T 0299/03 17-03-2005

1. The appeal is admissible.

Procedural matters

2. As appears from the Summary of Facts and Submissions, the Board was faced with procedural issues concerning (i) the absence of Opponent I at the oral proceedings, (ii) the admissibility of the auxiliary request filed by the Respondent at the oral proceedings, and (iii) the question as to whether document D14 should be introduced into the proceedings.

2.1 As mentioned above in paragraph VII, Opponent I informed the Board with its letter dated 20 January 2005 that it would not be represented at the oral proceedings. In accordance with Rule 71(2) EPC, the proceedings were continued without it.

2.2 As indicated in paragraph VIII above, the Respondent filed an auxiliary request during the oral proceedings. As is evident from this paragraph, the filing of this set of claims has been made in response to the objections raised by the Board at the oral proceedings in connection with the question of allowability of Claim 1 of the main request under Article 123(2) EPC, so that the filing of this auxiliary request cannot amount to an abuse of procedural rights.

2.3 The Board further notes that the amendment made in Claim 1 (restriction of the upper limit of the amount of water from 102 ppm to 100 ppm) does not substantially change the factual framework of the contested decision, so that no disadvantage would be caused to the Appellant by the late filing of this auxiliary request if it was admitted into the proceedings.

2.4 Under these circumstances the Board decided to admit the auxiliary request into the proceedings.

2.5 During the oral proceedings, the Appellant wished to refer on document D14 when presenting its line of argument concerning the question of inventive step.

2.6 In this connection, the Board notes firstly (i) that document D14 had been filed after the nine-month opposition period, and secondly that the Opposition Division did not admit this late filed document into the opposition proceedings on the grounds that it was not particularly relevant either for novelty or inventive step.

2.7 The Board further observes that, in the written appeal proceedings, the Appellant neither argued that the Opposition Division had wrongly exercised its discretion when not admitting document D14 into the proceedings, nor requested that this document should be reintroduced into the proceedings, and that the Appellant never referred to this document in its written submissions concerning the question of inventive step.

2.8 Furthermore, independently of the fact that there is, in the Board's view, no justification for the very late introduction (i.e. nearly two years after the filing of the Statement of Grounds of Appeal) of this document, the Board, having considered the document D14 and the Opposition Division's decision that such document was not admissible, is satisfied that the Opposition Division did not misuse its discretion under Article 114(2) EPC when it elected to disregard document D14.

2.9 Consequently, the Board decided not to introduce document D14 into the proceedings (Art.114(2) EPC).

Main request

3. Wording of the claims

3.1 Claim 1 of the set of Claims on the basis of which the Opposition Division decided that the patent could be maintained differs from independent Claim 2 as originally filed in that it has been indicated:

(i) that the amount of residual metals in the polycarbonate obtained is 10 ppm or less in total of Fe, Cr and Mo, and 50 ppm or less in total of Ni and Cu;

(ii that the amount of oxygen in the reactor is 10 ppm or less; and

(iii) that the water content in the reactor is 102 ppm or less instead of 500 ppm or less in original Claim 2.

3.2 Amendments (i) and (ii) are supported by original Claims 3 and 8, respectively.

3.3 Concerning amendment (iii), while the value 102 ppm for the water content is disclosed in original Examples 1, 7, and 8, this is made in association with an oxygen content of 5 ppm (Examples 1 and 7) or of 3 ppm (Example 8).

3.4 Following the principles set out in decision T 201/83 (OJ EPO 1984, 481) the amendment of the water content in Claim 1 on the basis of this specific value (i.e. 102 ppm) disclosed in the examples would be allowable under Article 123(2) EPC, provided the skilled person could have readily recognised this value as not so closely associated with the other features of the examples as to determine the effect of that embodiment of the invention as a whole in a unique manner and to a significant degree.

3.5 In this connection the Board notes, however, that in view of the application as originally filed (page 7, lines 2 to 8), there is an interdependency between the water content and the oxygen content in order to reduce the elution of metals and the colouring of the resultant polycarbonate, so that the value 102 ppm indicated in these examples cannot be dissociated from the oxygen contents indicated therein.

3.6 It thus follows that amendment (iii) is not allowable under Article 123(2) EPC.

3.7 Consequently, since Claim 1 contravenes Article 123(2) EPC, the main request as a whole must be refused.

Auxiliary request

4. Articles 123(2) and 123(3) EPC.

4.1 Claim 1 of the main request differs from Claim 1 of the main request only in that the amount of water has been restricted to 100 ppm or less instead of 102 ppm or less.

4.2 Since the range 100 ppm or less is, in contrast to the range 102 ppm or less, supported by the application documents as originally filed (cf. original Claim 7), the Board comes to the conclusion that Claim 1 meets the requirements of Article 123(2) EPC.

4.3 The same conclusion is valid for Claims 2, 3 and 4 which find their support in original Claims 4, 5 and 9, respectively.

4.4 Since Claim 1 also corresponds to the combination of Claims 1, 2, and 6 as granted, it is evident that the requirements of Article 123(3) EPC are met by the auxiliary request.

5. Clarity

5.1 Objections of lack of clarity have been raised by the Appellant in view of the indications of the amount of oxygen (i.e. 10 ppm or less) and of the amount of water (i.e. 100 ppm or less) in Claim 1.

5.2 When amendments are made to a patent during an opposition, Article 102(3) EPC requires consideration as to whether the amendments introduce any contravention of any requirement of the Convention, including Article 84 EPC. Article 102(3) EPC, however, does not allow objections to be based upon Article 84 EPC, if such objections do not arise out of the amendments made (cf. also decision T 301/87; OJ EPO, 1990, 335; Headnote 1).

5.3 In the present case, the Board notes that the features of Claim 1 to which objections have been raised under Article 84 EPC by the Appellant (cf. points VIII.(i.1) to (i.2), above) were already present in granted Claims 1 and 6.

5.4 It thus follows that the raising of these objections under Article 84 EPC by the Appellant against Claim 1 cannot be allowed.

5.5 Since Claim 1 results from a combination of granted Claims 1, 2 and 6, and since Claims 2, 3 and 4 correspond to granted Claims 3, 4 and 7, respectively, the Board comes to the conclusion that the requirements of Article 84 EPC read in connection with Article 102(3) EPC are met by all the claims.

6. Novelty

Lack of novelty has been alleged by the Appellant against Claim 1 of the auxiliary request in view of Example 2 of D2, of Example 14 of D5 and of Example 1 of D8.

6.1 Document D2 relates to the preparation of high molecular weight thermoplastic polycarbonates by transesterification. According to D2, a dihydroxy compound is reacted with an organic carbonate in the presence of salts of quaternary ammonium, phosphonium or arsonium bases as transesterification catalysts. The polycarbonates obtained are said to be substantially free of discolouration and of thermal decomposition at elevated temperatures (column 2, lines 49-61).

In general, the polycarbonates can be prepared by the interaction between the reactants at a temperature of from 150°C to about 350°C or higher for times varying from 1 to 20 hours, preferably from 1 to 10 hours at atmospheric pressures, subatmospheric orsuperatmospheric pressures and it is preferred that the reaction be conducted in the presence of a non- oxidizing or inert atmosphere such as, hydrogen, nitrogen, krypton, neon to prevent undesirable oxidative effects, especially where extremely high reaction temperatures are employed (column 4, lines 32- 42).

6.2 More precisely, D2 discloses in its Example 2 the preparation of polycarbonate by transesterification in a stainless steel reactor. According to Example 2, 7000 parts of bisphenol A, 6700 parts of diphenyl carbonate and 0.3 part of tetraphenyl phosphonium tetraphenyl borohydride are melted under nitrogen, in a stainless steel autoclave. The resultant phenol is distilled off with stirring at pressure of 100 mm Hg at a temperature of 166°C. 5300 parts of phenol are distilled off after about 125 minutes. After 15 minutes the vacuum is increased to 0.5 mm Hg and the reaction completed at a temperature of between about 290 and 305°C. During this time, an additional 570 parts of phenol are distilled off. As indicated in Example 2, after 270 minutes, an almost colourless (emphasis by the Board) melt of polycarbonate is obtained.

6.3 Independently of the fact that the reaction is carried out under nitrogen does not preclude that some oxygen might nevertheless be present in the reactor, it is in any case evident that Example 2 does not explicitly disclose the amount of water present in the reactor during the preparation of the polycarbonate.

6.4 Nor could it be implicitly be deduced from the indication of the colouration of the polycarbonate obtained in this example that the water content was inevitably in the range required by Claim 1 of the auxiliary request for the following reasons:

(i) The rather indefinite and unquantified indication that the obtained polycarbonate is almost colourless does not allow a comparison with the yellowness index of the polycarbonates obtained in the examples of the patent in suit determined according to the Japanese standard JIS K7103-77, so that it cannot, hence, be concluded that the polycarbonate obtained in Example 2 has a comparable yellowness and, thus, the same metal content as those obtained according to the claimed process of the patent in suit; and

(ii) even if it could, the similarity of the obtained products in terms of yellowness and metal content would not inevitably imply that the polycarbonate of Example 2 of D2 had been prepared under conditions falling under the scope of Claim 1 in terms of water content. While, on the one hand, it is normally expected that similar processes lead to similar products, it cannot, on the other hand, be reciprocally deduced that similar products have been inevitably prepared by similar processes.

6.5 Since, as shown above, there is no clear and unmistakable disclosure in Example 2 that the water content in the reactor was in the range 100 ppm or less, the subject-matter of Claim 1 and by the same token that of dependent Claims 2 to 4 must be considered as novel over Example 2 of D2 (cf. also T 355/99 of 30 July 2002; not published in OJ EPO, Reasons point 2.2.4).

6.6 Document D5 relates to the production of polycarbonates by transesterification. According to D5, undesired colour formation, that is the discolouration of the polymers produced in the transesterification process, can be reduced or inhibited when the reaction is carried out in the presence of glass or of metals selected from tantalum, nickel or chromium, so that the reaction mixture contacts only surfaces of such metals or of glass (column 1, lines 40-47).

6.7 In Example 14 of D5 aromatic polycarbonates are prepared by a continuous process as follows: Into a glass liquid reaction vessel there is introduced 1 part of bisphenol A and 1 to 1.1 parts of diphenylcarbonate and 0.000026 to 0.000037 part of alkaline metal salts as a catalyst. The mixture is allowed to react at a temperature of 160°C to 200°C at atmospheric pressure for 2-4 hours. The prepolymer reaction is completed in two subsequent nickel clad reactors with increasing temperature and vacuum. The temperature is increased to a final 240°C and vacuum is increased to 7-20 mm Hg. The total residence time in the reactors is from 2-5 hours. The final polymerization is carried out in two stainless steel wiped film reactors with a final temperature of 260 to 280°C and a vacuum of 0.2-0.5 mm Hg. A product having an intrinsic viscosity of 0.5 to 0.7 and a Gardner Yellow Index of 3 to 4 is obtained.

6.8 From the disclosure of Example 14 of D5, it is immediately evident that this example indicates neither the amount of oxygen present in the nickel clad reactors and in the stainless steel reactors nor the amount of water present in these reactors.

6.9 Furthermore, although the polycarbonates obtained in this example exhibit a Gardner Yellow index of 3 to 4, there is no evidence that the Gardner Yellow index exactly corresponds to the yellowness index determined according to Japanese standard JIS K7103-77 specified in the patent in suit, so that it cannot hence be concluded that the polycarbonates obtained in Example 14 have a comparable yellowness or, therefore, the same metal content as those obtained by the claimed process of the patent in suit.

6.10 Even if the Gardner Yellow index would exactly correspond to the one determined according to this Japanese standard, the Board further notes that the process of Example 15 of D5, which is carried out as in Example 14 except that the reactors are stainless steel reaction vessels and that the product line is constructed out of stainless steel pipe, results in a product having a similar intrinsic viscosity but a very high Gardner yellow index of 22, i.e. in the range of the comparative examples of the patent in suit. Hence, this would imply that the amount of water and/or of oxygen in Examples 14 and 15 cannot be inside the ranges defined in Claim 1 of the patent in suit.

6.11 In any case, even if one would disregard Example 15 and further consider that the polycarbonates obtained in Example 14 have a similar yellow index and hence a similar metal content as those obtained according to the claimed process of the patent in suit, it could not be reciprocally deduced, for the same reasons indicated in paragraph 6.4 above, that the process of Example 14 has inevitably been carried out in presence of an amount of oxygen of 10 ppm or less and of an amount of water of 100 ppm or less.

6.12 Consequently, Example 14 of D5 cannot destroy the novelty of the subject-matter of Claims 1 to 4.

6.13 The reference made by the Appellant to Example 1 of D8 is even less relevant for the question of novelty. It is immediately evident that this example cannot be novelty destroying for the claimed subject-matter because the transesterification process disclosed therein is carried out in a glass reactor instead of a metallic reactor as required by Claim 1 of the patent in suit.

6.14 It thus follows from the above that the subject-matter of Claims 1 to 4 must be considered as novel over the prior art referred to by the Appellant (Article 54 EPC).

The patent in suit, the technical problem

7. The patent in suit is concerned with a process for making polycarbonate having good colour tone or transparency by transesterification in a metallic reaction vessel.

7.1 Such a process is known from document D5 which the Board, like the Opposition Division, regards as the closest state of the art.

7.2 As indicated above in paragraph 6.6, document D5 relates to the manufacture of polycarbonate by transesterification in reaction vessels made of nickel, chromium or tantalum or clad or lined with such metals. According to D5, a disadvantage of known transesterification processes is the tendency of undesirable colour or discolouration to form in the resulting polymers but, when the reaction is carried out in reactors or systems substantially totally made of such metals to provide the contact surface or in reactors or systems clad or lined with a layer of such metals to provide the contact surface, a clear product is obtained. As further indicated in D5, when titanium, vanadium, iron, tin, lead, zirconium, stainless steel and Group IIIA metals marked discolouration of the prepolymer occurs (column 1, line 64 to column 2, line 3).

7.3 Starting from D5 the technical problem might be seen in the provision of a process for the production of polycarbonate in order to overcome the problem of discolouration linked to the elution of metals from the reaction vessels (cf. also patent in suit page 2, lines 33 to 40).

7.4 The solution proposed according to Claim 1 of the patent in suit is to carry out the transesterification in a metallic reactor comprising at least one metal selected from Fe, Cr, Mo, Ni and Cu with a water content in the reactor of 100 ppm or less and an oxygen content in the reactor of 10 ppm or less.

7.5 In view of the comparison between Examples 2 to 6 and 9 and comparative Examples 1, 5, and 7 (all using a Ni lined autoclave) which shows that a polycarbonate having a low yellowness index is indeed obtained only when the oxygen and the water contents are in the claimed ranges, the Board is satisfied that the claimed measures provide an effective solution of the stated problem.

Inventive step

8. It remains to be decided whether the claimed subject- matter was obvious to a person skilled in the art in view of the prior art relied upon by the Appellant.

8.1 As stated in D5, the discolouration of polycarbonates made by transesterification was essentially related to the thermal instability of either partial esters of dihydric phenol still containing free hydroxyl group or to that of bisphenol A at high temperature (column 1, lines 19-37). According to D5 this discolouration is inhibited or reduced when carrying out the transesterification in presence of selective metals or glass, so that the reaction contacts only surface of such metals or glass. It is thus clear that, in D5, the problem of discolouration of the polycarbonate is not correlated with the elution of metal from the reaction vessel and it has been shown (cf. paragraph 7.5 above) that the limitation of the oxygen and water amounts in a Ni lined reactor indeed leads to a reduction of the yellow index of the obtained polycarbonate. Since document D5 is totally silent on the amounts of water and oxygen which should be present in the reactor during the transesterification, it is thus evident that D5 alone cannot suggest the solution proposed in the patent in suit.

8.2 While it is true that document D2 is concerned with a process for manufacturing polycarbonate having a good colour, it is essentially focussed on the choice of transesterification catalysts which do not promote discolouration of the polycarbonates even at elevated temperatures (column 2, lines 44 to 61). While it is further true that D2 discloses that the transesterification should be preferably carried out under a non-oxidizing atmosphere (column 4, lines 32 to 42) and that the water content of the polycarbonate should be below 0.01% (column 2, lines 1 to 12), this first point refers to the aim to avoid undesirable oxidative effects, and the second point is made in the context of the thermoplastic processing of the polycarbonate. It is therefore evident that there is no suggestion in D2 that by using a specific oxygen content (i.e. 10 ppm or less) and a specific water content (i.e. 100 ppm or less) in the reactor, this would lead to a reduction of eluted metals and hence to a reduced colouration of the obtained polycarbonates. Thus, D2 would not provide any hint to the solution of the technical problem.

8.3 Document D4 which relates to the preparation of aromatic polycarbonates by transesterification merely teaches that polycarbonates prepared from 4,4'- dihydroxy-diphenyl alkanes might be discoloured and insoluble if large quantities of catalyst are used, due to the thermal instability of the 4,4'-dihydroxy- diphenyl alkanes, even if care is taken to exclude atmospheric oxygen (page 45, line three from the bottom to page 46, line 5). Document D4 furthermore being totally silent on the influence of water content in the reaction vessel on the colouration of the prepared polycarbonates, the Board can only come to the conclusion that D4 is of no help for solving the technical problem.

8.4 Document D6 is directed to a process for making aromatic polycarbonate having a desired hydroxyl- terminal ratio and number-average molecular weight in high efficiency by prepolymerizing (A) a dihydroxydiaryl alkane alone or in combination with a dihydroxydiaryl compound and (B) a diaryl carbonate until the number-average molecular weight of the prepolymer reaches 1,000-10,000, determining the number-average molecular weight, the ratio of hydroxyl terminals and that of aryl carbonate terminals to total terminal groups, adding diaryl carbonate to the system when the hydroxyl terminal ratio is higher than the desired level or adding dihydroxydiaryl compound when the ratio is lower than the desired level and continuing the polymerization reaction as to obtain the polycarbonate having the desired OH content and molecular weight. Although D6 indicates that the contamination of oxygen and water should be minimized, it neither discloses threshold values for oxygen and water nor does it make a correlation between these amounts and the colouration of the polycarbonate obtained. Consequently, D6 cannot offer to the skilled person a hint to the solution of the technical problem.

8.5 Document D12 relates to the metal corrosion of chemical equipment and presents only the general principles of wet corrosion of iron in presence of water and oxygen. It is hence clear that D12 cannot suggest the threshold values of oxygen and water content in a reaction vessel for the manufacture of polycarbonate by transesterification in order to obtain a polycarbonate having a low metal content and hence a low yellowness index.

8.6 In this connection, the further argument of the Appellant, supported, in the Appellant's view, by a graph submitted at the oral proceedings showing a linear relationship between the metal content (Ni, Cu) of the obtained polycarbonates and the water content in the reaction vessel in the examples of the patent in suit, that the skilled person would have by routine experiments determined these threshold values, cannot alter the conclusions drawn in paragraphs 8.4 and 8.5 above,

(i) firstly, since this argument would be based on knowledge which has been derived from the patent in suit and which is not derivable either from D6 or from D12,

(ii) secondly, since none of the cited documents makes a link between the amount of metal eluted and the yellowness of the obtained polycarbonates,

and (iii) thirdly, since D12 is absolutely not concerned with the wet corrosion of Ni or Cu.

8.7 Thus, in view of the above, the Board comes to the conclusion that the subject-matter of Claim 1, and by the same token that of dependent Claims 2 to 4 does not arise in an obvious manner from the prior art relied upon by the Appellant (Article 56 EPC).

8.8 In the Board's view one would also have come to the same conclusion, if, for sake of argument, one would, as successively done by the Appellant, have considered either document D2 or document D4 as the closest state of the art and as requiring both to work under exclusion of oxygen in the transesterification reaction for obtaining almost colourless polycarbonates, since D2 and D4 are totally silent on the influence of the water amount in the reactor on the elution of metal from the reaction vessel, and since this missing element could not have been suggested, for the reasons indicated in paragraphs 8.1, 8.4, 8.5 and 8.6 above, by the documents D5, D6, and D12 used in combination with either D2 or D4.

9. Consequently the auxiliary request of the Respondent is allowable.