Who can tell me the main components, manufacturing methods and degradation process of degradable plastic bags?

Biodegradable plastics refer to a kind of plastics degraded by microorganisms such as bacteria, fungi and algae existing in nature. The ideal biodegradable plastic is a kind of polymer material with excellent performance. After being discarded, it can be completely decomposed by environmental microorganisms and finally inorganic, becoming a part of the natural carbon cycle. "Paper" is a typical biodegradable material, and "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 complete biodegradable plastics and destructive biodegradable plastics.

Destructive biodegradable plastics: At present, destructive biodegradable plastics mainly include starch modified (or filled) polyethylene PE, polypropylene PP, polyvinyl chloride PVC, polystyrene PS and so on.

Biodegradable plastics: Biodegradable plastics are mainly made from natural polymers (such as starch, cellulose and chitin) or agricultural and sideline products through microbial fermentation or synthesis of biodegradable polymers, such as thermoplastic starch plastics, aliphatic polyester, polylactic acid, starch/polyvinyl alcohol, etc.

Present situation and development trend of biodegradable plastics at home and abroad

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Judging from the classification of raw materials, biodegradable plastics have at least the following types:

1. polycaprolactone

This plastic has good biodegradability, and its melting point is 62℃. Microorganisms that decompose it are widely distributed under aerobic or anaerobic conditions. As a biodegradable material, it can be mixed with starch and cellulose or polymerized with lactic acid.

2. Poly (butylene succinate) and its polymer

The technology of producing various high molecular weight polyesters (melting point 1 14℃) from PBS has reached the level of industrial production. Japan's Mitsubishi Chemical and Showa Polymer Company have started industrial production, with a scale of about 1000 tons.

The Institute of Physics and Chemistry of Chinese Academy of Sciences is also conducting research on the synthesis of polybutylene succinate polyester. At present, the Institute of Physics and Chemistry of Chinese Academy of Sciences is preparing to build an annual production line of 1 10,000 tons of PBS, and Guangdong Blonde Company has built an annual production line of 1 10,000 tons.

3. Polylactic acid

Natureworks Company of the United States has done active and effective work in improving the production process of polylactic acid, and developed the production of polylactic acid by fermentation of glucose in corn, with an annual production capacity of1.4000 tons. UNITIKA company in Japan has developed and produced a variety of products, among which canvas, tray and tableware are widely used in Aichi World Expo in Japan.

At present, Zhejiang Haisheng Biodegradable Plastics Co., Ltd. (the production line scale is 5,000 kilotons/year) is industrialized in China, and the pilot units are Shanghai Tongjieliang Biomaterials Co., Ltd. and Jiangsu Jiuding Group.

4. polyhydroxyalkanoate

At present, the industrialized production abroad is mainly in the United States and Brazil. At present, the domestic production unit is Ningbo Tianan Biomaterials Co., Ltd. (scale 2000 tons/year), and the pilot units are Jiangsu Nantian Group Co., Ltd. and Tianjin Guo Yun Biotechnology Co., Ltd.

The technology of producing biodegradable plastics by mixing aliphatic polyester and starch with biodegradable plastics obtained from renewable resources has also been successfully studied. In Europe and America, the mixture of starch and aliphatic polyester is widely used to produce garbage bags and other products. The largest and best-selling company in the world is Novamont of Italy, with its trade name Mater-bi, and its products are widely used in Europe and the United States.

There are many domestic scientific research and production units, among which the industrialized units are Wuhan Gorgeous Technology Co., Ltd. (8000 tons/year), Zhejiang Fahua Ecological Technology Co., Ltd. (8000 tons/year), Zhejiang Tianhe Ecological Technology Co., Ltd. (5000 tons/year), Fujian Baishida Biomaterials Co., Ltd. (2000 tons/year) and Zhaoqing Fanghua Degradable Plastics Co., Ltd. (5000 tons)

5. Aliphatic aromatic polyester

The aliphatic aromatic random polyester (Ecoflex) produced by BASF Company in Germany consists of adipic acid, terephthalic acid and 1, 4- butanediol. The current production capacity is 6.5438+0.4 million tons/year. At the same time, biodegradable plastic products based on polyester and starch were developed.

6. PVA biodegradable plastics

For example, in the 1990s, MaterBi products from NOVMANT, Italy, mainly added PVA to starch, which can be blown and processed into other products. Polyvinyl alcohol (PVA) materials need to be modified to have good biodegradability. The Research Institute of Light Industrial Plastics Processing and Application of Beijing Technology and Business University has made some achievements in this respect.

7. Carbon dioxide polymer

Abroad, Japan and the United States are the first countries to study carbon dioxide polymers, but there has been no industrial production.

Inner Mongolia Meng Xi Group Company has built a device with an annual output of 3000 tons of carbon dioxide/epoxy polymer resin by using the technology of Changchun Institute of Applied Chemistry, and its products are mainly used for packaging and medical materials. The low molecular weight carbon dioxide polymer technology developed by Dr. Chen Liban from Guangzhou Institute of Chemistry, Chinese Academy of Sciences has been put into production in Taixing, Jiangsu. The variety is low molecular weight carbon dioxide/epoxy polymer, which is used as the raw material of polyurethane foaming material and used for packaging household appliances. Using the technology of Professor Meng of Sun Yat-sen University, Henan Tianguan Group has built a pilot production line of carbon dioxide polymer, which is expected to be put into trial production this year.

Others such as chitin, polyamide, polyaspartic acid, polysaccharide and cellulose are under development.

Present situation and development trend

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According to the data of Japan Biodegradable Plastics Research Association, the output of biodegradable plastics in Japan was about 10000 tons in 2002, 20,000 tons in 2003 and 40,000 tons in 2005, and it is expected to reach10 ~ 200,000 tons by 20 10.

According to the data of the European Bioplastics Association, the figure of 200 1 shows that the consumption of biodegradable products in the EU is 25,000-30,000 tons, while the consumption of traditional polymers is as high as 35 million tons. The European Bioplastics Association predicts that the consumption of traditional polymers will reach 55 million tons in 20 10, and the consumption of biodegradable plastics will reach 500 ~100000 tons. Biodegradable materials may eventually occupy the market share of 10%. The proportion of raw materials using renewable resources in biodegradable materials will account for more than 90%.

According to the statistics of the Professional Committee of Degradable Plastics of China Plastics Association, the consumption of biodegradable materials in China in 2003 was about10.5 million tons, of which the biodegradable polymer without starch was about10.5 million tons. In 2005, there were about 30 enterprises engaged in biodegradable plastics, with a production capacity of 60,000 tons/year, actual output of about 30,000 tons, domestic market demand of about 50,000 tons, foreign imports of 6,543,800 tons and exports of 20,000 tons. It is estimated that the production capacity of 20 10 will reach about 250,000 tons.

Domestic and foreign policies

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Some developed countries also use degradable disposable tableware under the guidance of circular economy, such as the disposable fast food box made of potatoes and corn, which was trial-produced in Sweden in the late 1980s, and the toothpick made of glutinous rice was forced to be used in South Korea by law. In Europe, the standard EN 13432 on biodegradable compost plastics has been formulated, that is, the requirements for testing and final evaluation of compost and biodegradable recycled packaging materials, and other laws and regulations on promoting organic waste composting are being actively formulated and prepared. 65438-0996 The US government established the Presidential Green Chemistry Challenge Award to encourage the development of biodegradable plastics industry. 1989, New York State banned the use of non-biodegradable vegetable bags, subsidized the manufacturers of degradable plastics, and asked citizens to separate renewable and non-renewable garbage, or they would be fined $500.

Other countries have taken similar measures: India has banned the use of plastic packaging in dairy industry; South African law has completely banned the use of plastic packaging bags. With the development of legislation in various countries, biodegradable new packaging materials are expected to become more and more popular.

In China, with the deepening of understanding of degradable plastics, the strategic role of this material and its industry in China's sustainable development has been fully realized. The popularization and application prospect of biodegradable plastics is broad. In 2004, China passed the Renewable Energy Law (Draft) and the Solid Waste Law (Revised) to encourage the utilization of renewable biomass energy and the popularization and application of degradable plastics. In the document No.40 of the National Development and Reform Commission in 2005, it is also clear that the use and popularization of biodegradable plastics should be encouraged. In 2006, the National Development and Reform Commission launched a special fund project to promote the development of biodegradable materials.

Problems and difficulties in the development of biodegradable plastics

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However, although there are many studies and reports on degradable plastics, many specific problems cannot be solved, which is extremely difficult to popularize and the prospect is not optimistic. The reasons are as follows: firstly, the bearing capacity of degradable plastic bags is low, which can not meet the requirements of customers for loading more things and reuse; Second, the color of degradable plastic bags is dim and yellow, and the transparency is low, which gives people a feeling that they are not clean enough and ugly, and it is unsafe to use; Third, the price is high. Because the merchants give it away for free, the cost is unacceptable.

Another example is to solve the environmental pollution problem caused by EPS fast food box lunch. Try to use paper lunch boxes or degradable plastic lunch boxes instead. However, due to the following reasons, it is extremely difficult to popularize: first, EPS has high strength, light weight and good thermal insulation; Second, the price of paper lunch box is 0.5 ~ 2.5 times that of 65438+EPS; Third, even if the degradable PP lunch box is used, its performance is not as good as EPS. Recently, the relevant departments of our country require that plant fiber be used instead of EPS to make disposable tableware. However, due to the use of polymer hot melt adhesive in the molding process of this plant fiber tableware, there are still problems in dealing with and controlling the pesticide content remaining in the plant fiber tableware.

Therefore, there is still a long way to go to develop and study degradable plastics.

Suggestions on policies and measures for industrial development

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(A) to speed up product application research and development and industrialization

At present, the performance of biodegradable plastic products can not fully meet the needs of consumers. Although there are many varieties on the market at present, the mechanical properties and processability of each material are only outstanding in one aspect, and there are still some shortcomings in comprehensive properties, which will be one of the bottlenecks restricting its market application and promotion. While developing biodegradable plastic products, domestic enterprises should pay attention to accelerating the development of innovative products and uses with independent intellectual property rights. Due to the early development, production and application of biodegradable plastic products abroad, many patents have been applied, which has caused certain technical barriers for domestic enterprises to develop new products. Take the patent of polylactic acid as an example. In 2005, there were more than 1700 patents on polylactic acid abroad, but only 145 patents were published in China, and more than half of them were patents of foreign companies. Therefore, domestic enterprises should strengthen the development of independent intellectual property products.

(2) Strengthen research on product processing and development.

Secondly, at present, the strength of product processing research in China is still very weak. Most enterprises focus on material synthesis and ignore product processing and development. Some tableware made of biodegradable plastics are far from traditional plastic products in terms of heat resistance, water resistance and mechanical strength, which is precisely the key to the large-scale commercialization of biodegradable plastics.

(3) Improve the garbage recycling system and promote the recycling process of biodegradable plastics.

The lack of a complete recycling system also restricts the further promotion of products. Therefore, it is necessary to clearly mark the degraded plastics and then recycle them. Can be collected repeatedly and then molded into products; For those that cannot be reused, reasonable treatment methods should be considered. In view of the degradable plastics with renewable resources such as starch added to traditional plastics, a garbage disposal system with heat energy recovery can be adopted. For biodegradable plastics, compost can be considered emphatically.

(4) Accelerate the formulation of relevant policies and regulations.

1. Special fund support

Subsidy policies are adopted for the application and development of biodegradable plastic products, including central government subsidies and local government subsidies. The central government can provide subsidies through scientific and technological research funds and interest subsidies, such as demonstrating and promoting disposable biodegradable plastic products for the Olympic Games.

The state can consider adopting low-interest loans, special loans for technological transformation and credit guarantee policies to encourage enterprises that use biomass raw materials to produce biodegradable plastics to develop their industries.

2. Tax policy

At present, it is not clearly stipulated that the import of biodegradable plastics should adopt low tax rate, and preferential tariff rate should be formulated to promote industrial development.

In order to encourage and support the development of some enterprises, preferential policies can be reduced or exempted in accordance with the new enterprise income tax regulations, such as: first, enterprises in ethnic autonomous areas that need care and encouragement can be reduced or exempted on a regular basis with the approval of the provincial people's government; Second, enterprises granted tax reduction or exemption by laws, administrative regulations and relevant provisions of the State Council shall comply with the provisions.

3. Strengthen the recycling of traditional plastics and raise the recycling tax.

Foreign countries attach great importance to the recycling of plastic products after use. For example, according to the guidance law revised by the European Commission, EU member states should raise the recycling rate of domestic packaging waste to more than 55% from 2008 to 20 15, including 60% for glass packaging, 50% for metal packaging, 22.5% for plastic packaging and 0/5% for wood packaging. The European Commission pointed out that in 200 1 year, the recycling of packaging waste alone reduced the EU's carbon dioxide emissions by 0.6%, which shows that improving the recycling rate of packaging waste can not only reduce the energy consumption of packaging materials, save the cost of building incineration plants, but also reduce the environmental pollution caused by the production process of packaging materials, which is a very practical and effective measure to reduce greenhouse gas emissions and protect the environment. Therefore, it is necessary to strengthen the traditional compulsory recycling of plastics. For disposable plastic packaging products with high recycling cost, a recycling tax of 10% ~ 100% is added. For disposable plastic packaging products that cannot be recycled, it is stipulated that biodegradable plastics must be used.

Taxation on traditional plastic disposable products has a precedent in foreign countries. In March 2002, the Irish government began to levy value-added tax on plastic bags. According to the regulations of the Irish government, customers will be charged 15 euro cents for each plastic bag they use when shopping in the market. The number of plastic bags used in Ireland is staggering. 654.38+02 billion plastic bags are distributed to shoppers free of charge every year, which adds up to 654.38+04 million tons. On average, each person consumes about 325 plastic bags every year. Within one month after the VAT on plastic bags came into effect, the consumption of plastic bags plummeted by more than 90%.

4. Appropriately restrict some disposable non-degradable packaging products made of traditional plastics.

Appropriately restrict or even prohibit some disposable non-degradable packaging products made of traditional plastics in batches, such as disposable garbage bags, shopping bags, daily necessities packaging, disposable fast tableware, disposable plastic cups, disposable food packaging containers, disposable food packaging films, disposable industrial packaging, etc.

5. Promote degradable plastics in stages and batches.

According to the industry production capacity and product production technology, the promotion progress of degradable plastics will be gradually promoted. Before 20 10, we will focus on promoting biodegradable plastics, supplemented by natural materials such as starch mixed with traditional plastics, and give policy support to these two types of products, but the former is stronger than the latter. After 20 10, biodegradable plastics will be fully popularized, and traditional plastic products with starch will no longer enjoy preferential policies.

6. Strengthen the bridge function of trade associations.

Strengthen the role of China Plastics Processing Industry Association's Professional Committee on Degradable Plastics as an industry bridge, give financial support to industry associations, use industry associations to strengthen guidance on enterprise investment, production direction and product positioning, promote exchanges inside and outside the industry, promote exchanges and trade at home and abroad, and fully carry out policy research and industry statistics.