Flexible Packaging Inks and Its Types
Flexible Packaging Inks and Its Types
Flexible packaging is printed using both flexographic and gravure printing methods and comprises a number of different end products. These would include but are not limited to packaging for:
- Confectionary products
- Cookies/biscuits
- Coffee
- Juice
- Food
From an ink point of view, inks for flexible packaging can be divided into surface printing inks and lamination inks. For the most part, flexographic and gravure inks share the same raw materials, so for this matrix we will group both printing methods together. Types of Flexible Packaging Inks are as follows:
Surface Printing Inks
Surface printing inks must have reasonably:
- High gloss
- Excellent rub resistance and
- Resistance to a number of different external elements, such as water,
solvents, detergents and other materials that may come into contact with the printed surface
These inks typically use a protective overprint varnish to increase the surface resistance and to impart the desired C.O.F. and gloss.
Lamination Inks
Lamination is the process of combining two or more substrates to form a tough packaging structure to hold and provide barrier protection for the contents.
Lamination can be accomplished with adhesives (adhesive lamination) or with molten plastic (extrusion lamination) that acts to adhere the packaging films together.
Lamination inks are typically sealed inside the lamination structure so that the ink surface is not exposed to the outside, however the inks must still exhibit excellent adhesion to the film on which they are printed and they must not interfere with the bonding of the lamination films.
The differences between surface printing inks and lamination inks are slight but important:
- Surface printing inks are typically formulated with waxes that migrate to the surface of the ink film to provide rub, scuff and other resistance properties. They must also have good gloss, particularly if they are not to be overprinted.
- Lamination inks do not have the gloss requirements of surface inks but they do require excellent bonding ability to ensure that the lamination structure isn't compromised after manufacturing. They typically do not incorporate a lot of waxes or surface active ingredients as these can often interfere with lamination bonding.
Common types of flexible packaging substrates include:
- Biaxially oriented polypropylene (BOPP)
- Cast polypropylene (CPP)
- Polyester (treated or coated)
- Nylon
- Cellophane
- Polyethylene (LLDPE/HDPE)
Raw Materials Used for Solvent based Flexible Packaging Inks
Raw Materials Used for Solvent based Flexible Packaging Inks
Additives and Their Functions
Select Waxes for Cold Seal and Hot Seal Flexible Packaging
The primary waxes used are Polyethylene,
Polypropylene and Erucimide waxes, which are used to impart slip to the ink surface.
Raw Material |
Rub resistance
|
Scratch
|
Slip
|
Water resistance
|
Gloss
|
PE Wax
|
Excellent
|
Excellent |
Excellent |
Poor |
Moderate
|
Erucimide/stearamide
|
Fair
|
Excellent |
Excellent
|
Good |
Fair
|
PP Wax
|
Excellent
|
Excellent
|
Excellent |
Poor
|
Fair
|
Silicone
|
Fair
|
Excellent
|
Excellent
|
Moderate
|
Excellent |
PTFE |
Excellent
|
Excellent
|
Moderate |
Moderate
|
Poor
|
Cold Seal Packaging
Many temperature sensitive confectionary items (e.g. chocolate) are packaged and sealed using cold seal adhesives. These surface printed constructions consist of a surface printed ink and a cold seal release lacquer (CSRL), which prevents the printed ink from offsetting against the cold seal glue when in the printed roll.
Inks for cold seal packaging should not be formulated with any kind of fatty amide (erucimide) or PFE waxes as these can "poison" the cold seal adhesive if left in contact with the adhesive for any length of time in the printed roll.
Heat Seal Packaging
Both surface printed inks and lamination inks can also be heat sealed. In this instance a heat sealable film is used or a heat sealable coating is used to combine two films by applying heat to achieve the seal. Sealing temperatures and pressures can vary so when formulating these types of inks, it's important to know and test the inks under these sealing conditions. A typical sealing specification may be 350 degrees Fahrenheit for half a second at 40p.s.i.
» Learn How Wax Emulsion Help Improve Properties of Inks
Select Resins for Flexible Packaging Inks
Ink Formulations for Flexible Packaging