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News

An integral part of the formulation

Bayer MaterialScience AG : 22 April, 2005  (Company News)
Researchers at Bayer MaterialScience have developed a novel blocking agent for prepolymers used to flexibilize epoxy systems.
“After fulfilling its function, it is incorporated into the resulting polyurethane or polyamide network,” says Dr. Christoph Gürtler, one of the developers.

Conventional blocking agents, on the other hand, are split off or emit a substance.
The fact that one- or two-component polyurethane or epoxy systems containing Desmocap® LP MMC 3306 do not undergo a deblocking reaction is advantageous.

“Such systems can be used for the formulation of permanently flexible coatings whose properties are not altered over time by released substances,” says Dr. Thomas Stingl, an expert in the Coatings, Adhesives and Sealants Business Unit of Bayer MaterialScience. The coatings do not blister, even when applied in thick coats. And because LP MMC 3306 emits no volatile organic compounds (VOC), it is also environmentally friendly.

The new blocking agent offers another advantage with respect to VOC directives: Polyisocyanates or isocyanate prepolymers blocked with the product have a significantly lower viscosity than those converted to storage-stable adducts using conventional reagents. LP MMC 3306 can therefore be used to formulate low-solvent or even solvent-free coatings. Viscosity is approximately 23,000 mPas, substantially lower than the roughly 100,000 mPas of conventional systems.

Reactive polyurethanes blocked with LP MMC 2206 can be used to correct a known weakness of solvent-free, epoxy-based formulations – although low-VOC formulations of this type have many interesting properties, the epoxy resins used in them must have a low molecular weight. The resulting casting resins or coatings are therefore extremely brittle and tend to crack, making them unsuitable for most applications. Blistering may also occur. This can be overcome by adding blocked polyurethane prepolymers like LP MMC 3306. As the formulation cures, the prepolymers are incorporated into the epoxy-amine network via true chemical bonds, making the resin more flexible. LP MMC 3306 is very effective. In particular it shows a long-lasting effect.
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