Production technology and application of the hotte

Production technology and application of barrier plastic packaging film (Part I)

over the past 20 years of reform and opening up, China's plastic packaging industry has developed steadily and rapidly, and has developed from a decentralized industry in the initial stage to an independent industry with complete product categories, although the previous report proposed 8 ~ 10 or even 12 cavity modern industrial systems. It is predicted that by 2005, the annual market demand in the field of plastic packaging materials in China will reach 5.5 million tons, with an average annual demand growth rate of 10%. It is the fastest growing industry in the plastic products industry and is a sunrise industry with broad development prospects. Among them, film is the most used plastic packaging material. Due to its non-toxic, light weight, beautiful packaging and low cost, its application field is constantly expanding, and it has almost penetrated into all aspects of industrial and agricultural products and daily necessities. The investment in the plastic packaging film industry is growing rapidly. Therefore, grasping the overall trend of international and domestic plastic packaging film technology and market development is of great practical significance for making forward-looking and correct decisions

1functionalized development trend of plastic film

with the development of society and the improvement of people's living standards, the classification of products is becoming more and more detailed. The packaging of products is not limited to visual effects, but should be developed in depth in the direction of functionalization and diversification according to the characteristics of products and market demand. In recent years, technological progress has made the functionalization development trend of plastic packaging film increasingly obvious. Plastic packaging film with high requirements and high-tech content is becoming the pillar industry and R & D goal of many enterprises. Its packaging functions are diverse. In addition to the requirements for antistatic, anti adhesion and smoothness of general films, it is mainly through the adjustment of raw materials, additives or processes to give packaging film some special functions, For example, the heat shrinkability required for the straightness and tightness of cigarette and beverage packaging, the air permeability required for the packaging of vegetables and fruits, the conductivity required for the packaging of electronic components, the high optical performance required for the perspective packaging, the rust resistance required for the packaging of metal equipment and instruments, and the barrier and antibacterial properties increasingly needed in food, cosmetics and medicine, The functionalization of the film improves the added value of the product [1]. Barrier plastic packaging film is one of the fastest growing functional films at present. According to a research report on the development trend of eight high profit packaging markets in Europe in the next five years recently released by the famous British Pira International Group, the report provides first-hand information about the development trend of the high profit packaging market of 300 relevant packaging multinational enterprises in Europe, and accurately quantifies the growth of the high profit market in the next two and five years. The research shows that high barrier materials rank fourth in high value-added products. In China, barrier packaging film is in the growth period of promotion and use. Most domestic barrier films are used in the packaging of low-end products. Barrier films with excellent performance still need to be imported in large quantities, so there is a lot of room for market development

2 barrier property

the barrier property of resin refers to the shielding ability to small molecular gases such as oxygen, water vapor, liquid and odor. The barrier film is mainly used in food and pharmaceutical packaging to ensure that the packaging material will not deteriorate during storage and transportation, so as to extend its shelf life and shelf life. With the acceleration of the pace of life and the improvement of living standards, the demand for various convenience foods, such as meat products, dairy products, halogenated products, is increasing, and the quality requirements for pharmaceutical products are also increasing. In addition, barrier plastic films are also widely used in the packaging of cosmetics, tea, chemical reagents, pesticides, spices, feed and other products. Therefore, barrier films have become a hot spot of competitive development in various countries [2]. The use of barrier resins in barrier plastic films is the key [1 ~ 3], mainly including polyvinyl alcohol (PVA), ethylene vinyl alcohol copolymer (EVOH), vinylidene chloride copolymer (PVDC), polyethylene naphthalate (pen), special nylon (mxd2), nylon (PA), polyethylene terephthalate (PET), etc. among these barrier resins, PVA, EVOH, PVDC Pen is a high barrier material, the most commonly used are PVDC and EVOH, while PA is similar to pet in barrier property, belonging to medium barrier material. Research shows, PVA has the best oxygen resistance, beyl said: "the automotive industry particularly benefits from this oxygen resistance, but because it contains a large amount of hydroxyl, it has high moisture permeability and is sensitive to water; EVOH obtained by copolymerizing vinyl alcohol with ethylene (generally 25% - 45% ethylene content) The hydroxyl group in the material is reduced, so its moisture resistance performance is not changed as much as possible. The injection temperature, back pressure, injection cycle and the amount of color masterbatch are greatly improved. Although the oxygen permeability is improved, it is still a high barrier material better than PVDC. The disadvantage of PVA and EVOH is that the hydroxyl group in the material is easy to combine with the water in the environment to form hydrogen bonds, and its moisture resistance performance is greatly affected by humidity, so it can only be used in the core layer; PA has a certain barrier property, but the high moisture absorption affects the barrier property, so it can not be used as an outer layer generally; The modified special nylon mxd2 has better heat resistance, low moisture absorption, and the barrier property decreases little with the increase of temperature and humidity. Therefore, although it was developed late, its development and application are rapid

pvdc was the first to open the company, Chairman Wu Kunyuan told: "ldquo; Other peer enterprises generally can only press a single circuit board product to 8 layers of high barrier materials, which have a long history of use. They have been widely used in food packaging since the 1980s. PVDC is mainly used as casing film in China. PVDC has excellent oxygen and humidity resistance, but it is opposed by environmental protection people because of its chlorine content, and it is a prohibited material in some countries in Europe. Pen is a kind of high barrier material with excellent comprehensive performance, but its price is expensive and its popularization and application are limited. In the development of new materials, professional production enterprises in the United States, Japan and other countries have done a lot of work. Through modification technology, various new brands of resins with new functional characteristics have been introduced, such as blow molding grade PVA and PVDC, stretchable EVOH, barrier metallocene polypropylene, etc. Therefore, domestic enterprises have a wider range of choices in the use of raw materials

(to be continued)