T 0085/96 26-08-1999

Admissibility of the appeal

1. The appeal is admissible.

Procedural matters

2. One day before the oral proceedings to be held before the Board, the Appellant filed DN, which had until then not been mentioned in any way and hence is a completely new document in the case. In view of the late filing the Respondent had had no opportunity to study the document and to give its comments. In these circumstances, the Board considered that the criteria as laid down in decisions G 9/91 and 10/91 (OJ EPO 1993, 408 resp. 420) should be applied, that is, the document must be prima facie highly relevant in the sense that it is highly likely to prejudice the maintenance of the patent. Since DN contained no specific and direct disclosure of the dew point and was completely silent regarding the residual monomer content, the Board found that the subject-matter claimed by the patent in suit was not clearly and unambiguously disclosed in DN, so that DN prima facie could not be estimated to prejudice the novelty under Article 54(3) EPC of the claimed subject-matter. Therefore, DN was not admitted into the proceedings and a final decision could be announced at the end of the oral proceedings.

Wording of the claims

3. The only amendment to the claims during the opposition proceedings consisted in the incorporation into Claim 1 of the subject-matter of Claim 4 as originally filed and granted. Such a modification obviously complies with the requirements of Article 123(2) and (3) EPC and was not objected to by the Appellant.

3.1. However, in the framework of its objections under Articles 83 and 54 EPC, the Appellant raised an objection against the scope of the claims. This amounted to an implicit objection under Article 84 EPC, which is not a ground for opposition. The objection was based upon the fact that, on the one hand, the only requirement regarding the polymer was not its composition or structure or the way it was prepared, but solely its hydrophilicity, and, on the other hand, the reduction of the residual monomer content was not always achieved by carrying out the method as defined by the other features of the claim, that is, the temperature and dew point of the drying gas.

3.2. As explained by the Respondent during the oral proceedings, the method of Claim 1 was defined not only by the presence of a hydrated hydrophilic gel polymer and specific process parameters, e.g. temperature and dew point of the drying gas, but also by the requirement that residual monomer content should be small. The latter feature, which corresponded to a characterization of the claimed subject-matter by the result to be achieved, was thus a functional definition of the method, which ensured that the residual monomer content of the hydrophilic polymer after treatment was substantially lower than before treatment. As further argued by the Respondent, such characterization was necessary in view of the fact that (i) the desired effect was unpredictable, (ii) it concerned in practice a relatively small amount of polymers and (iii) consequently, there was no other way to ensure an appropriate protection of the invention (T 292/85, OJ EPO 1989, 275).

3.3. This argument has been accepted by the Board. It follows that the scope of protection is to be interpreted as limited to the cases where a combination of compositional features (hydrophilic groups) and process features (drying conditions, temperature and dew point of the drying gas) within the terms of Claim 1 leads effectively to a substantial reduction of the residual monomer content as compared to conditions which fall outside the required features. It also follows that the substantive issues raised by the Appellant will have to be appraised in the light of that interpretation.

Sufficiency of disclosure

4. The Appellant based its insufficiency objection mainly on the argument that in many cases the process features of Claim 1 would not lead to the desired monomer reduction and that the patent in suit contained no guidance in which cases the claimed method would work.

4.1. The patent in suit contains twenty examples which describe the treatment of different polymers at several temperatures, dew points and compositions of the drying gas, i.e. a great number of variations within the scope of Claim 1. Also, there are fifteen control examples which illustrate the influence of single parameters falling outside the claimed subject-matter. The Appellant has not argued, nor shown, that any of the examples would not be repeatable, so that the Board is satisfied that a skilled person would in fact be able to reproduce the examples and to apply the method there described.

4.2. Regarding the more general definition of the working conditions of the claimed method, the requirement that the residual monomer content should be small, as interpreted above (point 3.3), means a limitation to the extent that only systems in which the residual monomer content is actually reduced are covered by the claimed subject-matter. Therefore, for the patent in suit to comply with Article 83 EPC, the skilled person should be able to verify, without undue burden or inventive activity, whether or not the method would work under any other conditions than those specified in the examples. The Board is satisfied that such is the case. One could, for instance, measure the residual monomer content of a polymer gel dried at a certain temperature and/or dew point outside the specified ranges, and then, after changing the conditions so as comply with the requirements as claimed, determine if the monomer content was actually reduced. Such a procedure would not take very long, so that the skilled person would, within a reasonable time and guided by the examples, from which the effect of changing the dew point and/or temperature of the drying gas can be seen, always be able to establish the effectiveness of the method. It is therefore concluded that the skilled person, guided by the information contained in the patent specification, by means of systematic trial and error experiments, would be able to produce a hydrophilic polymer with a small residual monomer content.

Novelty

5. The novelty objection was solely based upon D1.

5.1. This citation describes a method for producing a cross-linked polymer, which comprises continuously feeding an aqueous solution of a monomer and polymerizing into a water-containing cross-linked gel polymer with a polymerization initiator in a vessel provided with parallel rotary stirrer shafts fitted with blades, finely dividing the gel polymer produced by the shearing force of the stirrer blades during the polymerization, and continuously discharging the resultant finely divided gel polymer from the vessel (Claim 1). In Example 1 the polymer gel is then spread on a wire gauze and dried in a hot air drier at 150 C. In Example 2 the polymer is dried with a blast of hot air at 160 C in a continuous through-circulation band drier. In the third example (named Example 4), the polymer is again spread on a wire gauze and dried with a blast of hot air at 180 C for one hour. Neither dew points nor monomer residue contents are mentioned.

5.2. The Appellant's argument, supported by the declarations of four technical experts, was that, when drying the polymer as described in Example 2, the dew point would automatically reach a value within the range now specified. However, that allegation is based upon a number of assumptions regarding the other conditions used in that example, so that its value is doubtful. In fact, the Appellant conceded that dew points as now specified in Claim 1 would not occur inevitably. Moreover, the Appellant made no attempt to repeat Example 2 of D1 in order to measure the dew point actually reached during the drying operation, in which case also the residual monomer content could have been determined. Since the possibility that the dew point falls outside the required range is definitely present and there is no evidence that the dew point in Example 2 of D1 actually does fall within it, the range for the dew point of the drying gas as specified in Claim 1 cannot be regarded as clearly and unambiguously disclosed in D1.

5.3. Furthermore, even if this were the case, there is no indication at all that the residual monomer content in Example 2 of D1 was in fact reduced. On the contrary, the experimental report which the Appellant filed during the proceedings before the first instance (20 November 1993) shows that under conditions of temperature and dew point of the drying gas in accordance with the patent in suit, no residual monomer reduction in fact occurred. Therefore, there is no reason to assume that the drying method of Example 2 of D1 would not only implicitly disclose the dew point of the drying gas, but also meet the third requirement of the claimed-subject matter: a reduced residual monomer content.

5.4. Consequently, D1 does not disclose all the features now claimed, be it explicitly or implicitly, and hence cannot be regarded as detrimental to novelty.

5.5. As for the other documents on file, the Appellant did not base any novelty objection on them and the Board concurs with the Opposition Division that they are not detrimental to novelty.

Inventive step

6. The patent in suit concerns a hydrophilic polymer and method for production.

6.1. The treatment of hydrophilic polymer is disclosed in D1 as well as D8.

6.1.1. As mentioned above (point 5), D1 relates to a method of producing crosslinked polymers. It aims at solving the problems associated with polymerizing aqueous solutions as water-in-oil emulsions or suspensions in a hydrophobic solvent, which require the use of large volumes of organic solvents, and with cast polymerizing aqueous monomer solutions, which involves the continual removal of heat of reaction; furthermore, the drying of the polymers produced by those methods entails finely dividing the polymer, thus causing huge energy consumption (page 1, lines 7 to 18). The solution taught in D1 consists in polymerizing an aqueous solution of the monomer into a water-soluble polymer gel, finely dividing the latter and continuously discharging it from the vessel (page 1, lines 22 to 27). The general teaching of D1 does not go beyond the production of finely divided polymer gel followed by a drying step described in general terms. In particular, there is no mention of the residual monomer content, let alone any teaching directed to a control or a reduction of that parameter.

6.1.2. D8, however, concerns a method for the reduction of the amount of water insolubles and free monomer in an aqueous acrylamide polymer gel charge containing at least about 25% polymer and having a molecular weight of at least about 4 million which comprises heating said polymer gel, in the substantial absence of a sulfite compound, at a temperature ranging from about 80. C to 150 C for at least about 30 minutes while simultaneously maintaining the water content of the gel undergoing heating at substantially the concentration of that of said charge and recovering the resultant polymer gel (Claim 1). After the gel has been heated, it is dried according to any known procedure (column 3, lines 37 to 38).

6.1.3. From the above it is clear that the methods of both D1 and D8 have many features in common with the present process, but that only D8 addresses the same problem as the patent in suit, that is, reduction of the residual monomer content. Therefore, the Board, like the Opposition Division but contrary to the parties' points of view, considers D8 to be the closest prior art document (see also decision T 606/89 dated 18 September 1990, not published in OJ EPO).

6.2. Although the method according to D8 is said to result in low residual monomer, it involves an additional intermediate process step during a period of time which may extend over several hours (column 2, lines 52 to 57), that is, heating the polymer before drying, thus making the process rather cumbersome. In view of this, the technical problem underlying the patent in suit, along the lines of the introductory statement in the patent specification (page 2, lines 48 to 50), may thus be seen in providing a simplified method for the production of a hydrophilic polymer having a small residual monomer content.

6.3. According to the patent in suit this problem is to be solved by carrying out the drying step with a gas containing steam and having a specific dew point range at a given temperature range, as specified in Claim 1.

6.4. The examples and comparisons with the prior art in the patent specification (Tables 1 to 11) demonstrate that the above-defined problem has been effectively solved. In particular, it has been shown that hydrophilic polymers have been prepared and dried under such conditions as to result in a substantially reduced residual monomer content.

7. The issue to be decided, therefore, is whether the claimed subject-matter is obvious having regard to the documents on file.

7.1. The general teaching of D8 is that the polymer gel, after polymerization, should not be dried, but should first be subjected to a heating step during which the water content of the polymer gel is kept substantially constant. If any drying of the polymer gel would occur, insoluble material would be formed, which is considered undesirable (column 2, lines 58 to 66). Neither the means of maintaining the water concentration of the gel substantially uniform (column 2, lines 66 to column 3, line 16), nor the procedure followed to carry out the final drying step (column 3, lines 37 to 39) are described as essential for a successful recovery of a dry polymer, provided that the above-indicated sequence of operations is followed. The skilled person faced with the technical problem as defined above (point 6.2) hence had no reason to depart from the specific teaching of D8, in particular no incentive to consider a selection along the lines of the claimed method, which is based on a drying step without a preliminary heating step. A further point to consider, which follows from the absence of any information concerning the drying step in D8, is that this citation does not regard the features thereof as critical for the achievement of a lower residual monomer content. For both reasons, D8 alone does not render obvious the definition of the method now being claimed.

7.2. In its Notice of Opposition, the Appellant combined the teaching of D8 with that of D1, arguing that it would have been immediately evident to the skilled person that operating a recirculating band drier as in Example 2 of D1, under conditions which would almost invariably give rise to high humidity, would be likely to give reduction of the residual monomer content. The Board cannot follow that assertion for the following reasons.

First, there is no reason for the skilled person to combine the method described in D8 with the specific drier used in Example 2 of D1. After all, D1 discloses two more examples in which a different type of drier is used and the skilled person might as well have chosen one of those driers. Secondly, D1 is silent about the humidity of the drying gas. As pointed out above (point 5), the allegation of high humidity is based upon a number of assumptions for which no basis in D1 can be found, so that the humidity of the drying gas cannot be regarded as implicitly disclosed. Thirdly, D1 is completely silent about the residual monomer content and the skilled person would not have learned anything in that respect from D1 so as to modify the process described in D8 in accordance with the method now claimed.

7.2.1. During the oral proceedings the Appellant also referred to D2 and D3 in combination with D8.

In D3 the concept of the "critical relative humidity" (CRH) of a coating is developed, which concerns the evaporation behaviour of aqueous solutions containing cosolvents (page 48, Summary). D2 concerns the evaporation behaviour of organic cosolvents in water-borne formulations (page 65, right-hand column, paragraph "Critical Relative Humidity"). Both documents define the CRH as the relative humidity necessary to allow the drying to occur so that the concentration of organic cosolvent in water remains unchanged during the drying process. When the air is drier than the CRH, water flashes off faster than the organic cosolvent, leaving a cosolvent-enriched "tail". Conversely, if the drying air is wetter than the CRH, the cosolvent flashes off in preference to water.

Hence both D2 and D3 pertain to the removal of solvents, which are usually present in amounts of the order of magnitude of the polymer, thus normally expressed in percentages. By contrast, the patent in suit relates to the removal of residual monomer, the amount of which is indicated by parts per million in relation to the polymer. It is therefore clear that the general teachings of D2 and D3 relate to a concept which is so remote from the problem solved by the patent in suit that the skilled person would not have considered the combination thereof with the method known from D8. Apart from that, the Appellant has failed to demonstrate any relationship between, on the one hand, the temperature and dew point ranges as required in Claim 1 and, on the other hand, the CRH, so that it is not evident that, even if D2 or D3 were combined with D8, such a combination would have resulted in the claimed subject-matter.

7.2.2. Therefore, even if the skilled person would indeed have been encouraged to depart from the method of D8, there was no incentive whatsoever either in D1, D2 or D3 or any of the other documents on file, to modify it in such a way as to arrive at the present process.

7.3. In addition to the above line of argument the Appellant also relied on D1 as the basis of its objection of lack of inventive step.

7.3.1. Starting from D1, the Appellant argued that in the present case the problem-solution approach should not be applied since the problem was an artificial one, the true problem being the drying of the polymer. In that respect, the claimed subject-matter was prima facie obvious since the skilled person would naturally use the drier mentioned in Example 2 of D1 and, in applying economically optimal drying conditions, would automatically operate under the conditions now being claimed. It was a one-way-street situation (T 192/82, OJ EPO 1984, 415), which remained obvious even if there was an unexpected effect. Also, arguing in parallel to decision T 188/83 (OJ EPO 1984, 555), where it was stated that novelty could not be established solely by a reference made to an advantage which had until then not been recognised, inventiveness could not be established by an unexpected advantage.

7.3.2. The Board cannot follow the Appellant's arguments for the following reasons:

(i) In view of the feature of substantial reduction of the residual monomer content, which, as a functional feature, is an essential aspect of Claim 1 (see point 5 above), there is no reason to ignore that feature and to assume it would be an artificial factor. All the more so, since in view of D8 it can be concluded that it is in fact an existing problem in industry.

(ii) The Appellant maintained that operating within the ranges required in Claim 1, when applying the drier used in Example 2 of D1, was inevitable for the skilled person. That assertion was supported by declarations of four technical experts, which concerned the circumstances in which the continuous band drier of Example 2 of D1 was employed. However, all four opinions started from the use of such a drier as a matter of course, without considering the possibility of using another type of drier, such as e.g. described in Examples 1 and 4 of D1. Therefore, not only is the use of a certain type of drier one of several alternative possibilities, but the conditions under which the drier is employed are, as pointed out above (point 5), also open to variation. Therefore, the Board cannot see a one-way-street situation in the present case and it considers the argument of prima facie obviousness as unsupported by the facts and, accordingly, the references to the decisions T 192/82 (supra) and 188/83 (supra) as inappropriate.

7.4. For the reasons given above, the Board concludes that the subject-matter of present Claim 1 cannot be derived from the documents relied upon by the Appellant, whether taken alone or in combination, and, therefore, involves an inventive step.

8. As Claim 1 is allowable and Claims 2 to 11 relate to further embodiments of the method according to Claim 1, their patentability is supported by that of Claim 1.

9. Since the Respondent's main request can be granted, its auxiliary requests need not be considered.