Rheological properties of gelatinized several pastes from Stein-Hall type corrugating starch adhesives at high temperature
2008
Koyakumaru, T.(Rengo Co. Ltd., Osaka (Japan))
This study investigated the rheological properties of Stein-Hall type corrugating adhesives (SH-adhesives) composed of carrier and main portions, which were needed for enhancing initial bond (green bond) strength to make the corrugated fiberboard at high speed on the double backer. Starch slurries and main portions of SH-adhesives were individually prepared from each starch: corn, high-almylose maize (hylon-5), waxy maize, wheat, potato, sweet-potato and tapioca. All carrier portions were prepared from cooked corn starch paste only. Initial shear rigidity, maximum shear stress, shear stress-strain pattern and viscosity of these gelatinized pastes from slurries and SH-adhesives were measured by the Couett type viscometer at 85degC. The properties of those SH-adhesives pastes depended on those of their main portions pastes, and were enhanced by their carrier portions. Rigidity and maximum stress of SH-adhesives pastes were varied by starch species, and these properties of the pastes from slurries increased as similar exponential function with increasing starch concentration in each species. So, these species pastes were organized into 4 types as type-1 of hylon-5, and type-2 of corn and wheat, and type-3 of potato, sweet potato and tapioca, and type-4 of waxy in order of the rigidity size and reverse order of strain size at maximum stress. And then, the rigidity was thought to be higher in the paste remaining the more clear shape gelatinized granules. Whereas, 7 kinds of SH-adhesive made a little difference in the green bond strength measured by table test. These results suggested that the rigidity and maximum stress were not most important factors in the rheological properties of gelatinized SH-adhesives pastes which were required to enhance the green bond strength on the corrugator.
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