T 0179/03 28-03-2007

Summary of Facts and Submissions

I. The appeal is against a decision of the Opposition Division to revoke European patent 0 772 488, which originates from international patent application PCT/US95/10080 published as WO-A-96/03202 and claiming a priority date of 28 July 1994. The independent claims as granted read as follows:

"1. A composite porous membrane which comprises a porous membrane substrate having an average pore size of between 0.01 and 10 microns, preferably between 0,05 and 5 microns, e.g. between 0.1 and 1.0 microns, formed of a first polymer, said substrate being directly coated over its entire surface by impregnation with a second polymer composition in a solvent which is crosslinked by exposing the impregnated substrate to ultraviolet light and/or mild heat and rendered insoluble in situ on said substrate with a free radical polymerization initiator, e.g. comprising a persulfate, and in the absence of a crosslinking agent, said composite porous membrane having essentially the same porous configuration as said porous membrane substrate."

"11. A process for forming a composite porous membrane having a porous membrane substrate formed of a first polymer with an average pore size of between 0.01 and 10 microns, preferably between 0.05 and 5.0 microns, and most preferably between 0.1 and 1.0 microns, said substrate being directly coated over its entire surface with a second polymer composition in a solvent which is crosslinked and rendered insoluble in situ on said substrate which comprises:

a) impregnating said substrate with a solution in said solvent of said second polymer and a free radical polymerization initiator, such as persulfate,

b) exposing the impregnated substrate from step a) to ultraviolet light and/or mild heat which effects a temperature of said solution between 45ºC and 100ºC to effect crosslinking of said second polymer, and to render said second polymer insoluble and

c) washing said impregnated substrate from step b) with a liquid to remove soluble polymer not rendered insoluble, excess polymerization initiator and reaction products of said polymerization initiator."

II. The European patent had been opposed on the grounds that the disclosure of the patent was insufficient (Article 100(b) EPC) (opponent 02) and that its claimed subject-matter lacked novelty and an inventive step (Article 100(a) EPC) (opponents 01 and 02) having regard inter alia to the following documents:

D1: EP-B-0 571 871;

D2: US-A-4 113 912;

D5: Kirk-Othmer, Encyclopedia of Chemical Technology, second completely revised edition, Volume 21, pages 427-440, John Wiley & Sons, 1970;

D6: EP-A-0 498 414;

E1: DE-A-4 217 335.

III. The decision under appeal was based on two sets of amended claims 1 to 25 filed with letter dated 26 September 2002 as the Main and the Auxiliary Requests.

The respective independent Claims 1 of those requests read as follows (emphasis added by the Board to show the amendments to the claims as granted):

Main Request

"1. A composite porous membrane which comprises a porous membrane substrate having a hydrophobic surface and an average pore size of between 0.01 and 10 microns, formed of a first polymer, said substrate being directly coated over its entire surface by impregnation with a second polymer composition in a solvent which is crosslinked by exposing the impregnated surface to ultraviolet light and/or mild heat and rendered insoluble in situ on said substrate with a free radical polymerization initiator and in the absence of a crosslinking agent, said composite porous membrane having essentially the same porous configuration as said porous membrane substrate."

Auxiliary Request

"1. A composite porous membrane which comprises a porous membrane substrate having a hydrophobic surface and an average pore size of between 0.01 and 10 microns, formed of a first polymer, said substrate being directly coated over its entire surface by impregnation with a second polymer composition in a solvent which is crosslinked by exposing the impregnated surface to ultraviolet light and/or mild heat and rendered insoluble in situ on said substrate with a free radical polymerization initiator and in the absence of a crosslinking agent, said composite porous membrane having essentially the same porous configuration as said porous membrane substrate and wherein said second polymer is a hydrophilic polymer."

The Opposition Division revoked the patent for lack of an inventive step, on the basis of reasoning which can be summarised as follows:

(a) The ground of opposition under Article 100(b) EPC (insufficiency of disclosure) raised by opponent 02 lacked any indication of facts, evidence and arguments, and thus was rejected.

(b) As to novelty, D1 did not unambiguously disclose that the porous membrane substrate had a hydrophobic surface. According to D2, in which a temperature of 150º to 160ºC, or even 200ºC, was used to insolubilise the coating, a hot water step at a temperature below 100ºC was necessary to replace the evaporated solvent in the coating. Thus, the feature "crosslinking by exposing the impregnated surface to ... mild heat", which implied that at a such low temperature degradation of the membrane would not take place, distinguished the claimed membrane from that of D2. D6 did not disclose a membrane prepared without using a crosslinking agent. Therefore, the subject-matter of independent Claim 1 according to each of the Main and Auxiliary Requests was novel over the prior art described in any of D1, D2 and D6. Furthermore, there was no reason to believe that any of the other cited documents would destroy the novelty of any of the claims of the Main or the Auxiliary requests.

(c) As regards inventive step, D1 described the closest prior art. The only feature of Claim 1 according to the Main Request which was not shown in D1 was the "hydrophobic surface" of the porous membrane substrate and the only features according to Claim 1 of the Auxiliary Request which were not shown in D1 were the "hydrophobic surface" of the porous membrane substrate and the "second polymer is a hydrophilic polymer". However, D1 dealt with polysulfones, which polymers were hydrophobic, and taught that these polysulfones should be made permanently hydrophilic. Although D1 exemplified porous substrates having a partially hydrophilic surface, its teaching was not restricted to polysulfones having partly hydrophilic surfaces. Hence, for the skilled person starting from D1, it would be obvious to coat porous membrane substrates having a hydrophobic surface to obtain permanently hydrophilic membranes. Since permanently hydrophilic membranes were obtained from the examples of D1, the coating copolymers used in those examples, albeit containing a hydrophobic monomer, were nevertheless hydrophilic. Hence, the subject-matter of Claim 1 of each of the Main and the Auxiliary Requests did not involve an inventive step.

(d) Since therefore the ground of opposition under Article 100(a) EPC (lack of inventive step) prejudiced the maintenance of the patent in suit, that patent should be revoked.

IV. On 5 February 2003, the patent proprietors lodged an appeal against that decision and paid the appeal fee. In the statement setting out the grounds of appeal, received on 14 April 2003, the appellants enclosed a Declaration by Dr Moya dated 4 April 2003. Then, in response to a communication of the Board in preparation for the oral proceedings, the appellants submitted five sets of amended claims as Auxiliary Requests 2 to 6, as well as three documents concerning the definitions of the terms "hydrophobic" and "hydrophilic" (letter dated 28 February 2007).

V. In their response to the statement setting out the grounds of appeal, opponents 01 (herein after, respondents 01) maintained their position that the subject-matter of Claim 1 of each of the Main and Auxiliary Requests lacked novelty and an inventive step, argued against the Declaration by Dr Moya and submitted comparative test results concerning repetition of Example 4 of D1 (letter dated 31 October 2003).

VI. Opponent 02 (herein after, respondent 02) argued against the admissibility of the Declaration by Dr Moya filed with the statement setting out the grounds of appeal (letter dated 1 September 2003). Then, she announced that she would not attend the oral proceedings set by the Board (Letter dated 15 December 2006).

VII. In the communication in preparation for oral proceedings, the Board had inter alia made comments on the clarity of the alleged distinguishing feature of Claim 1 according to the Main Request, namely the feature "having a hydrophobic surface" that had been taken from the description, on the interpretation of the feature "hydrophilic polymer" present in Claim 1 according to the Auxiliary Request as well as on the test results submitted by appellants and respondents 01.

VIII. Oral proceedings were held on 28 March 2007. Respondent 02 did not appear, as announced in their letter dated 15 December 2006. Oral proceedings were continued without her, pursuant to Rule 71(2) EPC.

After a discussion with the parties, the Board expressed the preliminary view that the subject-matter of Claim 1 according to the Main Request lacked novelty over the membrane described in E1. The appellants withdrew the Auxiliary Request and asked that the discussion turn to Auxiliary Request 2. The Board noted that Claim 1 according to Auxiliary Request 2 lacked features present in Claim 1 as granted and thus would not appear to be admissible; even if those missing features were present, the feature "consist of hydrophilic polymer" did not appear to distinguish the claimed membrane from that described in E1. The appellants then submitted a fresh Auxiliary Request 3.

Respondents 01 submitted a copy of a document from BASF concerning the physical properties, in particular the water-solubility, of the copolymers for the coating exemplified in E1, namely: "BASF, Luviskol(r)VA Grades, Technical Information, pages 1-19, May 1999" (hereinafter, D7).

After the Board had expressed the preliminary view that fresh Auxiliary Request 3 would not be acceptable because the amendments to Claim 1 still did not introduce any distinction of the claimed membrane from that described in E1 for the purpose of novelty and inventive step, the appellants did not maintain Auxiliary Requests 4 and 5 then on file but submitted a set of amended claims 1 to 17 identified as the Final Main request, as the sole request replacing all the requests then on file. Independent Claims 1 and 10 of the Final Main Request read as follows:

"1. A composite porous membrane which comprises a porous hydrophobic membrane substrate having an average pore size of between 0.01 and 10 microns, preferably between 0,05 and 5 microns, e.g. between 0.1 and 1.0 microns, formed of a first polymer, said substrate being directly coated over its entire surface by impregnation with a second polymer composition in a solvent which is crosslinked by exposing the impregnated substrate to ultraviolet light and/or mild heat and rendered insoluble in situ on said substrate with a free radical polymerization initiator, e.g. comprising a persulfate, and in the absence of a crosslinking agent, said composite porous membrane having essentially the same porous configuration as said porous membrane substrate and wherein said second polymer is a hydrophillic (sic) polymer and said first polymer is selected from the group consisting of a halogenated hydrocarbon polymer, a nitrogen containing polymer and an olefin polymer." (Emphasis added by the Board to show the amendments to the claims as granted)

"10. A process for forming a composite porous membrane having a porous hydrophobic membrane substrate formed of a first polymer with an average pore size of between 0.01 and 10 microns, preferably between 0.05 and 5.0 microns, and most preferably between 0.1 and 1.0 microns, said substrate being directly coated over its entire surface with a second polymer composition in a solvent which is crosslinked and rendered insoluble in situ on said substrate which comprises:

a) impregnating said substrate with a solution in said solvent of said second polymer and a free radical polymerization initiator, such as persulfate,

b) exposing the impregnated substrate from step a) to ultraviolet light and/or mild heat which effects a temperature of said solution between 45ºC and 100ºC to effect crosslinking of said second polymer, and to render said second polymer insoluble and

c) washing said impregnated substrate from step b) with a liquid to remove soluble polymer not rendered insoluble, excess polymerization initiator and reaction products of said polymerization initiator,

wherein said second polymer is hydrophillic (sic) and said solvent is water." (Emphasis added by the Board)

IX. The appellants essentially argued as follows:

Procedural matters

In the decision under appeal, the patent was revoked for lack of an inventive step of the claimed subject-matter having regard to D1, which was a specification of a granted European patent. However, that patent specification had been published after the priority date of the patent in suit. E1, instead, cited by opponent 02, had been published before the priority date of the patent in suit, but its content was not the same as that of D1. In particular, passages of D1 referred to in the decision under appeal were not present in E1. Therefore, the decision to revoke the patent having regard to D1 was wrong. Consequently, D1 should be disregarded and the matter should be discussed having regard to E1.

Since D7 was late filed and late published, it should not be considered.

Final Main Request

(a) The amendments to the claims were based on the application as filed and the request was thus admissible.

(b) Since the expression "having a hydrophobic surface" was no longer present in the claims, the objection under Article 84 EPC as to clarity of that expression had been overcome.

(c) The subject-matter of Claim 1 was novel having regard to D2, because D2 disclosed crosslinking techniques such as high temperature, radiation and use of crosslinking agents, all of which produced higher degradation and higher amounts of extractable residues.

(d) As to inventive step, D2 described the closest prior art. The problem to be solved was how to produce a hydrophilic membrane starting from a hydrophobic substrate while reducing the extractables and avoiding degradation of the membrane in its formation. According to the statements in the patent in suit, that problem had been solved. The opponents had not denied it. D2 did not contain any hint at changing its crosslinking technique toward the less degrading technique disclosed in the patent in suit. Even if the problem had not been solved, D2 did not teach to move away from the means of crosslinking disclosed. The further documents cited such as E1 concerned a different substrate and would not be combined with D2. Hence, the subject-matter of Claim 1 involved an inventive step.

(e) As regards the subject-matter of Claim 10, the closest prior art was described in E1, which concerned substrates made of polysulfone that should be made permanently hydrophilic. Although E1 acknowledged that polysulfone was hydrophobic, to make it permanently hydrophilic its surface should at least be made partially hydrophilic before coating. Furthermore, since the copolymer used in the coating solution described in E1 should be dissolved in a mixture of water and alcohol, it was not water-soluble. This was also apparent from D5, which showed that copolymers such as those used in E1 were commercially available in alcoholic solution. In any case, it had been shown by the appellants that the process of E1 did not work on polyethylene. Therefore, also the subject-matter of Claim 10 involved an inventive step.

(f) In summary, the amended patent fulfilled the requirements of the EPC.

X. Respondents 01 essentially argued as follows:

Procedural matters

Respondents 01 did not object to discuss the matter having regard to E1 instead of D1.

D7 was in reaction to the arguments submitted by the appellants on the coating solution disclosed in E1, it was highly relevant and should thus be admitted in the proceedings.

Final Main Request

(a) The amendments to the claims were not objected to.

(b) After the deletion of the feature "having a hydrophobic surface" from the claims, clarity under Article 84 EPC was no longer an issue.

(c) E1 was no longer relevant for the novelty of the subject-matter of Claim 1. However, there was no evidence that the product as claimed differed from the product of D2 in any measurable property. Hence, the product as defined in Claim 1 was not novel over D2.

(d) If the product of Claim 1 was found to be novel, D2 would be the closest prior art document. The problem to be solved would be how to produce a hydrophilic membrane starting from a hydrophobic substrate while reducing degradation and formation of extractable residues during the manufacture. There was no proof over D2, such as comparative examples, that that problem had been solved. Hence, the problem should be reformulated as to provide a further product. The coating copolymer composition described in E1 should impart a hydrophilic character to the polysulfone substrate and hence it must be hydrophilic. Apart that E1 did not exclude hydrophilic copolymers, any copolymer containing relatively small proportion of a hydrophobic monomer still was hydrophilic, independently from the fact that the exemplified copolymer of E1 was dissolved in a water-alcohol mixture. In that respect, Claim 6 of the granted patent in suit did not exclude the presence of further monomers which might be hydrophobic. Since E1 hinted at a coating process that permitted to obtain less degradation and residues, the claimed subject-matter was obvious having regard to the combination of D2 with E1. Also the further documents cited such as D5 contained hints at moving towards the process of the patent in suit. Hence, the subject-matter of Claim 1, if novel, would not involve an inventive step.

(e) E1 was still relevant to the process defined in Claim 10. The only distinguishing features of the process defined in Claim 10, compared to that of E1, were the final washing step and the choice of water as a solvent. Since the membranes of E1 should inter alia be suitable for the filtration of drinking liquids and pharmaceutical products, a final washing step before use was imperative. Furthermore, it was apparent from E1 that the addition of the alcohol was necessary only as far as any substantial turbidity of the aqueous coating solution arose. Therefore, the process of Claim 10 was obvious having regard to that of E1.

(f) The claimed subject-matter did not fulfil the requirements of the EPC and the patent in suit should be revoked.

XI. The appellants (patent proprietors) requested that the decision under appeal be set aside and that the patent be maintained on the basis of the Final Main Request submitted at the oral proceedings on 28 March 2007.

XII. Respondents 01 (opponents 01) requested that the appeal be dismissed.

XIII. Respondent 02 had requested in writing the dismissal of the appeal. She had additionally made the procedural request that the Declaration by Dr Wilson Moya dated 4 April 2003 filed by the appellants (patent proprietors) with their statement setting out the grounds of appeal not be admitted. If the Board were to admit this Declaration, then the case should be remitted back to the Opposition Division for a fresh decision, so that the right of appeal of opponent 02 be guaranteed, if the Opposition Division decided, on the basis of the newly filed evidence, to maintain the patent (letter dated 1 September 2003).