Lignosulfonate

Alternate Names: sulfonated lignin, sodium lignosulphonate, lignosulfate

Notes

A by-product from the production of wood pulp. Lignosulfonates are modified for use in ceramics, they act as a binder in plastic bodies. Lignins are used in brick and refractories production. Adding them to the clay (usually about 0.2% but can be much higher e.g. refractories) enables cutting the percentage of water (e.g. 2-4%) while still decreasing power usage in the pugmill. While the water concentration is lower, drying time is still increased somewhat (thus care needs to be taken to avoid uneven drying). Dry strength is generally improved. One user reported that while an iron oxide addition did not affect their body's plasticity it severely degraded dry strength - and a small lignin addition fixed the problem.

These products burn out at a fairly low temperature (e.g. 300-600*C).

These products are fairly expensive compared to traditional ceramic materials so only a cost-benefit analysis will prove whether then are feasible. One factor that really complicates their use is if the lignin product needs to be mixed with the water before the pugmill.

Care is needed before using this product in slurry operations as it can result in the formation of flakes on the inside the slip tank.

Related Information

Calcium lignosulfonate used as a glue to hold ball clay bags on a pallet

Some companies (e.g. Old Hickory Clay) use this as an alternative to shrink-wrapping every pallet of bagged materials (for environmental reasons for example). This wood derivative material is very sticky and behaves like a glue. However it redissolves quickly when whetted. Dark hard particles of this glue can be a concern in batching operations where they fall into the mix. However in a pugmill the particles dissolve during movement through the barrel and are not visible in the extruded product.

Links

Oxide	Analysis	Formula

Articles	Binders for Ceramic Bodies An overview of the major types of organic and inorganic binders used in various different ceramic industries.
Typecodes	Additives for Ceramic Bodies Materials that are added to bodies to impart physical working properties and usually burn away during firing. Binders enable bodies with very low or zero clay content to have plasticity and dry hardness, they can give powders flow properties during pressing and impart rheological properties to clay slurries. Among potters however, it is common for bodies to have zero additives.
URLs	http://en.wikipedia.org/wiki/Lignosulfonates Lignosulfonates on Wikipedia

By Tony Hansen
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