T 0879/21 (Geopolymer composite/SYNTHOS) 21-04-2023

1. Sufficient substantiation of the ground for opposition (Article 100(b) EPC)

1.1 The respondent argued that the ground for opposition under Article 100(b) should not have been admitted by the opposition division because this ground had not been substantiated in the notice of opposition. The objections presented in the notice related to the clarity of the claimed subject-matter, not sufficiency of disclosure.

1.2 These arguments are not convincing. Pages 4 to 9 of the notice of opposition set out the reasons why the opponent considered that the claimed invention was not sufficiently disclosed. The arguments presented were not limited to the clarity of the terms "geopolymer" and "geopolymer composite" or to a mere allegation that the claimed subject-matter was excessively broad.

1.3 In fact, the notice of opposition set out the reasons why the skilled person would not be able to prepare the claimed geopolymers using all the aluminosilicates mentioned in the patent. It also set out why a skilled person would not be able to prepare geopolymers encapsulating athermanous material by carrying out the process described in paragraph [0026] of the patent. Reasons were presented why the milling step specified in the patent would result in the destruction of the structure of the composite and afford a simple physical mixture of the relevant ingredients. Technical arguments were provided to substantiate this objection. Further arguments were set out why the skilled person would not be able to prepare the foam defined in claim 6 as granted.

1.4 For these reasons, the board concludes that the ground for opposition under Article 100(b) EPC was effectively raised in the notice of opposition as required by Rule 76(2)(c) EPC and that the opposition division's division decision to deal with this ground was correct. Whether the objections under Article 100(b) EPC are strong and will finally succeed is not relevant for deciding whether this ground for opposition was substantiated and effectively raised in the notice of opposition.

1.5 Admission of documents D15 to D17 and D18 to D21

1.6 During the oral proceedings held on 3 March 2021, the opposition division decided not to admit into the opposition proceedings:

- D15 to D17, filed by the opponent (now appellant) with its letter dated 23 December 2020, the last day for making written submissions or amendments under Rule 116 EPC

- D18 to D21, filed by the proprietor, (now respondent) on 11 February 2021, in reply to the filing of D15 to D17

1.7 A board should only overrule the way in which a department of first instance exercised its discretion when deciding on the admission of late-filed submissions if it concludes that that department did so according to the wrong principles, without taking into account the right principles or in an unreasonable way, and has thus exceeded the proper limits of its discretion (see "The case law of the boards of appeal" 10th edn., section IV.C.4.5.2).

1.8 The board considers that in the current case, the opposition division exercised its discretion using the wrong criteria and in an unreasonable manner when deciding not to admit the aforementioned documents.

1.9 On page 5 of the decision under appeal, when deciding on the admission of D15 to D17, the opposition division argued, in the first place, that two scenarios could be foreseen, namely:

- "if the opponents arguments in D15-D17 do not go beyond what has already been argued in the notice of opposition they are not more relevant that what already is on file"

- "If the opponents arguments provided in D15-D17 do go beyond what has been submitted in the notice of opposition these arguments and evidence are late filed and the proprietor is not given a fair and expedient chance to respond"

1.10 As submitted by the respondent, the implementation of this approach would inevitably result in any new submission being inadmissible. In fact, this approach pre-empts any possibility to have considered new arguments or facts submitted in preparation for the oral proceedings until the date set under Rule 116(1) EPC. This is unreasonable and not in line with the established case law.

1.11 Under established case law, when exercising its discretion to admit late-filed documents, the opposition division should determine their relevance. Prima facie relevance should the principal factor governing admissibility of late-filed documents (see Article 114(2) EPC and "The case law of the boards of appeal", 10th edn., sections IV.C.4.5.1 and IV.C.4.5.3).

1.12 The opposition division decided that D15 to D17 were not "prima face relevant", giving the following reasons on page 6 and 7 of its decision.

- D15 had been filed to provide evidence that certain foams according to the invention could not be prepared. However, since this allegation had already been raised in the notice of opposition under Article 100(b) EPC, D15 did not carry more weight than the submissions already on file.

- D16 and D17 were filed to provide evidence that milling destroys the geopolymer composite. This issue could be relevant for assessing sufficiency, novelty and inventive step. However, since these objections had already been brought forward in the notice of opposition, D16 and D17 were not more relevant than the submissions already on file.

1.13 The board does not agree with the opposition division's assessment of prima face relevance.

1.14 In the notice of opposition, the opponent set out the technical reasons why it considered that the process described in the patent did not afford the claimed geopolymer composite. The opponent noted that the size of the particles of the starting materials used to prepare the tested products and that of the particles observed after milling was substantially identical. This showed that any composite possibly formed in the first steps of the process was destroyed during the subsequent milling step. This meant that the process afforded a simple mixture of geopolymer and athermanous material in powder form, not a "composite".

1.15 The notice of opposition also set out the reasons why the foams defined in claim 6 as granted could not be prepared. It was argued that these foams would have a thermal conductivity lower than that of air and that this was technically impossible.

1.16 Furthermore, it was explained why these issues were relevant in the examination of the requirements of sufficiency of disclosure, novelty and inventive step.

1.17 In its communication issued in preparation for the oral proceedings, the opposition division did not address the technical arguments set out in the notice of opposition. The submission on the size of the particles obtained after the milling step was ignored. The thermal conductivity of the materials making up the foam of claim 6 was not taken into account either. A declaration from a technical expert (D14) filed by the patent proprietor in reply to the notice of opposition addressing these issues was also not considered.

1.18 The opposition division expressed, however, the preliminary opinion that the opponent's objections were not supported by any evidence and therefore not convincing (see points 6.3 to 6.6 of the communication).

1.19 The opponent's letter dated 23 December 2020 and the annexed experimental reports D15 to D17 address the opposition division's preliminary opinion as well as the content of D14, filed by the patent proprietor. D15 to D17 describe tests determining the thermal conductivity, density and sedimentation properties of relevant materials and provide electron microscopy images of products allegedly according to the claimed invention. These documents aim to show that:

- in the case of D15, certain foams having the density specified in granted claim 6 could not be prepared and that other foams allegedly according to the invention performed worse than those of the closest prior art. Consequently, the claimed invention was not sufficiently disclosed and did not involve an inventive step over the prior art

- in the case of D16 and D17, geopolymer composites allegedly according to the invention could not be prepared following the teaching of the patent because the milling step destroyed the composite structure, affording a simple mixture of particles of geopolymer and athermanous material. Consequently, the claimed invention was not sufficiently disclosed

1.20 It is readily apparent that by filing D15 to D17, the opponent tried to overcome the opposition division's preliminary finding that the objections set out in the notice of opposition were not supported by evidence. The evidence provided clearly goes beyond the submissions in the notice of opposition.

1.21 Accordingly, the opposition division's finding that D15 to D17 are not prima facie relevant because the allegations that the claimed composites and foams cannot be obtained and the objections of lack of disclosure, novelty and inventive step "were already brought forward in the notice of opposition" is unreasonable. With this reasoning, the opposition division has de-facto not assessed the prima facie relevance of these documents.

1.22 If this approach were to be implemented, a party would lose the right to have any new evidence supporting an attack raised in the notice of opposition considered, irrespective of its prima facie relevance for the outcome of the proceedings.

1.23 The respondent has also argued that the decision not to admit D15 to D17 was correct because these documents were filed late, on the last date set by the opposition division under Rule 116 EPC to file submissions in preparation for the oral proceedings. Had these documents been admitted, the proprietor would not have been able to prepare a suitable response. As in case T 1271/13, this was contrary to a fair and expedient procedure. D15 to D17 should have been filed promptly in reply to the filing of D14, rather than shortly before the oral proceedings.

1.24 These arguments are not persuasive. The circumstances in T 1271/13 were different from those in the current case as an experimental report substantiating a new attack of lack of sufficiency of disclosure was filed one month before the oral proceedings and a corrected version of the report was filed only the day before the oral proceedings. In the case at hand, no new attack was raised with the new submissions, and the correct version of the documents was filed more than two months before the scheduled oral proceedings.

1.25 Furthermore, in the current case, it is apparent from the documents on file that the opponent requested that the oral proceedings before the opposition division be postponed so it could carry out its own experiments in reply to the experimental report D14 filed by the patent proprietor. This request, as well as a later request from the patent proprietor to postpone the oral proceedings for it to address D15 to D17, was not granted by the opposition division. Thus, the opposition division refused the parties' requests for more time to prepare their cases and held the oral proceedings on the scheduled date. During the proceedings, D15 to D17 were eventually not admitted.

1.26 The opposition division could have decided to admit these documents without depriving the parties of their right to fair proceedings. It would, first, have had to give to the proprietor the opportunity to provide its response. It could then have considered that the objections raised by the opponent were not well founded and decided to reject the opposition during the oral proceedings. Alternatively, it could have arrived at the conclusion that, in view of D15 to D17, its preliminary opinion was to be reversed. In this case, if requested by the proprietor, it would have had to postpone the oral proceedings to give proprietor the opportunity to prepare a proper response to the new submissions.

1.27 For these reasons, the board concludes that the opposition division, when deciding not to admit D15 to D17, exercised its discretion without taking into account the correct principles and in an unreasonable way.

1.28 D18 to D22 were filed by the proprietor in reply to the filing of D15 to D17 and were also not admitted into the opposition proceedings by the opposition division. It was not disputed that the opposition division's reasoning on the admissibility of these documents hinged solely on the decision not to admit D15 to D17. Therefore, the decision not to admit D18 to D22 was also made without taking into account the correct principles.

1.29 Finally, in view of these findings and considering that the case is to be remitted for further prosecution the board does not deem it expedient to rule on their admittance.

2. Remittal of the case to the opposition division

2.1 The board considers that since none of the aforementioned documents were taken into account by the opposition division, although they could be prima facie relevant for assessing whether the requirements of sufficiency of disclosure, novelty and inventive step, are fulfilled, the case is to be remitted to the opposition division for further prosecution (Article 111(1) EPC and Article 11 RPBA 2020).

2.2 The board agrees with the parties that it is appropriate to remit to the opposition division the task of determining, by applying the right principles, whether D15 to D17 and the other documents filed in cascade by the parties during the opposition and appeal proceedings should be admitted.

2.3 The respondent requested that since D20 was not admitted by the opposition division and no explicit request to have it admitted was made in appeal, the board should rule that this document not be considered in subsequent proceedings. The board does not agree. D20 is mentioned in D15 as a reference describing the method used for determining the thermal conductivity of the relevant compounds. Its potential relevance is also discussed in the appellant's statement of grounds of appeal. Therefore, it would not be appropriate for the board to decide a priori that D20 is not to be considered in the proceedings after remittal.