T 2425/19 15-09-2023

Reasons for the Decision

Main request (claims as granted)

1. Sufficiency of disclosure

1.1 According to the established jurisprudence of the Boards of Appeal, a European patent complies with the requirements of sufficiency of disclosure, if a skilled person, on the basis of the information provided in the patent specification and, if necessary, using common general knowledge, is able to carry out the invention as claimed in its whole extent without undue burden, i.e. with reasonable effort. This means in the present case that the skilled person must be able to prepare multimodal polyethylene compositions having a melt flow rate at a load of 21.6 kg (MFR21) of equal to or less than 7.0 g/10 min, determined according to ISO 1133 at a temperature of 190°C and a load of 21.6 kg and comprising a base resin that comprises a low molecular weight ethylene homo- or copolymer fraction (A) and a high molecular weight ethylene homo-or copolymer fraction (B), wherein fraction (A) has a lower average molecular weight as fraction (B), the base resin having to fulfil the following set of conditions:

(a) a weight average molecular weight (Mw) of from 190,000 g/mol to 300,000 g/mol, determined by GPC according to ISO 16014-4:2003 and ASTM D 6474-99,

(b) a complex viscosity at 0.05 rad/s (eta**(*)0.05 rad/s) of 75 to 500 kPa.s and

(c) a shear thinning index, being the ratio of the complex viscosities at a shear stress 2.7 kPa and at a shear stress of 210 kPa, (SHI2.7/210) of 10 to 60, eta**(*)0.05 rad/s and SHI2.7/210 being determined by dynamic shear measurements according to ISO 6721-1 and ISO 6721-10.

1.2 The opponents maintained their objection of lack of sufficient disclosure against claims 1 and 12 as granted in the appeal proceedings. In particular, it was argued that the skilled person, contrary to the findings of the impugned decision, did not find sufficient guidance as to the preparation of multimodal polyethylene compositions fulfilling the conditions set out for the base resin in granted claim 1.

1.3 The arguments of the patent proprietor were that the patent in suit provided guidance for the process, conditions and starting materials in the description and contained an example showing how a composition according to granted claim 1 was obtained. On that basis, it was argued, the skilled person could perform the invention as set out in granted claim 1.

1.4 The question that the Board has to address is therefore whether the patent in suit contains sufficient guidance as to the preparation of the multimodal polyethylene compositions meeting the combination of parameters defined in granted claim 1 throughout the whole area claimed, taking into account the information given in the patent in suit, using common general knowledge and routine experimentation.

1.5 The patent in suit contains a general definition of the multimodal polyethylene compositions corresponding to the definition of granted claim 1 (paragraph 13) followed by a section addressing the base resin which forms part of the compositions (paragraphs 18-49). That section discloses the two fractions (A) and (B) of the base resin and contains passages discussing individual features of the base resin. In these passages, the description discloses the comonomer content (paragraph 33), complex viscosity (paragraph 35), weight average molecular weight (paragraph 36), shear thinning index SHI(2.7/210) (paragraph 42), density (paragraph 43), melt flow rates and flow rate ratio (paragraphs 44-46) and melting and crystallization temperatures (paragraphs 48 and 49) of the base resin only in terms of preferred ranges. There is in the part dedicated to the definition of the base resin in the description no teaching as to how a base resin having simultaneously a weight average molecular weight (Mw) of from 190,000 g/mol to 300,000 g/mol, a complex viscosity at 0.05 rad/s (eta**(*)0.05 rad/s) of 75 to 500 kPa.s and a shear thinning index (SHI2.7/210) of 10 to 60 (conditions (a) to (c) as defined above) can be obtained.

1.6 A process for the production of the multimodal polyethylene compositions is also disclosed in the patent in suit (paragraph 70). From that passage the skilled reader learns that the base resin is produced in a multi-stage process and that after polymerization the base resin is separated in at least two fractions with a different particle size in a sieving step.

1.6.1 The multi-stage process is further disclosed in the description in paragraphs 75-114 but only in very general terms and by way of optional and preferred features or ranges (slurry or gas phase polymerization, reactor, monomer concentration, polymerization temperature and residence time). There is no teaching as to how a skilled person could specifically implement that process to obtain a base resin fulfilling the conditions (a) to (c) of granted claim 1.

1.6.2 The sieving step applied to the base resin after the multi-stage polymerization is disclosed in paragraphs 70 and 132 of the description. It is said to lead to the separation of the polyethylene resin in at least two fractions of different particle size (preferred ranges are given in paragraph 135) but there is no further teaching as to how the sieving step, if need be in conjunction with the parameters of the multi-stage process, could lead to a base resin fulfilling the conditions (a) to (c) of granted claim 1.

1.6.3 While from that general teaching the skilled person can derive the information that a multi-stage polymerisation followed by a sieving step is necessary, no guidance is available as to how the operating conditions of the former and of the latter should be selected in order to obtain a base resin fulfilling the conditions (a) to (c) and in particular as to how these operating conditions should be modified in order to change a failure into success when the desired result is not obtained.

1.6.4 At the oral proceedings before the Board the patent proprietor considered that the definition of the catalyst in the patent in suit was relevant to the sufficiency of disclosure of granted claim 1. The disclosure of the catalyst in the description (paragraphs 115 to 124) is, however, completely unspecific and starts by stating: "As catalyst system any system of catalyst and optionally cocatalyst can be used suitable for polymerising polyethylene resins". The catalyst in the patent in suit is in particular not linked to any teaching relating to the preparation of a base resin fulfilling the conditions (a) to (c) of granted claim 1. The Board therefore does not find that the catalyst is in itself relevant to the question of sufficiency of disclosure of granted claim 1.

1.7 The patent proprietor also relied on the single example of the patent in suit in order to show how a multimodal polyethylene composition and a base resin according to granted claim 1 could be obtained. The example of the patent in suit, also by reference to the example of document D1 (preparation of inventive material A) indeed shows the disclosure of one specific multi-stage polymerization process followed by a sieving step resulting in a base resin (fraction 3) according to granted claim 1. The question to be answered, however, is whether a single example gives sufficient guidance to the skilled person as to how to obtain the base resin of the multimodal polyethylene compositions over the whole scope of granted claim 1.

1.8 Fraction 3 of the example of the patent in suit, which corresponds to polyethylene particles of a size of 250 to less than 400 mym, happens to fulfil conditions (a) to (c) (Mw of 265 000 g/mol, eta**(*)0.05 rad/s of 301.3 kPa.s and SHI2.7/210 of 29) but it is apparent that neither the multi-stage polymerization process of the example of D1, nor the sieving step disclosed in the example of the patent in suit contain a direct teaching of how the process features and the sieving step should be chosen in order to prepare a base resin meeting the conditions (a) to (c) over the whole breadth of claim 1.

1.9 Table 1 in the patent in suit shows marked trends in the variation of the weight average molecular weight, complex viscosity and shear thinning index across the fractions of different particle sizes. The skilled reader further derives from Table 1 that with increasing particle size ranges of the polyethylene fractions (less than 125 mym in fraction 1, between 125 and less than 250 mym in fraction 2, between 250 and less than 400 mym in fraction 3 and 400 mym or more in fraction 4) the weight average molecular weight and the complex viscosity increase steeply (131 0000 g/mol and 24.6 kPa.s for fraction 1, 159 0000 g/mol and 71.2 kPa.s for fraction 2, 265 0000 g/mol and 301.3 kPa.s for fraction 3 and 273 0000 g/mol and 513.8 kPa.s for fraction 4) whereas the shear thinning index sharply decreases (181 for fraction 1, 130 for fraction 2, 29 for fraction 3 and 18 for fraction 4).

1.10 In order to obtain a base resin having a complex viscosity eta**(*)0.05 rad/s over the whole range of 75 to 500 kPa.s according to claim 1, for instance close to the minimum value of 75 kPa.s, the skilled reader would have derived from Table 1 that fractions of lower particle sizes should be considered, close to the particle size of fraction 2. Table 1 however suggests that for low values of the complex viscosity the weight average molecular weight and the shear thinning index of the fractions will be largely outside the ranges defined in granted claim 1. There is in the patent in suit no further guidance as to how the sieving step should be adapted so as to obtain base resins over the whole scope of granted claim 1 and there is also no guidance as to whether the parameters of the multi-stage process should be modified and if so, how they should be modified so that such base resins could be obtained.

1.11 The Board therefore concludes that the patent in suit does not provide the necessary guidance for the preparation of the multimodal polyethylene compositions defined in granted claim 1 over its whole scope and with a reasonable effort. The same conclusion is valid for the process claim 12 as granted which refers to the compositions of granted claim 1 and does not provide any process limitation in addition to the ones discussed above. Granted claims 1 and 12 therefore lack sufficiency of disclosure.

Auxiliary requests 1 to 5

2. Sufficiency of disclosure

2.1 Sufficiency of disclosure of auxiliary requests 1 to 5 was in dispute between the parties which relied on their arguments provided for the main request and did not provide specific arguments for these auxiliary requests.

2.2 Claim 1 of auxiliary request 1 differed from granted claim 1 in that the multimodal polyethylene composition was further limited in that it has at least one of the following properties: a Charpy notched impact strength at 0°C of at least 30 kJ/m², a Charpy notched impact strength at -30°C of at least 15 kJ/m², and/or a Charpy notched impact strength at -40°C of at least 13 kJ/m², determined according to ISO 179/1eA:2000 on compression moulded specimens prepared according to ISO 293:2004. Claim 1 of auxiliary request 1 therefore differed from granted claim 1 in that a further condition had to be fulfilled by the multimodal polyethylene composition in addition to those set out in granted claim 1.

2.3 The Charpy notched impact strength of the polyethylene composition at 0°C, -30°C and -40°C is disclosed in paragraphs 62-64 of the patent in suit only by way of preferred ranges. As for the other features of claim 1, there is no teaching in the patent in suit as to how the ranges of Charpy notched impact strength of the polyethylene composition at 0°C, -30°C and -40°C could be obtained by adjusting any of the features of claim 1 or any step of the multi-stage polymerization process or the sieving step. It has also not been shown that the limitation of the Charpy notched impact strength of the polyethylene composition was in any way relevant to the definition of the base resin by way of the conditions (a) to (c). It follows that the reasoning and conclusion of lack of sufficiency reached for granted claim 1 equally apply to claim 1 of auxiliary request 1. Since claims 1 of auxiliary requests 2 and 3 were identical to claim 1 of auxiliary request 1, the conclusion of lack of sufficiency also applies to auxiliary requests 2 and 3.

2.4 Claim 1 of auxiliary requests 4 and 5 corresponded to claim 1 of auxiliary request 1 in which two of the three additional limitations applying to the Charpy notched impact strength of the polyethylene composition (Charpy notched impact strength at -30°C and -40°C) were deleted. The limitation regarding the Charpy notched impact strength of the polyethylene composition at 0°C remains in claim 1 of auxiliary requests 4 and 5. The reasoning and conclusion of lack of sufficient disclosure applying to claim 1 of auxiliary request 1 therefore equally applies to claim 1 of auxiliary requests 4 and 5.

Auxiliary requests 6 and 7

3. Sufficiency of disclosure

3.1 Claim 1 of auxiliary requests 6 corresponded to claim 1 of auxiliary request 4 further limited in that the base resin had a density of 935 to 945 kg/m**(3) and the range of melt flow rate at a load of 21.6 kg (MFR21) was limited to "equal to or less than 5.0 g/10 min". By comparison with granted claim 1, the multimodal polyethylene compositions must fulfill an additional condition relating to their Charpy notched impact strength at 0°C (at least 30 kJ/m**(2)) at a more limited range of melt flow rate (MFR21) (from at equal to or less than 5.0 g/10 min) and the base resin must also fulfill an additional condition relating to its density (935 to 945 kg/m**(3)).

3.2 The density of the base resin is addressed in paragraph 43 of the patent in suit and is defined by way of preferred ranges. The density of a base resin is a parameter that is in itself known in the field but its addition in claim 1, in combination with the other conditions (a)-(c) set out for the base resin, renders its preparation even more complex than it was in the case of granted claim 1. There is also no teaching in the patent in suit the skilled person could rely upon in order to prepare base resins according to claim 1 of auxiliary request 6.

3.3 The example of the patent in suit would not provide the skilled person with additional guidance either. Table 1 shows that the density of the base resin varies with the particle size's fraction and only fraction 3 (941 kg/m**(3)) has a density within the the range of operative claim 1. A variation of the range of particle sizes of the fractions separated by sieving after the multi-stage process therefore leads to opposite variations of the four conditions the base resin has to fulfill, and the patent proprietor did not show how these variations could be adjusted in order to arrive at a composition according to claim 1 of auxiliary request 6 over the whole scope of the claim. The Board therefore concludes that claim 1 of auxiliary request 6 lacks sufficiency of disclosure. The same conclusion applies to claim 1 of auxiliary request 7 which is identical to claim 1 of auxiliary request 6.

Auxiliary requests 8 and 9

4. Sufficiency of disclosure

4.1 Claim 1 of auxiliary request 8 corresponded to claim 1 of auxiliary request 4 further modified in that the multimodal composition has "pressure resistance determined at 5.6 MPa and a temperature of 80°C of at least 1000 h, and/or a pressure resistance determined at 5.7 MPa and a temperature of 80°C of at least 1000 h, determined according to ISO 1167-1:2006 on 32 mm SDR 11 pipes".

4.2 All parties relied on their arguments provided for the main request for the objection of lack of sufficiency of disclosure of auxiliary requests 8 and 9.

4.3 The pressure resistance of the multimodal polyethylene composition is disclosed in paragraphs 67 and 68 of the patent in suit. It is again disclosed by way of preferred ranges for which there is no teaching in the patent in suit as to how these ranges could be met alone or in combination with the other requirements set out in claim 1 of auxiliary request 8. The reasoning and conclusion concerning the lack of sufficiency of claim 1 of the auxiliary request 4 upon which claim 1 of auxiliary request 8 is based, also apply. The same conclusion also applies to claim 1 of auxiliary request 9 which is identical to claim 1 of auxiliary request 8.

4.4 Claim 1 according to auxiliary requests 8 and 9 therefore lacks sufficiency of disclosure.

Auxiliary requests 10 and 11

5. Sufficiency of disclosure

5.1 Claim 1 of auxiliary request 10 corresponds to claim 1 of auxiliary request 8 with a further limitation of the ranges of weight average molecular weight (Mw) to 220,000 g/mol to 280,000 g/mol, of complex viscosity to 175 to 400 kPa·s, of shear thinning index to 17 to 45 and of density to 935 to 947 kg/m³.

5.2 In addition to the requirements set out in granted claim 1, claim 1 of auxiliary request 10 requires the multimodal polyethylene composition to fulfill a set of additional conditions pertaining to its Charpy notched impact strength at 0°C and its pressure resistance, and the base resin to additionally have a density in a defined range as well as fulfilling more restricted ranges of weight average molecular weight, complex viscosity and shear thinning index.

5.3 The patent proprietor argued that the limitations performed in claim 1 of auxiliary request 10 brought the scope of claim 1 closer to the example for which a preparation was disclosed in the patent in suit. There is, however, no teaching in the patent in suit on how a base resin can be obtained that fulfils a set of four conditions (density, weight average molecular weight, complex viscosity and shear thinning index) as part of a composition that must simultaneously fulfill three additional conditions (melt flow rate (MFR21), Charpy notched impact strength at 0°C and pressure resistance). The number of conditions present in claim 1 of auxiliary request 10 in fact aggravates the lack of guidance as to the preparation of the composition as it adds further parameters to the claim for which there is no specific teaching in the patent in suit. The conclusion of the Board is that claim 1 of auxiliary request 10 also lacks sufficiency of disclosure.

5.4 Claim 1 of auxiliary request 11 is identical to claim 1 of auxiliary request 10. The conclusion of on the lack of sufficient disclosure reached for auxiliary request 10 also applies to auxiliary request 11.

Auxiliary requests 12 and 13

6. Sufficiency of disclosure

6.1 Claim 1 of auxiliary request 12 corresponded to granted claim 1 with the further limitation that the particle size of the base resin to a range of "equal to or higher than 200 µm and less than 500 µm". Claim 1 of auxiliary request 13 is identical to claim 1 of auxiliary request 12.

6.2 The particle size of the resin obtained by the multi-stage polymerization process disclosed in the patent in suit is discussed in paragraph 135 in which the particle size is again defined in broad terms by way of preferred ranges. It can be understood from the passage in paragraphs 132 to 134 that the selection of any range of particle size can be achieved by sieving the resin. There is, however, nowhere in the description nor in the example of the patent in suit a teaching from which it could be derived that by sieving the resin so that only particles of a size of equal to or higher than 200 µm and less than 500 µm are retained, a resin also fulfilling the conditions relating to the weight average molecular weight, complex viscosity and shear thinning index defined in operative claim 1 would be obtained. On the contrary, the example shows that in order to obtain one or more of the conditions of the base resin over the whole scope of the claim, the specific particle size would not be suitable (see analysis of the example in points 1.7-1.10 above). The Board therefore concludes that claim 1 according to auxiliary requests 12 and 13 also lacks sufficiency of disclosure.

Auxiliary requests 14 to 16

7. Sufficiency of disclosure

7.1 Claim 1 of auxiliary request 14 pertains to a process for preparing a multimodal polyethylene composition. Its formulation corresponds to that of granted claim 12 in which the wording "polyethylene composition according to any of the preceding claims" was replaced by the wording pertaining to the multimodal polyethylene composition defined in granted claim 1. Claim 1 of auxiliary request 14 therefore corresponds to the scope of granted claim 12 when dependant on granted claim 1.

7.2 The Board already came to the conclusion that both granted claims 1 and 12 lacked sufficiency of disclosure. The same reasoning and conclusion of lack of sufficiency of disclosure apply therefore to claim 1 of auxiliary request 14.

7.3 Claim 1 of auxiliary request 15 is identical to claim 1 of auxiliary request 14. The conclusion of lack of sufficiency of disclosure reached for claim 1 of auxiliary request 14 therefore also applies to claim 1 of auxiliary request 15.

7.4 Claim 1 of auxiliary request 16 corresponds to claim 1 of auxiliary request 14 further limited in that "after the sieving step a fraction having a particle size of 200 µm to less than 500 µm is selected and preferably is compounded to form the polyethylene composition".

7.5 All parties relied for claim 1 of auxiliary request 16 on their arguments of sufficiency of disclosure provided for claim 1 of auxiliary request 14. No further arguments specific to auxiliary request 16 were provided.

7.6 The separation of the base resin obtained by the multi-stage polymerization process in a fraction of particle size of from 200 mym to less than 500 mym is discussed in paragraph 135 of the patent in suit. It has already been established above (section 6.3 of the present decision) that there was nowhere in the description, nor in the example of the patent in suit a teaching from which it could be derived that by sieving the resin so as to obtain particles of a size of from 200 µm to less than 500 µm a resin fulfilling the conditions relating to the weight average molecular weight, complex viscosity and shear thinning index defined in operative claim 1 would be obtained. The Board therefore also concludes that claim 1 of auxiliary request 16 lacks sufficiency of disclosure.

Auxiliary requests 17

8. Sufficiency of disclosure

8.1 Claim 1 of auxiliary request 17 corresponded to granted claim 1 with the addition of the density feature of claim 1 of auxiliary request 6 and the further limitation of the ranges of weight average molecular weight (Mw) to 250,000 g/mol to 270,000 g/mol, of complex viscosity to 250 to 350 kPa·s, of shear thinning index to 22 to 35, and of melt flow rate (MFR21) to equal to or less than 5.0 g/10 min.

8.2 In order to prepare a multimodal polyethylene composition according to claim 1 of auxiliary request 17 the skilled person must therefore provide a base resin having to fulfill a set of conditions relating to its density, weight average molecular weight, complex viscosity and shear thinning index within even more limited ranges. The patent in suit, however, discloses these features and ranges independently from one another and does not provide a teaching showing how these ranges could be achieved in combination as required in operative claim 1, and there is no indication in the patent in suit that the recovery of a base resin having a specific range of particle sizes after sieving would ultimately lead to a composition fulfilling the set of conditions defined in claim 1.

8.3 Table 1 of the patent in suit shows the preparation of a base resin among which only that of fraction 3 is according to the definition of operative claim 1. The table also shows that the parameters of the base resin underlie opposite variations with increasing particle sizes (the density and the shear thinning index decreases while the weight average molecular weight and the complex viscosity increases). In how far the skilled person could have adjusted the parameters of the preparation process in order to be able to obtain a base resin and a multimodal polyethylene composition over the whole scope of claim 1 of auxiliary request 17 is not disclosed in the patent in suit nor was shown to be part of the common general knowledge of the skilled person. The Board therefore concludes that claim 1 of auxiliary request 17 lacks sufficiency of disclosure.