7/21/2019 TDS-61 How to Prepare Aqueous Dispersions of Carbopol

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TECHNICAL DATA SHEET

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TDS-61Edition : October 15, 2007

Previous Edition: January, 2002

How to Prepare Aqueous Dispersions ofCarbopol

Polymers

Dispersion

Although their application is not limited to aqueoussystems, the Carbopol polymers owe much of theirexceptional utility to their hydrophilic nature, or affinityfor water. A single particle of Carbopol will wet out

very rapidly when put in water. Like many otherpowders, Carbopol polymers tend to form clumps ofparticles when haphazardly dispersed in polarsolvents. The surfaces of these clumps solvate,forming a layer which prevents rapid wetting of theclump interiors. When this happens, total mixing timeis governed by the slow diffusion of solvent throughthis solvated layer to the dry interior. Therefore,formation of lumps must be avoided to preventexcessively long mixing cycles.

Dry Addition of Carbopol Polymers

The simplest way to achieve complete dispersion of a

Carbopol polymer is to take advantage of its smallparticle size. This advantage is lost if the Carbopol isadded too fast. Add the Carbopol slowly and carefullyto the dispersion medium while the mix is being stirredrapidly. Any device that will sprinkle the Carbopolpowder as discrete particles is useful. For example,something as simple as a coarse sieve containing afew large pebbles is very useful for making largebatches. The sieve permits rapid sprinkling and, atthe same time, breaks up any loose polymeragglomerates.

See Technical Data Sheet 103 for information on use

of the other production scale dispersion techniques forintroducing Carbopolpolymers into water.

Agitation

Agitation enhances the rate of Carbopol solvationIn general, higher shear rates disperse Carbopopolymers most rapidly. Extremely high-shearmixers should be carefully employed because they

can break down the polymers, resulting inpermanent viscosity loss. In some cases, this losscan be as high as 50 percent. Conventionaimpellers such as propellers or turbines do notimpart excessively high shear rates. They can beused to mix mucilages for extended periods withvirtually no decrease in polymer efficiency.

Moderate agitation equipment (800-1,200 rpm) ismost commonly available. Here, the primaryconsideration is to incorporate Carbopol polymersslowly and carefully so that large, partially-wetagglomerates do not form. Mixers such as the

Eppenbach, Barrington or Lightnin' Mixer are welsuited for the preparation of Carbopol mucilages.

In cases where the Lightnin' Mixer is employed, theuse of two impellers on a common shaft isrecommended. The lower impeller should be abou1/4 liquid depth off the bottom, and the top impellerabout 1/4 liquid depth below the surface. Positionthe mixer in the tank so that a vortex of one to one-and-one-half impeller diameters is generated. Thetop impeller will disperse the Carbopol polymerapidly before undesirable, half-hydrated, hard-to-disperse lumps can form.

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TDS-61How To Prepare Aqueous Dispersions of CarbopolPolymers

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Use of a variable drive motor is recommended. Ifthe mixer cannot be repositioned to avoid vortexing,the vortex can be minimized by reducing mixer

speed during the initial stages of neutralization. Asneutralization continues and the mix begins tothicken, a variable drive motor can be run atprogressively higher speeds. The increasingviscosity decreases the tendency to vortexformation.

Dispersions in Non-Solvents:The Indirect Addit ion Method

The recommended method of incorporatingCarbopol polymers is to premix them in a non-solvent. Carbopol polymers can be easilydispersed, for instance, in the oil phase of

emulsions. Many oils and solvents may be usedsuccessfully to make readily-pourable 30 percentdispersions of Carbopol polymers. When suchnon-solvent dispersions are added to the aqueousphase, which must contain the necessaryneutralizing agent, normal thickening occurs.

When dispersing Carbopol polymer in the oil phase,mix until a smooth, homogenous dispersion isreached.

Using moderate to vigorous agitation (800-1,200rpm), add the oil phase containing Carbopol

polymer to the water phase. The water phaseshould contain an appropriate neutralizing base.

Continue to mix for 15-20 minutes until theCarbopol polymer has swelled to produce a smoothemulsion.

The Direct Addition Method

In the presence of some polar oils (aromatic ordicarboxylic acid esters) or molten oils above 60C

Carbopol will physically plasticize, hindering stableemulsion formation. In these cases, dispersingCarbopol polymer directly into the water will resultin a smooth, stable emulsion.

Begin by mixing the water with moderate agitation(800-1200 rpm). Very slowly sift the Carbopopolymer into the vortex. Before adding the dryCarbopol polymers to the tank, break up any lumpsthat have formed in the polymer due to staticelectricity or humid conditions. Continue agitationuntil a thin, cloudy solution without lumps isattained.

Continue agitation while pouring in the oil phaseMix until particle size is reduced and a glossyproduct is obtained. Neutralize with a suitablebase.