Ideal Starch Viscosity for Corrugated

Khuram asks,

I have a few queries regarding corrugated glue.

  • What should be the ideal viscosity and %age solids range for corrugated glue adhesive?
  • Which one is the standard cup to measure viscosity of corrugated glue?
  • As viscosity changes with temperature so can you provide any graph showing change in viscosity of corrugated glue with temperature?
  • As in summer season temperature is higher so viscosity will be less. Is it advisable to control viscosity by adding borax in summer season?

 

We reached out to Roman Skuratowicz at Ingredion for some expert insight to Khuram’s question. Here’s Roman’s response.

  • Ideal viscosity varies by machine, BHS typically likes 40-50s Stein Hall viscosity, others may like something between 30-40. Most machines overall will run between 30-60 seconds Stein Hall. Fresh adhesive is better than storage adhesive. Using adhesive within hours is preferred but if needed adhesive can be stored overnight or for days with proper formulation, agitation and temperature control.
  • The Stein Hall cup is the standard measure for starch viscosity, although there are European versions as well as the US version. I have only ever worked with the US version, which can be purchased from https://www.gardco.com/pages/viscosity/vi/steinhall_cup.cfm  or  http://www.ringwoodstarchmix.com/ among other places.
  • Correct, viscosity changes with temperature. Follow this link for a temperature/viscosity reference table “Temperature – Viscosity Correction Table (For Stein Hall Viscosity)”. This table is approximate but provides a good guide.
  • First adjustment for viscosity is typically to add or remove a few pounds of starch in the primary. Adjusting borax changes the chemistry of the adhesive and does not impact viscosity as effectively as primary starch. You can also adjust shear time in the primary or borax mix which will impact viscosity. That said, reducing water temperatures is important as you want to keep adhesive storage temperature below 105F, otherwise you will see viscosity growth in storage. Controlling temperatures on the corrugator is also important, as high paper temperatures will flash water from the adhesive and result in brittle, crystallized bonds.
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