Properties / Applications: Desmodur Z 4470 SN/BA differs from conventional types of aliphatic polyisocyanates by having better solubility/dilutability in mild solvents (aromatics, aliphatics) as well as better compatibility with air-drying alkyd resins. Desmodur Z 4470 SN/BA polyisocyanate is mainly used as an “additive resin ” in existing, ready-for-use coating formulations to accelerate their drying, curing, and chemical crosslinking to obtain shorter dry, tape, and recoat times, and improved hardness and gasoline resistance in cured films. When Desmodur Z 4470 SN/BA is used as an additional drying and curing component in air-drying alkyd coatings, NCO/OH ratios of less than 0.5/1.0 are usually sufficient. With some types of alkyd resins, higher additions of Desmodur Z 4470 SN/BA polyisocyanate will cause embrittlement. The best level of addition should be determined in each case. Weathering of films containing Desmodur Z 4470 SN/BA polyisocyanate is mostly dependent on the type of alkyd resin used. The slight yellowing of alkyd resins modified with unsaturated fatty acids is slightly increased by the polyisocyanate addition. This tendency to yellow is more pronounced at drying temperatures above 176°F (80°C). It is recommended that forced drying be carried out below 176°F (80°C). Combining Desmodur Z 4470 SN/BA polyisocyanate with flexible polyesters and acrylics or properly formulated polyester/acrylic blends yields two-component polyurethane coatings with outstanding weather resistance. Adding Desmodur Z 4470 SN/BA polyisocyanate limits the potlife of the coating material. The potlife is approximately 8 hours for coating materials adjusted to spray viscosity. The potlife is influenced by the ingredients used in the formulation of the coating. As with any product, use of Desmodur Z 4470 SN/BA polyisocyanate in a given application must be tested (including but not limited to field testing) in advance by the user to determine suitability.

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