Guidelines for Using DigiPrime^® Icon for Off-Line Coaters

Michelman’s DigiPrime® Icon brand of primers, designed for converters who prepare substrates off-line, provides several performance advantages including better runnability, cleanability, lower odor, and superior adhesion.

The primers, which are press-ready, water-based, and designed for flexographic or gravure applications, optimize most film and paper substrates. They are very stable in liquid form, with a shelf life of 12 to 24 months if stored unopened at moderate temperatures. Coated substrates have a shelf life of 12 months or more and will not yellow or show degradation of print quality or adhesion.

These guidelines are applicable for DigiPrime® Icon 8000, DigiPrime® Icon 8010, and DigiPrime® Icon 8020.

Application Preparation

Clean the coating system thoroughly by flushing the supply lines and pumps with clean water, then cleaning the coater pans and rollers. Many ink or water-based primer chemistries used in the conventional printing industry can be incompatible. Do not use solvent-based cleaners. DigiPrime® primers will react negatively, becoming very viscous and dense.

Drying

A minimum web temperature out of the dryer/oven between 45-60°C is required to obtain full adhesion after drying. The web must cool to less than 30°C before rewinding the roll to prevent blocking. It is essential to have good drying in order to stock the primed reels in the right condition. Primed reels are equipment that should be appropriately stored, until printing, in a cart where the reels can be hung or placed vertically. Both ways eliminate the pressure on the primed reels, avoiding their possible blocking and deformation. Proper drying is critical for adhesion, block prevention, and correct end specifications.

Application and Cleaning

DigiPrime® off-line primers should not be allowed to dry on the anilox. Keep the coater moving, rollers turning, and surfaces wet. Water or water/soap mixture is the preferred method for clean-up, but the following suppliers also offer suitable cleaners:

Coat Weight

The recommended target coat weight of DigiPrime® on most surfaces, undiluted, is 1-1.5 gsm wet. However, depending on the absorbency or texture of a surface, higher coat weights may be needed and should be established by experimentation. Excessive coat weight may result in blocking the wound roll, and coat weight that is too high or too low may result in a lack of adhesion. Verify the coat weight and apply the primer according to substrate type.

Substrate Selection

Quality primer adhesion involves combining Michem® Indicator 001 with a tape test:

• Verify the proper coating lay-down quality with Michem® Indicator 001.
• Facilitate a tape test.
• Repeat the use of Michem® Indicator 001 across the same section as the tape test.

Materials and process for quality ink adhesion include:

• 3M 810 Cellophane Film Tape (for film)
• 3M 230 Masking Tape for paper
• Perform tape test three times:
  1. Immediately after printing
  2. 15 minutes after printing
  3. One hour after printing

86% of the ink adhesion should be achieved after 15 minutes.
(3 Star HP Indigo Media Certification)

Monitoring Coat Weight

Monitor the use of DigiPrime® off-line primers over a known length and width of media:

• Coat weight (gsm) × Length (m) × Width (m) = Consumption of DigiPrime® (g)
• Example: 1 wet gsm of DigiPrime® × 1000m × 0.300m = 300 grams

Gravimetric Method: Checking coat weight on plain films can be achieved by measuring the weight difference. Obtain an accurate balance because of the very low dry coat weight.

Recommended Coat Weight

Primer Specification