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The Wave of Green Development Has Further Advanced in the Flexible Packaging Industry

The wave of green development has been further advanced in the flexible packaging industry, with sustainable development gradually transforming from a concept into concrete actions taken by industry-leading enterprises. Against this backdrop, new materials, new processes, and new equipment—such as benzene-free inks, solventless lamination, high-efficiency drying devices, organic solvent recovery, and waste recycling—have been applied in the flexible packaging industry. Many flexible packaging companies made early preparations in 2009 and actively pursued technological upgrades, which resulted in a small development peak for almost all flexible packaging equipment suppliers that year.

New Technological Developments in the Flexible Packaging Industry

Like other forms of packaging, flexible packaging must take into account the three essential elements of packaging: safety, convenience, and aesthetics (display and promotion). After more than twenty years of development, China's flexible packaging industry has made tremendous progress, particularly in terms of aesthetics, where it has reached a world-leading level. However, in terms of safety, there are still certain problems in China's flexible packaging industry that require continuous effort to address. Judging from the current market situation, as individual order volumes become smaller and printing plate changes become more frequent, and with rising crude oil prices, persistently high prices of various raw and auxiliary materials, and increasing labor costs year by year, the profit margins of the flexible packaging industry have been further compressed, and cost pressures are growing daily. Therefore, new technologies, new processes, new equipment, and new materials in China's flexible packaging industry will develop rapidly in the direction of environmental protection and safety, energy conservation and emission reduction, cost reduction, waste reduction, and improved efficiency and yield.

1. Benzene-Free Inks and Universal Inks

To meet the strict requirements for residual solvent content set forth in the new series of national standards, the use of environmentally friendly benzene-free inks is an urgent priority for flexible packaging enterprises. For most flexible packaging companies, if they continue to use benzene-containing chlorinated polypropylene inks, it is difficult to meet the relevant requirements through process control alone. The use of benzene-free inks can not only effectively eliminate the residual of benzene-based solvents but also significantly reduce ethyl acetate residues, which is conducive to the overall control of total solvent residuals. Therefore, major ink suppliers have successively launched benzene-free and ketone-free inks. These inks do not contain aromatic hydrocarbons or ketone solvents and feature low odor and high gloss, helping to enhance the competitiveness of gravure printing in the packaging and printing field. In addition, benzene-free inks using chlorinated polypropylene modified resins as binders have also been widely applied due to their lower cost, ease of use, and adaptability to the special requirements of extrusion lamination. As for alcohol-water system composite inks, due to some problems that are currently difficult to resolve, their application has progressed slowly for color inks, although white inks have gained relatively broad application.

2. Solventless Lamination Technology

With the introduction of relevant laws, regulations, and standards, the market has imposed stricter requirements on the hygiene and safety performance as well as the barrier and protective performance of packaging materials. The flexible packaging market will undergo major structural adjustments, which presents development opportunities for solventless lamination.

The solventless lamination process does not use solvents, does not involve exhaust emissions, and does not require large and complex heating blower or exhaust systems. The equipment is simple, occupies a small footprint, consumes less energy, and has a straightforward process flow. It offers advantages such as low cost, resource conservation, and environmental friendliness, making it the main direction for future lamination process development. At present, most low-to-medium-grade flexible packaging materials can be produced using solventless lamination, but due to factors such as lamination quality, solventless lamination cannot yet fully replace the dry lamination process.

In 2009, breakthroughs were made in the development and application of domestically produced solventless lamination equipment and adhesives, which are gradually maturing. Although solventless lamination is currently less widely applied in China, in the long run, with increasingly stringent environmental regulations and continuous economic development, solventless lamination is bound to usher in a period of significant growth.

3. New Technologies in Printing Machinery Equipment

In recent years, gravure printing presses have entered the electronic shaft era, and the cost of electronic shaft gravure presses is declining significantly. Interchangeable printing carriages, sleeve-type impression rollers, and high-efficiency drying systems have been gradually applied, helping flexible packaging enterprises achieve remarkable results in energy conservation, consumption reduction, emission reduction, and safety. In addition, technologies such as secondary registration printing, electrostatic ink absorption devices, high-efficiency static elimination devices, remote diagnostic systems, and online quality inspection systems have also begun to be applied.

4. Organic Solvent Recovery Technology

Large quantities of organic solvents are used in the printing and lamination processes of flexible packaging, which is an important cause of solvent pollution in the flexible packaging industry. The exhaust systems of gravure presses and laminators emit large amounts of exhaust gas containing organic solvents, not only polluting the atmospheric environment but also causing indoor pollution and safety issues due to the volatilization of organic solvents during use. For many years, the flexible packaging industry has adopted high-altitude exhaust as a means of discharging organic solvent gases, but this approach can no longer pass environmental impact assessments. In the coming years, the state may introduce mandatory measures requiring flexible packaging enterprises to install organic solvent recovery and treatment devices to reduce exhaust emissions and ensure that national energy conservation and emission reduction targets are met.

Under the dual pressure of environmental policies and cost constraints, in 2009, organic solvent recovery technology in China's flexible packaging industry developed and spread rapidly. Some large flexible packaging enterprises have already begun to recover and treat the organic exhaust gases (solvents) generated during production, primarily using two methods:

(1) Adsorption Recovery Method: The organic exhaust gases generated during flexible packaging production are processed through adsorption, reduction, purification, and recovery for reuse. This approach not only solves the environmental pollution problem but also turns waste into treasure, recovering and recycling organic solvents and saving substantial funds for solvent procurement. However, because recovered solvents contain impurities that could affect consumer health if used directly, flexible packaging enterprises adopting this technology must ensure the purity of the organic solvents. In Europe, flexible packaging enterprises are required to be equipped with organic solvent recovery equipment before they are permitted to operate, and recovered organic solvents must be re-distilled before use.

(2) Regenerative Thermal Catalytic Combustion Method: The exhaust gases generated during the production process of flexible packaging enterprises are relatively high in concentration, typically ranging from 500 to 5,000 mg/m³, making them suitable for regenerative thermal catalytic combustion. After being heated by regenerative ceramic bodies, the temperature of the exhaust gas rapidly rises to 700–800°C, at which point the organic components in the exhaust gas decompose directly into carbon dioxide and water vapor, forming odorless high-temperature flue gas. This flue gas then passes through lower-temperature regenerative ceramic bodies, transferring a large amount of thermal energy from the flue gas to the ceramic bodies, which is used to heat the exhaust gas to be decomposed in the next cycle. The high-temperature flue gas itself is significantly cooled, then further reduced in temperature through a heat exchange system before finally being discharged outdoors. The heated air can be directly introduced into the drying systems of gravure presses and laminators, saving substantial energy. Although regenerative thermal catalytic combustion makes full use of combustion heat, the organic solvents are not regenerated, and the process generates large amounts of carbon dioxide, which to some extent exacerbates the greenhouse effect.

5. Gravure-Based Thermal Transfer Printing Technology

In recent years, thermal transfer printing technology has made great strides and is widely used for surface decoration of products such as daily necessities, stationery, cosmetics, electrical appliances, and toys. Gravure-based thermal transfer printing involves pre-printing patterns on film surfaces using gravure printing, which results in rich layers, vibrant colors, and minimal color deviation, making it suitable for mass production. Subsequently, a thermal transfer machine applies heat and pressure in a single operation to transfer the exquisite patterns from the transfer film onto materials such as leather, textile fabrics, acrylic, metal, plastics, crystal, wood products, art paper, and stainless steel. After forming, the ink layer integrates with the material surface, creating a realistic and beautiful appearance that greatly enhances product quality. At present, some enterprises have successfully applied gravure-based thermal transfer printing technology to hundreds of products, including clothing, fabric bags, hats, throw pillows, mugs, ceramic tiles, watches, mouse pads, coasters, wall calendars, medals, and pennants.

6. Digital Printing Technology

In recent years, the flexible packaging industry has seen a trend towards shorter order runs, along with steadily increasing demand for variable information. Therefore, flexible packaging enterprises need to leverage digital printing technology to improve turnaround speed and meet market demands. Some flexible packaging companies in Europe, the Americas, and Japan are turning to digital printing solutions to rapidly process packaging products with optimal shelf display effects. In 2009, some domestic flexible packaging companies also adopted digital thermal transfer printing technology, inkjet technology, and coding technology when printing electronic supervision codes, achieving positioned printing of variable information. However, this is only monochrome digital printing and still suffers from issues such as low efficiency. In the foreseeable future, digitally printed flexible packaging products are likely to remain a relatively small part of China's flexible packaging industry.

7. PVA High-Barrier Water-Based Coating Solution

By utilizing existing coating machines, dry laminators, and other equipment available at domestic flexible packaging enterprises, applying 0.6–0.8 g/m² (dry basis) of PVA high-barrier water-based coating solution onto films with adequate surface tension (such as PET, BOPP, CPP, PE, NY, etc.) can significantly reduce the oxygen transmission rate of the film, even to less than 0.5 cm³/(m²·24h·0.1MPa), achieving barrier properties that surpass five-layer co-extruded films using EVOH as the barrier layer and PVDC high-barrier coated films, approaching the oxygen barrier performance of aluminum foil.

The packaging film product structure is as follows: black-and-white film PE / PVA / ink / adhesive / transparent PE. This structure offers the following advantages: since the ink is positioned in the middle of the composite film and not directly exposed on the film surface, ink loss is less likely to occur. Compared with five-layer co-extruded black-and-white films using EVOH as the barrier layer, the requirements for ink and cost are significantly reduced. At the same time, since both the ink and adhesive are located on the outer layer of the PVA coating, residual solvents from the ink and adhesive cannot penetrate into the packaging bag to contaminate liquid fresh milk.

8. Multi-Layer Co-extruded Composite Film Production Technology and Extrusion Lamination Technology

Due to their low cost and high quality, multi-layer co-extruded composite films are being increasingly widely applied in domestic flexible packaging and other fields, with market demand transitioning from predominantly three-layer structures to five-layer and seven-layer structures. The development and improvement of heat-adhesive resins and inner seal layer resins for extrusion lamination are advancing rapidly. In addition to LDPE, resins such as MDPE, HDPE, EVA, PP, LLDPE, EEA, EAA, EMAA, and various ionomer polymers are continuously being applied, greatly expanding the variety of extrusion lamination products. These resins not only offer good processability but also impart excellent post-processing properties to extrusion-laminated products, such as low-temperature heat sealability and heat adhesion.