Degradable and recyclable express bag and preparation method thereof

Abstract

The invention discloses a degradable and recyclable express bag and a preparation method thereof, and relates to the technical field of high polymer materials, the degradable and recyclable express bag is prepared by cutting and sealing composite plastic, and the composite plastic comprises a base layer, a bonding layer and a wear-resistant layer; the bonding layer is made of TPU (Thermoplastic Polyurethane) hot melt adhesive; the base layer and the wear-resistant layer are both prepared from lignin, polyethylene glycol and nano-silver particles; according to the express bag, a thermoplastic organic material with a low melting point can be used on the bonding layer, so that the express bag can be rapidly prepared and rapidly recycled after being used, the used express bag can be classified, the wear-resistant layer and the basic layer are separated through heating, the wear-resistant layer or the basic layer is recycled according to the intact degree of the express bag, and the express bag is classified and recycled; and the materials which cannot be recycled are degraded, so that the express bags can be recycled or treated more easily in an environment-friendly manner after being used, and the cyclic utilization rate of the materials is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a degradable and recyclable express bag and a preparation method thereof. Background Art

[0002] However, with the increasing use of plastic products, the environmental problems caused by waste plastics are becoming increasingly prominent. A large number of used polyethylene products, such as various express bags and packaging bags, are produced on the consumer side. If these waste polyethylene materials cannot be properly recycled, they will become difficult-to-degrade garbage and accumulate in the natural environment for a long time, causing serious pollution to ecological and environmental elements such as soil, water sources, and air, destroying the ecological balance, and also causing a huge waste of resources. Under the background of the rapid development of the current express delivery industry, the use of express bags is extremely large. In order to meet the national standards and ensure the safety of use of express bags, express companies generally require suppliers to use new materials for production, so as to ensure that the produced express bags can meet the corresponding standards in various quality indicators such as strength, toughness, and damage resistance, so as to meet the normal use of express parcels in many links such as transportation, sorting, and delivery, and avoid the occurrence of package damage and loss of items due to quality problems of express bags.

[0003] For example, the Chinese patent application number CN202210150148.8 is a recyclable composite packaging bag, the preparation method mainly includes the steps of preparing hydrophobic paper, preparing surface coating and coating molding. When preparing the surface coating, hexamethylene diisocyanate and toluene diisocyanate are used to modify lignin, and silver nanoparticles are added on this basis. Compared with the prior art, the food packaging bag prepared by the present invention has good hydrophobicity, strong mechanical properties, strong thermal stability and can effectively inhibit foodborne pathogens.

[0004] But with biodegradable bags, the value or desirability of recycling is further reduced, making it more difficult and costly to recycle. Summary of the invention

[0005] The embodiments of the present application solve the problem in the prior art that degradable courier bags are difficult to recycle, thereby achieving the recycling of courier bags.

[0006] The embodiment of the present application provides a degradable and recyclable express bag, which is made by cutting and sealing a composite plastic, wherein the composite plastic includes a basic layer, an adhesive layer, and a wear-resistant layer; the adhesive layer is made of TPU hot-melt adhesive; the basic 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 is dissolved in dimethyl sulfoxide, and then a curing agent and a catalyst are added to react to form a prepolymer, and 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 through a casting machine; then the dimethyl sulfoxide is slowly volatilized in a low-temperature oven (50-60° C.) for 10-12 hours, and then the basic layer plastic is cured at 105° C. for 3-5 hours; Wherein, 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 addition amount of the curing agent is 2.0% of the total mass of the base material; The catalyst is dibutyltin dilaurate, and the added amount is 1 part by weight; the particle size of the silver nanoparticles is 60-80nm.

[0008] Furthermore, the preparation method of the adhesive layer is: after the basic 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 basic layer is 3:2.

[0009] Furthermore, the preparation method of the wear-resistant layer is as follows: the wear-resistant layer is a woven plastic layer, and the preparation method is as follows: 40 parts by weight of lignin are taken again to prepare a plastic solution, and 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 embryonic wires of a certain width, drawn into flat wires, and the flat wires are woven by a weaving machine at a warp and weft density of 50 strands / 100 mm, woven into a shape, and a woven cloth is obtained.

[0010] Furthermore, the preparation method of the composite plastic is to place the wear-resistant layer on the surface coated with TPU hot melt adhesive, and to compound the three layers of film at 90°C using equipment such as hot pressing or hot rollers, and then cool to room temperature after compounding to obtain the composite plastic.

[0011] Furthermore, the adhesive layer contains nano silver particles, the weight portion of which is 0.1-0.3.

[0012] Furthermore, the preparation method of the composite plastic is: 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 compound the five-layer film at 90°C using equipment such as hot pressing or hot rollers, and cool to room temperature after compounding 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 nano-silver particles in the inner adhesive layer is 10-50 nm, and the particle size of the nano-silver particles in the outer adhesive layer is 50-100 nm.

[0016] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages: First, the combination of lignin and polyethylene glycol forms a stable chemical structure. Lignin is a natural polymer compound with good biodegradability. After use, the courier bag can be decomposed faster by microorganisms in the natural environment, reducing pollution to the environment. The wear-resistant layer contains more lignin. Lignin itself has good physical properties, high hardness and impact resistance. The increase in lignin content makes the wear-resistant layer tougher and can effectively resist external wear and tear, directly withstand friction and wear during transportation, and extend the service life of the courier bag. The lower lignin content makes the basic layer lighter and reduces logistics costs. It also has better elasticity, which can provide better buffering protection for the transported items and reduce the damage caused by these external forces to the items. The basic layer with less lignin content also has better air permeability, which can maintain the freshness and quality of the items and reduce damage or deterioration of the items caused by humidity or stuffiness. Second, silver particles enhance the tensile strength and wear 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 interface effect of nanoparticles reduces the melting point of TPU, improves the recovery and separation efficiency, and reduces the separation time to 79%-83% of the original separation time; Third, the inner and outer double-layer plastic bags can form a redundant moisture-proof barrier. Even if the outer plastic bag is damaged due to friction, the inner plastic bag can still maintain its sealing, greatly reducing the risk of moisture intrusion; the middle wear-resistant woven layer isolates the direct contact between the inner and outer plastic layers, avoiding the decrease in sealing strength due to material adhesion during heat sealing. The middle wear-resistant layer acts as a "skeleton" to disperse external impact forces and prevent sharp objects from directly piercing the inner basic layer; Fourthly, the nanosilver particles in the inner adhesive layer have a smaller particle size, which can release silver ions more effectively and have a larger contact area with microorganisms, thereby enhancing the antibacterial effect of the inner layer and ensuring the sterility of the items in the package; the nanosilver particles in the outer adhesive layer have a larger particle size and release silver ions at a slightly slower rate, but can form an effective antibacterial barrier in the outer layer to prevent the invasion of external microorganisms; and in the composite process, the small-particle silver ions in the inner and outer adhesive layers are attracted by the large-particle silver ions and agglomerate around them, reducing the migration of silver ions and preventing the reduction of the antibacterial effect. DETAILED DESCRIPTION

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs; the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the term "and / or" used herein includes any and all combinations of one or more related listed items.

[0018] Embodiment 1: The present application provides a degradable and recyclable express bag, which is made of composite plastic, and the composite plastic includes a basic layer, an adhesive layer, and a wear-resistant layer; the adhesive layer is made of TPU hot melt adhesive; the basic layer and the wear-resistant layer are both made of lignin and polyethylene glycol; The specific preparation method is: S1. Prepare the basic layer: dissolve 40 parts by weight of lignin in dimethyl sulfoxide, then add a curing agent and a catalyst to react to form a prepolymer, then add polyethylene glycol to the prepolymer, and then add 0.2 parts by weight of silver nanoparticles to mix evenly to obtain a plastic solution; cast the basic layer solution through a casting machine to form a film with a thickness of 0.05 mm; then slowly volatilize the dimethyl sulfoxide in a low-temperature oven (50-60°C) for 10-12 hours, and then cure at 105°C for 3-5 hours to obtain a basic layer plastic; Wherein, 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 addition amount of the curing agent is 2.0% of the total mass of the base material; The catalyst is dibutyltin dilaurate, and the addition amount is 1 part by weight; the particle size of the silver nanoparticles is 60-80nm; S2. Prepare an adhesive layer: After the base layer is dried, coat a layer of TPU hot melt adhesive on its surface, and the thickness ratio of the adhesive layer to the base layer is 3:2; S3, preparing the wear-resistant layer: the wear-resistant layer is a woven plastic layer, and the preparation method is to 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, and the plastic is stretched and oriented after drying and curing, and the film is cut into embryos of a certain width, and drawn into flat wires, and the flat wires are woven by a braiding machine at a warp and weft density of 50 strands / 100 mm, and the woven fabric is obtained; Wherein, the mass ratio of polyethylene glycol to lignin in the wear-resistant layer is 1:(1.5-3); S4. Prepare express bags: place the wear-resistant layer on the surface coated with TPU hot melt adhesive, and compound the three layers of film at 90°C using equipment such as hot pressing or hot rollers. After compounding, cool to room temperature to obtain a composite plastic; then cut and seal to form a complete express bag.

[0019] The technical solutions in the above embodiments of the present 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 courier bag can be decomposed more quickly by microorganisms in the natural environment, reducing pollution to the environment. The wear-resistant layer contains more lignin. Lignin itself has good physical properties, high hardness and impact resistance. The increase in lignin content makes the wear-resistant layer tougher and can effectively resist external wear and tear, directly withstand friction and wear during transportation, and extend the service life of the courier bag. The lower lignin content makes the base layer lighter, reducing logistics costs; it also has better elasticity, can provide better cushioning protection for the transported items, and reduce the damage caused by these external forces to the items; the lower lignin content base layer also has better air permeability, can maintain the freshness and quality of the items, and reduce the damage or deterioration of the items caused by humidity or stuffiness; The use of thermoplastic organic materials with low melting points in the adhesive layer can facilitate the rapid preparation of express bags and rapid recycling after use. The express bags after use can be classified, and the wear-resistant layer and the basic layer can be separated by heating. The wear-resistant layer or the basic layer can be recycled according to their integrity, and the unrecyclable ones can be recycled by degradation, so that the express bags can be more easily recycled or processed in an environmentally friendly manner after use, thereby improving the recycling rate of materials; Silver nanoparticles are added to both the basic layer and the wear-resistant layer. In the basic layer, the silver nanoparticles can increase the antibacterial ability during express delivery. In the wear-resistant layer, the silver nanoparticles can increase the wear resistance and friction of the express bag surface, increase the number of express bags that can be stacked, and improve transportation efficiency and maximum transportation time.

[0020] Embodiment 2: The above embodiment increases the recycling rate and biodegradability of the courier bag by using composite plastics, greatly increasing the environmental protection ability of the courier bag. In order to increase the speed of bonding and separation, further improvements are made on the basis of embodiment 1.

[0021] The only difference from Example 1 is that the adhesive layer also contains nano silver particles, with a weight portion of 0.1-0.3; The technical solutions in the above embodiments of the present 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 sustained-release effect and can maintain antibacterial ability during long-term use, thereby improving the antibacterial ability of express bags in long-term use or in humid environments; Silver particles enhance the tensile strength and wear 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 compounding time; at the same time, the interfacial effect of nanoparticles reduces the melting point of TPU, improves the recovery and separation efficiency, and reduces the separation time to 79%-83% of the original separation time.

[0022] Embodiment 3: Embodiment 2 improves the efficiency of compounding and separation by setting nanosilver particles in the adhesive layer. To improve the safety performance, sandwich compounding is performed on the basis of Embodiment 2.

[0023] In step S4, two basic 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 compounded at 90°C using equipment such as hot pressing or hot rollers. After compounding, 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 in the above embodiments of the present application have at least the following technical effects or advantages: The inner and outer double-layer plastic bags can form a moisture-proof barrier. Even if the outer plastic bag is damaged due to friction, the inner plastic bag can still maintain its sealing, greatly reducing the risk of moisture intrusion; The middle wear-resistant woven layer isolates the direct contact between the inner and outer plastic layers, avoiding the decrease in sealing strength due to material adhesion during heat sealing. The middle wear-resistant layer acts as a "skeleton" to disperse external impact forces 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 falling off and contaminating the contents; the inner basic layer is in direct contact with the goods, and the surface is smooth and easy to clean, meeting the requirements of aseptic packaging.

[0025] Embodiment 4: Embodiment 3 uses five layers of composite material to reduce the contact of the wear-resistant layer with the outside world, reduce the probability of impurities adhering to the express bag, and reduce the difficulty in recycling due to foreign matter or impurities. In order to improve the recycling efficiency, further improvements are made on the basis of Embodiment 3.

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

[0027] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages: The nanosilver particles in the inner adhesive layer have a smaller particle size, which can release silver ions more effectively and have a larger contact area with microorganisms, thereby enhancing the antibacterial effect of the inner layer and ensuring the sterility of the items in the package; the nanosilver particles in the outer adhesive layer have a larger particle size, and the speed of releasing silver ions is slightly slower, but they can form an effective antibacterial barrier in the outer layer to prevent the invasion of external microorganisms; and in the composite process, the small-diameter silver ions in the inner adhesive layer and the outer adhesive layer are attracted by the large-diameter silver ions and agglomerated around them, reducing the migration of silver ions and preventing the reduction of the antibacterial effect; Nano-silver particles of different particle sizes in the inner and outer layers have some influence on the moisture barrier performance. By optimizing the particle size distribution, the moisture-proof performance of the express bag can be further improved to ensure the dryness and freshness of the items in the package. Nanosilver particles of different particle sizes in the inner and outer layers affect the melting point of TPU, making the melting point interlayer peeling temperature of TPU different, improving the recycling and separation efficiency. During the recycling process, the inner and outer layers can be separated more easily by increasing the temperature, reducing the separation time and improving the recovery rate. In addition, due to the different particle sizes in the inner and outer layers, the peeling time is different, which can further distribute and peel different layers, making it easier to recycle and reuse. The larger-sized nanosilver particles in the outer adhesive layer reduce the adhesion of external impurities to the courier bag, thus reducing the risk of difficulty in recycling due to foreign matter or impurities; Nano-silver particles of different particle sizes in the inner and outer layers enhance the compatibility between the adhesive layer and the basic layer and the wear-resistant layer, thereby improving the overall structural stability of the express bag and reducing material breakage and waste during the recycling process, thereby increasing the recycling rate.

[0028] The express bags made 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 force test (GB\T1130); weight loss test, the mass before and after 120 days of burial was compared (ambient humidity 40%, temperature 20°C), and the weight loss rate was calculated. The results are shown in Table 1. ; ; Table 1 The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A degradable and recyclable courier bag, characterized in that: It is made of composite plastics through cutting and sealing, and the composite plastics include a basic layer, an adhesive layer, and a wear-resistant layer; the adhesive layer is made of TPU hot melt adhesive; the basic layer and the wear-resistant layer are both made of lignin, polyethylene glycol, and nano-silver particles; The preparation method of the adhesive layer is as follows: after the base layer is dried, a layer of TPU hot melt adhesive is coated on the surface thereof, and the thickness ratio of the adhesive layer to the base layer is 3:2; The adhesive layer contains nano silver particles, the weight portion of which is 0.1-0.3; 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, composite the five-layer film at 90°C using a hot press or hot roller and other equipment, and cool to room temperature after the composite to obtain a five-layer composite plastic including an inner basic layer, an inner adhesive layer, a wear-resistant layer, an outer adhesive layer, and an outer basic layer; The particle size of the nano-silver particles in the inner adhesive layer is 10-50nm, and the particle size of the nano-silver particles in the outer adhesive layer is 50-100nm.

2. A degradable and recyclable courier bag as claimed in claim 1, characterized in that: The preparation method of the basic layer is as follows: 40 parts by weight of lignin is dissolved in dimethyl sulfoxide, a curing agent and a catalyst are added to react to form a prepolymer, polyethylene glycol is added to the prepolymer, and 0.2 parts by weight of silver nanoparticles are added and mixed uniformly to obtain a plastic solution; the basic layer solution is cast into a film with a thickness of 0.05 mm by a casting machine; the dimethyl sulfoxide is slowly volatilized in a low-temperature oven (50-60° C.) for 10-12 hours, and then the film is cured at 105° C. for 3-5 hours to obtain a basic layer plastic; Wherein, 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 addition amount of the curing agent is 2.0% of the total mass of the base material; The catalyst is dibutyltin dilaurate, and the added amount is 1 part by weight; the particle size of the silver nanoparticles is 60-80nm.

3. A degradable and recyclable courier bag as claimed in claim 1, characterized in that: The preparation method of the wear-resistant layer is as follows: the wear-resistant layer is a woven plastic layer, and the preparation method is to 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, the plastic is stretched and oriented, and the film is cut into embryonic wires of a certain width, drawn into flat wires, and the flat wires are woven by a weaving machine at a warp and weft density of 50 strands / 100 mm, and the weaving is formed to obtain a woven cloth.

4. A degradable and recyclable courier bag as claimed in claim 1, characterized in that: The preparation method of the composite plastic is to place the wear-resistant layer on the surface coated with TPU hot melt adhesive, and to compound the three layers of film at 90° C. using equipment such as hot pressing or hot rollers, and to cool to room temperature after compounding to obtain the composite plastic.

5. A degradable and recyclable courier bag as claimed in claim 2, characterized in that: The mass ratio of polyethylene glycol to lignin in the base layer is 1:(1-1.2).

6. A degradable and recyclable courier bag as claimed in claim 3, characterized in that: The mass ratio of polyethylene glycol to lignin in the wear-resistant layer is 1:(1.5-3).