T 0023/04 05-04-2006

I. Mention of the grant of European Patent No. 0 457 455 in respect of European patent application No. 91 303 886.5 in the name of Shell Oil Company, later assigned to Union Carbide Chemicals & Plastics Technology Corporation, was announced on 3 July 1996 (Bulletin 1996/27) on the basis of 16 claims.

Claims 1, 6, 7, 10, 12 and 16 read as follows:

"1. A polypropylene impact copolymer composition which comprises a homopolymer phase predominantly comprising a propylene homopolymer and a copolymer phase predominantly comprising a copolymer of ethylene and propylene, wherein the ratio of the intrinsic viscosity of the copolymer phase to that of the homopolymer phase is from 0.7/1 to 1.3/1, the intrinsic viscosities being determined according to ASTM D 1601-78 in decalin at 135ºC, that of the copolymer phase ([eta]copol) being derived from the intrinsic viscosity of the composition ([eta]prod) in accordance with the formula:

FORMULA/TABLE/GRAPHIC

where [eta]homo is the intrinsic viscosity of the homopolymer phase and Fc is the fraction of the composition which is copolymer.

6. A composition according to any one of the preceding claims wherein the composition is obtainable by a two-stage polymerization process.

7. A composition according to claim 6 wherein the two-stage polymerization process is a gas phase process wherein predominantly propylene is initially polymerized to form the homopolymer phase and the product of the initial polymerization is contacted with a mixture of propylene and ethylene to form the copolymer phase, the polymerizations being conducted in the presence of an olefin polymerization catalyst and the molecular weight at least one of the homopolymer phase and the copolymer phase being controlled to provide said intrinsic viscosity ratio.

10. A composition obtainable by visbreaking a polypropylene impact copolymer composition as claimed in any one of the preceding claims to provide a visbroken composition having a melt flow of from 2 to 200 according to ASTM-1238, condition L.

12. A composition according to any one of the preceding claims which further comprises a nucleating agent.

16. Shaped articles of a composition as claimed in any one of the preceding claims."

Claims 2-5 defined preferred embodiments of the composition of claim 1. Claims 8 and 9 defined preferred embodiments of the process of claim 7. Claim 11 restricted the viscosity ratio of the composition of claim 10. Claims 13-15 defined preferred embodiments relating to the nucleating agent.

II. Opposition against the grant of the patent was filed on 3 April 1997 by BASF AG. The opposition was subsequently transferred to Novolen Technology Holdings C.V. as a consequence of a transfer of business assets from BASF AG, the transfer taking effect from 3 December 2001.

The opposition was based on the grounds pursuant to Article 100(a) EPC, specifically that the subject matter claimed was neither novel nor founded on an inventive step.

The opposition relied inter alia on the following prior art citations:

D4: JP-A-146 953/88 (Considered in the form of an English translation)

D11: R. Greco et al. "Polyolefin blends: 2. Effect of EPR composition on structure, morphology and mechanical properties of iPP/EPR alloys"; Polymer 28 (1987) pp 1929-1936.

III. In a decision announced orally on 19 May 2003 and issued in writing on 17 October 2003 the opposition division held that the patent could be maintained in amended form on the basis of a main request of 15 claims filed with a letter dated 14 March 2003.

The claims according to this request differed from those as granted in that claim 1 specified the content of copolymer phase (10-50% by weight based on the total composition) and further specified the content of ethylene in the copolymer phase (35 to 75% by weight).

The decision under appeal held that the claims of this request met the requirements of Articles 123(2) and (3) EPC.

Novelty was acknowledged since it was held that the disclosure in D4 of an ethylene content of the copolymer component of 20-80 weight % was too vague to anticipate the content of 35-75 weight % ethylene claimed.

It was further held that the content of ethylene in the copolymers of the examples of D4 could not be derived by reference to impact strength data in D11, as had been submitted by the opponent.

With regard to inventive step, the problem to be solved was formulated, in accordance with page 2, lines 3, 4 and 40-44 of the patent in suit as being to provide compositions having improved resistance to stress whitening as well as good impact strength.

D4 was the closest prior art. This document was not concerned with said problem, the underlying problem of D4 being to provide compositions excellent in impact resistance, rigidity and flowability. The narrower range of the comonomer content of the copolymer component, compared to D4, was considered, together with the other parameters chosen, to contribute to the solution of said problem and the effect of the selection to be surprising and hence to support the presence of an inventive step.

IV. An appeal against this decision was filed by the opponent on 16 December 2003, the requisite fee being paid on the same date. It was requested that the decision under appeal be set aside and the patent revoked.

V. Together with the statement of grounds of appeal, received on 27 February 2004 the appellant introduced a further document:

D12: EP-A-433 990. This was prior art pursuant to Article 54(3) EPC for the contracting states BE, DE, ES, FR, GB, IT and NL.

(a) With regard to novelty, it was argued that the subject matter of claim 1 as maintained by the opposition division was anticipated by the disclosure of examples 2-5 of D12. Further objections of lack of novelty based on D12 were raised in respect certain of the other claims. It was further submitted that the subject matter claimed lacked novelty in view of the disclosure of D4. Although D4 did not disclose the content of ethylene in the copolymer, this information could be derived from the Tg values reported in D4 with reference to the information contained in D11. D11 concerned copolymers prepared using catalysts comparable to those employed in D4. From the data in D11 relating the Tg values of the copolymers to the monomer compositions thereof it was possible to ascertain the monomer compositions of the copolymers of D4.

(b) Regarding inventive step it was submitted that D4 represented the closest prior art. This was held to disclose copolymers having an ethylene content between more than 20 weight % and less than 35 weight %. Such compositions would be understood to have lower impact strength and probably improved stiffness and stress whitening resistance as compared to the compositions of the patent in suit. From D11 it was known that poor impact strength was a consequence of a lower ethylene content of the copolymer phase. It would be recognised that the impact strength of the compositions of D4 at an ethylene level of 20-35 weight % was insufficient. It would be immediately apparent to address this problem by using an ethylene-propylene copolymer having an ethylene content in the upper region of the range of 20 to 80 wt% disclosed in D4.

VI. The respondent (patentee) submitted, together with the response received on 6 August 2004, further sets of claims forming a main and a first and second auxiliary request. It was requested that the decision under appeal be set aside and the patent maintained on the basis of said main request, in the alternative, on the basis of the first or second auxiliary requests.

(a) Claim 1 of the main request corresponded to claim 1 as upheld by the opposition division, but modified by introduction of four disclaimers to take account of examples 2-5 of D12.

Independent claim 3 of the main request corresponded to claim 1 as upheld by the opposition division with the additional feature that a nucleating agent be present. This claim did not contain disclaimers. The main request further contained an independent claim 17 directed to a process for preparing a polypropylene impact composition having the product features of claim 1 as upheld by the opposition division together with process features essentially corresponding to those of claim 7 as granted. Further, four claims dependent thereon were proposed. A claim corresponding to granted independent claim 10 was not present.

(b) The respondent submitted that the newly filed claim 1 was novel with regard to D12 due to the disclaimers. The subject matter of claim 3, which did not contain the disclaimers, was not anticipated since D12 did not disclose the presence of nucleating agents. Process claim 17 was novel since D12 related to a slurry process, not a gas phase process as defined. With regard to the objection based on D4 and D11, the respondent submitted that the correlation between Tg and ethylene content relied upon was invalid. In this respect reference was made to differences in the process conditions (temperature, solvent) and the fact that in D4 the copolymer was prepared in the presence of the propylene homopolymer whereas in D11 the copolymer was prepared in the absence of any polypropylene. Further the Tg reported in D11 related only to the ethylene-propylene copolymer while that reported in D4 concerned the composition of ethylene-propylene copolymer together with the polypropylene phase. Regarding inventive step, the finding that D4 represented the closest prior art was not challenged. It was disputed that D4 and D11 would be combined as proposed by the appellant. D4 referred to composition obtained by in situ polymerisation, the copolymer being prepared in the presence of the homopolymer whereas D11 related to blends of the components. The problem underlying the patent in suit was to improve resistance to stress whitening, which problem was not addressed in D4. It had not been explained why the compositions of D4 would be expected to have improved stress whitening.

VII. The board issued on 25 January 2006 a summons to oral proceedings. In a communication from the board dated 31 January 2006 the provisional view was expressed that the disclaimers with respect to D12 had been correctly formulated. With regard to the newly introduced process claims it was indicated that the admissibility of these would have to be examined with regard to the requirement of Article 123(3) EPC and also with respect to the prohibition of reformatio in peius since the patent proprietor was not an appellant.

The board provisionally considered that the novelty objection based on a correlation of data between D4 and D11 was not valid.

With regard to those claims lacking the disclaimers but specifying the presence of a nucleating agent it was noted that according to D11 the ethylene-propylene copolymer component could itself exhibit nucleating activity. Hence it would be necessary to examine whether this feature could confer novelty with respect to D12.

With regard to the restriction of the content of ethylene in the copolymer, and in view of the case law developed with regard to selection inventions, it was stated that it would be necessary to examine whether this feature could confer novelty with respect to the broader range disclosed in D4.

With regard to inventive step it was noted that since the patent in suit identified the intrinsic viscosity (hereinafter "IV") ratio as significant for attaining the desired improvement in stress whitening, and in view of the fact that this ratio was exhibited by some of the compositions of D4, this problem had potentially already been solved in the prior art, meaning that a different technical problem would have to be formulated.

VIII. The respondent submitted in a letter dated 3 March 2006 further sets of claims forming a main and nine auxiliary requests. A further document was submitted:

D13: Ser van der Ven, "Polypropylene and other Polyolefins, Polymerization and Characterization"; Studies in Polymer Science 7. Elsevier, Amsterdam, 1990, pp. 317-321.

(a) Claim 1 of the main request read as follows:

"1. A polypropylene impact composition which comprises a homopolymer phase predominantly comprising a propylene homopolymer and from 10% to 50% based on the weight of the total impact copolymer composition of a copolymer phase predominantly comprising a copolymer of ethylene and propylene wherein the copolymer phase contains from 35 to 50% by weight of ethylene based on total copolymer phase, and wherein the ratio of the intrinsic viscosity of the copolymer phase to that of the homopolymer phase is from 1.0/1 to 1.3/1, the intrinsic viscosities being determined according to ASTM D 1601-78 in decalin at 135ºC, that of the copolymer phase ([eta]copol) being derived from the intrinsic viscosity of the composition ([eta]prod) in accordance with the formula

FORMULA/TABLE/GRAPHIC

where ([eta]homo) is the intrinsic viscosity of the homopolymer phase and Fc is the fraction of the composition which is copolymer; with the proviso that the composition does not consist of 72 weight percent of a propylene homopolymer phase containing 0.5 weight percent ethylene and having an intrinsic viscosity of 1.87 dl/g and 28 weight percent of a propylene copolymer phase containing 39 weight percent of ethylene and having an intrinsic viscosity of 2.16." Dependent claim 2 specified the composition according to claim 1 further comprising a nucleating agent, corresponding to granted claim 12, cited in section I above. Independent claim 3 corresponded to claim 1, with the difference that instead of the disclaimer the final phrase of the claim read:

where ([eta]homo) is the intrinsic viscosity of the homopolymer phase and Fc is the fraction of the composition which is copolymer; with the proviso that the composition does not consist of 72 weight percent of a propylene homopolymer phase containing 0.5 weight percent ethylene and having an intrinsic viscosity of 1.87 dl/g and 28 weight percent of a propylene copolymer phase containing 39 weight percent of ethylene and having an intrinsic viscosity of 2.16." Dependent claim 2 specified the composition according to claim 1 further comprising a nucleating agent, corresponding to granted claim 12, cited in section I above. Independent claim 3 corresponded to claim 1, with the difference that instead of the disclaimer the final phrase of the claim read:

"and wherein the polypropylene impact composition further comprises a nucleating agent". Claims 4 and 5 specified restrictions with respect to the content, in ppm, of nucleating agent in the compositions of claims 2 and 3. Claim 6 specified that the nucleating agent in the compositions according to claims 2 to 5 was sodium benzoate. Claims 4 to 6 corresponded to the granted claims 13 to 15 respectively. Claim 7 specified that the homopolymer phase could contain up to 6.0 weight percent ethylene, corresponding to granted claim 4. Claim 8 restricted the IV ratio to 1.0/1 to 1.2/1, corresponding to granted claim 5.

Claims 9 and 10 corresponded to the granted claims 6 and 7, cited in section I above. Claim 11, dependent on claim 10, specified that both stages be conducted in the presence of a fluidized bed olefin polymerization catalyst, corresponding to granted claim 8. Claim 12, dependent on claims 10 or 11 specified the addition of molecular hydrogen to control the molecular weight corresponding to granted claim 9. Claims 13 and 14 corresponded respectively to granted claims 10 and 11. Claim 15 corresponded to granted claim 16 cited in section I above. Independent process claim 16 read as follows: "16. A process for preparing a polypropylene impact composition which comprises a homopolymer phase predominantly comprising a propylene homopolymer and from 10% to 50% based on the weight of the total impact copolymer composition of a copolymer phase predominantly comprising a copolymer of ethylene and propylene wherein the copolymer phase contains from 35 to 50% by weight of ethylene based on total copolymer phase, and wherein the ratio of the intrinsic viscosity of the copolymer phase to that of the homopolymer phase is from 1.0/1 to 1.3/1, the intrinsic viscosities being determined according to ASTM D 1601-78 in decalin at 135ºC, that of the copolymer phase ([eta]copol) being derived from the intrinsic viscosity of the composition ([eta]prod) in accordance with the formula:

FORMULA/TABLE/GRAPHIC

where ([eta]homo) is the intrinsic viscosity of the homopolymer phase and Fc is the fraction of the composition which is copolymer;

wherein a two-stage gas-phase polymerization process is carried out wherein predominantly propylene is initially polymerized to form the homopolymer phase and the product of the initial polymerization is contacted with a mixture of propylene and ethylene to form the copolymer phase, the polymerizations being conducted in the presence of an olefin polymerization catalyst and the molecular weight of at least one of the homopolymer phase and the copolymer phase being controlled to provide said intrinsic viscosity ratio."

The dependent process claims 17-20 specified the same features as claims 11-14 of the main request (indicated above), however in relation to the process of claim 16.

(b) The submissions of the respondent may be summarised as follows:

(i) A procedural request for remittal of the case to the opposition division was made for the case that the board should consider the introduction of process claims not appropriate. With respect to the prohibition of reformatio in peius it was submitted that the amendments made were a consequence of the citation of D12, of which it had only been possible to take account at the appeal stage since it had not been cited previously. Hence the introduction of process claims should be permitted.

(ii) With regard to the requirements of Article 123(3) EPC in respect of the process claims, it was argued these were derived inter alia from composition claims defining process features and thus should properly be read as product by process claims. Carrying out this process would necessarily result in a composition within the scope of granted claim 1, meaning there was no increase in the scope of protection.

(iii) With regard to the question of whether the presence of a nucleating agent would confer novelty, it was submitted that the wording of the claims, in particular the word "further" indicated that this was not a component intrinsic to the composition but an additional component to the previously recited components, added after formation of the composition.

(iv) With regard to D4, it was argued that the requirements for novelty based on the criteria for a selection were met with regard both to the general disclosure and with regard to the examples thereof.

Compared to the general disclosure of D4 it was argued that selections had been made at least with respect to the disclosures of the ethylene content of the copolymer component of 20 to 80% and of the IV ratio of 0.5/1 to 2.0/1. Neither of the claimed ranges of these parameters, which required an IV ratio of 1.0/1 to 1.3/1 and a copolymer phase ethylene content of 35 to 50 % by weight was disclosed individually, let alone in combination.

With respect to the examples of D4, in particular the ethylene content of the copolymer, it was argued, with respect to the data in Table 6.3 of D13 which showed values of Tg for a homologous series of block copolymers differing only in rubber fraction ethylene content that the Tg values of -20 to -44ºC reported in the table of D4 corresponded to an ethylene comonomer content of around 80% or higher or around 20% or lower, showing that the examples of D4 did not anticipate the ethylene content defined in the claims.

It was further argued, with respect to the examples, that the requirements for a novel selection were also met since the claimed range of ethylene content of 35 to 50 wt% spanning a range of 15 wt% was narrow compared to the disclosure of 20-80 wt% in D4, spanning a range of 60 wt%. The claimed range was also far removed from the end points of the known range (20 and 80 wt%). The evidence of samples 6 and 8 of the patent in suit established that the claimed range of ethylene content was not an arbitrarily chosen specimen but made a technical contribution since it resulted in an improvement in stress whitening resistance.

(v) With regard to inventive step, it was argued that D4 failed to teach anything about stress whitening. The IV ratio alone was not sufficient to achieve this - other parameters, in particular the ethylene content had to be controlled as illustrated by samples 6 and 8 of the patent.

IX. Oral proceedings were held before the board on 5 April 2006.

(a) With regard to the formulation of the claims with respect to Article 123 EPC and the prohibition of reformatio in peius:

(i) The appellant acknowledged that the claims according to the main request, including process claim 16, did not result in an increase of the scope of protection as compared to the claims upheld by the opposition division. It was submitted that the respondent was employing three alternative "approaches" to address the issues arising from citation of D12 - introduction of a disclaimer (claim 1), introduction of a further feature (claim 3) or formulating process claims (claim 16). A single one of these - the route represented by claim 1 - would however be sufficient to overcome the objections. There was a contradiction between claims 1 and 16 since a product excluded from the scope of claim 1 by a disclaimer was encompassed by claim 16.

(ii) The respondent submitted a new main request to the effect that the case be remitted to the opposition division in order that the issues arising from the citation of D12 could be dealt with by the first instance. The remaining requests were upheld, it however being indicated in general terms that it was intended to modify and/or reorder certain of the auxiliary requests.

(b) Regarding novelty,

(i) With respect to the ethylene content of the copolymer employed in D4 the appellant submitted that it was not possible to derive this by correlation of the reported Tgs with those disclosed in D13. The respondent stated that this conclusion applied equally to D11.

(ii) With regard to the issue of novelty by selection, and the content of ethylene in the copolymer, the appellant submitted that samples 5 and 6 of Example 1 of the patent in suit showed that the ethylene content had no effect on stress whitening. D4 taught that an IV ratio of around unity was required. Although D4 was silent on stress whitening, it was possible that the compositions had this property.

The respondent observed that the samples 5 and 6 invoked by the appellant had different IV ratios, invalidating the comparison. Two factors were important for attaining good stress whitening - the IV ratio and the content of ethylene in the copolymer as could be derived from the examples of the patent in suit.

The respondent further submitted that D4 disclosed a broader range of IV ratios than defined in the patent in suit, and taught only that this ratio should get closer to unity. Most examples of D4 had IV ratios outside the range now claimed. Stress whitening was not even mentioned in D4. The claimed subject matter represented a selection from two lists - one selection in respect of the IV ratio and the other in respect of the ethylene content.

(iii) With regard to the issue of the nucleating agent, the respondent referred to the written submissions relating to the meaning of "further comprises". The statement in D11 regarding the nucleating effect of the ethylene/propylene copolymer represented an inference or a theory, but was not presented as a fact. This theory had since been discredited.

(c) Regarding inventive step, the appellant submitted that since the IV ratio was disclosed in D4 the problem of reducing stress whitening had already been solved. The technical problem as set out in the patent was therefore not correct. The only distinction with regard to D4, the ethylene content of the copolymer phase, had not been shown to give rise to any technical effect. The skilled person would be attracted to D4 by the reported properties. In repeating this teaching inevitably a composition in the central part of the disclosed range would be employed. If problems with stress whitening arose, further experiments would be carried out. It would be found that the best results were obtained in the central part of the range.

The respondent submitted that a novel technical effect over D4 had been shown. D4 contained no information about stress whitening. The examples of D4 could not be repeated as certain data - the ethylene content of the copolymer phase - was lacking. D4 contained no teaching that balancing the IV ratio and ethylene content of the copolymer would lead to improved stress whitening. There was no motivation to carry out any modification of the composition of D4 to improve stress whitening.

X. The final requests of the parties were:

The appellant (opponent) requested that the decision under appeal be set aside and that the European patent No. 457 455 be revoked.

The respondent (patentee) requested that the decision under appeal be set aside and the case remitted to the first instance for further prosecution or in the alternative that the patent be maintained on the basis of the main request or the first to ninth auxiliary requests filed with the letter dated 3 March 2006.