T 1585/18 01-03-2021

1. Preliminary remark

1.1 Out of the five requests defended by the appellant during the appeal proceedings four of them (the main and first auxiliary requests submitted with letter dated 27 January 2021 and the main request and first auxiliary requests filed with the statement of grounds of appeal) contain the same product claim 1, while the fifth (the second auxiliary request filed with the statement of grounds) is directed to a process for the preparation of a copolymer whose definition corresponds to that of claim 1 according to the other requests.

1.2 While the respondents objected to the admittance of some of the requests, it was not disputed that at least the second auxiliary request was in the proceedings as it corresponded to a request decided upon in opposition and its admittance was not objected to.

1.3 As the parties confirmed at the oral proceedings before the Board that the same objection of lack of sufficiency of disclosure with the same arguments applied both to process claim 1 of the second auxiliary request and to product claim 1 of the other requests, the Board for reasons of procedural economy found it not necessary to hear the parties on the issue of admittance of the disputed requests before having decided on the issue of sufficiency of disclosure. As the conclusion was reached that all requests do not meet the requirement of sufficiency of disclosure, there is no need to decide on the issue of admittance of the disputed requests and that issue is not dealt with in any further detail in what follows.

1.4 For ease of explanation sufficiency of disclosure of product claim 1 according to the main and first auxiliary requests in both version is dealt with first (section 2, below) and then the validity of the same reasoning for process claim 1 of the second auxiliary request is analysed (section 3, below).

Sufficiency of disclosure

2. Product claim

2.1 Product claim 1 according to the main and first auxiliary requests in both versions (referred to as product claim 1 in what follows) defines a copolymer in terms of both structural features setting out the constituents of said copolymer and parametric requirements relating to the properties of the copolymer (features (a)-(c) and (e)) as well as the impact resistance of a film produced from that copolymer (feature (d)).

2.2 Structurally, the copolymer of product claim 1 is only defined in that it is made of ethylene and an alpha-olefin. There is no further structural definition in claim 1 relating to the choice of the alpha-olefin or to the amount of that comonomer. The claimed copolymer is thus mainly defined by a set of parametric requirements it must fulfill.

2.3 As to this set of parametric requirements, the copolymer of product claim 1 must be such that it has:

(a) a density D in the range 0.915-0.933 g/cm**(3) measured in accordance with ISO 1183-1 (Method A), the sample being prepared by the method disclosed in the examples section,

(b) a melt index MI2 (2.16 kg, l90°C) in the range of 0.3-5 g/10min measured in accordance with ISO 1133,

(c) a melt index MI2 (2.16 kg, 190°C) and Dow Rheology Index (DRI), determined by the method disclosed in the examples section, satisfying the equation [DRI/MI2]>2.65,

(d) a Dart Drop Impact (DDI), as measured by ASTM D 1709-98 (Method A), in g of a blown film having a thickness of 25mym produced from the copolymer satisfying the equation

DDI >= 19000 x {1-Exp[-750(D-0.908)**(2)]} x {Exp[(0.919- D)/0.0045]},

and

(e) a Dow Rheology Index (DRI) in the range 1-15.

2.4 It was undisputed that not all copolymers of ethylene and an alpha-olefin necessarily fulfill the set of parametric requirements defined in that claim and that a number of parameters of the preparation process of the copolymers has to be purposely selected to obtain a copolymer satisfying the parametric requirements (a) to (e) set out in product claim 1. The question of sufficiency of disclosure in the present case is therefore whether the patent in suit provided sufficient guidance for the preparation of copolymers according to product claim 1.

2.5 In accordance with the established jurisprudence of the Boards of Appeal of the EPO, sufficiency of disclosure is to be acknowledged if a skilled person, on the basis of the information provided in the patent specification and, if necessary, using common general knowledge, is able without undue burden, i.e. with reasonable effort, to identify and prepare within the alternatives covered by the very broad structural definition of operative claim 1 those copolymers that fulfill the set of parametric requirements within the whole breadth of the claim (Case Law of the Boards of Appeal, 9th Edition, July 2019, II.C.5.4, in particular decision T 435/91, OJ EPO 1995, 188, Reasons 2.2.1). This reflects the general legal principle whereby the protection sought must correspond to the technical contribution made by the disclosed invention to the state of the art, which excludes the patent monopoly from being extended to subject-matter which, after reading the patent specification, would still not be at the disposal of the skilled person.

2.6 Accordingly, the question to be answered in relation to sufficiency of disclosure is whether the skilled person would have been able to prepare copolymers of ethylene and alpha-olefins which fulfilled the parametric requirements set out in features (a) to (e) as defined in product claim 1 on the basis of the specification and common general knowledge.

2.7 It was not disputed that density and melt index are common properties of this kind of copolymers and that the skilled person would know how to independently vary these two parameters already on the basis of common general knowledge. This cannot however be considered to be the case for the parameters DRI and DDI and the conditions related to them. The conditions related to DRI will be dealt with first.

2.7.1 The meaning of the DRI parameter present in the definitions of features (c) and (e) in product claim 1 is discussed in paragraphs 15 and 99 of the specification. These passages in particular disclose the DRI as being a parameter used to express a polymer's "normalized relaxation time as a result of long chain branching" and DRI is also defined therein as the extent to which the rheology of ethylene-octene copolymers known as ITP incorporating long chain branching into the polymer backbone deviated from the rheology of the conventional linear homogeneous polyolefins that are reported to have no long chain branches by the following normalized equation:

DRI=[365000(tau0/eta0)-1]/10

wherein tau0 is the characteristic relaxation time of the material and eta0 is the zero shear viscosity of the material, the DRI being calculated by least squares fit of the rheological curve (dynamic complex viscosity versus applied frequency eg. 0.01- 100 rads/s) as described in U.S. Pat. No. 6 114 486 with the following generalized Cross equation, i.e.

eta(w)=eta0/[1+(w.tau0)**(n)]

wherein n is the power law index of the material, eta(w) and w are the measured complex viscosity and applied frequency data respectively.

2.7.2 It is apparent from these passages of the specification that the patent in suit indicates a way of determining the DRI of a given ethylene copolymer on the basis of its rheological curve and selected indices. The specification however does not provide an explicit teaching on how an ethylene copolymer having a DRI according to feature (e) and fulfilling the condition set out in feature (c) at the same time must be prepared.

2.7.3 The appellant argued that, in line with paragraphs 15 and 18 of the specification, it was common general knowledge that the DRI was a rheological property related to the processability of the copolymer, meaning ultimately that the DRI could be varied by varying the melt index of the copolymer. The appellant supported that argument by data on melt index and DRI reported in the examples of the patent in suit. In that regard, a comparison of examples 3-6 in Table 2 of the patent in suit shows that ethylene hexene copolymers of melt index (MI2) increasing from 0.35 g/10 min to 0.69 g/10 min displayed a DRI which, in general, increased from 1.8 to 13.6. While that trend appears to be in line with the argument of the appellant, it is apparent that the range of melt indexes covered by the examples only represents a small portion of the range of melt indexes claimed (0.3-5 g/10 min) and there is no indication in the patent in suit that that trend would also be valid for the remainder and largest part of the range of melt index claimed.

2.7.4 Moreover, that consideration raises the question of whether there is sufficient guidance for the preparation of ethylene hexene copolymers having melt indexes chosen in that part of the claimed range (above 0.69 g/10 min and up to 5 g/10 min) and having a DRI that fulfills condition (e) (DRI in the range of 1-15). In particular, since the DRI of the copolymer of example 6 is already 13.6 for a melt index of 0.69 g/10 min, it appears legitimate to assume that following the position of the appellant an ethylene hexene copolymer having a DRI in the range of 1-15 (feature (e)) would not be achievable for a large part of the range of melt indexes.

2.7.5 The specification and the examples of the patent in suit are of little assistance when answering that question. The comparison of the preparation processes used in example 3 and in examples 4-6 relied upon by the appellant implies that the nature of the catalyst used to produce the copolymer may be a relevant factor in adjusting the melt index and the DRI of the copolymer obtained. However, there is no guidance in the specification as to which catalyst must be chosen in the broad class of metallocene catalyst systems disclosed in paragraphs 31-68 of the specification and as to how this choice should be undertaken in order to prepare the copolymers with melt index and DRI in specific ranges. More specifically, the catalyst involved in example 3 (catalyst A) and that used in examples 4-6 (catalyst B) seem to have a significant influence on the DRI of the copolymer (1.8 in example 3 and 9.2-13.6 in examples 4-6). It is however apparent from the description of the preparations of catalysts A and B that they are very similar to one another, the metallocene being the same in both catalyst systems ("complex A", i.e. (C5Me4SiMe2NtBu)Ti(eta**(4)-1,3-pentadiene)), the ionic compound A also being the same and the preparation processes for the catalysts being very similar (paragraphs 88/89 for catalyst A and paragraphs 90/91 for catalyst B). It can only be derived from the description of their preparations in the patent in suit that catalyst A differs from catalyst B in the concentrations of Al and Ti. That alone however does not provide the skilled person with meaningful information as to which modifications of the catalyst are necessary to obtain a DRI and melt index according to operative claim 1. Whether that difference in the catalyst is the sole factor that must be adjusted to produce the significant differences in DRI of the copolymers of example 3 and examples 4-6 is also nowhere discussed in the specification nor derivable from it.

2.7.6 There is further no teaching in the rest of the specification on how to select the catalyst of the copolymerization in order to adjust the melt index and the DRI of the copolymer. In that regard, the Board finds that the experimental evidence relating to the preparation of copolymers of ethylene and hexene present in the patent in suit does not make credible that the selection of the catalyst and/or the adjustment of the melt index of the copolymers would constitute suitable guidance generally applicable to the broad range of copolymers defined in product claim 1, in particular those having a melt index in the range identified above (above 0.69 g/10 min and up to 5 g/10 min) and meeting both conditions on the DRI. On the contrary, the considerations on the examples of the patent in suit constitute verifiable facts that support the existence of serious doubts as to the preparation of copolymers of ethylene and alpha-olefin over the whole scope of product claim 1.

2.7.7 A further parametric requirement of product claim 1 that limits the copolymer of ethylene and alpha-olefin concerns the Dart Drop Impact (DDI) and its relationship with density.

2.7.8 The DDI is, according to product claim 1 as well as paragraph 121 of the specification, a property of the copolymer that is measured on a blown film of a given thickness according to a known standard (ASTM D1709-98 (Method A)). The examples of the patent in suit all show, apart from example 3, the values of DDI (in g) relating to copolymers of ethylene and hexene produced (Table 2). Aside from the examples, the specification does not provide a teaching as to how the DDI characterizing a given ethylene alpha-olefin copolymer can be adjusted. Paragraph 26 of the specification seems to imply that the density of a given copolymer would be a factor when adjusting the DDI (films having a DDI>=1000 g would be obtained for copolymers of densities in the range of 0.9118-0.9248 g/cm**(3)). However, since the range of densities described therein only partially overlaps with the range defined in product claim 1 (0.915-0.933 g/cm**(3)), the Board does not see how that teaching could be of assistance to show that the claimed subject matter was sufficiently disclosed over the whole scope of the claim.

2.7.9 Even if one considers, as it was argued by the appellant on the basis of D19, that the density and the melt index of an ethylene copolymer were known to the skilled person to be the main factors in adjusting the mechanical properties of the copolymer and in some ways therefore the DDI (marked passages in pages 450 and 452 of D19), there is still no guidance on how these parameters of the copolymer can be adjusted such that feature (d) of product claim 1 is fulfilled.

2.7.10 Feature (d) is in the form of a mathematical condition that must be fulfilled and is defined as:

DDI >= 19000 x {1 -Exp[-750(D-0.908)**(2)]} x {Exp[(0.919- D)/0.0045]}

wherein D is the density of the copolymer. The part of the condition that sets out the threshold of DDI as a function of the density of the copolymer can be calculated over the range of densities defined in product claim 1 and has a profile shown as a graph in the figures provided by the appellant (page 3 of the letter of 7 June 2019) and by respondent 2 (page 3 of their rejoinder). The DDI of copolymers of ethylene and hexene are only provided for three examples (examples 4-6) in the patent in suit and the corresponding values are indicated in the figures of the appellant and respondent 2. While the conditions set out in (d) is fulfilled for these examples, the examples cover a small range of densities between 0.9196 and 0.9227 g/cm**(3) and there are no data for densities above that range that are still within the range defined in product claim 1 (0.915-0.933 g/cm**(3)). While the parties submitted different extrapolations as to how the DDI could vary as a function of density for densities in the range of 0.9227 to 0.933 g/cm**(3), these extrapolations do not seem to be based on an established mathematical model and none was provided. What both figures show, however, is that according to the data of the examples a steep decrease of DDI takes place with increasing density. This steep decrease is in accordance with the information available in D19 according to which a seemingly small decrease in density (e.g. 0.005 g/cm**(3)) can dramatically alter mechanical properties and in particular significantly reduce dart impact (page 450, first two sentences of the second full paragraph under "Mechanical Properties"). The data in the examples in the patent together with the information in D19 provide therefore verifiable facts which justify serious doubts on the possibility of meeting the required condition for values of density in the higher part of the range in product claim 1.

2.7.11 In this respect neither the patent in suit nor the common general knowledge made available by the parties provide a reliable teaching from which it could be derived how the skilled person should proceed when adjusting the density and melt index of ethylene alpha-olefin copolymers such that feature (d) could be fulfilled. In that regard, the Board finds that the skilled person did not have sufficient guidance on how to adjust the process of production of the copolymer such that feature (d) was satisfied in particular for values of density in the higher part of the range in product claim 1.

2.7.12 The examples of the patent in suit are of little assistance in that respect. Indeed, while the examples for which a value of DDI was provided (examples 4-6) show that feature (d) was fulfilled, they refer only to the lower part of the density range (D varies between 0.9196 and 0.9227 g/cm**(3) in these examples). No information is available for higher density values. On the contrary, the appellant deliberately decided not to provide neither in the patent, nor at a later stage with full knowledge of the objection of lack of sufficiency the DDI value for example 3 which has a value close to the upper limit of the range (0.9327 g/cm**(3)).

2.8 While the reasons provided in section 2.7 and subsections 2.7.1-2.7.12 above justify separately the presence of serious doubts that the copolymer of product claim 1 is sufficiently disclosed, the situation is exacerbated by the fact that conditions (c) and (e) related to DRI and condition (d) on DDI must be simultaneously fulfilled.

2.9 In the absence of indication of suitable common general knowledge which would allow the skilled person to fill the gap between the teaching of the patent and in suit and that which would be needed to prepare copolymers of ethylene and alpha-olefin over the whole scope for which protection is sought, the skilled person is left for a large part of those copolymers in the need to develop such missing methodology or to find out by trial and error which copolymers from the innumerable copolymers corresponding to the broad structural teaching of the patent in suit meet the parametric requirements set out in product claim 1. This amount in both situations to an undue burden for the skilled person.

2.10 As to the appellant's argument that it was up to the respondents to show that the preparation of the copolymers in accordance with product claim 1 amounted to an undue burden for the skilled person, the Board observes that each of the parties to the proceedings carries the burden of proof for the facts it alleges (Case Law, supra, III.G.5.1 and III.G.5.2). Who bears the burden of proof may be determined by the legal cases which the respective parties are trying to make. Whether it is discharged or not is assessed by the Board based on all the relevant evidence put before them, including the teaching or lack of teaching in the patent in suit in relation to the choice of suitable components and conditions necessary to obtain a copolymer meeting the parametric requirements of product claim 1. In the present case the existence of an undue burden results from the almost infinite number of copolymers that fall under the structural definition given in product claim 1, the serious doubts resulting from the analysis of the evidence available and the above established absence of a teaching in the patent in suit as to how select in an appropriate and straightforward manner the process conditions and components of the copolymers so as to meet the unusual parametric requirement of product claim 1. As a consequence, the onus of proof to demonstrate that the preparation of the copolymer over the whole scope for which protection is sought does not necessitate an undue amount of work for the skilled person is shifted to the patent proprietor (here appellant).

2.11 Accordingly, the subject-matter of product claim 1 lacks sufficiency of disclosure and the ground of opposition under Article 100(b) EPC prejudices the maintenance of the patent in the form of the main and first auxiliary requests in both forms.

3. Process claim

3.1 Claim 1 of the second auxiliary request filed with the statement of grounds of appeal concerns a process for the preparation of a copolymer of ethylene and an alpha-olefin, said copolymer being defined by the same set of parametric requirements (a) to (e) defining the copolymer of product claim 1 . The process of claim 1 of the second auxiliary request is further defined in that it comprises "polymerizing ethylene and an alpha-olefin in the presence of a metallocene catalyst system comprising a monocyclopentadienyl metallocene complex, said process being performed in the slurry phase in a multistage polymerisation process". The appellant did not provide a separate argumentation for claim 1 of the second auxiliary request and the features relating to the use of the metallocene catalyst system and process conditions during polymerization were not argued to change their position with regard to sufficiency of disclosure. Also, the Board does not find in the patent in suit any indication that the definition of the metallocene catalyst system as a catalyst comprising a monocyclopentadienyl metallocene complex and the fact that the process is performed in the slurry phase in a multistage polymerisation process would result in copolymers of ethylene and alpha-olefin fulfilling the set of parametric requirements (a) to (e) or would exclude that part of the claimed subject matter for which there is no sufficient guidance in that patent in suit.

3.2 Since the parametric requirements defining the ethylene alpha-olefin copolymer are identical in product claim 1 and in claim 1 of the second auxiliary request, the Board arrives at the same conclusion of lack of sufficiency of disclosure for claim 1 of the second auxiliary request for the same reasons as discussed for product claim 1 in point 2 above.

4. As all requests on file do not meet the requirement of sufficiency of disclosure, the appeal is to be dismissed and there is no need to decide on any other issue.