T 0179/05 () of 30.11.2006

Summary of Facts and Submissions

I. The grant of the European patent No. 0 835 885 in the name of Nippon Shokubai Co., Ltd, in respect of European patent application No. 97 117 334.9 filed on 7 October 1997 and claiming priority of the Japanese patent application JP 27094996 filed on 14 October 1996 was announced on 27 February 2002 (Bulletin 2002/09) on the basis of 11 claims.

Independent Claims 1 to 5, and 8 to 11 read as follows:

"1. A water-swellable crosslinked polymer, which has a total pore volume of pores with a pore size in gels of 5.1-27 nm of 60 v/v % or more relative to the entire amount of a physiological salt solution absorbed into the polymer, wherein the pore volume of pores with a pore size in gels of 5.1-27 nm (PV (5.1-27 nm)) is defined by a method comprising the following steps of:

A. allowing a water-swellable crosslinked polymer (W1 g), which stands in an equilibrium state swollen with a physiological salt solution (W2 ml), to fall again into an equilibrium state by adding a physiological salt solution (W3 ml, concentration Ci %) of a thread-ball-shaped molecule with molecular diameter R to the polymer; and then filtering off the polymer as swollen with the physiological salt solution; and then measuring concentration Cf % of the thread-ball-shaped molecule in the resultant filtrate;

B. defining PV (0-R) (ml/g) as PV (0-R) (ml/g) = (W2+W3) [1-{W3/(W2+W3)} x (Ci/Cf)]/W1;

C. determining PV (0-5.1 nm) and PV (0-27 nm) using a thread-ball-shaped molecule with R of 5.1 nm and a thread-ball-shaped molecule with R of 27 nm and

D. defining PV (5.1-27 nm) as PV (5.1-27 nm) = PV (0-27 nm) - PV (0-5.1 nm).

2. A water-swellable crosslinked polymer, which has a total pore volume of pores with a pore size in gels of 5.1-27 nm of 80 v/v% or more relative to the entire amount of an ion-exchanged water absorbed into the polymer, wherein the pore volume of pores with a pore size in gels of 5.1-27 nm (PVW (5.1-27 nm)) is defined by a method comprising the following steps of:

E. allowing a water-swellable crosslinked polymer (W1 g), which stands in an equilibrium state swollen with ion-exchanged water (W4 ml), to fall again into an equilibrium state by adding an ion-exchanged water solution (W5 ml, concentration Ci%) of a thread-ball-shaped molecule with molecular diameter R to the polymer; and

then filtering off the polymer as swollen with the ion-exchanged water; and then measuring concentration Cf% of the thread-ball-shaped molecule in the resultant filtrate;

F. defining PVW (0-R) (ml/g) as PVW (0-R) (ml/g) = (W4+W5) [1-{W5/(W4+W5)}x(Ci/Cf)]/W1;

G. determining PVW (0-5.1 nm) and PVW (0-27 nm) using a thread-ball-shaped molecule with R of 5.1 nm and a thread-ball-shaped molecule with R of 27 nm; and

H. defining PVW (5.1-27 nm) as PVW (5.1-27 nm) = PVW (0-27 nm) - PVW (0-5.1 nm).

3. A water-swellable crosslinked polymer, which has an average pore size in gels of 10-30 nm and a standard deviation of 11.5 or less in pore size in gels when the polymer is swollen with ion-exchanged water, wherein the average pore size is defined by a method comprising the following steps of:

I. allowing a water-swellable crosslinked polymer (W1 g), which stands in an equilibrium state swollen with ion-exchanged water (W4 ml), to fall again into an equilibrium state by adding an ion-exchanged water solution (W5 ml, concentration Ci%) of a thread-ball-shaped molecule with molecular diameter R to the polymer; and

then filtering off the polymer as swollen with the ion-exchanged water; and then measuring concentration Cf% of the thread-ball-shaped molecule in the resultant filtrate;

J. defining PVW (0-R) (ml/g) as PVW (0-R) (ml/g) = (W4+W5) [1-{W5/(W4+W5)}x(Ci/Cf)/W1;

K. determining PVW (0-5.1 nm), PVW (5.1-9 nm), PVW (9-11.8 nm), PVW (11.8-27 nm), PVW (27-56 nm), and PVW (0-56 nm) using a thread-ball-shaped molecule with R of 5.1 nm, a thread-ball-shaped molecule with R of 9 nm, a thread-ball-shaped molecule with R of 11.8 nm, a thread-ball-shaped molecule with R of 27 nm, and a thread-ball-shaped molecule with R of 56 nm; and

L. defining the average pore size as:

average pore size = [2.55 x PVW (0-5.1 nm)

+ 7.05 x PVW (5.1-9 nm)

+ 10.4 x PVW (9-11.8 nm)

+ 19.4 x PVW (11.8-27 nm)

+ 41.5 x PVW (27-56 nm)]

/[PVW (0-56 nm)].

4. A process for producing a water-swellable crosslinked polymer as claimed in claim 1, comprising the steps of subjecting a hydrophilic high molecule to a crosslinking reaction in an aqueous solution, wherein the crosslinking reaction is carried out in such a manner that the change in the concentration of a solid content falls within the range of ±30 %.

5. A process for producing a water-swellable crosslinked polymer as claimed in claim 1, comprising the steps of subjecting a hydrophilic high molecule to a crosslinking reaction in an aqueous solution, wherein the crosslinking reaction is carried out in such a manner that the concentration of a solid content falls within the range of 2 to 40 %.

8. A method for measuring a pore volume of pores with a specific range of size in a water-swellable crosslinked polymer as claimed in claim 1, which is swollen with a physiological salt solution, comprising the steps of:

allowing said swellable crosslinked polymer (W1 g), which stands in an equilibrium state swollen with physiological salt solution (W2 ml), to fall again into an equilibrium state by adding a physiological salt solution (W3 ml, concentration Ci%) of a thread-ball-shaped molecule with molecular diameter R to the polymer; and then filtering off the polymer as swollen with physiological salt solution; and then measuring concentration Cf% of the thread-ball-shaped molecule in the resultant filtrate; and

thereby determining volume PV (O-R) of physiological salt solution, as absorbed into pores having a size of O-R in a state swollen with physiological salt solution, from the following equation:

PV (0-R) (ml/g) = (W2+W3) [1-{W3/(W2+W3)} x (Ci/Cf)]/W1.

9. An absorbent article which comprises a water-swellable crosslinked polymer, wherein the water-swellable crosslinked polymer has a total pore volume of pores with a pore size in gels of 5.1-27 nm of 60 v/v% or more relative to the entire amount of a physiological salt solution absorbed into the polymer, wherein the pore volume of pores with a pore size in gels of 5.1-27 nm (PV (5.1-27 nm)) is defined by a method comprising the following steps of:

A. allowing a water-swellable crosslinked polymer (W1 g), which stands in an equilibrium state swollen with a physiological salt solution (W2 ml), to fall again into an equilibrium state by adding a physiological salt solution (W3 ml, concentration Ci%) of a thread-ball-shaped molecule with molecular diameter R to the polymer; and then filtering off the polymer as swollen with the physiological salt solution; and then measuring concentration Cf % of the thread-ball-shaped molecule in the resultant filtrate;

B. defining PV (0-R) (ml/g) as PV (0-R) (ml/g) = (W2+W3) [1-{W3/(W2+W3)}x(Ci/Cf)]/W1;

C. determining PV (0-5.1 nm) and PV (0-27 nm) using a thread-ball-shaped molecule with R of 5.1 nm and a thread-ball-shaped molecule with R of 27 nm and

D. defining PV (5.1-27 nm) as PV (5.1-27 nm) = PV (0-27 nm) - PV (0-5.1 nm).

10. An absorbent article which comprises a water-swellable crosslinked polymer, wherein the water-swellable crosslinked polymer has a total pore volume of pores with a pore size in gels of 5.1-27 nm of 80 v/v % or more relative to the entire amount of an ion-exchanged water absorbed into the polymer, wherein the pore volume of pores with a pore size in gels of 5.1-27 nm (PV (5.1-27 nm)) is defined by a method comprising the following steps of:

E. allowing a water-swellable crosslinked polymer (W1 g), which stands in an equilibrium state swollen with ion-exchanged water (W4 ml), to fall again into an equilibrium state by adding an ion-exchanged water solution (W5 ml, concentration Ci%) of a thread-ball-shaped molecule with molecular diameter R to the polymer; and then filtering off the polymer as swollen with the ion-exchanged water; and then measuring concentration Cf % of the thread-ball-shaped molecule in the resultant filtrate;

F. defining PVW (0-R) (ml/g) as PVW (0-R) (ml/g) [sic] (W4+W5) [1-{W5/(W4+W5)}x(Ci/Cf)]/W1;

G. determining PVW (0-5.1 nm) and PVW (0-27 nm) using a thread-ball-shaped molecule with R of 5.1 nm and a thread-ball-shaped molecule with R of 27 nm; and

H. defining PVW (5.1-27 nm) as PVW (5.1-27 nm) = PVW (0-27 nm - PVW (0-5.1 nm).

11. An absorbent article which comprises a water-swellable crosslinked polymer, wherein the water-swellable crosslinked polymer has an average pore size in gels of 10-30 nm and a standard deviation of 11.5 or less in pore size in gels when the polymer is swollen with ion-exchanged water, wherein the average pore size is defined by a method comprising the following steps of:

I. allowing a water-swellable crosslinked polymer (W1 g), which stands in an equilibrium state swollen with ion-exchanged water (W4 ml), to fall again into an equilibrium state by adding an ion-exchanged water solution (W5 ml, concentration Ci%) of a thread-ball-shaped molecule with molecular diameter R to the polymer; and

then filtering off the polymer as swollen with the ion-exchanged water; and then measuring concentration Cf% of the thread-ball-shaped molecule in the resultant filtrate;

J. defining PVW (0-R) (ml/g) as PVW (0-R) (ml/g) = (W4+W5) [1-{W5/(W4+W5)}x(Ci/Cf)]/W1;

K. determining PVW (0-5.1 nm), PVW (5.1-9 nm), PVW (9-11.8 nm), PVW (11.8-27 nm), PVW (27-56 nm), and PVW (0-56 nm) using a thread-ball-shaped molecule with R of 5.1 nm, a thread-ball-shaped molecule with R of 9 nm, a thread-ball-shaped molecule with R of 11.8 nm, a thread-ball-shaped molecule with R of 27 nm, and a thread-ball-shaped molecule with R of 56 nm; and

L. defining the average pore size as:

average pore size = [2.55 x PVW (0-5.1 nm)

+ 7.05 x PVW (5.1-9 nm)

+ 10.4 x PVW (9-11.8 nm)

+ 19.4 x PVW (11.8-27 nm)

+ 41.5 x PVW (27-56 nm)]

/ [PVW (0-56 nm)]."

Claims 6 and 7 were process claims directed to elaborations of the subject-matter claimed in Claims 4 and 5.

II. Two Notices of Opposition were filed against the patent, as follows:

(i) by Stockhausen GmbH & Co. KG (Opponent I), on 27 November 2002 and

(ii) by Kimberly Clark Worldwide, Inc. (Opponent II), on 27 November 2002.

Both Opponents requested the revocation of the patent on the grounds of lack of novelty and lack of inventive step (Article 100(a) EPC), and of insufficient disclosure (Article 100(b) EPC).

These objections were supported inter alia by the following documents:

Dl: Dextran Fractions; Amersham Biosciences data file 18-1153-41 AA, 2001-11;

D2: US-A-4 090 013;

D4: US-A-5 230 958;

D7: Declaration of Joy Holgerson, dated November 22, 2002;

D8: Declaration of Hoa Wilhelm, dated November 26, 2002;

D9: Martin M. Chui et al, "Measurement of the Porous Microstructure of Hydrogels by Nuclear Magnetic Resonance" Journal of Colloid and Interface Science, Vol. 174, 1995, pages 336-344;

D10: W0-A-95/12632;

Dl1: EP-B-0 105 634; and

Dl3: Declaration of Michael Niemeyer, dated 27 November 2002.

III. By a decision announced orally on 24 November 2004 and issued in writing on 6 December 2004, the Opposition Division rejected the oppositions.

According to the decision of the Opposition Division, the grounds of opposition raised by the Opponents did not prejudice the maintenance of the patent as granted. According to the decision the subject-matter of the granted claims met the requirements of Article 83 EPC, since the examples clearly indicated how to obtain a water swellable crosslinked polymer having a total pore volume falling within the meaning of the claims, and since the method for determining the pore volume of pores was completely reported in Claims 1 and 3. The Opposition Division did not accept the arguments of the Opponents that it was impossible to determine the pore volume according to the method disclosed in the patent in suit with precision and accuracy, since the tests carried out by the Opponents having been carried on a commercial product (Favor 880) and not on a polymer resulting from the examples of the invention were not an exact repetition of the specific embodiments indicated in the opposed patent.

According to the decision the subject-matter of the claims was novel over documents D2, D4, D9, D10, and D11. Furthermore, according to the decision, it had not been shown by the Opponents that the prior use of the product Favor 880 (cf. D13) complied with the requirements of the claims of the disputed patent.

Concerning inventive step, it was held that none of the cited documents suggested that the use of polymer having a total pore volume with a pore size in gels as indicated in Claims 1 to 3 would result in an improvement of the absorbency as shown by the examples. Furthermore, the method of measuring the pore volume according to Claim 8 had not been disclosed nor suggested by the cited documents.

IV. Notices of Appeal were filed on 4 February 2005 by Appellant I (Opponent I) and on 9 February 2005 by Appellant II (Opponent II) with simultaneous payment of the prescribed fee.

V. With its Statement of Grounds of Appeal filed on 15 April 2005, Appellant II submitted the following documents:

D17: Graph showing the maximal concentration of Dextran (thread-ball shaped molecule) in the filtrate as a function of the swelling capacity of the polymer; and

Annex 2: Test Data for samples prepared according to D2.

It also presented arguments concerning insufficiency of disclosure which may be summarized as follows:

(i.1) It had been held in the decision under appeal that the opposed patent satisfied the requirements of Article 83 EPC since it contained examples of the synthesis of polymers which allegedly satisfied the requirements of the test procedures set out in Claims 1 to 3.

(i.2) Claims 1 to 3 however were not limited to the particular swellable polymers synthesized in the Examples.

(i.3) During the opposition procedure, both Opponents had submitted test data demonstrating that the tests referred to in the claims did not produce meaningful results in relation to the prior art product Favor 880.

(i.4) Favor 880 water-swellable polymer tested by the Opponents was a crosslinked partially neutralised polyacrylic acid as in the Examples in the opposed patent.

(i.5) The Patent Proprietor had provided no explanation as to why the claimed tests did not work with Favor 880.

(i.6) The very small difference in concentration of the Dextran for 0% and 100% exclusion could not be measured reliably using the method of the patent.

(i.7) Blank measurements showed that there was an inherent error in the method of at least about 0.6%.

(i.8) As shown by Annex 2, there was a standard deviation of 0.004% in the filtrate concentration.

(i.9) This would imply a grand total estimate of error equal to about 1.4%.

(i.10) For a superabsorbent having a capacity of 60 g/g no exclusion of the Dextran would give a concentration of 0.5000% whereas total exclusion would give a concentration of 0.5051% (see also D17).

(i.11) Thus, for a 60 g/g capacity superabsorbent, and taking into account the error of 1.4%, it was impossible to distinguish between complete exclusion and none at all using the method of the patent.

(i.12) Repeating the analysis for the case of 100 g/g superabsorbent capacity, the error in determining excluded volume would be massive i.e. 84.5%. With a polymer having a 290 g/g capacity, the error in excluded volume would be reduced to 26%.

(i.13) However, a swelling capacity of 290 g/g was significantly higher than the swelling capacity of the vast majority of known superabsorbent polymers.

(i.14) The test procedures set out in Claims 1 to 3 were therefore flawed in that by their very nature they could not provide meaningful results for the vast majority of absorbent polymers.

(i.15) Further tests had been carried on samples of absorbent polymer prepared according to D2. The process disclosed in Examples I and II of D2 fell within at least Claims 4, 5 and 7 of the opposed patent (cf. Annex 2).

(i.16) These results further confirmed that the claimed tests were fundamentally flawed and hence that the patent was insufficient.

(i.17) They also showed that even a polymer prepared according to the process claimed in the opposed patent did not fall within Claims 1 to 3.

(i.18) In view of the evidence submitted, the burden of proving sufficiency should be shifted to the Patent Proprietor.

(i.19) Insufficiency arguments set out in the letter dated 24 September 2004 relating to the term "thread-ball-shaped molecule with molecular diameter R" in Claims 1 to 3 of the patent in suit were also maintained.

VI. With its Statement of Grounds of Appeal filed on 18 April 2005, Appellant I submitted the following documents:

Tables A and B: tests results on Samples 9 and 10 of D2; and

D18: Declaration of Dr. H. Schmidt dated 15 April 2005.

The arguments concerning insufficiency of disclosure presented by Appellant I in its Statement of Grounds of Appeal may be summarized as follows:

(i.1) The pore volume test of the patent in suit was neither exact nor sound and of course not reproducible. It yielded for example negative pore volumes or percentages above 100%.

(i.2) Samples 9 and 10 of D2 were state of the art samples which exactly followed the teaching of the patent in suit (cf. Claim 5).

(i.3) The pore volume tests carried out by Appellant II on these Samples clearly showed that meaningless results were obtained.

(i.4) The Appellants had sufficiently proved lack of enablement.

(i.5) According to numerous decisions of the Technical Boards of Appeal of the EPO the patent in suit must contain sufficient information to carry out the invention within the whole area that was claimed, i.e. not only with respect to the examples given in the patent in suit.

(i.6) Sample 9 of D2 clearly showed with a V/V% average of 46.53 (cf. Table A) that the claimed range of 60% or more was not fulfilled. Therefore, the claims in general and in particular Claims 1 and 5 were not sufficiently disclosed.

(i.7) Furthermore, the measurements in ion-exchange water of Samples 9 and 10 showed that they neither exhibited a V/V% average of 80% or more nor possessed an average of the Average Pore Size of 10-30 nm. Consequently, the subject-matter of Claims 2 and 3 was likewise not sufficiently disclosed, since both samples were however embodiments of the patent in suit.

(i.8) Reference was made in that respect to decision T 226/85 in which it was stated "it is, however, important to note that for sufficiency not only the exemplified specific embodiments must be reproducible but any embodiment which falls within the ambit of the claim."

(i.9) The Appellants had provided numerous pieces evidence that the pore volume tests of the patent in suit did not work.

(i.10) The Patent Proprietor had failed to submit evidence showing that the tests gave meaningful results.

(i.11) The shift of burden of proof to the Patent Proprietor was justified.

VII. In its letter dated 2 August 2005, the Respondent argued essentially as follows concerning insufficiency of disclosure:

(i.1) The tests carried out by the Appellants could not be considered as objective because they were not an exact repetition of the specific embodiments indicated in the patent in suit.

(i.2) The tests on Samples 9 and 10 of document D2, as provided by Appellant I, did not present in detail all the necessary operational data.

(i.3) A polymer usually had a molecular weight range and a molecular weight distribution. The test experiments provided by Appellant I did not show such data.

(i.4) Appellants I and II had argued that the burden of proof had been transferred to the patentee to provide evidence supporting that the method for determining the pore size volume was sufficiently disclosed.

(i.5) It was however the permanent jurisdiction of the Boards of Appeal in the European Patent Office that for proving an insufficient disclosure of an invention lack of reproducibility of the examples provided in the respective patent in suit was to be demonstrated.

(i.6) Any experimental data provided in respect of a sample of super absorbent Favor 880 could not be considered as providing objective evidence that the embodiments described in the present patent were objectionable under Article 83 EPC.

VIII. In a communication dated 8 August 2006 annexed to the summons to oral proceedings scheduled to take place on 30 November 2006, the Board drew the attention of the Parties to issues concerning the determination of the pore volume and the manufacture of the claimed products in view of the disclosure of document D2.

IX. With its letter dated 26 October 2006, the Respondent submitted a first auxiliary request consisting of six claims and a second auxiliary request consisting of a single claim.

Independent Claims 1 and 6 of the first auxiliary request corresponded to granted Claims 2 and 10. Independent Claims 2 and 3 and dependent Claims 4 to 5 were said to be based on granted Claims 4 and 5, and on granted Claims 6 and 7.

Claim 1 of the second auxiliary request corresponded to Claim 10 as granted.

It also presented arguments concerning insufficiency of disclosure which may be summarized as follows:

(i.1) Neither Appellant had exactly repeated the specific embodiments described in the patent in suit with respect to the measurement method of the pore volume of a water-swellable crosslinked polymer as claimed in claims 1 to 11 of the patent in suit as granted.

(i.2) Therefore, due to the lack of evidence, sufficiency of disclosure of the patent in suit should be acknowledged.

(i.3) According to the permanent jurisdiction in the EPO, the only requirement with respect to information not explicitly disclosed in a patent with respect to the requirements of sufficiency of disclosure was that information which was not explicitly disclosed in a patent sufficiently, was obvious to a person skilled in the art in a way that a detailed description of said information was superfluous in the light of the general knowledge of a skilled person.

(i.4) This applied to the way of determining the total amount of absorption for physiological salt solution and to the temperature at which the absorbency should be determined.

(i.5) Reference was made to paragraph [0029] of the patent in suit and to the standard procedures to determine the absorbency of super absorbent materials EDANA 442.1-99 and 441.1-99 as well as JIS K 7224-1996 according to which the parameters were measured by swelling the super absorbent materials or polymers at 23 ± 2 ºC.

(i.6) The same applied with respect to the so-called thread-ball shaped molecules which were used in the measurement of the pore volume as described in the present patent. Reference was also made to the letter of Appellant I dated November 27, 2002, page 5, second paragraph).

(i.7) The molecular diameter of said thread-ball- shaped molecules was known to a person skilled in the art for example from catalogues of commercially available products of said thread-ball-shaped molecules.

(i.8) The Respondent contradicted the allegations of Opponent II with respect to the high measurement errors (about 1.4 %).

X. The arguments presented by Appellant I in its letter dated 27 October 2006 and concerning insufficiency of disclosure may be summarized as follows:

(i.1) Reference was made to decision T 172/99 of 7 March 2002 (not published in OJ EPO).

(i.2) It had been shown that the pore volume test was not sufficiently disclosed for at least two polymers which were covered by the claim language.

(i.3) Contrary to the Patent Proprietor's assertion, the test experiments carried out by Appellant I provided both the film swell index for Samples 9 and 10 and the weight average molecular weight of the polyacrylate precursor prepared according to Example I of D2 (cf. D18).

XI. In its letter dated 27 October 2006, Appellant II argued essentially as follows:

(i) All the claims in the opposed patent referred either directly or indirectly to pore volume as measured by a particular non-standard test procedure.

(ii) It was for the Patent Proprietor to demonstrate that the patent in suit contained a full disclosure of the method by which the parameter was to be measured.

(iii) Claim 3 of the granted patent referred to an average pore size and a standard deviation in pore size. There was no indication whatsoever either in the claim or in the description of the patent as to how the standard deviation in pore size should be calculated.

(iv) Furthermore, a calculation made by Appellant II, showed that apart from comparative Example 3, the values for the average pore size reported in Table 2 of the patent in suit did not agree with those calculated using the equation given in Claim 3.

XII. Oral proceedings took place before the Board on 30 November 2006.

At the oral proceedings the discussion essentially focussed on the question of sufficiency of disclosure in view of the methods for determining the pore volumes used for characterizing the polymers according to granted Claims 1 and 2, of the determination of the average pore size and standard deviation thereof, and the method for determining the pore volume of water swellable polymer according to granted Claim 8.

(a) The Appellants, while having indicated that they essentially relied on the arguments and evidence presented in that respect during the written phase of the appeal for supporting their objection of insufficient disclosure, made additional submissions in that respect which may be summarized as follows:

(a.1) The methods for determining pore volumes as disclosed in granted Claims 1, 2 and 8 were not restricted to polymers meeting the requirements of Claims 1, 2 and 3. They should also be applicable to water swellable polymers of the prior art.

(a.2) Favor 880 and SXM 9543 which had been used in the tests carried out by Appellant II were superabsorbent polymers, based on partially neutralized polyacrylic acid as the polymers used in the Examples of the patent in suit.

(a.3) The patent in suit did not define the thread-ball shaped molecule used for carrying out the test for determination of pore volume.

(a.4) Document D1, which referred to Dextran products did not even refer to this term. Furthermore, the diameters which could be calculated from the Stoke's radii indicated in D1 (page 2) for the various Dextran products did not correspond to the diameters indicated in the patent in suit for the Dextran products used as "thread-ball shaped molecule".

(a.5) Stoke's radius might be determined in two different ways, either using a dynamic method (diffusion) or a static method (light scattering). These methods did not lead to the same results.

(b) The Respondent, while also essentially relying on the arguments presented in the written phase of the appeal made further submissions in order to support its view that the patent in suit did not lack sufficiency of disclosure in these respects. They may be summarized as follows.

(b.1) The criteria for sufficiency of disclosure was the possibility of repeating the examples of the patent in suit.

(b.2) The Respondent had no difficulties for carrying out the tests. The accuracy of the test was about 1%.

(b.3) The skilled person would know what was meant by "thread ball shaped molecules" and by the diameter of such molecules.

(b.4) An explanation to the problems encountered by the Appellants could have been that they had used polymers with an insufficient absorbency.

(b.5) As shown by document D17, the difference in the Dextran concentration in the filtrate between a 0% exclusion and a 100% exclusion increased with the absorbency of the polymer.

(b.6) The patent in suit was concerned with superabsorbent polymers which were known to have a high absorbency in physiological solution, e.g. more than 100g/g.

(b.7) Furthermore, the absorbency of these polymers was known to be even higher in ion-exchanged water than in physiological solution.

(b.8) The Respondent had developed its own method for calculating an average pore size of water swellable crosslinked polymer. Nevertheless, the standard deviation would however be determined as known by the skilled person.

XIII. The Appellants requested that the decision under appeal be set aside and the patent be revoked.

The Respondent requested that the appeals be dismissed, or, in the alternative, that the decision under appeal be set aside and the patent be maintained on the basis of Claims 1 to 6 of the first auxiliary request, or on the basis of Claim 1 of the second auxiliary request, both submitted with letter dated 26 October 2006.

Reasons for the Decision

1. The appeals are admissible.

Main request

2. Sufficiency of disclosure

2.1 As indicated in paragraph [0005] of the patent in suit, the aim of the invention is to provide water swellable crosslinked polymers which display sufficient high absorption capacity when put under an increased pressure in a state combined with fibrous matters. According to paragraph [0009], this can be achieved only if the swellable crosslinked polymers have a specific pore size on a molecular level.

2.2 Swellable crosslinked polymers meeting these requirements are represented by the polymers according to Claim 1 and by the polymers according to Claim 2 of the patent in suit.

2.3 While Claim 1 is directed to a water swellable crosslinked which is characterized only by the feature that it has a total pore volume of pores with a pore size in gels of 5.1-27 nm of 60 v/v % or more relative to the entire amount of a physiological salt solution absorbed into the polymer, as determined by the method defined in that claim, Claim 2 relates to a water swellable crosslinked polymer which is characterized only by the feature that it has a total pore volume of pores with a pore size in gels of 5.1-27 nm of 80 v/v % or more relative to the entire amount of an ion exchanged water absorbed into the polymer, as determined by the method defined in that claim.

2.4 It is thus clear that the essential feature of the claimed water swellable crosslinked polymers according to Claim 1 and to Claim 2 resides in the total pore volume of pore in the range of pore size of 5.1 to 27 nm as determined by the methods indicated in these claims.

2.5 In this connection, the Board observes that the respective pore volumes referred to in Claim 1 and in Claim 2 are determined by specific methods which have been developed by the Respondent itself.

2.6 Consequently, it must be considered that the specific pore volumes referred to in Claim 1 and in Claim 2 which are the only essential features for selecting water swellable crosslinked polymers in order to carry out the claimed invention are newly formulated and, hence, unfamiliar parameters which have to be determined by specific and newly developed methods.

2.7 As stated in the decision T 172/99 in the case of claimed subject-matter relying on a newly formulated and, hence, unfamiliar parameter to define the solution of a technical problem by which a relevant effect is achieved, the patentee, who has the duty of making a full and fair disclosure of his invention to the public (Article 83 EPC), is under a particular obligation to disclose all the information necessary reliably to define the new parameter not only (i) in a formally correct and complete manner such that its values can be obtained by a person skilled in the art without undue burden, but also (ii) in a manner which reliably retains the validity of the parameter for the solution of the technical problem for the application or patent in suit as a whole in the sense that the values routinely obtained will not be such that the claimed subject-matter covers variants incapable of providing the relevant effect or, therefore, of solving the associated technical problem.

2.8 Since, in the present case, it is the methods of determination of the specific pore volumes which give their technical significance to these features for the implementation of the claimed invention, it thus follows that the implementation of the claimed invention presupposes that the values of the specific pore volume as indicated in Claim 1 and in Claim 2 could be determined in a reliable and reproducible manner by the very specific methods mentioned in these claims.

2.9 In this connection, the Board notes that the published application (EP-A2-0 835 885) provides in the passage from page 7, line 54 to page 8, line 31 practical technical information as to carry out the determination of the pore volume in gels in a state of swollen with a physiological salt solution.

2.10 According to page 7, line 54 to page 8, line 5, about 10 mg (W1 g) of a water-swellable crosslinked polymer is precisely weighed out and then swollen by placing it into a screw tube of 100 ml along with about 30 ml (W2 ml) of a physiological salt solution, and then allowed to stand stationary for 60 hours. Afterwards about 30 ml (W3 ml) of a 1.00 % (Ci %) physiological salt solution of dextran with a molecular diameter of 51 Å (i.e. 5.1nm)("Dextran T10", made by Pharmacia Biotech Co., Ltd.) is added, and the tube is capped and then shaken for 60 hours with a shaker ("Double Shaker" NR-150, made by Taitec Co., Ltd.). After this shaking, the resultant swollen gel is filtered off with a glass filter. The filtrate is subjected to GPC analysis to determine the concentration (Cf %) of dextran in the filtrate from a calibration curve as made beforehand from the peak height of dextran with a known concentration (emphases by the Board).

2.11 Thus, according to page 8, lines 15 to 20, the pore volume of pores having a diameter of 0-51 Å, i.e. between 0-5.1 nm is given by the formula:

PV(0-5.1nm)(ml/g) = (W2+W3)[1-{W3/(W2+W3)}x(Ci/Cf)]/W1.

2.12 According to page 8, lines 21 to 31 the pores volume of pores between 0 and 270 Å (0 and 27 nm) and 0 and 560 Å (0 and 56 nm) are determined in the same way as the pore volume of pores between 0 and 51 Å (i.e. 0 and 5.1 nm) except that dextrans with a molecular diameter of 270 Å (27 nm) and with a diameter of 560 Å (56 nm) (i.e. Dextran T500 and T2000) are respectively used instead of a dextran with a molecular diameter of 51 Å (i.e. 5.1 nm).

2.13 The Board also notes that the published application provides in the passage from page 8, line 40 to page 9, line 20 the corresponding technical information as to carry out the determination of the pore volume in gels in a state swollen with ion exchanged water.

2.14 According to page 8, lines 40 to 49, about 10 mg (W1 g) of a water-swellable crosslinked polymer is precisely weighed out and then swollen by placing it into a screw tube of 100 ml along with about 30 ml (W4 ml) of ion-exchanged water, and then allowed to stand stationary for 60 hours. Afterwards about 30 ml (W5 ml) of a 1.00 % (Ci %) ion-exchanged water solution of dextran with a molecular diameter of 51 Å (i.e. 5.1 nm) ("Dextran T10", made by Pharmacia Biotech Co., Ltd.) is added, and the tube is capped and then shaken for 60 hours with a shaker ("Double Shaker" NR-150, made by Taitec Co., Ltd.). After this shaking, the resultant swollen gel is filtered off with a glass filter. The filtrate is subjected to GPC analysis to determine the concentration (Cf %) of dextran in the filtrate from a calibration curve as made beforehand from the peak height of dextran with a known concentration (emphases by the Board).

2.15 Thus, according to page 9, lines 1 to 5, the pore volume of pores having a diameter of 0-51 Å, i.e. between 0-5.1 nm is given by the formula:

PV(0-5.1nm)(ml/g) = (W4+W5)[1-{W5/(W4+W5)}x(Ci/Cf)]/W1.

2.16 According to page 9, lines 7 to 11 the pores volume of pores between 0 and 90 Å (0 and 9 nm) 0 and 118 Å (0 and 11.8 nm), 0 and 270 Å (0 and 27 nm) and 0 and 560 Å (0 and 56 nm) are determined in the same way as the pore volume of pores between 0 and 51 Å (i.e. 0 and 5.1 nm) except that dextrans with molecular diameters of 90 Å (9 nm), 118 Å (11.8 nm), 270 Å (27 nm), and 560 Å (56 nm) (i.e Dextran T40, T70, T500 and T2000) are respectively used instead of a dextran with a molecular diameter of 51 Å (i.e. 5.1 nm).

2.17 In that respect, it is noted by the Board that Appellant II has carried tests (cf. document D8) on samples of superabsorbent polymers (i.e. Favor 880 and SXM 9543 both of Stockhausen, Inc) in order to determine their pore volumes in a physiological salt solution and in ion-exchanged water according to the methods set out in Claims 1 and 2.

2.18 In that respect, it is observed that page 3 of D8 describes the procedure according to which these tests have been carried out as follows:

"Test 1 : Physiological Salt Solution (All measurements must be EXACT)

1. Weigh out 0.01g of SAM (as received) into a screw tube of l00 ml

2. Add 30ml of 0.9% saline solution, close cap tightly

3. Let it soaked for 60 hours

4. Add 30 ml of a 1% physiological salt solution of Dextran (99g of 0.9% saline solution + 1g of Dextran T10), close cap tightly

5. Shake the tube for 60 hours using "Double Shaker" NR-150. made by Taitec Co. Ltd)

6. Filter the swollen gels via a glass filter and collect the filtrate

7. Subject the filtrate to a GPC analysis to determine the concentration (Cf%) of Dextran from a calibration curve as made beforehand from the peak height of Dextran with a known concentration.

8. Repeat steps 1-7, but replacing Dextran T10 with Dextran T500

9. Repeat steps 1-7, but replacing Dextran Tl0 with Dextran T2000".

and

"Test 2 : Ion-Exchanged Water (All measurements must be EXACT)

1. Weigh out 0.01g of SAM (as received) into a screw tube of l00 ml

2. Add 30 ml of 0.9% ion-exchanged water, close cap tightly

3. Let it soaked for 60 hours

4. Add 30 ml of a 1% ion-exchanged water of Dextran (99g of 0.9% saline solution + 1g of Dextran Tb), close cap tightly

5. Shake the tube for 60 hours using "Double Shaker" NR-150. made by Taitec Co. Ltd)

6. Filter the swollen gels via a glass filter and collect the filtrate

7. Subject the filtrate to a GPC analysis to determine the concentration (Cf%) of Dextran from a calibration curve as made beforehand from the peak height of Dextran with a known concentration.

8. Repeat steps 1-7, but replacing Dextran T10 with Dextran T40

9. Repeat steps 1-7, but replacing Dextran Tl0 with Dextran T70

10. Repeat steps 1-7, but replacing Dextran Tl0 with Dextran T500

11. Repeat steps 1-7, but replacing Dextran Tl0 with Dextran T2000."

2.19 Consequently, it is in the Board's view, indisputable that the tests carried out by the Appellant II for the determination of the pore volumes of these samples of superabsorbent polymers have been carried out in the framework of the instructions given by the patent in suit for carrying these determinations according to the methods referred in Claims 1 and 2.

2.20 It is further clear that even stricter standards have been applied by Appellant II when carrying out its analyses since, according to the test procedures disclosed in D8, it is required that "All measurements must be EXACT) while, according to the patent in suit, a certain degree of uncertainty is apparently tolerated (cf. the wording "about" used in combination with the values W1, W2, and W3, W4 and W5).

2.21 The results of the pore volume determination in physiological salt solution made by Appellant II are presented in the Table on page 4 of D8.

2.22 In that respect, the Board observes that for the determination of the pore volume of Sample C in the range 0-5.1 nm, five measurements of the final concentration Cf of dextran in the filtrate have been carried out, which give values of the measured final concentration of 0.497, 0.501, 0.501, 0.498 and 0.504% respectively, and which allow to calculate the corresponding values of pore volume of respectively

-36.22, +11.98, +11.98, -24.10 and +47.62 ml/g. Independently of the fact that negative and hence meaningless values of the pore volume would appear to be obtained, the Board further observes that a slight variation in the measured value of the Cf of 0.003% (absolute) i.e. 0.6% relative leads to a quadrupling of the measured pore volume (11.98 to 47.62 ml/g). The extreme sensitivity of the determined pore volume to the measured value of the final concentration Cf is further illustrated, in the Board's view, in that Table, by the fact that a very slight variation of 0.001% absolute, i.e. 0.2% relative of the value of the measured Cf already induces a relative variation of 23% of the determined pore volume (cf. Sample B, PV (0-56)).

2.23 In this connection, the additional tests carried out by Appellant II on partially neutralized polyacrylic acid polymers prepared according to Sample 9 (Sample referred as W108601) and to Sample 10 (Sample referred as W108602) of Example 2 of D2 (cf. Annex 2, and Table 1 thereof submitted with the Statement of Grounds of Appeal), show that either negative i.e. meaningless results (cf. Sample W108602, only negative values of pore volume for the pore size range 0-5.1 nm) or drastically divergent results (e.g. a pore volume between 3.01 and 54.44 for the Sample W108601 in pore diameter range of 0 to 56nm, and a pore volume varying between 21.99 and 73.49 for the Sample W108602 in the same pore diameter range) in terms of pore volume are obtained for the same polymer when using the method disclosed in the patent for determining the pore volume of these polymers. Although Annex 2 does not disclose expressis verbis the respective final concentration Cf measured when carrying the method for determining the pore volume in the pore diameter ranges (i.e. 0-5.1 nm, 0-27 nm, 0-56 nm) of each repeat, the Board notes that these tests have been carried in the same way as those of D8, so that it could be reasonably expected that the same range of experimental error in the determination of the final concentration has occurred, and that hence these tests also illustrate the extreme sensitivity of the determined pore volume to the measured final concentration.

2.24 The results of the pore volume determination in ion-exchanged water made by Appellant II are presented in the Tables of pages 5 to 7 of D8.

2.25 In that respect, the Board observes that for the determination of the pore volume of Sample C in the range 0-5.1 nm, five measurements of the final concentration Cf of dextran in the filtrate have been carried out, which give values of the measured concentration of 0.502, 0.496, 0.494, 0.500 and 0.506% respectively, and which allow to calculate the corresponding values of pore volume of respectively:

+23.90, -48.39, -72.87, 0.00, and +71.15 ml/g. Independently of the fact that negative and hence meaningless values of the pore volume would appear to be obtained, the Board further observes that a slight variation in the measured value of the Cf of 0.004% absolute i.e. 0.8% relative leads to a tripling of the measured pore volume (23.90 to 71.15 ml/g). The extreme sensitivity of the determined pore volume to the measured value of the final concentration Cf is further illustrated, in the Board's view, in these Tables, by the fact that a very slight variation of 0.001% absolute, i.e. 0.2% relative of the value of the measured Cf already induces a relative variation of 23% of the determined pore volume (cf. Sample C, PV (0-56); Repeats 3 and 4).

2.26 In this connection, the additional tests carried out by Appellant II on partially neutralized polyacrylic acid polymers prepared according to Sample 9 (Sample referred as W108601) and to Sample 10 (Sample referred as W108602) of Example 2 of D2 (cf. Annex 2, and Table 2 thereof submitted with the Statement of Grounds of Appeal of Appellant II), show that negative i.e. meaningless results in terms of V/V % (cf. Sample W108601 (Repeats 1 and 5) and Sample W108602 (Repeat 1) or drastically divergent results (cf Sample W108601 Repeats 3 and 4) are obtained.

2.27 The extreme sensitivity in both methods of the determined pore volume to the measured final concentration Cf would appear, in the Board's view, to be inherent to the method of calculating the pore volume starting from the final concentration Cf. As taught by the patent in suit, the pore volume in physiological salt solution for a specific pore diameter range (e.g. 0-5.1nm) is given by the formula:

PV(0-5.1nm)(ml/g) = (W2+W3)[1-{W3/(W2+W3)}x(Ci/Cf)]/W1.

This implies, when replacing Ci, W1, W2, W3 by their values (i.e. 1%, 0.01g; 30ml; 30ml) that:

PV (0-5.1) = 60[1-(30/60ml)x 1/Cf]/0.01, i.e.

PV (0-5.1) = 6000(1- 0.5/Cf) = 6000(Cf-0.5)/Cf.

It is hence clear that the slightest variation in the determination of the final concentration is amplified by a factor in the order of 6000, when calculating the corresponding pore volume in physiological salt solution. It is further evident that one would come to the same conclusion in view of the corresponding formula used for calculating the pore volume in ion-exchanged water (cf. paragraph 2.15 above).

2.28 This extreme sensitivity finds, in the Board's view, also its origin in the very little difference in final concentrations of dextran in the filtrate which occurs between the case of a 0% exclusion and a 100% exclusion of the dextran molecule from the gel pores when determining the pore volume. As shown by the Appellant II in its Statement of Grounds of Appeal and not contradicted by the Respondent, this difference is as low as 0.051% absolute for a superabsorbent polymer having an absorbency of 60g/g. In other words a variation of 1% relative of the value of the measured final concentration induces a variation of 0 to 100% of the measured value of the actual volume of the pores in a specific diameter range (e.g. from 0 to 5.1nm).

2.29 Thus, the Board, in the absence of counter evidence from the side of the Respondent, can only conclude that the tests carried by the Appellant II merely bring to the light the inherent extreme sensitivity of the determination of pore volumes by the methods referred in Claims 1 and 2 to the measured final concentration Cf. It thus follows that, despite conducting the measurement of the final concentration of the dextran in the filtrate with due care and good accuracy as done by the Appellant II, there is, as shown above (cf. paragraphs 2.22, 2.23, and 2.25 to 2.26), an extreme inaccuracy in the determination of the pore volumes according to the methods referred to in Claims 1 and 2.

2.30 This extreme inaccuracy in the determination of the pore volume in a specific pore diameter range hence drastically questions the reliability of this feature, and by way of consequence the reliability of the feature set out in Claim 1 that a water swellable crosslinked polymer must exhibit a total volume of pores in the diameter range of 5.1 to 27 nm of at least 60% of the total volume of pores as determined by the method referred in that claim, and the reliability of the feature set out in Claim 2 that crosslinked polymer must exhibit a total volume of pores in the diameter range of 5.1 to 27 nm of at least 80% of the total volume of pores as determined by the method referred in that claim.

2.31 Whilst a reasonable amount of experimental inaccuracy is permissible when it comes to sufficiency of disclosure, the level of uncertainty in the present case is, in the Board's view, such that there would have to have been available adequate instructions in the specification or on the basis of the general knowledge of the skilled person in order to reduce the level of uncertainty in the determination of the pore volume in a specific pore diameter interval, to a level which would not jeopardize the validity of the measured parameter for the solution of the technical problem.

2.32 Although the patent in suit gives absolutely no indication on the degree of error of the determinations of the pore volume in the specific ranges of pore sizes, it has, nevertheless, been submitted by the Respondent at the oral proceedings before the Board that the pore volumes can be determined with an accuracy of 1% or less by the methods disclosed in the patent in suit.

2.33 Independently of the facts, that no evidence has been submitted in that respect by the Respondent, and that such an accuracy would necessitate an extremely high accuracy of the determination of the final concentration of dextran in the filtrate in view of the amplifying effect of the factor 6000 between the variation of final concentration on the value of the pore volume calculated therefrom, the Board can however only state that the patent in suit does not contain any indication of further factors which might strongly increase the accuracy of the determination of the final concentration, and hence the reliability of the determination of the pore volume by the methods referred to in Claims 1 and 2.

2.34 In that respect, the Board does not accept the argument of the Respondent, that the patent in suit is directed to superabsorbent polymers having a high absorbency, i.e. in the Respondent's view, of more than 100 g/g, and that for these polymers the pore volume could be determined with a good accuracy.

2.35 This is because, while it might be true, as shown by document D17, that a higher absorbency of the polymer would increase the difference between the final concentration Cf corresponding to the 0% exclusion and the final concentration corresponding to the 100% exclusion, the Board can only state that neither Claim 1 nor Claim 2 contains a such limitation in terms of absorbency of the claimed polymer (i.e. at least 100 g/g), and that the description of the patent in suit is totally silent on such minimal level of absorbency of the claimed polymers.

2.36 The Board also does not accept the further argument of the Respondent that when determining the pore volume in ion-exchanged water the absorbency of the polymers is increased with respect to its absorbency in physiological salt solution, and that hence the method referred to in Claim 2 would allow a more reliable determination of the pore volume than the one referred to in Claim 1.

2.37 Even if it were accepted that the absorbency is greater in ion-exchanged water than in physiological salt solution although there is no such evidence on file, this is because the tests carried out by the Appellant II (cf. D8) clearly show that the sensitivity of the determination of the pore volume to the measurement of the final concentration Cf remains in any case extreme when the polymers are tested in ion-exchanged water e.g. a tripling of the determined pore volume in ion-exchanged water in the range 0-5.1 nm for Sample C for a 0.8% relative variation of the measured final concentration to be compared with a quadrupling of pore volume in physiological salt solution for the same Sample C in the same range of pore size for a 0.6% relative variation of the final concentration.

2.38 Nor could the lack of instructions in the patent in suit (cf. paragraph 2.33 above) be overcome by the general knowledge of the skilled person, since the pore volumes according to Claims 1 and 2 represent newly formulated parameters determined by new methods for which, hence, no common general knowledge was evidently available in the art before the priority date of the patent in suit.

2.39 Consequently, the patent in suit does not disclose the method for determining the specific pore volumes as referred to in Claims 1 and 2 in a manner which reliably retains the validity of these parameters for the solution of the technical problem, in the sense that the values routinely obtained would not be such that the claimed subject-matter of Claim 1 and the claimed subject-matter of Claim 2 cover polymer variants incapable of providing the relevant effect (i.e. high absorption capacity when put under an increased pressure).

2.40 For these reasons, the Board comes to the conclusion that the patent in suit does not comply with the requirements of Article 83 EPC.

2.41 This conclusion would not be altered by the argument of the Appellant that the requirement of sufficiency of disclosure must be regarded as met if the examples of the patent in suit could be reproduced.

2.41.1 In the present case, the actual technical contribution to the state of the art by the disclosure of the patent in suit essentially consists of providing methods for selecting water swellable crosslinked polymers having high absorption capacity when put under pressure.

2.41.2 As indicated in paragraph 2.3 above, the claimed polymers according to Claims 1 and 2 are only characterized by a specific pore volume as determined by the methods mentioned in these claims, but no further specific details are given in these claims in respect of the chemical structure or the level of absorbency of the claimed polymers.

2.41.3 Since, in order to carry out the invention, the skilled person must hence be able to distinguish between water swellable crosslinked polymers having these specific pore volumes and those not exhibiting these features, the fact that the methods for determining the pore volume of water swellable crosslinked polymers disclosed in the patent might give conclusive results in the case of the specific partially neutralized crosslinked polyacrylic acid polymers disclosed in Examples 1 to 5 for the method referred to in Claim 1, and in the Examples 1, 6 and 7 for the method referred in Claim 2, does not change the fact that these methods must also be reliably applicable to any water swellable crosslinked polymer in order to allow the skilled person to disregard variants incapable of providing the relevant technical effect.

2.42 This is, however, not the case here, since it has been convincingly shown by the Appellants that the methods for determining the pore volume referred to in Claims 1 and 2 of the patent in suit give totally unreliable results when applied to other water swellable crosslinked polymers, even very closely structurally related to those exemplified in Examples 1 to 7 of the patent in suit, i.e. further partially neutralized crosslinked polyacrylic acid polymers such as Favor 880, SVM 9543, and those prepared according to Samples 9 and 10 of Example 2 of document D2.

First and second auxiliary requests

3. Since Claim 1 of the first auxiliary request corresponds to Claim 2 of the main request, and since Claim 1 of the second auxiliary request is directed to an absorbent article comprising a water swellable crosslinked polymer, whose definition correspond to that of the water swellable crosslinked polymer according to Claim 2 of the main request, it thus follows that these requests do not meet the requirements of Article 83 EPC. They must hence be refused.

4. Since none of the requests presented by the Respondent can be allowed, the decision under appeal must be set aside and the patent be revoked.

ORDER

For these reasons it is decided that:

1. The decision under appeal is set aside.

2. The patent is revoked.