T 0369/08 28-04-2010

Summary of Facts and Submissions

I. Mention of the grant of European Patent No. 1 368 405 with the title "Flame Retardant Polyester Film" in the name of Dupont Teijin Films U.S. Limited Partnership, in respect of European patent application No. 02712108.6, filed on 21 February 2002 as international application No. PCT/GB2002/000769, published as WO 2002/066538 on 29 August 2002, and claiming a priority date of 21 February 2001 from GB 0104277.9 was announced on 27 April 2005 (Bulletin 2005/17) on the basis of 11 claims.

Claim 1 read as follows:

FORMULA/TABLE/GRAPHIC

Claims 2 to 11 were dependent claims.

II. Notices of opposition were filed on:

- 11 January 2006 by Schill + Seilacher AG (OI) and

- 25 January 2006 by Mitsubishi Polyester Film GmbH (OII)

Opponent OI invoked the grounds of opposition pursuant to Art. 100(a) EPC (lack of novelty, lack of inventive step) and Art. 100(c) EPC (extension beyond the content of the application as filed). Opponent OII invoked the grounds of opposition pursuant to Art. 100(a) EPC (lack of inventive step) and Art. 100(b) EPC (insufficiency of disclosure). The following document was, inter alia cited in support of the oppositions by both opponents:

D1: US-A-4 157 436.

OI noted in its submissions that this document had been cited as "D4" during the pre-grant examination proceedings.

III. In a decision announced on 9 November 2007 and issued in writing on 17 December 2007 the opposition division rejected the oppositions.

(a) The patent in suit met the requirements of Art. 100(c)/123(2) EPC, reference being made to claim 1 as originally filed, and with respect to the specification of the measurement of thermal stability, to page 4 and page 19 lines 20-24 of the original application.

(b) The objections raised pursuant to Art 100(b)/Art. 83 EPC by the opponents and the findings of the decision in respect thereof can be summarised as follows, the objections being indicated by italics:

(i) No lower threshold value was given indicating to which extent thermal stability properties should be retained: In view of the results of the examples of the patent in suit "thermal stability" meant that the films had to completely retain ultimate tensile strength ("UTS") and/or elongation for at least 6 days in air at 140ºC, i.e. that the properties after aging had to be at the same level as those of the starting polyester without any phosphorus compound;

(ii) As copolyester films were sensitive to moisture at elevated temperatures the claimed use could not be carried out under humid conditions: It was credible without proof that the polyesters used according to claim 1 were sensitive to hydrolysis and consequently that mechanical properties would not be retained under humid conditions. Paragraph [0011] of the patent in suit specified that thermal stability was to be measured "in dry air" "under substantially anhydrous conditions" wherein little or no degradation via the hydrolytic pathway took occurred. Furthermore claim 1 had to be read through the eyes of the skilled person taking into account this teaching of the description.

(iii) The meaning of substituents R5 and R6 had been omitted from claim 5: The omitted information was given on page 4 of the patent in suit and was thus available to the skilled person wanting to carry out the invention.

(c) The findings of the opposition division with regard to novelty (Art. 100(a)/54 EPC) can be summarised as follows:

- D1 disclosed "films" rather than "oriented films". D1 contained no disclosure of extruded film (which would necessarily be oriented). An argument of the opponents that polyester films always represented oriented films was dismissed due to the absence of any supporting evidence.

- The functional feature characterizing the use as claimed was not disclosed in D1. The references to thermostability of the copolymer or articles made therefrom in D1 were restricted to behaviour during processing rather than under aging condition. Processing usually took place at temperatures higher than 140ºC and under vacuum or nitrogen rather than in air. Not even the mechanical properties of the polyester, or articles made therefrom under short-time heating conditions were clearly deducible from D1. Accordingly the claimed use was novel in view of D1.

(d) The findings of the decision with respect to inventive step (Art. 100(a)/56 EPC) may be summarised as follows:

- By common consent D1 was the closest prior art;

- The feature that the film was oriented could not support an inventive step;

- The feature relating to thermal stability of articles made from the polymers under oxidising conditions was neither explicitly nor implicitly disclosed in D1, and was not deducible therefrom.

(e) Accordingly the oppositions were rejected.

IV. Notices of appeal against the decision were filed on:

- 18 February 2008 by OI and

- 26 February 2008 by OII

the prescribed fees being paid on the same respective dates.

OII withdrew its appeal by letter dated 8 April 2008.

V. The statement of grounds of appeal was filed by appellant/opponent OI on 21 April 2008. Objections pursuant to Art. 100(a)-(c) EPC were maintained, which can be summarised as follows:

(a) Art. 100(c) EPC:

- the disclosure of thermal stability on page 4 the application as filed referred to that of the polymer, not of an article prepared therefrom;

- the final feature of claim 1, i.e. that relating to retention of mechanical properties before and after aging had been inadmissibly extended compared to the disclosure at the top of page 4 of the application by:

- replacement of "thermal stability of the polymer" by "thermal stability";

- "before and after aging" in connection with the retention of mechanical properties had been omitted;

- "% elongation" had been replaced by "elongation to break"

- The final feature of claim 1 had further been inadmissibly extended compared to the disclosure of page 19 lines 20-24 of the application as filed by:

- omission of the conditions of aging of a film sample (140ºC in an oven);

- the introduction of an "and/or" condition rather than "and" for "ultimate tensile strength" ("UTS") and "elongation to break";

- the original wording on page 19 "aged for different time periods" had been replaced by "over an extended period"

- the standard referred to in the claim (ASTM D882-88) was stated to relate to the measurement of thermal stability instead of ultimate tensile strength and elongation to break, although this standard did not relate to measurements of thermal stability.

(b) Art. 100(b) EPC The patent in suit failed to disclose the required magnitude of the thermal stability and flame resistance of a copolyester film in order for the specified use "of providing thermal stability and flame retardancy" to be fulfilled. In this connection the required comparison was between the properties of one and the same polymer before/after aging and not, as the opposition division had held, between two different polymers (see section III.(b).(i), above). The standard specified in the claim required that the measurements be carried out at a relative humidity of 50±5% and a temperature of 23±2ºC and also required a conditioning of the samples under these conditions for at least 40 hours prior to carrying out the measurement. Thus the requirements of the standard and the maintenance of "substantially anhydrous conditions" as specified in paragraph [0011] of the patent were mutually exclusive.

(c) Art. 100(a)/54 EPC The subject matter of claim 1 was anticipated by the D1, which disclosed that the flame resistant polyesters thereof could be employed to prepare fibres, boards and films, in particular due to their thermal stability. As there were only two types of film, namely oriented and non-oriented, the disclosure of the term "film" in D1 mandatorily encompassed oriented films. In any case the skilled person was aware that in particular thin films and thermally stable films were necessarily always stretched since the resulting orientation of the molecular chains significantly improvement the mechanical properties.

(d) Art 100(a)/56 EPC Since D1 disclosed oriented fibres it would be obvious that the copolyesters could also be employed to form films, in particular oriented films having thermal stability because D1 described oriented fibres produced with a draw ratio of 3.8 (example 7).

VI. The patent proprietor, now the respondent replied with a letter dated 9 September 2008. The main request was for dismissal of the appeal. Alternatively maintenance of the patent in amended form on the basis of one of the first to third auxiliary requests was requested. Corresponding sets of claims were however not submitted at this stage. The arguments advanced may be summarised as follows:

(a) Art. 100(c)/123(2) EPC:

- The feature that thermal stability was measured in terms of retention of certain physical properties was based on page 4 lines 1 to 11 in combination with page 19 lines 20-24 of the application as filed, reference being made to the WO publication;

- The term "thermal stability" referred to that of an article, in particular a film made from the polymer. This was apparent from page 3 lines 9-15 and 20-22 of the application and made explicit by page 4 lines 1 to 11 which explained that the thermal stability was determined in terms of specific mechanical properties before and after aging. The skilled person knew that these properties would be determined on a polymer article rather than on a polymer e.g. in pellet form. The specified ASTM standard could not be applied to pellets. This was confirmed by the final sentence in the indicated passage of page 4 of the application which referred to a polyester article and by the description of the method on page 19;

- The omission of the wording "before and after aging" did not result in an extension beyond the content of the application as filed. This phrase was disclosed at page 4 lines 5-8 of the application as equivalent in scope to "exposure in air to temperatures above ambient temperatures". The wording employed in the claim, i.e. a temperature of 140ºC and "extended period" had its basis at page 4 lines 4-5 of the application.

- The terms "% elongation" and "elongation to break" were used interchangeably in the application as filed as became apparent from pages 4 and 19 of the application.

(b) Art 83 EPC

- No evidence had been submitted that the copolyesters defined in operative claim 1 did not impart the properties of thermal stability and flame retardancy.

- The objection regarding the absence of threshold values was a matter governed by Art 84 EPC, not Art. 83 EPC and hence was not a matter for discussion in these proceedings.

- In any case analysis of the data showed, if the specification was properly construed, that these objections were without foundation. Based on an extended version of Table 2B of the patent, showing in addition the measurement errors, it was clear that the retention in UTS of the control (no phosphorus compound) and example 1 were the same within experimental error. In assessing the retention the appropriate comparison was with the pure polyester not containing the phosphorus modifier, but not a comparison of one and same film before/after aging. This was made clear in paragraph [0009] of the patent in suit. Accordingly the critical parameter specified in the claim was a relative one, not absolute. Regarding the determination of the physical properties it was incorrect to construe the patent as requiring that the measurements be carried out at 140ºC under anhydrous conditions- these conditions applied only to the aging process. The mechanical properties were measured according to the specified ASTM test before or after aging, not within the confines of the oven used for the aging test.

(c) Art. 54 EPC:

- D1 did not refer to the thermal stability of the phosphorus containing copolyester or to the thermal stability of the end product, i.e. the film and hence could not disclose the claimed use.

- D1 did not disclose the technical effect specified in operative claim 1 as it was directed essentially only to the heat stability of the phosphorus compound itself during the polymerisation process and its effect on the degree of polymerisation attainable.

- D1 did not disclose an oriented film.

(d) Art. 56 EPC:

- The teachings of D1 concerned stability of the phosphorus compounds themselves under the conditions of preparation of the polyesters rather than of articles prepared from the resulting polymers thus

- D1 had no bearing on the effect demonstrated in the claimed use.

VII. On 11 February 2010 the Board issued a summons to attend oral proceedings. In a communication dated 25 February 2010 the Board inter alia essentially concurred with the submissions of the respondent/patent proprietor concerning the nature of the teachings of D1 and its relationship to the use defined according to the operative claims. The absence of the auxiliary requests referred to by the respondent/patent proprietor (see section VI, above) was noted.

VIII. By a letter dated 26 February 2010 the opponent and former appellant OII stated that it would not attend the oral proceedings.

IX. Together with a letter dated 1 March 2010 the respondent/patent proprietor submitted the three auxiliary requests referred to in its rejoinder to the statement of grounds of appeal.

X. Together with a letter dated 15 March 2010 the appellant/opponent announced that its legal status had changed, which change was duly registered by the Office, as announced in a communication dated 25 March 2010. A further document was cited:

D7: "S.J. Chang: Polymer Degradation and Stability, Vol. 54, no. 2-3 (1996), pages 365-371". The appellant/opponent observed that this document had been cited in the proceedings before the examining division as the closest prior art (designated D3 in those proceedings- see the International Preliminary Examination Report). The submissions of the appellant/opponent OI can be summarised as follows:

- D7 related to the thermo-oxidative decomposition of phosphorus containing polyesters and solved the problem underlying the patent in suit;

- D7 exemplified inter alia PET having copolymerised therein units derived from the phosphorus compounds identified as "Phosgard" and "Ukanol", employed in the comparative and inventive examples of the patent in suit respectively;

- D7 disclosed that in simulated aging tests carried out under oxygen at 130ºC those polyesters containing the "Phosgard" unit - identified in D7 as "PET-co-PEPP" exhibited significantly greater decomposition that either unmodified PET or that containing the "Ukanol" phosphate compound (identified in D7 as "PET-co-PEDDP");

- This teaching rendered the subject matter claimed, i.e. the use of the specified copolyesters in order to provide improved thermal stability obvious.

XI. Oral proceedings were held before the Board on 28 April 2010.

(a) Art 100(c)/123(2) EPC The appellant/opponent objected that the conditions and timing employed for the measurement of aging were not completely specified in the claims. With regard to the conditions it was only stated that the measurements were carried out under the indicated conditions, although such interpretation was technically meaningless. The timing of the measurements, as explained at page 4, i.e. before/after aging was not specified in claim 1, meaning that this subject matter extended beyond the application as filed. The indicated parts of the description were in any case inconsistent with each other since page 4 of the application referred to the polymer whilst the claim and page 19 of the application referred to the film. The respondent/patent proprietor explained that the measurement of thermal stability was set out in the application as filed, reference being made to page 4 lines 1-11 and page 19 lines 20-24. Since a document could be its own lexicon, as held in the case law of the Boards of Appeal, the term "Thermal Stability" in the claims had to be interpreted in this framework, leading to the conclusion that there was no extension of subject matter.

(b) Art 100(b)/83 EPC The appellant/opponent conceded that its objections in this respect were at the border of Art. 83 and 84 EPC. The aging resistance was determined according to the operative claims indirectly, i.e. by measurement of certain physical properties. The data in the patent showed a decrease in the measured properties over the time of measurement, i.e. these properties were not "retained". The patent did not explain what amount of degradation could still be tolerated and hence where the limit for deeming a composition to exhibit "retention" of the indicated properties lay. This was exacerbated by the fact that the examples of the patent employed different aging times. Hence it was not known how to repeat the examples to establish whether a given composition met the requirements of the claim. The respondent/patent proprietor objected that this was in fact an objection pursuant to Art 84 EPC and referred to the submissions made in the rejoinder to the statement of grounds of appeal (see section VI.(b), above).

(c) Art. 54 EPC The appellant/opponent stated that the claims were directed to the use of a known polymer to provide a known product. As the polymer was known from D1 to be heat stable this was an inherent property and consequently would also be exhibited by articles made from the polymer, e.g. films. The feature of orientation was also inherent since ca 70% of all films were oriented. In particular D1 at col. 9, final section explicitly taught that the phosphorus compounds had no effect of lowering the molecular weight of the polyesters and consequently had no detrimental effect on the physical and colour properties of the resulting polyester shaped products. The respondent/patent proprietor in addition to reiterating the arguments from the written procedure (see section VI.(c), above) argued that D1 failed to disclose two features of the claims, namely oriented films or the specified use of the polyesters. Further, the processing conditions exerted a significant effect on the properties of fabricated articles. Orientation resulted in an increase in rigidity; however simply stretching a film did not necessarily and inevitably result in orientation. Consequently it was not correct to argue that properties of an article would inherently be determined by those of the polymer from which it was made.

(d) After deliberation the Board announced that the main request met the requirements of Art. 54, 83 and 123(2) EPC.

(e) Art. 56 EPC - Admissibility of D7 The appellant/opponent sought to invoke D7 as the closest prior art for consideration of inventive step pursuant to Art. 56 EPC, this document having been cited for the first time with its letter of 15 March 2010 (see section X, above). The respondent/patent proprietor requested that this document not be introduced. The arguments of the appellant/opponent regarding the circumstance surrounding the citing of this document at this stage of the procedure can be summarised as follows:

- This document had been cited in the examination proceedings as the closest prior art and hence was known both to the opposition division and to the patent proprietor;

- This had now been cited in the light of the comments by the Board with respect to thermal stability made in its communication (see section VII, above). The communication had resulted in a reappraisal of this document. Its significance had not previously been appreciated;

- At the time of filing the opposition D1 had been considered sufficient, hence D7 had not been cited. The citing of this document now could not be construed as an abuse of procedure.

The arguments of the respondent/patent proprietor concerning the citation of D7 can be summarised as follows:

- This document had been filed at a very late stage;

- Documents cited in the search report did not automatically form part of the opposition proceedings;

- This document had not been cited in either notice of opposition, although other documents from the search report had been;

- The late citing of this document was an abuse of procedure. The opponent had known of this document for at least four years;

- The existence of an abuse of procedure was reinforced by the fact that the appellant/opponent had not sent a courtesy copy of the submission of 15 March directly to the respondent/patent proprietor.

- Any case based on D7 constituted an entirely new opposition. Thus if this document were to be admitted then the case should be remitted to the first instance.

The arguments of the parties concerning the question of prima facie relevance of this document can be summarised as follows: The appellant/opponent:

- D7 addressed precisely the same problem as the patent in suit, i.e. resistance to thermally induced oxidative degradation of modified polyesters;

- The same modifiers (comonomers) were employed as in the patent.

- The same conclusions regarding the effects on thermal stability of the final copolyester in relation to the main chain/pendant phosphorous groups were reached, since:

- D7 explained that having a phosphorus link in the main chain resulted in chain scission and hence a reduction in thermal stability. This did not happen when phosphorus was present in a pendant group, which thus gave better thermal stability.

- Although there were differences in the measurement conditions, e.g. D7 employed pure oxygen at 130ºC for 12 hours rather than air at 140ºC for a number of days and D7 employed direct measurement of degradation, i.e. weight loss rather than indirect measurements (mechanical properties) the teaching addressed the same problem as the patent in suit.

- D7 also referred to the formation of fibres and plastics including textiles and contained a direct reference to a patent family member of D1 in Footnote 4.

- There was no evidence that the morphology of the polymer e.g. in an oriented film exerted any effect on the properties; on the contrary the properties were determined solely by the chemical constitution of the polymer forming the film.

- In any case the claims did not specify the degree of orientation or crystallinity.

The arguments of the respondent patent/proprietor:

- D7 had been dealt with during the proceedings before the International Preliminary Examining Authority ("IPEA") in a letter dated 4 October 2002 filed together with the demand for examination. This letter ultimately resulted in the amendment which resulted in the patent being granted as was apparent from the International Preliminary Examination Report ("IPER"). This letter was in the public domain and established that the arguments advanced therein had been accepted by the IPEA as constituting general knowledge.

- D7 considered only polymer chip, not articles, as followed from page 366 of the document. Consequently the results reported in D7 had been obtained on the basis of amorphous articles not oriented film. The degradation behaviour of a crystalline product, e.g. oriented film could not be predicted on the basis results obtained on polymer chip;

- Changes in mechanical properties of an oriented film could not be deduced from the behaviour of polymer chip, e.g. due to differences in the rates of gas diffusion arising from the morphology;

- The aging test in D7 had been carried out under fundamentally different conditions from those specified in the patent in suit. Thus in the examples of D7 oxidative degradation would have played a larger role than thermal degradation whereas in the patent in suit these two degradation pathways were in balance;

- D7 contained no information relating to the physical properties specified in the operative claims;

- In any case a certain amount of chain breakage could be tolerated without giving rise to a decrease in mechanical properties. Thus merely showing the existence of chain breakage would not mean that inevitably the physical properties were also impaired.

(f) The respondent/patent proprietor requested that if this document was admitted that the case be remitted to the opposition division and an apportionment of all future costs arising from the resumption of the opposition proceedings be made.

The appellant/opponent did not resist the request for remittal but disputed that there was any basis in the EPC for the request for apportionment of costs. In any case according to Art. 104 EPC it was for the opposition division, not the Board to decide upon costs.

XII. The appellant/opponent requested that the decision under appeal be set aside and that European Patent no. 1 368 405 be revoked. The respondent/patent proprietor requested that the appeal be dismissed. In the alternative it is requested that the patent be maintained in amended form on the basis of one of the sets of claims according to the first, second or third auxiliary requests, filed with letter of 1 March 2010 in that order: The respondent requested that the case be remitted to the First Instance if document D7 were to be introduced in the proceedings and further requested an apportionment of costs.