtained with a loose structure. A supercritical CO2-assisted annealing process is used: SC-CO2 is introduced into a high-pressure autoclave to allow citric acid and sodium bicarbonate to fully penetrate and react, forming a highly developed and uniformly interconnected microporous channel network. Expected product performance: extremely low particle density, soft and excellent resilience, superior resistance to repeated impacts, high and very uniform cell density, microporous channel ratio of up to 30%, and the fastest expected degradation rate. It is suitable for fresh high-value agricultural products such as bayberries, kiwis, and pears.

[0016] The filling particles exhibit a compression rebound rate of ≥80% under simulated express delivery stacking environment (stack weight 50kg, lasting 2h). When filled into express delivery packaging boxes, they reduce the loss rate of fragile items inside the boxes by ≥22%. In soil environment, the biodegradability rate is ≥70% within 3 months. The single impact performance comparison test under low temperature conditions determined the drop impact performance of the new material and traditional cushioning materials (such as EPS, EPE) at -5℃ and 23℃ (room temperature), verifying its energy dissipation efficiency and loss reduction potential of more than 20%.

[0017] Experimental Samples: Experimental Group: Cardboard boxes filled with cushioning particles made from the aforementioned third example (high-performance type) (size: 30cm x 30cm x 30cm), with filling amount up to 80% of the box volume; Control Group 1: Cardboard boxes of the same size filled with EPS foam particles (common market size); Control Group 2: Cardboard boxes of the same size filled with EPE (pearl cotton) rolls; Contents: A 5kg simulant (containing a sensor for measuring impact acceleration), simulating cold chain food (such as lychees, high-end ice cream) or biological agents.

[0018] All samples, along with their contents, were pretreated in a -5°C environmental chamber for 24 hours to ensure uniform internal and external temperatures. Using a drop tester, the sample box was dropped from a height of 60cm at a flat angle. The maximum impact acceleration (G-value) during the drop was recorded by a triaxial accelerometer on the contents. The lower the G-value, the more energy the cushioning material absorbed, the smaller the impact transmitted to the contents, and the better the damage reduction effect. The above experiment was repeated at 23°C.

[0019] At -5℃, EPS and EPE become brittle due to the low temperature, and the G value increases significantly (e.g., EPS increases from 80G at room temperature to 130G). The experimental group, containing antifreeze modifiers and nano-elastic particles, remains flexible at low temperatures, and the G value changes very little (e.g., from 75G to 85G). Loss calculation: Based on the G value of the control group EPS at -5℃ (130G), the G value of the experimental group (85G) decreased by about 34.6% ((130-85) / 130*100%), far exceeding the 20% loss reduction target.

[0020] Therefore, the new material can dissipate energy very effectively under low-temperature single impact, significantly reducing the impact force transmitted to the contents, making it perfectly suitable for cold chain scenarios.

[0021] Experiment 2: Simulated random drop test during e-commerce delivery. This experiment simulates multiple, multi-angle collisions experienced during real delivery to verify the durability and continuous protection capabilities of the material.

[0022] The test investigated the degree of cushioning performance degradation of the new material after a series of random drops, comparing it with traditional materials. Experimental samples were the same as in Experiment 1. The experimental method involved pre-treating the samples at -5℃ and using a programmable hexahedral rotary drop tester or robotic arm to perform a series of 10 random drops (at different heights and angles on the bottom, edges, and corners). After the 1st, 5th, and 10th drops, the contents were removed, the sensors were reinstalled, and a standard 50cm bottom drop test was performed, recording the G-value. This was done to monitor the degradation of the material's cushioning performance after varying degrees of wear.

[0023] The results showed that, in the control group (EPS / EPE), after multiple low-temperature impacts, the brittle material experienced permanent crushing, particle pulverization, or foam breakage, leading to a sharp decline in cushioning performance. The G-value measured in each standard test increased with each impact. In the experimental group, the nano-elastic particles provided excellent resilience and fatigue resistance. The pore structure could be repeatedly compressed and rebounded without collapsing. After multiple impacts, the G-value measured in the standard test remained stable or only increased slightly. Loss reduction calculation: Based on the G-value measured after the 10th impact, the G-value of the experimental group was expected to be more than 30% lower than that of the control group at the same time. This proves that the new material can provide continuous and stable protection throughout the entire distribution chain, with significant cumulative loss reduction effect and excellent fatigue resistance. It can effectively cope with the complex multiple impact scenarios of e-commerce distribution, continuously dissipate energy, and avoid product damage due to packaging failure in the later stages of transportation.

[0024] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A biodegradable high molecular cushioning packaging material, characterized by, The granule is composed of the following components in percentage by mass: biodegradable high-molecular compound 40-60%, anti-freezing modifier 5-15%, nano-scale elastic particles 8-20%, composite pore-forming agent 3-8%, and the rest being functional auxiliary agents; the biodegradable high-molecular compound is a compound of polylactic acid and polybutylene adipate / terephthalate at a mass ratio of 40-60:40-60; the nano-scale elastic particles are nano-rubber particles or nano-polyurethane particles with surface grafted maleic anhydride, and have a particle size of 50-200 nm; the composite pore-forming agent is a compound of sodium bicarbonate and citric acid at a mass ratio of 2-3:

1.

2. Biodegradable high molecular cushioning packaging material according to claim 1, characterized in that, The anti-freezing modifier is a compound of propylene glycol and glycerol at a mass ratio of 1-2:1; the functional auxiliary agents include 0.5-2% of antioxidant and 0.3-1% of dispersant by mass percentage, the antioxidant is a hindered phenolic antioxidant, and the dispersant is zinc stearate.

3. The biodegradable high molecular cushioning packaging material according to claim 1, characterized by, The nano-scale elastic particles have a surface grafting rate of 3-8% and are pretreated with a silane coupling agent, and the amount of the silane coupling agent used in the pretreatment process is 1-3% of the mass of the nano-scale elastic particles.

4. A parcel delivery cushioning particle made by extrusion of the biodegradable high molecular shock absorbing packaging material according to any one of claims 1 to 4, characterized in that, The granule has an irregular polyhedral structure and a particle size of 5-15 mm.

5. The express shipping cushioning pellet of claim 4, wherein, The granule has interconnected micropore channels in the interior, the micropore channels have a diameter of 0.1-0.5 mm, and the micropore channels account for 15-30% of the volume of the granule.

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