Binder viscosity

Sodium carboxymethylcellulose is Hsted in the 1990 United States Pharmacopeia under the categories of pharmaceutic aid (suspending agent, tablet binder, viscosity-increasing agent), and cathartic tablets. 

Sfo is the Stokes number based on initial nuclei diameter do [Adetayo et al.. Powder Tech., 82, 37 (1995)]. Extent (/cf), depends logarithmically on binder viscosity and inversely on agitation velocity. Maximum granule size depends hnearly on these variables. Also, (/cf ), has been observed to depend hnearly on liquid loading y. Therefore, the maximum granule size depends exponentially on liquid loading. Fig. 20-73 illustrates this normahzation of extent (/cf), for the drum granulation of hmestone and fertilizers. 

FIG. 20-74 Effect of binder viscosity and liquid content on final granule porosity for the drum granulation of 15 im glass baUotini. Decreasing granule porosity corresponds to increasing extent of granule consolidation. [Iveson et al., Powder Tech., 88, 15 (1996). ] With land permission from Elsevier Science SA, Lausanne, Switzerland. 

Decrease Binder Viscosity Lower temperature since binder concentration will decrease due to drying thereby lowering viscosity. This effect generally offset due to inverse relationship between viscosity and temperature. 

Binder spray rate Droplet size is affected by liquid flow rate, binder viscosity, and atomizing air pressure and volume. The finer the droplet, the smaller the resulting average granules. 57, 74, 75, 95... 

The consistency (fluidity) of an initial mixture depends on the binder filler weight ratio, all other parameters (binder viscosity, microsphere type, shape, size, density, and mixing conditions) being equal. The mixtures are casting compositions (viscous fluids) at small microsphere concentrations, while they become molding compositions (pastes) at higher concentrations. Thus, the fluidity of a syntactic composition depends primarily on the filler concentration and not on the binder viscosity (Fig. 1)73 ... 

Fig. 5. Molding pressure (P) versus binder concentration (C) for BV-01 phenol microspheres and binder viscosities of 1.25 (1) and 10.8 (2) Pa s...

S. M. Iveson, J. D. Htster, B. J. Ennis, Fundamental studies of granule consolidation - part 1 Effects of binder content and binder viscosity, Powder Technol., 1996, 88,15-20. 

Decrease binder viscosity. Lower binder concentration. Change binder. Decrease any diluents and polymers which act as thickeners. Raise temperature for processes without simultaneous drying. Lower temperature for processes with simultaneous drying since binder concentration will decrease due to increased liquid loading. This effect generally offsets inverse relationship between viscosity and temperature. 

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