In recent years, with the implementation of the “plastic ban”, biodegradable plastics have gradually entered the public’s vision, which is of vital significance for the development of environmental protection packaging industry.
At present, there are about 20 kinds of biodegradable plastics commonly seen in the market, which can be divided into two categories: bio based degradable plastics and petrochemical based degradable plastics according to the source of raw materials:
Biobased degradable plastics include thermoplastic starch, PLA, PHA, etc.
Petrochemical based degradable plastics include PBAT, PBS, PPC, PCL, etc.
Biodegradable plastics refer to plastics that are degraded by microorganisms existing in nature under natural conditions, such as soil or sandy soil, under specific conditions, such as composting, anaerobic digestion or aqueous culture medium, and finally completely degraded into carbon dioxide (CO2) and methane (CH4), water (H2O) and the mineralized inorganic salts of its elements, as well as new biomass.
The properties of the products can meet the requirements of use. The properties remain unchanged during the storage period. After use, the products can be degraded into harmless substances under natural environmental conditions. The main application fields of degradable plastics include agricultural mulch, various types of plastic packaging bags, garbage bags, shopping bags in shopping malls and disposable catering utensils.
In order to better seize the market opportunity, all technical R&D teams of Cowin Extrusion developed and produced special models suitable for PLA, PBAT and other degradable plastic modification granulation based on the common twin screw extruder technology, which improved the problems of low screw speed and low capacity of the start-up screw of degradable modified materials.
There are generally two granulating processes for biodegradable plastics: Air-cooling strand granulation line and Underwater granulation line.
The production process of Air-cooling strand granulation line as follows:
Twin screw feeder—Twin screw extruder—Hydraulic plate screen change—Die head —Stainless steel conveyor belt—Dryer—Pelletizer—vibrating screen
This granulation method is adopted by the majority of manufacturers with high cost performance.
The production process of Underwater granulation line as follows:
Twin screw feeder—Twin screw extruder—Hydraulic plate screen change—Underwater pelletizer—Centrifugal dehydrator—Circulating water tank—vibrating screen
Cowin CHT series parallel co-rotating twin-screw extruder produces PLA degradable plastic strips onto the air-cooled steel conveyor belt. There are 18 fans above the conveyor belt to air cool the extruded plastic strips through fans, and then they are transported to the pelletizer to complete the air cooling strand granulation.The air-cooling strand granulation line has low cost, simple equipment and convenient maintenance, which is selected by the majority of manufacturers.
Cowin Extrusion has not only the granulation production line for biodegradable materials, but also the sheet production line. PLA degradable sheet production line equipment composition: co-rotating twin screw extruder, screen changer, melt metering pump, mold, three roller calender, cooling bracket, trimming device, tractor, winder, etc.
Features of PLA degradable sheet production line:
Adopted double screw design, specifically for polylactic acid, corn starch melt design, aiming at the particularity of material by vacuum exhaust, Three-roller forming, adjustable roller temperature through the die temperature machine, ensure that products do not paste, products forming on the surface of good color, good toughness and the thickness of the dial gauge positioning, winding adopts automatic tension winding.
The PLA sheet extrusion production line is applicable to the production of PLA and modified PLA. PLA is derived from plant resources and can be directly used for extrusion molding. Due to its biodegradability, compostability, recyclability and other characteristics, PLA and modified PLA are widely used in electronic product shells, auto parts, instruments, clothing fibers, agricultural mulch, food packaging, tableware and other fields. It is a high-tech environmental protection product encouraged by the country.