T 0354/04 (Mineral fibres III/ROCKWOOL) of 20.1.2009

Summary of Facts and Submissions

I. The appeals lie from the interlocutory decision of the opposition division concerning the maintenance of the European patent No. 0 792 845 in amended form.

II. Claim 1 according to the main request decided upon by the opposition division reads as follows:

"1. Use of a melt composition to make man-made vitreous fibres which are shown to be biodegradable in the lung wherein the composition has an analysis, measured as weight of oxides, which includes

Si02 32 to below 45%

Al203 above 16 up to 26%

CaO l0 to 30%

MgO 2 to 20%

FeO 2 to 15%

Na2O + K2O 0 to 12%

TiO2 0 to 4%

Other Elements 0 to 8%

and the composition has a melt viscosity at 1400ºC of 10 to 70 poise, and in which the fibres have a dissolution rate as defined herein at pH 4.5 of at least 20nm per day."

III. In the contested decision the opposition division inter alia found that the patent was not objectionable for insufficiency of disclosure. More particularly, it accepted that the "analysis of the fibres ... had a composition as indicated in the claim" and that "the viscosity criteria stated in the claim refer to the melt, but a melt having a composition equivalent to the fibres" (point 4.1, second paragraph of the reasons). The opposition division considered (see reasons, point 4.2.1 "Viscosity") that the viscosity values in the claims were values calculated according to the approach published by Bottinga and Weill ("BW" hereinafter) in document C28. Concerning the calculation of the melt viscosity values according to the BW model, the opposition division, taking into account inter alia A14, came to the following conclusions (see point 4): "It can be accepted that BW does not allow calculating all viscosities within the claimed range. However, it was not disputed that certain, if not most compositions can be treated in the proposed way, with plausible results. By extrapolation of the missing D-values from neighbouring values, more compositions can be calculated. Still existing gaps can then be filled, if necessary, by experimental viscosity determination, using standard methods and equipment. The results so obtained can be calibrated against the calculated values in such a way that a consistent set of data is obtained. Although this could sometimes involve considerable experimental effort, compared with the suggested calculation according to BW, it does not imply that the patent could not be worked. Viscosity measurements are routine in the art of mineral fibre manufacture. There is thus no undue experimental burden, as in T 32/85."

IV. The documents considered in the opposition procedure include the following:

A14: Glafo Report 008629 - Fibre P

C24a: Glafo Report 018693-2;

C25: DE 28 56 206 C2;

C28: Y. Bottinga and D. Weill, "The viscosity of magmatic silicate liquids: A model for calculation"; American Journal of Science, Vo.272, May 1972, p.438 to 475;

C34: EP 0 459 897 A1;

A43: Summary of the patent proprietor's arguments concerning the issue of sufficiency of disclosure;

A44: Correspondence Ms Guldberg / Prof. Dingwell dated 2 October and 30 October 2001, respectively.

A46: Letter and "Stellungnahme" of Professor Conradt

V. In their respective statements of grounds of appeal, all three appealing opponents, i.e. appellant 1 (Knauf Insulation GmbH), appellant 2 (Paroc Oy AB) and appellant 3 (Saint-Gobain Isover) objected to the claims that had been considered patentable by the opposition division, inter alia on the ground of insufficiency of disclosure. In particular, appellant 1 raised objections under Article 100(b) EPC inter alia having regard to the term "composition" and to the viscosity criterion comprised in claim 1. In this connection, it discussed the contents of C28 and addressed the difficulties involved in measuring the melt viscosities of compositions as defined in claim 1, by referring also to document

A57: An experimental report of Prof. Suvorov of 2003.

VI. With its statement of grounds of appeal dated 5 July 2004, the appellant and patent proprietor Rockwool International A/S (referred to as "appellant Rockwool" hereinafter) filed five sets of amended claims as main and first to fifth auxiliary requests. It approved the findings of the opposition division concerning sufficiency of disclosure without going into details. It also filed a writ ("A39A") and further references essentially relating to novelty and inventive step issues.

VII. In its reply dated 10 January 2005, appellant 1 inter alia submitted further arguments concerning its objection under Article 100(b) EPC, pointing out inter alia the lack of information in C28 concerning some "other elements" which according to claim 1 may be present in amounts of up to 8% in the melt composition.

VIII. With its letter of 17 January 2005, appellant Rockwool filed a further set of claims as sixth auxiliary request, and a copy of a writ filed in a closely related case (T 440/04) wherein with respect to the issue of insufficiency of disclosure reference was made (see points 25 and 26) to documents A43, C24a and

C48c: Table with viscosity calculations "according to the Bottinga-Weill model".

IX. In its letter dated 24 January 2005 in reply to appellant Rockwool's statement of grounds of appeal, appellant 2 maintained its earlier objections and raised objections under Article 100(c) EPC against some of the pending auxiliary requests of appellant Rockwool.

X. In its further written submissions dated 27 January 2006, 7 April 2006 and 18 August 2006 appellant 1 further developed its argumentation concerning insufficiency of disclosure having regard inter alia to the features "composition" and "viscosity", by referring inter alia to the following further documents, and expressly making the contents of A83 (an opinion of Prof. Jestädt) part of its argumentation:

A80.1: ARP Report A007/4133/06;

A80.2 : Report LAB 849/06 Prof. Meisel - Leoben;

A82.1: Report of Prof. Mengel; and

A82.2 : Report Dr Kirschner - Leoben.

XI. The parties were summoned to oral proceedings.

XII. In its submission of 24 September 2008, appellant 1 cited further documents. In this letter and a further letter of 10 December 2008, it provided further detailed arguments inter alia concerning the "composition" feature and the issue of the calculated viscosity.

XIII. In two written submissions of 14 October 2008 and 18 December 2008, appellant 3 formulated objections under Articles 100(c) and 100(a) EPC having regard to appellant Rockwool's pending requests.

XIV. In a letter dated 15 December 2008, appellant 2 objected to the requests of appellant Rockwool, by raising objections under Articles 100(a)(b)(c), Article 84 and Rule 80 EPC. Concerning the issue of viscosity, appellant 2 referred to the previous submissions of appellant 1.

XV. On 19 December 2009, the board dispatched a communication in preparation of the oral proceedings in which it inter alia addressed the issue of sufficiency of disclosure. It inter alia indicated its provisional opinion concerning the meaning of the term "composition" (point 6.1) and addressed the question of "whether the disclosure of the patent in suit is sufficiently clear and complete to enable the skilled person to actually determine - without undue burden - correct and significant values of the desired properties such as the viscosity ... for a given fibre having a composition falling within the ranges specified in the claims" (point 6.3). Concerning C28, the board also pointed out "that the "D"-values to be used for the calculations are not available for a large part of the compositions falling within the ranges of the present claims" (point 6.4). The board also noted (points 6.7 and 6.8) that appellant Rockwool had already been able to analyse and discuss the content of several documents (including A80.1/A80.2 and A82.1/A82.2) filed by appellant 1 despite their late filing in the appeal proceedings.

XVI. Later on 19 December 2009, the board received a fax from the appellant Rockwool wherein fifteen auxiliary requests were made. Some of the requests were not completely drafted, but merely presented in the form of statements concerning intended combinations to be made amongst some of the fully formulated requests.

The appellant Rockwool inter alia also addressed the issue of insufficiency of disclosure by referring to the further documents

A87: M. Korsgaard et al., "Derivation of the temperature dependent constants for KAlO2 and NaAlO2 in a viscosity predictive model for high aluminosilicate melts"; Glass. Sci. Technol. 76 (2003) No.6, p. 270-275; and

A90: Submissions made by Paroc Group Oy AB in a different case and comprising viscosity calculations (sheet 3 of 3) according to the Bottinga and Weill model.

XVII. Finally, on 14 January 2009, appellant Rockwool filed fifteen sets of claims, namely a new main request and first to seventh and ninth to fifteenth auxiliary requests, respectively. The requests consisted of clean-typed versions of the requests previously on file, but with some additional amendments. The previous eighth auxiliary request was expressly withdrawn. Claim 1 according to the said second auxiliary request reads as follows (amendments to claim 1 according to the main request previously on file highlighted by the board):

"1. Use of a melt composition to make man-made vitreous fibres which are shown to be biodegradable in the lung wherein the composition has an analysis, measured as weight of oxides, which includes

Si02 32 to below 45%

Al203 above 16 up to 26%

CaO l0 to 30%

MgO 2 to 20%

FeO 2 to 15%

Na2O + K2O 0 to below 3%

TiO2 0 to 4%

Other Elements 0 to 8%, and wherein B203 is absent

and the composition has a melt viscosity at 1400ºC of 10 to 70 poise, calculated according to Bottinga and Weill, American Journal of Science volume 272, May 1972, page 455-475 and in which the fibres have a dissolution rate as defined herein at pH 4.5 of at least 20nm per day."

With the same submission, appellant Rockwool also filed copies of letters dated 23 July 2008, 11 November 2008 and 15 June 2004, respectively, which letters had been filed in the appeal proceedings concerning the parent case (T 337/04). The first two of the said letters were attached because they contained appellant Rockwool's comments on sufficiency of disclosure, including comments on documents A80.1/A80.2 and A82.1/A82.2; see points 7.22 to 7.26 of the copy of the letter dated 23 July 2008 and points 2.2.3 and 2.2.5 of the copy of the second letter dated 11 November 2008.

XVIII. During the oral proceedings on 20 January 2009 the appellant Rockwool withdrew its previous main and first auxiliary requests, the request filed as "second auxiliary request" on 14 January 2009 becoming its new main request, and confirmed that there was no eighth auxiliary request.

The exchange of arguments during the oral proceedings was essentially focussed on the admissibility of appellant Rockwool's requests filed on 14 January 2009 and on the issue of sufficiency of disclosure, more particularly having regard to the calculation of melt viscosities according to the BW method described in C28.

At the end of the oral proceedings, the board announced its decision.

XIX. The arguments of the parties, as far as they are relevant for the present decision, can be summarised as follows:

The appellants 1 to 3 requested that all or at least some of the appellant's requests of 14 January 2009 should not be admitted in view of their very late filing. Such a large number of requests which did not converge in terms of the numerous amendments made, and which raised new issues shortly before the oral proceedings, was not admissible pursuant to Article 13 of the RPBA.

In connection with its objections concerning sufficiency of disclosure, appellant 1 argued that although the expression "a melt composition" as used in the preamble of claim 1 was clear, it was questionable whether, considering the contents of the description of the patent in suit, "the composition" defined in claim 1 by virtue of its chemical composition ("analysis") and viscosity was the composition of the melt from which the fibres were made or the composition of the raw material mix used when preparing the melt. Depending on the particular components and processing conditions, it was possible that the composition of the melt differed from the one of the raw material mix and that the composition of the melt changed to some extent before it was actually formed into fibres (documents A80.1/A80.2).

Concerning the calculated viscosity feature, appellants 1 to 3 did not contest that calculations were possible for some compositions, but it was argued that they were not possible for compositions comprising components and/or amounts of components with respect to which C28 did not contain any or at least not enough information on how to consider them in the calculation. More particularly, C28 did not contain any information whatsoever concerning melts comprising ZrO2 and no information concerning melts comprising P2O5 in amounts of up to 8 weight percent. Substantial numbers of such compositions were, however, encompassed by the definition in claim 1. Those two oxides had already been used previously as components in mineral fibre compositions. Apatite was a natural occurring rock containing high amounts of phosphorus, and slags were also mentioned in the description as possible raw materials. The composition as defined in claim 1 also encompassed compositions having viscosities falling outside the claimed range. Therefore, in the absence of any indication in C28 concerning inter alia the Di values to be applied for ZrO2 or P2O5 at higher concentrations, or concerning their estimation by approximation or extrapolation, the skilled person could not calculate the viscosity of such compositions using the model described in C28. Adding higher amounts of phosphorus to silicon was not the same approach as the one referred to in the priority application and was something else than adding very small amounts of phosphorus to silicon. Consequently, the skilled person could not, based on the patent in suit and common general knowledge, reproduce the claimed invention. Moreover, the skilled person could not be expected to find the proper values by an undue experimental burden. In particular, appellant 1 pointed out that the mineral melts under consideration were not Newtonian liquids (C57). High temperature melt viscosity measurements were difficult and not a usual routine for the skilled person (documents A82.1/A82.2) and would lead to different results depending on the measuring method and depending on whether they were measured or calculated. The patent did not contain any information on how the viscosities could be measured and how a measured viscosity could be translated into a calculated one.

Appellant Rockwool argued that the requests filed on 14 January 2009 were only slightly amended compared to the ones filed on 19 December 2008. A large number of requests was necessary in view of the different objections and the volume of the arguments raised. The number of changes was small and the analysis of the changes was not particularly complex. The recent amendments were made to overcome objections that emerged more clearly during the oral proceedings concerning the parent appeal case T 337/04.

According to appellant Rockwool, the composition of the fibres and of the melt from which the fibres were formed were the same and had the analysis recited in the claims. A calculated melt viscosity could also be attributed to a fibre composition. Hence there was no lack of clarity or insufficiency of disclosure in this respect, even when the melt composition changed over time.

Appellant Rockwool argued that C28 was the authoritative reference concerning predictive melt viscosity calculations for geologists in the last two decades. Manufacturers making mineral fibres had relied for years on the BW model for calculating, rather than measuring viscosities of melts from natural stones. As to the melt compositions recited in claim 1, the indication "up to 8%" was intended to deal with the fact that a complex composition comprising five essential oxides and being based on naturally occurring rocks as raw materials would inevitably include ten or more other elements. However, each of these other elements would only be present in a small proportion of at most 1%. Elements present in such small amounts (small molar fraction) would however only provide a very small, negligible influence on the viscosity calculated according to C28. Moreover, C28 gave sufficient guidance on how to deal with several of the other elements for which there were no specific Di values and none of which would in practice be present in amounts of more than 5% (i.e. as major component) in the blend of oxides containing only up to 8% of other elements, such as zinc and barium. In particular, small amounts of phosphorus were to be added to silicon, but this was also applicable to higher amounts of phosphorus. Appellant Rockwool stressed that the patent was directed to the person skilled in the art, i.e. a person actually manufacturing fibres from natural stone, trying to make a commercial product therefrom. He would not think about some theoretical synthetic mixture of several different components. At the oral proceedings, appellant Rockwool however accepted that according to claim 1 P2O5 may be present in an amount of up to 8% by weight. According to BW, even such amounts were to be added to silicon for calculation purposes. Although the compositions recited in the claim covered compositions with viscosities falling outside of the claimed range, these latter compositions were excluded by the wording of the claim. Prompted to consider the content of priority application GB 9500667.2 (page 10), appellant Rockwool pointed out that the calculation approach according to the priority document would only give a slightly different value. Moreover, the patent in suit did not contain this information. In the meantime, the opponents also used BW for their viscosity calculations on phosphorus containing compositions. For instance from A90 it was apparent that appellant 2 used the BW model for viscosity calculations. There was no proof that the inclusion of phosphorous in concentrations of up to 8% would affect the boundaries of the claim so that the skilled person could not decide whether he was inside or outside of the claim. Adding P to Si was the appropriate approach and if this was done, the viscosity could be calculated. There was no subsequent art saying that this approach was wrong or difficult. The content of the said priority document was no prior art and hence not relevant. The work reported in A87 was only a master student's project and was thus not beyond the experimentation that ought to be expected of a person skilled in the art. The authors of C28 explained that there were some gaps and that they invited people to go and fill them, giving some guidance on what needs to be done. At the oral proceedings, appellant Rockwool stated that according to Professor Dingwell, it would take his group only a few weeks to test the guidance given by BW on phosphorus. This could not be considered as an undue experimentation. Hence the disclosure was sufficient.

XX. The appellant Rockwool (patent proprietor) requested that the decision under appeal be set aside and the patent be maintained on the basis of the main request labelled second auxiliary request, alternatively, on the basis of one of the auxiliary requests labelled third to seventh or ninth to fifteenth request, all requests filed on 14 January 2009.

Appellants I, II and III (opponents 01, 02 and 03) requested that the decision under appeal be set aside and that the patent be revoked.

Reasons for the Decision

Late filed evidence (A80.1/A80.2 and A82.1/A82.2)

1. As noted in the board's communication in preparation of the oral proceedings (point 6.7), the appellant Rockwool had the opportunity to comment and did comment in detail on the relevance of inter alia documents A80.1/A80.2 and A82.1. and A82.2 which were cited by appellant 1 at a relatively late stage of the appeal proceedings; see the contents of the two letters dated 23 July 2008 and 11 November 2008 referred to under point XVII hereinabove. The board also considered that more than two years elapsed between the filing of said evidence and the date of the oral proceedings, that said evidence was filed by appellant 1 to further corroborate some of its earlier statements, and that said evidence is of prima facie relevance (see points 6.1.1 and 11.4.1 below).

The board exercising its discretionary power under Article 114(2) EPC thus decided to consider the said documents despite their late filing.

Main request - Admissibility

2. Claim 1 of the present main request filed on 14 January 2009 (labelled "second auxiliary request (December 2008)") differs from claim 1 according to the main request filed with the statement of grounds of appeal of appellant Rockwool dated 5 July 2004 in that:

- it is specified that the melt viscosity value is calculated according to the Bottinga and Weill ("BW" hereinafter) publication C28,

- the upper limit of the weight-% range for Na2O + K2O has been reduced from 12% to 3%, and

- the presence of B2O3 is excluded.

Furthermore, the present main request differs from the main request filed with the statement of grounds of appeal in that four dependent claims, corresponding to dependent claims 8, 12, 16 and 18 of the patent as granted were deleted.

2.1 Concerning the reference to C28, the board notes that in the contested decision, the opposition division held that the viscosity values given in the claims were implicitly values calculated according to C28 (see Reasons, point 4.2.1, first paragraph), although the method used for determining the viscosity was not indicated in the claims. In the appeal proceedings T 337/04 concerning the parent patent (and involving all the parties to the present proceedings), the issue of insufficiency of disclosure having regard to the viscosity feature was discussed at the oral proceedings on 2 and 3 December 2008, during which patent proprietor (Rockwool International) filed amended claims comprising a reference to the method of Bottinga and Weill (C28). Since the claims of the present patent as granted are also silent about the method used for determining the melt viscosity, and since appellant Rockwool previously argued that calculated viscosity values, and not measured values, were appropriate (see e.g. A43, point 34; letter dated 24 December 2004, points 23 and 25), the board considers that the amendment consisting in the introduction of a reference to C28 into claim 1 was a foreseeable possible reaction of appellant Rockwool in the present proceedings.

2.2 The issue of the applicability of the BW method to compositions comprising high amounts of Na2O + K2O and/or "other components" was already previously addressed in the present case in the decision under appeal and in the submissions of appellant 1 (see e.g. its statement of grounds of appeal, point E.2 and its letter dated 10 January 2005, point III). Moreover, the applicability of the BW method to melt compositions comprising high amounts of alkali oxides and/or boron oxide was extensively discussed during the oral proceedings in the appeal case (T 337/04) concerning the parent patent, at the end of which the patent proprietor's appeal was dismissed. Therefore, the board also considers the lowering of the upper limit for the amount of Na2O + K2O and the exclusion of B2O3 as foreseeable possible reactions of appellant Rockwool. Said amendments can thus not have taken the other parties by surprise.

2.3 The amendments addressed under points 1.2 and 1.3 hereinabove were already proposed in appellant Rockwool's second auxiliary request filed on 19 December 2008, i.e. soon after the oral proceedings in the parent case (T 337/04) and one month before the oral proceedings in the present case.

2.4 Concerning the amendments consisting in the deletion of the four dependent claims, the board accepts that they are occasioned by grounds of opposition in accordance with Rule 80 EPC. More particularly, deleted claims 12 and 16 (numbering of the granted claims) had already been objected to under Article 100(c) EPC in the notice of opposition of opponent I dated 6 April 2001 (see "Anlage BMO", page 5, top paragraph). The features of deleted claim 8 (numbering of the granted claim) relating to the sintering temperature (deleted granted claim 8) were objected to under Article 100(b) EPC throughout the proceedings. Finally, the appellants 1 to 3 have not denied that the features of deleted claim 19 (numbering of the granted claim) had been objected to under Article 100(b) EPC in related proceedings, as it was pointed out by appellant Rockwool.

2.5 Considering all the above circumstances, the board does not consider the amendments in the claims according to the present main request to be too complex or to be filed so late that they could not be dealt with by the other parties without the adjournment of the oral proceedings.

The board exercising its discretionary power under Article 13 RPBA thus decided to admit the said main request despite its late filing.

Main request - Amendments

3. Although the specific method for calculating the melt viscosity values as now referred to in claim 1 is expressly mentioned in both the application as filed and the parent application as filed (see WO 96/ 14274; page 12, lines 25 to 28), the board has doubts as to whether the use of a melt composition specifically combining all the amended features of present claim 1 (restricted compositional ranges, properties) is actually directly and unambiguously disclosed therein.

3.1 However, the board does not consider it necessary to discuss the allowability of the various amendments involved under Articles 76(1) and 123(2) EPC, since the patent as amended suffers in any case from an insufficiency of disclosure having regard to the feature relating to the calculated melt viscosity (see points 4 to 15 below).

Main request - Insufficiency of disclosure

4. Insufficiency of disclosure, inter alia with respect to the viscosity feature, was one of the main issues in the present case. According to established jurisprudence of the boards of appeal, the requirement of sufficiency of disclosure is only met provided the invention as defined in the independent claim can be performed by the person skilled in the art within the whole area claimed without the burden of an undue amount of experimentation, taking into consideration common general knowledge and the whole information content of the patent in suit (see decisions T 435/91, OJ 1995, 188, point 2.2.1, third paragraph, of the reasons, and T 409/91, OJ 1994, 653, point 2, first paragraph, penultimate sentence).

5. The invention as claimed is the use of a melt for making man-made vitreous fibres of a specified solubility which are shown to be biodegradable in the lung, wherein said melt must have both

i) a specific composition defined by quantitative ranges for its components, and

ii) a viscosity at 1400ºC in the range of 10 to 70 poise, the viscosity value being calculated according to C28.

In order for the requirement of sufficiency of disclosure to be fulfilled in the present case, the skilled person must thus inter alia be able to calculate according to the BW model as set out in C28 the viscosity values of compositions having analyses throughout the ranges indicated in claim 1 so that he is able to identify and use those compositions having a viscosity value falling within the viscosity range indicated in claim 1 and to discard those which don´t. As will appear from the following, appellant Rockwool's position that the invention is sufficiently disclosed cannot be accepted, since the skilled person cannot simply rely on what is disclosed in C28 to calculate viscosities across the whole area defined by the compositional ranges indicated in claim 1, and is thus not in a position to carry out the claimed invention over the whole ambit of claim 1.

6. The ambit of claim 1

6.1 Meaning of "melt composition" and "composition"

6.1.1 The board acknowledges that in the description of the patent in suit (see e.g. sections [0002], [0044], [0045] and [0058]) the term "composition" is sometimes also used in connection with the composition of the mineral raw material mix to be melted in the course of the fibre fabrication. Depending on the process conditions and the nature of the raw materials, the composition of the melt may differ from the composition of the raw material mix and may change during the melting due to volatilisation, reduction and/or oven lining dissolution phenomena (see e.g. A80.1/A80.2). This was not disputed, see e.g. A43, points 67 and 69; points 7.22 and 7.23 of the letter dated 23 July 2008 attached to appellant Rockwool's written submission of 14 January 2009.

6.1.2 However, despite the somewhat misleading references to the composition of the raw material mix in the description, it is clearly apparent from the patent as a whole including the description that the aim is to identify compositions for providing fibres having controlled properties (inter alia a certain minimum dissolution rate in a specified environment), which properties depend on the composition of the fibres formed. Therefore, the board accepts the view of appellant Rockwool, that the skilled person would understand that "the composition" referred to in claim 1 by virtue of its chemical composition ("analysis") and viscosity is identical with the composition designated in claim 1 as "a melt composition" (emphasis added by the board), i.e. the composition from which fibres having said chemical composition are actually spun, and that this composition need not be identical with the (possibly somewhat different) compositions of the raw material mix or of the melt at some intermediate processing stage.

6.2 Compositions embraced by the compositional ranges

6.2.1 The compositions as defined in claim 1 may in terms of their "analysis" not only comprise the oxides specifically recited, but they may also comprise one or more "other elements" in significant amounts (calculated as oxides) of up "to 8%" by weight in total.

6.2.2 Claim 1 is, however, silent about the nature of these other elements. Only the description of the patent in suit (section [0033]) contains a non-exhaustive list of "other elements" that "can be present in the composition in any amount that does not detract from the desired properties and which does not exceed 8%": P2O5, B2O3, BaO, ZrO2, MnO, ZnO and V2O5 are specifically mentioned as examples of such "other elements". With regard to the amounts of these "other elements", it is indicated in the description only (section [0035]), that "each of the other elements is normally present in an amount of not more than 2%, except that P2O5 and/or B2O3 may be present in larger amounts" (emphasis added by the board). Moreover, it is expressly mentioned (section [0034]) that "often B2O3 is absent" and that "preferably, there is 1 to 8% ... P2O5 and 0 to 5% B2O3". In section [0044] it is stated that the composition to be melted is "typically" formed by blending naturally occurring rock and sand materials and waste materials.

6.2.3 Moreover, claim 1 contains no qualitative indications concerning the nature i) of the raw materials from which the fibres are manufactured or

ii) of the so-called "other elements" and the only quantitative limitation with respect to the latter is that their total amount may be up to 8 % by weight. Therefore, for the board, claim 1 is not limited to the use of compositions made from some specific raw materials, such as the naturally occurring rocks and/or the specific waste materials mentioned in the description (section [0044]). So, the compositions that may potentially be used according to present claim 1 are defined rather broadly and may even comprise oxide components not expressly mentioned as examples in section [0033] of the patent in suit.

6.2.4 It remained undisputed that mineral fibres comprising relatively high amounts of ZrO2 or P2O5 were not unknown in the field of mineral fibres before the priority dates invoked by the patent in suit. This is illustrated e.g. by C25 (a patent publication of Rockwool International A/S of 1988), where mention is made (see page 1, lines 39 to 52) of mineral fibres comprising ZrO2 in amounts of up to 10 % by weight, and by C34 (published 1991) disclosing mineral fibres comprising up to 10 % by weight P2O5 (see abstract or claim 1).

6.2.5 From the above, the board concludes that present claim 1 embraces the use of all those compositions which comprise one or more oxide forming elements not specifically mentioned in the claim or in the description in amounts of up to 8% by weight in total provided these compositions meet - inter alia - the recited viscosity requirement. In particular, the set of compositions having an "analysis" as recited in claim 1 embraces compositions comprising up to 8% by weight of one "other" element, e.g. of P2O5 (as conceded by appellant Rockwool at the oral proceedings), or of one of the other elements mentioned in the description, e.g. ZrO2.

6.3 Calculated viscosity range as a further limitation

As acknowledged by the appellant Rockwool, the compositional ranges recited in claim 1 embrace compositions with viscosities falling outside of the claimed range (see e.g. the two examples mentioned in point 2.2.9 of the letter dated 11 November 2008 referred to under point XVII above). Claim 1 is, however, restricted to the use of those melt compositions which not only have an "analysis" falling within the recited compositional ranges, but which additionally meet the requirement of a melt viscosity value falling within the recited numerical range, the value to be considered being the viscosity value calculated according to the BW model described in C28.

7. The Bottinga and Weill model as described in C28

7.1 C28 describes a model for calculating, instead of measuring, the viscosities of multi-component silicate liquids (i.e. melts) based on their composition according to the formula

FORMULA/TABLE/GRAPHIC

(1),

wherein eta is the viscosity, Xi is the mole fraction of the i-th component, Di is a constant associated with component i over a restricted range (in terms of mole percent SiO2) of composition, and each temperature has a particular set of Di constants. The Di constants tabulated in C28 (Table 3 on pages 452 to 456) were determined by mathematical methods based on measured viscosity data (2440 data points) extracted from a preferred set of published references that were available to the authors (C28: page 441, Table 1).

7.2 C28 is primarily concerned with a model for predicting, by means of calculations, the viscosities of naturally occurring magmatic liquids, and the application of the model to geologic problems involving viscosity (see e.g. the title; the abstract; page 460, second paragraph, first and last sentence; page 471, "Concluding remarks", first sentence). Applications in the field of mineral fibre manufacturing are not addressed. The authors of C28 specifically mention (in the paragraph bridging pages 442 and 443) that having regard to the evaluation of the reliability of the method more measured data would be "very desirable" for the components K2O, Fe2O3, TiO2, FeO and MnO, i.e. even for some of the components explicitly recited in present claim 1.

7.3 The authors of C28 indicate (see page 451, "Viscosity calculations") that in some cases a direct viscosity calculation is not possible for lack of input data in Table 3, which "makes it necessary to estimate Di values for certain components". Since the "paper is concerned primarily with geological applications", the authors have "chosen several compositions representative of the magmatic range in order to discuss the calculations and necessary approximations". The authors of C28 recommend that "for all major components", i.e. components present in amounts of > 5 mole %, "only the Di values actually listed in table 3 be used" and they consider that viscosity calculations will only be possible as far as the Di values are available for the temperature ranges concerned, although the linear temperature dependence may be extrapolated to some extent (see page 457, second paragraph).

7.4 More particularly, having regard to some specific cases where the necessary Di values are missing for the relevant SiO2 mole fraction range in Table 3, the authors of C28 give some specific guidance on how to carry out the calculations based on certain estimations or approximations (see the section "Viscosity calculations" extending over pages 451 and 457 to 460). Some express guidance is given (see page 451, last paragraph, page 458, first paragraph, to page 459, first paragraph) on how to deal with certain components of the representative magmatic compositions, i.e. with "small amounts" of phosphorous, with potassium in the form of KAlO2, with "minor amounts" (< 5 mole%) of TiO2 or of sodium oxide in the form of NaAlO2 in the composition range 0.35 < XSiO2 < 0.45 (page 458, last paragraph), and with "minor" MO components (i.e. bivalent metal oxides).

7.5 According to C28 (page 457, first paragraph), a "small amount of phosphorous usually present in magmas is added to silicon (compare calculations in table 4)". From the said Table 4, which lists the compositions of several representative magma types, it can be gathered that the amounts considered as "small" are in the range of 0.5 to 0.53 % by weight.

7.6 However, in developing and testing their model, the authors of C28 have not considered compositions comprising significant amounts of some of the other oxides specifically mentioned in the patent in suit as possible "other elements" in the patent in suit (section [0033]). For instance, ZnO, B2O3 and ZrO2 are not mentioned in C28 at all, and V2O5 is only mentioned in connection with measurements which were disregarded as source of input data by the authors (see C28: page 441, last full sentence; Tables 1, 4 and 6).

7.7 The board notes that it has not been disputed by the respondents that the viscosities of certain SiO2 based melt compositions to be used in mineral fibre production can actually be calculated using the BW model described in C28, instead of being measured. The board accepts that each oxide of an "other element" which is present only in a minor amount of up to about 1% (corresponding to a mole fraction of 0.01) may - at least when considered individually - only have an insignificant impact on the viscosity as determined according to formula (1) because the corresponding term DiXi may be very small and may thus contribute very little to the sum of these terms and hence to the calculated viscosity.

7.8 However, in the present case, the question that must be answered in the first place is not whether a calculated viscosity value falls within or without the numerical range in the claim but whether the person skilled in the art, considering the contents of the patent in suit and of C28, as well as common general knowledge on the filing date of the patent in suit, was actually in a position to calculate the viscosities of melt compositions having analyses throughout the ranges indicated in claim 1. As already set out under point 6.2.5 hereinabove, the compositional ranges in claim 1 include, inter alia, compositions comprising relatively high amounts of ZrO2 or P2O5. Only when the skilled person is in a position to actually calculate the viscosity value for these compositions he will be able to check thereafter whether this calculated value falls within or without a given range.

8. The limitations in the teaching of document C28

C28 describes a model for predicting instead of measuring the viscosities of multi-component silicate melts. At first glance C28, which is praised as the authoritative reference in viscosity calculations, appears to describe a simple calculation of the viscosity of multi-component melts requiring not much more than filling in available data in the formula (1). When trying to apply the calculation model of C28 to the compositions embraced by the compositional ranges in claim 1, the skilled person is however confronted with difficulties due to a lack of data and to gaps in the information provided in C28. The teaching in C28 is incomplete insofar as the BW model as set out therein is not fully applicable to all the compositions as defined in present claim 1.

8.1 Teaching in C28 is incomplete insofar as certain

Di values are missing

The straightforward viscosity calculation according to formula (1) of C28 requires that for each component of the melt composition present in a significant amount, the corresponding Di value must be known. As far as ZrO2 and P2O5 are concerned, C28 does not report any of the Di values needed for the calculation. The straightforward viscosity calculation according to formula (1) of C28 is thus not possible for the compositions comprising up to 8 weight % ZrO2 or P2O5.

8.2 Teaching in C28 is incomplete insofar as certain necessary estimations are not indicated

8.2.1 As mentioned under point 7.3 above, the authors of C28 indicate that in some cases, estimated or approximated Di values of certain components may be used in the calculation when the required Di values are not tabulated.

8.2.2 However, C28 contains no guidance whatsoever (see sections "Chemical dependence of viscosity - General", pages 443 to 444, and section "Viscosity calculations", pages 451 and 457 to 460) having regard to approximations or estimations that could be applied in the case where a composition contains ZrO2 in more than just a negligible amount, let alone in a higher amount of up to 8% by weight.

8.2.3 Having regard to phosphorus, C28 does not comprise any express information on how to deal with amounts substantially higher than the "small amounts" of at most 0.53 % by weight reported in Table 4.

8.3 Having regard to compositions comprising ZrO2 or P2O5 in amounts of up to 8 % by weight, C28 thus not only lacks the required Di values but also any indications concerning the specific approximations to be applied. The board thus concludes that the skilled person was not in a position to calculate or estimate in a reliable way a viscosity value "according to Bottinga and Weill, American Journal of Science Volume 272, May 1972, page 455 - 475" as required by claim 1 for at least those compositions falling within the compositional ranges of claim 1 which comprise high amounts of up to 8 % by weight ZrO2 or P2O5.

9. Incomplete teaching in C28 calls estimations to be made by the skilled person into question

9.1 According to the appellant Rockwool, C28 teaches to make best efforts to approximate or estimate or derive averages when a particular value is missing (see e.g. A43, point 36). By doing so, the skilled person would be able to calculate the melt viscosities of the compositions throughout the whole area claimed. These considerations are, however, not convincing for the board since reliable estimations cannot be made for all the compositions falling within the compositional ranges in claim 1 for the following reasons.

9.2 The authors of C28 indeed state that in some cases "lack of sufficient input data makes it necessary to estimate Di values for certain components" (page 451, section "Viscosity calculations", second sentence). Notwithstanding the fact that some guidance is given in C28 on how to estimate or approximate the required values in the case of some typical magmatic compositions reported in Table 4 of C28, no guidance is given in C28 on how to estimate, approximate or derive appropriate Di values for ZrO2 and P2O5 when present in high amounts of up to 8 % by weight (see points 8.2.2 and 8.2.3 hereinabove).

9.3 Instead, it must be noted that the authors of C28 emphasise (see the first sentence on page 446) that "a satisfactory quantitative model of viscosity-composition variation must be more discriminating than the usual "network former" and "network modifier" categories". However, C28 does not contain theoretical considerations which could be considered as a basis for enabling the skilled person to make appropriate, scientifically sound estimations of the Di values for ZrO2 and for P2O5 in amounts of up to 8 % by weight.

9.3.1 In particular, nothing can be derived from C28 concerning the interaction of ZrO2 with a silicate network in a multi-component melt and appellant Rockwool did not present arguments in this respect.

The board notes that the patent in suit also does not comprise any information or guidance in this respect.

9.3.2 As far as phosphorus is concerned, the specific reasons that actually lead the authors of C28 to recommend adding "small amounts" of phosphorus to silicon are not indicated either. Hence, no information can be gathered from C28 concerning an appropriate way for approximating or estimating the Di value for P2O5 present in the composition in amounts of up to 8 % by weight, i.e. in amounts that may be several times higher than the "small amounts" reported in Table 4 of C28. Therefore, the board does not accept that C28 suggests this approach and - in the absence of corroborating evidence to this effect - that the skilled person would necessarily envisage using this approach even in the case of compositions comprising P2O5 in relatively high amounts of up to 8 % by weight. For the skilled person, using this approach would merely be one conceivable possibility amongst others, and its validity would need to be tested and possibly confirmed by experimental investigations (in this respect see point 11 below).

This view is corroborated by the fact that in one of the applications from which the patent in suit claims priority (GB 9500667.2, page 10, lines 18 to 22), i.e. at a time before the filing date of the patent in suit, Rockwool considered that a different approximation for taking P2O5 into consideration in the calculation was appropriate, namely to "equalise 1 mole % P2O5 with 2 mole % Si + 1 mole % Ca" and undertook laboratory tests which "proved that this approximation is valid within actual chemical ranges".

The board notes that in the patent in suit (sections [0025] and [0034] of the description) it is merely stated that P2O5 may be added to "maintain" or "adjust" the "melt properties", which include in particular the viscosity and the liquidus temperature (see section [0003]). According to section [0025] a decreased amount of SiO2 (tending to lower the viscosity) is to be compensated by the addition of P2O5. Although the skilled person could arguably derive therefrom that an addition of P2O5 tends to raise the viscosity, the board considers that the information contained in the quoted passages is not specific enough to constitute a guidance for estimating the appropriate Di value to be used when calculating the viscosity of compositions containing P2O5 in relatively high amounts of up to 8 % by weight according to formula (1) given in C28.

9.4 Since the authors of C28 recommend that for components present in relatively high amounts (particularly for components present in amounts beyond the somewhat arbitrary limit of > 5 mole %) only the Di values listed in table 3 are to be used, the board takes the view that the skilled person would consider that for compositions of compositions containing ZrO2 or P2O5 in relatively high amounts of up to 8 % by weight, an estimation of the corresponding Di value would not be appropriate, let alone without experimental confirmation.

9.5 No evidence was brought to the board showing that a specific approach for estimating the respective Di values for the ZrO2 or P2O5 components present in relatively high amounts of up to 8 weight % in compositions as referred to in present claim 1 belonged to common general knowledge at the filing date of the patent in suit.

More particularly, neither documents C24a, C48c and A90 referred to by appellant Rockwool in connection with the issue viscosity calculation, nor any of the other documents relied upon by appellant Rockwool in the present appeal proceedings, provide any additional information in this respect. C24a and A90 are silent about the presence of phosphorus or zirconium. Document C48C reports results of "viscosity calculations according to the Bottinga-Weill model", but P2O5 is expressly referred to as being "outside model".

10. Incomplete teaching in C28 does not permit the extension of the applicability of the BW model

10.1 Having regard to conceivable ways of estimating or approximating Di values that might potentially be used by the skilled person in the calculation of viscosities along the lines indicated in C28, it is expedient to also consider document A14, a report issued by the renowned Glafo Research Institute. The contents of A14 confirm that the skilled person would not necessarily consider extending the applicability of the BW model beyond what is explicitly taught by C28.

10.1.1 From A14 it can be gathered that the experts of Glafo consider the text of C28 to be not "fully conclusive" and that there can be "difficulties with these calculations" (C14, page 1, sentence underneath the table of values). Referring to the specific composition which is identical to the composition "P" of the patent in suit, the Glafo experts conclude that the model of BW is "not suitable to calculate melt viscosities at 1400ºC" of certain compositions (see page 2, penultimate paragraph; page 3, first sentence) containing a component (10.1 mole % NaAlO2) for which the required Di value and a specific estimation methodology are missing in C28 (see entire page 2). The Glafo experts apparently did not consider it to be appropriate to estimate a Di value. They calculated a viscosity value based on choosing 0 as the value for the missing Di factors (bottom of page 2).

10.1.2 Although the composition specifically dealt with in A14 does not comprise phosphorus or zirconium, A14 corroborates the finding of the board that in the absence of useful indications in C28, the skilled person was not in a position to make a reliable estimation of the appropriate Di values for ZrO2 and P2O5 present in high amounts of up to 8% by weight and, therefore, to calculate the viscosity of such compositions "according to" C28. In this connection the board notes that document C24a concerns a different composition (9.0 mol % NaAlO2 but in a different XSiO2 range) of which Glafo was able to calculate the viscosity according to C28 based on available Di values and an indications concerning the approximation of the Di value to be used for KAlO2 (see entire document).

10.1.3 The appellant Rockwool considered that the approach as adopted by the Glafo experts was not appropriate (see A43, points 35 to 40) since no effort was made to estimate or derive a suitable average value. In its view, the information contained in C28 and the patent in suit permitted an estimation of a Di value for NaAlO2 in the XSiO2 range form 0.35 to 0.45, which was more appropriate than choosing the value 0 and led to a lower error in the calculation. This view of appellant Rockwool is confirmed by Professor Dingwell and Professor Conradt, but only as far as the amount of NaAlO2 comprised in a composition with an XSiO2 in the 0.35 to 0.45 range is relatively close to the 5 mole % (i.e. the value distinguishing minor from major components according to C28); see A44; third paragraph of Ms Guldberg's letter; second, third and fifth paragraph of Professor Dingwell's reply and A47; page 2 of the "Stellungnahme". The opinions of these two experts are thus not in contradiction with the conclusions of the Glafo experts in A14, which relate to a different composition (10.1 mole % NaAlO2, i.e. as major component) for which C28 contains less of the data needed for calculating the viscosity.

10.2 The skilled person taking into account common general knowledge could not derive from C28 and the patent in suit the estimations or approximations to be applied in the case of compositions comprising ZrO2 or P2O5 in amounts of up to 8 % by weight. To fill these gaps in C28, the skilled person could only speculate about appropriate estimations based on considerations not addressed in C28, and the viscosity calculated would thus depend on speculative Di values. In other words, depending on the specific underlying assumptions adopted by the skilled person, the estimations would not in any case give the same result.

Under these circumstances, for the board, the skilled person would have to grope in the dark because he is not in a position to calculate the viscosity of these compositions as required by claim 1, i.e. based on the information comprised in C28, the patent and common general knowledge alone.

11. Incomplete teaching in C28 calls for undue amount of experimentation

11.1 According to the appellant Rockwool, C28 also invites the skilled person to fill the gaps in the available data by means of additional measurements. Such measurements, as far as they were necessary at all, e.g. to test some adopted approximations, would not go beyond what ought to be expected from the skilled person. The board also does not agree with this argument for the following reasons.

11.2 The authors of C28 indeed suggest that their model can be improved and/or completed by gathering data from further viscosity measurements (see e.g. the sentence bridging pages 442 and 443, the first full sentence on page 458). Whilst their work was focussed on magmatic liquids and geologic applications and therefore did not consider compositions containing high amounts of certain components, they expressly left it "to others to develop additional applications and also to test further its validity as additional data are gathered" (see page 471, "Concluding remarks") (emphasis added by the board).

11.3 In order to be able to calculate viscosity values according to the model of C28 for the compositions referred to under point 6.2.5, the skilled person would thus first have to investigate experimentally the quantitative impact of specific components such as ZrO2 and P2O5 on the viscosity of multi-component silicate melts in the SiO2 mole fraction range(s) concerned. The investigations necessary for obtaining the correct Di values or for checking the validity of an approximation not disclosed in C28 involve high temperature melt viscosity measurements, the evaluation of the data and cross-checking how they fit with the BW model.

11.4 The necessary viscosity measurements and the subsequent evaluative work cannot, however, be considered as a matter of mere experimental routine. As will appear from the following, the obtainable results will depend to some extent on choices to be made when carrying out the measurements and when evaluating their significance. Different choices will inevitably lead to different results.

11.4.1 As noted in C28 (and confirmed in point 34 of A43), accurate high-temperature viscosity measurements on multi-component silicate melts are difficult to perform and imply various considerations concerning inter alia the appropriate experimental setup, method and parameters. The difficulties to be expected by the person skilled in the art of high temperature viscosity measurements when trying to measure viscosities of composition as defined in claim 1 are also illustrated by documents A82.1/A82.2 (see in particular point 3 of A82.2).

11.4.2 Difficulties having a potential impact on the results of the measurements, such as bubble formation, volatilisation of components and contamination of sample by the crucible proper control of the compositions are also extensively addressed in C28 itself, e.g. at page 440, third paragraph; page 441; page 442, first paragraph; page 461, second paragraph; page 465; page 466, first paragraph.

11.4.3 In this connection it is worth noting that Bottinga and Weill excluded several scientific publications of viscosity measurements, i.e. measurements carried out by persons skilled in the art of viscosity measurements, as data sources due to their contradiction with other measurements or because of insufficient evidence for the control of composition, and in particular measurements relating to the system SiO2-Al2O3-CaO with additions of inter alia P2O5 (see C28, page 441). The skilled person reading C28 would thus expect these measurements to be particularly critical.

11.5 Moreover in C28 it is assumed that the melts behave as Newtonian fluids under the conditions considered in the document (page 439, second paragraph). As can be gathered from the results presented in A57, this is not necessarily the case in compositions as defined in claim 1. Moreover, a measured viscosity value for a given melt may deviate substantially from the viscosity calculated according to C28 for the same melt (see e.g. Table 5 of C28, calculated versus measured viscosity values at low XSiO2 values).

11.6 Neither the patent in suit nor C28 contain more specific instructions on how viscosity measurements and evaluations required for determining the results to be used in the BW model for P2O5 or ZrO2 in compositions as defined in claim 1 could be carried out. Moreover, a calibration of the measured data against C28 or patent data is not possible since these two documents do not contain examples of compositions comprising ZrO2 or P2O5 in amounts of up to 8 % by weight. The skilled person is thus forced to develop its own research program. For the board, there are however limitations to what can be expected from the skilled person.

11.7 As indicated in C28, with the newly gathered experimental data the skilled person will have to verify the validity of the calculation model, and of any approach based on approximations (see point 9.3.2 hereinabove). Using the words of the authors of C28, this work can be considered as the development of an additional application.

11.8 From the above, the board thus concludes that the experimental and evaluative work required from the skilled person represents an undue amount of experimentation in the sense of decision T 435/91 (loc. cit.) The skilled person would actually be forced to generate all necessary data in order to be in a position to calculate the viscosities of melt compositions having analyses throughout the full ranges indicated in claim 1. This undue amount of experimentation requires more than routine means and manipulations and requires more than merely common general knowledge. The skilled person cannot be expected to embark on the scientific research programme required for testing the validity of given approximations and/or for finding the correct Di values for the calculation of the parameter value which is needed for identifying those amongst the compositions falling within the compositional ranges of claim 1 which are actually the ones to be used according to the invention. Or, in other words, it is not up to the skilled person to overcome the limitations of the patent in suit and fill gaps left by the patentee in the information.

11.9 However, even if the skilled person would decide to carry out such experimental work, he would not be in a position to know with certainty whether Bottinga and Weill and/or the scientific community would also qualify the results obtained as the "right" ones to be used in calculating the melt viscosity "according to Bottinga and Weill, American Journal of Science volume 272, May 1972, page 455-475". So, the skilled person would be left in doubt whether or not he can rely on his results. Hence, the viscosity definition as chosen by the patentee does not allow the skilled person to decide in a reliable manner and for a substantial set of compositions embraced by the compositional ranges of claim 1, whether or not he is working the claimed invention.

The consequences that variations in the quality of the data or of the approximations underlying the BW model as described in C28 can have are illustrated by the post-published document A87. Whereas the Di value for NaAlO2 at 1400ºC to be used in the XSiO2 range of from 0.35 to 0.45 is 9.15 according to the "neighbouring table approach" described in C28, it was determined to be much lower, namely 4.50, based on the experimental work done according to A87 (see Table 5).

11.10 At the oral proceedings, appellant Rockwool did not rely on any further documents cited in the course of the present opposition and appeal proceedings in connection with the specific issue addressed hereinabove. The board is also not aware of a cited document comprising additional information in this respect and which would lead to different conclusions.

12. Summarising, on the filing date of the patent in suit the skilled person was not in a position to calculate, at least not without the burden of an undue amount of experimentation, the melt viscosity value "according to Bottinga and Weill, American Journal of Science volume 272, May 1972, page 455-475" as required by present claim 1 for a substantial number of melt compositions falling within the compositional ranges recited in the claim. Consequently, the skilled person would not be able to identify in a reliable way throughout the whole ambit of the claim those melt compositions which meet both the compositional requirements and the viscosity requirement and may thus be used according to claim 1.

13. The board thus concludes that the patent does not disclose the invention as claimed in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art (Article 100(b) EPC).

14. Consequently, the appellant's main request cannot be allowed.

Auxiliary requests

15. The respective claims 1 of the remaining twelve auxiliary requests of appellant Rockwool (labelled "third" to "seventh" and "ninth" to "fifteenth auxiliary request", respectively) also refer to the use of a melt composition having a chemical composition defined by ranges for the relative amounts of the various components and a viscosity calculated according to C28 within a certain range.

15.1 Like claim 1 of the main request, the respective amended claims 1 according to all these auxiliary requests refer to compositions having "an analysis, measured as weight of oxides, which includes ... Other elements 0 to 8%, and wherein B2O3 is absent" and "a melt viscosity at 1400ºC ... calculated according to Bottinga and Weill, American Journal of Science volume 272, May 1972, page 455-475" in the given range of either "10 to 70 poise" or "12 to 70 poise" (emphasis added by the board).

15.2 The further amendments consist in the narrowing of some of the compositional ranges of the melt composition, the exclusion of B2O3 as a component, an additional reference to the dissolution rate in connection with the showing of biodegradability, the narrowing of the viscosity range, the inclusion of a reference to end-products which may contain said fibres and/or the inclusion of a reference to end uses of bonded products made from said fibres. The restricted compositional ranges are such that they still include compositions with viscosities falling outside the respective numerical ranges (see point 6.3 above).

16. The appellant did not argue that these further amendments were intended to overcome the objections under Article 100(b) EPC insofar as the latter concern the calculation of viscosities according to C28 for compositions comprising up to 8% other elements, and they are prima facie not suitable for that purpose.

Under these circumstances, questions raised by the other parties concerning the admissibility of each of these requests need not be addressed since these requests must in any case fail for the same reasons as the main request as will appear from the following.

17. For carrying out the invention as defined the respective claims 1 of each of these requests the skilled person must inter alia be in a position to calculate, according to the method described in C28, the viscosity of melts having compositions throughout the ranges indicated in the respective claims 1, i.e. inter alia compositions comprising "other elements" in amounts of up "to 8%". Consequently, the considerations under points 4 to 14 hereinabove apply mutatis mutandis to each of the present auxiliary requests.

The present auxiliary requests are thus likewise objectionable under Article 100(b) EPC (insufficient disclosure).

18. Consequently, none of the present auxiliary requests is allowable.

ORDER

For these reasons it is decided that:

The decision under appeal is set aside.

The European patent is revoked.