Year 2009
Antti Mäntynen

Optimization of a bead mill colorant production process

Environmental demands and economical aspects cause a need for more energy- and eco-efficient ways to produce tinting pastes. The tinting pastes are concentrated pigment pastes which are used in different tinting applications such as decorative paints, industrial coatings and coated fabrics.

The aim of the master’s thesis is to optimize the efficiency of an industrial paste production process. An optimized process would reduce raw material and energy costs in the tinting paste production as well as increase the colour strength.

In the literature part of the thesis, colorant production, optical properties of pigments, dispersion process and dynamic models of grinding was studied. A literature review covering bead milling of colorants was done. Also one example of instrumentation and automation of bead milling process was introduced.

The objective of the experimental part was to optimize the colorant paste bead milling process with respect to colour strength, used specific energy and milling time by changing the milling variables. Screening of bead milling variables; bead charge, bead size, rotor speed, viscosity and feed rate, were done using Plackett & Burman experiment design.

Three of the most significant variables were further studied and the quadratic models were constructed using Box Behnken design and response surface methodology. The models were built for three different pigment pastes ((iron (III) oxide red, β-phthalocyanine blue and quinophthalone yellow). Finally optimization for tinting strength versus energy consumption per hour was made with help of these models. Also relation between tinting strength and grinding time per kg was studied.

It was discovered that for almost every pigment paste an increase of rotor speed decreased the products tinting strength and increased the milling power. Also a high tinting strength was achieved with lower specific energy when grinding time was fixed.

This info last modified 27 Apr 2024 by Jerri Kämpe-Hellenius