A biodegradable foam box for cold chain logistics and its preparation method

Abstract

This invention belongs to the technical field of foam box materials, specifically relating to a biodegradable foam box for cold chain applications and its preparation method. The biodegradable foam box for cold chain applications, by weight, comprises 70-90 parts thermoplastic starch granules, 10-30 parts modified polylactic acid granules, 10-20 parts modified bamboo fiber, 2-5 parts maleic anhydride-modified polyester elastomer, 1-3 parts plasticizer, 1-3 parts plastic degradation toughening agent, and 0.5-1 parts nucleating agent; the modified bamboo fiber is bamboo fiber modified with nano-calcium carbonate and cellulose nanocrystal particles. The biodegradable foam box for cold chain applications provided by this invention meets the basic performance requirements of biodegradable materials, possesses good composting degradation capabilities, and is suitable for fresh food delivery, cold chain packaging, and other scenarios.

Description

Technical Field

[0001] This invention belongs to the field of foam box material technology, specifically relating to a biodegradable foam box for cold chain and its preparation method. Background Technology

[0002] In recent years, due to the rapid development of e-commerce, the demand for cold chain logistics has also been increasing. Cold chain logistics refers to the supply chain system in which perishable and easily spoiled products such as food and medicine are kept in a specified low-temperature environment throughout all stages of production, storage, transportation, sales and consumption in order to ensure product quality, reduce losses and prevent pollution.

[0003] To extend insulation time, foam boxes with good thermal insulation properties are one of the packaging materials for cold chain logistics. The traditional foam box material is mainly polystyrene foam. Although it is lightweight and strong, it is difficult to degrade and does not meet the requirements of green environmental protection. Therefore, it is of great significance to replace polystyrene foam with new biodegradable materials.

[0004] Chinese patent CN116102766B discloses an ultralight, highly flame-retardant, biodegradable PLA foam and its preparation process. The preparation includes the following steps: Step S1, compounding RDP, lignin, APP, and silica aerogel to obtain a flame-retardant system; Step S2, mixing PLA, PBAT, the flame-retardant system, and an epoxy chain extender, obtaining a mixed sample after the reaction; Step S3, molding the mixed sample in a molding device to obtain a molded sample; Step S4, supercritically foaming the molded sample in a carbon dioxide atmosphere to obtain a foamed sample; Step S5, cooling and solidifying the foamed sample to obtain ultralight, highly flame-retardant, biodegradable PLA foam. The PLA foam prepared by this invention has low density, low thermal conductivity, good flame retardancy, and is fully biodegradable, making it widely applicable in packaging, insulation, and shock absorption fields such as express delivery packaging, cold chain packaging, vaccine packaging, external wall insulation, and interior decoration; however, this technical solution does not address its compressive strength.

[0005] In my master's thesis (Zhang Yu. Preparation and Performance Study of Gelatin-Based Biodegradable Foam for Cold Chain Transportation Packaging [D] Xi'an University of Technology, 2020), gelatin and starch were used as raw materials for buffer and heat insulation foam materials. A process route for biodegradable gelatin-based biodegradable foam materials was established. The influence and mechanism of the preparation process on the structure, mechanical properties and thermal properties of gelatin-based foam were systematically analyzed. The feasibility of applying gelatin-based foam in cold chain transportation packaging was explored. However, the compressive strength of this technical solution is low and the heat insulation performance is poor. Summary of the Invention

[0006] The present invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial solution. Specifically, the present invention provides a biodegradable foam box for cold chain and a method for preparing the same. The biodegradable foam box for cold chain meets the basic performance requirements of biodegradable materials, has good composting degradation ability, and is suitable for scenarios such as fresh food delivery and cold chain packaging.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution:

[0008] In a first aspect, the present invention provides a biodegradable foam box for cold chain use, comprising, by weight, 70-90 parts of thermoplastic starch granules, 10-30 parts of modified polylactic acid granules, 10-20 parts of modified bamboo fiber, 2-5 parts of maleic anhydride-modified polyester elastomer, 1-3 parts of plasticizer, 1-3 parts of plastic degradation toughening agent, and 0.5-1 parts of nucleating agent; wherein the modified bamboo fiber is bamboo fiber modified with nano-calcium carbonate and cellulose nanocrystal particles.

[0009] The thermoplastic starch granules described in this invention are also called "unstructured starch". They are made by disordering the starch structure through a certain method to make it thermoplastic. They are commercially available products and can be sourced from Suzhou Kening Polyol Co., Ltd. or Suzhou Minghua Sugar Alcohol Co., Ltd.

[0010] Optionally, the mass fraction of the thermoplastic starch granules can be any one value or a range of any two values ​​from 70 parts, 75 parts, 80 parts, 85 parts, and 90 parts.

[0011] Preferably, the modified polylactic acid particles are Bio-plus 301p from Guangzhou Bijia Materials Technology Co., Ltd.

[0012] Optionally, the mass fraction of the modified polylactic acid particles can be any one value or a range of any two values ​​from 10 parts, 15 parts, 20 parts, 25 parts, and 30 parts.

[0013] Preferably, the method for preparing the modified bamboo fiber includes the following steps: bamboo fiber is subjected to alkali treatment to obtain pretreated bamboo fiber; nano-calcium carbonate and cellulose nanocrystal particles are dispersed in an ethanol aqueous solution, and a silane coupling agent is added to obtain a suspension; the pretreated bamboo fiber is added to the suspension for impregnation, and then dried to obtain modified bamboo fiber.

[0014] Preferably, the bamboo fiber has a mesh count of 100-150.

[0015] Optionally, the mesh count of the bamboo fiber can be any single value or a range of any two values ​​among 100 mesh, 120 mesh, 140 mesh, and 150 mesh.

[0016] Preferably, the alkali treatment method is as follows: soaking bamboo fiber in a sodium hydroxide solution with a concentration of 5-10wt% for 30-60 minutes, washing with water until neutral, and drying the pretreated bamboo fiber.

[0017] Preferably, the mass ratio of the nano-calcium carbonate, cellulose nanocrystals, silane coupling agent, and ethanol aqueous solution is 3-6:2-4:1.5-2.5:25-35.

[0018] Preferably, the mass ratio of the nano-calcium carbonate, cellulose nanocrystals, silane coupling agent, and ethanol aqueous solution is 5:3:2:30.

[0019] Preferably, the ethanol-water solution is a mixture of ethanol and water in a mass ratio of 60-80:20-40.

[0020] Preferably, the silane coupling agent is KH550.

[0021] Preferably, the mass-to-volume ratio of the pretreated bamboo fiber to the suspension is 1-2g:200-300mL.

[0022] Preferably, the nano-calcium carbonate is cubic nano-calcium carbonate with a particle size of 100-500 nm.

[0023] Optionally, the particle size of the nano-calcium carbonate can be any single value or a range of any two values ​​from 100nm, 200nm, 300nm, 400nm, and 500nm.

[0024] Preferably, the particle size of the cellulose nanocrystals is 50-100 nm.

[0025] Optionally, the particle size of the cellulose nanocrystals can be any single value or a range of any two values ​​from 50nm, 60nm, 70nm, 80nm, 90nm, and 100nm.

[0026] Optionally, the mass fraction of the modified bamboo fiber can be any one value or a range of any two values ​​from 10 parts, 12 parts, 15 parts, 18 parts, and 20 parts.

[0027] Optionally, the mass fraction of the maleic anhydride-modified polyester elastomer can be any one of 2 parts, 3 parts, 4 parts, or 5 parts, or a range of any two of these values.

[0028] Preferably, the plasticizer is selected from at least one of glycerol, ethylene glycol, sorbitol and xylitol.

[0029] Optionally, the mass fraction of the plasticizer can be any one value among 1 part, 2 parts, and 3 parts, or a range of any two values.

[0030] Preferably, the plastic degradation toughening agent is HB820 and / or HB320 from Anmi Micro-Nano New Materials (Guangzhou) Co., Ltd.

[0031] Optionally, the mass fraction of the plastic degradation toughening agent can be any one value from 1 part, 2 parts, or 3 parts, or a range of any two values.

[0032] Preferably, the nucleating agent is a biodegradable nucleating agent.

[0033] Preferably, the degradable nucleating agent is RQT-CH-6 or RQT-CH-8 from Henan Ruichite Chemical Co., Ltd.

[0034] Optionally, the mass fraction of the nucleating agent can be any one of 0.5 parts, 0.7 parts, 0.9 parts, or 1 part, or a range of any two of these values.

[0035] Secondly, the present invention provides a method for preparing the above-mentioned biodegradable foam box for cold chain use, comprising the following steps:

[0036] S1. Thermoplastic starch granules, modified polylactic acid granules, modified bamboo fiber, maleic anhydride-modified polyester elastomer, plasticizer, plastic degradation toughening agent, and nucleating agent are mixed, extruded, and pelletized to obtain foaming masterbatch.

[0037] S2. Place the foaming masterbatch in a foaming mold, place the mold in a high-pressure foaming reactor for supercritical CO2 foaming, and then depressurize and cool to obtain the final product.

[0038] Preferably, the foaming conditions for the supercritical CO2 foaming are: temperature 120-150℃, pressure 15-25MPa, and time 2-4h.

[0039] Optionally, the foaming conditions for the supercritical CO2 foaming are as follows: the temperature can be any one value or a range of any two values ​​among 120℃, 130℃, 140℃, and 150℃; the pressure can be any one value or a range of any two values ​​among 15MPa, 18MPa, 20MPa, 22MPa, and 25MPa; and the time can be any one value or a range of any two values ​​among 2h, 3h, and 4h.

[0040] Preferably, the depressurization rate is 10-30 MPa / s.

[0041] Optionally, the pressure relief rate can be any one value among 10 MPa / s, 20 MPa / s, and 30 MPa / s, or a range of any two values.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) The present invention uses biodegradable thermoplastic starch particles and modified polylactic acid particles as the main foaming components to provide biodegradable foam boxes for cold chain. After degradation test, it shows obvious disintegration in natural soil in 90 days, degradation rate >80% in composting environment in 60 days, and complete disintegration after soaking in seawater for 120 days.

[0044] (2) The present invention proposes a biodegradable cold chain foam box with a compressive strength ≥120KPa, a 24h water absorption rate ≤1.5%, a thermal conductivity ≤0.021W / (m·K), and a heat preservation time of up to 1400min obtained by compounding modified bamboo fiber, maleic anhydride-modified polyester elastomer, and plastic degradation toughening agent. The modified bamboo fiber is modified by cubic nano-calcium carbonate and cellulose nanocrystal particles, which are loaded on the surface of the bamboo fiber. The cubic nano-calcium carbonate provides rigidity, and the cellulose nanocrystal particles provide rigidity. The hydrogen bonding of the crystalline particles enables bamboo fiber to form a hydrogen bond network with thermoplastic starch particles and modified polylactic acid particles, enhancing the interfacial bonding force. Under the action of maleic anhydride-modified polyester elastomer, thermoplastic starch particles, modified polylactic acid particles, and modified bamboo fiber can achieve optimal compatibility, avoiding the agglomeration of modified bamboo fiber. At the same time, the addition of specific plastic degradation toughening agents, after supercritical CO2 foaming, can form a uniform and dense closed-cell structure, thereby enabling the foam box to withstand greater external forces without being easily damaged and to have excellent thermal insulation performance. Attached Figure Description

[0045] Figure 1 This is a photograph of the biodegradable foam box for cold chain prepared in Example 1.

[0046] Figure 2 SEM image of bamboo fiber before modification;

[0047] Figure 3 SEM image of the modified bamboo fiber prepared in Example 1;

[0048] Figure 4 SEM image of the modified bamboo fiber prepared in Example 2;

[0049] Figure 5 SEM image of the modified bamboo fiber prepared in Example 3;

[0050] Figure 6 and Figure 7 The graph shows the test results of the thermal insulation performance of the biodegradable cold chain foam box prepared in Example 2. Detailed Implementation

[0051] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples of the present invention can be obtained from conventional commercial channels or by existing known methods.

[0052] Preparation Example 1: Preparation of Modified Bamboo Fiber 1:

[0053] The preparation method of modified bamboo fiber 1 is as follows: bamboo fiber is soaked in a 6wt% sodium hydroxide solution for 50 min, washed with water until neutral, and dried to pretreat the bamboo fiber; nano-calcium carbonate and cellulose nanocrystal particles are dispersed in an ethanol aqueous solution (a mixture of ethanol and water with a mass ratio of 70:30), and silane coupling agent KH550 is added to obtain a suspension; the pretreated bamboo fiber is added to the suspension for impregnation, and dried to obtain modified bamboo fiber.

[0054] The bamboo fiber has a mesh count of 120 and is sourced from Guangdong Limei New Material Technology Co., Ltd., model number: BF-2120.

[0055] The nano-calcium carbonate is cubic nano-calcium carbonate with a particle size of 200-300nm, sourced from Nanjing Hongde Nanomaterials Co., Ltd., model number: HDYZ22.

[0056] The cellulose nanocrystals have a particle size of 77nm and are sourced from Shenzhen Qieling New Materials Co., Ltd., model number: NCC100.

[0057] The mass ratio of the nano-calcium carbonate, cellulose nanocrystals, silane coupling agent, and ethanol aqueous solution is 5:3:2:30.

[0058] The mass-to-volume ratio of the pretreated bamboo fiber to the suspension is 1g:250mL.

[0059] SEM images of bamboo fiber before modification are shown below. Figure 2 As shown; SEM image of modified bamboo fiber 1 is shown below. Figure 3 As shown.

[0060] Preparation Example 2: Preparation of Modified Bamboo Fiber 2:

[0061] The preparation method of modified bamboo fiber 2 is as follows: bamboo fiber is soaked in a 6wt% sodium hydroxide solution for 50 min, washed with water until neutral, and dried to pretreat the bamboo fiber; cellulose nanocrystal particles are dispersed in an ethanol aqueous solution (a mixture of ethanol and water with a mass ratio of 70:30), and silane coupling agent KH550 is added to obtain a suspension; the pretreated bamboo fiber is added to the suspension for impregnation, and dried to obtain modified bamboo fiber.

[0062] The bamboo fiber has a mesh count of 120 and is sourced from Guangdong Limei New Material Technology Co., Ltd., model number: BF-2120.

[0063] The cellulose nanocrystals have a particle size of 77nm and are sourced from Shenzhen Qieling New Materials Co., Ltd., model number: NCC100.

[0064] The mass ratio of the cellulose nanocrystals, silane coupling agent, and ethanol aqueous solution is 8:2:30.

[0065] The mass-to-volume ratio of the pretreated bamboo fiber to the suspension is 1g:250mL.

[0066] SEM images of modified bamboo fiber 2 are as follows: Figure 4 As shown.

[0067] Preparation Example 3: Preparation of Modified Bamboo Fiber 3

[0068] The preparation method of modified bamboo fiber 3 is as follows: bamboo fiber is soaked in a 6wt% sodium hydroxide solution for 50 min, washed with water until neutral, and dried to pretreat the bamboo fiber; nano calcium carbonate is dispersed in an ethanol aqueous solution (a mixture of ethanol and water with a mass ratio of 70:30), and silane coupling agent KH550 is added to obtain a suspension; the pretreated bamboo fiber is added to the suspension for impregnation, and dried to obtain modified bamboo fiber.

[0069] The bamboo fiber has a mesh count of 120 and is sourced from Guangdong Limei New Material Technology Co., Ltd., model number: BF-2120.

[0070] The nano-calcium carbonate is cubic nano-calcium carbonate with a particle size of 200-300nm, sourced from Nanjing Hongde Nanomaterials Co., Ltd., model number: HDYZ22.

[0071] The mass ratio of the nano-calcium carbonate silane coupling agent to the ethanol aqueous solution is 8:2:30.

[0072] The mass-to-volume ratio of the pretreated bamboo fiber to the suspension is 1g:250mL.

[0073] SEM images of modified bamboo fiber 3 are as follows: Figure 5 As shown.

[0074] The raw materials used in the following examples and comparative examples are all commercially available, but are not limited to these materials:

[0075] Thermoplastic starch granules: sourced from Suzhou Koning Polyol Co., Ltd.;

[0076] Modified polylactic acid granules: derived from Bio-plus 301p by Guangzhou Bijia Materials Technology Co., Ltd.;

[0077] Maleic anhydride-modified polyester elastomer: sourced from KOAS Chemical Co., Ltd., model: BP-1;

[0078] Maleic anhydride-grafted polyolefin elastomer: derived from DuPont's Fusabond N495;

[0079] Plastic degradation toughening agent: HB820 from Anmi Micro-Nano New Materials (Guangzhou) Co., Ltd.;

[0080] Degradable nucleating agent: RQT-CH-6 from Henan Ruichite Chemical Co., Ltd.

[0081] Examples 1-3 and Comparative Examples 1-5 prepared biodegradable foam boxes for cold chain applications. The composition by mass parts is shown in Table 1 below.

[0082] Table 1

[0083]

[0084] The preparation method is as follows: according to Table 1, S1, thermoplastic starch granules, modified polylactic acid granules, modified bamboo fiber, maleic anhydride-modified polyester elastomer or maleic anhydride-grafted polyolefin elastomer, plasticizer, plastic degradation toughening agent, and degradable nucleating agent are mixed, extruded, and pelletized to obtain foaming masterbatch.

[0085] S2. Place the foaming masterbatch in a foaming mold, and place the mold in a high-pressure foaming reactor for supercritical CO2 foaming (foaming conditions: temperature 130℃, pressure 20MPa, time 3h). Depressurize and cool at a rate of 25MPa / s to obtain the final product.

[0086] Test Example 1:

[0087] The biodegradable cold chain foam boxes prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to the following performance tests:

[0088] 1. Compressive strength (10%): Tested according to GB / T 8813-2020;

[0089] 2. Water absorption rate: Tested according to GB / T 8810-2005;

[0090] 3. Thermal conductivity: Tested according to GB / T 10297-2015, with the inner side at 12℃ and the outer side at 50℃. The results are shown in Table 2.

[0091] Table 2

[0092]

[0093] As can be seen from Table 2, the foam boxes prepared in Examples 1-3 have excellent physical properties, with a compressive strength ≥120KPa, a 24h water absorption rate ≤1.5%, and a thermal conductivity ≤0.021W / (m·K).

[0094] Comparative Example 1 was different because the modified bamboo fiber 2 used did not contain nano-calcium carbonate; Comparative Example 2 was different because the modified bamboo fiber 3 used did not contain cellulose nanocrystals; Comparative Example 3 was different because it did not contain modified bamboo fiber; and Comparative Example 4 was different because the maleic anhydride-modified polyester elastomer was replaced with maleic anhydride-grafted polyolefin elastomer.

[0095] In Comparative Example 5, due to the absence of plastic degradation toughening agents, the compressive strength of the prepared foam boxes decreased; the water absorption rate and thermal conductivity both increased, indicating a decline in physical properties.

[0096] Test Example 2

[0097] The thermal insulation performance of the biodegradable cold chain foam box prepared in Example 2 was tested.

[0098] (1) A foam box and a foam box with a bag of ice were placed in temperatures of -25℃, 0℃, 25℃, and 40℃ respectively, with a humidity of 50%. The temperature changes were measured using a temperature recorder. The results are as follows: Figure 6 As shown;

[0099] (2) Place the foam boxes and 1-4 bags of ice respectively in a temperature of 25℃ and a humidity of 50%, and use a temperature recorder to test the temperature change. The results are as follows. Figure 7 As shown.

[0100] Depend on Figure 6 and Figure 7 It can be seen that the foam box prepared in Example 2 of the present invention has excellent thermal insulation performance at different temperatures, and the thermal insulation time can be up to 1400 min.

[0101] Test Example 3

[0102] The degradation performance and safety and environmental protection of the biodegradable cold chain foam box prepared in Example 2 were tested. The degradation performance results are shown in Table 3, and the safety and environmental protection performance results are shown in Table 4.

[0103] Table 3

[0104]

[0105] Table 4

[0106]

[0107] As can be seen from Tables 3 and 4, the foam box prepared in Example 2 of the present invention has excellent degradation performance and safety performance.

[0108] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A biodegradable foam box for cold chain use, characterized in that, By weight, it includes 70-90 parts thermoplastic starch granules, 10-30 parts modified polylactic acid granules, 10-20 parts modified bamboo fiber, 2-5 parts maleic anhydride-modified polyester elastomer, 1-3 parts plasticizer, 1-3 parts plastic degradation toughening agent, and 0.5-1 parts nucleating agent. The modified polylactic acid particles are Bio-plus 301p from Guangzhou Bijia Materials Technology Co., Ltd. The method for preparing the modified bamboo fiber includes the following steps: bamboo fiber is subjected to alkali treatment to obtain pretreated bamboo fiber; nano-calcium carbonate and cellulose nanocrystal particles are dispersed in an ethanol aqueous solution, and a silane coupling agent is added to obtain a suspension; the pretreated bamboo fiber is added to the suspension for impregnation, and then dried to obtain modified bamboo fiber. The maleic anhydride-modified polyester elastomer is BP-1 from KOAS Chemical Co., Ltd. The plastic degradation toughening agent is HB820 and / or HB320 from Anmi Micro-Nano New Materials Guangzhou Co., Ltd. The nucleating agent is a biodegradable nucleating agent; the biodegradable nucleating agent is RQT-CH-6 or RQT-CH-8 from Henan Ruichite Chemical Co., Ltd.

2. The biodegradable foam box for cold chain use according to claim 1, characterized in that, The mass ratio of the nano-calcium carbonate, cellulose nanocrystals, silane coupling agent, and ethanol aqueous solution is 36:2-4:1.5-2.5:25-35.

3. The biodegradable cold chain foam box according to claim 2, characterized in that, The nano-calcium carbonate is cubic nano-calcium carbonate with a particle size of 100-500 nm.

4. The biodegradable foam box for cold chain use according to claim 3, characterized in that, The cellulose nanocrystals have a particle size of 50-100 nm.

5. The method for preparing the biodegradable foam box for cold chain logistics according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Thermoplastic starch granules, modified polylactic acid granules, modified bamboo fiber, maleic anhydride-modified polyester elastomer, plasticizer, plastic degradation toughening agent, and nucleating agent are mixed, extruded, and pelletized to obtain foaming masterbatch. S2. Place the foaming masterbatch in a foaming mold, place the mold in a high-pressure foaming reactor for supercritical CO2 foaming, and then depressurize and cool to obtain the final product.

6. The method for preparing the biodegradable foam box for cold chain logistics according to claim 5, characterized in that, The foaming conditions for supercritical CO2 foaming are: temperature 120-150℃, pressure 15-25MPa, and time 2-4h.

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