The following guidelines are provided based on Hauthaway’s experience in formulating coatings using our Hauthane polyurethane dispersions.  The guidelines are by no means exhaustive or meant to exclude other raw material or processing alternatives.  A list of raw materials suppliers for the products mentioned is appended below.

Coalescing Solvents

Aside from the co-solvent free grades (HD-2015, HD-4664, HD-4669, HD-4675), polyurethane dispersions contain n-methyl pyrrolidone as a by-product of the manufacturing process.  This co-solvent is a very effective coalescing solvent; consequently most of the Hauthane polyurethane dispersions require little or no additional co-solvent to form films.  However, it is possible to further enhance the performance properties of these films by adding additional coalescing solvents such as:

DPM – di-propylene glycol methyl ether (Dow Chemical, Eastman Chemical, Arco Chemical)
DPnB – di-propylene n-butyl ether (Dow Chemical, Eastman Chemical, Arco Chemical)
PM – propylene glycol methyl ether (Dow Chemical, Eastman Chemical, Arco Chemical)
Propylene glycol (Various) Texanol (Eastman Chemical)

These materials should be added at 5 - 15% based on the total formulation.  In the case of the co-solvent free grades, coalescing solvent should be added at 10 – 20% based on total formulation to attain optimal film formation properties.

Crosslinking Agents

The carboxylic functionality on Hauthane polyurethane dispersions makes them ideally suited for reaction with a number of crosslinking agents such as carbodiimides (Union Carbide’s Ucarlnk XL-29SE or Nisshinbo/GSI-EXIM’s Carbodilite V-02-L2), water dispersible isocyanates (Bayer’s Bayhydur 302 or Rhodia’s Rhodocoat WT-2102), polyaziridines (Bayer’s XAMA-7, NeoResin’s CX-100), melamines and epoxies (Hauthaway’s HA-806).

Defoaming Agents:

One of the most effective wetting agents for the Hauthane line is Dow Corning’s DC65 added at 0.01% on resin solids. We have found this product is less likely to create fisheyes than other defoamers.  Hauthaway also offers its own defoaming agents:

HA-601: A highly efficient, silicone defoamer for waterborne coatings systems.  This product may be added at 0.1 – 0.25% of total formulation.

HA-606: A silicone defoamer for waterborne coatings systems with rapid foam knockdown characteristics.  This product may be added at 0.01 – 0.1% of formulation.

Gloss Flattening Agents

To produce coatings with semi-gloss or flat gloss finishes, Hauthaway has found non-silica powders to be effective additives.  Pergopak M3 (Albemarle Corp.) or Bermasilk MK (Bergen Materials) are suggested products.

Flash Rust Inhibitors

The addition of ammonium benzoate at 1 – 2% of total formulation will eliminate flash rusting on metal substrates.

Leveling/Wetting Agents

The most effective wetting agents for the Hauthane line are BYK 346 and 348 from BYK Chemie or Dupont’s Zonyl FSN.  These materials should be added at about 0.25% of formulation.

Hauthaway also offers two products with proven effectiveness in leveling coating films.  These products are useful for both spray and brush applied coatings.

HA-504: A water dispersible fluoro-surfactant that may be added at 0.1 – 0.25% of formulation.

HA-508: A water-soluble silicone surfactant that may be added at 0.1 – 0.25% of formulation.

Mar-reducing Additives

Synthetic wax additives such as S. C. Johnson’s Jonwax 26 or silicone additives such as Dow Corning’s HV-490, may be used to reduce marring from incidental contact.  Polyethylene waxes such as those available from Micro Powders may also be used, but may separate with time.  Re-dispersion will be required.

Pigment Dispersants

Surfynol SE-F from Air Products is suggested for the dispersion of pigments in polyurethane dispersions at 4 – 6% on total formulation.

Rheology Modifiers

For thickening the viscosity of polyurethane dispersions, associative thickeners are available from several sources including:

These materials should be added at the manufacturers recommended levels.

UV Stabilizers

A 50/50 blend of Tinuvin 292/Tinuvin 1130 from Ciba Specialty Chemicals provides excellent exterior exposure protection. This blend should be diluted 1 to 1 with a water miscible solvent such as Dowanol DPM before adding to the polyurethane dispersion.  The recommended level of addition is 1 – 3% solids on solids.

Acrylic Emulsions

Generally, Hauthane polyurethane dispersions are compatible with a wide variety of acrylic emulsions.  Hauthaway has evaluated a number of grades from the major manufacturers and has reported on the compatibility and stability in a study entitled, “Compatibility and Stability of Hauthane Polyurethane Dispersions with Various Acrylic Emulsions.”  This study is available upon request or may be accessed on the Hauthaway web site: www.hauthaway.com.

Order of Addition

The order of addition of the components in a coating formulation is an important consideration in creating a stable liquid paint, as well as, an aesthetically pleasing and durable finish.  Hauthaway suggests the following procedure to produce the optimal coating properties.

Most formulations using polyurethane dispersions (PUD’s) also include acrylic emulsions.  If this is the case, start by placing the acrylic emulsion in a mixing vessel.

Next, add the coalescing solvent in a premixed blend with water under agitation.  This helps to prevent shocking the acrylic emulsion during the addition of coalescing solvent.  Shocking can result in grit formation or even gellation in extreme cases.  The ideal mixture would be a 50/50 blend of water and coalescing solvent, but any reduction of the cosolvent is beneficial.  Stir this mixture for at least 20 minutes.  A similar procedure may be followed for pure PUD-based formulations.

At this point, if the formulation is pigmented, add a pre-dispersed or solid pigment under agitation.  Allow sufficient time to adequately mix the pigment dispersion or to grind the solid pigment and to attain the ultimate color values.  Solid pigments may be ground into PUD’s directly, but will likely require the use of a wetting agent to attain the desired Hegman grind.  See the section on Pigment Dispersants above for suggested products and amounts.

If the acrylic emulsion has a different pH than the PUD, be sure to adjust the pH of the acrylic to the same range as that of the PUD using a diluted ammonia solution.  This will also prevent shocking of both the acrylic and polyurethane.  Under agitation, slowly mix in the PUD and stir for several minutes to allow sufficient blending.

The formulation may be thickened with rheology modifiers to the appropriate viscosity at this stage.  See the section above on Rheology Modifiers.

Finally, add leveling agents, UV-stabilizing packages and other additives at this point to complete the formulation.  Stir sufficiently to optimize the mix.