there’s a secret to perfect hdk pyrogenic · pdf filethere’s a secret to perfect...

THERES A SECRET TO PERFECT COATINGS AND INKS: HDK PYROGENIC SILICA
CREATING TOMORROWS SOLUTIONS
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HDK PROVIDES THE ULTIMATE IN RHEOLOGICAL AND FLUIDIZATIONCONTROL
ContentsProduct Performance and Expertise 3Unique Properties 4Rheological Performance 6Preventing Sedimentation 7Straightforward Processing 8Optimum Effectiveness 10Practical Examples 12High-Performance Powder Coatings 17
HDK Product GuideLeveling and Antisedimentation 18Layer thickness 18Hydrophilic HDK 19Hydrophobic HDK 19Automotive and Refinishing Applications 20Coil, Can and Corrosion Protection Coatings 24
General Industrial Coatings 26Floor, Furniture and Wood Coatings 27Printing Inks 28Service 30WACKER at a Glance 31

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HDK has the versatility to meet the many different requirements ofcoatings and printing inks. When itcomes to optimizing rheologicalproperties such as flow, fluidizationand triboelectric charging of coatingmaterials or powder coatings, HDK
pyrogenic silica gives you the selectivecontrol you need. HDK will get themost out of your products.
Targeted Product PerformanceWACKER has been producing pyro-genic silica for over thirty years and has continued to enhance its uniqueproperties. These efforts have madetodays HDK exceptional. HDK is not only a multitalented player, it alsoefficiently optimizes specific qualities in a wide range of products includingcoatings, printing inks and many more.
The unique assortment of hydrophobicand hydrophilic HDK grades givesprecise rheological control of all types of coating materials and powder paintsto the requirements of the application.When it comes to thickening, thixotropy,antisedimentation, pourability andelectrostatic applications, HDK impartsexactly the qualities you need for yourapplication.
Concentrated ExpertiseAn innovative, motivated partner to the coating and printing ink industry,WACKER SILICONES backs up itsunbeatable products with first-classservice. To satisfy the requirements ofthe market and our customers, weresearch, develop and produce binders,pigments and additives that continu-ously improve product performance andenhance applications. Our customerscan always count on expert, customizedsupport as well as comprehensivetechnical service. We have a localpresence worldwide.
HIGHEST RESULTS FROMEVERY APPLICATION

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UNIQUE PROPERTIES FOR VERSATILE APPLICATIONS

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The numerous systems for pigments,surface and powder coatings mustmeet specific requirements in produc-tion and storage and during applica-tion. This requires consistently highquality and efficiency. With HDK, you will reach your goals reliably andeconomically.
Many Possible ApplicationsIn close cooperation with the coatingsand printing ink industries, WACKERSILICONES has developed a wide rangeof hydrophobic and hydrophilic HDK
grades for numerous application areas.HDK is the perfect solution for everysort of ink and coating used on cars,furniture, ships, parquet floors anddiverse printing processes.
Two-component solvent-containingand high solids coating materials
Solvent-containing and high solidsbaking systems
Air-drying solvent-containing and high solids coatings
Solventless two-component and UV curing systems
Water-thinnable coating materials Powder coatings Systems for offset, gravure, flexo-
graphic and silk-screen printing
Clear Application AdvantagesWith its unique properties, HDK
improves the important propertiesof coatings and printing inks:
Rheology/Flow Control of film thickness and leveling Antisedimentation agent for pigments,
fillers and matting agents Control of flow and fluidization
properties
Appearance No influence on color High transparency, optimum high gloss Less water absorption, improved print
sharpness
Additional benefits Improved corrosion protection,
wet-adhesion, mechanical properties Protection of metallic pigments Charge control High storage stability
Handling No preactivation in solvents necessary Rheology unaffected by temperature
profile No subsequent seeding Reduced spraying, dusting, misting Improved stackability

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CUSTOMIZED RHEOLOGY FOR PERFECT SURFACES
To adjust a coating materialsrheological properties, you need toensure that the binder, solvent andpigments/filler ratio are perfectlymatched. As a rheological additive,HDK gives perfect control ofperformance in every phase.
Perfect LevelingIn practice, coating materials areexposed to a wide range of shear forcesduring production, transportation, stor-age and application. Production andapplication entail especially high levels of shear, which can influence the qualityof the coating. Very low levels also have an effect. The goal is to achieve auniform, smooth surface once a coathas been applied in the appropriatethickness. This requires achieving thedesired leveling while at the same timepreventing run-off. Here, HDK acts as a thixotropic agent and fine-tunes the relaxation rate of the viscosity in thefreshly applied coat.
Overview of the shear rates and viscosities that occur during a coating materialslifecycle from production to application
0.001 0.01 0.1 1 10 102 103 104 105
103
102
10
1
0.1
0.01
Shear rate
Vis
cosi
ty
[Pa
s]y
Storage Transportation
Coating material production
Application
Controlledwith HDK
Controlledwith HDK
Controlledwith HDK
Settling
SaggingFree-flowingSettling
Consistencyin drum Application
Controlled bybinders,pigments andsolvents
Packaging

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Another important task of HDK is toprevent sedimentation of fillers andpigments as a result of very low shearduring storage and transportation ofcoating materials.
Custom FormulationsA coating material formulation mustbalance very diverse requirements: on the one hand, high viscosity must be achieved in the low-shear range to prevent sedimentation (this may becombined with a yield point). On theother hand, the formulation must get theleveling properties right while preventingsagging after application.
There are many other parameters thatmake adjusting the rheological proper-ties of a coating material a highlycomplex task:
Binder polarity Binder molar mass and molar mass
distributions Choice of solvent (solubility parameter) Base viscosity of the binder/solvent
system Volume fraction of the pigments
and fillers Interactions between components Use of additional surface-active
products (wetting or dispersing agents,etc.)
Reliable SolutionsThese factors all influence the rheologi-cal properties and therefore affect theselection and dosing of rheologicaladditives. The wide range of HDK gradesoffers a solution for every demand. Theinterfacial situation energy of any systemcan be adjusted to the required valuewith hydrophilic HDK for non-polarsystems through to hydrophobic gradesfor more polar systems. For example,through the choice of a particular HDK,it is possible to shift the emphasis eithertoward control of film thickness ortoward optimum leveling.
CONSISTENT QUALITY BY PREVENTING SEDIMENTATION

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Equipment Fineness of grind [m]
Hydrophilic Grades Hydrophobic Grades
HDK N20 HDK T30 HDK T40 HDK H15 HDK H18
Dissolver 0 5 10 25 60 75 30 75 30 50
Horizontal (Netzsch) mill 0 5 0 5 0 5 0 5 0 5
Three-roll mill 0 5 0 5 0 5 0 5 0 5
Grindometer Measurement in Accordance with DIN ISO 1524
STRAIGHTFORWARD PROCESSING FOREFFICIENT PRODUCTION WORKFLOWS
Economic and smooth processesincrease production efficiency. Thereis a clear advantage to using HDK
to create easy-to-process productsprecisely tuned to specific coatingand printing ink systems.
Delivered Ready-to-UseAccording to the available data,pyrogenic silica, if used appropriately,does not have adverse effects on health or the environment. HDK can be processed efficiently: it can be usedwithout additional treatment before being integrated into production. Thereare no restrictions on the temperature at which it is incorporated.Formulating is made easier by theuniformity and consistently high qualityof HDK. The rheological efficacy ofHDK depends on how finely the pyro-genic silica is broken down. That meansthat with better dispersing machines,
Accuracy of measurement 5m. To obtain optimum colloidal particle dispersion, the mixing equipment must be selected to suit the agglomeration state of the particular HDK grade.

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higher viscosity values can be achievedfor the same HDK concentration.Efficacy does not depend on the puredispersion time, but rather on optimiza-tion of the shear forces. To attain optimal rheological stability, it has proven useful to first incorporateHDK into a high solids binder/pigmentphase. HDK grades with large surfaceareas (>200 m2/g) should be dispersedwith bead mills or three-roll mills. Insome cases, a powerful dissolver mayalso be adequate.
On-Location Around the WorldWith i

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