Understanding IPA and IPA substitutes, part II

Reducing IPA is a step-by-step process. For this, one must obtain support from the management and the printers, analyze the process water as to the use the proper fount and explain why the water levels will go up. One also needs dosage control and regular checkups.

Do not take the big steps (from 15% to 0% is likely to fail) but take small steps that will allow printers to get used to it and allow the press to get used to it and allow the printers to adjust the press-settings to optimise where needed.

Approaching the 4% IPA, try to convince to use the hydrophilic dampening rollers.

Alcohol substitutes are basically solvents known as glycol ethers with surfactants. They are normally used at 1/5 to 1/10 the level of alcohol which correlates to approximate levels of 1 to 5% of the chiller capacity depending on type of press, dampening system, ink used and plate type.

Replacement with a substitute

To replace Isopropanol, many companies have introduced complete, low volatility solvent replacements. Dosed at 1 to 5%, they offer low flammability and zero VOC content. It removes isopropanol from the equation, improves gloss, reduces vapour and odour, and reduces fire hazard.

However, it introduces problems of its own. It is toxic. It is damaging to positive working plates; it is difficult to control accurately and it swells rubber rollers.

IPA

IPA presents a fire and explosion hazard. It is absorbed through the skin and has the potential to become a carrier solvent. This means any foreign material dissolved in IPA will be carried through the skin membrane. Again, the greater the concentration of IPA, the greater the health hazard it presents. IPA removes the plasticisers from the rubber, causing the rubber to harden.

In the manufacturing of rubber and chrome rollers, lines are created on its surface. IPA is known to ‘bridge’ these lines and therefore, they do not appear in the print. This is why IPA is known as ‘friendly’ to the printer as it hides faults such as these and still print optimally.

Substitute

The substitute is a known skin-irritant and presents a significant health hazard when used as a concentrate. Safety precautions should be used when dispensing either of these materials. Disposal requires due care of ETP.

In many cases, the substitutes do not bridge these lines and requires rollers to be polished and/or desensitised. Roller settings may need to be adjusted or in some cases the rollers may need replacement. It will require some setting change at least. Therefore, without the buy-in of the printer/operator, this is not successful many times.

Total removal of solvents/ alcohol

1 If the print shop is committed to go solvent free completely, then run the press at <8% alcohol for a month (6% with ‘reducing’ founts) and address all problems that arise without increasing alcohol content

2 Ensure that the fount doser and thermostat are working well by performing an audit of damping water conditions hourly for a month

Ensure that the damping system is clean and that the rollers are of the recommended hardness or at the minimum, glaze-free. Apply an ideal deglazer

Discuss plans for total elimination with the press, ink and chemical supplier and most important of all, the user team.