T2943/18

20.05.2022


The appeal by the patent proprietor lies against the decision of the opposition division revoking European patent No. 2 686 382.


Claim 1 of the main request reads as follows:
"1. Propylene random copolymer composition comprising
(A) 60-85wt% of a copolymer of propylene and from 0.1 to 2wt% of units derived from ethylene; and
(B) 15-40wt% of a copolymer of propylene and from 7 to 17wt% of units derived from ethylene,
said composition having a total ethylene content of from 3 to 4.5wt%, a melt flow rate value according to ISO 1133 (230°C, 2.16 kg) of from 10 to 120 g/10 min, and having a crystallisation temperature (Tc), as measured by Differential Scanning Calorimetry (DSC) with a cooling rate of 10°C/min, of above 123°C."

The opposition division held that the subject-matter of claim 1 thereof was not inventive.
Inventive step:

D3 is taken as the closest prior art.  The subject-matter of claim 1 only differs from the composition prepared in example 1 of D3 in that it should have a crystallisation temperature Tc as defined in claim 1 of above 123°C.

The propylene copolymers prepared in example 1 of D3 and in examples 1 to 6 of the patent in suit differ in significant features, so a fair comparison between the compositions being claimed and the one according to example 1 of D3 can not be provided.

The technical problem effectively solved over example 1 of D3 resides in the provision of a propylene random copolymer composition suitable for moulded articles having improved rigidity and processability in terms of reduced cycle time in injection moulding while maintaining good clarity.

It is derivable from D17 that it is known in the art that the processability in terms of reduced cycle time in injection moulding of a composition such as the one according to example 1 of D3 may be increased by the use of a nucleating agent, which is further accompanied by an improvement in terms of rigidity and optical properties and an increase in terms of crystallisation temperature. Further considering that D3 already teaches the optional (and even preferred) use of nucleating agents, adding a nucleating agent to increase processability/reduce cycle time in injection moulding and increase rigidity would be obvious.

However, should a nucleating agent be added to the composition of example 1 of D3, it still remains to be assessed whether or not in doing so, one would effectively arrive at the subject-matter of claim 1, in particular at a composition having a Tc above 123°C as defined therein.

In that regard, in view of the evidence on file and in particular in the absence of any indication of the crystallisation temperature of the composition of example 1 of D3, both nucleated and not nucleated, it cannot be concluded that this would obviously be the case. The Board is further of the opinion that in opposition the burden of proof in that respect primarily lies on the opponent, here the respondent. However, it was not shown that nucleated propylene copolymers prepared in a similar manner to the ones of example 1 of D3 may have a Tc above 123°C.

Under these circumstances, it cannot be agreed with the opposition division's finding that the sole addition of a nucleating agent in the composition prepared in example 1 of D3 mandatorily leads to a composition having a Tc of above 123°C as defined in claim 1.

In view of the above and in the absence of any data regarding the crystallisation temperature of a composition according to example 1 of D3 which further comprises a nucleating agent, the respondent argued that, in order to improve the rigidity of the composition of the closest prior art, the skilled person would further contemplate preparing said composition using a Ziegler-Natta catalyst instead of a metallocene catalyst as used in D3. In doing so, the Tc of the composition would mandatorily increase and be above 123°C, as required by claim 1.

In that respect, it is well known in the present technical field that metallocene and Ziegler-Natta catalysts constitute two different families of catalysts which generally lead to fundamentally different properties of the polymers prepared therewith. Therefore, it appears highly questionable that it may be held obvious to modify example 1 of D3 by changing the catalyst specifically disclosed therein.

The respondent's argument that the skilled person would contemplate changing the catalyst used in D3 and prepare the composition of example 1 of D3 using a Ziegler-Natta catalyst instead of a metallocene catalysts as taught in D3 while at the same time adding a nucleating agent, is based on hindsight.

For these reasons, the distinguishing feature identified above is not obvious in view of the teaching of the prior art documents cited. Therefore, the respondent's objection concerning lack of inventive step of the the subject-matter of claim 1 starting from D3 as the closest prior art document is rejected.

The case is remitted to the department of first instance with the order to maintain the patent in amended form on the basis of the claims of the main request filed with the statement of grounds of appeal, after any necessary consequential amendment of the description.

 


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