Specifying Inks and Coatings

The seven phases of a package's life

As trite as it is, the phrase "garbage in, garbage out" is still applicable to the hardware and raw materials used in the production of a package. "Pressmanship" cannot make up for all of the potential failures and/or possible complications that can arise during the conversion, print storage, filling, filled package storage, shipping, final use, and disposal of that package. It therefore becomes crucial for the package developer and converter to anticipate every aspect of these seven phases in the life of a package.

Ink used for printing is a major player in the packaging production process. Unfortunately, many converter orders sound just like this: "I need 100 pounds of each process color, plus Pantone®* XYZ for a job that's going on press tomorrow." That's it! The ink maker is then expected to immediately predict a complete set of requirements for these inks.

Other than going by established color standards, and being familiar with the particular press conditions, there is no way for an ink supplier to completely forecast all of the ink properties required for the seven stages of package life. Fortunately, in a majority of cases, just by knowing the end use of a package, ink makers can provide inks that will meet the needs. But overlooking just a single need can cause failure. Years ago, I was visiting a package designer who proudly showed me a beautiful package he had recently designed for this year's "line." The primary color was a clean bright magenta that only a rhodamine-based pigment could match. Had I not questioned the need for fade resistance, our formulator would have matched the color, only to have the package fail out in the field. Without the proper information, formulating an ink is a disaster waiting to happen.

How, then, can we avoid this problem?
In order to formulate an ink or coating for packaging use, the ink maker must team with the converter, and often the package buyer, to get the full range of requirements. If the converter and package buyer are well schooled in the prerequisites for the package prior to placing the ink order, a great deal of time can be saved, and there will be significantly less chance for a failure out in the field. The question is, how can this be done?

It's not really difficult if one just takes each of the seven phases in the life of the package and thinks about what the package will or could be subjected to during each phase. This will lead to the properties required for the ink and/or the package. From this, the team can establish test methods. These can be procedures developed for just that one package, or, more likely, already established standard test methods found either in the ASTM book of standards or in a printing ink manual. Once test methods have been agreed upon, the specifications must be set. These must be well thought out, must take into account the worst possible scenario, yet must still be reasonable enough to be met in a production situation.

7-Phase Checklist
I have found it helpful to think out each phase in order to assure that nothing is overlooked. Each phase can then be further divided to assure that no need, no matter how insignificant it might seem, is overlooked. Completing the following checklist provides a good base of information for an ink formulator, and will help insure that the ink maker takes all requirements into consideration.

PHASE I: CONVERSION
 

• What is the substrate?
   
  • Rigid or flexible
  • Porous or nonporous
  • Paper or board
  • Coated or uncoated
  • Film
    • Type (polyethylene, polypropylene, polyester, etc.)
    • Slip package
    • Treatment level
    • Primed or unprimed
    • Clear or opaque

This information will help the ink formulator determine the proper formulation for adhesion and printability on that specific substrate.
 

• What will printing conditions be?
   
  • Roll-to-roll, sheetfed, or roll-to-sheet
  • Running speed
  • Drying capability
  • Plate
  • Ink fountain configuration
  • Ambient pressroom conditions

This will allow the ink maker to deliver an ink with the required color strength and general press runnability.
 

• What are the decorative properties required?
   
  • Color
  • High gloss
  • Matte finish
  • Low odor
     

Because these properties are generally fashioned to attract the consumer, they are extremely critical and must meet the specifications of the package buyer.
 

• What are the environmental and food packaging regulatory
  considerations?
   
  • Maximum VOC level
  • HAPs
  • Heavy metals
    • CONEG
    • Toy Specs
  • Direct or incidental food contact
  • Waste ink disposal

Care must be taken to assure that current regulations are completely met.
 

• How will the package be converted after printing?
   
  • In-line conversion
  • Off-press conversion
  • Die cutting, scoring, embossing, etc.
  • Heat-sealed
  • Hot-stamped
  • Hot-waxed
  • Laminated

This information will determine which properties, such as heat resistance, wax bleed, score pick resistance, bond strength, etc., are required for the dry ink film on the substrate or in the laminate.

PHASE 2: PRINT STORAGE

• What are the ambient storage conditions?
• Is print storage roll-to-roll or stacked sheets?

This information is necessary in order to formulate block and offsetting resistance into the ink.

PHASE 3: FILLING OPERATION

• Must the package slide easily over another package (i.e., plastic bags sliding over one another as they're being pulled from a wicket)?
• Must the package move under its own power down a conveyor?
• Are there any line lubrications used that can come into contact with the package?
• What product is being put into the package?
• Is there any excessive abrasion by belts, conveyors, etc., during the filling operation?
• Is the filled package heated, sterilized, refrigerated, quick frozen, or washed down after the filling operation?
• Is the filled package stacked on pallets?

This information is very critical to determine if a minimum or maximum coefficient of friction (COF) or slide angle is required. Also, it will indicate the need for chemical, product, (i.e., soap, grease, alcohol, etc.), temperature, moisture vapor transmission, water, steam and rub/abrasion resistance.

PHASE 4: SHIPPING

• Under what conditions are the filled packages shipped (i.e., are they strapped, in a larger carton, bagged, etc.)?
• Is there a possibility of exposure to heat, humidity?
• Is the transporter (truck, boxcar, etc.) refrigerated?

Formulators may have to build in temperature, moisture, moisture vapor, water, and rub-abrasion resistance for extreme shipping conditions.

PHASE 5: FILLED PACKAGE STORAGE

• What are the ambient storage conditions?
• Is there any refrigeration involved?
• How are the packages stored (pallets, stacked, etc.)?
• Is there store shelf, window or outside storage involved?

Light, weather, temperature, moisture vapor transmission and block resistance, as well as COF can be formulated into inks or coatings to meet these conditions. If refrigeration is involved, ammonia resistance is usually a requirement for the inks and/or coatings.

PHASE 6: END USE

• Is there a chance the product will contact the printed surface (i.e., soap, alcoholic beverages, milks, etc.)?
• Will the product be refrigerated or heated in the package?
• Is the package designed for microwave heating?
• Is the package designed for boiling in water?
• Is the product sterilized (steam, gas, radiation, etc.) in the package prior to use?
• Where is the product stored after purchase?
  • Outdoors
  • Humid basement
  • Storage shed
  • Refrigerator

These conditions might require that product, chemical, solvent, grease, alkali, light, weather, water, moisture vapor or temperature resistance be formulated into the ink.

PHASE 7: PACKAGE DISPOSAL

• Landfill
• Incineration

All of the environmental regulations must be known in order to assure compliance for the proper disposal of a printed package.

Potentially Serious Consequences
During my 36 years in the ink business, I have seen a wide variety of ink-related failures in the production and life of a package. Several years ago when wax-coated drinking cups were very common, I received a call from a converter complaining that their wax bath was turning yellow during the waxing operation. In this specific case the cup was printed with red and brown inks, thoroughly dried, and subsequently passed through a trough of molten wax. The wax in the trough had turned yellow, producing a yellow cast on the non-image areas of the white cup.

The first action taken was to examine the ink formulas. The brown ink called for an AAOT diarylide yellow (which is wax-bleed resistant), a wax-bleed resistant red pigment, and a carbon black. The red ink was mono-pigmented, and formulated with a wax-bleed resistant red pigment. On reviewing the actual batch tickets for each ink, however, I discovered that an AAA diarylide yellow had been substituted in the brown, because the plant had no AAOT yellow in stock. Unfortunately, the lab technician who approved the substitution was not aware that this ink was for wax cups. Had he been informed, there would have been no approval for substitution because AAA diarylide yellows are notorious for bleeding in wax.

Another incident typifying the need for complete, and not partial, information occurred when the R&D lab of an ink company was required to develop a very high gloss water flexo ink system for a beverage bottle label. No indication was given that the beverage was to be an alcoholic drink. A fine set of highly water resistant inks was developed, and proofs were submitted to the printer. The ink company looked very foolish when the inks were rejected for not having alcohol resistance. The salesperson just didn't ask the right questions, and brought incomplete information back to the lab.

In this latter example the salesperson felt it would be too "pushy" to ask numerous questions. It is difficult to believe that any converter would think that of a salesperson if the reasons for the questions were understood.

While all of this may seem very elaborate and involve a great deal of detail, it is a necessity if problems are to be avoided. Only after all of the phases in the life cycle of a package have been considered, and assurance of testing or analytical certification has occurred, can one feel secure that there will be no failure in the package in the field.

*Pantone Inc.'s check-standard trademark for color reproduction and color reproduction materials.