T 0293/92 24-08-1995

1. The appeal is admissible.

Procedural matter

2. The Appellant criticised the reason of the contested decision because it deviated from a preliminary communication of the Opposition Division (see point VI-(i) above).

2.1. Indeed, the Opposition Division, instead of limiting itself to the evaluation of the requests of the parties, took a more active role in that it suggested the wording of a claim thought to be allowable (communication of 7. November 1991). Apart from being undesirable in view of impartiality in an inter partes procedure, such suggestions may also lead to confusion as regards the provisional and non-binding nature of communications written in procedures before the EPO. In the present case, the Opposition Division, by suggesting an allowable independent claim, led the parties to assume that the claims on file were not allowable; the change of mind of the Opposition Division during the oral proceedings therefore might be seen as rather unexpected and surprising for the parties. Such undesirable course of procedure shows that Opposition Divisions in inter partes procedures should refrain from making suggestions to the parties.

2.2. However, the Board also feels that preliminary opinions reflected in communications during procedures before the EPO should not be interpreted by the parties as binding. It is within the nature of the proceedings before the EPO that a case may appear in a new light once the parties have been fully heard or on the basis of the Opposition Division's own investigation. It can therefore not be avoided that a change of opinion may be brought about even at a late stage, in particular during oral proceedings, which are meant to give the parties the opportunity to clarify their position and to elaborate on their arguments. Furthermore, the contested decision was based on facts, evidence and arguments on file and the Appellant did not show otherwise. Due to this and the above the Board does not find that the Opposition Division's way of conducting the proceedings amounts to a lack of sufficiency or substantiation of the reasons of the contested decision.

Amendments

3. The wording of the claims complies with the requirements of Article 123 EPC.

3.1. In formula (2) of Claim 1 for DE, GB, IT as granted, in the correlation between "Iso" and "Ec" the number "96.5" was amended into "95.5". The value of "96.5" was a printing error that occurred during the printing of the patent specification and which was not present in the text upon which the grant of the patent was based (cf. communications under Rule 51(4) EPC issued on 14 March 1986 and 26 June 1986). Therefore, this amendment does not contravene Article 123(2)(3) EPC.

3.2. The subject-matter of the patent as granted was a copolymer (for DE, GB, IT) or a film made out of a copolymer (for AT) defined by its ethylene content as well as by its isotacticity value. The additional process features are based on page 3, line 59 to page 4, line 2 of the patent specification corresponding to page 7, lines 4 to 18 of the description as originally filed. Therefore, the main request fulfils the requirements of Article 123(2) EPC.

3.3. Since the addition of a further characteristic limits the scope of a claim, there can be no question of an extension of the protection so that Article 123(3) EPC is also complied with.

Prior art

4. As it appears from points III, IV and VI above, the Opposition Division and the Appellant relied on D5 when dealing with substantive issues. This document is referred to at page 4, lines 17 to 18 of the patent specification in the form of the original japanese document as describing a titanium catalyst component corresponding to the one used in the patent in suit. However, as noted by the Respondent in its reply received on 9 August 1990 (page 4, paragraph 4), D5a was not laid open to public inspection until 26 May 1983, thus well after both priority dates of the patent in suit. The situation is different in the case of D5 published on 16 March 1983, which is between the two dates of priority, which implicitly raises the question of the validity of the first priority.

The first priority document discloses a film-forming propylene copolymer having an ethylene content as now claimed (claim), an isotacticity value according to the present formulae (English translation, page 4, first full paragraph) and produced by a catalyst system (English translation page 5, first full paragraph) that is more specific in its second component, the aluminium compound, than the one used in the patent in suit. According to this first priority document a tri-alkyl aluminium compound is used as the second catalyst component, whereas the present claim refers to a more general organoaluminium compound. The priority of the now claimed subject-matter is thus valid insofar as the second catalyst component is a tri-alkyl aluminium compound (see also G 3/93; OJ EPO 1995, 18).

Although expressly invited by the Board in the communication accompanying the summons and at the beginning of the oral proceedings to comment on that issue and explain whether and how D5 could nevertheless be regarded as state of the art within the meaning of Article 54(2) EPC, the Appellant did not provide any argument, but merely repeated that D5 was published between the two dates of priority of the patent in suit. Since the Appellant thereafter no longer relied on the teaching of D5 in support of its substantive objections, there will be no further consideration of that document hereinafter.

Novelty

5. D1 describes a process for preparing a propylene- ethylene copolymer of improved stretchability, in particular suitable for producing biaxially stretched films, which comprises copolymerizing propylene and a small amount of ethylene in the presence of a catalyst system composed of:

(A) titanium trichloride obtained by reducing titanium tetrachloride with an organoaluminium compound and reacting the reduced solid with a complexing agent and a halogen compound simultaneously or successively; and

(B) an organoaluminium compound, and in this process, ethylene is supplied to the polymerization system together with propylene so that the ethylene content in the resulting polymer is in the range of from 0.1 to 1.0. wt% (column 2, lines 7 to 24; column 6, lines 30 to 34; Claim 1). The isotactic values of the resulting copolymers determined by the heptane insoluble polymer (HIP) method which are reported in the examples are higher than 98%.

5.1. For the comparison of the claimed subject-matter with that teaching the three features which define the copolymers in Claim 1, namely the ethylene content (Ec), the isotactic value (Iso) and the process features, will be considered successively.

5.1.1. There is no dispute between the parties that the ethylene content in the copolymers produced by the process according to D1 falls within the range defined under condition (A) in Claim 1 of the patent in suit.

5.1.2. The question of the comparison of the isotactic values has been thoroughly discussed since that parameter is determined by the HIP method in D1, whereas the C13-NMR is used in the patent in suit. In opposition as well as during the appeal proceedings both parties have made opposite assertions regarding the reliability of these two methods and the conclusiveness of any comparison. As will appear from the next paragraph, however, that point is not essential for the issue of novelty, so that no further considerations will be made regarding the isotactic values hereinafter.

5.1.3. The comparison between the definition of the catalyst system used in D1 and that of the catalyst system required according to the patent in suit reveals differences in (i) the composition of the active solid titanium catalyst component, the prior art using generally an ether as the complexing agent (cf. Claim 1 in conjunction with column 3, lines 1 to 29), whereas a magnesium compound and an ester of phthalic acid are used for the preparation of the catalyst compound in the patent in suit, (ii) the granularity of the active catalyst component which has to meet specific criteria of size and distribution in the patent in suit, and (iii) the presence of additional Si-C bonds in the catalyst system used in the patent in suit as the result of the use of an organo silicon compound as the third catalyst ingredient.

The experimental reports submitted during opposition proceedings (Annex to the statements filed on 30 May 1988 and 9 August 1990), wherein the properties of films prepared from polymers obtained by following up Examples 1. and 2 of D1 and from polymers obtained in accordance with Example 3 of the patent in suit were compared, show that in respect of six physical properties, namely haze, impact strength, Young's modulus, heat shrinkage, surface inherent resistivity and stretchability, films prepared in accordance with the teachings of the patent in suit are significantly better. The Appellant's argument that, in the absence of any indication in these test reports regarding the processing conditions, this improved balance of properties of the films did not necessarily reflect differences in the polymers themselves cannot be accepted, since during the oral proceedings before the Board the Respondent specified that the films had been made by following the same procedure. This can only mean that the differences in the properties of the films result from different properties of the polymers, i.e. that the use of different catalyst systems results in different polymers.

This relationship has a considerable bearing on the definition of the polymers in Claim 1. In contrast to the Appellant's argument during oral proceedings that only ethylene content (Ec) and isotactic values (Iso) could be taken into account when assessing novelty, additionally there is a third feature to be considered which is the combination of process features (i) to (iii), with which a complex balance of no less than six physical properties is improved, which could not be expressed by means of conventional parameters. The process features in the claim must therefore be regarded as equivalent to a structural definition of the polymers and thus represent a true limitation with respect to polymers characterized otherwise by their (Ec) and (Iso) parameters only; this demonstrates the novelty of the claimed subject-matter.

5.2. The question of the wording of Claim 1 has to be examined in the light of this conclusion, since a prerequisite for a "product-by-process" claim to be allowable is that the products themselves be both novel and inventive. As far as the characterization of the polymers by process features is concerned, in view of the complex correlation between catalyst features and structural features of the resulting polymers, it is the only way to express the improvement of the balance of properties, which six physical properties are shown to be involved.

This is in line with decision T 150/82, OJ EPO 1984, 109, in which in a similar situation, the Board took the view "that in order to minimise uncertainty, the form for a claim to a patentable product as such defined in terms of a process of manufacture (i.e. "product-by- process claims"), should be reserved for cases where the product cannot be satisfactorily defined by reference to its composition, structure or some other testable parameters" (Reasons, point 10).

5.3. In view of the foregoing it is concluded that the requirement of novelty is met and that the formulation of the claim is adequate to express the contribution of the catalyst system to the definition of the products.

5.4. This conclusion also applies to Claim 1 for AT, since products made out of these novel copolymers are also novel.

Inventive step.

6. The patent in suit concerns film-forming copolymers, films thereof and a process for the production of the films. As stated above, such copolymers are disclosed in D1, which the Board, like the Opposition Division, regards as the closest state of the art. Although the copolymers obtained in D1 are said to have good stretchability, the level achieved could not be regarded as entirely satisfactory. Moreover, other properties, like the haze, impact strength, Young's modulus, surface inherent resistivity and heat shrinkage and in particular the balance between these properties, were capable of improvement.

In view of the above the technical problem underlying the patent in suit may thus be seen in providing a copolymer having not only good mechanical and optical properties, but also a good balance between these properties.

According to the patent in suit this problem is to be solved by a copolymer having a low ethylene content, high isotacticity and obtainable by using a specific catalyst system.

The examples of the patent in suit and also the additional experiments mentioned above demonstrate that the various aspects of the above-defined problem are effectively solved.

7. It remains to be decided whether the claimed subject- matter is obvious having regard to the documents on file.

7.1. D1 considers the influence of the catalyst system on the properties of the copolymer and the products made thereof (see column 1, lines 18 to 65). However, D1 concerns in particular catalysts containing a specific type of titanium trichloride (see column 4, lines 49 to 68) and is silent about catalyst systems based on a spherical solid titanium component containing magnesium, titanium, chlorine and an ester of phthalic acid with an alcohol having at least 2 carbon atoms. Therefore, D1 contains no teaching as to the use of such catalysts and its effects on the product properties and hence does not provide a solution to the above-defined problem.

In fact, D1 would discourage the skilled person to use any catalyst other than those specified therein. D1 teaches that the use of a specific catalyst, in combination with the use of a limited amount of ethylene, results in a number of advantages that could not be achieved previously with other catalysts. The shortcomings reported for previous prior art propylene copolymers, particularly in terms of mechanical properties, clearly show that the improvement of one property is often achieved at the expense of other properties. These shortcomings are overcome by applying the teaching of D1, which results in particular in the enhancement of stretchability without sacrificing the Young's modulus. Therefore, any attempt to use other catalysts systems than those disclosed in D1 would in the first place mean foregoing the advantages conferred by these catalysts. The prior art survey in the introduction of the patent in suit also shows that it had not been possible to combine various advantageous properties, which confirms the specificity of the catalyst system and the difficulty to reach a good balance of properties. As the latter aspect involving no less than six components is not considered in D1, it is evident that this citation cannot suggest any feature within the terms of the patent in suit.

7.2. In view of the above, the Board concludes that the copolymer as defined in Claim 1 of the main request for DE, GB, IT involves an inventive step. It follows that the films as defined in Claim 1 of the main request for AT, which are made out of these inventive copolymers, are also inventive.

8. As both Claims 1 for DE, GB, IT and for AT are allowable, the same goes for dependent Claims 2 to 4 for DE, GB, IT and 2 to 3 for AT, which all refer to the product according to Claims 1, and the patentability of which is supported by that of Claims 1.