T 0199/22 19-04-2024

Summary of Facts and Submissions

I. The joint opponents lodged an appeal against the decision of the opposition division to reject the opposition filed against European patent No. EP 2 731 786.

II. The opposition had been filed against the patent as a whole on the basis of the grounds for opposition under Article 100(a) in conjunction with Article 54 EPC (lack of novelty) and Article 56 EPC (lack of inventive step).

III. Oral proceedings before the board were held on 19 April 2024.

IV. Requests

The appellants (opponents) requested that the decision under appeal be set aside and that the European patent No. 2 731 786 be revoked.

The respondent (patent proprietor) requested that the appeal be dismissed or, as an auxiliary measure, that the decision under appeal be set aside and that the patent be maintained as amended on the basis of the claims of any of the first to seventh auxiliary requests as filed with its reply to the statement of grounds of appeal.

V. The following document is of importance to this decision:

E3: US 2010/0273378 A1.

VI. Claim 1 as granted has the following wording (the feature references used by the parties are given in square brackets):

"[f1] A method for manufacturing a wind turbine rotor blade [f2] applying vacuum assisted resin transfer moulding, [f3a] comprising the step of fixating at least one layer of fibre material (2) to a surface of a mould (1) or to other layers (2) [f3b] by means of an adhesive [f3c] with functional groups, which can react with a thermoset resin, [f4a] characterised in at least partly dissolving the adhesive during wetting the adhesive with the thermoset resin [f4b] containing components acting as solvents for the adhesive."

VII. Auxiliary requests

Claim 1 of the first auxiliary request is amended by the following feature at the end of claim 1 as granted: "using an adhesive comprising an unsaturated base resin.".

Claim 1 of the second auxiliary request is amended by the following feature at the end of claim 1 as granted: "using an adhesive comprising an unsaturated base resin of oligomers containing unsaturated bonds.".

Claim 1 of the third auxiliary request is amended by the following feature at the end of claim 1 as granted: "using an adhesive comprising an unsaturated base resin and a base resin to which at least one other component, namely at least one reaction inhibitor and/or reaction catalyst and/or softener and/or other polymeric composition than the base resin, was added.".

Claim 1 of the fourth auxiliary request is based on claim 1 as granted except that the first alternative of feature f3a "to a surface of a mould (1)" has been deleted.

Claim 1 of the fifth and sixth auxiliary requests is based on claim 1 of the fourth auxiliary request and adds the amendments of the first and second auxiliary requests respectively.

Claim 1 of the seventh auxiliary request reads as follows:

"A method for manufacturing a wind turbine rotor blade applying vacuum assisted resin transfer moulding, comprising the step of fixating at least one layer of fibre material (2) to other layers (2) by means of an adhesive with functional groups, which can react with a thermoset resin, wherein at least partly dissolving the adhesive during wetting the adhesive with a thermoset resin containing components acting as solvents for the adhesive, using an adhesive comprising an unsaturated base resin and a base resin to which at least one other component, namely at least one reaction inhibitor and/or softener, was added."

VIII. The parties' submissions can be summarised as follows.

(a) Patent as granted - novelty of subject-matter of claim 1

(i) Appellants

Document E3 related to a semifinished textile product with a tacky surface (see document E3, paragraph [0008]). Paragraph [0025] of document E3 stated that semifinished textile products were particularly suitable for the production of fibre-reinforced components in a vacuum infusion and resin injection process. Furthermore, paragraph [0027] and claim 14 of document E3 disclosed that the fibre-reinforced component might be used for the manufacture of rotor blades for a wind turbine generator. Accordingly, document E3 directly and unambiguously disclosed features f1 and f2.

According to document E3, the semifinished textile product had good tackiness, and according to the examples of document E3 this was achieved by applying an adhesive to unidirectional layers of glass fibre. Consequently, it was directly and unambiguously disclosed that the semifinished textile product had the property of fixating a layer of glass fibres by means of an adhesive to either a mould or other layers. In particular, paragraph [0025] of document E3 described a layup in a mould and Example 1 of document E3 described stacked layers of unidirectional glass fibres. Accordingly, features f3a and f3b were also anticipated by document E3.

The adhesive and its preparation were disclosed in paragraphs [0009] to [0014] of document E3. The partial ester used in the adhesive was, for instance, produced by using epoxidized novolaks, comprising epoxy groups and hence functional groups according to feature f3c. An adhesive with functional groups which reacted with a thermoset resin was also disclosed in paragraph [0023] of document E3.

Paragraph [0018] of document E3 referred to the use of the semifinished textile product with an epoxy resin according to the prior art and emphasised the excellent mechanical properties and compatibility of the epoxy resin with the adhesive. One example of such an epoxy resin was an epoxidized novolak. Since according to paragraph [0020] and claim 9 of document E3 the "adhesive is capable of being swelled and/or partially dissolved in reaction resin mixtures containing epoxy resins", features f4a and f4b were inherently disclosed. Moreover, features f4a and f4b were redundant. Since paragraph [0023] of the patent disclosed that "the same or similar oligomers in the adhesive and in the resin can be used", it was irrelevant whether the thermoset resin dissolved the adhesive or vice versa.

Consequently, all the features of claim 1 as granted were disclosed in document E3.

Contrary to the opposition division's opinion, feature f1 was disclosed in combination with the remaining features f2 to f4b. In this regard, it was established case law (see Case Law of the Boards of Appeal of the European Patent Office, 10th edition, July 2022, "Case Law", I.C.4.1) that the technical disclosure in a prior-art document had to be considered as a whole. Thus the person skilled in the art would understand that the product, for instance the rotor blade for a wind turbine generator, could be used in a vacuum assisted resin transfer moulding (VARTM) process, which was the process most commonly used for the manufacture of a wind turbine rotor blade. At least, there was an implicit disclosure of a wind turbine rotor blade produced by VARTM. This was in accordance with established case law (see Case Law, I.C.4.3), and was especially reflected in decision T 1523/07. According to that decision, an "implicit disclosure" was to be understood as a disclosure which any person skilled in the art would objectively consider to be necessarily implied in the explicit content. Moreover, resin infusion had been known for many years. The person skilled in the art was familiar with both possibilities, i.e. RTM (resin transfer moulding) in an open-mould arrangement and VARTM in a closed-mould arrangement. Since VARTM was the better choice due to the associated avoidance of volatile organic compounds, VARTM would have been the preferred option. A preferred option did not amount to a selection.

Thus the subject-matter of claim 1 was not novel over document E3.

(ii) Respondent

Document E3 was concerned with the manufacture of semifinished textile products with a tacky surface (see document E3, paragraph [0008]), i.e. the final products of document E3 had a tacky surface.

Although paragraph [0027] of document E3 disclosed that the semifinished textile products were suitable for the manufacture of wind turbine rotor blades, it did not disclose a method for manufacturing such. The same applied to claim 14 of document E3. Paragraph [0025] of document E3 merely disclosed that the semifinished textile products were used in VARTM processes, but not that a wind turbine rotor blade was manufactured by a VARTM method. Thus there was no direct and unambiguous disclosure of features f1 and f2 in combination.

Paragraphs [0012] to [0016] of document E3 referred to the adhesive and its production, before its application to the textile material. Paragraphs [0020] and [0023] and claim 9 of document E3, which were cited in support of the disclosure of features f3c and f4b, referred to the semifinished textile products, thereby not mentioning the final product or a wind turbine rotor blade. The disclosure of the adhesive "capable of partial solution in reaction resin mixtures containing epoxy resins" was not disclosed in the context of a VARTM process with a thermosetting resin.

The fact that the epoxy resin and adhesive were compatible, as disclosed in paragraph [0018] of document E3, could not be equated with a resin at least partially dissolving the adhesive as claimed in feature f4a. Contrary to the appellants' allegations, features f4a and f4b were not redundant, since feature f4b required that the resin - and not the adhesive - contain a solvent.

All in all, document E3 did not disclose features f1 and f3a to f4b in combination with a VARTM process. Therefore the subject-matter of claim 1 as granted was new over document E3.

(b) Patent as granted - inventive step of subject-matter of claim 1

(i) Appellants

The subject-matter of claim 1 was not inventive over document E3 alone. Document E3 disclosed all the features of claim 1 as granted except for features f1 and f2 in combination. It was established case law that a merely arbitrary choice from a host of possible solutions could not be considered inventive if not justified by a hitherto unknown technical effect that distinguished the claimed solution from the other solutions (see Case Law, I.D.9.21.9a)). In the case at hand, the person skilled in the art had a choice between an RTM process and a VARTM process (see document E3, paragraph [0025]). Both processes had particular advantages and disadvantages, which were well-known to the person skilled in the art.

(ii) Respondent

VARTM is nowadays the most common - and indeed the preferred - method, but this was not the case in 2012, the filing year of the patent. Additionally, document E3 was not an appropriate starting point for evaluating inventive step of the subject-matter of granted claim 1, since said document was not concerned with the manufacture of a wind turbine rotor blade.

(c) Admittance of first to seventh auxiliary requests

(i) Appellants

The first to seventh auxiliary requests should not be admitted, in accordance with Article 12(5) RPBA, since the respondent had not provided a substantiated analysis with regard to patentability (Article 12(3) RPBA).

(ii) Respondent

The first to seventh auxiliary requests should be admitted. The opposition division's decision did not give rise to further elaborations.

(d) First to seventh auxiliary requests - inventive step of subject-matter of claim 1

(i) Appellants

Paragraphs [0009] and [0012] of document E3 disclosed a partial ester. A partial ester, e.g. produced by epoxidized novolaks (see document E3, paragraph [0013]), had double bonds. Since an unsaturated base resin was a resin having double or triple bonds, this feature was disclosed in document E3. The same applied to an unsaturated base resin of oligomers containing unsaturated bonds, which was redundant and merely reflected the definition of an unsaturated base resin. Oligomers were formed by polymerisation of monomers containing double bonds, e.g. epoxidized novolaks, which were disclosed as an example in document E3. Thus there was no further distinguishing feature in claim 1 of the first and second auxiliary requests. With regard to claim 1 of the third auxiliary request, paragraphs [0015] and [0016] of document E3 mentioned an "initiator", which was just another word for a catalyst. Further reference was made to the catalyst MEKP and to the co-catalyst of Example 2 of document E3. Concerning claim 1 of the fourth to sixth auxiliary requests, the alternative of feature f3a of fixating at least one layer of fibre material to other layers was also disclosed in document E3 - see, for instance, paragraphs [0002], [0021] and [0025]. Claim 1 of the seventh auxiliary request limited the other components of the adhesive to a reaction inhibitor and softeners. These additives belonged to the toolkit of a chemist and, as such, could not contribute to inventive step.

The subject-matter of claim 1 of each of the first to seventh auxiliary requests was not inventive over document E3.

(ii) Respondent

The subject-matter of claim 1 of each of the first to seventh auxiliary requests was not obvious in view of document E3. With regard to claim 1 of the first and second auxiliary requests, it was not derivable from paragraph [0009] of document E3 that the adhesive itself comprised an unsaturated base resin and that the reaction product described in paragraphs [0009] to [0012] itself comprised oligomers having unsaturated bonds. Concerning the catalyst of claim 1 of the third auxiliary request, the initiator in paragraphs [0015] and [0016] of document E3 was not specified. Concerning the fourth to sixth auxiliary requests, paragraph [0021] of document E3 was merely referring to the textile layers of the semifinished textile product. Paragraph [0025] of document E3 only described the positioning of the semifinished textile products in the mould. In claim 1 of the seventh auxiliary request the alternatives "reaction catalyst" and "other polymeric composition than the base resin" have been deleted.