T 0623/20 (Chabazite zeolite/Tosoh) 19-10-2022

1. Consideration of documents, Article 12(6) RPBA 2020

1.1 The experimental report E35 was filed by respondent 1 with the reply to appeal. It was intended to demonstrate that it was not possible to reproduce the starting material (amorphous aluminosilicate material (AAM) having a SiO2:Al2O3 molar ratio of 28), prepared in the first stage of Example 3 of the impugned patent.

1.2 However, this experimental report, and E34 referenced in E35, should have been filed before the opposition division. The respondent raised the objection that Example 3 could not be identically reproduced during opposition proceedings (point 3.1.(iv) of the impugned decision) and they should then also have filed any evidence in support of this objection. According to the established case law of the boards of appeal, each of the parties to the proceedings bears the burden of proof for the facts it alleges (Case Law of the Boards of Appeal of the EPO, 10th edition, 2022, I.C.3.5.1). There is no apparent reason why the evidence was not filed before the opposition division and was only filed at the appeal stage. Therefore, the board cannot recognise that the circumstances of the appeal case would justify the admittance of E34 and E35.

1.3 E34 and E35 are therefore not taken into account (Article 12(6) RPBA 2020).

1.4 E33 merely reflects common general knowledge which, as such, was not contested.

2. Sufficiency of disclosure, Article 100(b) EPC

2.1 Claim 1 specifies that the chabazite-type zeolite has an average crystal particle diameter of 1.5 mym or more, wherein the average crystal particle diameter is measured by scanning electron microscopy (SEM) by arbitrarily selecting 50 crystal particle images from one or more SEM photographs taken at 5,000-fold magnifications, measuring the 50 crystal particle diameters thereof, and calculating a weighted average thereof.

2.2 A non-spherical crystal particle has no diameter in a strict sense. Instructions are thus missing on how exactly the "diameter" is identified and how the weighted average is calculated, i.e. how the weighting is performed.

Nevertheless, there is no reason why the skilled person who is familiar with measuring particle sizes of a zeolite using electron microscopy (E7, paragraph [0047]; E27, paragraph [0016] and E28, page 9, point (5)) would be unable to identify a suitable length, for instance the face side length, of a crystal particle, and measure it.

The result depends to some extent on the type of length measured, as illustrated in E31, in which a value of 1.6 mym was obtained for one edge, a value of 1.7 mym for the other edge and a value of 2.05 mym for the diagonal, each of these being the arithmetic mean of four crystals; however, such deviations of the results depending on which length is chosen as the "diameter" concern the question of clarity (Article 84 EPC) and not sufficiency of disclosure (see also T 593/09, point 4.1.4. of the Reasons), especially in the case of an open-ended range for the parameter.

The reference to a weighted average without any further indication adds to possible deviations of the results, in that they may depend on the chosen weighting (which might for instance be based on crystal particle area); however, this would not have prevented the skilled person from conducting the measurement. This is even more so as the patent explicitly describes that a particle diameter was obtained by averaging the diameters of the particles (paragraph [0035]), which is understood as calculating the number-based average. There is no reason why this could not be regarded as a number-weighted average in the context of the present patent. The explanations in E33 do not contradict considering the arithmetic mean to be a special case of a weighted mean (E33 (second paragraph), "if all the weights are equal, then the weighted mean is the same as the arithmetic mean").

2.3 The claim instructs the skilled person to "arbitrarily" select 50 crystal particle images. The skilled person would understand this as performing a random sampling operation, considering that an average value is then to be determined. No reason is apparent as to why the skilled person would be unable to do so, or why this would involve an undue burden. According to the claim, 50 crystal particle images are to be selected. While the result may depend on which specific crystal particle images are chosen, i.e. there may be a margin of error, its extent is not known. There is no proof from the respondents' side that the results of such measurements would consequently be unreliable and unreproducible, as would be the case if, for instance, the margin of error was so large that the result would have no technical significance.

2.4 In light of the above, the issues raised merely concern possible uncertainties linked to determining the average crystal particle diameter, in the sense of a possibly large error margin or a large spread of the results. Respondent 1 estimated the error margin as being 20-35% or even greater. In this case, the existence of a, possibly large, error margin is only relevant near the limits of the claim, when assessing whether an average crystal particle diameter is within the specified open-ended range of 1.5 mym or more, or outside this range. It thus concerns the question of whether the limits of protection conferred by the claim are clear, this being a requirement of Article 84 EPC; however, there is no indication that the ambiguity would permeate the whole claim (see T 608/07, point 2.5.2 of the Reasons). By contrast, the patent in suit shows that comparative zeolites can have much smaller average crystal particle diameters of 0.18 mym to 0.48 mym (Table 3, Comparative zeolites). In particular, there is no evidence that the possible uncertainties would be such that they would deprive the parameter relating to the average crystal particle diameter of any technical meaning and that, as a consequence of them, the skilled person would be unable to carry out the invention.

2.5 This case is not comparable to any of the cases cited by respondent 1. In T 61/14 neither the patent nor the prior art provided information on how to measure the parameter under consideration (points 5.8 and 5.9 of the Reasons), and therefore the underlying issue was not merely the possible uncertainty of the result at the limit of the claim. Neither of T 544/12 and T 1610/08 relates to the possible uncertainty of a parameter at the lower end point. In T 544/12 it was necessary to identify those compounds out of the host of compounds defined by the structural feature(s) in the claim which also fulfilled the claimed functional requirement(s) (point 4.2 of the Reasons). T 1610/08 dealt with the issue of whether a detailed description of at least one way of carrying out the invention was given (point 2, seventh paragraph, of the Reasons).

Furthermore, by contrast with T 256/87 (in which sufficiency was recognised anyway), it was the predominant opinion in later decisions that the definition of a 'forbidden area' of a claim should not be considered as a matter related to Article 83 EPC but rather to Article 84 EPC (see Case Law of the Boards of Appeal of the EPO, 10th edition, 2022 II.C.6.6.4 or, for example, T 2290/12, point 3.1 of the Reasons).

2.6 Respondent 1 also argued that the skilled person would have been unable to carry out the required zeolite synthesis because they would not know how to obtain an amorphous aluminium silicate gel having the necessary SAR (silica/alumina ratio).

E35 (see point 1.) is not taken into consideration. It has not been demonstrated that the skilled person would be unable to provide a CHA zeolite having the specified SAR. The patent in suit mentions several prior-art documents which describe CHA zeolites having a broad range of SiO2:Al2O3 ratios (paragraphs [0003]-[0005]; Comparative Example 1 reproducing the prior art). Furthermore, preparing an amorphous aluminosilicate gel as a starting material as shown in Example 3 is not the only method exemplified in the patent in suit; see, for instance, Example 2.

Even if the experimental protocols provided in the patent might not include all the necessary details for an identical reproduction, there is no evidence that the skilled person would have been unable to steer the zeolite synthesis towards the desired large average crystal particle diameter, based on the teaching provided in the patent in suit, and to thus obtain achabazite-type zeolite according to claim 1.

As follows from the considerations regarding the measurement of the average crystal particle diameter set out above (points 2.2 to 2.4), there is also no need to identically reproduce a given example as a reference point to assign a meaning to this parameter.

2.7 In conclusion, the requirement of sufficiency of disclosure is met.

2.8 The same considerations apply to process claim 2.

3. Alleged violation of the appellant's right to be heard, Article 113(1) EPC

3.1 The appellant argued that the opposition division changed its chain of reasoning, in that the reasoning in the written decision differed from the brief summary given by the chairwoman during the oral proceedings.

However, the actual decision given orally did not differ from that given in writing. The minutes of the oral proceedings indicated that a brief summary of the reasons was given by the chairwoman, but do not report this summary (page 5, third line from the bottom). In any case, it is normal practice that the reasoning is communicated in writing. The chairwoman was not obliged to provide any reasoning during the oral proceedings, let alone the full reasoning. A brief summary naturally cannot include all the aspects, and therefore the appellant could not have been surprised that a further aspect, which was allegedly not mentioned in the brief summary but discussed during the oral proceedings, was relied on in the written decision. Furthermore, the fact that one aspect had allegedly been mentioned orally that was not relied on in the decision is to the appellant's favour. In particular, there is no indication that the alleged differences between the brief summary and the written decision had any bearing on the final outcome of the oral proceedings, in that they might have influenced the appellant's line of defence or procedural choices during the oral proceedings.

3.2 The minutes of the oral proceedings before the opposition division demonstrate that all the reasons had been discussed with the parties, including the question of whether Example 3 could be reworked, on which the patent proprietor had an opportunity to comment (see page 2, third paragraph; page 3, penultimate paragraph - page 4, first paragraph; page 4, fifth paragraph of the minutes).

3.3 The board therefore sees no violation of the appellant's right to be heard.

4. Remittal, Article 11 RPBA 2020

4.1 The grounds for opposition relating to novelty and inventive step have not yet been dealt with. In view of the primary object of the appeal proceedings to review the decision under appeal in a judicial manner (Article 12(2) RPBA 2020), the circumstances of this case, in which the opposition division has not decided on these grounds for opposition, qualify as a special reason for remittal under Article 11 RPBA 2020. The case is therefore to be remitted to the opposition division for further prosecution (Article 111(1) EPC).