T 0376/91 (Laminate/AMERICAN CAN) 02-03-1994

Reasons for the Decision

1. The appeal is admissible.

The main request

2. The Board has no reason to question the findings of the Opposition Division concerning Article 123 EPC except the omission of the expression "for packaging" which was present in Claims 1 and 12 as granted.

2.1. It is conceivable that by omission of the said feature, certain laminates might be included which were excluded by the granted form of claim. There is, for example, no limitation on the thickness of the claimed laminates. Beyond a certain thickness, such laminates would clearly be unsuitable for use as a packaging film. In other words, deletion of the said feature would be likely to lead to an extension of the claimed subject-matter. The main request is accordingly refused for failure to comply with Article 123(3) EPC.

The auxiliary request

3. Inclusion of the expression "for retortable packaging" in Claims 1 and 11 of the auxiliary request first of all restores the limitation to films suitable for packaging. It is clear from the granted patent (e.g. page 3, lines 35 ff., page 6, lines 10 ff. as originally filed) that the laminates of the invention are intended for use in retorting processes. Inclusion of the word "retortable" in Claims 1 and 11 also amounts to a limitation of the subject-matter claimed since laminates incapable of withstanding the rigorous conditions of retorting would be excluded. It is also to be noted that inclusion of this limitation met the approval of the Appellant at the oral proceedings.

3.1. Accordingly, the Board is satisfied that, in this respect, Claims 1 and 11 of the auxiliary request satisfy the requirements of Article 123(2) and (3) EPC.

3.2. The Board is also convinced that the other objections raised by the Appellant under Article 123 EPC (see point V above) are met by the claims of the auxiliary request.

3.2.1. Limitation of the oxygen permeability to 0.35 mol per day per 645 cm2 of surface is supported by the value for KNO3 appearing in Table II on page 6, of the patent (page 12 as originally filed). Although based on a single value, it serves to limit the subject-matter to the more effective agents exemplified. It is not of significance for the purposes of Article 123(2) EPC that these agents were not stated to be preferred in the application as originally filed. The less effective drying agents mentioned in Table II become comparative examples by the amendment adding annotations on page 6 of the patent in suit before the Opposition Division. It is also a restriction in relation to the figure of 1.35. ml per day referred to in the granted claims.

3.2.2. Although the expression "water soluble water absorbing agent" may not be mentioned expressis verbis in the original document, there is ample support for such a limitation. It is apparent that the absorbing agents set out in Table I, each of which is water soluble, together with KNO3 mentioned in Table II, give significantly better oxygen permeability values than the water insoluble drying agents which also feature in Table II. The Decision T 151/84 dated 28 August 1987 (not published in OJ EPO) is not relevant to the present case as there the Board allowed deletion of a feature from the claims which was not regarded as an essential feature of the invention.

3.2.3. The Board is also satisfied that Claim 11 has adequate support in the originally filed specification. The original Claim 1 merely refers to "the incorporation of a drying agent in the structure" without any reference to its position. Only in Claim 2 is reference made to its position "in a layer proximate to the moisture sensitive layer". Correspondingly the description on the original page 2 refers generally to the presence of a drying agent (lines 11 to 13) and only later indicates (lines 14 to 17) its advantageous presence in the adhesive layers. There is thus support for its presence in any layer of the structure.

4. Clarity (Article 84 EPC)

In the written procedure, the Appellant raised an objection of lack of clarity insofar as the claims failed to specify how the oxygen permeability values were measured after retorting. During the opposition procedure, the Respondent indicated that these were measured in accordance with a modification of ASTM D1434 at a temperature of 22.8 C (73 F) (letter received on 7. September 1989). The Board sees no reason to differ from the opinion of the Opposition Division that the requirements of Article 84 EPC are satisfied.

5. Sufficiency of disclosure (Article 83 EPC)

5.1. The Appellant has argued that the patent in suit does not give adequate instruction as to how a drying agent might be incorporated in the barrier layer. In the description on page 4 (lines 15 to 18) instructions are given for incorporating a drying agent in an adhesive layer. According to Table I the thickness of the adhesive layer varies in the range 0.058 to 0.076 mm whilst that of the EVOH layer varies between 0.043 and 0.048. mm. The Board is convinced that the skilled person with a rudimentary knowledge of plastics processing would be able to adapt the method to include the drying agent in the EVOH layer. Although document (10), an American continuation-in-part of the application forming the priority of the patent in suit, was published after the priority date, it does demonstrate that a drying agent can be incorporated in an EVOH barrier layer (see Claim 1 and description column 6, lines 62 ff.). The disclosure of (10) could also be regarded as late-filed experiments which show that, when the drying agent is incorporated in the EVOH layer, oxygen permeability values appreciably less than 0.35. can be attained (cf. column 7, lines 13 to 28).

5.2. In respect of Article 83 EPC, the Appellant has failed to show that any area falling within the ambit of the claims cannot be carried out. The Appellant has limited his attack to the claims. According to the jurisprudence of the Boards (e.g. T 14/83, OJ EPO 1984, 105), the disclosure of an invention should be considered by interpreting the claims in conjunction with the description. As indicated, the Board considers that the description contains sufficient information to enable one skilled in the art to carry it out.

6. Novelty (Article 54 EPC)

None of the documents cited during the proceedings discloses laminates fulfilling all the features of Claims 1 and 11 of the patent in suit. Since novelty is no longer in dispute, it is not necessary to provide further reasoning.

7. Problem and solution

7.1. In the opinion of the Board the closest prior art is document (8) which is also concerned with multilayer laminates useful in the packaging of food and drink (e.g. column 9, lines 29 to 66; column 14, lines 17 to 57). These include five layer structures similar to those illustrated in Figure 2 of the patent in suit. Structures described in Examples 1 and 2 of (8) have polyolefin outer layers (e.g. polypropylene or ethylene- propylene random copolymer), intermediate adhesive layers of unsaturated carboxylic acid-modified polypropylene and, as the innermost oxygen barrier layer, EVOH.

7.2. In relation to (8), the problem to be solved is to develop a laminate for use in retortable packaging which retains its oxygen barrier properties after exposure to moisture at elevated temperature.

7.3. The problem is solved by including a water soluble drying agent in a layer of the structure in accordance with Claims 1 and 11 of the patent in suit. Having regard to the experimental results which appear in Tables I and II of the patent in suit, the Board is satisfied that the problem has been solved in a plausible manner.

8. Inventive step (Article 56 EPC)

8.1. Two facts concerning laminates of the type described in document (8) and the patent in suit were well known at the priority date. It had long been known, e.g. from reference (4) which was published in 1946, that the water vapour permeability of polyolefin films increased considerably with increasing temperature (cf. point V above). It was also well known, as acknowledged in the opening paragraphs of the patent in suit, that EVOH polymers are moisture sensitive, i.e. that they lose their ability to act as oxygen barriers. These facts were not disputed by the parties at the oral proceedings. As indicated above, the patent in suit solves the problem of the sensitivity of the EVOH layer to moisture which passes through the polyolefin outer layers at elevated temperatures.

8.2. The essential difference between the five-layer laminate of document (8) and that of the patent in suit is that, in the case of the latter, a water soluble drying agent is present within the laminates, preferably in each of the adhesive layers.

The disclosure of (8) is much concerned with the problems of extruding such multilayer laminates and the fabrication of containers therefrom. There is not the slightest hint in (8) of the problem underlying the patent in suit nor of its solution.

8.3. The Appellant has argued that document (5) points to the solution chosen in the patent in suit. The Board cannot accept this argument. Document (5) relates to mouldable resin compositions useful in making storage vessels for moisture sensitive materials. In the past, small sieve- like containers, e.g. of silica gel or CaCl2, were placed in such storage vessels to absorb moisture. According to (5), the drying agent is incorporated into the plastics material used to fabricate the storage vessel. As the walls of the resultant vessel contain particles of drying agent, it is unnecessary to employ a separate container of drying agent. This is an entirely different problem to that underlying the patent in suit.

8.4. Document (12) also relates to a multi-layer laminate for use in flexible packaging material which may consist of five layers. The inner layer is polyvinyl alcohol (PVOH) which acts as an oxygen barrier providing it is maintained in a substantially anhydrous state (page 1, lines 22 to 26). The said PVOH layer is laminated to two outer layers having low permeability to moisture (e.g. polyvinylidene chloride or a polyolefin; page 1, lines 61 to 93) by means of a polyurethane primer. According to (12), the polyurethane acts not only as a primer or adhesive to bond the PVOH to the outer layers but also to remove "the small amounts of water" contained in the PVOH (page 2, lines 49 to 53). It also states on page 2, lines 64 to 67 that it is important that once the barrier layer has been rendered anhydrous, it should be prevented from absorbing moisture.

8.4.1. The Appellant has argued that this is a similar problem to that encountered in the patent in suit and that the polyurethane acts not only as an adhesive but also as a drying agent within the meaning of the patent in suit. It is, however, to be noted that the polyurethane is stated to absorb merely the small amounts of water contained in the PVOH. The resultant PVOH is protected from further exposure to moisture only by the outer layer forming a moisture proof barrier (cf. page 2, lines 99 to 108). The laminate described in Example 1 is tested "at ambient conditions" (page 3, lines 86 to 92). There is no hint that such a laminate might retain its oxygen barrier properties under the rigorous conditions encountered during retorting.

8.5. The Respondent filed a report of Dr. Mitsutani, Monthly Report No. 53 dated November 1983, stating that such reports, available on subscription, circulated widely in the packaging industry. Even more than two years after the priority date of the patent in suit, Dr. Mitsutani was suggesting other solutions to solve the moisture sensitivity problem of EVOH polymer films. These included biaxial orientation of the EVOH film and surface treatment thereof (e.g. acetylation) to render the film more hydrophobic. Another solution proposed by Northern Petroleum Co. involved drying a multilayer structure which included an EVOH layer in an oven after retorting. A more radical possibility might be to replace the EVOH with another oxygen barrier film.

8.6. Whilst it might seem prima facie obvious to solve a problem involving moisture by employing a drying agent, it is clear from the preceding that a variety of alternative solutions to the problem underlying the patent in suit were also available. Since the prior art gives no hint of the solution proposed by the Respondent, an inventive step in respect of Claims 1 and 11. of the auxiliary request must be recognised. The remaining claims derive their patentability therefrom.