In this appeal the Board examined the inventive step of claim 1 of the main request, which read:
1. Use of an oil-soluble dimercaptothiadiazole compound or derivative thereof as a copper corrosion inhibitor in a tractor hydraulic fluid when in contact with a copper-containing metal wherein the oil-soluble dimercaptothiadiazole compound or derivative thereof is employed in an amount of from 0.01 to 0.2 weight percent, based on the weight of the tractor hydraulic fluid, to protect the copper-containing metal against loss of copper when the tractor hydraulic fluid contains at least 0.25 weight percent water, and wherein the oil-soluble dimercaptothiadiazole compound or derivative thereof has the formulawherein R1 and R2 are hydrogen or hydrocarbyl, n is 0 or 1, x is 1 or 2, y is 1 or 2 and z is 1 or 2.
The Board found document D7 to be the closest prior art and then pursued:
[3.3] As the next step according to the problem-solution approach, it is necessary to determine the problem which the claimed invention addresses and successfully solves in the light of the closest prior art.
[3.3.1] The [patent proprietor] defined the problem to be solved in view of document D7 as lying in the provision of a tractor hydraulic fluid with excellent protection against the loss of copper in the presence of at least 0.25 weight percent of water.
[3.3.2] The board regards this definition of the problem to be unclear, since the term “excellent” could be interpreted in a relative or absolute sense. Indeed, during the course of the proceedings the [patent proprietor] employed this term in each of these senses.
Thus, on the one hand, in the patent in suit, the following is stated ([…], emphasis added):
“It has now been discovered that when an oil-soluble dimercaptothiadiazole compound or derivative thereof is employed in functional fluids that contain water, copper containing metals in contact with the functional fluid are protected from copper loss. This discovery was quite surprising since other compounds known to be copper passivators or copper corrosion inhibitors do not perform nearly as well as the dimercaptothiadiazole compounds or derivatives thereof of this invention.”
Moreover, the patent in suit designates the results pertaining to “Nalco VX 2326” as being a comparative example […], and the [patent proprietor] also argued in written appeal proceedings that this was to be seen as a fair comparison in the sense of decision T 197/86 […].
On the other hand, the [patent proprietor] argued with reference to […] document D29, that the results obtained for the present DMTD derivatives in the JDQ 84 test were below an “absolute” threshold value of 53 ppm disclosed therein, and should therefore be regarded as being “excellent”.
Before each of these uses of the term “excellent” are discussed in more detail below, in points [3.3.4] and [3.3.5], the experimental results relied on by the parties will be outlined under point [3.3.3].
[3.3.3] The following table summarises the data provided for additives according to present formula (I). In all these examples, n is 0, and x and y are 2.
In addition, data was provided for further copper corrosion inhibitors, which is summarised in the following table […].
The data reproduced above were obtained in the JDQ 84 test, according to which a hydraulic pump is operated with a functional fluid contaminated with 1% water, and flow rates and copper levels measured at specified intervals […].
For the sake of completeness, the board wishes to note that, in the patent in suit, the remaining components of the formulations used in the examples are identified in terms of function rather than precise structure […]. Consequently, although indicated as being “formulated according to the formulation of Example 1 of the patent”, the compositions used by the [opponent] in Annexes J, K and I are likely to differ from those employed in the patent in suit in more respects than only the copper corrosion inhibitor. This may explain the different results obtained by the [patent proprietor] and the [opponent] for the compound wherein R1/R2 are C18. Similarly, under point 17 of its statement of grounds of appeal, the [patent proprietor] indicated that the formulations used in Annexes F and G differed with respect to several components from those used in the patent in suit. Consequently, it must be concluded that entries may only be reliably compared within the three sets of data (i.e. that provided in the patent in suit, and by the [patent proprietor] and [opponent], respectively).
[3.3.4] In so far as “excellent protection against the loss of copper” implies an improvement over the closest prior art […], the board is not convinced that the data outlined under point [3.3.3] provide adequate experimental support that this has successfully been achieved.
It is the established case law of the boards of appeal that, in order to be relevant, comparative tests have to meet certain criteria. These include the proper choice of the structurally closest comparative compound to be taken from the closest state of the art (T 181/82 ).
As outlined above […], document D7 relates to the field of tractor fluids and specifically discloses corresponding functional fluids in Table II comprising a DMTD additive, namely, “DMTD/formaldehyde/heptyl phenol”. Such an additive would clearly have greater structural resemblance to those claimed than the benzotriazole additives reproduced above in the second table of point [3.3.3]. The [patent proprietor] asserted that the exact structure of said DMTD derivative was unclear, but did not provide any evidence that the skilled person would not be able to obtain this product based on the information provided in […] document D7, in combination with common general knowledge, if required. Therefore, in the absence of any evidence to the contrary, the board regards the examples of document D7 to represent an appropriate starting point for assessing inventive step. However, no comparative tests were provided with respect to these examples.
It is additionally noted that document D7 specifically discloses further DMTD-based metal passivator components B-5, as outlined above in point [3.2] (cf. formula (XXIV), R’ = isopropyl, hexyl, decyl). The [patent proprietor] argued in this context that there was no example in document D7 of specific functional fluids containing these compounds. However, it is noted that present claim 1 is also completely open as to the nature of the further components in the tractor hydraulic fluid. There was therefore nothing to prevent the [patent proprietor] from designing comparative tests within the meaning of decision T 197/86, such as to demonstrate that any effect had its origin in the distinguishing feature of the invention.
In any case, Comparative Example A provided in the patent in suit is not considered to be pertinent since the compound identified above as “Nalco VX 2326” is neither specifically disclosed in document D7, nor does it accurately reflect the disclosure therein with respect to the structurally closest DMTD-based corrosion inhibitors, as explained in the previous two paragraphs. This comparative example cannot therefore be used to support any improvement with respect to the closest prior art.
Finally, the additional data submitted by the [opponent] demonstrate that compounds falling within present formula (I) are no more effective than the metal passivator according to document D7, tolytriazole […].
Consequently, the data provided, as summarised under point [3.3.3], cannot support the superiority of the additives according to present formula (I) with respect to the closest prior art.
[3.3.5] In a second line of argument, the [patent proprietor] submitted that “excellent protection against the loss of copper” should be seen as defining a result lying below a particular threshold value in the JDQ 84 test […]. However, in this case, the concept of “excellence” can have no other purpose than as a criterion for assessing the suitability of an additive for use as a corrosion inhibitor in a tractor hydraulic fluid contaminated with water.
The [patent proprietor] cited document D29 as disclosing that copper levels of 53 ppm are “not uncommon for a good fluid in this test”. However, this statement is made within the specific context of comparative tests between borated and non-borated calcium sulfonate additives. It cannot be concluded therefrom that values below the level of 53 ppm are by definition “unexpectedly good” regardless of context.
Therefore, the board considers that the inclusion of “excellence” as an absolute concept in the definition of the problem is redundant and, as such, can only lead to confusion as to its meaning.
[3.3.6] Consequently, the problem as defined above by the [patent proprietor] […] requires reformulation.
In the light of document D7 and in view of the fact that the present claims relate to a use rather than a composition, the problem to be solved can be defined as lying in the provision of an alternative method for protecting tractor hydraulic fluids against copper corrosion.
The solution as defined in claim 1 relates to the use of a DMTD derivative of formula (I) in an amount of from 0.01 to 0.2 weight percent in the presence of at least 0.25 weight percent water.
Having regard to the data reproduced above in the first table of point 3.3.3, the board is satisfied that this problem has been solved.
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