ARD SURFACE CLEANERS

must work harder thanever. The days of just clean-ing a surface are long gone.Users expect convenient,inexpensive products thatreduce the time and effortneeded for cleaning in pri-vate households as well asin the I&I industry.

In addition, expectations for visuallyrecognizable benefits have grown. Astreak-free, glossy surface supportsthe impression of it not just beingclean but hygienic, pure and safe forconsumers. More time for leisure activ-ities for consumers or reduced expens-es for cleaning staff in institutionalcleaning are achieved by less frequentand easier cleaning with reducedmechanical force. Special additivessuch as polymers are finding greateruse in cleaners to achieve user-friend-liness and long-lasting cleaningeffects, such as less resoiling and easi-er cleaning over time. The efficiency ofpolymers depends not only on their

structure but also on the kind of sur-face to be cleaned.

Challenges for CleanersOne major challenge for hard surfacecleaners is the various surfaces thatmust be cleaned. Surfaces can be char-acterized by their surface energy. Thissurface energy provides information onthe polarity and charge of the material.It helps to predict the behavior of clean-ing ingredients on different surfaces.

Common hard surfaces with differentsurface energies include glass andceramic; metals, such as stainless steelor aluminum; and plastic materialssuch as SAN, melamine or polypropy-lene. Glass and ceramic havehydrophilic surfaces with relativelyhomogenous and consistent character-istics, whereas many plastic materialshave hydrophobic surfaces with greaterroughness and inhomogeneity.

The surface energy can be calculatedbased on contact angle measurements.The contact angle of water describesdirectly the hydrophilicity of surfaces;this has been measured on various sur-faces (see Fig. 1 next page).

Another challenge in hard surfacecleaning is the influence of differentkinds of soiling. Soils are mainly com-posed of solids such as dust and otherparticles, mineral salts such as limeand rust and organic substances suchas oil, fat and soap.

Just as with surfaces, soils too may beclassified by their hydrophilic charac-ter. The various possible combinations

H

Hard surfaces cleaners must do more than remove dirt and grime. Consumersexpect products to repel dirt and improve gloss with less effort than ever.

Cognis researchers detail how a new class of polymers makes it all possible.

HAPPI • November 2007 • www.Happi.com 97

Long-lasting Effect PolymersFor Hard Surface Cleaning

Dr. Thomas Albers and Dr. Christine WildCognis GmbH

Monheim, Germany

One major challenge for hard surface

cleaners is the varioussurfaces that must

be cleaned.

of soiling and surfaces result in differ-ent behavior regarding adhesion.Greater adhesion of the soiling makescleaning more difficult. This can beovercome by surface modification withsurface active polymers. They changethe adhesion properties of soils andfacilitate cleaning.

Hard Surface Cleaner PolymersPolymers with specific characteristicsand functionalities can be designeddepending on the type of monomers,their molar ratios, molecular weightand molecular weight distribution

chosen for polymerization. Thus, poly-mers can be produced with customizedhydrophilic or hydrophobic properties.

Polymers in hard surface cleanershave the ability to disperse soil, com-plex minerals and adjust viscosity.Nowadays, polymers are under discus-sion for hard surface cleaners to pro-vide secondary cleaning benefits,which may include, for example,immediate visible effects such asenhanced gloss. Expectations havenow changed with regard to addition-al long-lasting benefits, the challengehere being to provide these benefits

without build-up effects of the poly-mer over time (Fig. 1).

Polymers can be classified in thesame way as surfactants with respectto anionic, cationic, nonionic andamphoteric substances. The structureis an important aspect in surface mod-ification.

Nonionic and anionic polymers donot provide long-lasting effectsbecause hard surfaces are normallynegatively charged and thus the affin-ity of those polymers is very low.Cationic polymers show affinity tohard surfaces, but are limited in usedue to incompatibility with many sur-factants and other ingredients. Thereis also a limitation in the pH range forthe final formulation.

Polymers with amphoteric structurealso show significant affinity to sur-faces and can easily be formulated inhard surface cleaners. Whereas thecationic charged part of the polymer isresponsible for the adhesion of thepolymer on the surface and hence pro-vides the long-lasting effect, the non-ionic and anionic parts, which are ori-ented toward the environment, influ-ence the hydrophilicity of the modifiedsurface.

Hydrophilic amphoteric polymerscan reduce the contact angle of wateron polar surfaces such as glass andceramic and improve the wetting per-formance. Specially designed, hydro-phobically modified, amphoteric poly-mers raise the contact angle on polarsurfaces and reduce the contact angleof non-polar surfaces such as plasticmaterials; whereas hydrophilicallymodified amphoteric polymers havevirtually no effect on non-polar sur-faces. Modification of surfaces withamphoteric polymers in aqueouscleaners provides various immediateand long-lasting visible benefits.

Polyquart Ampho 149 and PolyquartPro are hydrophobically-modifiedamphoteric polymers, compatible withall types of surfactants. WhereasPolyquart Ampho 149 is stable frompH 3-10, Polyquart Pro has beendesigned for applications ranging frompH 1-13.

Immediate EffectsPrimary cleaning performance is the

98 HAPPI • November 2007 • www.Happi.com

Fig. 2: Gloss in Leave-on Application on Ceramic Tile

Fig. 1: Contact Angle on Surfaces

Fatty alcohol ethoxylate—formulation without poly-

mer

Fatty alcohol ethoxylate—formulation with Polyquart

Untreated

Polyquart Ampho 149

Polyquart Pro

Hydrophilic Polymer

120

100

80

60

40

20

0

Cont

actA

ngle

[°]

Glass Ceramic Stainless Car PVC PPSteel Panel

most important immediate and visi-ble effect. Excellent primary cleaningis achieved by an optimized combina-tion of surfactants, acids or bases andother auxiliaries. Fatty alcoholethoxylates, for example, are common-ly used in hard surface cleaners.However, they reduce the gloss, leavevisible residues on surfaces andrequire thorough rinsing with water.

Convenient, ready-to-use spraycleaners or wet wipes with low levelsof salt or acids can be based on fattyalcohol ethoxylates as the single sur-factant, if amphoteric polymers areadded to the formulation in order toavoid unwanted side effects. Glass,ceramic tiles and shiny metals willmaintain their original shine (Fig. 2).

Quick and spotless drying is anotherrequirement for convenient cleaners.After rinsing, the water film does notdrain homogenously on surfaces thathave not been cleaned with formula-tions including special polymers.Water droplets are left on the surfaceand these are subsequently visible asspots when the surface is dry.

Surfaces modified by hydrophobical-ly-designed amphoteric polymers pro-vide a uniform and quick water draindue to the higher contact angle. Waterdrains within seconds and withoutleaving spots on vertical surfaces thathave been cleaned with formulationscontaining these hydrophobic poly-mers. There is no need for dry-wipingafter cleaning. This benefit is also vis-ible on cars cleaned withsuch formulations.

Surface modification withhydro- philic polymersallows a homogenous butslow water drain which maytake minutes upon rinsingwith water.

Long-Lasting EffectsSaving time in hard surfacecleaning can best beachieved by attaining long-lasting effects. Long-lastinggloss, soil release or lessresoiling and easier cleaningnext time are features ofconvenient cleaners.

Normally, solids such asrust or limescale adhere to

the surface meaning frequent clean-ing is required. A simulation trial fortesting adhesion of mineral residueshighlights the obvious difference afterprior modification. In this experi-ment, mineral salt solutions aresprayed on ceramic tiles and thensolidified directly on the tile. Thesolidified soil can easily be removedjust by rinsing with water. Even afterseveral rinses with water, it is possi-ble to prevent limescale build-up onhydrophobically modified ceramictiles (Fig. 3).

Lime soap or burnt-on fat are soilswhich are difficult to remove. Theyoften require a long contact time and

higher concentrations of cleaners aswell as additional mechanical force.Surface modification with amphotericpolymers provides a protective layeron the surface. The polymer filmbetween the soiling and the surfacedecreases the adhesion of soiling andfacilitates easier cleaning next time.

One test method to demonstrate theso-called “Easy-To-Clean-Again”effect uses burnt-on lime soap.Experiments have shown an obviouseffect with the use of hydrophobicamphoteric polymers (Fig. 4).

SummarySecondary cleaning effects such as

gloss and quick drying can beobtained by surface modifica-tion with specially designedpolymers in hard surface clean-ers. In addition, speciallydesigned hydrophobic ampho-teric polymers show long-last-ing benefits in terms of glossretention as well as quick andspotless drying.

This effect is still noticeableafter repeated rinsing withwater due to the improvedaffinity of these special poly-mers to various types of hardsurfaces. They can providereduced adhesion of soils onmany surfaces. Hard surfacesbecome less quickly resoiledand cleaning is much easiernext time. l

HAPPI • November 2007 • www.Happi.com 99

Fig. 3: Less Resoiling

Untreated and rinsed withwater

Pre-cleaned with formula-tion including Polyquart,

soiled and rinsed withwater.

Fig. 4: Easy-to-Clean-Again Effect

Left: soiled tile, then cleaned with water and sponge.Right: pre-cleaned tile including Polyquart, soiled andcleaned with water and sponge.