Degradable and recyclable express bag and preparation method thereof

Abstract

This application discloses a biodegradable and recyclable express delivery bag and its preparation method, relating to the field of polymer materials technology. It is made by cutting and sealing a composite plastic, which includes a base layer, an adhesive layer, and a wear-resistant layer. The adhesive layer is made of TPU hot melt adhesive. Both the base layer and the wear-resistant layer are made of lignin, polyethylene glycol, and nano-silver particles. By using a low-melting-point thermoplastic organic material in the adhesive layer, the express delivery bag can be quickly prepared and rapidly recycled after use. The used express delivery bag can be sorted, and the wear-resistant layer and base layer can be separated by heating. The wear-resistant layer or base layer can be recycled depending on its condition. The non-recyclable parts are degraded, making it easier to achieve environmentally friendly recycling or disposal of the express delivery bag after use, thus improving the recycling rate of materials.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a biodegradable and recyclable express delivery bag and its preparation method. Background Technology

[0002] However, with the continuous increase in the use of plastic products, the environmental problems caused by waste plastics are becoming increasingly prominent. Consumers generate a large amount of used polyethylene products, such as various express delivery bags and packaging bags. If these waste polyethylene materials are not properly recycled, they will become non-biodegradable waste, accumulating in the natural environment for a long time, causing serious pollution to ecological elements such as soil, water, and air, disrupting the ecological balance, and also resulting in a huge waste of resources. Given the rapid development of the express delivery industry, the use of express delivery bags is extremely large. Due to considerations such as the need for express delivery bags to meet national standards and ensure safety, express delivery companies typically require suppliers to use virgin materials for production. This ensures that the produced express delivery bags meet the corresponding standards in terms of strength, toughness, and tear resistance, thus meeting the normal use of express parcels in transportation, sorting, and delivery, and avoiding damage to parcels and loss of items due to express delivery bag quality problems.

[0003] For example, Chinese patent application number CN202210150148.8 describes a recyclable composite packaging bag. The preparation method mainly includes steps such as preparing hydrophobic paper, preparing a surface coating, and coating molding. In preparing the surface coating, hexamethylene diisocyanate and toluene diisocyanate are used to modify lignin, and silver nanoparticles are added on this basis. Compared with existing technologies, the food packaging bag prepared by this invention has better hydrophobic properties, stronger mechanical properties, stronger thermal stability, and can effectively inhibit foodborne pathogens.

[0004] However, for biodegradable bags, their recycling value or potential decreases further, making them more difficult to recycle and increasing costs. Summary of the Invention

[0005] The embodiments of this application solve the problem that biodegradable express bags are difficult to recycle in the prior art, and realize the recycling of express bags.

[0006] This application provides a biodegradable and recyclable express delivery bag, which is made of composite plastic through cutting and sealing. The composite plastic includes a base layer, an adhesive layer, and a wear-resistant layer. The adhesive layer is made of TPU hot melt adhesive. The base layer and the wear-resistant layer are both made of lignin, polyethylene glycol, and nano silver particles.

[0007] Furthermore, the preparation method of the basic layer is as follows: 40 parts by weight of lignin are dissolved in dimethyl sulfoxide, then a curing agent and a catalyst are added to react and form a prepolymer, then polyethylene glycol is added to the prepolymer, and then 0.2 parts by weight of silver nanoparticles are added and mixed evenly to obtain a plastic solution; the basic layer solution is cast into a film with a thickness of 0.05 mm using a casting machine; then the dimethyl sulfoxide is slowly evaporated in a low-temperature oven (50-60℃) for 10-12 hours, and then cured at 105℃ for 3-5 hours to obtain the basic layer plastic; The curing agent is a mixture of hexamethylene diisocyanate and toluene diisocyanate; the mass ratio of hexamethylene diisocyanate to toluene diisocyanate is 1:2; the amount of curing agent added is 2.0% of the total mass of the matrix material. The catalyst is dibutyltin dilaurate, added in 1 part by weight; the silver nanoparticles have a particle size of 60-80 nm.

[0008] Furthermore, the adhesive layer is prepared by coating a layer of TPU hot melt adhesive on its surface after the base layer is dried, with the thickness ratio of the adhesive layer to the base layer being 3:2.

[0009] Furthermore, the wear-resistant layer is prepared as follows: the wear-resistant layer is a woven plastic layer, and the preparation method is as follows: take 40 parts by weight of lignin again to prepare a plastic solution, and the preparation method is the same as that of the basic layer. After drying and curing, stretch and orient the plastic, and cut the film into filaments of a certain width, draw them into flat filaments, and weave the flat filaments into a warp and weft density of 50 threads / 100mm using a weaving machine to form a woven fabric.

[0010] Furthermore, the method for preparing the composite plastic involves placing a wear-resistant layer onto a surface coated with TPU hot melt adhesive, and then laminating the three layers together at 90°C using equipment such as hot press or hot rollers. After lamination, the composite plastic is cooled to room temperature to obtain the composite plastic.

[0011] Furthermore, the adhesive layer contains silver nanoparticles, with a weight ratio of 0.1-0.3%.

[0012] Furthermore, the preparation method of the composite plastic is as follows: take two basic layers coated with hot melt adhesive, place the wear-resistant layer between the inner and outer surfaces coated with TPU hot melt adhesive, and laminate the five-layer film at 90°C using equipment such as hot press or hot roller. After lamination, cool to room temperature to obtain a five-layer composite plastic.

[0013] Furthermore, the mass ratio of polyethylene glycol to lignin in the base layer is 1:(1-1.2).

[0014] Furthermore, the mass ratio of polyethylene glycol to lignin in the wear-resistant layer is 1:(1.5-3).

[0015] Furthermore, the particle size of the silver nanoparticles in the inner adhesive layer is 10-50 nm, and the particle size of the silver nanoparticles in the outer adhesive layer is 50-100 nm.

[0016] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: Firstly, the combination of lignin and polyethylene glycol forms a stable chemical structure. Lignin is a natural polymer compound with good biodegradability. After use, the express bag can be decomposed more quickly by microorganisms in the natural environment, reducing environmental pollution. Secondly, the wear-resistant layer contains more lignin. Lignin itself has excellent physical properties, including high hardness and impact resistance. The increased lignin content makes the wear-resistant layer more durable, effectively resisting external wear and directly bearing the friction and wear during transportation, extending the express bag's lifespan. Thirdly, the lower lignin content makes the base layer lighter, reducing logistics costs. It also has better elasticity, providing better cushioning protection for transported items and reducing damage caused by external forces. Finally, the base layer with lower lignin content also has better breathability, maintaining the freshness and quality of items and reducing damage or spoilage caused by moisture or heat. Secondly, silver particles enhance the tensile strength and abrasion resistance of TPU, reducing the risk of delamination of the composite layer under bending or impact, accelerating the melting efficiency of the adhesive layer during hot pressing, and shortening the processing time to 64%-74% of the original composite time; at the same time, the interfacial effect of nanoparticles lowers the melting point of TPU, improves recycling and separation efficiency, and reduces the separation time to 79%-83% of the original separation time. Third, the double-layered plastic bags can form a redundant moisture barrier. Even if the outer plastic bag is damaged by friction, the inner plastic bag can still maintain its seal, greatly reducing the risk of moisture intrusion. The middle wear-resistant woven layer isolates the direct contact between the inner and outer plastic layers, preventing the sealing strength from decreasing due to material adhesion during heat sealing. The middle wear-resistant layer acts as a "skeleton" to disperse external impact and prevent sharp objects from directly piercing the inner basic layer. Fourth, the smaller size of the silver nanoparticles in the inner adhesive layer allows for more effective release of silver ions and a larger contact area with microorganisms, thereby enhancing the antibacterial effect of the inner layer and ensuring the sterility of the packaged items. The larger size of the silver nanoparticles in the outer adhesive layer results in a slightly slower release of silver ions, but it forms an effective antibacterial barrier on the outer layer to prevent the invasion of external microorganisms. Furthermore, during the lamination process, the smaller silver ions in both the inner and outer adhesive layers are attracted to and aggregate around the larger silver ions, reducing silver ion migration and preventing a decrease in the antibacterial effect. Detailed Implementation

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0018] Example 1: This application provides a biodegradable and recyclable express delivery bag made of composite plastic, which includes a base layer, an adhesive layer, and a wear-resistant layer; the adhesive layer is made of TPU hot melt adhesive; the base layer and the wear-resistant layer are both made of lignin and polyethylene glycol; The specific preparation method is as follows: S1. Preparation of the base layer: Dissolve 40 parts by weight of lignin in dimethyl sulfoxide, then add curing agent and catalyst to react and form a prepolymer. Then add polyethylene glycol to the prepolymer, and add 0.2 parts by weight of silver nanoparticles and mix evenly to obtain a plastic solution. Cast the base layer solution into a film with a thickness of 0.05 mm using a casting machine. Then slowly evaporate the dimethyl sulfoxide in a low temperature oven (50-60℃) for 10-12 h, and then cure at 105℃ for 3-5 h to obtain the base layer plastic. In the basic layer, the mass ratio of polyethylene glycol to lignin is 1:(1-1.2); The curing agent is a mixture of hexamethylene diisocyanate and toluene diisocyanate; the mass ratio of hexamethylene diisocyanate to toluene diisocyanate is 1:2; the amount of curing agent added is 2.0% of the total mass of the matrix material. The catalyst is dibutyltin dilaurate, added at 1 part by weight; the silver nanoparticles have a particle size of 60-80 nm. S2. Preparation of adhesive layer: After the base layer is dried, a layer of TPU hot melt adhesive is coated on its surface. The thickness ratio of the adhesive layer to the base layer is 3:2. S3. Preparation of wear-resistant layer: The wear-resistant layer is a woven plastic layer. The preparation method is to take 40 parts by weight of lignin again to prepare a plastic solution. The preparation method is the same as that of the basic layer. After drying and curing, the plastic is stretched and oriented, and the film is cut into filaments of a certain width, drawn into flat filaments, and woven into woven fabric by a weaving machine at a warp and weft density of 50 threads / 100mm. In the wear-resistant layer, the mass ratio of polyethylene glycol to lignin is 1:(1.5-3). S4. Preparation of express delivery bags: Place the wear-resistant layer on the surface coated with TPU hot melt adhesive, and laminate the three layers of film at 90°C using equipment such as hot press or hot roller. After lamination, cool to room temperature to obtain composite plastic; then cut and seal to form a complete express delivery bag.

[0019] The technical solutions described in the embodiments of this application have at least the following technical effects or advantages: The combination of lignin and polyethylene glycol forms a stable chemical structure. Lignin is a natural polymer compound with good biodegradability. After use, the express delivery bag can be decomposed by microorganisms in the natural environment more quickly, reducing pollution to the environment. The wear-resistant layer contains more lignin. Lignin itself has good physical properties, such as high hardness and impact resistance. The increase in lignin content makes the wear-resistant layer more tough, effectively resisting external wear and directly bearing the friction and wear during transportation, thus extending the service life of the express bag. The lower lignin content makes the base layer material lighter, reducing logistics costs; it also has better elasticity, providing better cushioning protection for transported items and reducing damage caused by external forces; the lower lignin content of the base layer also has better breathability, which can maintain the freshness and quality of items and reduce damage or deterioration caused by moisture or heat. Using thermoplastic organic materials with low melting points in the adhesive layer facilitates the rapid preparation and recycling of express bags after use. It allows for the sorting of used express bags, separating the wear-resistant layer and the base layer by heating, and recycling the wear-resistant layer or the base layer depending on their condition. The non-recyclable parts are then degraded, making it easier to achieve environmentally friendly recycling or disposal of express bags after use and improving the recycling rate of materials. Silver nanoparticles are incorporated into both the base layer and the wear-resistant layer. In the base layer, the silver nanoparticles enhance the antibacterial properties of the package during delivery. In the wear-resistant layer, the silver nanoparticles increase the wear resistance and friction of the package surface, thereby increasing the number of packages that can be stacked and improving transportation efficiency and maximum delivery time.

[0020] Example 2: The above example increases the recycling rate and biodegradability of express delivery bags by using composite plastics, which greatly enhances the environmental protection capabilities of express delivery bags. Further improvements are made based on Example 1 to increase the speed of bonding and separation.

[0021] The only difference from Example 1 is that the adhesive layer also contains silver nanoparticles, with a weight ratio of 0.1-0.3. The technical solutions described in the embodiments of this application have at least the following technical effects or advantages: The silver nanoparticles in the adhesive layer can further inhibit the growth of microorganisms between layers or inside the bag, forming an all-round antibacterial barrier from the inside (basic layer) to the outside (wear-resistant layer); the silver nanoparticles in the adhesive layer have a certain slow-release effect, which can maintain antibacterial ability during long-term use and improve the antibacterial ability of the express bag in long-term use or humid environment. Silver particles enhance the tensile strength and abrasion resistance of TPU, reduce the risk of delamination of the composite layer under bending or impact, accelerate the melting efficiency of the adhesive layer during hot pressing, and shorten the processing time to 64%-74% of the original composite time. At the same time, the interfacial effect of nanoparticles lowers the melting point of TPU, improves recycling and separation efficiency, and reduces the separation time to 79%-83% of the original separation time.

[0022] Example 3: Example 2 improved the efficiency of composite and separation by setting silver nanoparticles in the adhesive layer. To improve safety performance, sandwich composite was carried out based on Example 2.

[0023] In step S4, two base layers coated with hot melt adhesive are taken, and the wear-resistant layer is placed between the inner and outer surfaces coated with TPU hot melt adhesive. The five-layer film is laminated at 90°C using equipment such as hot press or hot roller. After lamination, it is cooled to room temperature to obtain a five-layer composite plastic. Then, it is cut and sealed to form a complete express bag.

[0024] The technical solutions described in the embodiments of this application have at least the following technical effects or advantages: The double-layered plastic bags can form a moisture barrier. Even if the outer plastic bag is damaged by friction, the inner plastic bag can still maintain its seal, greatly reducing the risk of moisture intrusion. The middle wear-resistant braided layer isolates the inner and outer plastic layers from direct contact, preventing the sealing strength from decreasing due to material adhesion during heat sealing. The middle wear-resistant layer acts as a "skeleton" to disperse external impact and prevent sharp objects from directly piercing the inner basic layer. The basic layer can elastically buffer pressure, and combined with the rigid support of the wear-resistant layer, the overall pressure resistance is improved, and the stacking height can be increased by 20-30%; the outer basic layer can prevent the wear-resistant layer fibers from shedding and contaminating the contents; the inner basic layer is in direct contact with the goods, and its smooth surface is easy to clean, meeting the requirements of aseptic packaging.

[0025] Example 4: Example 3 uses a five-layer composite to reduce the contact between the wear-resistant layer and the outside world, thereby reducing the probability of impurities adhering to the express bag and making it less difficult to recycle due to foreign objects or impurities. To improve recycling efficiency, further improvements are made based on Example 3.

[0026] The particle size of the silver nanoparticles in the inner adhesive layer is 10-50 nm, and the particle size of the silver nanoparticles in the outer adhesive layer is 50-100 nm.

[0027] The technical solutions described in the embodiments of this application have at least the following technical effects or advantages: The smaller size of the silver nanoparticles in the inner adhesive layer allows for more effective release of silver ions and a larger contact area with microorganisms, thereby enhancing the antibacterial effect of the inner layer and ensuring the sterility of the packaged items. The larger size of the silver nanoparticles in the outer adhesive layer results in a slightly slower release of silver ions, but it forms an effective antibacterial barrier on the outer layer, preventing the invasion of external microorganisms. Furthermore, during the lamination process, the smaller silver ions in both the inner and outer adhesive layers are attracted to and aggregate around the larger silver ions, reducing silver ion migration and preventing a decrease in the antibacterial effect. The different particle sizes of the inner and outer layers of silver nanoparticles affect the moisture barrier performance. By optimizing the particle size distribution, the moisture-proof performance of the express bag can be further improved, ensuring the dryness and freshness of the items inside the packaging. The different sizes of silver nanoparticles in the inner and outer layers affect the melting point of TPU, resulting in different interlayer peeling temperatures. This improves recycling and separation efficiency. During recycling, heating makes it easier to separate the inner and outer layers, reducing separation time and increasing the recovery rate. Furthermore, the different particle sizes in the inner and outer layers result in different peeling times, allowing for further distribution and peeling of different layers, which is convenient for recycling and reuse. The larger-sized nano-silver particles in the outer adhesive layer reduce the adhesion of external impurities to the express bag, reducing the risk of difficulty in recycling due to foreign objects or impurities. Nano-silver particles of different sizes in the inner and outer layers enhance the compatibility between the adhesive layer and the base and wear-resistant layers, improve the overall structural stability of the express bag, reduce material damage and waste during recycling, and thus improve the recycling rate.

[0028] The express bags prepared in Examples 1 to 4 were subjected to performance tests, including tensile strength test (GB / T1040.3); elongation at break test (GB / T1040.1); right-angle tear test (GB / T1130); weight loss test, and the mass before and after burying in soil for 120 days was compared (ambient humidity 40%, temperature 20℃). The weight loss rate was calculated, and the results are shown in Table 1. ; ; Table 1 The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A biodegradable and recyclable express delivery bag, characterized in that, Made from composite plastic through cutting and sealing, the composite plastic includes a base layer, an adhesive layer, and a wear-resistant layer; the adhesive layer is made of TPU hot melt adhesive; the base layer and the wear-resistant layer are both made of lignin, polyethylene glycol, and nano silver particles; The adhesive layer is prepared by: after the base layer is dried, a layer of TPU hot melt adhesive is coated on its surface, and the thickness ratio of the adhesive layer to the base layer is 3:

2. The adhesive layer contains silver nanoparticles, with a weight ratio of 0.1-0.

3. The method for preparing composite plastic is as follows: take two base layers coated with hot melt adhesive, place the wear-resistant layer between the inner and outer surfaces coated with TPU hot melt adhesive, and laminate the five-layer film at 90°C using hot pressing or hot roller equipment. After lamination, cool to room temperature to obtain a five-layer composite plastic including an inner base layer, an inner adhesive layer, a wear-resistant layer, an outer adhesive layer, and an outer base layer. The particle size of the silver nanoparticles in the inner adhesive layer is 10-50 nm, and the particle size of the silver nanoparticles in the outer adhesive layer is 50-100 nm.

2. The biodegradable and recyclable express delivery bag as described in claim 1, characterized in that, The preparation method of the basic layer is as follows: 40 parts by weight of lignin are dissolved in dimethyl sulfoxide, then a curing agent and a catalyst are added to react and form a prepolymer. Polyethylene glycol is then added to the prepolymer, and 0.2 parts by weight of silver nanoparticles are added and mixed evenly to obtain a plastic solution. The basic layer solution is cast into a film with a thickness of 0.05 mm using a casting machine. Then, dimethyl sulfoxide is slowly evaporated in an oven at 50-60℃ for 10-12 h, and then cured and crosslinked at 105℃ for 3-5 h to obtain the basic layer plastic. The curing agent is a mixture of hexamethylene diisocyanate and toluene diisocyanate; the mass ratio of hexamethylene diisocyanate to toluene diisocyanate is 1:2; the amount of curing agent added is 2.0% of the total mass of the matrix material. The catalyst is dibutyltin dilaurate, added in 1 part by weight; the silver nanoparticles have a particle size of 60-80 nm.

3. The biodegradable and recyclable express delivery bag as described in claim 1, characterized in that, The wear-resistant layer is prepared as follows: the wear-resistant layer is a woven plastic layer. The preparation method is to take 40 parts by weight of lignin again to prepare a plastic solution. The preparation method is the same as that of the basic layer. After drying and curing, the plastic is stretched and oriented, and the film is cut into filaments of a certain width and drawn into flat filaments. The flat filaments are then woven into a warp and weft density of 50 threads / 100mm using a weaving machine to obtain a woven fabric.

4. The biodegradable and recyclable express delivery bag as described in claim 2, characterized in that, In the base layer, the mass ratio of polyethylene glycol to lignin is 1:(1-1.2).

5. A biodegradable and recyclable express delivery bag as described in claim 3, characterized in that, In the wear-resistant layer, the mass ratio of polyethylene glycol to lignin is 1:(1.5-3).