Flexible packaging is extensively being used for packaging food, personal care and consumer goods. The lamination process plays a key role in manufacturing flexible packaging where adhesives are used to bond different material layers together such as films, papers and foils. This article aims to provide insights into lamination adhesives used for flexible packaging, their types, properties, advantages, and applications.
Types of Lamination Adhesives
The major types of adhesives used for flexible packaging lamination include solvent-based adhesives, water-based adhesives, and hot melt adhesives.
Solvent-based Adhesives
Solvent-based adhesives have traditionally been used widely in flexible packaging lamination due to their strong bonding properties and high productivity. They contain organic solvents to dissolve adhesives which provides excellent adhesion to various substrates. However, solvent-based adhesives release VOCs and have other environmental issues. Newer formulations with lower VOC content are being developed to make them more eco-friendly.
Water-based Adhesives
Water-based adhesives have lower VOC emissions compared to solvent-based ones making them a sustainable alternative. They utilize water as the carrier solvent and the adhesive is in the form of an emulsion or dispersion. Water evaporates during drying leaving the adhesive bonded to the substrates. However, their bonding strength and productivity is relatively lower than solvent-based adhesives. Further improvements are being made to enhance their performance.
Hot Melt Adhesives
Hot melt adhesives are solid adhesives that are heated and applied molten on the substrates. They instantly cool down and bond the substrates. Being solvent-free, hot melt adhesives emit zero VOCs and have a very high productivity. However, special hot melt equipment is required for their application. Developing hot melt adhesives with competitive adhesion properties remains an active area of research.
Properties of Adhesives for Flexible Packaging
The key properties required in lamination adhesives for flexible packaging application include:
- High Bond Strength: Ability to form extremely strong and durable bonds between substrates that can withstand stresses during packing, transportation, storage etc.
- Heat and Water Resistance: Ability of the adhesive bond to withstand exposure to heat, moisture and humidity without delamination. This ensures packaging integrity.
- UV Resistance: Ability to withstand UV light exposure without bond degradation as flexible packages are often exposed to sunlight.
- Low Viscosity: Adhesives require low viscosity for uniform application as thin adhesive films.
- Short Drying Times: Fast drying and setting is required to increase lamination productivity and line speed.
- Chemical Resistance: Resistance to chemicals, acids, oils, which may come in contact with packaging during use.
- Clearness: Transparent nature of adhesive film for packaging where visuals need to be printed or seen through the package.
- Non-toxicity: Adhesives must be non-toxic and suitable for food contact applications as per food safety regulations.
- Low Odor: Adhesives with negligible odor prevents imparting undesirable smells to the packaged products.
Applications in Flexible Packaging
Lamination adhesives are used in various flexible packaging applications ranging from simple to complex multi-layer constructions. Some key applications include:
- Pouch Lamination: Bonding films to films or films to papers to form stand-up pouches for snacks, coffee, pet food etc.
- Carton Lamination: Lamination Adhesives For Flexible Packaging of paper board to films for carton packaging of juice, milk, frozen food etc.
- Roll Stock Lamination: Forming film laminates in roll form for subsequent bag or pouch making.
- Wrapping Films: Bonding cast stretch films or cling films used for primary wrapping of various products.
- Lidding Films: Lamination of films onto trays, cups or other rigid containers to provide peelable seals for food service packaging.
- Label Laminates: Producing self-adhesive label stock by laminating films onto paper or other substrates.
- Blister Packs: Lamination of thermoformed films or foil onto rigid supports to form tamper-proof blister packs.
Advantages of Lamination Adhesives
The usage of lamination adhesives provides multiple advantages to flexible packaging manufacturers and brand owners:
- Superior Package Integrity: Strong adhesive bonds provide burst strength and resistance to damages during distribution of packaged goods.
- Protection from Environment: Properly bonded packages can withstand effects of moisture, heat, pressure changes during storage and transportation.
- Increased Aesthetics: Glossy and transparent adhesive films improve visual appeal and print quality on packaging surfaces.
- Tamper Evidence: Lamination helps incorporate tamper-evident features and seals keeping product freshness intact.
- Extended Shelf Life: Strong barrier from external elements helps preserve contents and extend shelf life of packaged products.
- Downgauging Potential: Thinner films may be used for lightweight packaging by relying on adhesive strength rather than film thickness alone.
- New Design Options: Adhesive lamination enables combination of different materials in novel and customized packaging formats.
- Automated Packaging Lines: Lamination facilitates high-speed packaging operations on fully automated lines with increased output.
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