Several attempts to control the size of tetra basic lead sulfate crystals have been investigated since a long time. All attempts based on spontaneous nucleation of tetra basic lead sulfate to obtain seeding crystals. Spontaneous nucleation, whether in the mixer before pasting or after pasting in a steaming process gives a wide distribution of tetra basic lead sulfate crystals after curing and drying. To control the size of the seeding crystal as well as the number per volume unit are the main problem of all approaches based on spontaneous nucleation. Additional agglomeration of seeding crystals restricts the minimum size of tetra basic lead sulfate crystal size to about > 15 µm and therefore effects remarkable the BET surface.
The engineering office developed together with Penox GmbH an additive containing tetra basic seeding crystals based on Nano Technology. The seeding crystals exhibit a narrow size distribution and are prevented against agglomeration. Therefore a homogenous distribution of seeding crystals will be obtained within the paste during the paste preparation. But applying steam a complete conversion to tetra basic lead sulfate will be obtained within less than one hour. The crystals size can be managed by the concentration of TBLS+ in the mixture. By adding 0.5% to 3% of TBLS+ crystals within the range of 3 µm to 20 µm will be achieved. Depending on the crystal size the pore sizes can be managed within the range from 0.4 µm up to 3 µm.