The appeal of the patent proprietor lies from the decision of the opposition division revoking patent EP 3 156 427, for the reason that claim 1 does not meet the requirements of Article 84 EPC.
Claim 1 refers to a method for preparing a superabsorbent polymer comprising a crosslinked polymer.
It was common ground that the following feature defining the step of the surface crosslinking reaction according to claim 1 was not part of the claims as granted and could, therefore, following the ruling of G 3/14 be examined at the present stage of the proceedings:
"the initial reaction temperature of the reaction solution containing the surface crosslinking agent with the base polymer at the start of the cross-linking reaction is 100 to 170 C, and the temperature rise time from the initial reaction temperature, until the time when the maximum reaction temperature is reached, is controlled to be more than 10 minutes and not more than 40 minutes"
The requirement of clarity is meant to ensure that the skilled person can determine unambiguously the scope of the subject-matter for which protection is sought, in particular in order to know when (s)he is working within or outside the ambit of the claim. In view of that, it has to be answered whether the amendments introduced into the claims as granted result in the boundaries of the claim to be unambiguously defined. Also, the normal rule of claim construction is that the terms used in a claim should be given their broadest technically sensible meaning in the context of the claim in which they appear.
Regarding the "initial reaction temperature", the Board agrees that the requirements of Article 84 EPC are not met because no clear meaning can be attributed to the term "the initial reaction temperature of the reaction solution containing the surface crosslinking agent with the base polymer at the start of the cross-linking reaction is 100 to 170 C", so that the boundaries of claim 1 are ambiguous.
In particular, no definition of the term "initial reaction temperature ... at the start of the cross-linking reaction" is present in operative claim 1. In view of the wording of the claim itself ("initial reaction temperature", "start of the cross-linking reaction"), the Board considers that said initial reaction temperature can - due to the linguistic structure of the passage - only refer to the temperature at which the cross-linking reaction effectively starts. In that regard, the Board sees no reason to consider that this interpretation, which is fully in line with linguistic considerations, would not be a technically sensible reading that would not be considered by the skilled person.
However, it is unclear to the Board how such an "initial reaction temperature", namely "the start of the cross-linking reaction", is to be effectively determined.
When a granted claim has been amended by insertion of a feature which was not part of the claims as granted, that feature, i.e. the amendment, is subject to examination under Article 84 EPC (G 3/14) and therefore should be clear for the skilled person when read in the context of the claim itself. This is due to the fact that in opposition and appeal proceedings before the EPO, the patentee has in principle - irrespective of the question of the admittance of late submissions - the opportunity to amend the claims to bring them into line with more specific passages of the description. Thus, a claim should not be interpreted in a specific sense by implying into it features which appear only in the description, as this would go contrary to the requirement of clarity and would deprive claims of their intended function. Therefore, the appellant's arguments based on an interpretation of the amendment made in claim 1 in the light of the description did not convince.
At the oral proceedings before the Board, the appellant argued that some passages of the Korean original PCT patent application as filed (D27) had not been translated correctly in the European application as filed (D13). A certified translation had been filed as document D33 with the statement of grounds of appeal. In view of the translations of D33, the skilled person would understand that the initial reaction temperature specified in claim 1 was the temperature of the reactor in which the surface crosslinking reaction was performed, whereby said temperature could be easily measured using common methods.
This argument presupposes that a claim should be interpreted not only in the light of the patent specification, but even in the light of the translation of the PCT-application submitted to the EPO at the time of entry into the regional phase, or - as in the present case - in the light of a corrected translation thereof filed during the appeal proceedings. However, there is no legal basis for such an approach. According to Article 14(2) EPC the translation filed with the EPO at the time of entry into the regional phase may be corrected. However, this does not mean that a correction of that translation would automatically lead to a correction of the corresponding passage in the patent specification. This would require a specific request to this effect, which was not made in the present case.
Furthermore, the Board considers that an amendment of a granted claim taken from the description of the patent specification should be clear in itself, which excludes that the inserted feature being interpreted contrary to its express wording in the sense of a specific passage of the description. Therefore, the appellant's argument must be rejected.
For these reasons, the feature "the initial reaction temperature of the reaction solution containing the surface crosslinking agent with the base polymer at the start of the cross-linking reaction is 100 to 170 C" does not meet the requirements of Article 84 EPC.
The appeal is dismissed.