SubscribeEver since the 31st German Federal Immis-sion Ordinance (31. BImSchV) entered into force in 2001, all companies generating VOC emissions are required to reduce the amount of these emissions.
Many users of cleaning processes involving highly volatile solvents are faced with the choice of investing in an exhaust air treatment system or switching to another cleaning method altogether.
The essential criteria governing a decision for or against VOC-emitting solvents are
- the ecological and economic difficulties of exhaust air treatment
- the increased requirements regarding the safety of solvent cleaning systems (according to ATEX)
- the necessity of improving the effective-ness of cleaning systems for new ink and paint systems.
Technological progress in the paint and varnish industry has led to the development of ink and paint systems with new properties. There is a strong tendency towards water-based inks and paints. Traditional cleaning methods, however, are not suitable for these new substances. They do not meet the increasingly strict requirements regarding environmental protection and occupa-tional safety, nor do they offer the necessary range of application for the different ink and paint systems.
That is why, for a few years now, water-based cleaning systems combined with mechanical cleaning technology have been used success-fully for these cleaning applications. By nature, water-based cleaning systems - washing agents produced by dilution with water - emit virtually no organic substances and are therefore particularly sustainable from an economic and ecologi-cal viewpoint.
These systems, which have been used for more than 10 years by the automobile industry to remove paints and varnishes, can in principle be applied to the ink, paint and varnish industry as well. Today, water-based systems are used in numerous processes. Besides offer-ing the mentioned ecological advantages, they also frequently deliver better cleaning results than traditional methods.
Container cleaning in daily practice
The cleaning of containers represents the main cleaning application in the paint and varnish industry. In practice, this is a time-consuming process that uses large quantities of organic sol-vents. Most conventional cleaning systems with organic solvents use brush technology. The in-side surfaces of the container are permanently wetted with solvent while being cleaned by one or more brushes. (Since the entry into force of ATEX, brush cleaning systems must be inerted in order to be used with solvent.)
The effectiveness of this cleaning process is determined mainly by the mechanical effect of the brushes. A residual ink film is a common phenomenon. This incomplete cleaning is typi-cal for water-based inks, paints and varnishes.
A typical mixing container just before cleaning and just after a 15-minute brush cleaning with a solvent mixture.
The brush technology frequently causes a high solvent loss, and thereby increases the undesired VOC emissions.
Compared to these well-known drawbacks of cleaning with organic solvents, the water-based cleaning technology proves to be thorough and effective. Its combined mechanical and chemi-cal effect permits the use of spray jets with a pressure of 5-10 bar.
The effectiveness of this modern cleaning method is based on the combination of a physi-cal cleaning process and the chemical destruc-tion of the varnish polymer. In spite of shorter cleaning times and less mechanical cleaning, the cleaning effect is increased manifold.
In practice, the spray jet technology permits a thorough cleaning of container parts that are difficult to reach, such as outlets or grooves.
The result of a 10-minute spray jet cleaning with a water-based cleaning system: A clean container without ink film.
Moreover, water-based cleaning systems absorb much higher quantities of dissolved and undis-solved substances than conventional organic solvents. Consequently, they need far less wash-ing agent.
An important difference between water-based cleaning technology and cleaning with organic solvents is the cleaning process itself: In water-based cleaning, the washing agent must be heated to higher temperatures and the containers must be rinsed with water to remove residual washing agent.
The combined benefits of high effectiveness and high dirt absorption capacity make water-based cleaning very efficient. Despite the additional energy consumption and rinsing cycle, water-based cleaning systems are economically com-parable to cleaning methods with integrated solvent recovery.
Advantages of water-based cleaning systems
Economic and ecological sustainability
The water-based washing agents are free of VOC-emitting substances.
Greater freedom in the design of cleaning systems
Since water-based washing agents are not flammable, there is no need for sophisticated safety systems.
Universal applicability
The universal effectiveness of water-based cleaning systems, due to the combination of mechanical and chemical cleaning, makes this cleaning method suitable for all common ink and paint systems.
High effectiveness
Compared to organic solvents, water-based cleaning systems often show greater cleaning power, i.e. they require shorter washing times and less mechanical cleaning.
High dirt absorption capacity
Water-based washing agents have a longer ser-vice life and higher resistance than solvents.
Summary
The necessity of improving climate and immis-sion protection calls for greater restrictions on the use of substances and processes that cause emissions, particularly in industrial surface cleaning. One way of consistently meeting this requirement is switching to alternative, low emission processes and chemicals.
The water-based cleaning technology, consist-ing of a combined mechanical and chemical cleaning system and spray jet technology, is a highly efficient and economical process for re-moving ink, paint and varnish.