Polylactic acid (PLA) is a new type of polyester material produced from organic acid lactic acid. It has advantages over existing plastic materials such as polyethylene, polypropylene, and polystyrene. It is defined by the industry as the most promising for the new century. New packaging materials, which are environmentally-friendly packaging materials, are expected to replace plastics such as polyethylene, polypropylene, and polystyrene in the future, and have broad application prospects. Polylactic acid performance Polylactic acid has good biodegradability, can be completely degraded by microorganisms in nature after use, and various products made of it can be buried in soil for 6-12 months to complete automatic degradation. After it is used, the waste is buried in soil or in water, and carbonic acid gas and water can be formed under the decomposition of microorganisms. In sunlight, they will produce starch as a starting raw material through photosynthesis. In this way, a cyclic process can recover both the polylactic acid raw material starch and the photosynthesis reducing the content of carbon dioxide in the air. Polylactic acid has good mechanical properties and physical properties, suitable for blow molding, thermoplastics and other processing methods, processing is convenient, application is very extensive. It can be used to process various plastic products from industrial to civilian use, packaged foods, fast food lunch boxes, non-woven fabrics, industrial and consumer cloths. Into the mouth of labor into agricultural fabrics, health fabrics, rags, hygiene products, outdoor UV protection fabrics, tent fabrics, floor mats and so on, the market is very optimistic about the prospects. Polylactic acid has good compatibility and biodegradability, and is also widely used in the medical field. For example, it can produce disposable infusion tools, exfoliation-free surgical sutures, and low polylactic acid as pharmaceutical sustained-release packaging agents. Polylactic acid is also a low-energy product that is 30% to 50% lower than a polymer produced from petroleum products. It is expected that before the onset of the non-renewable oil resource depletion period, the market price of petroleum and its derivatives will skyrocket, and renewable products will surely become tight global consumer goods. Industrial production of polylactic acid Polylactic acid production is based on lactic acid as the raw material, the traditional lactic acid fermentation mostly uses starchy raw materials. At present, the United States, France, Japan and other countries have developed and used agricultural and sideline products as raw materials to ferment and produce lactic acid, and then produce polylactic acid. The American company LLC produces polylactic acid as follows: corn starch is hydrolyzed to glucose and then anaerobicly fermented with lactobacillus. The fermentation process uses liquid caustic soda to generate lactic acid. The fermentation broth is purified and electrodialyzed to achieve a purity of 99%. .5% L-lactic acid. PLA manufacturing processes made of lactic acid include: (1) Direct polycondensation, using a solvent under vacuum to dehydrate polycondensate. (2) The non-solvent method produces lactic acid as a cyclic dimer lactide, which is polycondensed into PLA by ring-opening. A U.S. institute has successfully developed a method to convert the scrapped potatoes after cheese production into glucose syrup, ferment them with bacteria into lactic acid fermentation liquor, electrodialysis separation, heating to evaporate water, and obtain polylactic acid that can be made into films and coatings. As a fresh-keeping bag and in place of polyethylene and waterproof wax packaging materials. The Erstein sugar factory and a university in France developed sugar beets as raw materials, first decomposed into monosaccharides, fermented to produce lactic acid, and then used chemical methods to polymerize lactic acid into polylactic acid, and also used industrial sugar-making processes to degrade waste sugar. Liquid to produce polylactic acid, the production cost has dropped significantly. Japan's Bell spinning company uses corn as raw material to ferment and produce polylactic acid, using polylactic acid to make biodegradable foam material. The process is to mix a special additive in polylactic acid, control its molecular structure, make it become easily foamable particles, and then add the organic compound foaming agent made of carbohydrate, and shape it in the molding machine. High-pressure steam is heated to a foamed material. The strength of the material, such as compressive stress, cushioning, and chemical resistance, is the same as that of polystyrene plastics. It does not pollute the environment after incineration, but it can also be fattened. According to media reports, Hycail Materials Industries, a European manufacturer of biodegradable plastics, recently made breakthroughs in improving the development and production of polylactic acid (PLA) temperature resistance. The poor high temperature resistance of PLA materials has always been a difficult problem to solve, and the new Hycail XM 1020 material can withstand temperatures up to 200°C without deformation. Even materials containing fats and liquid foods are not deformed or stress-damaged by microwave heating. It can withstand microwave heating at 205°C for 30 minutes. At present, Hycail PLA's production facilities in the Netherlands have produced hundreds of tons per year, and Hycail plans to build large-scale installations with a capacity of at least 25,000 tons per year. The polylactic acid production line currently built in China is generally small in size, usually tens of tons or hundreds of tons; fortunately, the scale of the proposed project or expansion project is as large as 10,000 tons. It is believed that in the near future, polylactic acid will replace traditional products in many areas of our country and exert its biodegradable function. Polylactic acid, a biopolymer material developed by the School of Materials and Science Engineering of Tongji University, recently received an Innovation Award at the Industrial Expo. This polylactic acid, commonly known as "corn plastic," is considered the terminator of "white pollution" brought by traditional chemical plastics. The raw material for polylactic acid is not only corn, but many other crops can be used to extract lactic acid. Therefore, it is more appropriate to refer to polylactic acid as "biomass plastic." With the depletion of various petrochemical resources such as petroleum and coal, the development and application of biological resources has attracted the attention of scientists around the world, and has also stimulated the vigorous development of the biomass industry. This emerging industry is the use of renewable or recycled organic materials such as crops, livestock and poultry excrement as raw materials to produce fuels, energy, and biomass materials (including plastics, fibers, etc.) through biochemical methods. According to professionals, only one company in the United States can produce polylactic acid on a large scale. The company's production process adopts a "two-step method" and the production cost is very high. The price per ton is about 3,000 US dollars. Although the prices are high, they can't stop the demand of the market, especially the developed countries spend more money to promote. In China, such high prices are obviously unacceptable to the market. How to reduce the cost of production through technological improvements and to produce cheap polylactic acid has become the focus of research. At the same time, the subject of the School of Materials and Science Engineering of Tongji University was also listed as one of the first batch of 29 "science and education-based cities" industrialization projects in Shanghai. After 8 years of research and 1 year of industrialization, the School of Materials and Science Engineering at Tongji University has finally developed a "one-step method" to develop the advanced technology of polylactic acid. Through the organic combination of bio-engineering technology and polymer synthesis technology, the “one-step method†can synthesize lactic acid extracted from corn into polylactic acid particles, and the production cost is greatly reduced. The ex-factory price is approximately 10,000 yuan per ton, close to the current chemical plastics. The price of particles. As a result, polylactic acid has the conditions for promotion and industrialization in China. Development Significance of Polylactic Acid The significance of polylactic acid in China is not only reflected in environmental protection, but also positive for the construction of circular economy and conservation-oriented society. The raw materials for chemical plastics are extracted from non-renewable fossil resources --- petroleum, which is becoming a scarce consumptive resource. The polylactic acid extracted from plants obviously has inexhaustible supply of raw materials, and the decomposed polylactic acid will be absorbed by the plants to form a material recycling. Therefore, polylactic acid is known as a plastic that is easily biodegraded under the global environment. And compared to chemical plastics, polylactic acid will not produce more carbon dioxide. Because the raw material of polylactic acid --- corn in the growth process through the photosynthesis of plants, it will consume carbon dioxide. In addition, the industrialization of polylactic acid will greatly increase the added value of crops. Taking corn as an example, China has an annual inventory of more than 30 million tons, and most of it is used as feed. If it is used to produce polylactic acid, a "corn-lactic acid-polylactic acid-copolymer blend-various applied products" will be formed. The industrial chain can greatly increase the price of corn and increase the income of farmers. Previously, polylactic acid has been used in packaging or tableware for agricultural films and convenience foods. However, compared with plastics made of oil and natural gas, the polylactic acid plastics produced by plants are expensive, and they deform at about 60°C. Due to these shortcomings, this material has so far been difficult to popularize. Despite this, people are still very optimistic about polylactic acid. One important reason is that it uses plants as raw materials. Polylactic acid may make a huge contribution to solving the world's two major problems of depletion of fossil fuels and global warming. In order to get rid of the reliance on increasingly depleted petroleum resources, vigorously developing environmentally friendly biodegradable polymers to replace petroleum-based plastic products has become a hot spot in current research and development. After years of research, some well-known scientific research institutions and companies have introduced a variety of biodegradable polymers. Among many biodegradable polymers, PLA has just entered the industrialization process and has won the attention and favor of the global plastics industry for its outstanding mechanical properties, wide application fields, and remarkable environmental and social benefits. It is estimated that between 2005 and 2010, as the production cost of polylactic acid approaches the cost of traditional plastics, and the market application will be vigorously expanded, popularization will enter a peak period, and the polylactic acid construction boom will develop globally. According to forecast, according to proven oil reserves and current consumption, global oil resources can only be consumed for more than 30 years. It is expected that before the onset of the non-renewable oil resource depletion period, the market price of petroleum and its derivatives will skyrocket, and renewable products will surely become tight global consumer goods. As a result, polylactic acid has brought about a golden market opportunity and a huge consumption potential. According to statistics, in the world, the consumption of plastics in 2000 was about 115 million tons. If the consumption of alternative petroleum-based polymers is 10% to 20% after 10 to 20 years, the global demand for polylactic acid will reach 11.5 million to 23 million tons per year. . Reducing costs and increasing competitiveness with existing plastics are still issues that need to be addressed in the future development of the polylactic acid industry. In early 1998, the market price of polylactic acid decreased from US$5,000/tonne to US$2,500/tonne. The current price is 10% to 15% cheaper than that of PET (polyethylene terephthalate). It is expected that after 7 years, the polylactic acid price will be Expect to be able to compete with all thermoplastic resins. Cargill Dow plans to invest $1 billion in the next 10 years. In 2006 and 2009, it will build another two units with a total capacity of 450,000 tons/year. Japan is an important application development area and application market for polylactic acid in the world. It is mainly used in packaging containers, agriculture, construction, and sports clothing and bedding for textiles. Japan called biodegradable plastic green plastic. In order to expand its market share, Cargill Dow's Lactic Acid announced the cooperation with Mitsui Chemicals to develop the application of polylactic acid. In the future, it will also cooperate with Japanese Bell Spinning Fibers, Mitsubishi Plastics, Eureka, Kuraray and other users to conduct cooperative research and explore new applications. It is predicted that the market demand for biodegradable polymers in North America will be strong in the next few years. The average annual growth rate in 2005 will be 7%, reaching 1.6 million tons, of which the demand for polylactic acid will be nearly 1 million tons. Not long ago, the U.S. Department of Energy awarded $2 million to Cargill Dow for use in fermentation research using renewable resources. Another $2 million is used for the study of fermentation of polylactic acid and other products from cereal fibers, plant stalks, etc. According to China's sustainable development strategy, using renewable resources as raw materials, the use of biotechnology to produce biodegradable polylactic acid has great market potential. Deep processing of grain products and production of high value-added products are major measures to achieve leap-forward economic development. China is the world's largest country of grain production, ranking second in the world after corn production. The use of corn as a raw material, the introduction of foreign advanced technology, the construction of large-scale polylactic acid plant has a lot of room for development.