Where an invention concerns a chemical product, this product can be defined in a patent claim directly by its chemical formula or rather by the exact ingredients of the formulation. If need be, the product may be defined indirectly as a product of a specified process. If no such definition is possible, the European Patent Office (EPO) – as an exception – allows the definition of the claimed product by its parameters, provided that these parameters can be clearly and reliably determined.

The recent decision T 1389/07 of the Technical Board of Appeal 3.3.06, dated December 14, 2009, shows again that parameter-defined product claims are to be regarded as an exception limited to cases where the product can otherwise not be defined. The decision concerned a cleansing composition comprising a polymer/oil blend. The product claim characterized the polymer/oil blend solely by adhesiveness parameters. However, since the inventive polymer/oil blends were explicitly disclosed in the application, a definition of the polymer/oil blends in the claim via the respective polymers and oils was also possible. Therefore, the board did not accept the product claim based on the adhesiveness parameter of the blend. The applicant could only overcome the objection of lack of clarity pursuant to Article 84 of the European Patent Convention with a modified product claim specifying the polymers and oils as per the invention.