T 0626/22 (CROSS-LINKED PRODUCT/MITSUI CHEMICALS) 01-03-2024

Reasons for the Decision

1. Admittance of document D10

1.1 The respondent requested that document D10 not be admitted into the appeal proceedings.

1.2 The appellant submitted document D10 after filing its statement of grounds of appeal. Consequently, the provisions of Article 13(1) RPBA apply.

1.3 Document D10 deals with the analysis of chain unsaturations in ethene/1-octene copolymers prepared at high temperature. The appellant argued that document D10 had been filed in response to the respondent's reply to the statement of grounds of appeal, referring to the influence of the unsaturated double bonds of the ethylene copolymers on moulding stability.

1.4 However, this issue had already been discussed in the opposition proceedings and addressed in the decision under appeal. The opposition division concluded that the burden of proof was on the opponent to show that the further differences (other than those related to melt flow properties) between Example 3 and Comparative Example 3 of the patent had a significant impact on the properties measured (see section 3.3.2 of that decision). Consequently, in wishing to challenge that conclusion, the appellant should have adduced pertinent evidence at the latest with its statement of grounds of appeal. Document D10 should thus have been filed earlier.

1.5 What is more, it is common ground between the parties that the amount of unsaturated bonds of the polyethylene polymer influences its crosslinking properties. In this context, the appellant mentioned that this statement by the respondent was also supported by D10.

Moreover, the mere fact that ethylene copolymers which fall within the scope of the claims as granted can also comprise terminal vinylene groups does not undermine the opposition division's assessment that the cause of the improved moulding stability effect is to be ascribed to the MFR10/MFR2.16 ratio stipulated in the granted claims (see for example the fourth paragraph on page 21 of the decision under appeal).

Therefore, D10 was not prima facie relevant to the decision to be taken.

1.6 Consequently, the board did not admit document D10 into the appeal proceedings (Article 13(1) RPBA).

2. Inventive step

2.1 The patent

The patent relates to a method for producing a crosslinked product, a crosslinked product, the use thereof, an ethylene copolymer, and an ethylene copolymer composition (see paragraph [0001] of the patent).

2.2 Closest prior art

2.2.1 In the decision under appeal, it was held that document D1, and in particular Example 1 thereof rather than Example 5 or Comparative Example 3, was the most promising starting point for the assessment of inventive step of the granted claims. The board sees no reason to deviate from this assessment, for the following reasons.

2.2.2 It is uncontested that document D1 is directed towards the same purpose as the patent or a similar one, namely to provide ethylene-alpha-olefin copolymers that can be crosslinked, crosslinkable compositions comprising them and foamed moulded products obtained therefrom (see paragraph [0015] of D1; paragraphs [0001] and [0006] to [0009] of the patent).

2.2.3 However, it is disputed whether Examples 5/10 or Comparative Examples 3/11 represent promising alternative starting points for the assessment of inventive step.

2.2.4 Examples 5/10 are a less promising starting point than Example 1, because the claimed subject-matter differs from Example 1 only by the MFR10/MFR2.16 ratio, whereas it is further distinguished from Examples 5/10 by the MFR2.16 value.

2.2.5 At the oral proceedings before the board, the discussion focused on whether Comparative Examples 3/11 could be considered a suitable starting point for the assessment of inventive step.

As regards Comparative Example 3, the board endorses the opposition division's assessment that an embodiment that requires improvement in the light of D1 alone, an example that is labelled as "comparative", would not normally represent a suitable springboard for arriving at the claimed subject-matter. This finding is in line with decision T 2114/16 (Reasons 5.3.4), for example, to which the respondent referred. In addition, Comparative Example 3 has an MFR10/MFR2.16 ratio which D1 clearly teaches away from (see paragraph [0046]).

Moreover, keeping the MFR10 value in Comparative Examples 3/11 constant and increasing the MFR2.16 value to a value of, for example, 2.0 g/10 min to arrive at the subject-matter of claims 1 and 9 of the patent, as proposed by the appellant at the oral proceedings, would mean approximately doubling MFR2.16 from 1.1 to 2.0 g/10 min. However, this would result in an MFR10/MFR2.16 ratio of about 5, falling outside claim 1 and claim 9. Such an increase would thus not have led to the subject-matter of claims 1 and 9 of the patent.

This shortcoming is not overcome by the fact that paragraphs [0100] to [0106] of D1 provide information on means for adjusting the long-chain branching content in the ethylene copolymers and thus the MFR10/MFR2.16 ratio. As argued by the respondent, the skilled person - having decided to raise the MFR2.16 value to values falling within claim 1 - would have to change the copolymer used in Comparative Example 11 and adjust (raise) the MFR10/MFR2.16 ratio to a value falling within claims 1 and 9 of the patent, which would be against the teaching of D1. Whether the MFRs "disappear" in the final, crosslinked material, as argued by the appellant, has no bearing on this conclusion.

It is for these reasons that Comparative Examples 3/11 of D1 do not represent a suitable and realistic starting point for the assessment of inventive step.

2.2.6 In line with the decision under appeal, Example 1 of D1 is considered to be the most promising starting point, for the following reasons.

Having established (i) that the entire document D1 is directed towards the same (or a similar) purpose/use as the patent and (ii) that none of the embodiments described in D1 addresses the aspect of the moulding stability/dimensional stability of foamed moulded products, the most promising starting point for the notional skilled person is established from the structural similarity between the claimed subject-matter and the specific embodiments of D1. Example 1 is such an embodiment of D1, since the claimed subject-matter differs from the patent only in the MFR10/MFR2.16 ratio. A starting point established in such a manner is realistic and would require a minimum of structural and functional modifications to arrive at the claimed invention (see Case Law of the Boards of Appeal, tenth edition, 2022, I.D.3.2, second paragraph; T 606/89, Reasons 2). This finding is also in line with decision T 870/96 (Reasons 4.1, also referring to T 66/97) cited by the appellant, in particular since the purpose/use addressed by Examples 1 and 5 of D1 is already similar, and the claimed subject-matter differs from Example 5 by an additional feature (see point 2.2.4 above).

In view of these considerations, Example 1 qualifies as the most promising starting point for the assessment of inventive step.

2.3 Distinguishing features

As correctly held in the decision under appeal (see page 14), the ratio of MFR10/MFR2.16 in independent claims 1 and 9 represents the only distinguishing feature over Example 1 of D1 (the copolymer of Example 1 is used in Example 7 to prepare a crosslinked foamed product).

2.4 Technical effect and objective technical problem

2.4.1 The appellant argued that no technical effect had been substantiated of which the cause could be ascribed to the distinguishing feature. Consequently, the objective technical problem underlying the granted claims was to provide alternative compositions suitable for foam applications.

2.4.2 The board does not agree. There is no information at hand to indicate that the results described in the patent, and in particular in Table 1, could not be generalised. In this context, the appellant failed to present convincing arguments why an indication in the claims of the total content of unsaturated bonds, vinylidene groups and/or terminal vinylene moieties would be required in order to render the distinguishing feature non-arbitrary. The indication in claims 1 and 9 of the concentration of vinyl groups per 1000 carbon atoms ensures good mechanical strength and homogeneous crosslinking of the resulting moulded article (see paragraphs [0025],[0163] and [0165] of the patent). In view of this, whether or not other unsaturated groups would also contribute to mechanical strength and homogeneous crosslinking (to some extent) does not seem relevant. Similarly, the board holds that in view of the explanations provided in paragraph [0163], to which the respondent referred in this context, it is also convincing that the distinguishing feature brings about improved mouldability, in respect of the dimensional stability of moulded articles. The experimental results described in Table 1 of the patent reflect and support these conclusions. The appellant, challenging the corresponding conclusions in the decision under appeal, has not adduced any evidence that would prove the contrary.

2.4.3 The mere possibility that a considerable amount of the olefinic double bonds present in the copolymers can be situated at the ends/terminal position of the ethylene copolymers cannot per se undermine a link between the effect (dimensional stability of moulded foamed articles) and the distinguishing feature. In the appellant's submission dated 18 January 2023, the graphical representation of a linear regression displayed in point 16 does not indicate any R value (correlation coefficient) or therefore its significance. It does not demonstrate the causal nature of the alleged correlation between (dimensional) moulding stability and total unsaturation either. In this context, the respondent convincingly argued that paragraphs [0083] and [0084] of the patent set out that increasing the polymerisation temperature led to an increased MFR10/MFR2.16 ratio and an increased vinyl group content. The connection between vinyl group content and the distinguishing feature thus seems to be the influence of temperature on long-chain branching (associated with said MFR ratio) and vinyl group content/formation of unsaturated bonds. Hence, the technical effect of which the cause is ascribable to the distinguishing feature is indeed an improved moulding/dimensional stability.

2.4.4 It is not apparent that this benefit would not be obtainable across the full scope of the granted claims.

In this context, the appellant has not argued credibly that varying, for example, the content of the additional polymer such as ethylene vinyl acetate copolymer, silicone rubber and/or crosslinking agents in foamable compositions could undo the observed effect, even though it could be expected that this effect would be achieved to a lesser extent in compositions comprising smaller amounts of the ethylene copolymers than the examples of the patent.

2.4.5 The objective technical problem underlying the subject-matter of claim 9 in view of Examples 1/7 of D1 (the polymer of Example 1 is used in Example 7 of D1) is thus to provide ethylene copolymers that give a (foamed) product having improved moulding stability (dimensional stability).

2.5 Obviousness

2.5.1 Confronted with this objective technical problem, the skilled person would not be in a position to arrive at the subject-matter of claim 9 in an obvious way. D1 does not contain any teaching as to the missing link. The appellant's allegations that the skilled person would have used a higher melt flow rate (MFR2.16), in an obvious way in view of the higher resin fluidity in moulding applications, and that the MFR10/MFR2.16 ratio did not constitute a hurdle to arriving at the claimed subject-matter have not been substantiated. They are also irrelevant, considering that obviousness is judged on the basis of the problem to be solved as set out above. Put differently, it is not apparent why the skilled person would have arrived at the claimed subject-matter when trying to solve the problem posed. Consequently, this line of argument does not convince the board.

2.5.2 The conclusions arrived at in respect of inventive step would not be different even if Examples 5/10 of D1 were taken as the starting point. The board agrees with the opposition division that a comparison between Example 1 and Comparative Example 4 of the patent is pertinent. This comparison supports the above conclusions regarding the presence of the aforementioned technical effect and the non-obviousness of the solution provided by the subject-matter of claim 9. Whilst the MFR10/MFR2.16 ratio, vinyl group content and density values differ slightly between the ethylene copolymers obtained in Example 5 of D1 and Comparative Example 4 of the patent, the results obtained make credible the assertion that the moulding stability of the foamed specimens is markedly improved when moulding crosslinkable compositions comprising polymers as claimed in claim 9. This can be inferred from the doubled standard deviation value for the size of the moulded articles reported for Comparative Example 4, as compared to Example 1 of the patent.

2.5.3 The subject-matter of independent claim 9 is thus not obvious to a skilled person and therefore meets the requirement of Article 56 EPC.

2.5.4 Independent claims 1, 5, 6 and 11 as granted involve the copolymers of independent claim 9 as a technical feature. They too meet the requirement of Article 56 EPC for the aforementioned reasons, applied mutatis mutandis.

Consequently, the main request meets the requirement of Article 56 EPC. The corresponding ground for opposition under Article 100(a) EPC, lack of inventive step, does not prejudice the maintenance of the patent.