Tuesday, 8 May 2012

T 303/09 – Looking For Problems

The opponent appealed against the rejection of the opposition by the Opposition Division.

Claim 1 of the patent as granted read :
A papermaking belt comprising a reinforcing substrate embedded in a thermosetting polyurethane layer and having an outer peripheral surface and an inner peripheral surface formed by said thermosetting polyurethane layer, wherein a polyurethane layer forming said outer peripheral surface is made of a composition containing an urethane prepolymer having isocyanate groups on ends and a hardener containing dimethylthiotoluenediamine.
The Board found this claim to be distinguished from the closest prior art D1 by the nature of the hardener used. It then went on to examine the objective technical problem :

[3] According to D1, column 2, line 13ff, the problems of avoiding development of cracks and improving the abrasion resistance of the belts have been contradictory. It was an object of the invention of D1 to provide a belt capable of satisfying both these requirements. This problem is solved according to D1 by a structure whereby on one surface the hardness decreases laterally outwards from the middle portion to the side portion.

D1 contains two examples. The first demonstrates a belt wherein one surface has regions of differentiating hardness, the comparative example employs a belt where both surfaces have a uniform hardness across the width thereof. These examples show that the belt of the example according to the claims of D1 did not develop cracks after 600 hours on a “testing machine”, whereas the belt of the comparative example developed cracks after 250 hours. D1 contains no discussion of the considerations leading to the selection of the hardener or any consideration of possible alternatives.

[3.1] According to paragraph [0005] the object of the patent in suit is to provide a papermaking belt, formed by integrating a reinforcing substrate and a thermosetting polyurethane layer with each other, capable of preventing cracking. A further aim is to provide a belt as above, capable of suppressing growth of a crack even if one forms. A still further aim is to provide a belt resistant to delamination.

[3.2] Table 1 of the patent in suit compares belts having differing compositions of polyurethane forming the outer surface whereby the constitution of the prepolymer varies. Further two sets of belts are provided, one employing the hardener required by the claims, i.e. DMTDA, the other set employing MOCA, i.e. the hardener employed in D1. In the cases of both hardeners the same equivalent ratio of hardener hydrogen to isocyanate (H/NCO) of 1.04 is employed. Table 1 shows that for a given polyurethane prepolymer composition the belt prepared using DMTDA as hardener exhibits greater endurance. Thus the compositions according to the claims have endurance limits of between 250 and 2250 x 10**(4) reciprocations whereas the respective compositions employing MOCA achieve levels of only 10 to 90 x 10**(4).

[3.3] Table 2 reports examples based on the same three polyurethane compositions as in Table 1 but in which only DMTDA curative is employed. In the examples of Table 2 the equivalent ratio of hardener, expressed as H/NCO, is varied over the range 0.92-1.15. The results show that over the majority of this range, i.e. 0.92-1.14 no cracking is observed after 10**(6) reciprocations, which is superior to the best result obtained with the MOCA cured compositions reported in Table 1. Therefore, the examples of the patent in suit show that the distinguishing feature compared to D1, i.e. the use of DMTDA instead of MOCA, makes it possible to obtain a belt that is resistant to cracking even without a differentiated hardness profile across the width (i.e. the “comparative” belt structure of D1) and that this effect is, contrary to submissions of the [opponent] obtained over a broad range of hardener equivalent ratios.

[3.4] In the light of this evidence the technical problem to be solved with respect to D1 can be formulated as being to provide a further papermaking belt which is resistant to cracking and which does not require the differentiated hardness structure of D1, which problem has been effectively solved by using DTMDA instead of MOCA.

[4] The [opponent] argued that that the problem as set out in the patent in suit was not in fact the correct one and that a different problem should be adopted, namely that of avoiding the use of MOCA hardener or to provide a papermaking belt employing less toxic materials.

[4.1] According to the problem solution approach, the problem as set out in the patent in suit is normally taken as the starting point for the analysis of inventive step. Under certain circumstances it is permissible – or even necessary – to modify this and adopt a different problem. For example, if it had been shown that the problem as set out in the patent had not been solved, or if inappropriate prior art had been employed to define the problem (see summary of the appropriate case law presented in “Case Law”, infra section I.D.4.3.2). In view of the analysis set out in sections 2 and 3 above, it is apparent that such circumstances do not exist in the present case since both D1 and the patent in suit address the same problem, namely cracking of the paper-making belt, and the evidence of the patent in suit shows that this problem has been solved by the distinguishing feature with respect to closest prior art D1.

[4.2] The [opponent] invoked two decisions to support its position that in the present case it was appropriate to depart from the problem as set out in the patent in suit. According to T 910/90, when assessing the objective technical problem, it was not important whether the problem had already been mentioned in the closest prior art, but what mattered was what the skilled person objectively recognised as the problem when comparing the closest prior art with the invention (T 910/90, [final passage on page 9 thereof]). In the present case, one aspect of the technical problem mentioned in the prior art is the same as in the patent, namely prevention of cracking and it is this common problem which is the focus of the examples of D1 and of the patent. As this problem is explicitly mentioned in both the patent in suit and in D1, and is solved according to the examples of both, the skilled person would objectively recognise this as the technical problem to be solved. Accordingly the situation underlying the findings of T 910/90 does not apply to the present case and consequently the reasoning thereof does not support the position of the [opponent] concerning the definition of the technical problem.

[4.2.1] Decision T 936/96 [2.6] states […] that if an analysis following the framework of the problem-solution approach leads to the conclusion that the subject matter claimed is not inventive, this assessment cannot be changed or overcome if a different problem was also solved, the solution to which was not obvious.

The essence of this decision is thus that the correct approach is that of the problem solution approach, and that conclusions arrived at by application of a divergent analysis, not following the problem solution approach cannot overcome or prevail over the conclusion so reached. In the present case however, following the problem-solution approach, the conclusion is that the claimed subject-matter is inventive. Accordingly, decision T 936/96 does not provide support for the position of the [opponent] that it is appropriate in the present case to depart from the definition of the problem that results from application of the problem solution approach.

[4.2.2] In conclusion, the problem proposed by the [opponent] is neither mentioned in nor derivable from either the patent in suit or D1 since neither document contains – even implicitly – any discussion of matters such as toxicity. Accordingly there are no grounds for departing from the problem as set out in the patent in suit in any manner and in particular no grounds for adopting the formulation of the problem as petitioned by the [opponent].

The Board then found the claim to be inventive and dismissed the appeal.

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