Products
Home > Products > Lamination Films

Lamination Films

Introduction
In today’s market, properties expected out of packaging are phenomenal. To keep up with these ever growing market demands the industry has adopted laminating two or more substrate which allows advances packaging techniques.

The lamination is the process of bonding together two or more substrates together with the help of adhesives.
Earlier only solvent based adhesives were known and used. These adhesives are made up of two components adhesive and additives which are mixed using solvents as the carrier.

A typical example is polyester or BOPP is reverse printed and then laminated with LDPE. In this case printed polyester or BOPP is put on the primary unwinder then printed surface is passed through the coating head and adhesive is picked up. The substrate is then passed through the drying tunnel. Adhesive is dried to the extent that it becomes tacky. Heated air flow is used in the drying tunnel. All the solvents in the adhesive are removed by evaporation. This film is then brought to the nipping station where it is bound together with the secondary film. Nipping station consists of one chrome plated roller and one rubber roller. The chrome plated roller is heated from inside and the temperature is kept around 70 degree Celsius. This is done to keep the adhesive in tacky condition when bonding is taking place.

The laminate so created is cooled and brought to the room temperature and then rewound. It is then kept aside for curing .

The adhesives are either polyurethane based or polyester based with poly isocyanate based additives. These adhesives are of high molecular weight and generally exhibits good initial bond ( Green Bond ) which goes on to become excellent after curing the laminate typically between 48 to 72 Hours.

Adhesive coating weights are normally between 2.5 to 4 GSM depending on kind of substrate area of print etc. While there are many applications for flexible packaging laminates, there are relatively few key performance requirements that they all share. The adhesive must have excellent clarityand bond strength as well as be resistant to heat and humidity.

Solvent based laminates normally exibit a Green bond of 75 to 100 gms / 25 mm and cured bond strength of around 350 to 400 gms per 25 mm. In case of solvent less adhesives green bond is almost nil and cured bond strength is same as that of solvent based laminate.
Films for Lamination
For many applications in flexible packaging, the use of a single material may not satisfy all of the properties demanded of the product. In these cases, a composite consisting of two or more layers of material may provide the desired performance. A particularly common means of creating such a composite is to laminate various polymeric films to other films, foils, papers, etc. with a polymeric adhesive.

This production solution is commonly employed in the packaging industry where the end-products require multi-functional properties, such as high tensile strength and high gas permeability. These are generally referred to as barrier films. The laminate construction can become rather complicated due to the nature of the specific application. A typical laminate used in the medical packaging industry, for example, may be multi-layer composite containing films of polyester / polyethylene / metal foil / polyethylene.

The variety of modern flexible packaging products that are available today would not be possible without modern adhesive systems. The evolution of the packaging industry has closely matched the development of new adhesive materials and production processes. These trends have led to high quality and technically demanding packaging structures required by the consumer.

The physical and chemical characteristics of the substrate itself will influence the choice of adhesive and coating method to be employed. The substrates that are used in the manufacture of flexible packaging fall into three main categories: papers, foils, and films. By far films are becoming the dominant material because of their lightweight, strength, disposal, and cost characteristics.

Common polymeric films that are used in flexible packaging are:
  • High and low density polyethylene
  • Linear low density polyethylene
  • Cast and oriented polypropylene
  • Ethylene-vinyl acetate
  • Polyvinyl chloride
  • Cellulose (plain and coated)
  • Cast and oriented polyamide (nylon)
  • Polyester
  • Metallized film
  • Coated (polyvinylidene chloride or acrylic) film
The Flexible Packaging Industry uses multi layer polyethylene and co-polymer films for laminating to one or more substrates, such as polyester film, polypropylene film, often in combinations with Aluminium foil and/or paper, depending upon the packaging system. The multi layer film forms the inner most layer – the Heat Seal Layer – of the laminate, which is in contact with the product.

In a multi layer film the polymer, the equipment and the process variables combined, determine the level of crystallinity and orientation and in turn the resulting film properties.

The design of a multi layer film structure is based on pre-determined performance characteristics such as
  • The film / product compatibility.
  • The lamination process.
  • Machinability on the packaging line.
  • Heat seal characteristics that matches the requirements of the packaging line.
  • Storage (Shelf life ), handling and transportation conditions.