Submills

Basket mill for batch grinding:

From 5 Ltr - 1750 Ltr Grinding Capacity

Theory or design concept
The SUBMILL complies with modern grinding technology.: Instead of one or two passes through the mill with reduced throughput, it is more effective to increase the number of passes with higher output. In fact, it is proven that the disadvantage of a continuous mill (vertical or horizontal) is that the residual time of the different pigment particles is not the same. Some particles stay longer in the grinding chamber whereas others will exit more quickly. The SUBMILL system on the other hand has a combination of expulsion and suction, ensuring that all the base product passes through the grinding chamber many hundreds of times during the operation and is progressively uniformly processed. Within the SUBMILL process system, there is a direct relationship between particles residual time and particle size distribution. At the end of the process, the finesse spectrum is very narrow and the colour strength is duly achieved.

The advantages of the SUBMILL

Coating products can be manufactured from start to finish using the same container. The premixing operation is reduced to a minimum.

The grinding process can be carried out entirely in automatic mode. No supervision is required.
If viscosity is increased during grinding, binder or solvent can be added to the mill base without stopping the process and transfering back to a mixer.

In comparison with the conventional Grinding Mills, the SUBMILL System is highly efficient, therefore, grinding times are greatly reduced. Compared to conventional Grinding Mills, the SUBMILL effectively decreases energy costs.

The Grinding Chamber is designed as an open system so that Grinding Media remains in a floating state. Therefore, flotation and compression are no longer a problem.

Replacement of worn media can be carried out in a matter of seconds without removing any parts.

Cleaning is very easy and quick. Following the Grinding operation, the basket is raised out of the process material, partially emptied by the slow running the disc and then finally submerged in the cleaning solvent. The SUBMILL is virtually self cleaning when its runs for a few minutes in a suitable solvent. In respect of colour changes, 10 to 15 minutes are enough to pass from one batch colour to another.

Grinding Media

Milling time is directly proportional to the diameter and density of Grinding Media. The number of contact points in a given volume depends on the diameter of the beads. Small media particles are important to obtain better grinds.

Grinding Media with high density is suitable for formulations of high pigment concentration. However, all kinds of Grinding Media such as glass, steatite, zirconium oxide and steel can be used.

Mechanical features

The SUBMILL has all the advantages of our world renowned mixer-dispersers with elevating rams and infinitely variable speed controls.

All parts coming into contact with the Grinding Media have smooth extremely hard surfaces, which result in minimum wear.

All parts coming into contact with the material being processed are of high micro finished stainless steel, to reduce cleaning down time.

A pressurised lid enables processing in a controlled atmosphere or vacuum.

The Grinding Chamber is fitted with a specialised jacket for the circulation of cooling water. This cooling system effectively dissipates heat during the grinding operation and efficiently decreases the temperature of the product during the grinding.

Alternatively the interchangeable dispersing/grinding vessel is fitted with a spiral flow water jacket for optimum temperature control. The coned bottom ensures optimum circulation of the product during grinding. Should the machine be required to run at less than maximum capacity the above design also facilitates operations with a smaller batches.

The motor is driven by a two speed motor or by a frequency inverter with infinitely variable speed.

Environment

Only the SUBMILL can work under vacuum. The vacuum can de-areate the material to be processed, decrease viscosity, modify thyxotropy, in other words improve rheological properties of the base product.

The SUBMILL works in a closed system as a sealed unit. There is no risk from loss of solvent and consequently prevents contamination of the environment.

The SUBMILL shows that the sole of the environmental problem is to avoid the need for removal of all emissions by not producing them in the first place.

The grinding basket (1) is immersed into the dispersion container (2) which contains the product to be ground. The product is pumped trough the grinding basket (1) at a very high flow rate by means of a turbine plate (3). The turbine plate creates a strong suction as well as a vigorous expulsion and ensures that the whole batch passes many time trough the grinding basket during the process. The grinding basket is filled with grinding beads (4), which are accelerated with an agitator disc (5). The moving beads stress the product to be ground. This stress causes a dispersion and / or break up of the solid matter in the product. The grinding basket is open above and equipped with a screen (6) at its bottom, which prevents the grinding beads from leaving the grinding basket. Most of the energy introduced by the agitator disc is converted to heat. This heat is carried off by means of a cooling liquid, which circulates in the cooling jacket of the grinding basket (8) and in the cooling jacket of the dispersion container (7). In order to prevent the formation of foam or the evaporation of solvent during the process, the SUBMILL's (except SUBMILL Labor) are equipped with a pressure sealed cover (9) which closes the dispersion container completely and allows to run the process under vacuum.