Water Based Cleaning Technology - Cleaning Methods and Systems

Since the entry into force of the 31st ordinance on the implementation of the German federal immission protection law (BImSChV), all companies using processes whereby VOCs are emitted are called upon to reduce the quantity of VOC emissions by pre-vention or treatment.

Many users of cleaning processes involving volatile solvents are now faced with the decision of investing into an exhaust air treatment system or switching to a different cleaning method.

The principal criteria to be considered in the decision for or against using solvents that cause VOC emissions are the ecological and economical problems of exhaust air treatment and the technical requirements that must be met by technologically ad-vanced cleaning systems.

Demands made on the cleaning technology and the cleaning systems

The demands made on modern cleaning methods and technologies are dictated by the technological improvement of inking and varnishing systems, the chemical and physical properties of the parts to be washed and the increasingly strict environ-mental and industrial safety regulations. At this time, users can choose between cleaning technologies with chemicals and chemical-free technologies with limited ap-plicability and effectiveness.

That is why, for a few years now, water-based cleaning systems and machine-supported cleaning technologies have been used successfully for a wide range of cleaning tasks. Water-based cleaning methods, washing solutions generally pro-duced through dilution with water, emit little or no organic substances and are hence particularly sustainable in both economical and ecological terms. The machine-supported aqueous cleaning systems that are now widely used produce much better cleaning results and are hence increasingly used for cleaning tasks accompanying production.

From today’s perspective, alternative VOC-reduced cleaning systems, e.g. systems based on high-boiling solvents, will mainly cover cases where water would cause un-desired problems, especially during inline cleaning.

Selecting the cleaning technology/cleaning system

The choice of technology – spraying or immersion with ultrasonic cleaning – and of the system – water-based and neutral to alkaline – is determined by the parts to be washed and, to a considerable extent, by the chemical and physical properties of the washing agent, and the contamination.

Another important factor is the efficiency of the technology and the cleaning system. Spraying furnishes better cleaning results than other technologies in practically all cleaning applications involving inks. Water-based cleaners, especially systems com-bining chemical and mechanical cleaning, have a higher dirt absorption capacity and show a more effective dissolution of dried and hardened ink than solvents.

A combination of spraying technology and a water-based cleaning system is a very powerful and environmentally friendly cleaning method for the printing and dyestuff industry. Another important benefit of water-based cleaning is the greater freedom in designing machines, since there is no need for explosion protection equipment and exhaust air treatment.

Applications of cleaning technology

Cleaning of screen rollers and impression cylinders

Cleaning screen rollers and impression cylinders is no easy task; as their surface structures grow more complex, they make higher demands on the machine and the washing agent.

The combination of a water-based cleaner with chemical and physical cleaning effect and the spraying technology ensures a quick and complete dissolution and removal of ink from the small cavities in the surface profile of impression cylinders and screen rollers.

High cleaning power and low consumption

The cleaning of printing unit parts is a time-consuming task that requires large quantities of solvent. Spray cleaning with water-based cleaners combining a chemical and physical cleaning effect is an economical and VOC-free alternative. This cleaning method is characterized by a considerably shorter washing time compared to the sol-vent method and the high dirt absorption capacity of the water-based cleaners.

Wide range of application and high effectiveness

Printing processes use a wide range of inks and organic coatings whose solubility changes considerably even during the process as a result of chemical conversion and physical influences. This calls for time-consuming cleaning that does not furnish the desired results when common solvents are used. Aggressive cleaning chemicals and methods do not represent a viable alternative, since they chemically or physically abrade the material of the parts being cleaned.

Better to choose cleaners that are adapted to the material and gently remove ink and organic coatings. Such cleaners must ensure effective cleaning while inhibiting corrosion and preserving the material, properties that are particularly easy to achieve with water-based cleaners.

Summary:

The necessity of improving climate and immission protection calls for a more restric-tive handling of substances and processes that cause emissions, particularly in in-dustrial surface treatment and cleaning. One way of meeting this requirement is by replacing these substances and processes by others with little or no emissions. The water-based cleaning technology consisting of a cleaning system with chemical and physical effect and the spraying technology represents a highly efficient and economical method of removing ink and organic coatings.

Authors:

Dr.Thomas Werner
Head of Research and Development
Working in industrial R & D of surface chemistry and technology processes since 1992.
KS Chemie GmbH

Dipl. Ing. Eberhard Künnemann
Head of process technology
D.W.RENZMANN Apparatebau GmbH