A method for coating color optimization with the emtec PDA.C 02 – developed by Gruener and Baumeister
- Characterization of the coating base paper surface
- Defined coating color preparation
- Simulation of the coating machine applicators at the time the coating color and the base paper are contacted :
- Simulating the shearing history of the coating color in the coater
- Dynamically contacting the coating color with the base paper
- Producing a high shear impulse and pressure pulse
- Characterization of the coated paper
- Instantaneous measurement within approx. 39 msec of contact
- Simple evaluation of the measuring results
WHAT ARE THE BENEFITS OF THE MEASURING METHOD?
- Differences in base papers, coating colors and coated papers lead to quality changes during processing ; unfortunately, the classical measuring methods do not adequately detect these variations. The PDA.C 02 system is able to identify these differences.
- Pilot coater and machine trials indicate the effects of coating color and base paper variations. The PDA.C 02 provides a tool to explore the origins.
THE PDA.C 02 CAN MEASURE ALL THREE STAGES OF THE COATING PROCESS :
1. Base paper
Assessing process relevant surface quality parameters
such as surface porosity, surface sizing and fines/filler concentration at the surface
R & D: Optimizing the base paper, developing new grades, ensuring quality consistency of several rolls in coating trials
QC: Detecting slight quality variations during production
2. Coating color in contact with base paper
Reducing the need for pilot coater / machine trials
R & D: Visualizing the interactions between the coating and substrate surface, gaining new insights, optimizing the additive and pigment use ( types and dosages )
QC: Controlling the incoming quality of additives and pigments
Assessing the changes in runnability, coating hold out, covering and print evenness in offset and flexo printing
3. Coated paper
Assessing the surface quality of coated papers :
Identifying small changes in the coating quality by comparing measurement results of liquid penetration with suitable test liquids ( water or mineral oil )
Determining and predicting the properties such as printability, glueability or barrier effects on the basis of a database or process analysis
MEASURING METHOD
- Modelling of the processes and the coating color to base paper interactions
- Characterizing the base paper by measuring with water, carboxyl methyl cellulose solution and serum
- Preparing and deaeration the coating color with a CDA / CDM laboratory system, taking the relaxation times after shear loads into account
- Measuring the coating color to substrate interactions with the PDA.C 02 in the short term time range, simulating the coating machine applicators
- Evaluating the measuring results with the aid of the ”Cookbook” for coating color optimization:
- Calculating the immobilization time IT
- Determining the curve gradient signs +/-
- Determining the gradient magnitude until FC
- Noting the curve shape after DWRV
- Information is provided concerning the homogeneity, structure, thickness, density of the immobilized filter cake, runnability of the coating color, print evenness, coating hold out and covering.
