T 2210/19 13-01-2021

Reasons for the Decision

Main request

1. Inventive step

1.1 Claim 1 of the main request generally pertains to a process for producing a chromium catalysed ethylene copolymer powder by polymerising the corresponding monomers in the presence of an activated supported chromium oxide based catalyst, the process comprising the step of activation of the catalyst. Claim 1 of the main request corresponds to claim 1 of the 3**(rd) auxiliary request found to be inventive over D3 in the contested decision. D3 and in particular its example 20 was chosen as the closest prior art with respect to operative claim 1 in the contested decision. That choice was not disputed in appeal. D3, as the patent in suit, concerns olefin polymerization catalysts and more specifically chromium based catalysts and methods of use of chromium based catalysts for the production of polyolefins (D3, paragraph 2; patent in suit, paragraph 1). The Board does not see a reason to deviate from D3 as the closest prior art.

1.2 Example 20 of D3 was seen as particularly relevant as starting point for the assessment of inventive step of operative claim 1. Example 20 of D3 discloses the use of a DEAlE-reduced chromium oxide based catalyst supported on 957HS silica (paragraphs 97, 105 and 111) to produce an ethylene/hexene copolymer (Table 2a on page 40). The catalyst is said to be prepared in accordance with Example 7 (Table 2a). The activation conditions of that catalyst are given in paragraph 97, in particular the catalyst was charged into a fluidised bed heating vessel, heated under dry nitrogen up to 325°C and held at that temperature for 2 hours after which the nitrogen stream was replaced by a stream of dry air and the catalyst heated slowly up to 600°C where it was activated for 6 hours. The activated catalyst was then cooled with dry air to about 300°C and further cooled to room temperature with dry nitrogen. It is apparent from that description that the silica supported DEAlE-reduced chromium oxide catalyst used in example 20 was activated in a fluidised bed activation reactor and that it was submitted to a temperature of above 500°C, as required by operative claim 1.

1.3 D3 does not disclose the particle fragmentation coefficient of the copolymer produced. However, it was not in dispute that the particle fragmentation coefficient, which is defined by a formula given in operative claim 1 and in paragraph 6 of the patent in suit, could be calculated from the information provided in the examples of D3. In this context the experimental report D6, and in particular its Table 3, shows that the fragmentation coefficient calculated for the copolymer produced from the process according to example 20 of D3 is 0.360, i.e. it is in the range defined in operative claim 1 (at least 0.29). Also that conclusion was not in dispute between the parties in appeal.

1.4 The fluidisation gas velocity profile is not given in D3 nor is derivable from the information contained in that document. The fluidisation gas velocity profile defined in operative claim 1 requires that the fluidisation velocity (Vf1) of the fluidisation gas is initially maintained below 6.5 cm/s, until the temperature inside the activation reactor reaches at least 200°C, and said fluidisation gas is then brought to a value (Vf2) which is at least l cm/s higher than Vf1. That fluidisation velocity profile constitutes therefore the distinguishing feature over the process of example 20 of D3.

1.5 The opposition division found in the contested decision that there was no evidence on file that the polymer powders obtained in the example of the patent in suit had improved properties, such as ESCR, creep, melt index and catalyst activity as compared to the closest prior art D3 and also with respect to the comparative examples of the patent in suit. The opposition division considered that due to the differences in the processes disclosed in the examples of the patent in suit and in example 20 of D3, it could not be concluded that the fluidisation gas velocity profile according to operative claim 1 resulted in any effect over the process of the closest prior art. The opposition division concluded therefrom that the problem over D3 was "to provide an alternative process of preparation of an ethylene copolymer with a high fragmentation coefficient with an activated chromium oxide catalyst" (section 3.2, last paragraph on page 12). By contrast, the respondent contended at the oral proceedings before the Board that the problem over D3 was the provision of a reliable and consistent method for the production of a chromium catalysed ethylene copolymer powder with a low fragmentation i.e. a high fragmentation coefficient. This, it was argued, would be achieved by the adoption of the claimed fluidisation gas velocity profile. The respondent based their formulation of the problem on the example and the two comparative examples of the patent in suit.

1.6 According to the case law of the boards of appeal, alleged advantages to which the patent proprietor merely refers, without offering sufficient evidence to support the comparison with the closest prior art, cannot be taken into consideration in determining the problem underlying the invention and therefore in assessing inventive step (Case Law of the Boards of Appeal, 9th Edition, July 2019, I.D.4.2).

1.7 The patent in suit contains a single example according to operative claim 1. In that example the polymer obtained from the polymerization process had a fragmentation coefficient of 0.315. It is however clear from the description of example 1 of the patent in suit in paragraph 53 that apart from being a silica supported chromium oxide catalyst, the catalyst used in that example differs in multiple instances from that used in example 20 of D3 such as in the type of silica support (957HS in D3, MS-3050 in example 1 of the patent in suit), different particle sizes (40 mym in paragraph 97 in D3, 90 mym in paragraph 54 in example 1 of the patent in suit) and surface areas (300 m**(2)/g in paragraph 97 in D3, 470 m**(2)/g in paragraph 54 in example 1 of the patent in suit). The appellant made plausible that these differences would have an impact on the process and on the polymer produced. In particular, since the particle size of the catalyst is involved in the formula defining the fragmentation coefficient of the polymer produced, it is immediately clear that the different particle sizes of the catalysts used in the example of the patent in suit and in example 20 of D3 will affect the fragmentation coefficient of the resulting polymer. In that regard, any effect resulting from the use of the catalyst disclosed in the example of the patent in suit on the fragmentation coefficient of the produced polymer cannot be attributed to the distinguishing feature of claim 1 of the main request over D3.

1.8 It can thus not be concluded from the example of the patent in suit that the process of claim 1 of the main request leads to olefin polymers with improved properties or to a particularly reliable and consistent method for the production of a chromium catalysed ethylene copolymer powder with a low fragmentation i.e. a high fragmentation coefficient. The comparative examples 1 and 2 of the patent in suit do not support a different conclusion either since the catalysts used in the examples of the patent in suit are different commercial products (PQC35105 in example 1; PQC24340 in comparative example 1; EP350X in comparative example 2) and have morphologies that differ from the catalyst according to example 1 and also involve different supports (aluminium modified vs. titanium modified supports) and different chromium loadings as apparent from paragraphs 60-68 of the patent in suit. Moreover, the conditions applied during the following olefin polymerisation were also different (polymerisation temperatures, partial pressures, proportions of hexene copolymer, bed levels, fluidisation velocities and production rates) as is apparent from the example of the patent in suit, paragraph 59 and comparative examples 1 and 2, paragraphs 66 and 73. The achievement of a given fragmentation coefficient cannot therefore be attributed to the use of a specific fluidisation profile.

1.9 The Board concludes therefrom that the data contained in the patent in suit do not support the formulation of problem as the provision of a reliable and consistent method for the production of a chromium catalysed ethylene copolymer powders with a low fragmentation i.e. a high fragmentation coefficient.

1.10 Since there are no data on file that can show that the fluidisation velocity profile according to claim 1 of the main request results in any improvement over the process disclosed in example 20 of D3, the problem can only be defined as the provision of a further process for producing a chromium catalysed ethylene copolymer powder, in accordance with the problem that was proposed in the preliminary opinion of the Board (section 10.10).

1.11 The skilled person, looking for a further process, would consider variations of the process already known from the closest prior art, taking into account the common general knowledge in the field and the knowledge made available in the prior art. That includes variations of any of the parameters of the process that can be expected to be suitable to carry out alternative processes without exercising any inventive activity. As the problem is simply the provision of a further process, no further motivation is needed by the skilled person to perform the modified process.

1.11.1 The formulation of the activation step a) in claim 1 of the main request is open ("comprising") and allows a change of the fluidisation gas from dry nitrogen to dry air, as done in D3. The question with respect to obviousness in the present case is whether, in the activation process of the silica supported chromium oxide catalyst used in example 20 of D3, the selection of a gas velocity of below 6.5 cm/s until the temperature inside the activation reactor reaches at least 200°C, followed by an increase of said fluidisation gas velocity at any point after that temperature was reached by at least l cm/s in order to merely provide a further process, could be seen as involving an inventive step.

1.11.2 The activation of chromium catalysts is discussed broadly in paragraphs 51-53 of D3, where it is taught that when a fluidized bed is used, the passage of a stream of dry air or oxygen through the supported chromium-based catalyst during the activation aids in the displacement of any water from the support and converts, at least partially, chromium species to Cr**(+6). There is however no mention of the gas velocity during activation in D3 and thus no teaching that the gas velocity would be limited in any way as long as it makes technical sense in the context of the activation.

1.11.3 D7, a textbook on catalysis containing a section on supported chromium catalysts used in ethylene polymerization processes (section 3, A Review of the Phillips Supported Chromium Catalyst and Its Commercial Use for Ethylene Polymerization, pages v and vi of the index), provides some insights as to which types of fluidisation gas velocities were known to be used in activation processes of supported chromium catalysts. In particular, section 20.4 of D7 relates to the mathematical modeling of an activation process and mentions an activation example in which the supported chromium catalyst was brought to a temperature of up to 800°C under an air flow having a velocity of 6.4 cm/s (page 573, second paragraph and Figure 252). The model shows that the use of a gas velocity close to the value defined in operative claim 1 (6.5 cm/s) at a temperature that is above 500°C was known in the art. Also, gas velocity values in the broader range of about 5-12.5 cm/s, but still encompassing the threshold of 6.5 cm/s defined in operative claim 1, are disclosed for other commercial teste activations on Figure 253 (middle part relating to air velocity) on page 574 of D7. Also, D8, which is an academic publication relating to the same type of supported chromium catalyst activation mentions fluidized bed gas velocities of 1.5 to 10 cm/s as typical for commercial activation processes (page 254, second column, second paragraph). D7 and D8 show therefore that fluidized bed gas velocities below and above the threshold of 6.5 cm/s set out in claim 1 of the main request were already common in the art for the same type of activations.

1.11.4 While the activations disclosed in section 20.4 of D7 and in the second column on page 254 and page 255 of D8 for which the fluidisation gas velocity are given were performed at high temperatures of up to 800°C and more, as underlined by the respondent, there is nothing in D7 and D8 that limits the fluidisation gas velocities used during activation to any range of temperatures. Indeed, D8 (Section 3.2 and Figure 3 on page 254) and D7 (Figure 9 page 147; last paragraph of page 364 and section 20.3) teach that temperatures of as low as 400°C could be successfully used during activation and that the moisture released during activation was not detrimental to the stability of chromium VI in the catalyst up to a temperature of about 600°C (first paragraph on page 573 of D7). That teaching is compatible with the closest prior art D3 in which an activation temperature of 600°C was used in the activation of the catalyst involved in example 20. Also, the range of temperatures that can be used in the activation according to D3 largely overlaps with the one known from D7 and D8 since any temperature from about 300°C up to the temperature at which substantial sintering of the support takes place can be used (paragraph 51 of D3), which in paragraph 52 of D3 may be up to about 900°C. There is no teaching in D3, D7 or D8 that would lead away from the broad range of gas velocities of 1.5-10 cm/s at any activation temperature chosen between 400°C and 800°C in the cited prior art.

1.11.5 The choice of a fluidisation gas velocity in the range of 1.5-10 cm/s at an activation temperature of 600°C, would therefore be in view of the teachings of D7 or D8, a common measure that a skilled person could take to merely provide a further activation process that ultimately would provide a further process for producing a chromium catalysed ethylene copolymer powder.

1.11.6 The additional increase in velocity by 1 cm/s after the temperature reaches 200°C as defined in operative claim 1 was also not shown to provide any effect so that an increase of the gas velocity is seen as an arbitrary measure that the skilled person could have selected as well. In that regard, the measure is also generally known in the context of the activation of the catalyst, as suggested by D7 (page 576, 3**(rd) paragraph) and D8 (page 258, column 1, 2**(nd) paragraph). Increasing the velocity at any point during activation, even by 1 cm/s, is thus not seen as an inventive measure. Claim 1 of operative claim 1 is thus found to lack an inventive step.

1.11.7 The fact that the catalyst in D3 is treated, after its activation and prior to its use in the polymerization of olefins, with a reducing agent in order to tailor its flow index response (paragraph 17; claim 1 of D3) does not change the conclusion reached by the Board on obviousness. The treatment of the supported chromium catalyst with a reducing agent such as diethylaluminum ethoxide (DEAlE) as it is disclosed in D3 and which is said to have an influence on the molecular weight of the polyolefin produced (paragraphs 26-28) has not been shown to have a negative impact on the fragmentation coefficient of that polymer. Examples 20, 21 and 24-28 according to D3 that are also reported in Table 3 of D6 in particular show that a supported chromium catalyst activated under a gas velocity profile (#2) according to claim 1 of the main request and treated with a reducing agent (Tables 2A and 2B of D3) all display a fragmentation coefficient above 0.29 as required in claim 1 of the main request. In that regard, the fact that examples 22 and 23 of D3 are not reported in D6 alongside the other examples of D3 (examples 20,21 and 24-28) is as such not relevant to the question of obviousness since the process according to example 20 of D3, which is the starting point for the assessment of inventive step already leads to a fragmentation coefficient of the produced polymer of 0.360, a value that is within the range of operative claim 1 (equal or superior to 0.29). Finally, the process of claim 1 of the main request, because of its open formulation ("comprising") does not exclude a further step after the activation step a) and the polymerization step b) in which the activated catalyst is treated with a reducing agent in the same manner as in D3.

1.12 It follows that starting from example 20 of D3 the selection, in the activation step of the supported chromium catalyst, of a fluidisation gas velocity of below 6.5 cm/sec until the temperature inside the activation reactor reaches at least 200°C, followed by an increase of said fluidisation gas velocity at any point after that temperature was reached by at least l cm/sec is an obvious measure when aiming at merely providing a further process for producing a chromium catalysed ethylene copolymer powder. Therefore the process of claim 1 of the main request does not involve an inventive step.

1**(st) auxiliary request

2. Inventive step

2.1 Example 20 of D3, which was accepted by the parties as the closest prior art for the main request, remains the most relevant starting point for the assessment of inventive step of claim 1 of the 1**(st) auxiliary request.

2.2 Claim 1 of the 1**(st) auxiliary request differs from claim 1 of the main request in that, in the activation step of the supported chromium oxide based catalyst, the fluidisation gas used during the consecutive stage of the activation process is an inert gas followed by an oxidising gas.

2.3 The respondent argued that there was no disclosure in the prior art of a process containing the three stages relating to the specific fluidisation velocity profile involving the increase of the gas velocity as defined in claim 1 of the main request and additionally using first an inert gas followed by oxidising gas after the temperature in the activation reactor reached at least 200°C. However, the activation of the supported chromium catalyst used in example 20 of D3 is disclosed in paragraph 97. According to that process, porous silica support containing 2.5 weight percent chromium acetate is charged to a fluidized bed heating vessel and heated slowly at a rate of about 50°C per hour under dry nitrogen up to 325°C and held at that temperature for about 2 hours, after which the nitrogen stream was replaced with a stream of dry air and the catalyst composition was heated slowly at a rate of about 50°C per hour to 600°C where it was activated for about 6 hours. It is apparent from that passage that the activation involved the use of an inert gas (dry nitrogen), followed by an oxidising gas (dry air) after the temperature in the activation reactor reached 325°C (therefore at least 200°C).

2.4 It follows that operative claim 1 differs from example 20 of D3 only in the fluidisation velocity profile that was already part of the definition of claim 1 of the main request.

2.5 The added feature in claim 1 of the 1**(st) auxiliary request was not shown to result in any further effect by comparison to the main request. The patent in suit and in particular paragraphs 17 and 20, which concern the fluidisation gas used in the activation process, do not disclose any effect associated with the use of an inert gas followed by an oxidising gas in the fluidisation velocity profile according to operative claim 1. In view of the absence of any effect resulting from the feature added in operative claim 1, the problem remains, as for the main request, the provision of a further process.

2.6 In that regard, since claim 1 of the main request was found to lack an inventive step in view of D3 in combination with D7, the same conclusion is also reached in case of claim 1 of the 1**(st) auxiliary request for the same reasons as for claim 1 of the main request. Claim 1 of the 1**(st) auxiliary request lacks therefore an inventive step.

2**(nd) and 3**(rd) auxiliary requests

3. Inventive step

3.1 Claim 1 according to the 2**(nd) and 3**(rd) auxiliary requests differs from claim 1 of the 1**(st) auxiliary request only in the use of additional language meant to clarify the order of stages relating to the different gas velocities in the activation step. In particular, the language used in claim 1 according to the 2**(nd) and 3**(rd) auxiliary requests underlines that the stage at which the fluidisation gas velocity is at the value Vf1 and the one with an increase in gas velocity to a value (Vf2) which is at least 1 cm/s higher than Vf1 are consecutive stages of the activation. That however was not in dispute between the parties at the oral proceedings before the Board. Also, it was already understood that the stages at which the velocities are defined as being Vf1 and Vf2 in claim 1 of the main request are consecutive stages of the activation process. In that regard, the reasoning of inventive step applying to claim 1 of the 1**(st) auxiliary request equally applies to claim 1 according to the 2**(nd) and 3**(rd) auxiliary requests. Indeed the parties did not provide any separate argument on inventive step for these requests.

3.2 It follows that claim 1 according to the 2**(nd) and 3**(rd) auxiliary requests lacks an inventive step over D3 as the closest prior art.In view of this the issue of admittance of the 2**(nd) auxiliary request into the proceedings becomes irrelevant, as acknowledged by the appellant.

3.3 As all the requests of the respondent do not meet the requirements of Article 56 EPC, the appeal is to be dismissed and there is no need for the Board to decide on any other issue.