T 0806/03 13-09-2006

1. Both appeals are admissible.

2. Procedural matters

2.1 In view of the fact that all parties had been summoned to the oral proceedings in due time (section IX, above), the Board decided to continue the proceedings in the absence of Appellant II and of the other Parties as of right (Opponents I and II) in accordance with Rule 71(2) EPC.

2.2 On the one hand, Article 100(c) EPC had been a ground for opposition initially invoked by Opponent II (Notice of Opposition: page 2, cf. section II, above). On the other hand, Appellant I, when limiting its requests in its letter dated 18 July 2006, nevertheless maintained its appeal "as a precaution to ensure freedom to pursue claims broader than set D" (section IX (1), above). This information had been made available to the other parties by communication dated 24 July 2005, i.e. more than one month before the oral proceedings (Rule 78(2) EPC), which gave them the opportunity to reconsider their intentions concerning the case in good time before the oral proceedings.

Whilst, according to the Opinion of the Enlarged Board of Appeals G 4/92 (OJ EPO 1994, 149), a decision against a party, which has been duly summoned but fails to appear at oral proceedings, may not be based on facts or evidence put forward for the first time during those oral proceedings (Conclusions 1 and 2), the Enlarged Board also emphasised in No. 4 of the reasons that, in accordance with Rule 71(2) EPC and in the interests of the proper administration of justice, no party should be able to delay the issue of a decision by failing to appear at the oral proceedings. In this respect, the Board follows the view expressed in T 912/91 of 25 October 1994 (No. 10 of the reasons; not published in OJ EPO):

"Finally, the Board finds that considering and deciding in substance on the maintenance of the patent on the basis of the present claims as amended during oral proceedings in the absence of two of the Opponents does not conflict with the decision of the Enlarged Board of Appeal G 4/92 (OJ EPO 1994, 149). According to this decision, a party who fails to appear at oral proceedings must have the opportunity, in accordance with Article 113(1) EPO, to comment on new (and therefore surprising) facts and evidence submitted in those proceedings. The submission during oral proceedings of auxiliary requests is, clearly, neither a 'fact' nor can it be 'evidence' within the meaning of the above decision, so that that decision does not apply in such a case. Were it otherwise, no decision could ever be issued at the end of an appeal hearing where, as is usually the case, auxiliary requests are filed and, as is also frequently the case, one or more of the Opponents does not attend the hearing. This would render such hearings pointless, as well as offend the general principle of legal certainty, i.e. the general interest of the public in the termination of legal disputes ('expedit reipublicae ut sit finis litium')".

On the basis of the above facts and findings, the Board came to the conclusions that amendments carried out in the claims before grant and still contained in the sets of claims submitted later by Appellant I had also to be considered in the oral proceedings with regard to the requirements of Article 123(2) EPC, irrespective of the absence of several parties in the hearing, and that all the parties must have expected that these questions would be discussed. Therefore, the requirements of Article 113(1) EPC are met.

3. The decision under appeal

3.1 As already mentioned above, one of the grounds for opposition relied upon and substantiated by the Opponents with regard to the patent in suit, which was derived from a divisional application, had been based on Article 100(c) EPC.

3.2 With regard to the Main Request of the Patent Proprietor in the opposition proceedings, which was directed to the maintenance of the patent as granted, the Opposition Division decided that Article 123(2) EPC had not been complied with in comparison with "the application as originally filed, which is the parent application WO91/09882" (No. II.1.1 of the decision under appeal).

3.2.1 As this Main Request is no longer maintained by Appellant I (section IX (1), above), it is not subject-matter to be dealt with in this decision. This finding is also valid for the auxiliary requests on the basis of Sets A to C, mentioned in sections II (3) and IV, above, which were withdrawn at the same time.

3.2.2 Nevertheless, the Board observes with regard to the passage of the decision under appeal referred to above, that the subject-matter of a European patent must not extend (i) beyond the content of the application as filed, or (ii), if it was granted on a divisional application (or on a new application filed in accordance with Article 61 EPC), beyond the content of the earlier application as filed (cf. the wording of Article 100(c) EPC). Aspect (i) is governed by Article 123(2) EPC, aspect (ii) by Article 76(1) EPC.

Hence, in the present case, Article 123(2) EPC provided the basis for examining the allowability of amendments of the subject-matter of the divisional application No. 94 202 617.0 carried out during its examination in comparison with the initial text of this divisional application as filed on 12 September 1994 (aspect (i), as above), whereas the comparison of the text of the granted patent with WO-A-91/09882 (the text of the parent application) should have been based on Article 76(1) EPC (aspect (ii), as above).

The reference in the decision under appeal to the wrong Article made, however, no difference with regard to the substance of the decision on the Main Request at issue in the opposition proceedings (No. 1.1 of the reasons for the decision under appeal), since the descriptions of the parent application as published in WO-A-91/09882 and of the divisional application as filed were identical.

Main Request of Appellant I

4. Wording of the Claims

4.1 For the reasons given in section 2.2, above, the Main Request as identified by Appellant I in its letter dated 18 July 2006 (section IX (1), above) and as still maintained at the beginning of the oral proceedings, had to be considered by the Board with regard to the requirements of Article 123(2) EPC.

Claim 1 of this set of claims was based on a combination of features contained in the granted version of Claims 1 and 2, respectively, whereby the common definition of radicals X3 and X4 as contained in the anion was derived from granted Claim 2 (sections I and II (3), above), which had been "made consistent with the text on page 14" (letter dated 14 April 1997, page 1, third paragraph) in reply to a communication of the Examining Division before grant.

4.2 In order to meet the objection raised by the Board under Article 123(2) EPC (section X (1), above), a new Main Request was filed in the oral proceedings (section X (2), above). It differs from the replaced former version only by the wording of Claim 1. In this claim, the previous formulation in the common definition of radicals X3 and X4 which referred to "hydrocarbyl radicals containing from 6 to about 20 carbon atoms" was replaced by "hydrocarbyl radicals containing from 1 to about 20 carbon atoms".

4.2.1 This new range has its basis on page 14, lines 16/17. Therefore, Claim 1 of the new Main Request complies with Article 123(2) EPC.

4.2.2 Having regard to Claim 1 as granted (section I, above), it is evident that the incorporation of the features of Claim 2 as granted in Claim 1, albeit in extended form (referring to a range of C1 to C20 instead of C6 to C20) (cf. sections I, II(3) and X (2), above), comes down to a limitation of the scope of protection conferred by the patent in suit. The new Claim 1, therefore, does not violate Article 123(3) EPC in this respect.

4.3 Furthermore, Appellant II had objected to the additional feature in the definition of the anion in Claim 1 as maintained (sections II (3), III (2) and V (1), above), because this wording was not, in its opinion, supported by the application as originally filed. The relevant passage on page 19 read as follows:

"With respect to the combination of the metallocene component with the activator component to form a catalyst of this invention, it should be noted that the two compounds combined for preparation of the active catalyst must be selected to avoid transfer of a fragment of the anion, particularly an aryl group, to the metal cation, thereby forming a catalytically inactive species. This can be done by steric hindrance, resulting from substitutions on the cyclopentadienyl carbon atoms as well as substitutions on the aromatic carbon atoms of the anion. It follows, then, that the metallocene components comprising perhydrocarbyl-substituted cyclopentadienyl radicals could be

effectively used with a broader range of activator compounds than could metallocene components comprising unsubstituted cyclopentadienyl radicals. As the amount and size of the substitutions on the cyclopentadienyl radicals are reduced however, more effective catalysts are obtained with activator compounds containing anions which are more resistant to degradation, such as those with substituents on the ortho positions of the phenyl rings. Another means of rendering the anion more resistant to degradation is afforded by fluorine substitution, especially perfluoro-substitution, in the anion. Fluoro-substituted stabilizing anions may, then, be used with a broader range of metal compound (first components). Activators in which the anions comprise pentafluorophenyl groups are preferred for preparing ion-pair metallocene catalysts of this invention."

4.4 This disclosure can be summarised as follows:

When reacting the MC and the activator compounds with one another, there is a danger of forming catalytically inactive species, caused by the transfer of a fragment of the anion to the cation. Such a transfer of a fragment, particularly an aryl group, can only be the result of the degradation of the anion. Therefore, such a degradation must be avoided.

This goal can be achieved by substituting either the Cp ligand(s) of the MC or the aromatic carbon atoms of the anion, in particular in the ortho-position of phenyl rings. In this way, steric hindrance is achieved, which prevents the transfer of a fragment of the anion (after its degradation) to the cation. Another way of increasing the resistance of the anion against degradation is its fluorine-substitution.

Amongst the above possible choices, more effective catalysts are obtained with activator compounds containing anions being more resistant to degradation.

In view of these findings, the Board is satisfied that both aspects of the additional feature of Claim 1 (indicated by (i) and (ii), respectively, see sections II (3), IX (1) and X (2), above) comply with Article 123(2) EPC.

This amendment also clearly results in a limitation of the scope of protection conferred by Claim 1 as granted, so that the requirements of Article 123(3) EPC are also complied with.

4.5 Consequently, the requirements of Articles 123(2) and 123(3) EPC are met by the new Main Request.

Furthermore, in view of the fact that the descriptions of the application as filed and of the parent application as published in WO-A-91/09882, including in particular those passages referred to above with regard to Article 123 EPC, are identical, the Board has come to the conclusion, also with regard to Article 76(1) EPC, that the objection under Article 100(c) EPC raised in the opposition proceedings cannot prevail.

5. Problem and solution

5.1 The patent in suit concerns a catalyst system for the polymerisation of olefins in gas phase or slurry polymerisation on the basis of an ionic catalyst system, the homogeneous version of which has been known from D1, as admitted by Appellant I.

5.2 Apart from ion pair catalysts corresponding to any one of the formulae in Claim 1 (cf. section II (3), above; patent in suit: Claim 2 as granted and D1: page 8, lines 27 to 37), document D1 additionally refers to solid catalytically active zwitterion-type compounds. Such compounds were formed by decomposition of a number of unstable ionic catalysts prepared eg from peralkyl-Cp-MC and tetra-phenyl- or tetra-(para-alkyl)phenyl-borate compounds (D1: page 8, line 63 to page 9, line 26; Examples 1, 4, 10 and 22). The objects to be achieved in D1 were good control of MW and MWD, no activation equilibrium, no need for an undesirable cocatalyst and increased comonomer incorporation (D1: page 3, lines 6 to 12).

5.3 When accepting D1 as the closest state of the art (as acknowledged in the decision under appeal and by Appellant I; sections III (5), and X (6), above; and as accepted as one possible starting point for the assessment of inventive step by Appellant II, section V (2), above), the technical problem to be solved with regard to D1 may be seen in the provision of a heterogeneous catalyst suitable for gas phase and slurry polymerisation, which reduces reactor fouling and provides polymers having a higher bulk density than the homogeneously catalysed polymerisation of D1 without impairing the other properties achieved in the homogeneously catalysed polymerisation, namely high molecular weight, narrow molecular weight distribution and composition distribution, good comonomer incorporation, good sequence distribution and controlled particle size (cf. [0010] and Statement of Grounds of Appeal of Appellant II: page 2, 2nd half; section V (2), above).

5.4 Whilst Appellant I had argued in its letter dated 29 January 2004 (item 3.3 "Surprising effect", section VI, above) that these goals had been attained in the examples of the patent in suit, Opponent II (being a Party as of right) referred again to its test report and argued against the reasons in the decision under appeal (sections II (3), VII and IX (4), above), wherein reference had been made to credible doubts with regard to the results in the test report, that "The invention claimed is in no way limited to a particular support or a particular method to bring the catalyst on a support". Moreover, Opponent II took the view that its own conclusions drawn in that report "are applicable and prove that whatever the problem underlying the patent is, it is not solved over the full scope of the claims" (letter dated 9 February 2004, page 7, 2nd and 3rd paragraphs).

5.5 In paragraphs [0030] to [0032], explanations are given concerning the chemical composition of support material and the requirements to be fulfilled by such carriers. In particular, the importance of removal of moisture and of surface hydroxyl groups is underlined there ([0030]: "... subjected to a thermal treatment in order to remove water and reduce the concentration of the surface hydroxyl groups"; [0031]: "Chemical dehydration converts all water and hydroxyl groups on the oxide surface to inert species."; [0032]: "... has been thermally or chemically dehydrated such that it is substantially free of absorbed moisture"). In view of these statements, it is evident to the Board that the content of water and/or OH-groups of the support material affects the activity of the catalyst and that the specific conditions to be maintained in the treatment of the support material before it is used depend inter alia on its chemical nature.

5.5.1 This question was apparently discussed in depth in the hearing before the Opposition Division (Minutes of 14 May 2003: 2nd half of page 3, item 5, and page 4, 1st and 2nd paragraphs; and decision under appeal: item II.3.3.1, in particular the paragraph bridging pages 6 and 7). It follows therefrom that, whilst it had been asserted in the report that the support treatments had corresponded to those described in Examples 1, 4 and 14 of the patent in suit, there were significant departures from those process steps as disclosed in these examples (cf. test report: page 2).

5.5.2 Thus, whilst, in Example 1, basic alumina had been dried at 100ºC under vacuum, treatment (i) started from a commercial silica heated at 100ºC in air before vacuum was applied; in treatment (ii) a large quantity of the oxide had been dried in a tube furnace for a limited time, it is not evident to the Board that the water had been removed to a similar extend as in Example 4, nor that the concentration of the surface hydroxyl groups had accordingly been reduced. In treatment (iii), allegedly corresponding to Example 14, the amount of the organoaluminium added was based on an assumption about the surface OH content of the calcined silica. Neither is the basis of this assumption evident to the Board, nor can it be excluded that, when the whole water adsorbed by the inorganic oxide material and all hydroxy groups of the oxide had been converted to inert species, an excess of the aluminium compound was left behind, which would have also had an effect on the polymerisation.

Further explanations to the test report to overcome the objections in the decision under appeal have not been given by the opposing parties in writing, nor have they attended the oral proceedings before the Board where it might have been possible to elucidate these issues.

In any case, the onus of proof for the assertion that the problem was not solved in the full scope of the claims has been on the Opponents who have not convincingly discharged this burden.

5.6 Nor are any experimental data available, which would challenge those results provided by the examples of the patent in suit. In particular, Example 2 demonstrates that the use of a supported catalyst resulted in a significant increase of the bulk density.

5.7 In view of these facts and findings, the Board has no reason to come to a conclusion with regard to the above test report of Opponent II different from that in the decision under appeal. Nor is it in a position to refute the arguments of Appellant I in its letter dated 29 January 2004 (sections VI and 5.4, above) that the different aspects of the relevant technical problem (section 5.3, above) were indeed solved by the catalyst as defined in Claim 1 when used in the polymerisation process of Claim 3.

6. Inventive step

It remains to be decided whether the claimed solution of this problem derives in an obvious way from the cited documents.

6.1 Although including catalytic active compounds having the same chemical formula as those represented by the general chemical formulae in Claim 1 (section 5.2, above), D1 refers nowhere to heterogeneous catalysts supported on an inorganic oxide carrier which was suitable for use in gas phase or slurry polymerisation. Rather, only different generations of unsupported homogeneous catalyst systems of the prior art, reaching from Ziegler-Natta to MC/alumoxane catalysts, and the homogeneous ionic catalyst claimed therein, have been considered in the document.

All these catalysts were soluble in the polymerisation mixture with one exemption in Example 9, wherein mention is made of polyethylene obtained by means of a yellow precipitate suspended in toluene (apparently in a slurry polymerisation using a solid catalyst). This precipitate had been obtained in Example 8 from tri(n-butyl)ammonium tetra(o-tolyl)boron and bis(Cp)zirconium dimethyl. However, no further particulars can be derived from either example about the structure of the precipitate or about the polymer obtained.

In view of these facts and findings, the Board cannot derive any hint in D1 pointing to a solution of the above relevant problem, let alone to the solution as defined in Claim 1, and, therefore, takes the view that the document itself cannot make the subject-matter of Claim 1 obvious.

6.2 Amongst the further documents cited by the Opponents, specific reference was made by Appellant II to D5 (section V (2), above). It relates to a solid catalyst for olefin polymerisation comprising (A1) a compound of a transition metal of Group IVB of the Periodic Table, (A2) an AlOx and (A3) a particulate organic or inorganic compound carrier in specific atomic ratios (Claim 1), and it relates to a process for forming this catalyst (Claim 7). Whilst the transition metal compound was further specified in Claim 3, the support material was referred to in all claims of D5 as a "particulate organic or inorganic compound carrier".

In view of this wording in the claims of D5, the Board cannot concur with the approach of Appellant II in its Statement of Grounds of Appeal, who criticised the decision under appeal for considering the AlOx as "a key feature for achieving an active metallocene polymerisation catalyst" in D5. In the Board's view, it is clearly the AlOx which is the only fixed feature within the definition of the claimed subject-matter of D5, leaving no room for variation in this respect. Hence, it is unimportant for the question to be decided here that Appellant II had not found any hint in the literature that the methods of supporting mentioned in D5 should be limited to AlOx systems (Statement of Grounds of Appeal: page 4, 2nd paragraph: "Zunächst haben wir in der Literatur keinen Hinweis gefunden, dass die in D5 genannten Trägerungsmethoden auf Aluminoxansysteme beschränkt sein sollten ..."; section V, above), because the decisive question is whether it was obvious to solve the relevant technical problem by using a particulate inorganic support in an ionic catalyst system, formed according to one of the formulae in Claim 1 of the Main Request (sections II (3) and X (2), above) and whether there was a hint derivable from the disclosure of D5 to this end.

Although the description of D5 discloses that metal compounds containing at least one Cp ligand (Claim 3) and the particulate carrier might be organic or inorganic (page 12, last two lines), that inorganic oxides were preferred as the inorganic compound carrier (page 13, lines 24 to 31) and that high bulk density could be achieved by using the catalyst of D5, the Board has not found any reason in the document to replace its essential component AlOx and, thus, to use a completely different catalyst system.

6.3 The catalyst of D4 differs from that in D5 by an additional mandatory olefin prepolymerisation step, otherwise the features of its catalyst before this additional step are essentially the same as in D5. Thus, apart from the prepolymerisation, this catalyst is also composed of a transition metal compound supported on a carrier and an AlOx. The transition metal compound may have (as in D5) Cp ligands and may additionally be treated with an organic metal compound before it is contacted with the support (Claim 3; page 12/13), which may be a porous inorganic oxide (Claim 7). As in D5, the only component, the presence of which is unambiguously required in all its embodiments, is the AlOx. Consequently, the arguments in the previous section are also valid for this document.

6.4 The essential requirement of D3 is a supported catalyst component treated with at least one MC and at least one non-MC transition metal compound (Claim 1), which according to Claim 12 is used together with a cocatalyst comprising (a) an AlOx and an organometallic compound of a metal of Groups IA, IIA, IIB or IIIA of the Periodic Table. The support may be any solid, particularly porous support such as talc or an inorganic oxide or a resinous support material eg a polyolefin. The preferred material is an inorganic oxide in finely divided form (page 5, last paragraph).

In order to obtain polymers having an improved particle size and bulk density (not necessarily referring simultaneously to narrow particle size distribution and high bulk density) and also to obtain polymers having varied ranges of MWD and/or CD, this document thus teaches, in essence, to combine a MC/AlOx catalyst with a Ziegler-Natta catalyst, in supported form. Nowhere in the document are any hints to be found which would give an incentive to delete the Ziegler-Natta and the AlOx components. Therefore, although referring to the aspect of improved particle size and bulk density, D3 goes in the direction of a completely different solution and, rather, leads the skilled reader away from the solution found in the patent in suit.

6.5 Document D2 relates to an olefin polymerisation supported catalyst comprising the reaction product of at least one MC of a metal of Group 4b, 5b and 6b of the Periodic Table and an AlOx, whereby the reaction product is formed in the presence of a support. Thus, like D3, D4 and D5, it also positively requires the presence of an AlOx, even though "without the presence of the objectionable excess of alumoxane as required in the homogeneous system" (page 3, lines 13 to 15). Although D2 also refers to a support which may preferably be an inorganic oxide in finely divided form, optionally pre-treated by dehydration (Claim 2; page 4, lines 26 to 29 and page 5, paragraph 2) and the catalyst may be used in solution, slurry and gas phase polymerisations (page 11, line 26 et seq.), the requirement that an AlOx be used cannot be dispensed with, in particular in view of the fact that, according to the examples, the AlOx acts not only as an activator but also as a scavenger, as pointed out by Appellant I (section X (6), above).

6.6 In view of these facts and findings, the Board cannot see any reason to consider the AlOx as not being a key feature of the subject-matter of each of D2 to D5, which should be replaced by something else in order to overcome the above relevant technical problem, in particular having regard to the teachings in D3 and D5, according to which the problem of improved bulk density could already be solved with MC/AlOx catalyst systems. Any suggestion to replace the AlOx can only be based on the knowledge of the patent in suit, i.e. an inadmissible ex-post facto analysis.

Nor could be expected, let alone derived from any one of D2 to D5, that the ionic catalyst of D1 would be compatible with the oxide carrier, so that an active catalyst would be obtained which would solve the above relevant technical problem (section 5.3, above).

In the Board's view, these conclusions are valid irrespective of whether D1 or any one of D2 to D5 is used as the starting point for the assessment of inventive step.

Therefore, the subject-matter of Claim 1 is not made obvious by any one of the documents, relied upon by the Opponents, i.e. by Appellant II and the other Parties as of right, individually or in combination with one another.

7. By the same token, these findings are also valid for the process of Claim 3 and the embodiment in dependent Claim 2.

Consequently, the subject-matter of Set D (the Main Request of Appellant I) involves an inventive step.

8. Since the Main Request of Appellant I has been successful, there is no need to further consider its auxiliary requests.

9. Correction of the priority date

According to the Minutes of the oral proceedings before the Opposition Division (item 2), the Opposition Division had considered the request for the correction of the priority date as filed by letter dated 14 March 2003 (cf. item I.5 of the decision under appeal) to be allowable, this had not been disputed by the Opponents. In view of the wording of Article 76(1) EPC, the Board sees no reason to deviate therefrom. Consequently, the front page of the patent specification should be corrected accordingly.