Plastic Packaging New Materials

From the perspective of the development of the entire packaging industry in the world, although plastic packaging materials have been subject to serious environmental challenges, plastic packaging remains one of the fastest-growing materials in the packaging industry. In order to meet the requirements of the new era, in addition to the requirements for increasing the packaging quality and efficiency of the market, plastic packaging materials are further required to save energy, save resources, and be easily recycled or easily degraded by the environment for technological development. Point of departure. For this reason, plastic packaging materials are being developed toward high performance, versatility, environmental adaptability, new materials, new processes, new equipment, and widening application fields.

High-performance, multi-functional plastic packaging materials are becoming a hot spot in many countries, and some products have been put into industrial production. Such materials include high permeability, multi-functional preservation, selective permeability, heat resistance, sterility (anti-bacterial), rust prevention, deodorization, resealability, and easy-openability. Impermeability, multifunctional preservation, aseptic packaging materials, etc. are developing more rapidly. In addition, nanocomposite packaging materials being researched and developed in recent years are receiving attention.

Polyethylene naphthalate (PEN)

PEN resin structure and PET are very similar, but PEN in all aspects of performance is better than PET, it has the following characteristics: 1. PEN's heat distortion temperature is 30 °C higher than PET, reaching 100 °C, and can be used for hot filling. 2. The glass transition temperature of PEN is about 40°C higher than that of PET. At the same time, the tensile strength, flexural modulus and bending strength of PEN are also high. Therefore, PEN has good dimensional stability, low thermal shrinkage, and good long-term heat resistance. 3. PEN is superior to PET in its resistance to acids, alkalis, hydrolysis and general chemicals. 4. PEN is a kind of good gas barrier property in all kinds of plastics. The barrier property to oxygen, carbon dioxide and water is 4 times, 5 times, 3.5 times higher than that of PET respectively. 5. Compared with PET, PEN is less adsorbable to organic solvents and has a lower free-standing and precipitated property. 6. PEN crystallinity is lower than PET, easy to make thick-wall transparent bottles. 7. Has good UV resistance. 8. PEN has good hygienic properties.

PEN has excellent properties and is an ideal packaging material. However, PEN is expensive, which limits its wide use as a packaging material. Since both PEN and PET are thermoplastic polyesters and their chemical structures are similar, a certain ratio of PEN and PET are melt-blended to form a polymer. Alloys, which can take into account the economics of PET, heat resistance and gas barrier properties of PEN, are currently the focus of PEN application research and development, and are also one of the main ways to bring PEN to market (especially packaging). When 10%-20% of PEN is blended with PET, the barrier properties to oxygen and carbon dioxide can be increased by 30%-50% and 23%-37%, respectively, and the shielding wavelength of ultraviolet rays can be increased to 380 nm. PEN/PET blends or copolymers have been used for the packaging of edible oils, alcoholic beverages, carbonated soft drinks, and beer.

At present bottle containers have become PEN's main market. Due to the excellent characteristics of PEN, PEN bottles blown with PEN perform better than PET bottles. PEN bottle transparent, hot filling temperature up to about 100 °C, good barrier to ultraviolet, oxygen, carbon dioxide, and chemical resistance, used in beverages, beer, cosmetics, baby food packaging, has great practicality and market . Especially in beer packaging, it has made up for the defects in PET and glass and has become a hot topic in recent years.

Teijin is a pioneer in the production of biaxially oriented PEN films in the world. As early as 1989, it successfully developed highly functional PEN films. In 1993, it built a 4,000-ton/year film production line. In addition, world film giants such as Toray and DuPont have also entered the PEN film production market. PEN can be manufactured using the same equipment as PET. The process is the same as PET film production. PEN film (BOPEN) is produced by melt extrusion-biaxial stretching. BOPEN has excellent characteristics such as heat resistance, gas barrier property, hydrolysis resistance, dimensional stability, etc., and it is easy to obtain an extremely thin film with a thickness of 0.8 μm. By using these characteristics of the film, packaging materials for different purposes can be obtained. Among them, there is a large market for food packaging, pharmaceutical packaging, fragrant packaging, and impulse packaging for precision instruments.

Polyvinylidene chloride (PVDC)

PVDC is a light yellow, powdery, high barrier material. In addition to the general properties of plastics, it also has self-extinguishing properties, oil resistance, good taste and excellent moisture, mold and other properties, but also has excellent printing and heat sealing properties.

PVDC is a kind of packaging material with better comprehensive barrier performance in plastic packaging in the world today. It is different from the fact that polyvinyl alcohol has a sharp decrease of gas barrier property with increasing moisture absorption, and is different from the fact that the nylon membrane deteriorates the moisture-blocking property due to water absorption, but it is a kind of high barrier property with good moisture resistance and gas barrier properties. material. It not only has excellent high barrier properties, but also has excellent printing performance, composite properties and transparent properties. In practical applications, PVDC coating film has no special requirements for printing inks and equipment. Therefore, it is not necessary to change the processes of each process, and the production efficiency and cost can be greatly improved.

The use of PVDC composite packaging than conventional PE film, paper, aluminum foil and other packaging materials to reduce a lot, so as to achieve the purpose of reducing packaging and reduce waste. In the United States, PVDC products are non-toxic and safe plastic materials, which have been widely used in food packaging; in Germany, the packaging materials have green signs; while in Japan, South Korea, small packaging foods, medicines, chemical products, and electronic products that circulate on the market About 60% use PVDC packaging. With the popularity of this new packaging material, in recent years, the output of PVDC resin in Western countries has increased year by year. The annual growth rate of the United States is about 2%, and Japan is nearly 10%.

In view of the fact that the level of food packaging in our country is still relatively backward, relevant experts pointed out that the promotion of the use of PVDC materials not only can improve the packaging product quality in China, but also can reduce the losses caused by product packaging, thereby enhancing market competitiveness and establishing a new corporate image. . It can be predicted that in the future packaging industry, the full and reasonable use of PVDC coating film will gradually become the mainstream of the packaging industry in China, and food consumption will be greatly reduced.

Water-soluble plastic (PVA)

Polyvinyl alcohol (abbreviated as PVA) has a white powder appearance and is a widely used water-soluble polymer with properties ranging from plastic to rubber. As a novel green packaging material, it 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 , chemical reagents for photography, and chemical reagents for gardening. Its main features are: 1. Degradation is complete, the final products of degradation are CO2 and H2O, which can completely solve the problem of packaging waste disposal; 2. Safe and convenient to use, to avoid direct contact with the packaged material, can be used for the packaging of harmful substances on the human body; 3. Good mechanical properties, heat sealable, high heat seal strength; 4. With anti-counterfeiting features, it can be used as the best weapon for anti-counterfeiting of high-quality products, extending the life cycle of quality products.

As far as the degradation mechanism is concerned, polyvinyl alcohol has both water and biological degradation characteristics. First it dissolves in water to form a glue liquid that penetrates into human soil, which increases soil stickiness, air permeability and water retention, and is particularly suitable for sand soil transformation. The PVA in the soil can be decomposed by a strain of bacteria, Pseudomonas, isolated in the soil. A symbiotic system composed of at least two bacteria can degrade polyvinyl alcohol: one is an active bacterium of polyvinyl alcohol, and the other is a bacterium that produces substances required for PVA-active bacteria. The oxidation of secondary alcohol catalyzes PVA, and then the hydrolase cleaves the oxidized PVA backbone, further degrades, and eventually degrades to CO2 and H2O.

Since water-soluble films have environmental characteristics, they have received extensive attention from developed countries in the world. For example, Japan, the United States, and France have mass-produced and marketed such products, such as the United States’ W. T. P company and C. C. I. P company, France's GREENSOL company and Japan's synthetic chemical company, its users are also some famous big companies, such as Bayet, Henkel, Shell, A-gr.Eva Other large companies have started using water-soluble films to package their products.

In China, the water-soluble film market is emerging. According to relevant statistics, China's annual need for packaging film accounts for 20% of plastic products, which amounts to approximately 309,000 tons. Even if it accounts for 5% of the market, the annual demand will reach 15,000 tons. The current market price: US products for 13-17 million / ton, Japan's products for 20-25 million / ton, the domestic product sales price is only 40% of the United States, the average selling price of 60,000 yuan / ton, so in The price is very competitive. With the development and progress of society, people are paying more and more attention to protecting the environment in which we live. In particular, after China's accession to the WTO, it is in line with the developed countries in the world, and the environmental protection requirements for packaging have been increasing. As a result, water-soluble packaging films are in China. The application prospect must be very broad.

Polypyrazine amide (PZA)

Similar to polystyrene, PZA polymer is a highly transparent, well-operated, and water resistant material that is resistant to most thermoforming processes; it can use conventional processing equipment, including sheet and film extrusion equipment. , Blown film manufacturing, fiber spinning and injection molding processing equipment. It has a good price and performance potential compared with PET, it also provides excellent adhesion properties and gloss characteristics, and has a good metallized properties.

Current commercial applications of this PZA polymer include: compostable food bags and "garden waste" bags, yoghurt packaging cartons, sowing mats, and non-woven coverings to prevent weed growth. This polymer is currently being produced at the PZAZT plant in the United States and will reach 7,200 tons of production capacity by the end of this year. Although this PZA resin has emerged in the market, it is still limited to the demand for biodegradation.

With the increase in the quality of plastic packaging products and the increase in functionality, new varieties of plastics for packaging have been continuously developed, and the use of existing plastic varieties has been further expanded. In particular, high-barrier plastic packaging materials are mainly made up of food packaging and gradually expanded to the non-food packaging field. Industrial packaging, pharmaceutical packaging, agricultural and sideline product packaging, building material packaging, and marine product packaging will all be further developed.