Biodegradable plastic is a kind of plastic which is degraded by the action of microorganisms such as bacteria, mould (fungus) and algae. The ideal biodegradable plastic is a kind of polymer material with excellent use performance, which can be completely decomposed by environmental microorganisms after being discarded, and finally become an integral part of carbon cycle in nature. "Paper" is a typical biodegradable material, while "synthetic plastic" is a typical polymer material. Therefore, biodegradable plastics are polymer materials with the properties of paper and synthetic plastics.
Biodegradable plastics can be divided into two types: complete biodegradable plastics and destructive biodegradable plastics. At present, destructive biodegradable plastics mainly include starch modified (or filled) polyethylene PE, polypropylene PP, PVC, polystyrene PS, etc.
Fully biodegradable plastics are mainly made from natural polymers (such as starch, cellulose, chitin) or agricultural and sideline products by microbial fermentation or synthesis of biodegradable polymers, such as thermoplastic starch plastics, aliphatic polyester, polylactic acid, starch / polyvinyl alcohol, etc.
At present, biodegradable plastics based on natural substances such as starch mainly include the following products: polylactic acid (PLA), polyhydroxyalkanoate (PHA), starch plastics, bioengineering plastics, and general-purpose plastics (polyolefin and PVC).
Due to its good degradability, biodegradable plastics are mainly used as soft and hard food packaging materials, which is also the largest application field at this stage.
The main target markets of biodegradable plastics are plastic packaging film, agricultural film, disposable plastic bag and disposable plastic tableware. Compared with traditional plastic packaging materials, the cost of new degradation materials is slightly higher. However, with the enhancement of environmental protection awareness, people are willing to use new degradation materials with higher price for environmental protection. The enhancement of environmental protection awareness has brought great opportunities for the development of new biodegradable materials industry. With the development of China's economy, the successful holding of the Olympic Games, the World Expo and many other large-scale activities shocked the world, the need for the protection of world cultural heritage and national scenic spots, the environmental pollution caused by plastics has been paid more and more attention, and the government at all levels has made the white pollution control one of the key work.
Developed countries and regions such as Europe, the United States and Japan have successively formulated and issued relevant laws and regulations, limiting the use of non degradable plastics through local prohibition, restriction, compulsory collection and collection of pollution taxes, etc., and vigorously developing new biodegradable materials to protect the environment and soil. In 2005, France issued a policy that all disposable plastic bags must be able to be used after 2010. biodegradation.
At the same time, China has introduced a number of policies to encourage the application and promotion of biodegradable plastics. In 2004, the National People's Congress passed the renewable energy law (Draft) and the solid waste law (Revised), encouraging the use of renewable biomass energy and the promotion and application of degradable plastics; in 2005, the national development and Reform Commission (NDRC) No. 40 document explicitly encouraged the use and promotion of biodegradable plastics; in 2006, the national development and Reform Commission launched a special fund on promoting the development of biomass biodegradable materials. Objective: the definition, classification, identification and degradation performance requirements of degradable plastics implemented on January 1, 2007 has been recognized by Europe, the United States, Japan and other countries, providing convenience for Chinese enterprises to export products.
According to the classification of raw materials, there are at least the following types of Biodegradable Plastics:
This kind of plastic has good biodegradability, the melting point is 62 ℃. The microorganisms that decompose it are widely distributed under the conditions of pleasant or anaerobic. As a biodegradable material, it can be mixed with starch, cellulose, or polymerized with lactic acid.
Poly (butylene succinate) (PBS) and its copolymers
The technology of manufacturing various high molecular weight polyester based on PBS (melting point: 114 ℃) has reached the level of industrial production. Japan's Mitsubishi Chemical and Showa polymer company has started industrial production, with a scale of about 1000 tons.
The Institute of physics and chemistry of Chinese Academy of Sciences is also carrying out the research on the synthesis of polybutylene succinate copolyester. The Institute of physics and chemistry of Chinese Academy of Sciences has cooperated with Shandong Huiying company to build a production line of PBS and its polymers with an annual output of 25000 tons, and Guangdong Jinfa company has built a production line with an annual output of 1000 tons. Tsinghua University has established a production line with an annual output of 10000 tons of PBS and its copolymers in Anqing Hexing Chemical Co., Ltd.
Polylactic acid (PLA)
NatureWorks company of the United States has done active and effective work in improving the production process of polylactic acid. It has developed the production of polylactic acid by fermentation of glucose in corn, with an annual production capacity of 14000 tons. Unitika company of Japan has developed and produced many kinds of products, among which canvas, tray and tableware are widely used in Aichi Expo.
China's industrialization includes Zhejiang Haisheng biodegradable plastics Co., Ltd. (production line with a scale of 5000 kilotons / year), and the pilot units are Shanghai tongjieliang biomaterials Co., Ltd., Jiangsu Jiuding group, etc.
国外实现工业化生产的主要为美国和巴西等国。国内生产单位有天津国韵生物材料有限公司（规模1万吨/年）  、宁波天安生物材料有限公司（规模2千吨/年），正在中试的单位有江苏南天集团股份有限公司等。
The United States and Brazil are the main countries to realize industrial production abroad. Domestic production units include Tianjin Guoyun biomaterial Co., Ltd. (10000 tons / year) , Ningbo Tian'an biomaterial Co., Ltd. (2000 tons / year), and Jiangsu Nantian Group Co., Ltd. is in pilot test.
The technology of producing degradable plastics by mixing aliphatic polyester and starch with biodegradable plastics from renewable resources has also been studied successfully. In European and American countries, starch and aliphatic polyester blends are widely used to produce garbage bags and other products. Novamont is the largest and best-selling company in the world. Its trade name is mater Bi. Its products are widely used in Europe and the United States.
There are many domestic research and production units, including Wuhan Huali Technology Co., Ltd. (40000 tons / year), Zhejiang HUAFA Ecological Technology Co., Ltd. (8000 tons / year), Zhejiang Tianhe Ecological Technology Co., Ltd. (5000 tons / year), Fujian best biological materials Co., Ltd. (2000 tons / year), Zhaoqing Huafang Degradation Plastics Co., Ltd. (5000 tons / year) Tons / year).
Aliphatic aromatic copolyester
The aliphatic aromatic random copolyester (ecoflex) manufactured by BASF company in Germany has the following monomers: adipic acid, terephthalic acid and 1,4-butanediol. The production capacity is 140000 tons / year. At the same time, the biodegradable plastic products based on polyester and starch were developed.
Polyvinyl alcohol (PVA) biodegradable plastics
For example, materbi products of novant in Italy mainly added PVA into starch in the 1990s, which can blow film and process other products. Polyvinyl alcohol materials need to be modified to have good biodegradability. The Institute of light industrial plastics processing and application of Beijing University of technology and industry has made some achievements in this respect.
Carbon dioxide copolymer
In foreign countries, the first countries to study carbon dioxide copolymers are mainly Japan and the United States, but they have not been industrialized. Inner Mongolia Mengxi Group Co., Ltd. adopts the technology of Changchun Institute of Applied Chemistry, and has built a device to produce 3000 tons of carbon dioxide / epoxy copolymer resin. The products are mainly used in packaging and medical materials. The low molecular weight CO 2 copolymer technology developed by Dr. Chen Liban, Guangzhou Institute of chemistry, Chinese Academy of Sciences, has been put into production in Taixing, Jiangsu Province. The product is low molecular weight CO 2 / epoxy copolymer, which is used as raw material of polyurethane foam material and packaging of household appliances. Henan Tianguan Group adopts the technology of Professor Meng Yuezhong from Zhongshan University, and has built a pilot scale carbon dioxide copolymer production line, which is expected to be pilot production this year.
Others such as chitin, polyamide, polyaspartic acid, glycan and cellulose are under development.
Poly - β - hydroxybutyrate (PHB)
Worldwide, PHB and PHBV are recognized as one of the most promising biodegradable plastics, as well as new products under development. The pilot production cost of the technical side is about 40 yuan / kg, and the cost of the products after industrial production will be further reduced. The price advantage is obvious, especially the production process of the technical side is simple and the equipment is simple, which is convenient for promotion and large-scale production.
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