With the polyurethane dispersion Imprafix® 2794 XP, Bayer MaterialScience has developed a high-performance crosslinking agent for the coating of temperature-sensitive textile fibers. One example is elastic polyamide fibers, which are used most frequently in swimwear and athletic attire, but also in outerwear, underwear, panty hose and shoes. The blocking agent in the dispersion enables formulations with an extremely long pot life, meaning that they can be stored almost indefinitely before they are used.
On the other hand, temperatures of around only 125 °C are sufficient for deblocking and initiating the crosslinking process. Such formulations can therefore be used to coat elastic polyamide fibers, without damaging them. "Conventional blocked crosslinking agents require a higher temperature of 150 °C, at which such textile fibers experience a loss of elasticity," explains Thomas Michaelis, a textile coatings expert at Bayer MaterialScience.
Coatings based on the Impranil® line of polyurethane dispersions and the new polyisocyanate dispersion adhere extremely well to textile fabrics. They improve the fabric's scratch resistance and make it very resistant to abrasion. Such coatings are also extremely resistant to dry cleaning and washing. Because of the long pot life, formulations based on Imprafix 2794 XP can be used flexibly with respect to time and as needed in the production of textiles and synthetic leather.
The new crosslinker also offers advantages for applications beyond the textile industry. The baking coating of perfume bottles or fine dining glassware is usually performed at temperatures above 180 °C. With many conventionally blocked crosslinkers, deblocking at such temperatures is associated with clearly perceptible yellowing. Not so with the new product, in which the isocyanate groups are blocked with dimethylpyrazole (DMP). The decorative coatings produced are dishwasher-safe and lightfast.
Imprafix 2794 XP is also an alternative to other polyisocyanate crosslinkers for baking coatings used in automotive OEM coating applications. Formulations based on the new crosslinker can be applied as a filler, for example, and offer good protection against mechanical loads and stone chipping.