Alcohol Substitutes: Metering Rubber Rollers Used for IPA-free Dampening systems

Some years ago, the world was facing a shortage of isopropyl alcohol (IPA). subsequent environmental, health and safety regulations added their limitations to using alcohol and continue to pressure on offset printers to reduce the use of volatile organic compounds VOCs.

In lithographic printing, the dampening unit transfers a water-based solution to the non-image area of the printing plate making it ink-repellent. IPA is a Worldwide popular dampening solution additive that reduces its surface tension and increases its viscosity making it wetter and easier to spread across the printing plate. this allows a thicker film of dampening solution to interact with the ink and the non-image areas of the plate.

IPA based dampening solutions have been accepted with making the printing process with less troubles, masking problems that can occur due to improper offset printing rollers settings, lack of operator skills and lack of printer maintenance.

Today, printers around the world facing a challenge of substituting IPA due to severe supply shortage and due to health and safety concerns and regulations. IPA free-printing, however, offers great advantages over the IPA-printing, one of the benefits is better quality printing with sharper colours and less tendency to emulsification.

Several kinds of IPA substitutes are available. They are formulated with one or more chemicals from the glycol and glycol-ether families plus other additives that perform the functions of alcohols. in the beginning substitutes were formulated to be used with a small amount of IPA, but today formulations are completely replacing alcohols while offering their own range of properties.

Working with IPA Substitutes.

there are two goals when replacing IPA. the first is to manufacture a quality product while using safe materials and the second is to choose the right IPA substitute that will give the optimum results. this choice depending on the press, the dampening equipment, the water, substrate, ink and even the printing job. printers can not expect to change one aspect without expecting to adjust others.

The key to successful alcohol-free printing is the hardness and nip relationship of the dampening unit rubber rollers. Major thoughts should be given to the metering rubber roller, which requires lower hardness than when running IPA. Metering rollers are normally supplied with a shore hardness of 25–30 and sometimes will harden during service.

It is recommended that the hardness of the metering rubber roller be reduced to 18–22 when running IPA substitutes. Softer rollers tend to have better water loving characteristics. Their softness increases the width of the nip between the metering roller and the chrome roller without increasing the pressure, giving press operators more adjusting latitude.

Lichaa is a Chemical Engineer at TRAD Rollers, a senior compounder specialised in the formulation of rubber rollers compounds for the printing industries.