T 0020/17 13-02-2020

I. The appeal lies against the decision of the opposition division posted on 8 November 2016 revoking European patent number 2 195 374.

II. The patent was granted with a set of 14 claims, whereby claims 1 and 2 read as follows:

"1. Process for preparing a heat-processable thermally conductive polymer composition according to claim 6, comprising steps of

- melt mixing of a thermoplastic polymer, a thermally conductive filler and optionally one or more further components, thereby forming a mixed homogenous melt, and

- cooling the mixed homogenous melt thereby obtaining the polymer composition

in a solid form,

wherein thermoplastic polymer is selected from polyamides, polyesters, polyarylene sulfides, polyarylene oxides, polysulfones, polyarylates, polyimides, poly(ether ketone)s, polyetherimides, polycarbonates, copolymers of said polymers among each other and/or with other polymers, including thermoplastic elastomers, and mixtures of said polymers and copolymers, and

wherein the thermally conductive filler comprises graphite powder comprising platelets having a thickness of less than 500 nm, and wherein the graphite powder has a BET specific surface area, determined by the method according to ASTM D3037, of at least 10 m**(2)/g and a particle size distribution characterized by a D(v, 0.9) of at least 50 µm as determined by laser diffraction.

2. Process according to claim 1, wherein the graphite powder in the form of platelets having a thickness of less than 500 nm is present in an amount of 5 to 40 % by weight, relative to the total weight of the polymer composition."

Claims 3-5 were dependent on claim 1.

Claim 6 was an independent claim, directed to a polymer composition and read as follows:

"Heat-processable thermally conductive polymer composition comprising

(a) 30 to 95 % by weight of a thermoplastic polymer selected from polyamides, polyesters, polyarylene sulfides, polyarylene oxides, polysulfones, polyarylates, polyimides, poly(ether ketone)s, polyetherimides, polycarbonates, copolymers of said polymers among each other and/or with other polymers, including thermoplastic elastomers, and mixtures of said polymers and copolymers; and

(b) 5 to 40 % by weight of a graphite powder in the form of platelets having a thickness of less than 500 nm and wherein the graphite powder has a BET specific surface area, determined by the method according to ASTM D3037, of at least 10 m**(2)/g and a particle size distribution characterized by a D(v, 0.9) of at least 50 µm as determined by laser diffraction;

wherein the weight percentages are relative to the total weight of the polymer composition."

Claims 7-13 were directed to preferred embodiments of the composition of claim 6.

Claim 14 was directed to the use of a composition as defined in claims 6-13.

III. Three notices of opposition against the patent were filed, invoking the grounds pursuant to Article 100(a) EPC (lack of novelty, lack of inventive step), Article 100(b) EPC and Article 100(c) EPC.

The following documents, inter alia were cited in support of the oppositions:

D1: US-A-6 685 855

D2: US 2002/0054995 A1

D3: KR 100705906 B1 (D3a: translation of claims and Table 1; D3b: complete translation)

D4: KR 100705905 B1 (D4a: translation of claims and Table 1; D4b complete translation)

D5: US 2003/0220432 A1

D8: TIMCAL Graphite & Carbon, "TIMREX**(®) Graphite ENSACO**(TM) Carbon Black Carbon additives for polymer compounds", 2004.

During the course of the opposition proceedings the patent proprietor submitted two experimental reports, designated D17 and D20 with letters of 7 January 2016 and 26 August 2016 respectively. Opponent 1 submitted inter alia with letter of 26 August 2016 an experimental report designated D21.

IV. The decision was based on amended sets of claims forming a main and four auxiliary requests.

Claim 1 of the main request differed from claim 1 as granted by specifying that the thermally conductive filler "comprises a graphite powder in the form of platelets" according to part of claim 2. Claim 5, directed to a composition, was unamended compared to the corresponding claim 6 as granted.

The wording of the auxiliary requests underlying the decision is not relevant for the present decision.

D20 was admitted to the procedure. D17 was discussed in the decision together with D20, although no explicit finding with respect to admittance of D17 was given. Document D19 was not admitted to the procedure, as it would only become relevant if D8 were considered to represent the closest prior art, which was not the case.

The main request was found not to meet the requirements of Article 56 EPC. Any of D1, D2 or D5 could be considered as representing the closest prior art. These disclosed thermally conductive plastic compositions comprising one of the polymers as defined in claim 1 and an amount of graphite platelets in the claimed range.

The subject-matter claimed was distinguished from the closest prior art by the properties of the graphite, in particular the defined combination of BET surface area and particle size distribution.

The graphite of D2 satisfied the claimed requirements in respect of BET surface area. The value of particle size distribution - D(v, 0.9) was however not disclosed. Thus the examples in the patent could not be considered as representative of the teaching of D2. Nevertheless it was accepted that the data of the patent showed that the claimed compositions exhibited improved thermal conductivity for a given filler loading. The evidence of the patent indicated in particular improvements as compared to a graphite TIMREX**(®) KS44 which, as stated in the patent and shown in D8, had a particle size distribution in the required range but a BET specific surface area of 9 m**(2)/g and hence below that required.

Experimental reports D17 and D20 showed that the claimed graphites did not impair the processability of the compositions. However the patent contained no data which would provide a basis for reformulating the problem on this basis. The graphite used in D17 and D20 - "EcoPhit" - had a particle size far larger than the lower limit of the claim and differed greatly from that of the closest prior art - KS44. Thus the proffered comparison was not a fair one and not suitable to demonstrate any technical effect over the whole scope of the claims.

Although the patent proprietor had argued that improvements in the mechanical properties arose, there was no evidence for any such improvement at the same filler loading.

Thus the objective problem could be formulated only as the provision of thermoplastic compositions of improved thermal conductivity at the same loading of filler.

The problem was solved by the use of a thermally conductive graphite filler as defined in the claims, for example TIMREX**(®) BNB90.

This material was however known as the filler of choice in thermally conductive compositions and was known to be clearly better than the KS grades at a given loading. This was shown by D8 on page 22. This particular filler as well as similar fillers of the same class had been used as thermally conductive fillers in polypropylene (D8, page 22), ABS (D3, D4) and other polymers. Thus it was obvious to use said class of filler with other types of polymers known in the art, and as taught inter alia by D8.

Accordingly an inventive step was denied.

The auxiliary requests, insofar as held admissible, were also held not to meet the requirements of the EPC. The details of these findings are not relevant for the present decision.

Accordingly the patent was revoked.

V. The patent proprietor (appellant) filed an appeal against the decision.

In the statement of grounds of appeal the main request as considered by the opposition division was maintained and a first auxiliary request, in claim 1 of which the thermoplastic polymer was restricted to various polyamides was submitted.

A further experimental report was provided ("Enclosures 5.1-5.3").

VI. The opponents (respondents) replied to the appeal.

Objections to admittance of the auxiliary request and of the newly filed experimental data were raised. It was also disputed that the opposition division had correctly exercised its discretion in admitting D17 and D20 to the procedure.

Objections in respect of lack of sufficiency of disclosure and lack of inventive step were pursued in respect of the main request.

For the auxiliary request objections pursuant to added subject-matter, clarity and inventive step were raised.

VII. The Board issued a summons to oral proceedings and a communication.

VIII. With a letter of 3 December 2019, the appellant filed two "Enclosures" - numbered 3 and 4 each containing a "Declaration" and three further auxiliary requests designated auxiliary requests 1-3 were provided. The main request and the previously filed auxiliary request, which was redesignated auxiliary request 4, were filed again.

Claims 1 and 5 of auxiliary request 1 differed from claims 1 and 5 of the main request by restricting the polymer to polyamides and polycarbonates.

Claims 1 and 5 of auxiliary request 2 differed from auxiliary request 1 by specifying only polyamides.

Claims 1 and 5 of auxiliary request 3 were restricted to the same polyamides as listed in auxiliary request 1 as submitted with the statement of grounds of appeal (now auxiliary request 4) but additionally specified that these were "semicrystalline".

IX. A further document - designated A1 - was submitted by opponent 2 with letter of 18 December 2019.

X. Oral proceedings were held before the Board on 13 February 2020.

In the course of the oral proceedings the appellant submitted a further set of claims as auxiliary request 5 in which claims 1 and 5 restricted the polyamide to a single species, namely PA 4,6. Otherwise the claims were as claim 1 of the main request with consequential deletion of claim 8 (directed to polyamides and hence redundant).

XI. The arguments of the appellant, insofar as relevant for the decision, can be summarised as follows:

(a) Admittance of documents

D17, D20: There was no legal basis for excluding these documents from the procedure. The opposition division had correctly exercised its discretion in admitting said documents.

D19: there was no legal reason for admitting this, consistently with the findings of the decision under appeal.

Enclosures 5.1-5.3 provided with the statement of grounds of appeal: these contained comparative examples and were a reaction to the - unexpected - findings of the opposition division in respect of the non-suitability of the data then on file to support the position on inventive step.

Enclosures 3 and 4: these were relevant to the question of inventive step since unlike other submissions of the appellant, they contained data relating to polycarbonates, and could be seen as a response to D21 of opponent 1 which had been admitted to the proceedings by the opposition division. These declarations filled in gaps in the data thus far submitted and were necessary to defend the case in particular should D8 be regarded as the closest prior art.

(b) Main request - inventive step - claim 5

D2 did not address the same problem as the patent in suit and hence was not the closest prior art.

The subject-matter as claimed was distinguished from the disclosure of D2 by the nature of the graphite.

The problem with respect to D2 was the provision of thermally conductive polymer compositions with improved thermal conductivity and good - not necessarily improved - processability, as expressed by spiral flow, whilst maintaining the mechanical properties. This was set out in paragraphs [0005], [0036] and [0037] of the patent. The data of Enclosure 5 as well as those of D20 showed that this problem had been solved.

Regarding the admissibility of invoking maintenance of good processability for formulating the technical problem the case law, for example T 39/93, T 246/91 and T 386/89, permitted the problem to be (re)formulated on the basis of any technical effect mentioned in the application. Thus it was permissible to reformulate the problem taking into account maintenance of good processability on the basis of the disclosure of the melt flow.

D2 was silent with respect to this problem since melt flow and thermal conductivity were not addressed. Hence there would have been no reason to consult the document in view of the problem underlying the patent in suit and, even if the document had nevertheless been considered, no pointers to the claimed subject-matter would be found. In particular the specific combination of properties of the graphite in terms of particle size and BET surface area was not disclosed in or derivable from D2. The same considerations applied to D1 and D5. Taking into account the teachings of D8 would not have led to a different conclusion since D8 was silent with respect to the problem underlying the patent, being restricted to considerations of thermal conductivity. D8 provided no motivation to make the necessary modifications to the compositions of D2 in the expectation of solving the problem underlying the patent in suit. Even if nevertheless the necessary adjustments were to be made to arrive at the subject-matter claimed, D8 provided no indication that these would be expected to lead to the desired outcome for solving the problem. Furthermore D8 showed that the graphites as defined in the operative claims were unsuitable for use in thermoplastic polycarbonates and polyesters and also taught that for thermoplastics small particle sizes were required. The particle size as defined in the claim was higher than the range identified as suitable in D8. Thus D8 taught away from this aspect of the claimed invention.

(c) Auxiliary requests 1 and 2 - inventive step

The subject-matter had been restricted compared to the main request to emphasise the inventive features. The same considerations applied as for the main request.

(d) Auxiliary requests 3 and 4 - inventive step

These represented further limitations of the main request and were inventive for the same reasons.

Auxiliary request 3 contained additional features compared to auxiliary request 4, which had been introduced in order to address a potential objection in respect of added subject-matter in respect of auxiliary request 4.

(e) Auxiliary request 5 - admittance

The appellant found it unforeseeable and surprising that none of the requests, in particular auxiliary request 3, had not been found to meet the requirements of inventive step. The appellant was somewhat uncertain as to the starting point for consideration of inventive step within D2 and the rationale underlying the Board's decision on inventive step.

There would have been no cause to file such a request at an earlier stage of the procedure.

The amendments now offered as auxiliary request 5 were not complicated and were convergent,

corresponding to a restriction of a request previously submitted. Accordingly no new issues were introduced and the scope of discussion had not been extended. Nor was there any requirement for investigative effort on the part of the Board or the respondents to deal with this request.

There was no legal ground for the objections of the respondents to the admittance of the request. PA4,6 was demonstrated in the examples on record. Also none of the documents on file referred to PA4,6 which confirmed that this was non-obvious.

XII. The arguments of the respondents can be summarised as follows:

(a) Admittance of documents

(i) D17, D20: The carbon black employed in these reports was very different to that employed in the examples of the patent. More seriously, it had not been shown that this material had been generally available at the priority date of the patent in suit. Hence the opposition division had incorrectly exercised its discretion in deciding to admit these reports.

(ii) D19: It would be of relevance if starting from D8 as the closest prior art and hence should be admitted.

(iii) Enclosure 5.1 to 5.3, submitted with the statement of grounds of appeal: Two new graphites were employed. It was questionable what additional information was provided by these data compared to that in the patent. At most these data confirmed what was stated in the patent to be known. A different polyamide had been employed compared to that in the examples of the patent leading to the question whether these data were suitable to show a technical effect and what information was thereby added to the data in the patent.

(iv) Enclosure 3: this related to matters that had been invoked in the notice of opposition, and hence could and should have been submitted at an earlier stage of the procedure, not towards the conclusion of the appeal proceedings. It should therefore be disregarded.

(v) Enclosure 4: In writing the appellant had explicitly stated that admittance of this document was not requested. Accordingly based on the written submissions there had been no reason for the document to be considered further. There was no ground apparent why this situation should be changed at the oral proceedings. In any case there had been no opportunity to verify the statements made in the 2nd Declaration.

In any case both Enclosures 3 and 4 (declarations 1 and 2) were of doubtful relevance.

(b) Main request- inventive step

There was no basis in the patent for invoking processability in the definition of the problem, The application mentioned only the spiral flow measurement and furthermore in a rather vague manner. The measurement conditions needed to be defined. Reformulation of the problem was permitted only to a limited extent, namely that the problem could be derived from the application as originally filed.

Hence the only effect or property which could be taken into account was thermal conductivity.

D2 was a suitable starting point for the analysis of inventive step in particular because graphite was employed in D2 to provide thermal conductivity to the compositions. Even if D2 emphasised electrical conductivity, it was also required as a matter of course that such compositions exhibited good thermal conductivity. The subject-matter claimed differed from D2 only in the particle size distribution. However there were no examples which demonstrated an effect deriving from this feature. The only difference in the properties of the graphites used in the examples of D17 was the BET surface area. The data of Enclosures 5.1-5.3 differed in three respects from the claimed subject-matter and were also unsuitable to show any effect deriving from the particle size.

It was in any case known from D8 that Timrex**(®) BNB90 graphite resulted in higher thermal conductivity at the same filler loading than for example the KS series graphites. Hence in the search for alternative compositions to those of D2, D8 provided a strong motivation to employ a graphite as claimed. The fact that BNB90 resulted in poorer processability was not of relevance. This was a trade off - a given thermal conductivity could be attained at lower filler loading and the lower processability could be adjusted or compensated for by other means. This was confirmed by D20.

On this basis, an inventive step should not be acknowledged.

(c) The same considerations applied to auxiliary requests 1-4.

(d) Auxiliary request 5 - admittance

The request should not be admitted to the procedure. Nothing new had transpired in the course of the oral proceedings compared to the written proceedings. The conclusions of the Board had been based on the same combination of documents as had been in the proceedings since the outset and on which the decision of the opposition division had been based. Such a claim could have been filed with the statement of grounds of appeal. There was no evidence that there was anything "special" about the now specified polyamide. Furthermore the amendment represented a late change of case. Thus far D2 had been considered to be the closest prior art. The limitation to PA4,6 might have as a consequence that D2 was no longer the closest state of the art. Thus the respondents required the opportunity to analyse the new situation and, if necessary, carry out a further search which was not possible in the time available. The arguments of the appellant itself demonstrated that auxiliary request 5 represented a fresh case.

The request was furthermore not prima facie clearly allowable since there was potentially an objection pursuant to Article 123(2) EPC.

XIII. The appellant requested that the decision under appeal be set aside and the patent be maintained on the basis of the main request, or in the alternative on the basis of one of auxiliary requests 1 to 4 as filed with the letter of 3 December 2019, or on the basis of auxiliary request 5 filed during the oral proceedings of 13 February 2020.

XIV. The respondents requested that the appeal be dismissed.