Pouring spheres into a loose pile will result in a density of, at most, 64 percent, the theoretical maximum packing density for flowable materials. With a solids content of 60 percent, the latest generation of polyurethane dispersions for the coating of textiles on exhibit by Bayer MaterialScience at Techtextil 2007 in Frankfurt am Main is close to this physical limit. These waterborne raw materials make it possible to achieve high add-ons in a single pass. This is primarily an economic advantage resulting from better machine utilization and reduced energy costs.
The star of the products on exhibit is Impranil® DLU. “This is an aliphatic, high-performance polyurethane dispersion characterized by extremely good foamability, flexibility and hydrolytic stability,” says Thomas Michaelis, a textiles coatings expert at Bayer MaterialScience. Impranil® DLU was developed for the particularly high-quality coating of upholstery, automobile seats, sporting goods and other technical goods.
The “60 percent dispersion” range includes three other products: Impranil® LP RSC 1554 gives textiles more volume and body, and is well suited to mechanical foaming. This dispersion can be used to formulate fashionable and cost-effective coatings for such things as outerwear fabrics. It is also used for the finishing of non-wovens. Impranil® LP RSC 1380 is used in similar applications primarily to improve the haptic properties of fabrics. Impranil® LP RSC 1537 is a specialist for the transfer process, in which the top layer – in other applications it would be called a topcoat – is first applied to a transfer paper. Impranil® LP RSC 1537 is extremely well suited as an adhesion layer, which together with the top layer is subsequently transferred to the textile.
In addition to the high-solids products, Bayer MaterialScience is also showing a new aliphatic polyurethane dispersion for the top layer at this year’s Techtextil. Impranil® LP RSC 1997 makes the surface of synthetic leather extremely resistant to abrasion and aging. Just like the high-solids products, the dispersion is free of organic cosolvents, thickening agents and external emulsifiers. “With the latest product generation, the days in which environment-friendly, waterborne dispersions for the coating of textiles were dismissed as too thin or not resistant enough can finally be relegated to history,” says Michaelis with conviction.