’ Advan

Conts in TiO~

ast year we published an article in thismagazine on using polymeric hiding lcch-nologies as a means of reducing dependenceon Ti02 in paint formulations.1ROPAQUETM

, opaque polymer and EVOQUETM prc-com-posite polymer were shown as effective means to partiallyreplace TiO2, reduce formulation cost, and maintain orimprove performance properties in architectural coat-ings. ROPAQUE, a light-scattering pigment, has been araw material in pabats for the last 30 years and its use hassteadily grown as the technology has advanced throughseveral generations of development. The recent pricesurge in TiO2 and high forecast price through 2015 (Fig-ure 1) have sparked a renewed interest, and formulatorsare revisiting its use in a wider range of formulations aswell as increasing its use in current opaque polymer-con-taining formulatinns. Last year, EVOQUE pre-compositepolymer was a newly introduced technology for TiO2reduction, which increased both the wet and dry lighi-scattering efficiency of Ti02. In this article we focus onthe advances made in the past year with this exciting newtechnology h’om its initial launch in early 2011 to its fullcommercialization in 2012,

FIGURE1 [ North America historical average and forecast price of TiO2through 2015.

$3.00

$2.00

$1.00

History (IClSPricing, ReedBusinessInformation Ltd.)

MineralsInternational)

$0,00 ~,~1~1~~’~

1990 1995 2000 2005 2010 2015

Reference

TiO2 Crowding and Loss of ScatteringEfficiencyBelbre we talk about pre-composite polymer, let’s discussone of the fundamen tel problems in using TiOa in white andpastel formulations - crowding.? Crowding occurs whenthe spacing of TiO2 particles decreases to the point wherethe light scattering becomes dependent on the concentra-tion of’fiOz. Crowding reduces the scattering efficiency ofTiO2, causing formulators to use lnore of this expensiveraw material. In practice, this effect begins well below10 PVC of TiOa, leading to inefficient use of TiO2 in mostarchitectural coatings. To date, there was little that couldbe done to overcome the crowding effect. Using sufficientlylow levels of TiOa is not an option in white and pastel paints,Small-particle-size extenders and binders can reduce, butnot elilninate, crowding. So forlnulators are forced to usehigher levels of Tit)~ cud incur the associated higher rawmaterial cost. With the rising cost of TiOa over the past 18months, the inefficient use of TiO~ is no longer sustainablein the coatings industry, EVOQUE pre-composite polymerprovides a new and practical solution to this old problemby offering a more uniform distribution of TiOa in the paintfilm, resulting in improved scattering efficiency.

How EVOQUE WorksOne way of describing the crowding effect is by dependantscattering.~ ~is theory describes the effective scatteringdiameter, or scattering zones, of TiO2 particles as beinggreater than their actual diameter. These scattering zonesoverlap as the concentration of TiO2 increases, reducingscattering efficiency, and resulting in the crowding effect,The EVOQUE polymer strongly interacts with the TiO2 sur-lhce to forth a pigment-polymer composite. This compositemaintains a greater separation between the TiO2 particles,resulting in a more unfform distribution of TiO2, which inturn reduces the overlap of the scattering zones, thus result-ing in greater scattering efficiency, as shown in Figure 2.

Factors Affecting Ti02 CrowdingLet’s look more closely at TiOa crowding and the factorsthat can affect it. As the use level of conventional TiO2

By David Fasano, Ph.D., Senior Scientist; and Linda Adamson, Architectural Technical SerMce Manager I The DowChemical Company, Spring House, PA

Technicians and scientists nccd data to verify tcst outcomesand validate their research, As the need for additional testingincreases, more data will be generated. Therelbre, the data infor-mation system becomes increasingly important, Data createdIYom testing or other process steps needs to bc integrated into the

Automation Solution for RheologyBeing a global market leader in the fields of density and theologymeasurements. Anion Paar has seen the increased need far labautomation and the benefits it brings. Together with key customers,we have iraplemented automated rhealogical measurement solu-tions, The HTR (High’throughput Rheomcter) is a customized solu-tion that fits company individual processes. For an HTI1 proicct, theexisting procedures arc analyzed and adequate automation solu-tions provided. A cooperative approach and the customized solutionto an existing need are key factors for successful automation.

The HTR automates the process of sample preparation, mea-surenrent, measurement device cleaning and measurement datastorage. The first step in such a prolect with the HTI/is to analyzethe theological measurement processes. Typically, this showsthat there are more routine processes than customers often thinkof. Rheological measurements on a small number of samples cantake more than half a day, leaving less tbne for analysis and inter-pretation of the data. Subsequently, there is a lack of motivation forincreased testing due to the large amount of work involved,

Existing HTR customers say that they can build more complexanalysis due to the high throughput offercd by the HTR solution.

A further nmior advantage is that measurements will be analyzedduring the night or weekend. Management consulting companiesthese days send their draft to india overnight and get a well-prepared analysis the next day. In the case of rheological mea-surement, an automated solution is capable of doing the stone.Customers have the data needed in their data rile the next day andcan start right away with important research.

Successful automation can increase throughput, help driveinnovation faster and reduce cost. Once installed, fast return oninvestment and other benefits can bc easily achieved. A key factorin the successful implementatfan of automated solutions is thechoice of the partner or automation company. The combination ofapplication knowledge with automation knowledge is an essentialstep towards successful automation.

An Important Factor inTechnological LeadershipAccording to Markus Bodlos, Head of Antomalion & Robotics,"Demand has increased since the recession because companiesare willing to invest to set themselves apart from the intensecompetition within the coatings industry." In the comingyears, many cmnpanics worldwide will invest in various auto-motion solniions, The decision for automation will not just bemade for cost savings and increase in efficiency, but also tohave the capability of additional testing, one important factorin technological leadership. ¯

For more information, visit www.antonpaarxom.

5.06

De~eisko Corporation ¯ Ogdensbu~g, New Yoi~k ~

PAINT & COATINGS INDUSTRY ¯ !~ 27

increases in a paint formulation, the amount of incremen-tal scattering decreases, and tbus scattering efficiencydecreases, as indicated by the dashed blue line in Figure3. As the concentration of TiO2 increases, the separationbetween the particles decreases dramatically, as schemabically shown in Figures 4a and 4b. Many formulators usesmall-particle-size extenders in an attempt to decreasecrowding. In fact, small-parficle-size extenders still crowdTiO2 but to a lesser degree than large-particle-size extend-ers, as schematically shown in Figures 4c and 4d. q’heeffect this has on scattering is shown in Figure 5, Thehorizontal reference line indicates the scattering of thecontrol formulation with 190 pounds of TiOx,

Eleven extenders of different composition and particlesi~e were used to formulate at 15 PVC while maintain-ing TiOx level and volmne solids. The control formulationand one extender formulation are given in Table 1. It isclear that the largest extenders had the most negativeeffect on scattering, As much as 20% of the scatteringefficiency was lost with the 12 Itm calcium carbonateextender, More surprisingly, even the smallest sub-micronextenders do not increase the scattering above that of thecontrol formulatiom indicating some degree of crowding.While small-par ticle-si~e extenders crowd less than large-partide-si~e extenders, they do not space TiOx and theydo not increase its scattering efficiency. By comparison,ROPAQUE should minbnally crowd ~ri02 as a similar sizedextender, but we observe an increase in the overall scat-tering of the paint. The increase in scattering is the resultof the encapsulated air void, which acts as a light-scatter-ing pigtnent. The comhination of scatterit~g and minimalcrowding has led to the common use of this raw materialin paint forlnulations and, with today’s rising TiOx price,it is producing new value in a wider range of formulationsat increased use levels.

Like extenders, latexbinders are also particles. As such,they can crowd TiOx and reduce its scattering efficiency,as shown in Figure 6. Several commercial latex binderswere substituted into an extender-containing forcnulationsimilar to that shown in Table 1: the extender PVC wasadjusted to 6 PVC. Scattering decreases with increasingparticle si~e with two exceptions, In the case of the styreneacrylic latex binder, scattering is less than anticipatedbased on its particle size because the refi’active index ofthe styrene acrylic latex is greater than that of the otherlatex binders. Scattering is proportional to the differencein refractive index squared between the pigment and thesurrounding medium. So increases in the latex refractiveindex decrease that difference relative to the high refi’ac-ti~e index of TiO2 (~2,8). The uniquely high refractiveindex orTiO~ is what makes it such a good hiding pigment,The second exception is EVOQUE pre-composite polymer.It has much higher scattering than at~ticipated for bothits particle size and refractive index, The improvement inscatterit~g is due to a more uniform distribution of TiO2 inthe paint film. The effect on scattering over a broad rangeof TiO2 levels is shown by the solid red line in Figure 3.

Scalming dectron micrographs of paints made withconventional latex binders and EVOQUF~ are shown inFigures 7a and 7b, respectively. The more uniform dis-tribution of TiO2 is seet~ in Figure 7b. Another l?ature of

FI(]URE 2 I Scattering zone depictions for Ti02 and EVOQUE. Scattel-ing efficiency of Ti02 decreases at high use Levels because of crowding.EVOQUE limits how close Ti02 particles can approach each other.

TiO2 particle with itsscattering zone

EVOQUE precomposite polymer

FISURE ] Scattering efficiency of conventional TiO~ compared to com-posite Ti02,

} l ~ Conventional TiOz

I ~10 20

TiOz PVC

FISURE4 ! Schematic depiction of TiO2 particle distribution and separaLion at a) low use level, b) high use level, c) high use level with large partide size extender, and d) high use level with small particle-size extender,

PAINT & COATINGS INDUSTRY

Advancements in Ti02 Composite Technology

FIGURE 5 ~ Effect of various particle sizes on light scattering comparedto the control (no extender). ROPAQUE opaque polymer offers a furtheradvantage as a light-scattering pigment.

0.1 1.0 10.0

~ No Extender (190 Ib TiO~)

ROPAQUE OpaquePolymer 15 PVC

¯ CaCO,, 15 PVC

Particle Size (um)

FIGRRE 6 I Scattering efficiency compared to particle size for variouslatex binders.

= 6

50,1 Particle Size (u m)

~* Acrylic ~1.50

A VA/Eth-1.50

[3 Styrenic ~1.55

¯ EVOQUE Pre-Composite

T/IBLE1 I Formulations with and without extender.

Grind

TAMOU" 731A dispersantSurfactantDefoamerDry universal Ti02ClayGrind subtotalLetdownWaterRHOPLEXTM acrylic

binder (50%)CoalescentPropylene glycol5urfactantDefoamerWaterAmmonia (28%)ACRYSOLTM RM-2020 NPR

rheology modifierACRYSOL RM-8W theology

modifierWaterTotals

125.06.81.01.0

190.00,0

323.8

50.0

531.3

5.310.01.01.02.50.0

25.0

88.7

408.8

50,0

436.7

4.410.0

0.0

25.0

5.5 5.2

48.4 128.7

the micrographs is the brightness of the TiO2 particles inFigure 7a, indicating that the TiO2 particles are at the verysurface of the fihn, while in Figure 7b the TiO2 particlesare less defined, indicating that they are covered withpolymer, the pre-colnposite polymer that is forming thepigment-polymer composite. The more uniform distribu-tion of TiO2 particles and the fact they are below the filmsurface infers that a tighter film structure is possible.

Scattering and Color/Tint StrengthWhen reformulating for reduced Ti02 levels, matching thescattering properties is important to ensure that the opacityremains the same. Just as important is lnatching the tintstrength properties. Most refornmlations need to be accom-plished while maintaining the same color palette as theoriginal paint. With both polymeric hiding technologies,ff the scattering of reformulated paint matches that of theoriginal paint and there are no color acceptance issues, thecolor palette can be well matched. Examples of relbrmula-tions using ROPAQUE and EVOQUE tinted with 2 ounces orthe COLORTREND 888 line without any adjustments to theformulations are shown hr Figure 8, The formulations aregiveu in Tables 2 and 3. EVOQUE pre-composite polymerrelbrmula~ions have a AE (CIELab color space) less than1. The AE for all of the ROPAQUE opaque polymer cam-parisons are less than or equal to 2, the greater AE comingmainly From the yellowness (+Ab) of the flatting extenderused in this reformulation. Excellent color matching andtint strength are possible with both polymeric hiding tech-nologies, even with significant TiO2 reductions.

TAB!.E 2 I Control and E~OPAQUE formulations used in thecolor examples in Figure 8.

GrindCellulosic thickener (2.5%)WaterTAMOL 165A dispersantKTPPTRITONTM CF-IO surfactantDe foamerDry universal Ti02Nepheline syeniteAttapulgiteDiatomacous silicaMildewcideGrind subtotalLetdownRHOPLEX acrylic binder (45,5%)ROPAQUE Ultra (30%)De foamerCoalescentACRYSOL RM-2020 NPR

theology modlfierWaterTotals

100,0

16.2

2,0

224.2224.2

5.0

5.0684,2

368.4

3.68.4

15.4

86.6

100.0105.011.61.12,01.0

155.4129.75.029.75.8

546,3

368.6

78.2

3.6

9.6

53.9

1075.7

Full Commercial StatusWhen we first launched the EVOQUE pre-composite poly-mer technology platform in early 2011, we were complet-ing the final stages of product development and manu-facturing scale-up, Commcrcial production began in theIattcr part of 2Bll. We now have three commercial prod-ucts designed for the needs of the North American market(Table 4). Co]nmercial paints containing EVOQUE arcbeing soId in North America. In other parts of the world,paints made with EVOQUE designcd for their specificneeds are enjoying similar commercial success.

Formulating ProtocolWhen formulating architectural house p~ints withEVOQUE, we have deveIoped a protocol that is highlightedin Table 5. In the high-quality fiat formulation in Table6, we started with an existing conventional control paintthat already contained I~.OPAQUE. Pocusing on the mainingredients that contribute to the overall PVC of thepaint, we removed 15% of the TiO2 and replaced it withROPAQUE to keep tfie PVC constant. You could chooseto use more economical extenders or a combhaatio~ ofROPAQUE and extenders to maintain PVC in the corn-

TABLE 31 Control and EVOQUE formulations used in thecolor examples in Figure 8.

GrindEVOQUE pre-composite

polymerOefoamerWaterSlurry TiOaGrind subtotalGrindWaterCellulosic thickener (100%)TAMOL 1124 dispersantSurfactantDefoamerClayNepheline syeniteAttapulgiteGrind subtotalLetdownSlurry TiO2RHOPLEX acrylic binder (53.5%)ROPAQUE opaque polymerCoalescentDefoamerPropylene glycolAMP-95 additiveACRYSOL RM-3000

rheology modifierACRYSOL RM-895 theology

modifierWaterTotals

121.22.55.32,51.0

37.513Z51.5

309.0

306,255.83.63.0

8.6

20.2

136.31114.6

215.2

OA

215.2472.7

2.55.3

37.5

129.4

3.83,0

2.0

21.7

1087.6

posite pahat, but we fiud that using ROPAQUE is the bestmethod when re-formulating, especially since these twobiding technologies work complementary to each other.For the addition of EVOQUE, we would recommend addingthe pre-composite polymer at a level of ~ ~.4 wet pounds(46.5% solids) for every dry pound of TiO2 remainhag tofully saturate the surface of TiO2 and facilitate good stabi-lization of the pigment-polymer composite,

As for dispersant level, it is best to keep the level constantbased on the total amount of mineral-based pigments andextenders in the formulation. As for coalescent demand,again it is important to keep the level constant based ontotal polymer solids in the formulation to facilitate goodfilm formation. Additionally, most composite pahats requireless thickener since the hydrodynamic volume of the pig-meat-polymer composite hacreases the inherent viscosityof the paint due to the bound water at the surface.

Depending upon what test you use to determine paintopacity or that strength, l’urther adiustment of TiO2 levelmay be required. Also, flatting materials may be addedor adjusted based upou your sheen requirements. As forother performance features, the composite paint was

FIGURE5 7a AND 7b I Scanning electron micrographs show a more uniformdistribution of Ti02 in paints made with EVOQUE pre composite polymer(b) compared to conventional binder (a). The brightness of the Ti02 inconventional binder indicates that much of the Ti02 i5 at or above thepolymer surface.

FIGURE 81 Tint strength and color matches over the entire color palette.

Control A (left) and ROPAQUEOpaque Polymer (right)

Control B (left) and EVOQUEPre~Composite Polymer (right)

Titanium White

Red Oxide

Fast Red

Magenta

Medium Yellow

Yellow Oxide

Phthalo Green

Phthalo Blue

CarbazoleViolet

Raw U tuber

Lamp Black

PAINT & COATINGS INDUSTRY ¯ ’t 31

Advancements in TiO2 Composite Technology

TABLE4 I Commercial EVOQUE pre-composite polymers in North America.

1140 No Premium Int/Ext Flat-SG1180 Yes Premium Int/Ext Flat-Gloss1133 No Quality Int/Ext Flat-SG

T~BLE5 J Reformulating protocol for EVOQUE pre composite polymer paints.

Contt’ol and Two Formulations¯ 8racket TiO2 level to determine a hiding match

Remove 12% and 20% (suggested);if only I paint is desired, remove 15%

¯ Keep total dry binder weight constant¯ Add 1.4 wet pounds of pro-composite polymer (46.5%) for

every dry pound of TiO2 remainingReduce the current binder to maintain total drybinder weight

¯ Keep Total PVC and VS constant¯ Add extender or, preferably, ROPAQUE

¯ Adjust additivesDispersant at constant % on mineral pigment andextender solidsCoalescent at constant % on total polymer solids(binder and ROPAQUE)

¯ Thickener level is generally lower

TABLE6 I Reformulation of a conventional paint with EVOQUE.

TiO2ROPAQUE opaque polymerTotal PVCEVOQUE pre-composite

polymer

Scattering (S/rail)Contrast ratioTint strength (Y, LB)Gloss (60°/85°)Abrasive scrub (cycles)Nousehold stain removalAdhesion (gloss alkyd)

50

5.70.92957.6

3/7

414

47%

99

50

(31)

5.90.93658.251649353%92

FIGURE 9 I Manufacturing process for composite paints with EVOQUEpre-composite polymen

approximately cgual to, or slightly better than, the con-ventional paint for abrasive scrub, stain removal andalkyd adhesinn.

The Paint Making ProcessPaint manufacturing with EVOQUE pt’e-composite tech-nology is nearly identical to the conventional point-mak-ing process, Several paint lnanufacturing options havebeen identified for EVOQUE, using dry and sinn’y gradesof titanium dioxides.

We worked with a paint manufacturer to run several250-gallon paint batch trials. Commercial quantities ofboth a high-quality fiat and semigloss formulation weremade using EVOQUE and universal-grade dry TiO2 fol~lowing the process outlined in Figure 9. The formationof the composite - which is the combination of EVOQUEpro-composite poly~ner and Ti02 - is critical in the paintmaking process.

In our paint plant trial, a grind was made in a separatedispersion tank under normal conditions. All liquid millbase materials were added first while mixing at 1000rpm. Dry extender pigments were added next and mixingspeed was increased to 1500 rpln. Dry TiO2 was addedwhile adjusting the mixing speed to 1500-2000 rpm andmixing lbr at least 15 rain. In a separate vessel or mixingtank, we charged the EVOQUE pre-colnposite polymer.water and defoamer under agitation. The grind wasthen added to the mixing tank with sufficient agitationfor at least 10 min. It is during this stage whereby theTiO2 is being added to EVOQUE pro-composite polymerthat the composite is being formed and that the 10 rainmix tinre ensures the composite reaction is complete.The rest of the letdown materials were then added to thebatch while mixing at I000-1500 rpm and adjusted withwater and thickeners to the desired high-and low-shearviscosities of the final paint.

Performance FeaturesWhile the key advantage of EVOQUE is hiding efficiency,there are other possible performance benefits with thistechnology due to its improved pigment distribution, Inte-rior paint properties such as household stain resistance

10% Ti02 in a high-quality semigloss and 15% TiO2 in ahigh-quality flat when reformulating with EVOQUE pre-composite polymer. A side-by-side drawdown of the con-ventional paint vs, the reformulated composite version ofthe same paint is shown, Tea, coffee and grape juice wereapplied to the dried paint fihn and allowed to penetratethe fibn For 60 rain before they were rinsed with tap water.The test panel was then washed with a non-abrasivecleaner for 200 cycles using a Gardner Scrub Machine.As seen in the exalnple, the composite paint looks cleanercompared to the conventional control paint.

Other notable improvements have been seen withEVOQUE in our exterior durability testing, such as tan-nin stain blacking and rust staining resistance. Thesame high-quality fiat paints used in the stain remaval

examined after 18 months on our test fences locatedin Spring House, PA. For tannin stain blocking testing,

we applied two coats of the test paints directly on a red-wood panel. The panel was then placed horizontally facedown on the exposure rack. As seen in the photo fromFigure 11, the composite paint, while slightly yellowin color due to some tannin bleeding, looks much better thml its conventional controh ’the same two paintswere also drawn down on a cold rolled steel panel, driedovernight and then exposed on a north vertical rack.After 18 months, the composite paint shows some slightrust spots, but is much better tbau its conventionalcontrol counterpart. These performance enhancelnentsobserved with EVOQUE can be attributed to the tighterfilms that are formed because of the better distribution ofthe Ti02 particles in the paint fihn. As for other exteriorproperties, we continue to monitor but expect equal toimproved performance over tinle.

Life Cycle Assessment andEnvironmental ImpactWe performed a comparative Life Cycle Assessment (LCA)of waterborne paints for interior and exterior wall protec-tion and decoration in the context of the European paintmarket in order to better understand the environmentalimpact arising lbom the use of ROPAQUE and EVt/QIJE, Thegoal of the LCA was to obtain an objective assessment ofthe environmental perfornlance of the waterborne paintsproduced with our opaque polymer and pre-compositetechnologies and many pre existing conventional bindertechnologies aml compare the results to help advance ourindusixy’s understanding of the situation.

The LCA was performed in compliance with the require-meats of International Standards (ISO 14040 aml IS()14044). A third party review and peel: reviews were performed by LCA and indust:ry experts to provide independentopinions on this shldy, Several waterborne paint tbrmula-tions reflecting typical PVCs were assessed in this LCA.

Both ROPAQUE and EVOQUE technologies offered abetter Eco-Profile due to the reduction of Ti02 levels inthe formulating paint systems tested. In general, paintsbased on both ROPAQUE opaque polymer and EVOQUEpre-composite polymer yiehted the lmvest impacls acrossthe categories studied in the life cycle stages Production,Application, Maintenance and End-of Life.

FIGUREIO I Household stain removal of convenlional vs.composite paints.

Stain RemovalHigh-Quality Semigloss

(26% PVC/36% VS)Conventional Composite Paint

Coffee

Tea

Stain RemovalHigh-Quality Flat

{45% PVC/36% VS)Conventional Composite Paint

c~ffee

Tea

FIGURE 11 I Exterior durability off conventional vs. composite paints.

High-Quality Exterior Flat(45% PVC/36% VS)

Tannin Stain Blocking1 8 Months

199 Ib TiOzConventional Paint

12.5% TiO~ ReductionComposite Paint

RUSt Staining ~es~sta nce" Ovel~ ~old R~lled Steel

199 Ib 1;i0z ; ; " 12.5% TiO~ Reductionc~nventio~nal paint ~ ~ Composite Paint

Left: High-quality flat made with conventional polymertechnology, Right: High quality flat made with EVOQUEpre-composite polymer technology.

ConclusionsROPAQIiE opaque polymer and EVOQ[IE pre-compositepolylner offer two distinct and complimentary approachesto reducing the use levels of TiO2 in interior and exteriorformulations, while maintaining equal hiding. Alternatively, they can also be used to significantly improve hid-ing at equal TiO2 levels. Other benefits, such as reducedformulation cost, improvements in barrier fi[lll properties,and better Eco-Profile of both interior and exterior water~borne paints, are also possible,

"Trademark of The Dow Chemical Company ("Dow") or an affiliated com-panyofDow,

References

PAINT 84 COATINGS INDUSTRY ¯ 33

ngs

The fihn formation process of one-compo-nent waterborne formulations involves asequence of water evaporation, coales-cence and further solidification. Thelength of this process determines when

the coated substrate can be further processed or used, Along drying time lengthens the total coating process untilfinished parts can be used, further processed or stacked.Accelerating the development of a coating’s early perfor-mance characteristics allows for increased productivityif a coating line can run faster, or if the interval betweennmlti-layer coatings can be shortened or if it can extendthe application period of a seasonally applied coating.

Waterborne coatings have several benefits. Stricterregulations drive the need for lower V0C emissions, andthus the use of waterborne solutions. In addition, water-borne coatings are less hazardous in the application pro-cess, are not fiammable, and equipment is safely cleaned.Maior R&D efibrts on waterborne systems have resultedin significant progress and broader availability of water-borne solutions. Today’s customers expect and demand

FIGURE 1 I Proposed crosslinking mechanism of the nanoaddltive.

~ functionality functionalityOxylink

nanoadditive

the availability of waterborne products that are perceivedas nmre ’green’ than solventborne alternatives.

Technically, waterborne coatings are high-tech prod-ucts that are complex and delicate to fornmlate. Thissituation increases the demand for a mare comprehensivetoolbox to balance the various performance and handlingrequirements of watethorne coatings. Nanoparficles havebeen used as functional ingredients in coatings for morethan 10 years, even though utilization was sometimeshindered by handling constraints. Aqueous dispersionadditives based on inorganic nmaoparticles conlprise afurther advanced class of materials that extend the formu-Iator’s toolbox for waterborne coatings.

Nanoparticle-Based Dispersion AdditivesDispersions of inorganic particles are well establishedin coatings, e.g., as pigment preparations. From geo-metrical considerations it is well known that the specificsurface area increases drastically (I/x) as the particlesize decreases? Benefits that rely on the surface area ofactive ingredients are therefore greatly enhanced whennanoparticlcs are used. Small amounts of such activeingredients can be very effective, which allows the use ofsuch materials as an additive in the lower percentage oreven sub-percentage range. In addition, these materialscan be used in clear and glossy coatings, as the visualappearance remains unchanged.

When using laanoparticles, the dispersion qual-ity provides a malor hurdle, as the particles need to

By Steffen Pilotek, Business Development Director Nanotechnology I Buhler Inc. (Nanotechnology), Austin, TX; andI(lau$ Steingriiver, Head of R&D/lechnical Sales, and Mar~ Herold, Senior Research Chemist I BONer PARTEC GmbH,Saarbr~Jcken, Germany