1. 1 water-soluble film
The main features are:
(1) has good mechanical properties, can be heat sealed and has high heat sealing strength;
(2) Safety-it can prevent users from directly contacting the packaged articles, and can be used to package articles harmful to human body;
(3) Environmental protection-complete degradation. The final products of degradation are CO2 and H2O, which can be completely solved.
Treatment of packaging waste;
(4) Anti-counterfeiting-with anti-counterfeiting function, it can be used as the best weapon for anti-counterfeiting of high-quality products and prolong the life cycle of high-quality products.
1.2 black and white film (black/white film)
The main features are:
(1) heat sealability-excellent heat sealability;
(2) oxygen barrier layer-it has a unique function of avoiding light and blocking oxygen;
(3) Low cost performance.
The appearance of black and white film of fresh milk in China market will be the development direction of fresh milk packaging in the next few years. At present, the black and white film of fresh milk packaging used by china dairy companies depends on imports.
The black and white film used for fresh-keeping packaging is generally made of three or four layers of different polyethylene and black and white masterbatch. Generally, metallocene linear low density polyethylene (MLLDPE) with high and uniform branching and narrow molecular weight distribution is used as the heat sealing layer to improve the heat sealing performance of black and white film packaging.
1.3 active plastic packaging film
The main features are:
(1) breathability-let the produced carbon dioxide and oxygen permeate, and keep perishable products in sleep;
(2) bactericidal performance-the film contains a small amount of slow-release bactericide, which can also prevent the growth of mold, and the fresh-keeping period of packaged fruits and vegetables can be extended by more than 1 time;
(3) Preservation-it can absorb ethylene that can promote the ripening of fruits and vegetables and keep the periphery of perishable products moist. Perishable products such as packaged fresh fruits, vegetables and flowers can be kept fresh for several weeks, which solves the problem of long-distance transportation of these products.
1.4 antibacterial plastic film
The main features are:
(1) Safe use-reduce the disposable preservatives in the film, so that consumers can reduce the intake of preservatives;
(2) Quality assurance-can extend the shelf life of food. Plastic films containing antibacterial agents can gradually release preservatives into food within a certain period of time, which not only effectively ensures the quality of food.
2 Development direction of packaging film
Colored plastic flexible packaging has become the fastest developing product in the packaging industry because of its excellent comprehensive performance, reasonable price and environmental protection. It constantly replaces other packaging, and its use is expanding day by day. It is expected to maintain a good growth momentum in the next few years. In order to improve the market competitiveness, plastic flexible packaging is developing towards thin-walled and high-performance, and the demand for multi-layer composite films is growing faster than that of ordinary single-layer films. Multi-layer composite films such as polyethylene film and polypropylene composite cast film have the most promising application prospects in packaging.
Development trend of cast film in the third and fourth years
(1) Material reduction-In order to meet the requirements of packaging reduction and environmental protection, the packaging materials are thinned and lightened;
(2) Safe use-pay attention to human health, and the materials should be safe;
(3) Intelligent products-with many functions such as fresh-keeping, anti-corrosion, anti-bacteria, anti-counterfeiting and prolonging the shelf life;
(4) Equipment efficiency-packaging equipment is developing towards large-scale, rapid, efficient and automatic.
Green chemistry is also called "environmentally friendly chemistry", "environmentally friendly chemistry" and "clean chemistry". Green chemistry is a "new chemical baby" produced and developed in recent years. 1984 "waste minimization" is put forward by the us environmental protection agency, which is the original idea of green chemistry. 1989 The US Environmental Protection Agency put forward the concept of "pollution prevention". 1990, the federal government of the United States passed the Pollution Prevention Action Act, which established pollution prevention as a national policy, and the word "green chemistry" appeared for the first time in the provisions of this law. 1992, the us environmental protection agency issued the pollution prevention strategy. From 65438 to 0995, the US government established the "Presidential Green Chemistry Challenge Award". From 65438 to 0999, the Royal Society of Chemistry founded the first international journal of green chemistry, which marked the official appearance of green chemistry. China is also closely following the forefront of chemical development in the world. 1995, the Department of Chemistry, Chinese Academy of Sciences determined the green chemistry and technical consultation topic for academicians.
One of the core contents of green chemistry is "atomic economy", that is, making full use of every atom in reactants, thus making full use of resources and preventing pollution. The concept of atomic economy was put forward by Trost, a famous American organic chemist, in 199 1 (for which he won the academic prize of 1998 Presidential Green Chemistry Challenge Award). The atom utilization ratio is used to measure the atom economy of the reaction. In organic synthesis, every atom of the raw material molecule is used to the maximum extent to combine with the target molecule to achieve zero emission.
12 principles of green chemistry
In order to briefly describe the main viewpoints of green chemistry, P.T.Anastas and J.C.Waner put forward the principle of 12 green chemistry:
1. prevention-it is much better to prevent waste from being generated than to treat and purify it after it is generated.
2. Atomic economy-design such a synthetic scheme so that the materials used in the reaction process can enter the final product to the maximum extent.
3. less harmful synthetic reaction-design the synthetic process, only select or produce substances that are less toxic to human body or environment, preferably non-toxic.
4. The generated chemical product is safe-the product of the designed chemical reaction not only has the required performance, but also has the minimum toxicity.
5. Solvents and auxiliary materials are safer-try not to use auxiliary materials (such as solvents or precipitants). When not in use, try to be harmless.
6. The use of energy should pay attention to efficiency-try to reduce the energy needed in the chemical process as much as possible, and also consider the impact on the environment and economic benefits. The synthesis process is carried out at atmospheric temperature and pressure as much as possible.
7. Use recyclable raw materials-as long as it is technically and economically feasible, raw materials should be recycled rather than discarded.
8. Minimize derivatives-redundant derivative reactions (temporarily changing physical and chemical processes in order to protect groups or remove protection) should be avoided or reduced as much as possible, because these steps need to add some reactants and also produce waste.
9. Catalysis-Catalysts (as selective as possible) are more important than stoichiometric reactants.
10. design degradation-the products produced according to the design can be decomposed into harmless degradation products after their effective functions are completed, and will not continue to exist in the environment.
1 1. The pollution prevention process can be analyzed in real time-analytical methods must be continuously developed, and the real-time analysis and process should be monitored, especially the control of harmful substances.
12. accident prevention-in the chemical process, the selection of reactants (including their specific forms) should focus on minimizing the possibility of chemical accidents including release, explosion and fire. 5R resource use theory.
In recent years, breakthroughs have been made in the field of biotechnology, such as the exponential growth of GenBank and PDB sequences. The establishment of efficient gene cloning and expression platform can effectively improve the application of enzyme-directed evolution technology in biocatalysts in terms of specificity, selectivity and stability. These advances make biocatalysis more and more important in chemical synthesis. The successful application of biocatalysis in the following fields is reviewed: developing economical chemical enzymatic synthesis process in drug production, minimizing the generation of waste and the application of dangerous reagents in green chemistry, and modifying natural products in natural chemistry to find new drugs with better biological activity.
With the extensive use of packaging materials, the disposal of some waste packaging materials is a difficult problem to be solved urgently. Generally, there are three ways to treat waste packaging materials: landfill, incineration and recycling. Landfill method not only pollutes the land, but also wastes a lot of land; Burning releases a lot of toxic gases and pollutes the atmosphere; The recycling method is troublesome to collect and sort out, and the practical application is difficult. Therefore, it is very necessary to develop suitable packaging materials and methods.
Biodegradation is a new method to solve the problem of waste packaging materials. It has the characteristics of convenient storage and transportation and wide application range. Among biodegradable packaging materials, biodegradable packaging plastic is a common packaging material.
1 biodegradable plastics and their classification biodegradable plastics refer to plastics that can be degraded by microorganisms in the presence of water and nutrients. Biodegradable plastics can be divided into complete biodegradation and biodegradation according to their mechanisms and failure forms.
1. 1 Fully biodegradable plastics refer to plastic materials whose molecular structure can be completely decomposed into simple compounds by microorganisms or enzymes. At present, there are mainly natural polymers, synthetic materials, microbial synthetic materials and plant transgenic materials.
1.2 biodegradable plastics biodegradable plastics are mainly degradable plastics composed of natural polymers and synthetic polymers. At present, the composite method that is expected to be applied in the packaging field is still dominated by * * * mixing, and its preferred substrates are starch and cellulose.
2 Degradation mechanism of biodegradable packaging materials 2. 1 complete biodegradation mechanism The mechanism of complete biodegradation is that biodegradable materials can be completely decomposed into low molecular compounds such as CO2, H2O or ammonia under the action of natural microorganisms such as bacteria, molds and algae. It has the characteristics of convenient storage and transportation and wide application range. There are roughly three modes of action in its degradation process.
1) the physical action of organisms leads to the mechanical destruction of substances due to the growth of biological cells; 2) the chemical action of biology, the action of microorganisms on polymers and the generation of new substances; 3) The direct action of enzymes and microbial erosion lead to the cracking or oxidative cracking of some substances.
2.2 The mechanism of biodegradation refers to the degradation of natural polymers (starch, cellulose, etc.) by microorganisms. ) and the modification of synthetic plastics (* * * poly) to overcome the shortcomings of poor strength of natural polymers and obtain biodegradable plastics.
Study on biodegradable packaging plastics biodegradable packaging plastics can be decomposed in a short time under natural environmental conditions. It is a new method to replace conventional plastics and solve "white pollution", and it is also a hot spot for scholars at home and abroad.
There are reports on biodegradable materials at home and abroad. Biodegradable packaging plastics include starch-based biodegradable plastics, biodegradable materials synthesized by microbial fermentation, fully biodegradable plastics based on cellulose, light/biodegradable plastics and synthetic biodegradable materials.
3. 1 Starch-based biodegradable plastics Starch-based biodegradable plastics have been reported. Teng Lijun et al. studied the physical and mechanical properties of starch-polyethylene biodegradable film and common plastic film polyethylene (PE) and polypropylene (CPP). The results show that the degradation rate of degradable materials used in the experiment is more than 20% within 20 ~ 30 days. Water absorption and air permeability are higher than those of ordinary films PP and CPP；; The mechanical properties can meet the use requirements. At the same time, the application prospect of biodegradable film in packaging field is analyzed. Starch plastics generally refer to plastics containing starch or its derivatives. Plastics with natural starch as filler and natural starch or its derivatives as the main component belong to this category, in which the proportion of starch can be as high as 60%. Starch-based plastics are a large class of degradable plastics.
Due to the poor compatibility of raw starch with common plastics such as PE and styrene (PS), it is often necessary to introduce compatibilizers such as ethylene and vinyl acetate to prepare * * * mixtures. Foreign countries, especially Italy, the United States and Japan, are in the ascendant in the research of starch-based polyvinyl alcohol plastics, which have their own technical characteristics and have reached a certain height. Their product production has formed a certain scale and influence. The United States uses modified starch to make biodegradable plastics with high starch content (above 90%), which is an opaque gray resin with a melting point of about 175 ~ 200℃. Extruded and granulated with a twin-screw extruder at 130℃ and molded with water as plasticizer, the properties of injection-molded products are similar to PS, but the tensile strength is better than PS, which is easy to biodegrade under aerobic and anaerobic conditions and is suitable for fast food packaging materials. * * * Mixed starch-based plastics have been mass-produced abroad, and degradable plastics have also been developed and produced by mixing gelatinized starch and PVA. In recent years, a new type of starch composite material has been developed abroad. Because it does not contain non-degradable macromolecules or small molecules, it can be completely biodegradable in the environment and can be used for disposable plastic products.
Starch-based plastics are easy to degrade, because after the starch component in the product is decomposed, many micropores appear on the surface of the product, which increases the surface area eroded by chemistry and biology and accelerates the degradation of the residual part. The higher the starch content, the faster the biodegradation rate.
3.2 Biodegradable Plastics Synthesized by Microbial Fermentation Biodegradable packaging materials made of honey and oil are both thermoplastic and completely biodegradable. Its main products are 3- hydroxybutyl ester and 3- hydroxyamyl ester of * * * polyester "Biopol" (0% ~ 30%), polyhydroxybutyrate (PHB) developed by tokyo institute of technology Resources Research Institute and aliphatic polyester developed by Massachusetts Institute of Technology (MTI). Among them, "Biopol" has made great progress. It was developed by ICI Company in the UK from 1976 and industrialized from 1990. The thermal decomposition temperature of this product is 200℃, and it can be completely decomposed 1 year in the compost yard without secondary pollution. In addition, PHB is a substance stored in bacteria to cope with food stress, which can be activated by many bacteria and lead to rapid degradation. The research in this field has great development prospects.
3.3 Synthetic biodegradable plastics The biodegradable packaging materials manufactured by chemical synthesis method are more flexible than microbial synthesis method, and the products are easy to control. The research and development work is to synthesize substances with structures similar to natural polymers or polymers with easily biodegradable functional groups. At present, main products are polylactic acid (PLA) and polycaprolactone (PCL). Polylactic acid is a polyhydroxy acid. As a biological product, it has good biodegradability, good biocompatibility and bioabsorbability [1 1], and will not leave any environmental problems after degradation. Its manufacturers mainly include Shimadzu Corporation of Japan, Mitsui East Asia Chemical Company, Cargill Company of the United States and Ecochem Company. 65438-0998 Danone of Germany cooperated with CargillDow to develop a rapidly degradable Danone yogurt cup with polylactic acid as raw material. Zhong Fang Synthetic Fiber Co., Ltd. made biodegradable foam plastics from polylactic acid extracted from corn. Some physical and chemical properties of this material are the same as those of polystyrene, so it can still be processed with existing plastic foam equipment. PCL is formed by open-chain polymerization of ε -caprolactone under the action of catalyst, which will slowly decompose in soil, and can decompose 95% in one year.
Degradable plastic is one of the effective ways to solve the environmental pollution problem of disposable plastic packaging products, which can be described as green plastic packaging materials. In recent years, the process of industrialization has been rapid. It is reported that in 2000, the application of degradable polymer materials in the United States could reach 6,543,800 tons. Europe is also increasing at a rate of 400,000-500,000 tons per year; The development and production of degradable plastics in China has also become a hot spot, and some varieties have entered the market, and the prospects are in the ascendant.
At present, the industrialized degradable plastics include photodegradation, photodegradation, biodegradation and transgenic biodegradation. Although photodegradation technology is mature, the environmental factors affecting its degradation behavior are very complicated, which limits its application in packaging field.
3.4 Cellulose-based biodegradable plastics Natural polymer cellulose, like starch, is a non-thermoplastic material and cannot be processed by conventional processing methods. By mixing or chemical modification, the hydrogen bond of cellulose is broken, and the hydroxyl groups on cellulose molecules react to obtain cellulose derivatives, which are mixed with unmodified cellulose or native starch to prepare degradable plastics with different properties, and processed into various products or films with good mechanical properties, low production cost and fast degradation speed. It is found that the degradable plastics made by mixing 30% ~ 85% of degradable cellulose derivatives with 30% ~ 70% of unmodified cellulose or raw starch can be made into various products or films by injection molding and tape casting. Its performance, degradation speed and production cost have the potential to be popularized and applied in the packaging field, and can be used for the packaging of food and daily necessities.
3.5 Light/Biodegradable Plastics In biodegradable plastics, the degradation behavior of materials must be carried out in an environmental medium with biological activity. Adding a proper amount of photosensitizer can make plastics both photodegradable and biodegradable, and under certain conditions, the controllability of degradation rate is obviously improved. Therefore, the development of photobiodegradable plastics has attracted wide attention at home and abroad. It has become one of the important research and development directions of degradable plastics. In recent years, people have made extensive research on the degradation speed, control, completeness, environmental safety of degradation products and evaluation methods of degraded materials, and made some breakthroughs. The application of this kind of materials in the field of packaging will have broad development prospects.
China news agency, Beijing, November 10th (Reporter Yan Xiaohong) The reporter learned from today's "High-level Forum on Organic and Green Food Development" that China's organic and green food industry has broad prospects for development.
Approved by the Ministry of Commerce, the first China International Organic and Green Food Expo, co-sponsored by China People, Foreign Trade Development Bureau of the Ministry of Commerce and China Cereals, Oils and Foodstuffs Group, was held in Beijing today. As one of the theme activities of the exhibition, the "High-level Forum on Organic Food and Green Food Development" discussed the role of organic agriculture in China's agricultural development and strong country.
The countermeasures of international cooperation and cultivating the international market of green food are discussed in depth.
According to the forum, since 1970s, organic agriculture/eco-agriculture, which mainly aims at eco-environmental protection and safe agricultural production, has developed rapidly in Europe, the United States, Japan and some developing countries. At the same time, the development of China's organic food industry is still in the primary stage, and its market share is still small compared with that of developed countries, but it is developing rapidly. At present, the base area of organic food production certification in China is about 300,000 hectares.
At the same time, the global consumption of organic food has greatly increased. Although the proportion of retail sales of organic food in the whole food industry is very small at present, it has great growth potential. It is predicted that the global retail sales of organic food will reach $80 billion in 2008. Under the national policy background that solving the "three rural issues" is the top priority of economic work, the development prospect of organic food and green food industry in China is infinitely broad. March 2005 14: It is estimated that the global annual output value of nanotechnology has reached 50 billion US dollars. At present, governments and large enterprises in developed countries have launched research plans to develop nanotechnology and nano-plans. The United States regards nanotechnology as the core of the next industrial revolution. At the beginning of 200 1, nanotechnology was listed as a national strategic goal. The investment in basic research of nanotechnology has increased from 1 1997 to more than $100 million to nearly $500 million in 200 1 year, and it is ready to take the lead in this field like microelectronics technology. Japan has also set up a center for nanomaterials, which has included nanotechnology in the research and development focus of the new five-year basic plan for science and technology, and listed new material technologies represented by nanotechnology as four key development areas, including life sciences, information and communication, and environmental protection. In Germany, nano-materials have also been included in the strategic field of scientific research in the 2 1 century, and 19 institutions across the country have established nanotechnology research networks. With mankind entering the 2 1 century, the development of nanotechnology will make greater contributions to the development of society, the improvement of living environment and the protection of human health. In a sense, 2 1 century will be a nanometer century.
Due to the wide application of surface nanotechnology, short industrialization cycle and high added value, the high-tech and high-tech products formed and the transformation and upgrading of traditional industries and products have excellent industrialization market prospects.
In terms of nano-functional and structural materials, we should make full use of the unusual optical, electrical, magnetic, mechanical, sensitive, catalytic and chemical characteristics of nano-materials, develop new high-tech products and modify traditional materials; Focus on breaking through the key technologies, detection technologies and characterization technologies of industrialization of various nano-functional and structural materials. Multifunctional nano-composite materials and high-performance nano-cemented carbide provide broad opportunities for the leap-forward development of chemical industry, building materials, light industry, metallurgy and other industries. It is predicted that during the tenth five-year plan period, the industrialization of various nano-materials may form a number of large enterprises or enterprise groups, which will have an important impact on the national economy; The application of nanotechnology has gradually penetrated into various fields involving the national economy and people's livelihood, which will produce new economic growth points.
The application and development of nanotechnology in coatings industry has promoted the upgrading of coatings and created a breakthrough new era in which coatings have become truly green products.
China's annual housing completion area is about/kloc-0.8 billion square meters, with an annual growth rate of about 3%. If 65.438+08 billion square meters of buildings are all decorated with architectural coatings, the total demand for architectural coatings will be nearly 3 million tons, about 20-30 billion yuan. At present, the annual output of architectural coatings in China is only over 600,000 tons, and now the annual output of coatings in the world is 25 million tons, and each person consumes 4 kilograms a year, which is110 of developed countries. The average annual consumption of coatings in China is only 1.5 kg. Therefore, architectural coatings have a very broad development prospect.
Nano-coating is recognized as a special product for the construction project of Beijing Olympic Village, which shows the application value of the coating in the construction field. It uses unique photocatalytic technology to decompose and eliminate toxic gases in the air. It can absorb and eliminate harmful gases such as formaldehyde and ammonia, and make the indoor air fresher. After testing, the killing rate of various molds is over 99%, and it has long-term anti-mildew and anti-algae effects. Nano-modified interior wall paint is actually an advanced sanitary paint, which is suitable for painting in families, hospitals, hotels and schools. Nano-modified exterior wall coatings have the advantages of low surface tension, strong adhesion, high film hardness, good toughness, excellent self-cleaning function, strong dust and dirt adhesion resistance, excellent hydrophobicity and easy cleaning of dirt. The washability is more than 15000 times, with good light and color retention and strong ultraviolet resistance. Service life exceeds 15 years. Small particle size, can penetrate into the wall, react with silicate substances on the wall to make it firmly combined, strong adhesion, no peeling, no shedding, anti-aging Its nano-antifreezing coating not only has various excellent properties of nano-coating, but also can be used normally at-10℃ to -25℃. It breaks through the requirement that the wall humidity of building coatings should be below 10%, shortens the construction period, improves efficiency and creates high quality, so it is welcomed by construction units.
At present, the application of nano-materials to modify coatings is still in the primary stage, and the technology and process are not mature enough, which needs to be explored and improved. However, some improved test results of various properties of coatings prove that the market prospect of nano-modified coatings is very good. Synthetic rubber plays an important role in national defense, automobile, medicine, environmental protection and other fields with its unique properties. At present, the basic situation of new synthetic rubber varieties in China is that there is still a certain gap compared with foreign varieties in scale, production technology level, product brand and performance. There are few varieties of products, production has not formed scale, products have not formed serialization, and some varieties need to rely on imports. This restricts and affects the development of downstream products to high performance to a considerable extent. The rapid development of China's automobile industry puts forward higher requirements for the quality, performance and quantity of rubber products, which will further stimulate and promote the development of China's new synthetic rubber industry. Establishing a complete upstream and downstream industrial chain of new synthetic rubber will certainly promote the development of China's synthetic rubber industry.