German technical background VOK-370 leveling agent Used to reduce surface tension in solventborne coating systems replaces BYK-370

German technical background  VOK-370 leveling agent

VOK-370 polyester-modified silicone surface additive for solventborne coating systems and unsaturated polyester gel coatings. Contains hydroxyl functional groups. Significantly reduces surface tension. 

Product information 

Chemical composition 

Polyester modified polydimethylsiloxane solution containing hydroxyl functional groups. 

Typical physicochemical data 

The data presented on this data page is typical and not a product specification. 

Density (20 °C): 0.92 g/ml 

Non-volatile (10 min., 150 °C): 25% 

Solvent: xylene/alkyl benzene/cyclohexanone/glycol monophenyl ether 75/11/7/7 

Flash point: 25 °C 

Hydroxyl value (solids): 35 mg KOH/g 

Storage and transportation 

Stir well before use. At temperatures below 5 °C, the product may delamination or become turbid. Heat to 20 °C and stir well. 

Application areas 

Coatings industry 

Product features and benefits 

Due to its high surface activity, the additive accumulates on the coating surface. Its high activity allows the additive to be incorporated into the polymer network and anchored to the coating surface. VOK-370 improves surface slip, solvent resistance, weather resistance, anti-blocking and reduces dust accumulation. If the additive is fixed to the coating surface by an active group, these properties last longer than conventional inactive silicones. The additive also reduces surface tension and improves substrate wetting. Improves leveling and prevents the formation of Benard vortices.

Recommended Use 

VOK-370 reacts with resin by hydroxyl groups and is mainly used in solventborne two-component polyurethane systems. It can also react with the following resin systems: alkyd/melamine, polyester/melamine, acrylates/melamine, self-crosslinking acrylates and epoxy systems. The additive is best used in wood and furniture coatings, leather coatings and canning coatings.

Recommended dosage 

0.1-1% additives (supplied form) are based on total formulation. 

The above recommended dosage is for reference, and the appropriate dosage needs to be determined through a series of tests. 

Addition method and processing guidance 

The additive can be added at any stage of the production process, including post-adding. 

Special considerations 

When the paint is used outdoors, weathering will remove the top layer of resin and additives from the coating. Testing must be carried out to determine whether these conditions will allow the additive to be effective for a long enough time. In order for the additive to be incorporated into the coating system through its functional groups, the coating needs to be carefully and evenly sanded before recoating or repairing to ensure sufficient adhesion. 

Room temperature curing system 

Product features and benefits 

This additive improves the leveling of unsaturated polyester gel coatings. It also prevents the formation of craters and fisheyes, improving the acceptability of spray paint mist or dust. 

Recommended dosage

0.1-0.3% additive dosage (purchased form) is based on total formulation. 

The above recommended dosage is for reference, and the appropriate dosage needs to be determined through a series of tests. 

Addition method and processing guidance 

The additive can be added at any stage of the production process, including post-adding. The addition of the additive at the end of the process has proven to be effective. 

Special instructions 

Unlike so-called silicone fluids, the additive is very convenient to use. Before use, however, we recommend that you test it for foam stabilization, recoating and crater tendencies in specific systems.