Polyester is a kind of macromolecule compound obtained by the polymerization of polyols and polyacids. According to the kinds of alcohols and acids that make up polyesters, polyesters can be roughly divided into aliphatic polyesters, aromatic polyesters, aliphatic-aromatic copolyesters and other new copolyesters. Polyester synthesis is mainly divided into two ways: microbial synthesis and chemical synthesis. Materials processed from polyester raw materials can be roughly divided into polyester fibers, polyester films and rigid polyester materials according to their material and shape.
With the development of polyester industry, the demand for polyester materials is increasing day by day. A large number of waste polyester materials are burned, discarded or buried, which not only causes serious environmental pollution, but also exacerbates the shortage of petrochemical and land resources. With the increasing awareness of environmental protection, people's demand for environmentally friendly polyester is becoming more and more urgent. Generally speaking, environmentally friendly polyesters show a multi-level and progressive development trend from "reuse of polyester resources" to "petroleum-based degradable polyester", "bio-based polyester", and then to "bio-based degradable polyester". 1 regenerated polyester From the perspectives of sustainable development and circular economy, recycling waste polyester into recycled polyester materials is not only in line with the environmental protection concept of recycling and recycling, but also conducive to alleviating the shortage of resources. According to statistics, a ton of waste PET bottles can produce about 0.98 tons of recycled polyester fibers, which is equivalent to 6 tons less oil and saves 3 m3 of landfill space. 2 Petroleum-based Degradable Polyester In order to solve the problem of "white pollution" caused by the difficult degradation of plastic products in nature, developed countries put forward the concept of degradable plastics in the 1970s. After being discarded, degradable plastics can be decomposed into CO2 and H2O under natural conditions (light and microorganisms), and eventually return to nature. At present, photodegradable plastics and biodegradable plastics are the main biodegradable plastics. For polyesters, aliphatic polyesters contain hydrolyzable ester bonds, which are easily degraded by microorganisms, and belong to degradable polyesters. In addition, some petroleum-based aliphatic-aromatic polyesters (such as PBAT) also belong to degradable polyesters. 3 Bio-based Polyester In order to cope with and solve the shortage of petrochemical resources and environmental pollution, research and development of products based on renewable biomaterials has become a hot spot of science and technology at home and abroad and a development strategy supported by various countries. Compared with the development of petroleum-based degradable polyesters, the advantages of bio-based polyesters are that they can directly replace petrochemical raw materials with renewable biomass raw materials to produce monomer compounds, and PET and other polyester materials can be produced by conventional synthetic processes. Bio-based PET, for example, now accounts for about 40% of the global production capacity of bio-plastics, and occupies a dominant position. According to the forecast of European Bioplastics Association, the global production capacity of bioplastics will reach 7.8 million tons in 2019, and the high value-added applications of bio-based polyesters and other materials are really recognized. 4 Biodegradable Polyester Regenerated polyester and bio-based polyester can save petroleum resources to a certain extent and promote the development of circular economy, but these two environmentally friendly polyesters can not be degraded after the end of product life cycle and can not eradicate "white pollution" from the source. Degradable polyesters can eventually be decomposed into CO2 and H2 in natural environment, but at present most of the biodegradable polyesters with application value come from non-renewable petrochemical raw materials, so people turn their attention to biodegradable polyesters. Biodegradable polyester not only meets the requirements of biodegradability, but also meets the requirements of bio-based sources. Biodegradable polyester is made from biomass, which is synthesized by microorganism or biomass-based platform compounds. The typical biodegradable polyester synthesized by microorganisms is PHA, which is synthesized by microorganisms through life activities and stored in vivo. The biodegradable polyester synthesized by biomass-based platform compounds includes PLA, PCL, PGA and other common aliphatic polyesters.