T 0868/09 27-03-2012
Download und weitere Informationen:
Process for producing a polyethylene coating on a substrate
Late submitted material - admitted (no)
Inventive step - (second and third auxiliary requests) - (no)
Summary of Facts and Submissions
I. The appeal by the patent proprietor lies against the decision of the opposition division announced on 21 January 2009 and posted 20 February 2009 according to which European patent EP-B1 1 265 959 (application number 01 911 780.3) could be maintained in amended form on the basis of the third auxiliary request.
II. The patent as granted had 17 claims whereby independent claim 1 was directed to a process for coating a substrate, claims 2-14 being dependent on claim 1.
Claim 15 was directed to an extrusion coating structure provided on a substrate and read as follows:
"An extrusion coating structure provided on a substrate comprising at least one layer of bimodal polyethylene composition, characterized in that the composition is produced by
- subjecting ethylene, optionally with hydrogen and/or comonomers to polymerization or copolymerization reactions in a multistage polymerization sequence of successive polymerization stages;
- carrying out the polymerization reactions in the presence of a single-site catalyst capable of forming a composition comprising
- a low molecular weight component with a MFR2 of 20g/l0min or more and a density higher than the density of the composition, and
- a high molecular weight component, said composition having a melt flow rate MFR2 of 5g/l0min or more and a density of 915 - 960 kg/m**(3);
said layer of bimodal polyethylene composition exhibiting
- a tensile strength machine/transverse direction of 20/20 MPa or more,
- tear strength machine/transverse direction of 1.0/1.5 MPa or more, and
- puncture strength of 900 N/mm or more, preferably 1000 N/mm or more."
Claims 16 and 17 were dependent on claim 15.
III. A notice of opposition was filed on 1 February 2006, invoking the grounds pursuant to Art. 100(a) EPC (lack of novelty, lack of inventive step). The opposition was supported by the following document:
D1: WO-A-98/30628.
During the oral proceedings before the opposition division the opponent additionally invoked the ground of opposition pursuant to Art. 100(b) EPC (insufficiency of disclosure).
IV. The decision of the opposition division was based on the claims of the patent as granted as the main request and three auxiliary requests. According to the decision the main request (claims of the patent as granted) did not meet the requirements of Art. 54 EPC, the first and the second auxiliary requests did not meet the requirements of Art. 56 EPC whereas the third auxiliary request was held to meet the requirements of the EPC. The ground of opposition pursuant to Art. 100(b) EPC, invoked by the opponent at the oral proceedings, was admitted to the proceedings.
V. The opponent lodged an appeal against the decision on 20 April 2009, the prescribed fee being paid on the same day. The statement of grounds of appeal was filed on 22 June 2009. A further submission was filed with a letter dated 23 November 2010.
VI. The respondent (patent proprietor) made written submissions with letters dated 17 June 2009 and 23 December 2009, the latter containing two new auxiliary requests designated 1 and 2.
VII. On 5 October 2011 the Board issued a summons to attend oral proceedings on 27 March 2012. In a communication the Board set out its preliminary opinion and expressed its view on the interpretation of the claims, in particular relating to the meaning of "... catalyst capable of ..." and the (lack of) relationship between the composition used to define the catalyst and the composition used to form the coating. As final date for the filing of any further submissions 27 February 2012 was set.
VIII. By letter dated 29 February 2012, received on equal date, the respondent filed three sets of claims designated main request and first and second auxiliary requests. It was stated that two claim sets were filed as an amended main request and an amended first auxiliary request. It was also indicated that the claim set designated "1st auxiliary request" filed with the letter of December 23, 2009 was maintained as the 2nd auxiliary request. However no comments were given regarding the set of claims bearing the legend "2nd Auxiliary Request" submitted with letter of 29 February 2012. The respondent was also silent regarding the set of claims designated "2nd second auxiliary request" filed with letter dated 23 December 2009.
Claim 1 of the main request read as follows (additions compared to claim 15 as granted indicated in bold, deletion by [deleted: strikethrough ]by the Board):
"An extrusion coating structure provided on a substrate comprising at least one layer of bimodal polyethylene composition, characterized in that the composition is produced by
- subjecting ethylene, optionally with hydrogen and/or comonomers to polymerization or copolymerization reactions in a multistage polymerization sequence of successive polymerization stages;
- carrying out the polymerization reactions in the presence of a single-site catalyst capable of forming a composition comprising
- a LMW [deleted: low molecular weight ]component with a MFR2 of 20g/l0min or more and a density higher than the density of the composition, and
- a HMW [deleted: high molecular weight ]component said composition having a [deleted: melt flow rate ]MFR2 of 5g/l0min or more and a density of 915 to 960 kg/m**(3);
wherein the active complex of said single-site catalyst has the general formula
(X1)(X2)Hf(Cp-R1)(Cp-R2)
wherein
X1 and X2 are the same or different and selected from the group comprising halogen, methyl, benzyl and hydrogen;
Hf is hafnium;
Cp is a cyclopentadienyl group; and
R1 and R2 are the same or different and stand for linear and branched hydrocarbyl groups containing 1-10 carbon atoms.
or wherein the single-site catalyst is based on a siloxy-substituted bridged bis-indenyl zirconium dihalide;
and whereby said bimodal polyethylene composition comprises a low molecular weight component in an amount of 60 to 40 wt.-% and a high molecular weight component in an amount of 40 to 60 wt.-%,
said layer of bimodal polyethylene composition exhibiting
- [deleted: a ]tensile strength machine/transverse direction of 20/20 MPa or more,
- [deleted: a ]tear strength machine/transverse direction of 1.0/1.5 MPa or more, and
- puncture strength of 900 N/mm or more, preferably 1000 N/mm or more."
[deleted: ]
Claim 1 of the first auxiliary request differed from the main request in that the catalyst was specified as being a single site metallocene catalyst and in that the mode of carrying out the polymerisation reactions contained additional features, reading as follows (additions compared to the main request indicated in bold by the Board):
"...
- carrying out the polymerization reactions in the presence of a single-site metallocene catalyst capable of forming a composition comprising
- a LMW component with a MFR2 of 20g/10min or more and a density higher than the density of the composition when polymerized
- in a slurry reactor
- for at least 10 minutes
- at a hydrogen-to-ethylene feed ratio between 0.1-0.5 kg of hydrogen/ton of ethylene
- at supercritical conditions at temperatures over 90ºC
- at a pressure of 25 to 100 bar
- whereby 40-60 wt-% of the whole composition is formed in the slurry reactor and
- a HMW component when polymerized in a
- gas phase reactor
- the molar ratio of hydrogen to ethylene in the reactor being lower than 0.6 mol/kmol
- the gas phase reactor being operated in the temperature range of 50 to 115ºC and
- the reaction pressure between 10 and 40 bar and
- the partial pressure of ethylene between 1 and 20 bar
- whereby 60-40 wt-% of the whole composition is formed in the gas phase reactor
said composition having a MFR2 of 5g/l0min or more and a density of 915 to 960 kg/m**(3). ..."
Claim 1 of the second auxiliary request - filed as the first auxiliary request with the response to the statement of grounds of appeal - read (additions compared to claim 15 as granted indicated in bold by the Board):
"An extrusion coating structure provided on a substrate comprising at least one layer of bimodal polyethylene composition, characterized in that the composition is produced by
- subjecting ethylene, optionally with hydrogen and/or comonomers to polymerization or copolymerization reactions in a multistage polymerization sequence of successive polymerization stages;
- carrying out the polymerization reactions in the presence of a single-site metallocene catalyst capable of forming a composition comprising
- a low molecular weight component with a MFR2 of 20g/l0min or more and a density higher than the density of the composition, and
- a high molecular weight component, said composition having a melt flow rate MFR2 of 5g/l0min or more and a density of 915 to 960 kg/m**(3);
whereby said bimodal polyethylene composition comprises the low molecular weight component in an amount of 60 to 40 wt.-% and the high molecular weight component in an amount of 40 to 60 wt.-%,
said layer of bimodal polyethylene composition exhibiting
- [deleted: a ]tensile strength machine/transverse direction of 20/20 MPa or more,
- [deleted: a ]tear strength machine/transverse direction of 1.0/1.5 MPa or more, and
- puncture strength of 900 N/mm or more, preferably 1000 N/mm or more."
Claim 1 of the 2nd Auxiliary Request filed with letter of 29 February 2012 was identical to Claim 1 of the set of claims filed as the first auxiliary request with the response to the statement of grounds of appeal.
Claim 1 of the third auxiliary request - filed as the second auxiliary request with the response to the statement of grounds of appeal of 23 December 2009 read as follows (additions compared to claim 15 as granted indicated in bold by the Board; deletions as [deleted: strikethrough ]):
"An extrusion coating structure provided on a substrate comprising at least one layer of bimodal polyethylene composition, characterized in that the composition is produced by
- subjecting ethylene, optionally with hydrogen and/or comonomers to polymerization or copolymerization reactions in a multistage polymerization sequence of successive polymerization stages;
- carrying out the polymerization reactions in [deleted: the ]presence of a single-site catalyst capable of forming a composition comprising
- a low molecular weight component with a MFR2 of 20g/l0min or more and a density higher than the density of the composition, and
- a high molecular weight component,
said composition having a melt flow rate MFR2 of 5g/l0min or more and a density of 915 to 960 kg/m**(3);
whereby said bimodal polyethylene composition comprises the low molecular weight component in an amount of 60 to 40 wt.-% and the high molecular weight component in an amount of 40 to 60 wt.-%, and whereby
- ethylene, optionally with hydrogen and/or comonomers is subjected to a first polymerization or copolymerization reaction in the presence of the single-site catalyst in a first reaction zone or reactor to produce a first polymerization product with an MFR2 of 20 g/10 min or more;
- recovering the first polymerization product from the first reaction zone;
- feeding the first polymerization product to a second reaction zone or reactor;
- feeding additional ethylene and, optionally, comonomers to the second reaction zone;
- subjecting the additional ethylene and optionally additional monomer(s) and/or hydrogen to a second polymerization reaction in the presence of the single-site catalyst and the first polymerization product to produce a second polymerization product having MFR2 of 5 g/10 min or more; and
- recovering the combined polymerization product from the second reaction zone;
wherein no fresh catalyst is added to the second polymerization stage; said layer of bimodal polyethylene composition exhibiting
- [deleted: a ]tensile strength machine/transverse direction of 20/20 MPa or more,
- [deleted: a ]tear strength machine/transverse direction of 1.0/1.5 MPa or more, and
- puncture strength of 900 N/mm or more, preferably 1000 N/mm or more."
IX. By letter dated 16 March 2012 the respondent stated that it would not attend the oral proceedings. In a further letter dated 20 March 2012 the respondent submitted further amendments.
X. By letter dated 22 March 2012 the appellant stated that it, too, would not attend the oral proceedings and submitted further substantive arguments with respect to the newly filed requests.
XI. Oral proceedings were held on 27 March 2012. As previously notified neither party attended.
XII. The arguments of the appellant can be summarised as follows.
(a) Novelty of the product features of the subject - matter of claim 1 of the main request was accepted.
(b) Only the product features of claim 1 of the main request should be taken into account when assessing inventive step. The features relating to the catalyst did not relate to the product per se and the restriction imposed thereby was unclear. The feature "single site catalyst" did not represent a distinguishing feature compared to the closest prior art D1.
The mechanical properties specified could not render the claimed subject-matter inventive since either these were the inevitable consequence of the composition claimed or, if this were not the case, then the claim would lack sufficiency, since it was not taught how to obtain the specified composition except when using specific single site catalysts so that the claim covered embodiments for which there was no enabling disclosure. Furthermore these mechanical properties were nothing more than desiderata, meaning that in effect the claim related to an obvious composition whereby an attempt had been made to distinguish it from the prior art by adding some desirable properties.
The specified ratio of high molecular weight and low molecular weight compositions had to be regarded as the "default" ratio for any composition without a specific teaching to the contrary. Hence the skilled person would automatically select such a range. No evidence had been advanced that this range gave rise to any technical effect and even if it had this would have to be seen as a "bonus" effect of an obvious feature.
XIII. The arguments of the respondent can be summarised as follows:
Main request
Art. 123(2) EPC: Claim 1 of the new main request found its basis in original claim 15 combined with the passages beginning on page 3, line 30, page 4, line 14, page 7, line 6. The features relating to the definition of the catalyst were based on original claim 8, page 5, line 30 - page 6 line 9 and page 6, lines 11-14 of the description.
First auxiliary request
Art. 123(2) EPC: The respondent provided a table indicating the basis of the features of this claim in the application as filed, showing claim 15 as the basis, supplemented with 15 features recruited from several passages found on pages 9, 10 and 11 of the application as filed.
Second auxiliary request
(filed as first auxiliary request with submission dated 23 December 2009)
(a) Art. 123(2) EPC: The basis for the feature "single-site metallocene catalyst" was to be found in claim 5 of the application as originally filed.
(b) Art. 54 EPC: Novelty was established not only by the ratio of low and high molecular weight components and the physical properties, but essentially due to the single site metallocene catalysts capable of forming a composition having the properties indicated in the claim. These features were not disclosed in D1. The use of any single site catalyst did not necessarily yield the bimodal compositions as required by claim 1, which some metallocene catalysts were not able to produce, as explained in paragraph [0025] of the patent in suit. The ratio of high and low molecular weight components was not arbitrary but was a preferred range as explained in paragraph [0051] of the patent in suit. This ratio influenced the rheological properties of the composition.
(c) Art. 56 EPC: The subject matter of claim 1 was distinguished by the structure arising from the use of a single site catalyst and the ratio of high and low molecular weight fractions. The evidence present in the patent in suit showed the effect arising from these features. The objective technical problem was to provide a product having improved tensile strength, tear strength, burst force and lower hot tack temperatures. There was no incentive in D1 to employ a single-site catalyst, let alone a specific such catalyst, yielding the low and high molecular weight components as defined. It was necessary to select a single site catalyst capable of providing a high density low molecular weight component and a low density high molecular weight component. Paragraph [0025] of the patent reported that there also existed unsuitable metallocene catalysts.
Third auxiliary request
(filed as 2nd auxiliary request with the submission dated 23 December 2009)
(a) Art. 123(2) EPC: the basis for the catalyst feature was given as page 5, lines 21-22 of the application as filed.
(b) Art. 54 and 56 EPC: the respondent did not provide submissions specifically with respect to this request, but treated this together with the aforementioned request.
XIV. The appellant requested that the decision under appeal be set aside and that the patent be revoked.
The respondent requested that the decision under appeal be set aside and the patent be maintained on the basis of the claims according to the main request, or alternatively on the basis of the claims according to the first, second or third auxiliary request whereby the main request and first and second auxiliary requests had been filed with the submission dated 29 February 2012 and the third auxiliary request had been filed with the letter of 23 December 2009 (response to the statement of grounds of appeal) as the second auxiliary request (see point 2.3 below).
Reasons for the Decision
1. The appeal is admissible.
2. Procedural matters
2.1 The submission dated 20 March 2012 was filed
- significantly after the final date set by the Board,
- only a week before the oral proceedings, and
- after the respondent had stated that it would not attend the oral proceedings.
Therefore the Board has elected to exercise its discretion not to admit it to the proceedings (Art. 114(2) EPC).
2.2 In the communication accompanying the summons to oral proceedings the Board set a final date of 27 February for the filing of further submissions. The respondent however filed amended claims with a letter dated 29 February 2012, i.e. two days after the final date set. No explanation or justification for failing to observe the time limit set by the Board was advanced. Therefore, the applicable criteria are those as set out in the case law discussed in section VII.E.16.1.1 of the "Case Law of the Boards of Appeal of the European Patent Office", 6th Edition, 2010 and in particular T 153/85, OJ EPO 1988, 001, section 2.1 of the reasons.
From the information supplied by the respondent, it appears that the respective claims 1 of the main request and first auxiliary request rely on features recruited from various different parts of the description so that the requirements of Article 123(2) EPC do not appear to be fulfilled. Also, the amendments do not answer the observations the Board made in its communication dated 5 October 2011 regarding the interpretation of the claims and its consequences for novelty and inventive step.
In view of the above, the claims of the main and first auxiliary request are not prima facie clearly allowable and, as a consequence, not admitted to the proceedings.
2.3 Second auxiliary request filed with submission of 23 December 2009
With letter of 29 February 2012 the respondent filed new requests, denoted as main, 1st auxiliary and 2nd auxiliary requests. In the letter reference was made to "amended main request" and "amended 1st auxiliary request". The claims denoted as 1st auxiliary request then on file were stated to be maintained as the 2nd auxiliary request. Therefore, there can be no doubt of the respondent's intention to replace the main and first auxiliary request then on file by the amended ones and to maintain the then 1st auxiliary request as 2nd auxiliary request, which is confirmed by the fact that claim 1 of the 2nd auxiliary request of 29 February 2012 is identical to that of the first auxiliary request of 23 December 2009. However, the respondent did not indicate the fate of the previously filed second auxiliary request. Since that request had not been explicitly withdrawn, it has to be assumed that the request was also maintained, to be renumbered to the third auxiliary request.
3. As a result, the present decision concerns the second and the third auxiliary requests filed as first and second auxiliary requests, respectively, with letter dated 23 December 2009.
4. Second auxiliary request
4.1 Art. 123(2) EPC
The subject matter of claim 1 is derived from:
- originally filed claim 15
- page 11, lines 26 and 27 (proportion of high and low molecular weight components)
- Claim 5 (the feature that the catalyst is a metallocene single site catalyst).
The passage on page 11 is formulated in general terms and applies to the product as such. Hence this passage may be combined with the other amendments.
Claims 2 and 3 correspond to originally filed claims 16 and 17.
The subject matter of claim 1 is restricted compared to claim 15 as granted due to the specification of the proportions of high and low molecular weight components.
Accordingly the Board considers that the requirements of Art. 123(2) and (3) EPC are satisfied.
4.2 Interpretation of the claims
4.2.1 Claim 1 is directed to an extrusion coating structure provided on a substrate comprising at least one layer of bimodal polyethylene composition whereby the composition is characterised in that "it is produced by" a certain process.
It is established case law (Case Law, supra, section II.B.6, in particular decision T 0411/89, points 2.1 and 2.2 of the reasons) that such wording is to be interpreted only to the extent that the product is "producible" or "obtainable" by such a process in so far as the process does not lead to recognisable differences in the product. Since the patent in suit gives no indication that different process features would lead to different product properties, these process features cannot serve to restrict the subject matter of the claim. Hence, the wording "produced by" does not exclude that the product can be obtained by other processes.
4.2.2 It is not possible to derive any details or restriction of the characteristics of the product from the specification of the single site metallocene catalyst in the claim.
This catalyst is characterised only to the extent that it should be "capable" of forming a "composition" having a number of undefined components ("comprising") as well as defined components, namely a low molecular weight component of specified properties, and a high molecular weight component of indeterminate properties and further by the MFR2 and density of that "composition". The definition of those two components is however such that they overlap, i.e. these may be one and the same.
4.2.3 Furthermore, the relationship between the composition used to define the catalyst and the composition that is actually part of the coating structure forming the subject-matter of the claim, is obscure. In particular the wording of the claim imposes no link between the composition which the catalyst is "capable" of forming and that which the extrusion coating of the claim comprises. In other words, it is not a feature of the claim that a composition having the indicated properties which the catalyst - under unspecified conditions - is stated to be "capable" of forming is in fact the composition forming the coating. Nor can this be derived as being mandatory from the part of the description of the patent in suit relating to the catalyst (paragraph [0025]).
Accordingly this aspect of the claim has to be interpreted as defining a bimodal polyethylene composition of unspecified properties which can be - but does not have to be - obtained by polymerisation of the named monomers with a catalyst the nature of which is defined only to the extent that it is a "single-site metallocene" catalyst.
4.2.4 The following phrase of the claim, relating to the proportions of low and high molecular weight component, can be unambiguously interpreted as relating to the components of the bimodal polymer mentioned in the preamble of the claim.
4.2.5 The final part of the claim defines certain physical properties of the layer of bimodal polyethylene composition.
The respondent has advanced no arguments to counter the submissions of the appellant according to which this wording has to be interpreted either as the inevitable outcome of the process by which the product is obtainable, or constitutes merely desiderata.
The Board therefore can identify no reason to conclude that this wording imposes, by itself, any technical limitation on the subject matter of the claim over and above that of the other features thereof.
4.2.6 As a consequence of the above considerations the subject matter of the claim reduces to the following:
- [A coating on a substrate]
- having at least one layer of a bimodal polyethylene composition
- the polyethylene composition having low and high molecular weight fractions in the proportions 60:40 to 40:60.
4.3 Art. 54 EPC
D1 discloses an extrusion coating structure in which at least one layer is made of a polymer composition comprising a multimodal ethylene polymer, which contains from 80 to 100% by weight of ethylene repeating units and from 0 to 20 % by weight C3-10 alpha-olefin repeating units, has a density of between 0.920 and 0.960 g/cm**(3) and which is a blend of at least two different ethylene polymers. According to claims 2 and 3 the ethylene polymer is prepared either in a two step process or by blending at least two ethylene polymers having different average molecular weights. This is also taught starting at page 2 line 11 of D1. According to the passage bridging pages 2 and 3 any kind of ethylene polymerisation catalyst can be used, e.g. Ziegler-Natta or metallocene, whereby the preferred catalyst system is based on a group 4 metal metallocene and alumoxane. On page 4 first complete paragraph it is stated that according to an important embodiment of the invention the multimodal polymer can be prepared by mixing at least two ethylene polymers of different average molecular weight. However neither here nor in the examples are the proportions of high and low molecular weight polymers to be employed specified. Accordingly the requirements of Art. 54 EPC appear to be satisfied.
4.4 Art. 56 EPC
4.4.1 Closest prior art
The patent in suit relates to an extrusion coating structure on a substrate comprising at least one layer of bimodal polyethylene composition. Such coatings are known from D1 which by common consent is the closest prior art. The Board sees no reason to take a different view.
The subject matter of operative claim 1 is distinguished from the teaching of D1 by the proportion of high and low molecular weight polymer fractions (see points 4.2.6 and 4.3 above).
4.4.2 Problem solved
The examples of the patent in suit show a polymer composition prepared using a single site metallocene polymerisation catalyst (examples 1 and 2), a composition of commercial high pressure polyethylene (comparative example 3) and a polymer prepared employing a Ziegler-Natta catalyst (comparative example 4). However there is no example which relates to the proportion of high and low molecular weight components. Accordingly there is no evidence of any effect associated with the distinguishing feature over the closest prior art. Nor does any of the evidence advanced during the opposition proceedings demonstrate any technical effect associated with the distinguishing feature.
Under these circumstances the problem to be solved can only be formulated as to provide a further extrusion coating structure to that known from D1.
4.4.3 Obviousness
In view of the nature of the problem to be solved, any composition within the teaching of D1 represents an obvious solution thereto. D1 even provides a broad indication to the claimed solution since it teaches to use blends of polymers of different molecular weights. Thus the selection of a particular ratio of the two polymers has to be seen, in the absence of evidence of any associated technical effect, merely as a normal course of action within the framework of D1 which the skilled person would not hesitate to consider, and therefore forming an obvious solution to the above-defined technical problem.
Hence the second auxiliary request does not meet the requirements of Art. 56 EPC and is therefore refused.
5. Third auxiliary request
Claim 1 of the third auxiliary request differs from claim 1 of the second auxiliary request only in the details of the catalyst and process. However since these features do not impose any restriction on the subject matter claimed (see point 4.2 above), the subject matter of this request reduces to the same as that of the second auxiliary request.
The same conclusions therefore apply, with the result that the subject-matter of the third auxiliary request also does not meet the requirements of Art. 56 EPC.
The third auxiliary request is therefore refused.
6. Since none of the requests on file is allowable, the patent has to be revoked.
ORDER
For these reasons it is decided that:
1. The decision under appeal is set aside.
2. The European patent No. 1 265 959 is revoked.