T 0268/03 () of 17.1.2006

European Case Law Identifier: ECLI:EP:BA:2006:T026803.20060117
Date of decision: 17 January 2006
Case number: T 0268/03
Application number: 96906548.1
IPC class: C07C 17/269
Language of proceedings: EN
Download and more information:
Decision text in EN (PDF, 84.035K)
Documentation of the appeal procedure can be found in the Register
Bibliographic information is available in: EN
Versions: Unpublished
Title of application: Synthesis of tetrafluoroethylene
Applicant name: E.I. DU PONT DE NEMOURS AND COMPANY
Opponent name: Dyneon GmbH & Co. KG
Board: 3.3.10

Headnote

-
Relevant legal provisions:
European Patent Convention 1973 Art 56
Keywords: Admissibility of late filed requests (yes)
Main and auxiliary request 1: inventive step (no) - obvious alternative
Auxiliary request 2: inventive step (yes) - improvement credible - fair comparative test
Catchwords:

-

Cited decisions:
T 0038/84
T 0197/86
Citing decisions:
-

Summary of Facts and Submissions

I. The mention of the grant of European patent 0 809 621, in respect of European patent application No. 96906548.1, which is based on the International application PCT/US96/02261 filed on 14 February 1996, was published on 4 August 1999.

II. Notice of opposition was filed in which revocation of the patent in its entirety was requested on the grounds of lack of novelty and inventive step (Article 100(a) EPC).

Inter alia, the following documents were cited during the opposition proceedings:

(1) DE-A-1 207 370,

(2) DE-A-1 170 935,

(3) DE-A-1 073 475 and

(4) M. Fedurtsa: "Mechanism of Thermal Decomposition of Octafluorocyclobutane", Ukrainskii Khimicheskii Zhurnal, (1987), Volume 53, pages 870 to 872.

III. In a decision issued in writing on 18 December 2002, the Opposition Division revoked the patent. The decision was based on a main request filed with a letter dated 9 March 2001 and an auxiliary request submitted during the oral proceedings before the Opposition Division.

The Opposition Division came to the conclusion that the subject-matter of claim 1 of the then pending main request was not novel with regard to the process disclosed in document (1).

Document (1) was considered as the closest prior art document for the subject matter of the independent claims 1 and 4 of the then pending auxiliary request. This document did not disclose the pressure range and the low conversion level specified in claim 1. However, document (1) taught that lower conversions resulted in less by-products. In addition, it could be derived from document (2) that the pressure range indicated in claim 1 was usual for this type of process. Hence, the subject matter of claim 1 of the then pending auxiliary request lacked inventive step.

The presence of an inert diluent as specified in claim 4 of the then pending auxiliary request was not disclosed in document (1). However, it was known from document (3) that yield and conversion could be improved in the presence of steam as diluent. Therefore, the subject matter of claim 4 of the then pending auxiliary request also lacked inventive step.

IV. On 24 February 2003, the Appellant (Proprietor of the patent in suit) lodged an appeal against the above decision. During the oral proceedings held before the Board on 17 January 2006 the Appellant defended the maintenance of the patent in suit on the basis of a main request and five auxiliary requests that were filed on 19 December 2005, superseding all previous requests.

The main request comprised a set of nine claims, independent claim 3 reading as follows:

"3. Process comprising pyrolyzing CF2HCl to obtain tetrafluoroethylene as desired reaction product and C4F8 as undesired reaction product, and further comprising co-feeding C4F8 along with said CF2HCl to the pyrolysis reaction in an amount effective to reduce the formation of C4F8 as undesired reaction product essentially without consuming C4F8 in the pyrolysis reaction, thereby increasing the yield of said tetrafluoroethylene reaction product, said pyrolysis reaction being carried out in the presence of diluent."

The auxiliary request 1 comprised a set of eight claims, independent claim 3 of that request differing from claim 3 according to the main request exclusively in the presence of steam as diluent, and in that the reaction is carried out at 750ºC to 850ºC.

The auxiliary request 2 comprised a set of two claims, the sole independent claim 1 reading as follows:

"1. Process comprising pyrolyzing CF2HCl to obtain tetrafluoroethylene as desired reaction product and C4F8 as undesired reaction product, and further comprising co-feeding C4F8 along with said CF2HCl to the pyrolysis reaction in an amount effective to reduce the formation of C4F8 as said undesired reaction product, essentially without consuming C4F8 in the pyrolysis reaction, thereby increasing the yield of said tetrafluoroethylene reaction product, said pyrolysis reaction being carried out under a total pressure of 0.8 to 1.2 atmosphere (89-121 kPa) to a conversion of CF2HCl of from 10% to 50%, wherein no inert diluent is used and wherein said C4F8 concentration is from 5% to 10% based on the combined weight of C4F8 and CF2HCl."

V. The Appellant's arguments can be summarised as follows:

The new requests were filed at the oral proceedings before the Board in response to formal objections concerning the amendments made in the previous requests. Since the Appellant should have the opportunity to overcome these objections, the new requests should be admitted into the proceedings.

Whereas document (3) should be considered as the closest prior art, document (1) could also be considered as an adequate starting point for the assessment of inventive step of the process according to claim 3 of the main request and the first auxiliary request. The problem solved by the claimed process with regard to the process disclosed in document (1) was to provide a further process for preparing TFE with high yields. The solution to that problem as reflected by claim 3 was to carry out the pyrolysis of CF2HCl in the presence of steam at a reaction temperature in the range of 750 to 850ºC. Document (1) could not suggest this solution since it did not consider the possibility of carrying out the reaction in the presence of steam. In addition the recycling of the mixture of by-products, as taught by document (1), could not be applied in the presence of steam since the skilled person expected under these reaction conditions a hydrolysis of the chlorinated by-products. Document (3) did not mention the recycling of C4F8. Furthermore, documents (1) and (3) could not be combined so as to arrive at the claimed process since both documents approached differently the problem underlying the patent in suit. Document (1) taught to improve the yield by pyrolysing under high conversion conditions and recycling the by-products which were also pyrolysed, whereas the process disclosed in document (3) was based on the findings that CF2HCl was surprisingly stable to hydrolysis under conditions of pyrolysis in the presence of water. The method of steam dilution was known to the authors of document (1) since document (3) was filed five years before document (1) by the same applicants. Yet, document (1) was entirely silent upon steam dilution. On the other side, document (3) neither considered the role of C4F8, nor did it mention the recycling of any heavy components.

Thus, the process according to claim 3 of the main request and of the first auxiliary request involved an inventive step.

The process of claim 1 according to the second auxiliary request required levels of conversion of 10 to 50%. In contrast thereto, document (1) which reflected the closest prior art, disclosed a method involving high conversions, i.e. 84%, for which high temperatures were required. Under these conditions a large portion of unwanted by-products was formed which could be cracked at high temperature if they were separated and re-fed to the pyrolysis reaction. In this context document (1) disclosed the recycling of 4% by weight of C4F8. With regard to this prior art, the problem underlying the present invention could be seen as providing a method for achieving higher yields of desirable end products. The solution provided by the patent in suit was characterized by conducting the pyrolysis under low conversions, i.e 10 to 50%, while co-feeding with the starting material 5 to 10% of C4F8. It could be deduced from the experimental data in the patent specification that when compared to a co-feeding of less than 5%, the co-feeding of 5 to 10% by weight of C4F8 reduced the amount of C4F8 produced and increased the yield in desirable end products. There was no indication in document (1) that C4F8 could have a significant role in the yield increase. In addition, document (1) was also completely silent with regard to the influence of the amount of C4F8 co-fed. None of the other cited prior art documents gave any indication in this respect.

Thus, the process according to claim 1 according to the second auxiliary request involved an inventive step.

VI. The Respondent's arguments can be summarised as follows:

Fresh requests were filed by the Appellant at a very late stage of the proceedings. In these requests, the expression "effective" present in claim 1 as granted was restored in the independent claims instead of the expression "controlled so as" present in the claims previously filed in the appeal proceedings. Since the expression "effective" had a broader meaning than the expression "controlled so as" this modification amounted to a broadening of the claims. However, the Appellant had given up broader claims containing the expression "effective" in the first instance proceedings and while filing the present appeal. Therefore, these requests should not be admitted into the proceedings.

The process according to claim 3 of the main and first auxiliary request only provided an alternative to that disclosed in document (1). This alternative was characterised by the fact that the pyrolysis reaction was carried out in the presence of steam as diluent. However, the use of steam as diluent in the pyrolysis of CF2HCl was known to the skilled person from document (3). Neither document (1), nor document (3) mentioned that the by-products generated by the pyrolysis of CF2CHCl would hydrolyse in the presence of steam. Thus, the alleged prejudice against using steam had not been proven.

Therefore, the process according to claim 3 of the main request and of the first auxiliary request did not involve an inventive step.

Document (1) could also be considered as the closest prior art document with regard to the process according to claim 1 of the second auxiliary request. Since a direct comparison between the claimed process and the closest prior art was missing, the technical problem could only be formulated so as to provide a further process for preparing TFE. The solution to that problem was to apply to the process known from document (1) conversions of 10 to 50% and adding more C4F8 in the feed. However, it was known to the skilled person that conversions of 10 to 50% were typical in the art and were linked with the achievement of higher yields of TFE. Furthermore, it could be expected that increasing the amount of C4F8 resulted in a higher production of TFE and HFP since it was known from document (4) that these products were generated by the thermal decomposition of C4F8.

Therefore, the process according to claim 1 of the second auxiliary request did not involve an inventive step.

VII. The Appellant requested that the decision under appeal be set aside and that the patent be maintained on the basis of the main request or subsidiarily on the basis of one of the auxiliary requests 1 to 5 filed during the oral proceedings before the Board.

The Respondent requested that the appeal be dismissed.

VIII. At the end of the oral proceedings the decision of the Board was announced.

Reasons for the Decision

1. The appeal is admissible.

2. Procedural matters: admissibility of the requests

In response to the objections raised during the oral proceedings with regard to the support in the application as filed of the amended expressions "controlled so as" and "in the presence of inert diluent" in the independent claims of the various requests filed in the written stage of the appeal proceedings, the Appellant submitted fresh requests containing only amendments prompted by the objections raised. The Respondent was not hindered in its argumentation with regard to novelty and inventive step by the amendments carried out in the claims of the new requests, since the amendments did not amount to create a fresh case necessitating a reconsideration of the objections and evidence brought forward so far by the Respondent against the patentability of the claimed subject matter. Consequently, the fresh requests are admitted into the proceedings.

The Respondent argued that the claims of the fresh requests were broader in scope than those pending before the Opposition Division and filed at the beginning of the appeal proceedings. The Appellant should not be allowed to broader the subject-matter claimed during appeal proceedings.

However, in accordance with the established jurisprudence of the Boards of Appeal of the EPO, in the present case where the Proprietor of the patent is appealing against the revocation of its patent, the Proprietor is entitled to revert to a more broadly worded version of the patent even if it had filed a restricted version before the opposition division and at the beginning of the appeal proceedings (Case Law of the Boards of Appeal of the EPO, 4th. Edition 2001, VI.I.3.1.2, (b), (bb) (1)). Thus, the limitation of claims during inter partes proceedings is regarded as a formulation attempt to respond to the objections raised rather than implying an irrevocable renunciation of subject-matter claimed. Therefore, in the present case the appealing Proprietor is not prevented from returning during appeal proceedings to a broader version of its claims.

Main and auxiliary request 1

2. The main and the auxiliary request 1 contain an independent claim 3 according to which the pyrolysis process is carried out in the presence of diluent. The process in accordance with claim 3 of the auxiliary request 1 is more precisely defined than in claim 3 of the main request, since the diluent is defined in the former as "steam" and a reaction temperature range is indicated (see point IV above). Thus, the subject-matter of claim 3 according to auxiliary request 1 is covered by that of claim 3 of the main request. In case the embodiment according to the auxiliary request 1 lacked patentability, such a line of requests would mandatorily result in the conclusion that the subject-matter of the preceding main request cannot be patentable either. Hence, in the present case it is appropriate to examine first whether the objections raised by the Respondent prejudice the patentability of the subject-matter of claim 3 of the auxiliary request 1.

Claim 3 of the auxiliary request 1

3. Amendments

Claim 3 is based on the combination of claim 1 and claim 7 of the application as filed. The reaction temperature of 750ºC to 850ºC indicated in claim 3 is disclosed on page 4, line 26 of the application as filed.

It is not contested that when compared to the patent as granted, claim 3 of the auxiliary request 1 does not extend the protection conferred thereby.

Consequently, the amended claim 3 fulfils the requirements of Article 123(2) and (3) EPC.

4. Novelty

The Respondent did not raise any objection with regard to the novelty of the subject matter of claim 3 of the auxiliary request 1. The Board on its own does not see any reason to take a different view. Hence, it is unnecessary to go into more details in this respect.

5. Inventive step

5.1 For the assessment of inventive step in accordance with the "problem-solution approach", it is necessary to establish the closest prior art in order to determine in the light thereof the technical problem which the invention addresses and solves. The "closest prior art" is normally represented by a prior art document disclosing subject-matter aiming at the same objective as the claimed invention and having the most relevant technical features in common (Case Law of the Boards of Appeal of the EPO, 4th. Edition 2001, I.D.3.1).

5.2 The patent in suit is directed to a process for pyrolysing CF2HCl to obtain tetrafluoroethylene (TFE) comprising co-feeding C4F8 along with said CF2HCl to the pyrolysis reaction.

5.3 The preparation of TFE by pyrolysis of CF2HCl involving the co-feeding C4F8 along with said CF2HCl to the pyrolysis reaction belongs to the state of the art as evidenced by document (1).

Document (1) discloses a process for the manufacture of TFE, which comprises pyrolysing CF2HCl and after separation of the TFE and lower boiling materials obtained, mixing the by-products formed which have a higher boiling point than TFE with fresh CF2HCl and subjecting the mixture to pyrolysis (claims 1 and 4).

According to the sole example of document (1) a mixture comprising CF2HCl and 4.5 kg C4F8 was subjected per hour to a pyrolysis in a platinum tube heated to 940ºC. After leaving the reaction tube, a mixture containing TFE, perfluoropropylene (HFP) and 5.0 kg C4F8 was obtained per hour. The yield of TFE was 94% at a conversion rate of 84%. When, under the same reaction conditions, only the unreacted CF2CHCl was subjected to further pyrolysis, the yield was merely 72% (example, columns 3 and 4).

Thus, document (1) discloses a process for pyrolysing CF2CHCl to produce TFE comprising co-feeding C4F8. In addition, the process is operated without consuming C4F8, since 4.5 kg thereof are co-fed into the reactor whereas 5.0 kg thereof leave the reaction tube.

Neither party contested that document (3), which was addressed by the Appellant as a possible starting point, discloses a process having less features in common with the claimed process than the process according to document (1). In particular the most relevant feature of the claimed process, namely the co-feeding of C4F8 without its consumption, is not disclosed in document (3).

Therefore, the Board considers in agreement with the Appellant and the Respondent, that document (1) represents the closest prior art and starting point in the assessment of inventive step.

5.4 Having regard to this prior art, both parties submitted that the technical problem underlying the subject-matter of the patent in suit as defined in claim 3 of the auxiliary request 1 was to provide a further process for preparing TFE in high yields.

5.5 The solution to this problem proposed by the patent in suit is the process according to claim 3 of the auxiliary request 1, which is characterized by the features that the pyrolysis reaction is carried out at a temperature of 750 to 850ºC in the presence of steam as diluent.

5.6 The Respondent never disputed that the claimed process produces TFE in high yields and the Board is not aware of any reason for challenging that finding. The specification of the patent in suit reveals in paragraph [0012] and in the examples given the successful use of steam, on the one hand, and of the temperature range claimed, on the other.

5.7 It remains to be decided whether or not the proposed solution to that objective technical problem, namely the process according to claim 3 of the auxiliary request 1, is obvious in view of the state of the art.

5.7.1 The skilled person looking for an alternative to the process disclosed in document (1) would turn its attention to document (3) which belongs to the same technical field and addresses the problem underlying the patent in suit of preparing TFE. This latter document discloses a process for the manufacture of TFE by the pyrolysis of CF2HCl, wherein the pyrolysis is operated in the presence of superheated steam. In example 1 of document (3) the pyrolysis is carried out in the presence of steam at a reaction temperature of 840ºC (column 4, lines 30 to 33). In addition document (3) teaches that the conversion is increased to about 65 to 70 % and a yield of 90 to 94 % TFE is achieved when pyrolysing a mixture of CF2HCl and steam (column 1, lines 39 to 46). Thus, document (3) clearly teaches that the pyrolysis of CF2HCl can be operated in the presence of steam at 840ºC and results in high yield.

The Board concludes from the above that document (3) gives a clear incentive on how to solve the technical problem underlying the patent in suit of providing a further process for preparing TFE with high yields, namely by operating the process known from the closest prior art document (1) in the presence of steam as diluent at a temperature of 840ºC, i.e. within the claimed range, thereby arriving at the solution proposed by the patent in suit.

5.7.2 The Appellant argued in support of obviousness that the skilled person expected under these reaction conditions a hydrolysis of the chlorinated products thereby dissuading him from applying the teaching of document (3) in the present case. However, according to document (3), CF2HCl was not hydrolyzed by steam under these reaction conditions (column 2, lines 45 to 49). Thus, even if the skilled person would have postulated the hydrolysis of CF2HCl or of the fluorinated by-products in the presence of steam, as argued by the Appellant, document (3) teaches that this side reaction does not take place. In addition, since document (3) gives a strong hint to use steam, the skilled person would not have been discouraged from following this clear teaching. On the contrary, in view of the incentive from document (3) to use steam, the skilled person was not deterred from applying the teaching of that document and would try to operate the reaction in the presence of steam with a reasonable expectation of success. This is confirmed in the specification of the patent in suit which acknowledges that steam had been used in the prior art in the pyrolysis of CF2HCl (page 2, lines 21 to 23).

Thus, in the absence of any substantiating facts and corroborating evidence, the Appellant arguments are mere speculations that the Board does not find convincing.

5.8 For these reasons, the subject-matter of claim 3 according to the auxiliary request 1 turns out to be merely the result of an obvious combination of the teaching of documents (1) and (3) and thus lacks the required inventive ingenuity (Article 56 EPC).

Consequently, the auxiliary request 1 must be refused.

Claim 3 of the main request

6. Claim 3 of the main request covers the subject-matter of claim 3 according to the auxiliary request 1. Since the Board arrived at a negative conclusion with regard to inventive step of the process as defined in claim 3 of the auxiliary request 1, the process according to claim 3 of the main request necessarily lacks inventive step for the same reasons (see point 5 above).

Therefore, the main request must also be refused.

Auxiliary request 2

7. Amendments

Claim 1 according to the auxiliary request 2 is based on the combination of claims 1, 3, 4 and 5 of the application as filed. Dependent claim 2 corresponds to claim 6 of the application as filed.

It is not contested that when compared to the patent as granted, claim 1 of the auxiliary request 2 does not extend the protection conferred thereby.

Consequently, the claims fulfil the requirements of Article 123(2) and (3) EPC.

8. Novelty

The novelty of the subject matter of claim 1 of the auxiliary request 2 has not been contested. The Board on its own does not see any reason to take a different view. Hence, it is unnecessary to go into more details in this respect.

9. Inventive step

9.1 Both parties considered that document (1) also represents the closest prior art and starting point for the assessment of inventive step for the process according to claim 1 of the auxiliary request 2. The Board on its own does not see any reason to take a different view on the grounds given in point 5.3 above.

The mixture subjected to pyrolysis according to the sole example of document (1) contains 4% by weight of C4F8 based on the combined weight of C4F8 and CF2HCl (see Appellant's statement of grounds, page 10, paragraph 1) and the conversion rate of CF2HCl was 84% (further details in point 5.3 above).

9.2 Having regard to this prior art, the Appellant submitted that the technical problem underlying the subject-matter of the patent in suit as defined in claim 1 of the auxiliary request 2 was to provide a process achieving higher yields of TFE and of the useful by-product HFP.

9.3 As a solution to this problem the patent in suit proposes the process according to claim 1 of the auxiliary request 2, which is characterized by co-feeding C4F8 in a concentration from 5 to 10 % by weight based on the combined weight of C4F8 and CF2HCl and by carrying out the process so as to achieve a conversion rate of CF2HCl of from 10% to 50%.

9.4 The parties were divided on the matter as to whether or not the evidence presented, namely the examples of the patent specification, convincingly showed that the technical problem defined herein above (see point 9.2) was successfully solved by the claimed process. In this context the Respondent argued that no example truly reflected the process disclosed in document (1) and that, consequently no improvement with regard to the closest prior art could be identified.

The examples in the specification of the patent in suit, while keeping the conversion rate constant and within the claimed range, were carried out by modifying the concentration of C4F8 in the feed (tables 1, 2 and 3 on page 5). Some of the examples show a concentration of C4F8 in the feed within the claimed range of from 5 to 10 % by weight. This finding applies to the examples indicated in the last line of each of the tables 1 and 2 and to the examples in the second to the fourth line of table 3. The other examples of those tables, which involve a feed containing less than 5% by weight of C4F8, thus, are not in accordance with the invention. Nevertheless, these examples serve for comparative purposes since they truly reflect the impact of an essential technical feature distinguishing the claimed process from the closest prior art, namely a concentration of from 5 to 10 % by weight of C4F8 in the feed versus a lower concentration in the prior art. Thus, the comparison provided by the different examples of the patent in suit is fair and to be taken into consideration when assessing inventive step (see decision T 197/86, OJ EPO 1989, 371).

The experimental data presented in the tables 1 to 3 of the patent in suit show that the yield in TFE and HFP is higher when the concentration of C4F8 in the feed is in accordance with the invention. According to table 1 the yield of TFE and HFP is 96,5% when using a concentration of 5,08% C4F8 in the feed, i.e. within the claimed range, whereas the yield is 91,7 to 95,8% when the concentration is below the claimed threshold. Corresponding results are given in table 2 which reports a yield of 96,1% when operating the process within the claimed concentration range compared to a yield of 93,2 to 94,6% when operating it below that range, and in table 3 reporting a yield of 95,3 to 95,9% compared to 94,5%.

Although, the increase in yield observed when the feed contains above 5% by weight of C4F8 is small, it was not contested that this result is significant and substantial on an industrial scale (see decision T 38/84, OJ EPO 1984, 368).

For theses reasons, the Board is satisfied that the technical problem underlying the patent in suit has been successfully solved.

9.5 It remains to be decided whether or not the proposed solution to that objective technical problem is obvious in view of the state of the art.

9.5.1 Document (1) makes no mention of any effect linked to the concentration of C4F8 in the inlet feed. In addition, since document (1) illustrates only a process in which the concentration of C4F8 in the feed was 4% by weight, the skilled person cannot derive from that document any teaching with regard to the effect of the concentration of C4F8 on the yield of the desired products. Thus, the skilled person cannot get any hint from document (1) on its own, that an improvement of the yield could be achieved by increasing the concentration of C4F8 in the feed to a range from 5% to 10% by weight.

9.5.2 Document (3) is directed to a process for pyrolysing CF2HCl to TFE, but it does not describe to operate the pyrolysis by co-feeding C4F8 along with said CF2HCl to the pyrolysis reaction. Consequently, document (3) cannot point to the claimed solution which comprises co-feeding C4F8 within the particular concentration range claimed.

9.5.3 The Respondent argued that the skilled person was expecting that the co-feeding of C4F8 would result in an increase of the yield of TFE and HFP since it was known from document (4) that C4F8 was transformed into these products by thermal decomposition.

Document (4) relates to the mechanism of the decomposition of C4F8. However, this document does not address the decomposition of C4F8 in the context of the pyrolysis of CF2HCl. In addition, the process according to the patent in suit is operated essentially without consuming C4F8 (see claim 1) whereas document (4) relates to the decomposition of C4F8, said decomposition involving obviously a consumption of C4F8. Thus, that document is silent on the matter of increasing the yield of TFE and HPE in the pyrolysis of CF2HCl with the consequence that the Respondent's allegation is not supported by the facts. Any explanation now offered by the Respondent of the effect achieved by the claimed process is mere hindsight since the skilled person could not get any incentive from document (4) to carry out the pyrolysis of CF2HCl by co-feeding C4F8 in a particular concentration in order to improve the yield of TFE and HFP, essentially without consuming C4F8.

Consequently, document (4) on its own or in combination with document (1), does not point to the claimed solution to the technical problem defined herein above.

9.6 Therefore, the process according to claim 1 of the auxiliary request 2, and for the same reason, that according to dependent claim 2 involve an inventive step within the meaning of Articles 52(1) and 56 EPC.

ORDER

For these reasons it is decided that:

1. The decision under appeal is set aside.

2. The case is remitted to the first instance with the order to maintain the patent on the basis of claims 1 and 2 of the auxiliary request 2 filed at the oral proceedings before the Board and a description yet to be adapted.

Quick Navigation