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Case Law of the Boards of Appeal

5.1.4 Achieving a higher degree of purity

In T 990/96 (OJ 1998, 489), it had to be examined whether the feature in dispute, which in fact represented a specific degree of chemical purity (in particular diastereomeric purity), constituted a "new element" imparting novelty to the claimed subject­matter.

The board stated that it was common general knowledge that any chemical compound obtained by a chemical reaction would normally contain impurities for various reasons and that it was not possible for thermodynamical reasons to obtain a compound which was ­ in the strict sense ­ completely pure, i.e. totally free of any impurity. It was, therefore, common practice for a person skilled in the art of preparative organic chemistry to (further) purify a compound obtained in a particular chemical manufacturing process according to the prevailing needs and requirements. Conventional methods for the purification of low molecular organic reaction products, which could normally be successfully applied in purification steps, were within common general knowledge. It followed that, in general, a document disclosing a low molecular chemical compound and its manufacture made this compound available to the public within the meaning of Art. 54 EPC 1973 in all grades of purity as desired by a person skilled in the art. Exceptional situations might exist which could justify a different conclusion. For example, there could be a situation where it was proved on the balance of probability that all prior attempts to achieve a particular degree of purity by conventional purification processes had failed (T 392/06).

In T 728/98 (OJ 2001, 319), the applicant (appellant) argued that the situation was such an exceptional one as mentioned in T 990/96. The claimed pharmaceutical composition differed from the state of the art because the particularly high purity level of the compound it contained could not be achieved by conventional methods.

The board found, however, that the applicant, who bore the burden of proving this allegation, had not provided the necessary evidence. In fact, the prior-art teaching yielded significant, even if small, quantities of the substantially pure compound using conventional purification methods. The general rule therefore applied that achieving a particularly high level of purity of a known compound was not a feature to be regarded as imparting novelty to such a product over the prior art.

In T 786/00 the arguments submitted by the respondent (opponent) with respect to T 990/96 (OJ 1998, 489) were not convincing, since that decision could not be applied to the present case. In contrast to T 990/96, the present case related to a process for the manufacture of polymers having specific properties (i.e. resistance to boiling water), characterised by the use of organic compounds having a required purity as starting components. In other words, the purity level of the starting components was an essential technical feature of the process, which could only be carried out in the required range of purity but not in all available grades of purity of the starting materials. In the board's view, there was a fundamental difference between the purity requirements presumed to exist for the isolation of a final product, and those for the starting materials used in a preparative process. By contrast, in T 990/96, the concern surrounding the starting materials was the precise opposite, in that it involved a mixture of stereo isomers which could be separated by fractional crystallisation so that the product resolved into two optically pure enantiomers with the aim of achieving an ultimate degree of purity. In that connection, the concern of the skilled person had to be presumed to be to use the most impure starting materials possible, consistent with the aim of obtaining a sufficient yield of product, which itself could be further purified. Consequently, the general statements in T 990/96 concerning the purity of the final products could not be applied directly to starting materials or, hence, to the present case.

In T 112/00 the board considered a composition including a solvent having a purity greater than 99% to be new over a prior art composition containing such a solvent whose purity was not specified. The board stated that the claimed composition could be considered as a final product and the solvent as the starting material. As in T 786/00, novelty would be established by the defined purity of the starting material.

The issue in T 803/01 was the novelty of a pharmaceutical composition which differed from prior-art compositions only in the degree of purity of one of its components. In the board's view each and every purification method, provided it was "conventional" but regardless of the extent of purification sought, was presumed to be automatically available to the public, and that in a fully enabling way, so as to amount to an effective novelty-destroying disclosure. As stated in T 100/00 in this respect, the term "conventional" could only mean "conventional in view of the concrete technical context concerned". Therefore the question of whether the degree of purity for the polylactide required in claim 1 provided a new element over the prior art had to be assessed in the concrete technical context concerned.

The board concluded in this case that the methods of purification described in document D2 - which had to be regarded as the relevant "conventional purification processes" in the concrete technical context concerned - would not succeed in providing the required degree of purity. Nor was there any ground for concluding that other "conventional" methods of purification would be capable of delivering the required degree of purity either. The board thus decided that there was a new element in the feature of a defined level of purity as set out in claim 1.

In T 142/06 the board noted that it followed from the considerations made in decision T 990/96, according to which a document disclosing a low molecular compound and its manufacture normally makes this compound allowable in all desired grades of purity, that the purity level of an organic compound is as such not an essential feature for the definition of this organic compound. However, in the case at issue it was evident that the content of chlorine ion of the claimed latex was an essential feature of the claimed latex, since, according to the patent in suit, only the latexes having this low level of chlorine ions enabled the production of films having the desired properties in terms of oxygen barrier properties and boil blushing properties. This implied that the claimed degree purity in terms of chlorine ion content could not be considered as an arbitrary degree of purity but that it amounted to a purposive selection. Thus, for this reason the considerations made in decision T 990/96 and, by way of implication, in decision T 803/01, did not apply to the case before the board. Furthermore, it also followed from the considerations made in decision T 990/96, that, before examining whether or not conventional purification processes described in the prior art would succeed in providing the required degree of purity, it should, in the board's view, first be checked whether the desirability of obtaining the claimed grade of purity existed in the relevant prior art (see also T 100/00 of 7 March 2003). The board was unable to discern the desirability of reducing the amount of chlorine ion to a very low content in the prior art documents. Thus, the board could only conclude that the inventor had really provided the public with something new, or, in other words, that there was a new element (i.e. chlorine ion content not greater than 500 ppm) in claim 1 which imparted novelty over the prior art.