T 0543/05 13-11-2007

1. The appeal is admissible.

MAIN REQUEST

2. Amendments (Articles 100(b) and 123(2) EPC)

2.1 The only objection raised by Appellant I with regard to this issue is the introduction of the term "non-expanded" in the definition of the polytetrafluoroethylene (PTFE) films used for the preparation of the claimed chemical barrier laminates into granted Claim 1 and into Claim 7 as amended before the Opposition Division (cf. "axially oriented unsintered non-expanded polytetrafluoroethylene films" [emphasis added]).

2.2 The question to be decided is whether the addition of the word "non-expanded", which is accepted not to have been explicitly disclosed in the application as originally filed, is directly and unambiguously derivable from the application as originally filed.

2.3 The content of the application as originally filed can be summarised as follows:

2.3.1 The claimed invention aims "to provide a novel and improved PTFE laminate having high tensile and tear strengths, flexibility, and excellent chemical resistance and barrier properties" (see page 2, lines 7 - 9 of the application as originally filed). The laminates are "constructed of oriented PTFE films" (page 2, lines 16 - 17. The starting films may be unsintered or sintered (see page 4, lines 3 - 5) but the preferred PTFE films are "unsintered prior to lamination, and are uniaxially oriented, typically as a result of their having been extruded or calendered during production" (page 2, lines 17 - 19). The films are said to be "sintered during lamination, but retain their orientation" (page 2, lines 19 - 20).

2.3.2 The lamination is carried out by heating the films to a temperature between 349 and 404ºC (660 and 760ºF), at a pressure of at least 7 x 10**(3) Pa (1 p.s.i.) for a period of time between 20 and 70 seconds (see Claims 9 - 11).

2.3.3 In the preferred embodiments according to the examples unsintered PTFE films are laminated at 382ºC (720ºF) and 276 x 10**(3) Pa (40 p.s.i.) for a period of 70 seconds. The films are sintered during lamination and retain their respective direction of orientation (see page 4, lines 21 - 23).

2.4 The crucial issue for the assessment of the admissibility under Article 123(2) EPC of the claimed subject-matter is whether it is evident beyond any doubt to the skilled person reading the original description that the PTFE films used were "non-expanded" films.

2.5 In the Board's judgement, this is indeed the case for the following reasons:

2.5.1 Taking account that the objective of the patent is to produce a laminate having excellent barrier properties, it would be clear to the skilled person reading the application as originally filed that, in order to achieve such barrier properties, porous films would not be suitable. The skilled person would consider that expanded PTFE films should be avoided because they are porous (see for instance, D9, page 2, lines 3 - 5 where it is stated that expanded PTFE cannot be used as a barrier layer to chemicals since it can rapidly absorb through its pores liquids that have a low surface tension).

2.5.2 Moreover, the films used as starting materials are qualified in the application as originally filed as unsintered prior to lamination, and uniaxially oriented, "typically as a result of their having been extruded or calendered during production". It is undisputed that these manufacturing methods result in non-expanded films. The films manufactured in this way are then laminated and the specification is completely silent about any expansion process to be carried out before lamination. The skilled reader would undoubtedly understand that films obtained after extrusion or calendering, that is to say, non-expanded films, have been used.

Further, the lamination conditions disclosed in the application as filed are comparatively gentle. The skilled person would be aware of the fact that under these mild conditions it would not be possible to produce a barrier product using as starting material an expanded (porous) material, because air would remain entrapped within and between the films. This is confirmed by the severe laminating conditions of the expanded films used in D9, which discloses temperatures of from 330 - 390ºC, pressures of from 1.0 x 10**(6) - 2.4 x 10**(6) Pa (150 - 350 p.s.i.) and times of from 15 minutes to 4 hours.

2.5.3 Finally, there is nothing in the application as originally filed which would suggest that expanded films could be used. The fact that in the application as originally filed both unsintered and sintered films could be used as starting material and in the granted version only unsintered films were used does not invalidate the above interpretation. The possible use of sintered films, originally envisaged by the present inventors as a less preferred alternative, does not entail that these must have been expanded, because the properties sintered/unsintered are unrelated to and independent from the properties expanded/non-expanded. The skilled person would be aware that extruded and/or calendared PTFE films, which by these processes become axially oriented, are unsintered and non-expanded, unless subjected to further treatment not suggested in application as filed; expansion of the films occurs by stretching under certain conditions (cf. D3, column 2, line 7 to column 3, line 17), resulting in expanded, unsintered films, which thereafter may be heated above the PTFE's crystalline melting point leading to "amorphous locking", i.e. sintering of the stretched, expanded film (D3, column 3, lines 49 to 65).

2.5.4 In summary, the teaching that the PTFE films used as starting material are "non-expanded" is a teaching that can be directly and unambiguously derived by the skilled person from the application as originally filed.

2.6 The Opposition Division pointed out that in its broadest possible meaning the term "PTFE film" covered both non-expanded and expanded films. Appellant I further noted that the term "non-expanded" relates to a specific characteristic of the "PTFE films" and the fact that this characteristic was not defined implied that both possibilities were embraced by the original disclosure. In any case, in its opinion the amendment amounted to an exclusion of the "expanded" films and should be regarded as a disclaimer. This "disclaimer" did not fulfil the criteria for assessing the allowability of a disclaimer as set out in the decisions G 1/03 (OJ EPO 2004, 413) and G 2/03 (OJ EPO 2004, 448).

2.7 These arguments cannot be accepted by the Board.

2.7.1 The assertion of the Opposition Division that the term "PTFE film" embraces both expanded and non-expanded films is only correct when the term is read in isolation. As already explained above (see 2.5), in the context of the application as originally filed the only meaningful interpretation of the term "PTFE film" is that it relates exclusively to non-expanded PTFE films. Any different interpretation makes no sense in the light of the application as originally filed and would be dismissed by the skilled person.

2.7.2 It is also noted that this interpretation by the Board is fully consistent with the use of the terms "unexpanded" (equivalent to "non-expanded") and "expanded" in the prior art documents in the proceedings.

Therein a PTFE film is characterized as "expanded PTFE film" (sometimes referred as ePTFE film) when it has been subjected to an expansion process (see for instance D9, page 1, line 29 - page 2, line 9). The absence of the qualification "expanded" implies that the film has not been subjected to such an expansion process and consequently there is no need to specifically highlight the absence of this special-treatment-derived feature (see also paragraph (a) of the first statement of Mr. DiClemente).

A PTFE film is characterized in the prior art as "unexpanded" only when this is necessary for the purpose of comparison with an "expanded" film (cf. D3, Tables 4, 6, 8, 10, etc.; see also D9, paragraph bridging pages 1 and 2). If such comparison is not an issue the "unexpanded" film is referred to merely as "the unsintered film" (see D3, example 3, column 8, line 60, and compare with column 10, lines 25 - 26 or example 6, column 12, line 62 and column 13, line 25 and compare with Table 6).

2.7.3 Thus the introduction of the word "non-expanded" into Claims 1 and 7 merely made explicit what was already implicit in the application as originally filed, namely that the films to be used as starting materials are "non-expanded PTFE films".

This amendment does not therefore mean that specific embodiments covered by the original disclosure are now excluded (or "disclaimed"). Consequently, it does not amount to a disclaimer and the criteria for allowability of disclaimers are not relevant.

2.8 For these reasons the Board is satisfied that the amendments made to Claims 1 and 7 do not introduce subject-matter which goes beyond the content of the application as originally filed.

3. Novelty (Article 54 EPC)

3.1 The novelty of Claim 1 was contested by Appellant I having regard to the disclosure of D9 and the novelty of Claim 7 was contested having regard to the disclosure of example 9 of D3.

3.2 Claim 1 is directed to a flexible fluoroplastic chemical barrier laminate comprising a plurality of axially oriented sintered PTFE films, the laminate being obtainable by laminating a plurality of axially oriented unsintered non-expanded PTFE films.

3.2.1 Document D9 discloses a densified previously expanded PFTE article and a process for its production (see abstract). The process consists of the bonding and simultaneous densification of a plurality of sheets or tapes comprised of expanded polytetrafluoroethylene (ePTFE) as obtained in D3 (see D9, page 5, lines 2 - 6). The process is carried out under conditions which retain the node and fibril structure of the original ePTFE (see page 5, lines 11 - 13).

3.2.2 The barrier laminates according to Claim 1 of the patent in suit are on the contrary made from unsintered non-expanded PTFE films under mild lamination conditions. As a consequence, the final laminate does not exhibit any characteristics (voids, node and fibril structure) resulting from and typical for an expansion process (see D9 and also D3, Fig. 1 and column 6, lines 25 - 43).

3.2.3 The claimed laminates are therefore clearly distinguished from the products of D9.

3.3 Claim 7 is directed to a method of producing a flexible fluoroplastic chemical barrier laminate by stacking a plurality of axially oriented unsintered non-expanded polytetrafluoroethylene films and confining the films between heated platens to expel entrapped air.

3.3.1 This process is clearly distinguishable from the process of example 9 of D3 which uses an expanded film for the preparation of the laminate and does not use heated platens to expel entrapped air during the preparation of laminate, the expanded, amorphously locked laminate being made by clamping to a rigid frame two layers of expanded film and heating at 370ºC for 7 minutes.

3.4 For these reasons the subject-matter of the claims is novel.

4. Inventive step (Article 56 EPC)

4.1 Closest prior art

4.1.1 The Board considers in agreement with both Appellants that the closest prior art is represented by document D9, since it also addresses the production of PTFE articles having barrier properties.

4.1.2 As already discussed above under 3.2.1, D9 discloses a multilayer material constituted by densified expanded PTFE sheets and a process for its preparation (see also Claims 1 and 3). D9 acknowledges in its introduction (see pages 1 and 2 under "Background of the invention") that films of low porosity PTFE exhibit poor mechanical properties such as poor strength and flexibility, which limit their use. D9 further acknowledges that expanded porous polytetrafluoroethylene as produced by the process of D3 and having a microstructure characterised by nodes interconnected by very small fibrils shows higher strength but, owing to its porous structure, cannot be used as a barrier layer.

4.1.3 D9 aims to alleviate this prior art drawbacks by a process wherein two or more layers of expanded porous PTFE are placed inside a heat and pressure stable flexible container, gas is evacuated from the container, which is then subjected to a high pressure between 1.0 x 10**(6) - 2.4 x 10**(6) Pa (150 - 350 p.s.i.) and a temperature of at least 368ºC to obtain a densified expanded PTFE (see Claim 3). The thus obtained products are useful as a barrier to harsh chemicals (cf. page 2, lines 5 - 9).

4.1.4 The barrier laminates of Claim 1 of the patent in suit differ from the disclosure of D9 essentially by the use of axially oriented unsintered non-expanded PTFE films as starting films and by the use of milder conditions for the preparation of the laminate.

4.2 Problem to be solved

4.2.1 The patent in suit does not attribute any specific effect to these distinguishing features. According to paragraphs [0034] - [0037] the laminates of the invention exhibit improved tensile and tear strengths in all directions when compared with laminates made of non-oriented films. However, a direct comparison with the products of D9 cannot be made with the data in the patent and these advantages can therefore not be taken into account when formulating the problem to be solved.

4.2.2 Thus, in the absence of any established advantage over the disclosure of D9, the objective technical problem to be solved by the patent in relation to said prior art can thus be formulated as being the provision of alternative PTFE laminates having high tensile and tear strengths and good chemical resistance and barrier properties (see also [0005]).

4.3 Solution to the problem

4.3.1 The solution to this problem is provided by the claimed laminates prepared by laminating a plurality of axially oriented unsintered non-expanded PTFE films, with at least one of said films having its direction of orientation disposed angularly with respect to at least one other adjacent film.

4.3.2 The examples in the patent in suit show that the above mentioned problem has been credibly solved. The laminates thus obtained are tear resistant and flexible and are able to provide resistance against chemical attack. This was not challenged by Appellant I.

4.4 Inventive step

4.4.1 It remains to be decided whether, in view of the available prior art documents, it would have been obvious for the skilled person to solve this technical problem by the means claimed, namely by laminating a plurality of differently axially oriented unsintered non-expanded PTFE films.

4.4.2 Document D9 does not give any hint to this solution. On the contrary, as stated above, non-expanded PTFE films are discarded as starting materials in D9 due to their poor mechanical properties (see page 1, lines 21 - 22).

Document D3 also gives no hint to this solution. D3 discloses a process for the production of a porous article which comprises expanding a highly crystalline PTFE made by extrusion technique by stretching it (see Claim 1). The only laminate exemplified in D3 is made of two layers of expanded films and results in an expanded, amorphous locked laminate which does not show barrier properties (see example 9).

The Board also disagrees with the argument of Appellant I that the skilled person would deduce from the reference to the low filtering rates of unexpanded unsintered single films mentioned in example 10 of D3 that they could be used for preparing laminates having good barrier properties. There is no compelling logic behind this argument because the information that the unexpanded, unsintered films were unsuccessful as semi-permeable membranes offers no information about their possible use for the preparation of laminates having a different property, namely functioning as a chemical barrier material.

4.4.3 Thus, the finding that laminates having excellent chemical barrier properties could be prepared from axially oriented unsintered films under mild conditions is not a teaching the skilled person, being confronted with the task to provide a solution to the existing technical problem, would find in the available prior art.

4.5 Hence, the Board considers that, in the light of the cited prior art, it would not have been obvious to a person skilled in the art to arrive at the laminates claimed in Claims 1 to 6 or at the process of their preparation as claimed in Claims 7 to 16. The subject-matter of the claims therefore involves an inventive step within the meaning of Article 56 EPC.

5. In summary, the Board concludes that the grounds of opposition raised by the Appellant I do not prejudice the maintenance of the patent as amended.