China's degradable plastics are in the early stage of industrialization, compared with the traditional petrochemical plastics field has a higher technical threshold, industry-related complete sets of production, equipment, design and development are more difficult, product-related modification technology needs to be developed, and the maturity of various degradable plastic product production technology is also different.
PLA technology
The main synthesis techniques of PLA include direct polycondensation (one step) and open ring polymerization (two step). This technology is less mature than PBAT. Among them, the direct polycondensation method (one-step method) is to use the activity of lactic acid in the presence of a dehydrating agent to remove the carboxyl and hydroxyl groups, so that the lactic acid molecules are polycondensed to form a low molecular polymer, and then the molecules are directly condensed into PLA by high temperature dehydration. Secondly, the cycle-opening polymerization method (two-step method) is to synthesize lactic acid monomer into ethyl ester by dehydration cyclization, and then recrystallized ethyl ester polymerization reaction to obtain PLA, and PLA with high molecular weight can be obtained by this method. At present, the projects to achieve industrial production are mostly two-step technology, the technology is more mature, the overall product molecular weight is higher, the PLA output can reach more than 200,000 t, and the performance is better. From the perspective of market production capacity, the PLA technical process has also been initially opened up, and a more mature complete set of process production equipment has been developed.
PBS/PBAT technology
The industrialization technology process of PBAT and PBS has been opened up, and there are mature complete sets of industrialization projects of technical equipment, and the technology maturity is relatively high.
Foreign PBAT process development earlier, BASF company launched degradable plastic PBAT (Ecoflex) in 1998, and has been rapidly promoted, the current production capacity of 74,000 t/a. Recently, the first phase of the BASF (Guangdong) integration project will build six new PBAT production lines, with a combined capacity of 160,000 t/a (the news was falsified). Italy's Novamont company is the world's first biodegradable plastics industrialization enterprises, in 2004, Novamont company acquired Eastar-Bio copolyester biodegradable plastics business of the United States Eastman Company, the production of PBAT trade name is Origo-Bi, production capacity reached 100,000 t/a.
Through comparative analysis, it can be seen that the domestic PBAT production technology is mature, and the PBAT production technology represented by Juyou Chemical has the advantages of continuous process, efficient by-product treatment, and good product quality, and has been widely applied. The one-step production of PBS/PBAT technology developed by the Institute of Physics and Chemistry of the Chinese Academy of Sciences has the advantages of reducing equipment investment and material loss. The successful development of flexible equipment avoids the limitations of other production lines that can only produce specialized products, can adapt to the market demand for different products, and also lays the foundation for enterprises to flexibly respond to market changes and maximize benefits.
The composite modification technology of PBAT/ other degradable materials is briefly described as follows: Polylactic acid (PLA) has excellent mechanical properties and good degradability, aiming at the shortcomings of poor mechanical properties of PBAT material, the blending modification of PLA and PBAT can improve the strength and elastic modulus, and at the same time, PBAT/PLA composite maintains good degradability. A biodegradable composite of PBAT and stereo-complex polylactic acid (sc-PLA) was prepared by melt blending method. After blending PBAT with sc-PLA, a spherical filler permeation network structure was formed in the blend, which showed higher yield stress and modulus. In order to improve the mechanical properties of PBAT/PLA composites to a greater extent, it is necessary to improve the compatibility of PBAT and PLA.
PLA+PBAT is used to make biodegradable packaging bags, which can be decomposed into water and carbon dioxide under specific circumstances, without pollution to the environment.
