Porous Ceramic Roller Coating for Stable Ink-Water Emulsion
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Solution Overview
Problem
Existing roller bodies in wet offset machines, coated with matted chromium or RILSAN®, fail to maintain a stable ink-water-emulsion due to surface smoothing from highly pigmented inks, necessitating the use of costly and environmentally harmful emulsification aids, and often result in an 'ink-in-water-emulsion' that disrupts the printing process.
Innovation Solution
Application of a porous coating made from wear-resistant oxide ceramics or hard metals, such as Al2O3, Cr2O3, or WC/Co, using thermal spraying or other methods, which maintains surface roughness and prevents delamination in fibre reinforced plastic materials, ensuring a stable ink-water-emulsion formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If matted chromium or RILSAN® coatings are used on roller bodies, then wear resistance is improved, but surface roughness is lost due to smoothing from highly pigmented inks
Solution Approach 1:
The patent applies a porous coating layer made of oxide ceramics (such as Al2O3, Cr2O3, TiO2, SiO2, or ZrO2) or wear-resistant hard metals (such as WC/Co, Cr3C2/NiCr, NiCrBSi) on the roller body surface. The porous structure maintains surface roughness even after prolonged operation with highly pigmented inks, preventing the smoothing effect that occurs with conventional matted chromium or RILSAN® coatings. This porous structure allows the surface to retain its texture and emulsification capability while providing exceptional wear resistance.
Solution Approach 2:
The patent uses composite material structures where a porous coating layer of oxide ceramics or hard metals is applied over the base roller body material (steel, aluminum, or carbon fiber reinforced plastic). This composite approach combines the wear resistance of ceramics/metals with the porous surface structure needed for maintaining roughness, creating a multi-layer system that outperforms single-material coatings.
2Ease of manufacture
If conventional coatings are used, then manufacturing simplicity is maintained, but emulsion stability deteriorates requiring additional emulsification aids
Solution Approach 1:
The porous coating structure inherently provides the surface roughness needed for stable ink-water emulsion formation without requiring additional chemical emulsification aids. The porous surface topology creates natural emulsification zones that maintain stable 'water-in-ink' emulsion, eliminating the need for isopropyl alcohol or tenside-containing additives that would otherwise be required with smooth conventional coatings.
3Ease of operation
If smooth coatings are used, then initial emulsion formation is possible, but process stability deteriorates after extended operation
Solution Approach 1:
The porous coating maintains its surface roughness topology throughout extended operation, preventing the smoothing that occurs with conventional coatings after weeks of use. This sustained roughness ensures consistent emulsion stability and prevents the overturning of the printing process from 'water-in-ink' to 'ink-in-water' emulsion that occurs with smooth coatings during prolonged operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a wear-resistant surface that maintains sufficient roughness, preventing surface smoothing and ensuring a stable ink-water-emulsion, eliminating the need for harmful additives and maintaining print quality over extended operation.
Implementation Method 1
which coating preferably is applied by means of a thermal spraying method
Implementation Method 2
subsequently ground to size, so that pores in the matrix of the layer are opened
Data Source
Figure 1~2
AI summary
The invention relates to roller bodies made of steel, aluminium or carbon fibre reinforced plastic material, which, in printing units of wet offset machines, are in direct contact to the dampening form roller and which serve the formation of a stable ink-water-emulsion. The invention further relates to methods for producing such roller bodies. In conformity with the invention the roller body is provided with a porous coating of highly wear-resistant oxide ceramics or of wear-resistant hard metal, wherein pores that are open towards the circumferential surface of the roller body, are formed in the layer matrix of the coating preferably by applying the porous coating by a thermal spray process or an other coating process, and by subsequently grinding the coating to size to thereby open pores in the layer matrix. The surfaces produced in this manner preferably have a stable roughness of 1.0 μm < Rz < 500 μm, in particular Rz = 5 μm to 25 μm. The thicknesses of the porous coating preferably ranges from 25 μm to 2000 μm, and most preferably amounts to about 150 μm.