T 0540/01 (Butyleneglycol/DAICEL) 05-11-2003

1. The appeals are admissible.

2. Late filed evidence (Article 114(2) EPC)

Documents (4) to (6) are new evidence cited for the first time in the Appellant II's Statement of the Grounds of Appeal. The Appellant I objected to admitting these documents into the proceedings for the reason that they were late filed while providing detailed comments thereon in his letter of reply dated 8. February 2002.

Those documents were prompted by and intended to overcome the Opposition Division's essential argument set out in the decision under appeal that the specific requirements of the distillation, i.e. the lines (1-4- 5) and (1-4-6) and the decanter (1-4-4), supported the inventive step of the claimed invention. Furthermore documents (4) to (6) are standard textbooks reflecting the common technical knowledge of the skilled person.

The submission by an Appellant of fresh documents in the Statement of the Grounds of Appeal to overturn the appealed decision is to be considered as a normal action of a losing party (see decision T 1072/98, point 2.3 of the reasons, not published in OJ EPO). Thus, in the present case, the fresh documents (4) to (6) submitted with the Appellant II's Statement of the Grounds of Appeal are not filed late in the sense of Article 114(2) EPC. This finding is underpinned by the fact that those documents address common general knowledge thereby causing no undue delay or burden to the appeal proceedings.

Therefore, documents (4) to (6) are to be taken into consideration in the appeal proceedings.

3. Amendments (Article 123(2) and (3) EPC)

The amendment to claim 1 as granted of decomposing aldoxane, contained in the crude reaction solution, in an aldoxane decomposition column (1-3) finds support on page 6, lines 27 and 28 and on page 7, lines 22 and 23 of the application as filed. Performing a distillation of the mixture of acetaldehyde, water and crotonaldehyde to recover separately acetaldehyde and crotonaldehyde is based on original Figure 1, streams (F) and (E). The specific installations to perform that distillation indicated in the characterising portion of claim 1 is found on page 7, lines 8 to 10 of the application as filed. The particular operation of the condenser (1-4-3) and the decanter (1-4-4) is supported by original page 9, lines 4 to 15. Thus, all the amendments made to claim 1 as granted comply with the requirements of Article 123(2) EPC.

Those amendments of claim 1 as granted bring about a restriction of the scope of that claim, and therefore of the protection conferred thereby, which is in keeping with the requirements of Article 123(3) EPC.

4. Novelty

The novelty of the patent in suit was not at issue in this appeal. Although raised as a ground for opposition by him, the Appellant II concurred in appeal proceedings with the finding of the Opposition Division rejecting this ground. Nor does the Board see any reason to take a different view. Hence, it is unnecessary to go into more detail in this respect.

5. Inventive step

5.1. According to the established jurisprudence of the Boards of Appeal it is necessary, in order to assess inventive step, to establish the closest state of the art, to determine in the light thereof the technical problem which the invention addresses and successfully solves, and to examine the obviousness of the claimed solution to this problem in view of the state of the art. This "problem-solution approach" ensures assessing inventive step on an objective basis and avoids an ex post facto analysis.

5.2. Claim 1 of the patent in suit is directed to a process for preparing 1,3-butylene glycol starting with an aldol condensation of acetaldehyde to yield the intermediate aldoxane, decomposing that intermediate to paraldol which is then hydrogenated. The documents JP-A-212384/1987 and JP-A- 246529/1987 which are cited and acknowledged in the specification of the patent in suit on page 2, lines 41 to 52 as the closest prior art, refer both to the same type of preparation process. Uncontested by the Appellant II, they describe a preparation process wherein aldoxane resulting from an aldol condensation is thermally decomposed yielding a crude reaction solution primarily consisting of paraldol while distilling off acetaldehyde, followed by catalytically reducing (with hydrogen) paraldol to prepare 1,3-butylene glycol. The unreacted acetaldehyde, together with crotonaldehyde generated in the thermal decomposition step, is recirculated to the aldol condensation.

5.3. Those documents, though having not been expressly addressed in the notice of opposition, nevertheless form part of the opposition appeal proceedings since any document indicated in a contested patent as closest prior art is automatically included therein (see decision T 536/88, OJ EPO 1992, 638, point 2.1 of the reasons). Where the patent in suit indicates a particular piece of prior art as being closest to the claimed invention and the starting point for determining the problem underlying the patent in suit, then the Board should adopt this as the starting point for the purpose of a problem-solution analysis unless it turns out that there is closer state of the art of greater technical relevance (see e.g. decisions T 800/91, point 6 of the reasons; T 68/95, point 5.1 of the reasons).

Thus, the Board considers, in agreement with the Appellant I that in the present case the process for preparing 1,3-butylene glycol described in both documents specified above represents the closest state of the art and, hence, takes it as the starting point when assessing inventive step.

5.4. The Appellant II, while not disputing the above findings, addressed also document (1) as representing the closest prior art. That document is directed to a process for preparing 1,3- butylene glycol starting with an aldol condensation of acetaldehyde yielding acetaldol which is steam stripped to remove unreacted acetaldehyde, and then hydrogenating the stripped acetaldol. Therefore document (1) neither specifies that process to proceed via the intermediate aldoxane and, thus, to thermally decompose aldoxane in a decomposition column, nor to hydrogenate paraldol. For those reasons the process disclosed in document (1) is further away from the claimed invention than the documents addressed in point 5.2 above.

The Appellant II alleged that the process of document (1) necessarily and implicitly comprised the unspecified steps and features, namely the formation of aldoxane, its thermal decomposition in a decomposition column and the hydrogenation of paraldol. Aldoxane was formed automatically and the steam stripping corresponded to a thermal decomposition of aldoxane yielding what was described as paraldol in the claimed invention. However, the Appellant II, when offering his interpretation of document (1), has merely speculated without providing substantiating facts or corroborating evidence. The burden of proving the facts it alleges lies with the party invoking these facts. If a party, whose arguments rest on these alleged facts, is unable to discharge its onus of proof, it loses thereby. In the absence of any pertinent evidence presented by him, the Appellant II has not discharged the burden of proof which is upon him, with the consequence that the Board cannot accept his view.

5.5. The drawbacks of the conventional process for preparing 1,3-butylene glycol according to the closest prior art (cf. point 5.2 above) lie in recirculating crotonaldehyde generated in the thermal decomposition step of aldoxane to the aldol condensation together with unreacted acetaldehyde, unpreferably resulting in the generation of various impure components by a reaction with acetaldehyde in the aldol condensation step (patent specification page 2, lines 49 to 52).

Thus, the technical problem underlying the claimed invention as indicated in the specification of the patent in suit on page 2, lines 4 to 6 and page 3, lines 19 to 20, and as submitted by the Appellant I at the oral proceedings before the Board, consists in providing an improved process for preparing 1,3- butylene glycol in which the generation of by-products is decreased resulting in obtaining an odorless 1,3- butylene glycol at higher yields.

5.6. As the solution to this problem, the patent in suit proposes a process for preparing 1,3-butylene glycol as defined in claim 1 which is characterised by step (d), i.e. by performing a distillation of crude acetaldehyde in an acetaldehyde-refining column (1-4) including a reboiler (1-4- 1), a condenser (1-4-2), and a condenser (1-4-3) and a decanter (1-4-4) between a discharging line (1-4-5) and a recirculating line (1-4-6), wherein a distillate discharged from the discharging line (1-4-5) is condensed in the condenser (1-4-3), and then a resulting condensate is separated into two layers of liquid in the decanter (1-4-4); crotonaldehyde is primarily included in the upper layer of liquid [stream (E)] of the two layers of liquid, followed by supplying to a recovery step or a waste line, and resulting in being removed from acetaldehyde to be recirculated to the aldol condensation step (a); and the lower layer of liquid [stream (D)] of the two layers of liquid primarily includes from 5 to 15 % by weight of crotonaldehyde, and from 85 to 95 % by weight of water, both of which are recirculated to the side portion of the acetaldehyde-refining column (1-4) through a recirculating line (1-4-6) in order to effectively recover crotonaldehyde, and which is further characterised by step (e), namely by recirculating the refined acetaldehyde having a content of less than 0.1% crotonaldehyde to the aldol condensation step.

5.7. The Appellant I and the Appellant II were divided on the matter of whether or not the evidence presented in the specification of the patent in suit convincingly demonstrates that the proposed solution successfully solves the problem underlying the invention of preparing odorless 1,3-butylene glycol at higher yields.

The Appellant I relied on the experimental report comprised in the specification of the patent in suit demonstrating that the yield of 1,3-butylene glycol in the process according to the invention, i.e. examples 1 and 2, was improved vis-à-vis the process according to the closest prior documents (cf. point 5.2 above), i.e. comparative examples 1 and 2. In examples 1 and 2 the yield of odorless 1,3-butylene glycol is 76,6% and 78%, respectively, while in comparative examples 1 and 2 the yield thereof is lower, namely 59,6% and 70%, respectively. That experimental report compares the yield of two processes for obtaining odorless 1,3-butylene glycol both differing from each other exclusively in the presence or absence of steps (d) and (e) as defined in claim 1. Therefore, the comparison of the experimental data for examples 1 and 2 and comparative examples 1 and 2 indicated in that test report truly reflects the impact of the process modifications distinguishing the solution suggested by the patent in suit from the closest prior documents. This specific comparison is, thus, a fair basis for the assessment of inventive step. For these reasons, the Board is satisfied that the problem underlying the patent in suit has been successfully solved.

The Appellant II addressed example 7 and comparative example 2 in order to challenge the successful solution of the problem underlying the invention. He submitted that the content of crotonaldehyde in the crude solution discharged from the bottom of the aldoxane decomposition column [stream (B)] was higher in example 7. according to the invention, namely 2,3%, than in comparative example 2 according to the prior art, namely 1,7%. However, the problem underlying the patent in suit consists in obtaining odorless 1,3-butylene glycol in higher yields (cf. point 5.5 above), not in reducing the content of crotonaldehyde in a particular intermediate process stream, e.g. stream (B). Furthermore the operation conditions in example 7 and comparative example 2 are substantially different, e.g. the reaction temperature / the retention time being 117°C / 13 min and 75°C / 86 min, respectively, thereby making any direct comparison between both examples void.

5.8. Finally, it remains to be decided whether or not the proposed solution to the problem underlying the patent in suit is obvious in view of the cited state of the art.

5.8.1. The closest prior art documents (see point 5.2 above) to start from teach a process wherein unreacted acetaldehyde is recirculated to the aldol condensation together with crotonaldehyde. They do not give any incentive to modify that process by steps (d) and (e) as defined in claim 1 and to increase thereby the yield. Thus, those documents, on their own, do not render obvious the solution proposed by the claimed invention

5.8.2. Though document (1) is directed to a process for preparing 1,3-butylene glycol and describes inter alia the distillation of a crude mixture of acetaldehyde and crotonaldehyde to recover acetaldehyde for further use (page 2, lines 75 to 81), that document does not address the technical problem underlying the patent in suit of obtaining odorless 1,3-butylenen glycol in higher yields (see point 5.5 above). For this simple reason document (1) cannot give any hint on how to solve that technical problem since a skilled person would not take the teaching of that document into consideration when looking for a solution to the problem underlying the invention.

Furthermore, the skilled person would not in any event arrive at the process according to claim 1 when combining the teaching of the closest prior documents (cf. point 5.2 above) with that of document (1). Document (1) describes a mere distillation of the crude mixture of acetaldehyde and crotonaldehyde to recover acetaldehyde whereas the process of the invention requires in characterising step (d) inter alia the additional use of a decanter which is operated following particular process features, and in characterising step (e) a maximum content of 0.1% crotonaldehyde in the refined acetaldehyde. Thus, the skilled person when combining the teachings of the closest prior documents and of document (1) would thereby not arrive at the claimed process. Therefore, the Appellant II's obviousness objection based on document (1) cannot convince the Board.

5.8.3. The Appellant II also addressed documents (4) and (6) reflecting common general knowledge and describing standard features in the field of separation techniques thereby implying a less ambitious problem of the invention, namely to provide merely an alternative process for preparing 1,3- butylene glycol. However, the technical problem underlying the patent in suit is different and consists in the provision of a process for preparing odorless 1,3-butylene glycol in higher yields (see point 5.5 above). Both documents do not address this technical problem and for that very reason they cannot give any hint on how to solve it; therefore a skilled person would not take the teaching of those documents into consideration when looking for a solution to the problem underlying the invention.

Furthermore, the combination of the teaching of documents (4) or (6) with that of the closest prior documents (cf. point 5.2 above) would not result in the process as defined in claim 1. Document (4) describes a series of stills for refining crotonaldehyde whereas the process of the invention requires in step (d) the additional use of a particularly operated decanter and in step (e) a maximum content of 0.1% crotonaldehyde in the refined acetaldehyde. Document (6) is directed to distillation operations in general describing inter alia a removal of water from a side stream of a hydrocarbon or fusel oil distillation column by means of a decanter. However, that document is silent about any particular operation of the decanter as required in the process of claim 1, namely of separating in a decanter a specific side stream into two layers of liquid, the upper layer being crotonaldehyde and the lower layer primarily including from 5 to 15% by weight of crotonaldehyde, and from 85 to 95% by weight of water, both of which being recirculated to the side portion of the acetaldehyde-refining column, and it is silent about a maximum content of 0.1% crotonaldehyde in the refined acetaldehyde.

Hence, the skilled person when combining the teaching of the closest prior documents with that of document (4) or (6) would thereby not arrive at the claimed process. Therefore, the Appellant II's obviousness objection based on those documents is devoid of merit.

5.8.4. To summarize, in the Board's judgment, none of the documents addressed above renders the claimed invention obvious, either taken alone or in combination.

The Appellant II not relying on further prior art in order to support his objection of obviousness, the Board is satisfied that none of the other documents in the proceedings renders the proposed solution obvious.

5.9. For these reasons the Board concludes that the subject- matter of the sole claim involves an inventive step within the meaning of Articles 52(1) and 56 EPC.