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How to disperse carbomer powder polymer
  • 2019-12-31 17:06:17

Although their application is not limited to aqueous systems, the Carbomer polymer such as Lubrizol Carbopol polymer such as Carbopol 940, 980, Carbopol ETD2020, Ultrez 21, Ultrez 20, and Newman fine chemicals brand name NM-Carbomer 940, 980, and other brand name such as carbomer 340, tego carbomer 140, owe much of their exceptional utility to their hydrophilic nature, or affinity for water.  A single particle of carbomer polymers will wet out very rapidly in water. Like many other powders, carbomer powder tends to form clumps when haphazardly dispersed in polar solvents.  When this happens, total mixing time is governed by the slow diffusion of solvent through this solvated layer to the dry interior.  Therefore, formation of lumps must be avoided to prevent excessively long mixing cycles so as to get smooth carbomer(carbopol)gel.



Dry Addition of Carbomer polymer

The simplest way to achieve complete dispersion of a Carbomer polymer such as Lubrizol Carbopol 940,980 Ultrez 20, 21, is to take advantage of its small particle size. Add the Carbomer polymer slowly and carefully to the dispersion medium while the mix is being stirred rapidly.  Any device that will sprinkle the Carbomer powder as discrete particles is useful. For example, something as simple as a coarse sieve containing a few large pebbles is very useful for making large batches.  The sieve permits rapid sprinkling and, at the same time, breaks up any loose polymer agglomerates so as to achieve smooth carbomer (carbopol )gel.



Agitation

Agitation enhances the rate of Carbomer polymer solvation.  In general, higher shear rates disperse Carbomer polymers most rapidly.  Extremely high-shear mixers should be carefully employed because they can break down carbomer carbopol structure, resulting in permanent viscosity loss.  In some cases, this loss can be as high as 50 percent.  Conventional impellers such as propellers or turbines do not impart excessively high shear rates.  They can be used to mix mucilage for extended periods with virtually no decrease in polymer efficiency. Moderate agitation equipment (800-1,200 rpm) is most commonly available. Here, the primary consideration is to incorporate Carbomer polymers slowly and carefully so that large, partially-wet agglomerates do not form.  In cases where the Mixer is employed, the use of two impellers on a common shaft is recommended.  The lower impeller should be about 1/4 liquid depth off the bottom, and the top impeller about 1/4 liquid depth below the surface.  Position the mixer in the tank so that a vortex of one to one and-one-half impeller diameters is generated.  The top impeller will disperse the Carbomer polymer rapidly before undesirable, half-hydrated, hard-to disperse lumps can form. Use of a variable drive motor is recommended. If the mixer cannot be repositioned to avoid vertexing, the vortex can be minimized by reducing mixer speed during the initial stages of neutralization.  As neutralization continues and the mix begins to thicken, a variable drive motor can be run at progressively higher speeds.



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