Laminated Packaging Bags Materials: The Future of Food Safety and Quality

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    Laminated Packaging Materials in Food Industry

    A simple plastic wrap film often fails to meet the demands of safeguarding, enhancing, and fitting the needs of goods processing. Hence, a superior choice exists—Laminated packaging material, which merges multiple layers of identical or diverse packaging materials. This combination balances out the limitations found in a singular material by harnessing the best traits from each layer. Laminated materials now play a dominant role in food packaging bags.

    Understanding the Layers of Laminated Materials

    The core makeup of Laminated materials can be described as follows: The external layer typically comprises a heat-resistant, high-melting point material capable of enduring thermal stress without easy damage and allows for clear printing and optical clarity. Materials like paper, aluminum foil, glass paper, polycarbonate, nylon, polyester, and polypropylene are preferred for this. The inner layer should possess qualities such as strong sealing, adhesiveness, neutrality in taste, non-toxicity, and resistance to oils, water, chemicals, etc., using heat-resistant plastics like polypropylene, polyethylene, and polyvinyl chloride.

    For Laminateds with three or more layers, the intermediate layer is usually made from substances excellent at blocking gases and moisture and with significant mechanical strength, such as aluminum foil, polyvinyl chloride, glass paper, paper, polyethylene, and the like. Adhesive layers that bond these materials often use solvent-based thermosetting polyurethane for outer and middle layers and modified polypropylene emulsion or specially tailored carbonyl propylene copolymer resin between the inner and middle layers.

    Advanced Adhesives and Coatings

    The outer layer needs a strong bond adhesive that's cost-efficient and straightforward in application, while the inner layer adhesive must tolerate high temperatures, have strong peel qualities, be non-toxic and flavorless, not alter the food's nutritional composition, and should preserve the food's natural color and taste well. Recent international advancements include applying a coating to the base film's surface, enhancing its air tightness, oil resistance, and chemical durability, rendering it suitable for diverse food packaging. Among the used coatings are polyvinyl chloride resin and polypropylene-polyvinyl chloride resin with methods such as single and double-sided applications.

    Laminated Variants and their Applications

    Current go-to materials for food packaging Laminateds include dual-layer examples like glass paper/polyethylene and paper/aluminum foil, and triple-layer items like stretched polypropylene sandwiched with polyethylene. For detailed insights, see the PVC heat shrinkage and cold expansion article in the same issue. Multi-layer Laminateds adding up to four or five layers—like glass paper/polyethylene/stretched polypropylene—enhance the barriers even further. Additionally, a six-layer construction featuring polyethylene and aluminum foil layers is employed.

    Chlorinated polyethylene (CPE)—a white, tasteless, and non-toxic saturated polymer with excellent weather and chemical resistance, including to oils, flames, and aging—is highlighted for its resilience even at very low temperatures and compatibility with a variety of polymers. It's generated through a chlorination reaction of high-density polyethylene and falls into either resin-type (CPE) or elastomer-type (CM) categories, usable on its own or combined with other plastic materials including PVC, PE, PP, PS, ABS, and even PU.

    The Retort Pouch – A Packaging Innovation

    The retort pouch is an epitome of Laminated film packaging capable of withstanding high-temperature sterilization, initially crafted for astronauts in the USA and later mass-produced in Japan since the 1960s, with an annual consumption of 500 million bags. The retort pouch's popularity and production are expanding in the United States, Germany, and beyond at a brisk rate. It boasts advantages over glass and metal containers such as a secure seal, aesthetic appeal, lightness, durability, and portability.

    Divided into standard and ultra-high temperature sterilization bags, their composition varies from two layers for the former to multiple layers, including aluminum foil, for the latter, ensuring the preservation of foods for up to two years. The retort pouch uses polyester for exterior strength and heat endurance, aluminum foil in the core for gas, moisture, and light barriers, and for the part in direct contact with food and heat-sealing, non-toxic polypropylene or HDPE is utilized. Retort pouches are mainly for packaging preserved food and are also employed for encapsulating beverages and juices in Japan and Western Europe.

    Food Packaging as a 'Special Food Additive'

    Various pivotal dynamics affect the security of food packaging, which acts as a 'special food additive'. It represents the final phase in the modern food industry and has grown inseparable from food products itself. However, challenges mar China's food packaging sector where packaging stands as food's intimate attire.

    The integrity of raw and supplementary materials alongside the processes can directly influence food quality and human health. Predominantly, plastics are the materials of choice for packaging, but under certain conditions, the polymer monomers and additives in these plastics may leach, posing health risks upon transferring to food or medicines.

    Safety Risks and the Integrity of Packaging Materials

    Packaging materials can retain harmful substances emanating from the packaging materials themselves, particularly the inks and solvents in the printing process, which contain hazardous chemicals like benzene and halogenated hydrocarbons. These substances not only threaten worker health during manufacturing, risking poisoning incidents but also destabilize labor-capital relations and societal equilibrium.

    High-polymer materials such as polyethylene and polypropylene are the mainstays for soft food packaging materials. The right choice of packaging material is crucial for food manufacturers, for mismatches can lead to food safety issues like the shortening of liquid milk's lifespan or the hastened spoilage of vegetables due to improper fresh-keeping films. PVC cling film's potential harm arises from two factors: the excess of residual vinyl chloride monomer and the presence of DEHA plasticizer, which releases upon contact with heat or oils and can impact health. Bisphenol A, prevalent in plastic packaging, internal can coatings, and adhesives, leaches into food when heated and exhibits estrogen-like effects; recent animal studies point to a possible linkage between bisphenol A and an increased breast cancer risk.

    Printing Ink and Process Considerations in Food Packaging

    Printing Ink

    Across the spectrum of food packaging films, the demanded ink attributes cover general adhesive strength, wear endurance, and the ability to endure sterilization, boiling, and cold temperatures, ensuring the ink remains steadfast during transport and storage.

    Printing process

    The manufacturing of food packaging bags predominantly utilizes gravure printing, seen en masse in supermarkets. However, many Western nations prefer flexo printing for its environmental benefits, despite its slightly less refined dot performance compared to gravure.

    Thanks for you time to read KanzoPack’s blog, if you have any questions or inquiry about packaging pouch, please feel free to contact with us.

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