T 2604/22 (Dispersion comprising nanoparticles/STORA ENSO) 02-12-2024

1. Right to be heard (Article 113(1) EPC)

1.1 The appellant argued that the decision under appeal did not take into consideration its argument that Sample 9 of D1 did not disclose the addition of nanoparticles to a slurry of cellulose fibres. The opposition division's decision did not "in any way mention or comment on the Proprietor's arguments concerning Sample 9 of D1 or why the Main request would or would not fulfil the requirement of novelty over Sample 9 of D1 in view of the Proprietor's arguments."

1.2 The proprietor (now appellant) filed a corresponding request for a correction of the minutes of the oral proceedings before the opposition division. The opposition division refused this request since it considered this argument "not [...] essential for taking the decision" under appeal (see the opposition division's communication dated 25 November 2022).

The board notes that the opposition division did not contest that the aforementioned argument was presented by the patent proprietor during the oral proceedings. Hence, the board has no reason to doubt that this argument was effectively part of the patent proprietor's case before the opposition division.

1.3 It is true that the decision under appeal does not set out the reasons why the aforementioned argument, which was presented in relation to the main request, was not considered convincing. The board opines that this argument is indeed relevant for the assessment of novelty of claim 1 of the main request. It is thus concluded that the appellant's right to be heard has been infringed.

An infringement of the right to be heard by a department of first instance has to be acknowledged if a central argument has been heard by the deciding body but has not been considered and addressed in substance - either explicitly or implicitly - in its decision (see Case Law of the Boards of Appeal, 10th edition, 2022, III.B.2.4.2). To meet the requirement of the right to be heard, a decision that is open to appeal has to contain at least some reasoning on the crucial points of dispute in order to give the party concerned a fair idea of why its submissions were not considered convincing. In relation to the assessment of novelty of claim 1 of the main request, however, such a reasoning was not provided either explicitly or implicitly in the decision under appeal.

1.4 In order to be able to assert that there has been a substantial or fundamental procedural violation, however, a causal link between the procedural violation and the outcome of the case needs to be established. As held in decision T 49/13, an error that would not have led to a different outcome of the proceedings cannot be regarded as a substantial procedural violation (see Reasons 9; cf. also decision T 2249/08, Reasons 6.7, and decision T 1340/10, Reasons 1.6).

1.5 In the case at hand, the main request would also have fallen in view of the finding of a lack of novelty in respect of claim 9 over both documents D23 and D24.

1.6 In auxiliary request 1, however, claim 9 has been deleted. Auxiliary request 1 was not held allowable by the opposition division only because claim 1 thereof was identical to that of the main request which, in turn, had been held to lack novelty over D1. The procedural violation and the resulting assessment of novelty of claim 1 as granted in view of D1 are thus decisive for the decision taken by the opposition division to refuse auxiliary request 1. Moreover, not taking into account the aforementioned argument could also have had a bearing on the assessment of inventive step. In this regard, the appellant stated that "the Opposition Division also made an incorrect assessment of inventive step since the analysis of the distinguishing technical features was not correct."

1.7 Consequently, the board concludes that the opposition division committed a substantial procedural violation causal to the appeal, and therefore the appealed decision must be set aside and the appeal fee reimbursed (Rule 103(1)(a) EPC), see Case Law of the Boards of Appeal, 10th edition, 2022, V.A.11.7.1.

1.8 As the procedural violation does not affect claim 9 of the main request, the board will assess the novelty of the subject-matter of this claim in the following.

2. Novelty (Article 100(a) EPC in conjunction with Article 54 EPC) - main request

2.1 Claim 9

2.1.1 The appellant argues that the process of claim 1 was distinguished from that disclosed in D23 and D24 by the presence of nanoparticles during the mechanical disintegration step.

2.1.2 However, this argument is not sufficient to establish the novelty of product-by-process claim 9 of the patent. In fact, the aqueous slurries comprising microfibrillated cellulose (MFC) described in both D23 and D24 also comprise, like the patent, very fine cellulosic fibres having a large open surface, i.e. microfibrillated cellulose within the meaning of claim 1, onto which nanoparticles can be adsorbed. Moreover, these documents describe such nanoparticles and disclose, at least implicitly, that these nanoparticles are indeed adsorbed onto such cellulosic fibres.

2.1.3 In this regard, D23 expressly mentions that a filler material is efficiently taken into the inside of a loose MFC aggregate in aqueous MFC dispersions under appropriate dispersion (see paragraph [0036]).

2.1.4 Example 6 of D23 discloses the mixing of fumed silica "Aerosil 90G" having a minor axis diameter of 20 nm and a ratio of major axis diameter to minor axis diameter of 1:1, i.e. nanoparticles within the meaning of claim 1 of the patent.

2.1.5 Likewise, paragraph [0075] of D23 sets out that it is preferred that the filler used is non-aggregated. Paragraph [0076] of D23 discloses that the MFC and the filler material should be evenly distributed. To this end, a high-speed disperser or high pressure homogeniser can be used.

2.1.6 Moreover, claim 1 does not call for a specific quantity of nanoparticles absorbed to the MFC fibres.

2.1.7 In view of these findings, the board concludes that it cannot be established whether or not a dispersion as featured in Example 6 of D23 has been prepared by a process as called for in claim 1 or in accordance with the procedure described in Example 6. In the absence of a demonstrated structural difference that could be associated with the process feature in question, the dispersion prepared in Example 6 is considered to anticipate the dispersions claimed in claim 9 as granted.

2.1.8 Similar considerations apply in respect of the disclosure of Examples 1 to 5 of D24. First of all, nanocellulose is an MFC within the meaning of the patent, see paragraph [0028]. It is unlikely that the dispersions of nanocellulose that are contacted with nanoparticles formed therein would contain significant amounts of aggregated nanoparticles. D24 also sets out that no sedimentation of the formed dispersions was observed. The dispersions of D24 are thus stable dispersions, as described in the example of the patent in suit. D24 also divulges that nanocellulose can be used as a dispersant and stabiliser agent (see paragraph [0004] of D24/D24a). This requires, however, the adsorption of the dispersant to the dispersed compound (filler particles). Thus, the products obtained in Examples 1 to 5 of D24 cannot be discerned from corresponding dispersions obtained using the process of claim 1 as granted.

2.1.9 As regards the burden of proof in relation to the novelty of products characterised by process features, the appellant presented essentially two arguments. First, it was inequitable to allow the opponent to produce comparative data less than two months prior to the oral proceedings before the opposition division. In this regard, the board observes that the comparative data provided by the opponent have not been taken into account in the decision under appeal. Second, the appellant referred to T 564/02. However, this decision does not support the appellant's case because it held that the subject-matter of the product-by-process claim under examination could not be distinguished from a product obtained by the process of the prior art (see Reasons 3.5 and 3.7) and in fact confirms established jurisprudence as to the assessment of novelty of "product-by-process claims" (see Reasons 3.4). In this regard, the burden of proof to demonstrate novelty is incumbent upon the proprietor, which has failed to do so (see also T 32/17, Reasons 15).

2.1.10 Therefore, and in line with the findings in the decision under appeal, the subject-matter of claim 9 as granted is not considered novel in view of documents D23 and D24.

3. Remittal

As set out above, the opposition division's assessment of auxiliary request 1 is tainted with a substantial procedural violation. In these circumstances, the board considers it appropriate to remit the case to the opposition division for further prosecution (Article 111(1) EPC; Article 11, second sentence, RPBA).