T 0477/01 05-11-2003

Summary of Facts and Submissions

I. The grant of the European patent No. 0 657 476 in the name of Sumitomo Chemical Company Limited in respect of European patent application No. 94 118 696.7, filed on 28 November 1994 and claiming two JP priorities of 6 December 1993 and 20. April 1994 was announced on 3 June 1998 (Bulletin 1998/23) on the basis of 11 claims.

Independent Claims 1, 3, 5, 8 and 11 read as follows:

"1. An Alpha-olefin polymer obtained by polymerizing an Alpha-olefin having 3 or more carbon atoms which satisfies the following conditions:

the intrinsic viscosity [Eta](measured in tetralin solvent at 135°C) of said polymer is not lower than 0.5 and not higher than 10, and 20°C xylene-soluble fraction (CXS) content (% by weight) and 105°C xylene-insoluble fraction (XIS) content (% by weight) of said polymer satisfy the following condition:

XIS =< 70.00 - 3.64CXS

provided that CXS is not smaller than 0 and not greater than 15.

3. A process for producing an Alpha-olefin polymer which comprises producing an Alpha-olefin polymer obtained by polymerizing an Alpha-olefin having 3 or more carbon atoms and satisfying the following conditions:

the intrinsic viscosity [Eta](measured in tetralin solvent at 135°C) of said polymer is not lower than 0.5 and not higher than 10, and

20°C xylene-soluble fraction (CXS) content (% by weight) and 105°C xylene-insoluble fraction (XIS) content (% by weight) of said polymer satisfy the following condition:

XIS =< 70.00 - 3.64CXS

provided that CXS is not smaller than 0 and not greater than 15, by the use of a catalyst system consisting of

(A) a solid catalyst component containing magnesium, titanium, halogen and an electron donative compound as essential components,

(B) an organoaluminum compound, and

(C) an electron donative compound component.

5. A polypropylene for use in the production of a biaxially oriented film which satisfies the following conditions (1) to (3):

(1) the content of 20°C xylene-soluble fraction (CXS) is 3.5% by weight or less,

(2) the content of 20°C xylene-soluble fraction (CXS, % by weight) and the content of 105°C xylene- insoluble fraction (XIS, % by weight) satisfy the following condition:

XIS =< 70.00 - 3.64CXS,

and

(3) melt flow rate (MFR) at 230°C is from 0.5 to 10.0. g/10 minutes.

8. A polypropylene for use in the production of a biaxially oriented film obtained by carrying out a polymerization reaction by the use of a catalyst system consisting of:

(A) a solid catalyst component containing magnesium, titanium, halogen and an electron donative compound as essential components,

(B) an organoaluminum compound, and

(C) an electron donative compound component, which satisfies the following conditions (1) to (3):

(1) the content of 20°C xylene-soluble fraction (CXS) is 3.5% by weight or less,

(2) the content of 20°C xylene-soluble fraction (CXS, % by weight) and the content of 105°C xylene- insoluble fraction (XIS, % by weight) satisfy the following condition:

XIS =< 70.00 - 3.64CXS,

and

(3) melt flow rate (MFR) at 230°C is from 0.5 to 10.0. g/10 minutes.

11. A biaxially oriented film obtained by subjecting a polypropylene for use in the production of a biaxially oriented film according to one of Claims 5 to 10 to a stretching processing."

Claims 2, 4, 6 to 7, and 9 to 10 were dependent on Claims 1, 3, 5, and 8 respectively.

II. On 1 March 1999, a Notice of Opposition was filed by Targor GmbH (later Basell Polyolefine GmbH), in which revocation of the patent in its entirety was requested on the grounds of lack of novelty and lack of inventive step (Article 100(a) EPC).

The objections were supported inter alia by the following documents:

D1: EP-A-0 318 049;

D2: Masahiro Kakugo et al "Microtacticity Distribution of Polypropylenes Prepared with Heterogeneous Ziegler-Natta Catalysts"; Macromolecules, 1988, Vol. 21, pages 314-319;

D3: Masahiro Kakugo et al "Characteristics of Ethylene- Propylene and Propylene-1-Butene Copolymerization over TiCl3. 1/3 AlCl3-Al(C2H5)2Cl"; Macromolecules, 1988, Vol. 21, pages 2309-2313;

D4: Akinori Toyota et al "Polymerization of propylene with an ethylene bis(1-indenyl)hafnium dichloride and methylaluminoxane catalyst system"; Journal of Molecular Catalysis, Vol. 56, 1989, pages 237-247;

D5: Dr. L. Bothe et al "Methoden zur Charakterisierung von Polypropylen", Kunststoffe, Vol.74, Nr.4, 1984, pages 225-228;

D6: C. Tzoganakis et al "Effect of Molecular Weight Distribution on the Rheological and Mechanical Properties of Polypropylene", Polymer Engineering and Science, March 1989, Vol. 29, No. 6, pages 390- 396;

D7: EP-A-0 515 855; and

D8: Kunststoff Taschenbuch, 24th Edition, 1989, Hanser Verlag, page 371.

III. In its decision announced orally on 7 February 2001 and issued in writing on 22 February 2001, the Opposition Division held that the grounds of opposition raised and substantiated by the Opponent did not prejudice the maintenance of the patent in amended form.

The decision was based on Claims 1 to 11 as granted as main request, on Claims 1 to 11 as submitted during the oral proceedings of 7 February 2001 as first auxiliary request, and on Claims 1 to 11 as submitted during the oral proceedings of 7 February 2001 as second auxiliary request.

Claims 1 to 11 of the first auxiliary request differed from Claims 1 to 11 as granted, in that it had been indicated in independent Claims 1 and 3 that the intrinsic viscosity of the polymer must be not lower than 1,22 and not higher than 10.

Claims 1 to 11 of the second auxiliary request differed from Claims 1 to 11 as granted in that the value of the CXS of the polymer had been limited to 0,1 to 12 in independent Claims 1 and 3, and in that Claims 5 and 8 had been made dependent on Claim 1.

The decision stated that Claim 1 of the main request lacked novelty in view of the polymers of fractions 11 of Table II, 10 and 12 of Table III and 13 of Table IV of document D3. Consequently the main request was refused.

Concerning the first auxiliary request, the decision held that the subject-matter of Claim 1 differed from fraction 13 of Table IV of D3 only in that the polymer according to Claim 1 should exhibit an intrinsic viscosity of at least 1.22 instead of 0.71 for the polymer of fraction 13 of D3. According to the decision, no unexpected effect could, however, be seen in relation to that increase in intrinsic viscosity. Thus, the Opposition Division came to the conclusion that the subject-matter of Claim 1 of the first auxiliary request lacked inventive step. This led to the refusal of the first auxiliary request.

The decision further stated that the subject-matter of the second auxiliary request was novel, since documents D1, D3, and D4 did not disclose the XIS parameter of the polymer according to Claim 1 of the second auxiliary request.

D1 or D4 (cf. in particular Examples 1 to 4, and 6 to 8 of D1,and Example 1 of Table 1 of D4) could be considered as the closest state of the art. The polymers disclosed in D1 or D4 differed from those of Claim 1 of the second auxiliary request in that they did not exhibit an XIS value in the claimed range. Starting from D1 or D4 the technical problem was seen as to improve properties of biaxially stretched films made therefrom.

The Examples of the patent in suit showed that this problem was effectively solved. Thus, inventive step was acknowledged for the subject-matter of the claims 1 to 11 of the second auxiliary request.

IV. A Notice of Appeal was lodged on 2 May 2001 by the Appellant (Opponent), with simultaneous payment of the prescribed fee.

With the Statement of Grounds of Appeal filed on 4 July 2001, the Appellant submitted an experimental report. It also argued essentially as follows:

(i) Example 1 in Table 1 of document D4 disclosed the manufacture of a propylene polymer exhibiting an intrinsic viscosity of 2,96 dl/g.

(ii) Although the parameters XIS and CXS were not explicitly disclosed in D4, the polymer obtained in this Example 1 would meet these requirements.

(iii) In that respect documents D2 and D3 showed, as submitted in the letter of 7 December 2000 of the Opponent (Appellant), the relation between the melting points of the polymer and the elution temperature, i.e. its XIS value.

(iv) Furthermore, Run H of the annexed experimental report, which was a repetition of Example 1 of Table 1 of D4, showed that the polymer obtained had a CXS value of 0.1% by weight and an XIS value of 8% by weight.

(v) Thus D4 was novelty destroying document for Claim 1 of the patent in suit.

(vi) One would come to the same conclusion for the Examples 1, 3, 4, 6 and 7 of D1.

(vii) Claim 2 would also lack novelty in view of D4 and D1 and Claims 5 to 7 were not novel over D4.

(viii) Since the use of the catalyst mentioned in Claims 3, 4, 8, 9 and 10 was known from document D7, these Claims lacked inventive step in view of the combination of either D1 with D7 or D4 and D7.

(ix) It was also known from D8 that polypropylene could be used for the manufacture of biaxially stretched films. Thus Claim 11 would lack inventive step in view of the combination of D4 with D8.

V. With its letter dated 14 February 2002, the Respondent (Patent Proprietor) submitted a set of 6 Claims and requested the patent be maintained on that basis.

Independent Claim 1 read as follows:

"A process for producing an Alpha-olefin polymer which comprises producing an Alpha-olefin polymer by polymerizing an Alpha-olefin having 3 or more carbon atoms, said Alpha-olefin polymer satisfying the following conditions:

the intrinsic viscosity [Eta] (measured in tetralin solvent at 135°C) of said polymer is not lower than 0.5 and not higher than 10, and

20° C xylene-soluble fraction (CXS) content (% by weight) and 105°C xylene-insoluble fraction (XIS) content (% by weight) of said polymer satisfy the following condition:

XIS =< 70.00 - 3.64CXS

provided that CXS is not smaller than 0.1 and not greater than 12, by the use of a catalyst system consisting of

(A) a solid catalyst component containing magnesium, titanium, halogen and an electron donative compound as essential components,

(B) an organoaluminum compound, and

(C) an electron donative compound component."

Dependent Claim 3 read as follows:

"A process for producing a polypropylene for use in the production of a biaxially oriented film according to Claim 1, which comprises producing a polypropylene by polymerizing propylene by the use of a catalyst system consisiting (sic) of:

(A) a solid catalyst component containing magnesium, titanium, halogen and an electron donative compound as essential components,

(B) an organoaluminum compound, and

(C) an electron donative compound component, wherein said polypropylene obtained satisfies the following conditions (1) to (3):

(1) the content of 20°C xylene-soluble fraction (CXS) is 3.5% by weight or less,

(2) the content of 20°C xylene-soluble fraction (CXS, % by weight) and the content of 105°C xylene-insoluble fraction (XIS, % by weight) satisfy the following condition:

XIS =< 70.00 - 3.64CXS, and

(3) melt flow rate (MFR) at 230°C is from 0.5 to 10.0 g/10 minutes."

Independent Claim 6 reads as follows:

"Use of a polypropylene obtained according to the process claimed in Claim 3 in a stretching process for the production of a biaxially oriented film."

Claims 2 and 4 to 5 were dependent on Claims 1 and 3 respectively.

The Respondent argued essentially as follows:

(i) Claim 1 was directed to a process for producing an Alpha-olefin having specific intrinsic viscosity, CXS and XIS values and obtained while using a heterogeneous Ziegler-Natta catalyst.

(ii) This Claim was novel over D1 to D8 since none of these documents disclosed the manufacture of such an Alpha-olefin polymer in the presence of such catalyst.

(iii) Furthermore, the polymer obtained differed from the polymer obtained by using a homogeneous catalyst as used in D1. This was evident from pages 433 and 440 of Summary Report of the Sixth International Business Forum on Speciality Polyolefins SPO 1996, annexed to the letter of 14. February 2002.

(iv) This document showed that polypropylene polymers obtained by using single site metallocene catalyst had poor stretchability.

(v) D1 and D4 did not suggest that an Alpha-olefin polymer having the properties set out in Claim 1 might be obtained with a Ziegler-Natta catalyst system.

(vi) D7 could not suggest that Alpha-olefin polymers having the properties set out in Claim 1 would have improved stretchability and stiffness.

(vii) Thus, the subject-matter of Claims 1 to 6 was novel and inventive over the cited prior art.

VI. With its letter dated 11 August 2003, the Appellant indicated, that, in view of the amended set of Claims submitted by the Respondent with its letter of 14. February 2002, it maintained its request for the revocation of the patent in totality.

VII. Oral proceedings were held on 5 November 2003.

Following preliminary observations of the Board concerning the wording of Claims 3 and 6 of the set of claims 1 to 6 filed by the Respondent with its letter dated 14 February 2002, the Respondent submitted a set of Claims 1 to 5 in order to replace its main request on file.

This set of claims differed from that submitted with the letter dated 14 February 2002 in that Claim 6 thereof had been deleted, in that a clerical minor error had been corrected in Claim 4 (i.e. "wherin" should read "wherein") and in that Claim 3 had been amended to read as follows:

"A process according to Claim 1 wherein the Alpha- olefin polymer is a polypropylene for use in the production of a biaxially oriented film, wherein the process comprises producing a polypropylene by polymerizing propylene by the use of a catalyst system consisting of:

(A) a solid catalyst component containing magnesium, titanium, halogen and an electron donative compound as essential components,

(B) an organoaluminum compound, and

(C) an electrodonative compound component, wherein said polypropylene obtained satisfies the following conditions (1) to (3):

(1) the content of 20°C xylene-soluble fraction (CXS) is 3.5% by weight or less,

(2) the content of 20°C xylene-soluble fraction (CXS, % by weight) and the content of 105°C xylene-insoluble fraction (XIS, % by weight) satisfy the following condition:

XIS =< 70.00 - 3.64CXS, and

(3) melt flow rate (MFR) at 230°C is from 0.5 to 10.0. g/10 minutes."

The submissions of the Parties at the oral proceedings may be summarized as follows:

(i) While the Appellant declared that it had no objection under Articles 54, 84, 123(2) and 123(3) EPC against the new main request of the Respondent and did not contest that the polypropylene resins obtained by the claimed process had good film processing properties, it submitted, however, that the subject-matter of the main request lacked inventive step. In that respect it argued essentially as follows:

(i.1) Document D4 should be considered as the closest state of the art, since it disclosed in Run 1 of Table I a polypropylene polymer which fulfilled all the requirements set out in Claim 1 of the patent in suit in terms of intrinsic viscosity, CXS content and relation between XIS and CXS.

(i.2) The polypropylene disclosed in that Example of D4 had been obtained while using a metallocene catalyst (i.e. ethylene bis(1-indenyl)hafnium dichloride).

(i.3) Even if D4 did not expressly relate to the manufacture of films, it was clear for the skilled person in view of document D1 which also referred to the manufacture of polypropylene polymers for making films in the presence of similar metallocene catalysts (i.e. zirconium based), that the polypropylene disclosed in Run 1 of D4 would be particularly suitable for making films.

(i.4) Thus, starting from D4 the technical problem might be seen as to provide an alternative process for making a polypropylene polymer suitable for making films.

(i.5) Since Ziegler Natta catalysts such as those used in the patent in suit were well known in the art (cf. for example document D7) in the manufacture of polypropylene resins, it would have been obvious for the skilled person to adapt the process of D4 to the use of the Ziegler-Natta catalysts such as those disclosed in D7 in order to obtain a polypropylene having the characteristics of that of Run 1 of D4.

(ii) The Respondent, while essentially relying on the arguments presented in its letter dated 14. February 2002, presented further arguments which may be summarized as follows:

(ii.1) Document D1 should represent the closest state of the art.

(ii.2) D1 related to polypropylene resins useful for the manufacture of films, but D1 contained no information concerning the XIS value of the polypropylene resins disclosed therein.

(ii.3) It could not be deduced from the melting point of the polypropylene disclosed in the Examples of D1, as had been done by the Appellant in its letter of 7 December 2000, that these resins would also have a XIS value in the range required in the patent in suit.

(ii.4) The polypropylenes according to D1 were said to exhibit a high crystallinity. This would result in films of high stiffness but of reduced stretchability.

(ii.5) In contrast, the polypropylenes obtained according to the process of the patent in suit led to films having a good compromise of stretchability and stiffness. In that respect, the value of the XIS parameter of the polypropylene resin was of utmost importance in order to obtain such properties.

(ii.6) Thus, starting from D1 the technical problem must be seen as to provide a process for polypropylene resins having improved films processing properties.

(ii.7) Document D4 was a scientific publication dealing with polymerization of propylene in presence of metallocene catalysts and was not concerned with the manufacture of films.

(ii.8) Although document D7 disclosed the catalysts used in the patent in suit, it did not give any indication on the CXS and the XIS values of the polypropylenes obtained.

(ii.9) Thus, the subject-matter of Claims 1 to 5 involved an inventive step.

VIII. The Appellant requested that the decision under appeal be set aside and the European patent No. 0 657 476 be revoked.

The Respondent requested that the patent be maintained on the basis of the main request consisting of Claims 1 to 5 filed during the oral proceedings.