Current situation and trend of plastic film industry in China

The output of plastic film in China accounts for about 20% of the total output of plastic products, and it is one of the categories with rapid output growth in plastic products. With the increasing demand for plastic film in packaging, agriculture and other fields in China, it is expected that the demand for plastic film in China will increase by more than 9% every year, and its market prospect is very broad.

From the application field of plastic film (thickness: 0.06mm ~ 0.26mm) in China, the packaging industry has the largest consumption, the most varieties and the widest application, accounting for about 2/3 of its consumption, followed by agriculture, accounting for about 30%, and then there are functional films, such as microporous films

Shielding membrane, geomembrane, etc. Theoretically, almost all synthetic resins can form films, but the resins that have economic significance, become commodities and use the most are polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), ethylene / vinyl acetate (EVA), polyamide (PA) and other resins. If appropriate plastic additives are added to the resin matrix, various functional films can be prepared. The production methods of plastic film industry include extrusion method and calendering method. The extrusion method is divided into extrusion blowing, extrusion casting, extrusion stretching (also known as secondary molding), etc. at present, extrusion method is the most widely used, especially for the processing of polyolefin film, and calendering method is mainly used in the production of some PVC films.

General situation and development trend of plastic packaging film industry

一、 Industry Overview

Among plastic packaging materials, the market demand for film materials increased the most, accounting for about 46% of the total plastic packaging materials. Plastic packaging film mainly includes: heat shrinkable packaging film, wrapping packaging film, sterile food packaging film, fruit and vegetable fresh-keeping film, liquid packaging film, etc. With the continuous improvement of the equipment level of China's plastic film industry, some have reached the advanced level of developed countries, and a number of new products have emerged. For example, as the base material of composite packaging, biaxial tensile film has not only overcome the situation of long-term import, but also exports about 300000 tons every year, earning foreign exchange of more than 3 billion US dollars. The number of large-scale packaging film manufacturing enterprises in China has developed rapidly, reaching 2240 at present, among which a number of industry leading enterprises have emerged, such as Jiangyin Shenda group, Zhejiang dadongnan plastic group, Foshan Oriental packaging materials company, Foshan DuPont Hongji packaging materials company, Foshan Plastics Group Co., Ltd Guangzhou Hongshun Plastic Industry Co., Ltd. and Nanya plastic industry (Guangzhou) Co., Ltd. play a decisive role in this industry.

1. Heat shrinkable packaging film

At present, PVC heat shrinkable films are gradually decreasing in China, while PE, PP, pet, PVDC, PA and other heat shrinkable films are developing rapidly, and multilayer coextrusion composite heat shrinkable films have appeared. Take the three-layer coextrusion heat shrinkable film, which is the most widely used at present, as an example. The film is a three-layer composite heat shrinkable film with linear low-density polyethylene as the middle layer and coextrusion polypropylene as the inner and outer layer. Because it has the advantages of PE and PP at the same time, its performance is better than that of single-layer PE film and PP film. At present, nearly 20 enterprises in the industry have produced heat shrinkable films, and their production capacity has grown from 40000 tons to nearly 80000 tons, among which Baoshuo group, Tianjin Shengda, Fuzhou Jiatong and Jiangsu Nantong are the backbone enterprises. Single layer heat shrinkable packaging film can be widely used in the binding and packaging of fast food pasta, ceramic products, tea sets, mechanical parts, military machinery, hardware tools, construction and transportation materials. Multilayer heat shrinkable film is mainly used in the packaging of fresh meat and other food, as well as daily necessities, medical and health products, cultural goods and other packaging. It is predicted that the market demand for heat shrinkable packaging film in China will increase by 20% in the next five years.

2. Wrapping film

The wrapping film is self-adhesive, and no heat treatment is required in the packaging process, which saves energy and reduces the packaging cost

At the same time, the goods can be tightly wrapped into a whole, which is convenient for loading and unloading and saves transportation costs. Linear low density polyethylene LLDPE is generally used as the raw material for winding packaging film. Ethylene / butene copolymer with melt index of 1 ~ 2 and density of 0.98g/cm3 is used in China, and it is produced on single-layer or three-layer coextrusion equipment by blow molding or tape casting. The key to make the winding packaging film self-adhesive is to add chemical additives, such as compatibilizers and adhesion promoters, to two or more compatible, partially compatible or incompatible resins, which are chemically compounded or directly injected into viscous resins such as PIB. In addition to its packaging function, the wrapping packaging film also has some special functions. For example, the wrapping packaging film for forage silage can maintain the moisture and nutrients of forage, which is conducive to the absorption of nutrients by livestock, so as to promote the development of animal husbandry. The domestic research and development of grass wrapping packaging film began in 1997 with the cooperation between the Institute of light industry plastic application technology of Beijing Institute of light industry (now Beijing Industrial and Commercial University) and BP company. This technology has been successfully applied. Representative enterprises include Wuxi Rongsheng protective film factory, Guangzhou Sanda plastic packaging factory, etc

3. Sterile food packaging film

Aseptic food packaging film refers to the ultra-high temperature food packaging film that can withstand the instant sterilization of food (such as dairy products, beverages, seasonings). This packaging film can make food have a long shelf life without preservatives and cold storage. This is a new technology and one of the development directions of plastic packaging. There are two kinds of aseptic packaging for food. One is aseptic large packaging bags with a capacity of 5 ~ 1000L. The composite film for bag making is mainly composed of pet aluminized film and PE film; The other is aseptic cup packaging, which uses pp/pe/eva/pvdc/ps multi-layer coextrusion composite film, in which PP is the protective layer film, EVA is the bonding layer, and PVDC is the oxygen barrier layer.

4. Fruit and vegetable fresh-keeping film

Fruit and vegetable fresh-keeping film is used in fruit and vegetable packaging to inhibit the metabolism and nutrient loss of fruits and vegetables in the preservation process, and maintain the flavor and quality of fruits and vegetables. China is the world's largest country in the production and marketing of fruits and vegetables, and about 30% of fruits and vegetables are lost due to non preservation during storage and transportation, so the preservation of fruits and vegetables in China has great economic value. At present, polyethylene film and polypropylene film are widely used in the fresh-keeping packaging of fruits and vegetables. When choosing a suitable fresh-keeping packaging film, its permeability must be considered to maintain the appropriate concentration of oxygen and carbon dioxide in the film. At the same time, a certain amount of porous substances (such as zeolite, valley stone, etc.) can be added to absorb the ethylene gas released by fruits.

5. Metallocene catalyzed polyolefin filmPolyolefin films prepared by metallocene single center active catalysis have outstanding excellent properties, mainly including MPE, MPP, MPs, etc. The heat sealing performance, tensile performance and puncture resistance of this film are better than those of traditional films, which can effectively solve the problems of penetration cracking and heat sealing cracking in liquid packaging. It is mostly used for the heat sealing layer of liquid packaging composite films such as milk, soy sauce, shampoo and so on.

6. Biaxially stretched film

Biaxially stretched film has always played an important role in film packaging, including biaxially stretched polypropylene (BOPP), biaxially stretched polyester (BOPET), biaxially stretched nylon (BOPA), among which BOPP has the largest output. BOPP film is a new transparent packaging material developed in the 1960s. It has the advantages of light weight, non-toxic, odorless, moisture-proof, high mechanical properties, good dimensional stability, good printability and so on. It can be widely used in the packaging of food, candy, cigarettes, tea, fruit juice, milk, textiles and so on. The production methods of BOPP film include bubble tube method and stretching method, among which stretching method is used more. This method is to extrude the granular BOPP special material through the flat die, quench it on the cooling roll, and then preheat it under different conditions to pull the film vertically and horizontally, so as to greatly improve the comprehensive performance of the film. In China, the large demand for flexible packaging provides a good market opportunity for the development of BOPP industry. However, the BOPP film industry has experienced a boom of cross industry competition for the introduction of BOPP production lines since the late 1990s. It is expected that by the end of 2005, the national BOPP production capacity will exceed 2million tons, while the annual market demand is only about 900000 tons, that is, 1/2 of the production capacity will be empty. The coextrusion heat sealing biaxially oriented polypropylene film produced by Nanjing Zhongda not only maintains the heat shrinkability of BOPP, but also adopts the opening positioning technology to solve the problems of heat sealing and the adhesion between the medium film and the small film.

Among biaxial tensile materials, BOPET and BOPA films follow BOPP in market share. The domestic BOPET film industry has also experienced overheated development and irrational investment. It is expected that this oversupply will be more serious in the next few years.

7. CPP and CPE films

These two kinds of films are produced by tape casting, that is, PP or PE melt is produced by tape casting quenching to produce a non tensile, non oriented PP or PE flat extruded film. CPP and CPE films have excellent performance balance, and subsequent processes such as printing and compounding are extremely convenient. They are widely used in the field of packaging, especially CPP has a large market. At present, China has introduced more than 60 sets of CPP production lines, with a total production capacity of more than 150000 tons. CPP film is mainly used for composite packaging in the domestic market, and its largest application is aluminized film and cooking film. Among them, the laser anti-counterfeiting film of Shanghai Zijiang color printing company, the breathable cast film of Zihua company, and the antistatic CPP film of Wisteria company are all listed in the national torch project.

Pattern distribution the two major pppe film production centers in China are located in the adjacent coastal provinces / cities in eastern China - Jiangsu / Shanghai / Zhejiang - and Southeast Guangdong Province, which account for 33% and 32% of the total national production respectively. Some of China's largest film producers and converters, including Foshan Plastic Group Co., Ltd., Guangzhou Hongshun Plastic Industry Co., Ltd. and Nanya plastic industry (Guangzhou) Co., Ltd., are located in Guangdong Province. Guangdong, Zhejiang, Shandong, Jiangsu and Shanghai account for more than half of the total output of the country.

Four regions of PVC packaging in China

First, it is a high-end bag manufacturing base with foreign capital as the main body, with Shiling Town, Huadu City, Guangdong Province as the center, radiating the Pan Pearl River Delta. 90% of its products are sold to European and American markets, and it is the 'leader' of China's PVC bag industry;

The second is a medium and high-end PVC bag manufacturing base centered on Quanzhou, Fujian Province and dominated by Taiwan and Hong Kong funds. At present, there are more than 1000 enterprises, with an annual output value of more than 8billion yuan, accounting for about 40% of the national total;

Third, the Pan Yangtze River Delta region centered on Shanghai has built a Shanghai international leather goods luggage trading center. Foreign buyers place orders based on samples all year round, attracting a large number of private bag enterprises in Guangdong, Fujian and Zhejiang with strong financial strength to settle in;

Fourth, Baigou, Hebei Province, with its successful experience in operating bags since the 1990s, has leapt to the largest professional PVC bag Market in China, driving the development of relevant enterprises in surrounding provinces and promoting the formation of a new industrial chain.

二、Development trend of packaging film

After the rapid development of plastic flexible packaging in the 1990s, China has entered a period of steady development. The profit margin is gradually declining, and the competition is increasingly fierce. At present, what aspects should the development of domestic plastic flexible packaging focus on? This is a common concern in the industry. The following are the development priorities of domestic plastic flexible packaging:

The 21st century is a century of environmental protection. Building a circular economic society and taking the road of sustainable development have become the focus of global attention and urgent task. In order to meet the requirements of the new era, plastic packaging materials must not only meet the increasing requirements of the market for packaging quality and quantity, but also be developed from the starting point of technology development, which is to save resources, easy to recycle after use, easy to dispose of, or easy to be absorbed or degraded by the environment. New materials, new processes, new technologies and new products of plastic packaging are constantly emerging, and are developing in the direction of high performance and multi-function, actively adopting new raw materials and new technologies, expanding application fields, and the harmonious development of plastic packaging and environmental protection.

1. High barrier packaging materials that improve protection performance and extend shelf life. Such as the development and application of high barrier coextrusion composite film; High resistance plastic packaging materials have been rapidly developed and widely used because they can give quality assurance, freshness preservation, flavor preservation and extend shelf life. In addition to polyvinylidene chloride (PVDC), ethylene and vinyl alcohol copolymer (EVOH), which are widely used at present, in recent years, environmental friendly materials have been developed to promote polyvinyl alcohol (PVA), polyethylene terephthalate (pen), copolyamide (MXD6), silicon or aluminum oxide evaporated film (soft glass) The development of nano inorganic materials will be more noticeable.

The use of metallocene polyolefins (mhdpe, mLLDPE, MPP) can further improve many properties of flexible packaging, such as strength, toughness, transparency, barrier, heat resistance and processability. In 2006, the development trend of improving the technical level and environmental adaptability of flexible plastic packaging film (bag) has become a hot spot in the development of the industry. Composite high barrier, multifunctional packaging and sterile packaging technology have emerged a number of new products with oil resistance, flavor retention, moisture resistance and mold resistance, and the demand for anti-counterfeit packaging and anti-static packaging has also developed rapidly. High barrier and functional soft plastic composite packaging film (bag) is developing to a new technical level.

2. Development and application of sterile packaging materials, antibacterial packaging films and radiation resistant packaging films; The biggest advantage of aseptic packaging materials and technology is that under aseptic conditions, without preservatives and refrigeration, it can retain the original nutritional components and flavor of food to the greatest extent, which can greatly prolong the shelf life and facilitate storage and transportation. The market is developing very rapidly and its use is expanding. In addition to accounting for a large proportion in dairy products and fruit sweat drinks, it will further expand to the field of pharmaceuticals, cosmetics and condiments.

In the process of development, the hygiene and safety of flexible packaging films (bags) are also seriously challenged. Many food plastic packaging materials on the market are difficult to meet the national requirements for food safety, hygiene and environmental protection. In recent years, the sampling qualification rate of packaging bags around the country is low, only 50-60%. From the Lanzhou 'toxic milk powder' incident broadcast by CCTV in July 2005 (due to the excessive residue of toluene and xylene solvents, and the unqualified packaging film (bag)) to the storm caused by the toxicity of the plasticizer Diisooctyl adipate (DIOA) added to PVC fresh-keeping film in October, the reasons for this situation are not only the problems of the enterprise itself, but also the insufficient management and restriction of the industry by the state. The deep-seated problems and factors involved in this matter deserve our deep thinking and attention.

3. Nanocomposite packaging materials will be rapidly industrialized with the rapid development of nanotechnology. Due to the obvious enhancement and improvement of its wear resistance, hardness, strength, impermeability and plasticity, it can be used not only in food packaging, but also in special packaging, such as anti-static, anti electromagnetic, invisible, dangerous goods packaging, etc. it is suitable for heat-resistant packaging materials heated by electromagnetic ovens and microwave ovens, It will make great changes in traditional plastic packaging materials.

4 environmental friendly (environmentally friendly) plastic packaging materials (or green plastic packaging materials) have become a hot spot of global concern with the implementation of the environmental management standard is 14000 series. Among them, plastic packaging materials that are easy to be recycled, such as pet and pen, biodegradable plastics in environmentally degradable plastics (EDP) have become hot spots, and others such as zero pollution foamed plastics, thin-walled bottles and bag packaging containers have also attracted much attention. Controlled atmosphere packaging of packaging materials suitable for the storage of agricultural products such as grain;

However, no matter what kind of plastic packaging is used, it will cause problems caused by the health and safety of VC fresh-keeping film, which can promote more plastics.Packaging enterprises should take the road of green packaging, in addition to developing water-soluble inks that meet health and safety In addition to water-soluble alcohol soluble adhesives, we also need to develop new products of coextrusion technology. The development of coextrusion film application market has become a hot spot in the industry development in the past two years, and progress has been made.

Last year, the State paid more attention to food safety and the safety and quality of packaging in direct contact with food. Green packaging that meets environmental protection requirements and is pollution-free will receive more and more social attention. Vigorously develop green packaging, do a good job in packaging waste treatment and resource recycling, and realize the requirements of sustainable development. Therefore, the relevant departments of the Chinese government and relevant associations, such as the composite film special committee of the China Plastics Processing Industry Association, are working closely to implement the spirit of the document No. 86 (2006) of the General Administration of quality supervision, inspection and quarantine, implement the market access system for products such as plastic packaging containers and tools for food, and issue production licenses to the first 29 enterprises that have obtained market access qualifications on December 27, 2006, A total of 97 products have been applied for admission, covering all 39 product varieties that have been admitted this time. In the future, when purchasing plastic packaging, containers, tools and other products for food, food production enterprises and consumers should recognize the products marked with QS.

Solvent free and water-based environmental friendly adhesives for composite films have been produced abroad and are still being developed in China. The biggest gap in China is that, as Li, vice president of China Plastics Processing Industry Association, said in an interview with foreign visiting experts, China's current output of plastic products ranks first in the world, but the quality is far behind the level of developed countries, mainly due to the backwardness of talents. It is our future development option to strengthen the cultivation and training of talents, take the road of technological innovation and independent intellectual property rights, fully implement the scientific concept of development, and build an innovative plastic packaging enterprise.

Summary and development trend of agricultural film industry

一、Industry Overview

Since 1979, the cultivation technology of agricultural film mulching has been vigorously promoted in China. In 1980, the area covered by agricultural film was only 25000 mu, and in 2005, the area covered by agricultural film reached 170million mu. The land that can be covered with plastic film in China is more than 400million mu, so China's demand for agricultural plastic film will continue to increase, reaching 2.7 million tons in 2010.

Since the production of agricultural plastic films, China has achieved two world firsts, namely, the first in output and the first in coverage, which is roughly 1.6 times the total of other countries in the world. Agricultural plastic films mainly include greenhouse films and mulch films, as well as shading nets, insect proof nets, forage films and agricultural non-woven fabrics. Plastic films are widely used as covering materials for solar greenhouses, plastic greenhouses and various plastic small arch sheds. The annual consumption of greenhouse film has reached 700000 tons, covering an area of 50million mu; The annual consumption of plastic film is about 450000 tons, and the coverage area is more than 220million mu. With the rapid development of agricultural science and technology, the demand for agricultural film will continue to grow. According to incomplete statistics, there are nearly 1000 agricultural film production enterprises in the whole industry, with a production capacity of more than 2million tons, including about 60 enterprises with an annual production capacity of more than 10000 tons and about 30 large backbone enterprises. The well-known agricultural film manufacturing enterprises are mainly concentrated in Henan, Hebei and Shandong, Henan Shuanghui plastic factory, Shandong Rixin Chemical Co., Ltd., Hebei Baoshuo group, Zhongyuan Plastic products factory, Tianjin Ersu, Anhui Guofeng plastic industry, Beijing Huadun, China agricultural chemical import and Export Corporation and Shandong Zibo Tianhe, etc.

The cultivation technology of plastic film mulching has been applied since the late 1950s. This technology can not only promote crop growth and increase crop yield, but also realize the cultivation of fruits and vegetables in cold seasons. According to the function, the greenhouse film can be divided into: long-life film, drip free film, heat preservation film, light conversion film, diffuse film, reflective film, etc. At present, polyethylene (PE) is the main greenhouse film material in China, and some PVC, ethylene / vinyl acetate (EVA) and metallocene polyethylene (MPE) are also used. Polyethylene terephthalate (PET), polycarbonate (PC) and polytetrafluoroethylene (PTFE) are also used to prepare greenhouse films abroad. Although they have excellent performance, they are expensive and use less.

Plastic mulching film can play the role of heat preservation, root protection, antifreeze, moisture conservation, light regulation, water conservation, weeding, and soil salinity control, so as to promote early maturity of crops and improve crop yield and quality. According to the function, the mulching film can be divided into: ordinary colorless transparent film (also known as drip film), drip free film (also known as drip film), light effect film (including colored film and light conversion film), weeding film, heat preservation film, degradable film, aging resistant film, water seepage film (including small hole film and microporous film), etc. At present, polyethylene (PE) is the main film material in China, and some polyvinyl chloride (PVC) is also used. Although compared with PE film, ethylene / vinyl acetate (EVA) film has good heat preservation and transparency, good compatibility with drip free agents, good tensile property, easy film formation, aging resistance and impact resistance, it is less used due to its high price. If the cost is reduced, the consumption is expected to gradually increase.

1. Long life anti-aging film

Most of the anti-aging greenhouse films produced in China are relatively thin (with a thickness of 0.06mm ~ 0.10mm), and their service life is generally up to

By 1.5 ~ 2 years, there is still a big gap in the service life compared with the thicker greenhouse film abroad (with a thickness of 0.18mm ~ 0.20mm). For example, the PVC long-life film in Japan can be used for 2 ~ 3 years, and the PET film can be used for 10 years. By optimizing the general resin materials and stabilizers, the service life of the greenhouse film can be extended. Specifically, in terms of optimizing basic resin materials, agricultural film manufacturers often use resins with high molecular weight, narrow molecular weight distribution and few branch chain numbers to produce aging resistant PE greenhouse films based on melt flow rate (MFR). In addition, the residual amount of transition metal ions, crystal morphology and crystallinity of the basic resin are also important indicators to optimize the functional greenhouse film. For example, Beijing Yanshan Petrochemical Company, Qilu Petrochemical Company, Tianjin United Chemical Company, etc. have developed special resins for the production of functional PE greenhouse film; In terms of adding compound non-toxic light stabilizer and developing high-efficiency anti-aging system, gw540/2002 anti-aging system, which has been applied in China for more than ten years, needs to be gradually replaced by non-toxic anti-aging system due to its serious irritation and sensitization. At present, foreign non-toxic polymeric hindered amine light stabilizers have successively entered the Chinese market, including Ciba Specialty Chemicals of Switzerland, cyanate of the United States, Clariant of Switzerland, 3vsigma of Italy, etc. However, the price of polymeric hindered amine light stabilizers introduced abroad is high, which is difficult for most manufacturers in China to bear. Bw6911 new light stabilizer and 6911/b215 anti-aging system launched by Beijing Institute of chemical industry not only have excellent performance, but also are cheap. The polyolefin greenhouse film produced by this system has achieved satisfactory results after application in Northeast, North China and southwest China, which has better overcome the 'backplane effect' and extended the service life of the greenhouse film, which is worthy of further promotion and application.

The requirements for aging resistance of mulching film are not as high as that of greenhouse film. Among plastic mulching films, PVC is the earliest used mulching film resin, which has the characteristics of high strength, UV resistance, aging resistance, transparency and good heat preservation. However, because of its high density, film thickness, complex formula and process, and high cost, it has been gradually replaced by PE film. At present, except for the three provinces in Northeast China and some regions in Shandong Province, almost all other regions use PE film. In PE film, HDPE, LDPE and LLDPE are used. Among them, HDPE has high strength, but it is not resistant to aging; LDPE has low strength but good light transmittance; LLDPE has good strength and aging resistance, so LLDPE is the most suitable film material. Considering the cost, aging resistant PE film materials in China are mostly blended with LDPE with 70% LLDPE.

2. Antifogging film

There is high temperature in the film, which is suitable for spring and autumn. It has a good effect on thermophilic crops. The disadvantage is that fog droplets are easy to form in the film, which affects light transmission. The surface of drip free film (also known as drip film) contains hydrophilic substances. The water droplets in the film flow down the film, with low humidity, good light transmittance, large temperature difference inside and outside the film, and its performance is generally better than that of drip film. In order to improve the dripping performance of the film, it is generally possible to modify the surface polarity of the film or add dripping agent. In application, dripping agent and antifogging agent are often added or coated on the surface of the film at the same time, even if they have both antifogging and dripping functions, so as to further improve the light transmittance of the film. The dripping agent is a mixture of various non-ionic surfactants, and the mist eliminator is a special surfactant, such as fluorine-containing surfactant and / or silicon-containing surfactant. It is found that the 'coordination effect' of dripping agent and defogger is very important. Both Beijing Research Institute of chemical industry and Lin'an plastic chemical additives factory have developed a trickle demisting system with good demisting effect. The purpose of coating type drop demister was to supplement the effect so that the performance and life of the film could be synchronized as much as possible. At present, the development of coating type drop demister system has become one of the important ways to produce functional greenhouse film.

3. Light effect film

For greenhouse film, in order to obtain sunlight to promote crop growth, light conversion agents are often added to the film, while less light conversion agents are used in plastic film, and more colored film is used. In the development and application of light conversion agents, only by turning green light, can we really play the role of light conversion. At present, the light conversion agents that have been applied in the production of light conversion greenhouse films mainly include rare earth light conversion agents or light conversion agents composed of organic fluorescent pigments. The 'single base dual energy rare earth light conversion agent' developed by the luminescent materials research office of Hunan Normal University has the function of converting ultraviolet light into blue light and red light, and converting green light into red light, which has a good application effect. The light conversion greenhouse film produced by some enterprises is also called high light energy film, light ecological film, high light quality film, etc. The high light energy greenhouse film developed by Beijing Huadun Plastic Co., Ltd. has the characteristics of wide excitation spectrum and emission spectrum. The emission spectrum of blue light region (420nm ~ 460nm) and red light region (620nm ~ 660nm) has high relative luminous intensity. Because blue violet light is conducive to crop growth, and red light can promote fruit formation, it can make crops mature in advance, increase early yield, and have a better effect of increasing production and income.

There are many varieties of colored films in mulching film, which are suitable for different crops. For example, purple film can pass through red and blue light and absorb green light, which can improve spinach production and prolong the marketing period; The red film can promote the growth of cucumber through red and blue light; Silver gray film and aluminum foil reflective film have strong light reflection effect, which can drive aphids, keep the ground temperature, fill the light on the back of crops with insufficient light, promote fruit coloring, and improve fruit yield and sugar content. The colored film material is generally PE, with a small amount of PVC, and the pigment is added in the form of color masterbatch. All kinds of colored mulching films are mostly single-layer films, except for aluminum foil reflective films and black-and-white double-sided mulching films, which are composite films. Both light conversion greenhouse film and colored mulching film are developing towards high efficiency and specialization.

4. Multifunctional composite membrane

With the improvement of production technology, agricultural film is developing towards a multifunctional film that can simultaneously meet the requirements of long life, heat preservation, mist elimination and good light transmittance. Advanced three-layer coextrusion composite film blowing technology has been successfully applied in many enterprises. Some enterprises use internal cooling devices to improve the stability of wide blown film bubbles and the transparency of greenhouse film, and improve the dripping property of greenhouse film; Some enterprises have adopted domestic three-layer composite wide film blowing unit, which can produce functional greenhouse film with a width of 12m ~ 20m; Some enterprises have improved the inserting and stacking mechanism of blown film bubbles and the traction coiling technology, effectively solving the creep problem of the folding part of the greenhouse film and improving the flatness of the greenhouse film; Some enterprises have improved the master batch manufacturing process, resin and master batch mixing process and extrusion process technology, so that the functional additives are more evenly and stably dispersed in the greenhouse film, thereby improving the quality of the functional greenhouse film. For example, EVA multi-functional three-layer composite greenhouse film (with a thickness of 0.10mm) added with drip demisting system and inorganic heat preservation agent has a good effect on covering the suburbs of Shenyang, Liaozhong County and Anshan area in Liaoning Province.

5. Degradable agricultural film

In order to solve the problem of white pollution of agricultural film, in addition to strengthening the recycling of anti-aging agricultural film, it is more important to strengthen the development and application of degradable plastic film, which is also a development trend of agricultural film. The traditional degradable mulching film is mainly prepared by blending method, that is, adding biodegradable substances into polyethylene resin, or adding photodegradants and other components, so that it can be locally broken first in use, and then a large film into the soil into small pieces that are not noticed. However, this only turns the visible pollution into invisible pollution, but does not fundamentally solve the problem of soil pollution. At present, the hot spot in the development of degradable mulching film is to use degradable polymer materials with other structures to replace polyolefins with photodegradants, or blend new degradable materials with polyolefins and degradants, combine biodegradation and photodegradation, improve degradation efficiency and controllability, and fundamentally solve the problem of incomplete degradation.

二、Development trend of agricultural film

Through asset restructuring, strong combination and listing, China's agricultural film enterprises will give full play to their comprehensive advantages and launch an impact on the high-end market of agricultural film, which will become the main development trend in the future. It mainly improves the overall quality of enterprises, and also solves the problems of market planning, technological innovation, team cooperation, etc., and pays attention to the implementation of new ideas, new ideas and new methods, so as to narrow the gap with foreign-funded enterprises.

The competition in the agricultural film market is becoming increasingly fierce, and the market demand is constantly updating and changing, but the development potential of the market is huge, and the overall application level of agricultural film needs to be further improved. The structure of greenhouse film products is developing towards multiple layers, and the performance is developing towards functionalization and comprehensive performance, such as high light transmittance, high insulation, high strength, long life, continuous dripping period, fog proof period, light conversion period, dust-proof period, bacteria proof period, etc; Mulching film products are developing towards the functionalization of soil moisture conservation, warming, weeding, pest control, etc., and the specialization of asparagus, cotton, tobacco, garlic, leek and other varieties.

In short, the agricultural film industry will continue to develop towards enterprise scale and product functionalization. At the same time, improving the recyclability and degradation technology of agricultural film and reducing environmental pollution not only promote the sustainable development of agriculture, but also ensure the future development of agricultural film industry. At the same time, in line with the national industrial policy, the development of pollution-free agricultural film will be very important. In agricultural plastics, it is necessary to improve the functionality of greenhouse film, achieve long-life aging resistance, anti fog and anti dripping, high transparency and high heat preservation, realize light energy conversion, and improve the light cooperation of crops; For mulching film, we should solve the problem of white pollution remaining in the soil, and develop a variety of functional mulching films, such as aphid removal, weeding and coloring.

Developed countries have developed light ecological greenhouse films, which can keep the ultraviolet light beneficial to crop growth, filter out or convert the ultraviolet light or green and yellow light harmful to crops into blue violet light and red orange light required for crop photosynthesis. The UV light conversion range is wide, the light conversion spectrum is consistent with photosynthesis, and the light conversion life can be as long as 180-300 days, which has the function of significantly improving crop quality and reducing pests and diseases; However, the development of light ecological greenhouse film in China is still blank. Although the development of light conversion greenhouse film is successful, most of it is mainly warming, the light conversion range is narrow, the effect is poor, the light conversion life is only 20-30 days, and the UV light conversion is only 1%-3%. The red orange light peak is not in good agreement with photosynthesis, and the effect of increasing production is limited. It basically does not improve crop quality and reduce pests.

At present, developed countries mainly use special greenhouse films, and different sheds can be used according to the different needs of different crops for light

Film, so the cultivated crops have high yield and good quality; At present, China is still a multi-purpose film, so the phenomenon of 'persimmon is not red, eggplant is not purple' is quite common. In the process of developing industrialized agriculture, developed countries have developed plastic greenhouses. The covering material is no longer traditional plastic film, but thick film or thicker sheet, with high strength, good light transmission and strong heat preservation performance. It can be used for 15-30 years at a time, and can also be easily integrated into a variety of functions, such as light conversion, drip prevention, fog prevention, etc; In China, traditional plastic films are still generally used, with short service life and poor functionality.

The layout of China's agricultural industry will develop towards regionalization and specialization, the industrial center will continue to develop towards advantageous production areas, the facility structure will become larger, the environmental regulation will become more intelligent, and the diversification of cultivation and horticulture will become a new growth point of the horticultural industry. Moreover, at present, the national high-grade agricultural film only accounts for 2% of the total output of agricultural film, the medium-grade agricultural film accounts for 20%, and the low-grade products account for 78%. The supply of low-grade agricultural film products exceeds the demand, which is far from the level of developed countries, where the medium and high-grade products account for 20%, the medium-grade agricultural film accounts for 50%, and the low-grade products account for only 30%. The data shows that the development space of agricultural film industry in China is quite broad: first, more than half of the planting area suitable for agricultural film coverage in China is still blank; Second, the proportion of functional membrane only accounts for 30%, while it reaches 80% abroad; Third, the high and middle grade agricultural film production can not meet the market needs.

However, as agricultural film is an agricultural product, for many years, the designated enterprises of agricultural film have made great sacrifices to benefit farmers for a long time, and have been in a state of low profits, breakeven and even loss, resulting in a serious lack of momentum for development. After joining the WTO, all domestic enterprises are facing fierce competition in both domestic and foreign markets. Product upgrading, equipment upgrading and technological progress all need policy and financial support. If we can get the funds and policy support from relevant national departments, the development of agricultural film industry will be faster.

In order to meet the requirements of the situation, enterprises in the industry should pay attention to: first, the more promising the situation is, the more it is necessary to avoid blindly starting, overcome the disadvantages of low-level repeated construction in the past, change the situation of large number, small scale and low level of agricultural film enterprises, and concentrate on making the existing backbone enterprises bigger and stronger; Second, seriously implement the scientific concept of development, save resources, reduce energy consumption, pay attention to recycling, protect the environment, and take the road of green, sustainable and healthy development; Third, strengthen internal management, constantly improve the core competitiveness of enterprises, and implement brand strategy.

With the development of China's national economy and the improvement of people's living standards, fog prevention has put forward higher requirements for the quality of agricultural products such as vegetables. Therefore, the development of a new generation of functional greenhouse film - - photo ecological film, which meets the current market needs, can not only increase production, but also significantly improve crop quality and reduce crop diseases and pests, has become an urgent task for China's agricultural film industry.

Functional film

1. Impermeable composite film

This is a kind of functional film widely used in the field of food packaging and medical packaging in China. The impermeable composite film refers to a composite film with high impermeability to oxygen, moisture, aromatics and volatile substances. It is generally composed of three parts: gas barrier layer (impermeable resin), water barrier layer (polyolefin resin) and adhesive layer (adhesive resin). Multi-layer coextrusion is the main method to produce impermeable composite film, According to the shape and structure of the die, multi-layer coextrusion can be divided into multi-layer coextrusion tube film composite process and multi-layer coextrusion tape casting composite process. Barrier composite films can be divided into symmetric and asymmetric types according to their structural characteristics. At present, the market is mainly asymmetric, and there are 3, 5, 7, 9 and 11 composite films according to the number of composite layers. Commonly used impermeable resins include PA, EVOH, pet, PVDC, pan, etc; Polyolefin resins include PE, PP, EVA, MPE, etc; Adhesive resin is a kind of resin that has stable adhesion to barrier resin and polyolefin resin, such as maleic anhydride grafted PP.

In recent years, silicon oxide film with high resistance and permeability is also very attractive in the market. It is coated with a layer of silicon oxide on pet and nylon film, which has the advantages of high resistance and permeability, oil resistance, drug resistance, transparency, flexibility resistance, environmental adaptability, microwave oven adaptability and so on. The technical trend of its development is not only to improve its printability and impermeability, but also to make it have the functions of blocking ultraviolet rays and preventing electrification.

2. Antibacterial film

Antibacterial film is to add silver ions, fluorspar, juniper alcohol and other antibacterial substances into the film to make a bactericidal fresh-keeping film. At present, this product has been successfully applied in the packaging of tofu, fish, meat and pickles abroad, but it is still basically in the experimental stage in China. For example, hailke chemical company has added nano inorganic antibacterial materials to the film to produce an antibacterial film with better comprehensive performance.

3. Electromagnetic shielding film

Electromagnetic shielding film can block the electromagnetic wave of microwave oven, avoid the leakage of electromagnetic wave, facilitate the safe use of microwave oven, and can be widely used in the field of food packaging and decoration. The film is a kind of aluminized composite film. Its process is to coat a layer of 400 ~ 500 on the surface of polyester film by vacuum evaporation μ M thick aluminum film.

4. Microporous film

Special microporous film is a highlight of the current fruit and vegetable fresh-keeping film, that is, according to the fresh-keeping ball of the packaged fruits and vegetables, different numbers of small holes are opened on the plastic film to improve the gas transmission rate. Data show that the oxygen transmittance of the film is 800 ~ 200ml / m2? 24 ｈ? MPa, the freshness of fruits and vegetables is the best. In addition, microporous film is also used in mulching film for ventilation and water seepage, which can reduce the number of crop irrigation and save water.

5. Water soluble film

As a novel green packaging material, water-soluble plastic film is widely used in the packaging of various products in Europe, America, Japan and other countries, such as pesticides, fertilizers, pigments, dyes, detergents, water treatment agents, mineral additives, detergents, concrete additives, photographic chemicals and gardening care chemicals. Its characteristics are: complete degradation, non-toxic and safe, high heat sealing strength, anti-counterfeiting function, good printing performance, anti-static and dust-proof, etc. Its main raw material is polyvinyl alcohol (PVA) with low alcoholysis degree, and various additives are added, such as surfactants, plasticizers, anti adhesion agents, etc. At present, the water-soluble film market is rising in China. The Institute of Applied Technology of light industrial plastics of Beijing University of technology and technology has realized the dry melting granulation and film blowing processing of PVA by screening out plasticizing modifiers that can reduce the plasticizing temperature of PVA, and has applied for five patents. Now some patents have been transferred and put into production; Zhuzhou Institute of technology and Guangdong Zhaoqing Fangxing packaging materials company have jointly developed water-soluble films and production equipment, and their products are going to the market. Compared with foreign countries, the price of domestic water-soluble film products has strong competitiveness. The price of water-soluble PVA film in the United States is 130000 ~ 170000 yuan / ton, that in Japan is 200000 ~ 250000 yuan / ton, while the price of domestic products is only 60000 yuan / ton.

In addition, functional films include transparent wear-resistant film, rainbow film, special medical packaging film, selective transmission film, geomembrane, etc., which have been widely used in all aspects of production and life.