T 0057/84 (Tolylfluanid) of 12.8.1986

European Case Law Identifier: ECLI:EP:BA:1986:T005784.19860812
Date of decision: 12 August 1986
Case number: T 0057/84
Application number: 79103777.3
IPC class: B27K 3/40
Language of proceedings: DE
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Documentation of the appeal procedure can be found in the Register
Bibliographic information is available in: DE | EN | FR
Versions: OJ
Title of application: -
Applicant name: BAYER
Opponent name: -
Board: 3.3.01
Headnote: If a product is required to manifest a particular property (in this case a highly fungicidal effect) under various conditions, the superiority of the invention will depend on whether or not that property is improved under all conditions liable to be encountered in practice and particularly under the various conditions evolved in order to test it (in this case exposure to water and wind). If comparative tests are cited in support of that superiority, it is their combined results that have to be considered. The decisive factor is whether the invention out-performs the substance used for comparison in the tests as a whole (in this case, results in the need to use a significantly lower concentration of the pollutant substance), even if the substance used for comparison proves better in one of the tests.
Relevant legal provisions:
European Patent Convention 1973 Art 56
Keywords: Inventive step
Basis of comparison for substantiating an improvement
Admissible comparison of values from different tests
Comparison of values from different tests


Cited decisions:
Citing decisions:
T 0038/88
T 0470/90
T 0678/02
T 1503/14
T 1914/15

Summary of Facts and Submissions

I. European patent No. 10 635 was granted on 29 April 1981 on the basis of European patent application No. 79 103 777.3, filed on 3 October 1979 and claiming the priority of a German application of 13 October 1978. It has three claims, the first of which reads as follows:

"Use of N,N-dimethyl-N'-p-tolyl-N'dichlorofluoromethylthio sulfamide in wood impregnating agents. (The substance in question is hereinafter referred to as "tolylfluanid").

II. The opponents filed notice of opposition on 14 August 1981 citing the following document: (1) W. Perkow, "Wirksubstanzen der Pflanzenschutz- und Schädlingsbekämpfungsmittel", updated to May 1974, Heading "Tolylfluanid", and requested that the patent be revoked in its entirety owing to lack of inventive step. Subsequently they also cited in support of their submission: (2) R. Wegler, "Chemie der Pflanzenschutz- und Schädlingsbekämpfungsmittel" (1977), Vol. 4, p. 194; (3) EP-A-22 900; (4) Pesticide Manual, 6th ed. (1979), p. 278, and (5) EP-A-38 109.

The literature cited by the patentees included other passages from (4), namely

(4a) Pesticide Manual, 3rd ed. (1972), pp. 172 and 477.

III. In a decision dated 15 December 1983, despatched on 16 January 1984, the Opposition Division revoked the patent on grounds of lack of inventive step. In the Division's view tolylfluanid differed from the known wood preservative dichlofluanid merely in the substitution of the p-tolyl group for the phenyl group. The high solubility of tolylfluanid in organic solvents, cited in support of inventive step, was already known from (1). Its superiority in combatting wood-rotting fungi was not suprising since, as stated in (2), it was also more effective than dichlofluanid in combatting mildew. Finally, the known solubility of tolylfluanid in water, was at only 4%° not such as to give rise to a prejudice against its use and in any case no citations from the literature had been adduced to support that contention.

IV. The appellants (patentees) appealed against the decision on 16 February 1984 at the same time paying the appeal fee. In the statement of grounds that followed on 14 May 1984 they chiefly took issue with the suggestion that merely because the substance was more effective against mildew it could be inferred that it would also be more effective against wood-rotting fungi, supplying the results of fungicide efficiency test in support of their view. Nor could they accept that the higher solubility of tolylfluonid in water was of no consequence. At the Board's suggestion they carried out further comparative tests, this time using internationally recognised testing methods and submitted the results which in their view demonstrated the superiority of tolylfluanid over dichlofluanid in combatting wood-rotting fungi. They further cited in support of their submissions: (6) W. Metzner et al., "Holz als Roh- und Werkstoff" 35 (1977), pp. 233-237 and, on 7 August 1986, (7) Angew. Chemie, 76 (1964) 10, pp. 807-812.

V. The respondents (opponents), on the other hand, argued that while the fact that a fungicide was more effective in combatting a particular fungus did not necessarily mean that it would also be more effective in combatting others, it would suggest that appropriate tests should be performed. They also denied that the results of the new comparative tests submitted by the appellants demonstrated the superior fungicidal properties of tolylfluanid over dichlofluanid, asserting that there was "no consistent pattern". Furthermore they disputed the existence of prejudice attributable to the known higher water-solubility of tolylfluanid, pointing out that solubility calculations based on the two-component agent/water system were not, in view of the likely absorption of the agent by wood, valid in the case of a three-component agent/water/wood system.

VI. At the oral proceedings on 12 August 1986 the parties essentially maintained their positions although the appellants are no longer insisting on the existence of a technical prejudice based on the higher solubility of tolylfluonid in water compared to dichlofluanid. On the other hand, they attach particular importance to the assertion that wood preservatives need to be equally effective when exposed to water and to wind, so that in conducting comparative quality tests it is important to take account of the minimum quantity of each substance required to achieve an adequate effect in both tests. The respondents do not accept this yardstick, maintaining that any comparison must be between like and like i.e. the toxic limits of the two substances when exposed to water and their limits when exposed to wind must be compared separately. They further claim that citation (7) should be disregarded as it was submitted out of time, failing which it should be invoked against the appellants rather than for them since it indicates the use of tolylfluanid as a preservative for materials in general and hence for wood in particular. The appellants request that the contested decision be set aside and the opposition rejected. The respondents request that the appeal be dismissed.

Reasons for the Decision

1. The appeal complies with Articles 106 to 108 and Rule 64 EPC and is therefore admissible.

2. While citation (6) was introduced into the proceedings on 18 November 1985 and is already mentioned in the preamble to the description of the patent in suit (page 2, line 11), the appellants first drew attention to citation (7) in their submission received at the Office five days before the oral proceedings, at which the Board first became aware of it. It accordingly constitutes evidence not submitted in due time within the meaning of Article 114(2) EPC and has been disregarded for the purposes of what follows since the Board does not consider it to be relevant. As the department of first instance rightly found, citations (3) and (5) are not prior publications and hence likewise have to be disregarded. For the purposes of this decision, therefore, only citations (1), (2), (4)/(4a) and (6) are to be considered.

3. The invention falls within the field of wood preservatives.

4. In the Board's view citation (6), which teaches the use of dichlofluanid as a fungicide component in impregnating agents for wood (cf. page 234, Section 2 in conjunction with Tables 2 to 4 on page 235) constitutes the closest state of the art.

5. The problem to be solved by the invention must therefore be to propose the use of another active substance which on balance is more efficient and in particular, by reducing the quantity of the substance required to give adequate protection to the wood, to lessen the environmental pollution resulting from its inevitable emission.

6. The patent in suit proposes to solve this problem by the use of tolylfluanid in the impregnating agent.

7. The first point to be considered is whether the proposed solution really does solve the problem.

7.1 On 18 November 1985 the appellants supplied the results of comparative tests carried out by internationally recognised methods to establish, for dichlofluanid and tolylfluanid respectively the toxic limits (in kg/m3) at which protection against fungus attack either ceases completely ("lower limit") or at which full protection is achieved ("upper limit"). The tests were conducted on three standardised wood/fungus combinations (A: pine sapwood/Coniophora puteana; B: beechwood/Coriolus versicolor; C: pine sapwood/Gloeophyllum trabeum) under three standard conditions (a: without ageing; b: exposed to water; c: exposed to wind) - see the table attached as Annex 1" to the submission of 14 November 1985.

7.2 Since the parties agree that exposure to water and wind are the problem most frequently encountered in practice, the results under conditions b and c will be examined first.

7.2.1 Whereas there is practically no difference between the respective toxic limits recorded for dichlofluanid and tolylfluanid tested on wood/fungus combination A, quite clear differences emerge in the case of combinations B and C, although how these should be interpreted is not immediately evident.

7.2.2 Adopting the respondents' approach and comparing the values for each test separately with upper and lower limits carrying the same weight, the result in the case of combination B would be a narrowing of the range under conditions b and c, in the sense that tolylfluanid would give a better upper limit but not so good a lower one, so that on balance the results would be roughly the same. In the case of combination C the invention would produce a clear improvement under condition b and a marked disimprovement under condition c. The respondents accordingly speak of there being "no consistent pattern", with the result that the problem would appear not to have been solved.

7.2.3 This approach first of all fails to take into account the fact that wood preservation is concerned with the protection of products having a relatively long useful life where the aim is absolutely to prevent attack by wood-destroying fungi, which in the Board's view makes the upper limits much more important than the lower ones. Tolylfluanid, however, out-performs dichlofluanid in terms of the upper limits not only when applied to combination C under condition b but also when applied to combination B under conditions b and c; only in the case of combination C under condition c does dichlofluanid perform better. One most certainly could, therefore, speak of tolylfluanid's achieving a largely consistent pattern of improvement even comparing like with like as the respondents advocate.

7.2.4 Even more significant in the Board's view is the fact that to be of any practical use and reliable in its effects a wood preservative must pass the international standard tests for exposure to wind and water, separately measured, with a sustained adequate preservative effect that is with minimum loss of its active substance. The main factor here is the minimum initial fungicide concentration needed for ecological even more than for economic reasons because, when exposed to the elements, quantities of the fungicide which is usually fairly toxic are released into air and water to pollute the environment. The degree to which a wood preservative is non-polluting of both air and water is governed by the minimum fungicide concentration needed to protect the wood despite simultaneous exposure to both elements. If the values for the two exposure tests are different the higher - and hence less acceptable - value determines the quantity to be used in practice, on the principle that a chain is as strong as its weakest link, since it represents the minimum quantity that will satisfy both criteria. From these considerations, which are fundamental to whether the technical problem defined above has been solved, the following principle may be derived: If a product is required to manifest a particular property at all times and under various conditions, the superiority of the invention will depend on whether or not that property is improved under all conditions liable to be encountered in practice and particularly under the various conditions evolved in order to test it. If comparative tests are cited in support of the invention's superiority, it is their combined results that have to be considered. The decisive factor is whether the invention out- performs the substance used for comparison in the tests as a whole, even if the latter substance proves better in one of the tests. Applying this principle here, in the case of combination B the worse of the two upper limits for dichlofluanid (6.6 under condition c) has to be compared with the worse of the two upper limits for tolylfluanid (6.0 under condition b), and in the case of combination C the worse of the two upper limits for dichlofluanid (5.1 under condition b) has to be compared with the worse of the two for tolylfluanid (2.5 under condition c). The result is an improvement, that is a reduction in the required quantity of the active component, of the order of 10% and 50% respectively. Even including combination A, where there was no evident improvement, the average overall improvement is still significant at 20%, since, as the appellants were able to state in the oral proceedings without contradiction, an improvement even of 10-15% must be regarded as significant.

7.2.5 A rough comparison with the values obtained using Sutter's method (see test results submitted on 1 July 1982) does nothing to alter this conclusion; the results were qualitatively the same. It has therefore been credibly demonstrated that the problem is solved under conditions b and c.

7.3 The Board furthermore considers that a comparison of the two wood preservatives under condition a, that is without simulating exposure to the elements, is relevant in that it reflects conditions when wood preservatives are used for interiors. Here again the values (see comparative test of 18 November 1985) show an improvement of some 55% for combination A, almost 10% for combination B and no change for combination C, i.e. once again an average improvement of approximately 20%. All in all, therefore, the technical problem has been solved.

8. The solution claimed is not mentioned in any of the cited documents and is hence indisputably new.

9. For purposes of inventive step the question to be examined is whether the claimed solution would in the light of the other citations have been obvious to a person skilled in the art attempting to solve the problem defined above on the basis of citation (6).

9.1 Citation (1) describes under "dichlofluanid" and "tolylfluanid" the properties of the two substances for controlling fungal infections in certain living plants. Taken on its own it contains no indication that they might also be used in wood preservatives, that is for the protection of non-living materials. A skilled person merely seeking an additional active agent for wood preservatives might indeed, given his knowledge from (6) concerning the suitability of dichlofluanid as a wood preservative component, be encouraged by citation (1) to test the structurally very similar tolylfluanid. However, since the problem is to provide an improved wood preservative component and since structurally similar compounds usually only produce comparable results, such tests would not seem to hold much promise.

9.2 Citation (2) claims that tolylfluanid is more effective than dichlofluanid in combatting powdery mildew fungi (cf. page 194, second and third line below the second formula). Its relevance is accordingly limited to a specific use in the field of plant protection.

The respondents themselves have admitted (submission of 7 December 1984, page 1, paragraph 1) that this is not enough to warrant a prediction of greater effectiveness in controlling other species of fungus, particularly in the different field of wood preservatives. They do, however, contend that the reference to powdery mildew in (2) would lead a skilled person to carry out the relevant tests, a view the Board is unable to share:

9.2.1 Merely to allege that it would have been obvious to carry out such tests is not sufficient without detailed substantiation. This would involve explaining in which art a person would have needed to be skilled in order to see the conduct of tests as obvious, and the reasons why it would have been so.

9.2.2 In stating that given the reference in (2) to the greater effectiveness of tolylfluanid in treating mildew it would have been obvious for a skilled person to check whether tolylfluanid might not also be more effective than dichlofluanid in combatting wood-destroying fungi, the respondents tacitly assume that skill in the arts of treating wood-destroying fungi and treating fungus disease in crops would be combined in the same person. Even if this is accepted the conclusion that merely because a particular fungicide had been shown to be more effective in treating one given species of fungus (powdery mildew) it was an obvious step to test whether the same fungicide was also more effective in dealing with one or more other species at random is not tenable. On the contrary, what would have to be considered in detail is the nature of the disclosure - such as on the one hand, how many fungus species tolylfluanid was more effective against, and how closely these species were related and on the other against how many how closely related species it was less effective - that would make the idea of carrying out the relevant tests obvious.

9.2.3 Since, however, the respondents disregarded the fact that the person skilled in the art of the disputed patent and the person skilled in plant protection are not in fact one and the same, none of this need be gone into here. The criterion for judging inventive step is whether the solution would have been obvious to the skilled person to whom the problem would normally be entrusted, which in this case is a person skilled in the art of wood preservation. Since the field of plant protection to which (2) belongs is too remote from his own specialist field relating to non-living material, such a person would view the results reported in (2), according to which tolylfluanid is more effective than dichlofluanid in treating powdery mildew, in the light of his limited specialist knowledge and would be unable to see a connection between that fact and his aim of discovering more effective wood preservative agents.

9.2.4 Moreover, the mere fact that the harmful organisms referred to in (2) and those it is desired to combat here both fall under the general heading of fungi - which, incidentally covers such widely different species as the penicillium varieties that produce penicillin and poisonous fungus varieties - would not suggest the idea of testing whether the teaching of (2) was transposable to the field of wood preservation which - as no one disputes - could not have been foreseen. Technically, from the point of view of the wood preservation specialist at any rate, there is no connection between powdery mildew fungi and the three wood-destroying fungi internationally considered as being representative. In these circumstances on the basis of (2) it would not have occurred to the person skilled in the relevant art to carry out the tests regarded as obvious by the respondents.

9.3 Citation (4) relates to an active agent having a completely different structure to tolylfluanid and is therefore immaterial. Moreover it was not published in that form until 1979, after the priority date.

9.4 Citation (4a) was significant in the opposition proceedings in that the appellants quoted what it had to say about the water-solubility of dichlofluanid and tolylfluanid in order to argue the existence of a prejudice against the solution provided by the patent. Since they have ceased to press their contention that such a prejudice exists and since that argument is no longer necessary, now that an improved active component for use in wood preservatives has been provided, this citation need not be considered further.

9.5 Similarly the other citations, neither on their own nor in conjunction with (6), are such as to make the subject-matter of Claim 1 obvious. It therefore involves an inventive step.

10. The acceptability of Claims 2 and 3 derives from that of Claim 1.


For these reasons, it is decided that:

1. The contested decision is set aside.

2. The opposition is rejected.

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