Pigment powder, the basic material for the majority of dispersed products feature a large number of primary particles which adhere to each other thus forming agglomerates, i.e. simple clusters. The decisive objective of a dispersion machine is to be seen in breaking up the agglomerates and in wetting, which means coating, each individual primary particle with the binder film.

The term "stationary" dissolvers is generally employed for "dispersion machines" with stationary impeller, mostly pole changeable, two-speed motors and a toothed disc not allowing any height adjustment. In our opinion, the use of this type of dissolvers does not provide satisfactory results. If required, the speed can be doubled, the power consumption, however, will then be 4 times as high. We believe that this ratio is too large, as most of the time the machine would then either be under- or overloaded. A matching to the product viscosity cannot be achieved.

Another important prerequisite is the height adjustment of the toothed disc. At the beginning of the production cycle, the disc turns just above the container bottom i order to start with the necessary reduced binder quantity. The low initial speed prevents the binder from splashing on the container wall. These splashes would, with the filling level rising, lead to fast and uncontrolled formation of pigment encapsulation which would then be excluded from the dispersion process. Because of the changing container filling level the infinite height adjustment of the toothed disc represents a crucial prerequisite, as only then a uniform product circulation and thus perfect dispersion is guaranteed.

According to our knowledge, the amount of electrical energy applied for optimum product composition, which is converted into friction heat during dissolver operation, is decisive for the degree of dispersion and the product fineness and modulus. For this reason, high rated drives feature a corresponding current consumption.
However, when calculating the energy requirement it is essential to take into consideration how the power is applied during the production process. Due to the short dispersion time and to the fact that the full drive power is virtually only needed for the dispersion phase itself, the power costs are relatively low. This means that a 110 kW dissolver requires less than 30 kW for a 2000 kg batch during a cycle time of only 15 min. At a basic price of EUR 0,13/kWh this results in approx. EUR 3,90 per 2000 kg of the product, i. e. less than half a Cent per kilogram. Not to mention the increased product quality.

During the operating process with dissolvers it must be assumed that the electrical energy will unavoidably lead to product heating due to particle friction, a side effect which is advantageous for the optimum dispersion process, because the flow behaviour of the product is positively influenced. Trials in the manufacture of white lacquer from titan dioxide pigments resulted in a considerably improved fineness modulus by approx. 5 µ at a temperature of 70° C, thus a better degree of whiteness and gloss as compared with a dispersion temperature of only 60° C.
Due to the improved particle wetting, in addition to pigment saving, not only the colour intensity development but also the storage stability is positively influenced. Experience has shown that the critical temperature upper limit of the majority of products is clearly higher than the factory reference values for dissolver application.

A very important prerequisite for the achievement of the dispersion task is a uniform product circulation up to the mixing container wall zones. To the best of our knowledge the design of stirring discs, tooth shapes etc. is not decisive. It is even possible that with completely smooth discs of a correspondingly large diameter an excellent dispersion result can be achieved. In practice, smooth discs have the disadvantage, however, that during pigment addition the contact with the mixed product is not always assured.

The increased quality requirements placed on today's products call for growing production equipment perfection. Even pastes and high viscosity products exceeding 500.000 cP which today are frequently produced in kneaders or planetary paddle mixers, can be produced more economically and with considerably better quality using our KREIS-DISSOLVER®s. Even for the production of high quality Polyester car body putty and glass fibre reinforced special qualities KREIS-DISSOLVER® with viscosity dependent speed control can be used due to its convincing success. Also here the improved dispersion has a positive influence on storage stability.

For the dispersion of colour pigments for offset printing inks substantial economical advantages are offered as a result of the use of the KREIS-DISSOLVER®. With a product composition featuring high pigment concentration (depending on the type of the prepared pigments, between 27% and 38%) a quality product can be achieved, when adhering to our formula proposals, with only one pass in the three roller mill.

Optimum dispersion results are achieved by the uniform, rolling product circulation. Apart from other constructive measures, container wall scrapers can be useful for the production of extremely thixotrope products and for mixing finished products and colours.