Water-based cleaning system for anilox rollers

This article describes a cleaning system (enpurex from bubbles & beyond) for anilox rollers and gravure cylinders tested under laboratory and field conditions by the Leipzig University of Applied Science at the recently established HTWK’s faculty iP³ Leipzig (Institute of Printing, Processing and Packaging, Leipzig/D).

This article was written by Prof Dr Lutz Engisch and Dr Dirk Schumann

Unlike traditional solvents, the enpurex cleaners act on the basis of novel systems called complex phase fluids. They belong to the inner structured fluids that act dynamically due to a high self-forming fluid. The product penetrates the cells deeply to clean, diffuses into the dried ink and lifts its fragments from the surface of the roller (see figure 1). Typical dissolving action of the ink does not happen. As a result, the negative aspects of conventional solvents, such as smearing or large solvent volumes are obsolete.

 

The enpurex cleaning innovation is a physical cleaning principle which works in three steps: 1 = Infiltration and diffusion into the ink layer, 2 = Fragmentation of ink and 3 = Removal after a water rinse.
Figure 1: The enpurex cleaning innovation is a physical cleaning principle which works in three steps: 1 = Infiltration and diffusion into the ink layer, 2 = Fragmentation of ink and 3 = Removal after a water rinse.

The enpurex detergents are water-based, non-flammable, free from caustic chemicals and biodegradable. Products from the enpurex series can only be applied in an undiluted form and are deactivated by adding water.

Current roller and cylinder cleaning

Due to its chemical composition, dried ink can not simply be removed from the cells with soap and water; it must be removed with special cleansers. Products that are currently used for cleaning printing formes in gravure and anilox rollers in flexo printing are mainly based on organic solvents. Solvents can access the human body through inhalation or by skin contact. Regular exposure to these substances can be harmful.

This may cause degreasing of the skin, irritation of the mucous membranes, narcotic effects, disorders of the central and peripheral nervous system, or liver and kidney damage. Furthermore, most solvents are highly polluting and are also fire and explosion hazards.

Solvent-based products are restricted under rigid industrial safety standards, and classed as chemical and hazardous pollutants. To these chemical and hazardous pollutants belong all substances which endanger human health or at least affect it, regardless of their aggregate state. The hazardous chemical substances access the human body mainly through the respiratory tract and through the skin and enter the bloodstream very quickly and often unnoticed.

Respiratory diseases, nerve damage, as well as cancer are a later result of prolonged pollutant distribution throughout the body. The exposure dependence is based on the biological half-life of the substances-an indication for the time until half of the substance is removed or converted into other products. In order to provide broad protection for the environment and the user, several chemical laws have been published which describe and restrict the handling of hazardous chemicals and which list the values of each substance with a maximum accepted concentration (MAC).

Since 2004, risk-based Occupational Exposure Limits (OEL) have been introduced. The usage of those substances is only allowed if the necessary protective measures, which are defined in the »Hazardous Substances Ordinance«, have been carried out. The adherence to these necessary precautions can only be achieved with considerable effort and the resulting costs such as aspirators, special chemical storage cabinets, residual solvent disposal costs etc.

Novel cleaning processes

The expertise of bubbles & beyond lies in research and development in the field of complex fluids. They are the first company worldwide to develop so-called phase fluids. The ingredients – mostly cosmetic raw materials – reform these fluids into highly dynamic superstructures. Among the ingredients are components which are usually not miscible, such as oil and water. By adding surfactants and specific activators the components solute into each other permanently and form a stable single-phase fluid. This fluid is the structured equilibrium between the permanent separation (Ostwald ripening) and mixing (entropy effect).

The ingredients are not (or only a little) involved in the proper cleaning action but instead build a molecular network. Unlike ordinary liquids, here molecules work in conjunction (molecular team-working) with each other and not individually. The high dynamics in the fluid along with the high diffusivity ensure a smooth and physically created cleaning process on many surfaces: paints or residues do not need to be etched away aggressively, instead they are fragmented by using the intelligent fluids and lifted off the surface. The performance surpasses most conventional systems significantly.

Another advantage of intelligent fluids is the use of gentle ingredients instead of »hard chemistry«. bubbles & beyond’s technology is particularly based on renewable raw materials, cosmetic or food grade ingredients. The enpurex products are all water-based, dermatologically tested and biodegradable and thus contribute towards environmentally compatible process controls.

Test study

One of the first applications was the removal of graffiti from mineral, plastic, or metal surfaces. The targeted development of the technology in the printing industry began rather by accident: An interested label printer heard about the innovative graffiti remover, and decided to test the cleaning effect on anilox rollers and in particular on the hard chemical components of conventional products.

The inefficient cleaning performance of competitor’s products and the use of expensive technical equipment led the industry expert to look for gentle and highly effective alternatives. After the first positive results the targeted optimisation of formulations for the priority use in flexographic and gravure printing started with the development of enpurex products.

Together with the Leipzig University of Applied Science (HTWK Leipzig) the first laboratory and field tests were conducted as part of a technical study. The enpurex 95 Plus and enpurex Power cleaning systems were tested rigourously by the HTWK department »Materials and Material Testing« for their cleansing effect.

The intensity of the product’s smell was assessed in advance by an odour test (known as olfactory tests). The bubbles & beyond products, enpurex 95 Plus and enpurex Power, were compared to the standard cleaning agents butyl acetate, isopropyl alcohol, and a mixture of ethanol/ethyl acetate. The test volunteers ranked the intensity of odours into an arbitrary order. These tests showed that the enpurex cleaners were rated better compared to the standard cleaning agents. The odours were perceived as less aggressive and less unpleasant.

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