Modification of Starches in dry process
Chemically modified starches (from potatoes, corn, tapioca, wheat, peas, and others) are used in papermaking, among other applications, to improve paper strength. The wet process is used most frequently in this case. The starch is slurried in water, then the cationizing agent is added to cause it to react. The starch remains in a suspension throughout the entire process until drying. However the dry process is more economical. In this process, natural starch powder is intensively mixed with the cationizing agent. The etherification reaction then takes place in a reactor. The reactor is connected downstream to a second neutralizing mixer. The starch consistency remains powdery throughout the process.
The AVA HRM ring layer mixer and the continuous AVA HTK-T reactors are used in series production of cationized starches. In the first stage, the starch powder (native starch) is intensively and homogeneously mixed with the etherifying agent and sodium hydroxide (catalyst) in the ring layer mixer at circumferential agitator speeds of up to 40 m/s. Following this, etherification is carried out in an AVA HTK-T heated reactor. The reaction process is maintained continuously at processing times of between 1 h to 4 h. Finally the starch enhanced with sodium hydroxide solution is neutralized by adding acid. In this final process step a highly uniform mixing of the components is ensured by a further AVA HRM ring layer mixer.
- White dextrin
- Yellow dextrin
- British gum
Deciding Facts – Starches
- Reduced consumption of raw materials compared to the wet process
- Wastewater-free process
- Shorter processing times compared to the wet process
- Very high solids content
- Consistently reproducible product quality
- Batch process or continuous process – AVA offers both options
AVA ring layer mixers in combination with AVA reactors are ideally suited to the challenging tasks of the starch industry due to their high mixing intensity (optimal etherification).