DisperCarbopol

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The Specialty Chemicals Innovator © TDS-103 Rev. October 1993 Dispersion Techniques for Carbopol® Resins Carbopol resins are highly water and polar solvent soluble polymers which function as efficient thickeners and stabilizers for suspensions or emulsions. Much of the exceptional utility of the Carbopol resins results from the hydrophilic nature of the polymer. A single particle of Carbopol resin will wet out very rapidly when put into water. Like many fine particulate powders, Carbopol resin
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  Carbopol resins are highly water and polar solventsoluble polymers which function as efficientthickeners and stabilizers for suspensions oremulsions. Much of the exceptional utility of theCarbopol resins results from the hydrophilic nature of the polymer. A single particle of Carbopol resin willwet out very rapidly when put into water. Like manyfine particulate powders, Carbopol resins tend toclump when improperly added to the solvent.The surface of a powder aggregate solvates to form atough outer layer which prevents complete wettingof the interior polymer particles. This results indispersion defects such as grainy texture, reducedviscosity or the presence of insoluble particlesresembling fish eyes.To prepare high quality and reproducible dispersionsof Carbopol resins, the proper dispersing techniquemust be carefully followed. I.Direct Addition of Carbopol Resinsinto Water The proper method to use when adding Carbopoldirectly to water depends on the quantity andconcentration of the dispersion to be prepared. A. Small Quantity Batch Dispersions Dispersions of several hundred milliliters to severalgallons with concentrations of up to 1.5 weightpercent Carbopol resin can be practically preparedby sifting the dry resin into rapidly agitating water.Aqueous surface wetting and dispersion of Carbopolresin is best achieved with moderate rate agitation of approximately 800-1200 rpm. Motorized mixers suchas the Eppenbach, Colframo, Arde-Barinco, Janke andKunkel or Lightnin' Mixer with a conventional open-blade impeller (pitched marine or saw tooth propeller)are most appropriate. Extremely high-shear mixerssuch as Waring blenders or rotor-stator homogenizersshould be avoided or carefully employed. The mixingintensity generated by this type of mixer can shear theopened (hydrated) polymers resulting in permanentviscosity loss. In some cases, this loss can be as highas 50%. Conventional impellers, such as propellersor turbines do not impart excessively high shearrates. They can be used to mix mucilages forextended periods with virtually no decrease inpolymer efficiency.If in-line mixers such as colloid mills or homogenizersare used, the Carbopol resin should be initially wetted-out with moderate rate agitation. Therefore, themixing time using the high shear mixers will beminimized. If a homogenizer is employed, strive touse the lowest shear rate and the shortest mixing timeto achieve a homogeneous mixture.When mixing, submerge the impeller until it is veryclose to the bottom of the vessel and angle the mixerto generate a vortex which is one to one-and-one half impeller diameters. Slowly sift the resin into thevortex of the agitating liquid (approximately 1200rpm). Continue the agitation for about 20 minutes oruntil a lump-free dispersion is attained. In some caseswhen a Lightnin' Mixer is employed, two impellers ona common shaft are recommended. The top impellerrapidly disperses the resin before the undesirable,partially-hydrated lumps are formed. A sifting devicesuch as a coarse sieve or a non-corrosive 20-meshmetallic screen should be used to slowly sprinkle theCarbopol resin into the vortex of the water generatedby the mixer. The sifting method allows the slow,controlled addition of the dry Carbopol resin, enablingeach particle to wet out on the water vortex. The sieve Dispersion Techniques for Carbopol Resins TDS-103Rev. October 1993 The Specialty Chemicals Innovator ©  or screen permits the break-up of any loose resin oragglomerates due to the static charge on the particles.A metallic screen decreases the tendency to buildmore static charge on the particles as they are sifted.Once all the dry resin has been introduced,continue agitating at the moderate to rapid rate for10-15 minutes. Reduce the speed to avoid theentrapment of excess air.For emulsions, add oils and emulsifiers to form theemulsion prior to neutralizing the Carbopol to buildemulsion viscosity. Neutralization of Carbopol isaccomplished with a suitable alkali or amine base.For the order of neutralizer addition in gel products,see the Carbopol Troubleshooting Guide. Note: Dispersions of Carbopol resins made toa precise solids level for analytical viscositytesting should follow Noveon Standard TestingProcedure 430-I, Brookfield Viscosity (lowshear). B. Large Quantity Batch Dispersions Dispersion volumes ranging from tens of gallons tohundreds of gallons at concentrations of Carbopolresins of up to three weight percent may be preparedwith an eductor or flocculant disperser. This techniqueis a fast, inexpensive means of dispersing Carbopolresins with reduced dusting.Figure 1 shows how the rate of dispersion increaseswith an increase in water pressure. Figure 2 shows thebasic design of the eductor. It is a small, inexpensive,metal or plastic, non-moving plumbing valve whichexerts a partial vacuum on the powder inlet via theBernoulli effect. Carbopol resin is pulled from theeductor funnel into the eductor valve throat. Thepartial vacuum is created by the flow of incomingmake-up water through the venturi of the eductorthroat. Water turbulence within the valve wets out theresin to enable the formation of quality dispersions.The eductor outlet should have enough piping (4-5 ft.)to build sufficient back pressure to direct the polymer/ water slurry into an agitated mix tank filled with waterto complete resin hydration.Eductors can disperse 22.7 kg (50 lb>) of resin in fiveto ten minutes with up to 3.0% resin concentration.Determining the exact eductor and size requiredfor the specific application can best be determinedfrom the technical bulletins and advice of aneductor manufacturer. Note: Select an eductor which is capable of a solidparticle dispersion. Do not use a liquid eductormodel. The funnel may be replaced bya flexible hose with stainless steel endtube to enable direct vacuum pick-upfrom the box of Carbopol resin. Selecting Neutralizers forHigh Alcohol Solutions ã Metallic alkali (NaOH, KOH, etc.) willneutralize Carbopol resins with less than20% ethanol. ã Triethanolamine (TEA) will neutralizeCarbopol resins up to 50% ethanol solution. ã 2-Hydroxypropyl ethylene diamine(Quadrol ® ) will neutralize Carbopol resins upto 70% ethanol solution. 1.   Cowles Blade—Not recommended due to high shear.2.   Paddle Blade—Frequently used when blending operations follow initialdispersion of Carbopol resin.3.   3-Blade Marine Impeller—Excellent choice for dispersing Carbopol resin.Impeller of choice when making emulsions.4.   Foddler Impeller—Poor mixing due to low shear.5.   Hi-Lift Impeller—High shear: use with caution. Noveon, Inc. / 9911 Brecksville Road, Cleveland, Ohio 44141-3247 / TEL: 800-379-5389 or 216-447-5000 tions and equipment used commercially in processingthese materials, no warranties or guarantees are made asto the suitability of the products for the applicationdisclosed. Full-scale testing and end product performanceare the responsibility of the user. Noveon, Inc. shall not beliable for and the customer assumes all risk and liability oany use or handling of any material beyond Noveon’s directcontrol. The SELLER MAKES NO WARRANTIES,EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITEDTO, THE IMPLIED WARRANTIES OF MERCHANTABILITYAND FITNESS FOR A PARTICULAR PURPOSE. Nothingcontained herein is to be considered as permission,recommendation, nor as an inducement to practice anypatented invention without permission of the patent owner.The information contained herein is believed to be reliable,but no representations, guarantees or warranties of anykind are made as to its accuracy, suitability for particularapplications or the results to be obtained therefrom. Theinformation is based on laboratory work with small-scaleequipment and does not necessarily indicate end productperformance. Because of the variations in methods, condi- The Specialty Chemicals Innovator © ® Trademark of Noveon, Inc.© Copyright 2001 Noveon, Inc.  Figure 1Dispersion Rate of Carbopol Resins with an Eductor Figure 2Eductor  Further information regarding eductors can beobtained from these manufacturers:PENBERTHYP.O. Box 112Prophetstown, IL 61277Phone: (815) 537-2311FAX: (815) 537-5764AMETECK INCORPORATEDDivision of Schutte and Koerting2233 State RoadBensalem, PA 19020Phone: (215) 639-0900FAX: (215) 639-1597FOX VALVE DEVELOPMENTCORPORATIONHamilton Business Park, Unit 6AFranklin RoadDover, NJ 07801Phone: (201) 328-1011FAX: (201) 328-3651DICKENS & WILLIAMSONINCORPORATEDP.O. Box 25009Charlotte, NC 28212Phone: (704) 537-0304FAX: (704) 245-1977 C.Large Quantity Continuous ProductionDispersions The production of good quality, high-solidsCarbopol resin dispersions from a continuousproduction scheme is possible with a mechanicalin-line powder disperser. Mechanical dispersers usethe principle of a high velocity eductor coupled withthe mechanical working configuration of an in-linehomogenizer to rapidly disperse and wet eachindividual polymer particle instantaneously. Thishighly turbulent, high-shear mixer operates at sucha rapid rate that the particles are wetted and expelledprior to polymer swelling. Lump formation andpolymer degradation from mechanical shearingare eliminated.The valved powder hopper feed of the mechanicaldisperser can significantly reduce the level of airentrapment or foaming. Dispersed particles areexpelled from the disperser directly in a tank with low/moderate agitation. Table 1 providescomparative outline of mechanical dispersersand their features.  Further information regarding mechanical disperserscan be obtained from the following manufacturersor distributors.YTRON ® Dr. Karg GmbHOsternacherstrasse 50D-8210 Prien am ChiemseeGermanyPhone: 08051/1457QUADRO™ PROCESS INC.72 King Street SouthSt. Jacobs, ONCanada NOB 2N0Phone: (519) 664-3724SILVERSON MACHINES LTD.Waterside Chesham, BucksHP5 1 PQ, EnglandUnited KingdomPhone: 0494786331NORTH AMERICANSILVERSON MACHINES LTD.P.O. Box 58950 Industrial DriveEast Longmeadow, MA 01028Phone: (413) 525-4825ARDE BARINCO INC.500 Walnut StreetNorwood, NJ 07648Phone: (201) 784-9880 D. Carbopol Resins and Foam Some foaming can occur in the preparation of Carbopol resin in water dispersions, particularly withCarbopol 1342 and 1382. The significant yield valueof these dispersions (even as unneutralized polymers)can result in the formation of a persistent foam.A handy technique to break the foam is to partiallycollapse the polymer by the addition of a very lowlevel of strong mineral acid. The yield value isreduced and the trapped air surfaces. Phosphoricor hydrochloric acid is effective at O.5% on theweight of Carbopol resin. A 1.0 weight percentdispersion of Carbopol resin would require 0.005weight percent or 50 ppm H 3 PO 4 or HC1. This levelof acid results in no significant contribution of saltwhen neutralizing Carbopol resin. Therefore, theviscosity of the end product is unaffected. Organicacids suchas citric or lactic acid are not recommended becausethey are weaker acids and would yield higherconcentrations of residual salts upon neutralization. Table 1Mechanical Dispersers for Carbopol Resins ModelManufacturer/Distributor CarbopolResinCapacity(lbs./hr.)MaximumCarbopolResinSolids(wt. %)Water Flow Rate(lbs./hr.) ZCYTRONQUADRO120015*15,000SilversonFlashblendSilversonMachines Ltd.,UK750015-20*50,000Arde VaccuumDilumeltArde Barinco Inc.1000430,000* Dispersions of greater than 5 weight percent Carbopol resin becomedense, solid-like, and impractical to pump or handle. Tips for Using an Eductor ã   Avoid using hot water. The water vaporwill prematurely swell the resin end clogthe eductor. ã   A minimum 3/4-inch (2 cm) diameter pipeend 35 psig (1.2 atm) water pressure isrequired for an eductor. Constant pressuremust be maintained. If necessary, include apump for inlet water. ã   The eductor should be installed with easilyremovable plumbing fittings to facilitatecleaning. The discharge must be locatedabove the liquid level of the tank to preventback pressure. ã   Prevent plugging of the eductor throat bystarting with a clean eductor and initiatingthe water flow before adding the preweighedresin to the eductor funnel. If the eductor doesplug with dry resin, care should be takenwhen cleaning so that the eductor orifice sizeis not altered. ã   Tapping the funnel manually or with aninexpensive vibrator will prevent Carbopolresin from sticking to the funnel.
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