How to make a fully degradable express bag?
Recently, the State Post Bureau stated at a regular press conference in the fourth quarter of 2022 that by the end of 2025, postal express outlets nationwide will ban the use of non-degradable plastic packaging bags, plastic tapes, and disposable plastic woven bags.
According to the national standard GB/T 38727-2020 "Packaging Plastic Films and Bags for Fully Biodegradable Logistics Express Transportation and Delivery", the made express bags need to have high strength to meet different load-bearing requirements, and the tensile strength needs to reach more than 20MPa. At the same time, the puncture performance needs to reach more than 2N under the needle of 1mm diameter. The molding cycle of express bags is complex, and it takes 4-7 days to complete the whole process of film blowing, printing, and side sealing bag making, which puts forward high requirements for the long-term side sealing performance of the material. It can complete the side sealing, and the side sealing is firm, and the side sealing strength is ≥15N/15mm, which will greatly expand the time window from film blowing to bag making.
A biodegradable express packaging bag is characterized in that: it is made of a composite film, the composite film comprises a first layer, a third layer and a second layer between the first layer and the third layer, the first layer , The third layer and the second layer are respectively made of film material A or film material B, the material of the first layer and the third layer is the same, and the material of the second layer and the first layer and the third layer are different.
The film material A, by weight percentage, is composed of the following components: polylactic acid 95.5%, degradable color masterbatch 3%, tackifier 1.5%; The film material B, by weight percentage, is composed of the following components Composition: polyadipic acid/butylene terephthalate 95%, degradable color masterbatch 3.5%, tackifier 1.5%; the tackifier is ethylene-acrylic acid copolymer; the degradable color masterbatch, according to In terms of weight percentage, it is prepared by heating and extruding the following components: 60~85% of biodegradable plastic carrier, 0~15% of filler, 5~25% of pigment, and 2~9% of auxiliary; The plastic carrier is one or more of polylactic acid, polyadipate/butylene terephthalate, and polybutylene succinate; the fillers in the degradable color masterbatch are silica and /or calcium carbonate, the pigment is an inorganic pigment or an organic pigment, the auxiliary agent is composed of a coupling agent, a plasticizer and a lubricant, and the coupling agent, the plasticizer and the lubricant all account for the weight percentage of the auxiliary agent respectively The coupling agent is a silane coupling agent; the plasticizer is diethylene glycol adipate and/or glycerol; the lubricant is oleic acid amide or erucic acid amide.
The preparation technology of the above-mentioned biodegradable express packaging bag, comprises the following steps:
(1) Mix the components measured by weight percentages, respectively, to obtain film material A and film material B;
(2) respectively place the film material A and film material B obtained in step (1) on the blown film, respectively In the hopper of the machine, the particles of film material A and film material B enter the screw section by their own weight. In the process of being extruded by the screw, the screw section is divided into five zones from the feed end to the discharge end to control the extrusion of film material A. The screw section temperature is: 90 ℃ in the first district, 120 ℃ in the second district, 160 ℃ in the third district, 180 ℃ in the fourth district, 175 ℃ in the fifth district; control the screw section of extrusion film material B Temperature is: 90 ℃ of first district, 110 ℃ of second districts, 150 ℃ of 3rd districts, 160 ℃ of 4th districts, 160 ℃ of 5th districts, after the film material of molten state is filtered through the head to remove impurities , into the same die for co-extrusion, and through inflation to obtain a white and black opaque composite film; then through the air ring cooling, bubble stabilization frame, herringbone splint and traction roller traction to obtain the tube material;
(3) The tube material is obtained; According to the requirements of finished bags, bag making and gluing are done.
