T 0568/11 - Comparative examples

Key points

• A useful reminder of how to do comparative experiments before the EPO: what if not only the distinguishing feature is modified, but also some other features.
• " According to the established jurisprudence of the boards of appeal, each of the parties to the proceedings carries the burden of proof for the facts it alleges. As there is no apparent and compelling technical reason why the above mentioned additional differences between the compositions to be compared according to the respondent's tests would have no influence on the properties of the composition, let alone any supporting evidence in this respect, the respondent's argument concerning the significance of the comparisons offered is merely speculative and cannot be retained. Accordingly, the experimental tests relied on by the respondent cannot demonstrate a causal link between the [the distinguishing feature], and the purported improved chemical resistance and improved printability. Therefore, the present decision does not deviate from the findings in decision T 197/86, relied upon by the respondent, according to which the nature of the comparison with the closest state of the art in comparative tests submitted to demonstrate an inventive step on the basis of an improved effect must be such that the effect is convincingly shown to have its origin in the distinguishing feature of the invention."  

 EPO T 0568/11 -  link

Reasons for the Decision

3.2 Problem and solution

3.2.1 Having regard to the disclosure of either D1 or D3, the respondent submitted that the technical problem solved by the subject-matter of claim 1 of the patent in suit was the provision of aqueous compositions which lead to coatings having improved chemical resistance and inks having improved printability. That problem is meant to be solved by the use of a bulk polymerization for preparing the vinyl oligomer A instead of an emulsion polymerization.

3.2.2 As to whether evidence has been provided that the claimed subject-matter provides a successful solution to the problem mentioned above, the respondent referred to three comparative tests of the patent in suit, namely comparisons between comparative examples 7, 9 and 11 vs. examples 6, 8 and 10, respectively (paragraphs [127]-[135]). According to the established case law of the Boards of Appeal, in the case where comparative tests are chosen to demonstrate an inventive step on the basis of an improved effect, the nature of the comparison with the closest state of the art must be such that the alleged advantage or effect is convincingly shown to have its origin in the feature distinguishing the invention from the closest state of the art, in the present case the change of morphology of vinyl oligomer A resulting from the use of bulk instead of emulsion polymerization.

3.2.3 The comparative tests submitted by the respondent can be analysed as follows:

(a) The aqueous composition prepared in comparative example 7 differs inter alia from the one prepared in example 6 in that a vinyl oligomer (CVO8) prepared by emulsion polymerisation is used instead of a vinyl oligomer (VO6) prepared by bulk polymerisation. However, the other characteristics of the aqueous compositions compared cannot be considered to have been kept constant having regard to the use of 3-mercaptopropionic acid (a chain transfer agent, see paragraph [55]) and of large amounts of ammonia during preparation of CVO8 (paragraph [74]). In respect of the chain transfer agent, the respondent did not dispute that the amount of hydrophilic groups in the oligomer would be modified consequently and its argument according to which such a compound had to be used in the emulsion polymerisation is not convincing since there exist other means, less invasive, to regulate a polymer's molecular weight. As to ammonia, if it can be deduced that VO6 has been neutralised since it is in alkaline form (two first lines of paragraph [86]), the nature of the base used for neutralisation is unknown. In addition, the step of emulsion polymerisation for producing the vinyl polymer B in the presence of the vinyl oligomer A is also different in comparative example 7 as the amount of solids content of the oligomer used (17.4% for VO6 and 24.8% for CVO8) and of the resultant composition (27.1% for example 6 versus 36.8% for comparative example 7) is not the same (paragraphs [86]-[90]).

[...]

3.2.4 Summing up, the comparative tests relied on by the respondent are not based on compositions which differ only in the feature meant to distinguish the claimed subject-matter from the closest prior art. The respondent nevertheless argued that the additional differences between the compositions to be compared were so minimal that they would have no influence on the properties of the composition, and that it was up to the appellant to demonstrate the contrary.

3.2.5 According to the established jurisprudence of the boards of appeal, each of the parties to the proceedings carries the burden of proof for the facts it alleges. As there is no apparent and compelling technical reason why the above mentioned additional differences between the compositions to be compared according to the respondent's tests would have no influence on the properties of the composition, let alone any supporting evidence in this respect, the respondent's argument concerning the significance of the comparisons offered is merely speculative and cannot be retained. Accordingly, the experimental tests relied on by the respondent cannot demonstrate a causal link between the change of structure of vinyl oligomer A, which results from its preparation by bulk polymerisation, instead of emulsion polymerization, and the purported improved chemical resistance and improved printability. Therefore, the present decision does not deviate from the findings in decision T 197/86, relied upon by the respondent, according to which the nature of the comparison with the closest state of the art in comparative tests submitted to demonstrate an inventive step on the basis of an improved effect must be such that the effect is convincingly shown to have its origin in the distinguishing feature of the invention.

3.2.6 Since the respondent did not present corroborating evidence or an explanation making it credible that the purported technical benefit is achieved, that alleged advantage of the claimed aqueous compositions over the closest prior art cannot be taken into account.

3.2.7 Accordingly, the technical problem solved over the closest prior art by the claimed subject-matter as proposed by the respondent cannot be accepted and needs to be reformulated. In view of the above, the technical problem effectively solved (objective problem) can only be considered to lie in the provision of further aqueous coating or ink compositions.

3.3 Obviousness

3.3.1 It remains to be decided whether or not the proposed solution to the objective problem underlying the patent in suit is obvious in view of the state of the art.

3.3.2 It is not disputed that bulk polymerisation of vinyl polymers is a conventional technique in the art, as indicated in paragraph [48] of the patent in suit and confirmed in D6 (page 174, point 6.3.1) and D5 (column 2, lines 11-13). This technique as shown in D5 is in particular known to be employed in the same technical field of aqueous coating compositions for metal and glass surfaces, prepared via a two stages process, in which a conventional bulk polymerisation of a mixture of vinyl monomers provides a first carboxyl-group-containing polymer, to which water-soluble and water-insoluble monomers are added and polymerised via emulsion polymerisation in the presence of the first polymer (column 1, lines 5-10, column 2, lines 9-26 and examples 1 to 6).

3.3.3 Moreover, paragraph [16] of D1 teaches that the preparation of the water-soluble first polymer as defined in claim 1 of that document can be prepared by various techniques such as solution polymerisation, bulk polymerisation or emulsion polymerisation (see point 2.1.4 above). That paragraph follows the description in paragraphs [14] and [15] of D1 which provide a list of monomers to be employed to prepare the first polymer, including methacrylic acid, beta-carboxyethylacrylate, methyl methacrylate, butyl acrylate, diacetone acrylamide and styrene, monomers used for the preparation of the water soluble polymers of example 11 and 12 of D1 and those of examples 1 to 3 of D3.

3.3.4 Therefore, starting either from the compositions disclosed in examples 11 and 12 of D1 or from the compositions described in examples 1-3 of D3, and having in mind the objective to merely provide further aqueous coating or ink compositions, the skilled person would find not only in D5, but also in paragraph [16] of D1 the suggestion to replace the water-soluble first polymers prepared by emulsion polymerisation of vinyl monomers in said examples 11 and 12 of D1 or said examples 1 to 3 of D3, by corresponding water-soluble first polymers based on the same vinyl monomers but obtained by bulk polymerisation.

3.3.5 The respondent's argument according to which the person skilled in the art starting from examples 11 or 12 of D1 and faced with the posed problem would not consider the teaching of paragraph [16] of D1 as the latter was to be read in line with the claims of D1 only fails to persuade. Whereas the skilled person merely analysing the disclosure of D1 in respect of those examples would not perform the mental act to modify those in the light of the information provided in paragraph [16] of that document, because he would have no reason to do so (see above points 2.1.3 to 2.1.5), the skilled person seeking to provide further aqueous coating or ink compositions than disclosed in those examples would be left with no choice as to modify them taking into account any envisageable measures known from the prior art, including a change of the preparatory method for obtaining the water-soluble first polymer as suggested in paragraph [16] of D1.

3.3.6 The respondent also argued that a person making emulsion polymers would be deterred to use the very different process of bulk polymerisation, as bulk polymerisation and emulsion polymerisation required significant modifications. This allegation was made with reference to paragraph [71] of the patent in suit and the impossibility to use the same amount of alpha-methylstyrene used in a bulk polymerisation process in an emulsion polymerisation. Paragraph [71], however, does not refer to any deterrent for a skilled person starting from an oligomer that can be prepared by emulsion polymerisation to prepare an oligomer with the same monomers but by bulk-polymerisation, let alone in respect of the oligomers prepared by emulsion polymerisation in examples 11 and 12 of D1 or in examples 1 to 3 of D3.

3.3.7 Moreover, as indicated by the respondent in particular in view of D7, it is not disputed that bulk polymerisation is a different technique from emulsion polymerisation, requiring known measures, in particular different reaction temperatures, equipment and initiators. It is also not disputed that the skilled person based on the common general knowledge is able to perform such bulk polymerisation of vinyl monomers. In the absence of any evidence to the contrary and compelling reason why this would not be possible, it is concluded that the specific vinyl monomers used in examples 11 and 12 of D1 or those used in examples 1 to 3 of D1 for the preparation of the water-soluble polymer by emulsion polymerisation can be also bulk- polymerised, in line with the information provided in paragraphs [17], [20] and [24] of the patent in suit.

3.3.8 The respondent argued on the basis of D6 that bulk polymerisation is a cumbersome technique and that the disadvantages of bulk polymerisation would outweigh its benefits so that the skilled person would be deterred to prepare the first oligomer by bulk polymerisation. Given the established principle that the answer to the question as to what a person skilled in the art would have done depends on the result he wished to obtain (T 939/92, OJ EPO 1996, 309; Reasons for the decision, point 2.5.3), the fact that, in the present case, the skilled person is deemed to be merely seeking to provide further aqueous coating or ink compositions, i.e. regardless of the difficulty to obtain such compositions, the use of bulk polymerisation for the preparation of the water-soluble first polymer is considered by the skilled person as a useful and obvious measure. In other words, the skilled person is merely accepting known disadvantages linked to the use of the bulk polymerisation, which cannot confer any inventive character to the aqueous compositions of operative claim 1. In addition, the Board notes that D6 recommends the use of bulk polymerisation for the preparation of low-molecular weight polymers (as in fact is done in D5, see column 3, line 68), so that D6 on the contrary would provide an incentive to use bulk polymerisation for preparing the low-molecular weight water-soluble polymers of D1 (see paragraph [17]) or D3 (see claim 1).

3.3.9 Finally, the respondent argued that emulsion polymerisation and bulk polymerisation would lead for the present type of polymers to polymers having different architectures and molecular weight distributions, which was not contested by the appellant, which in the respondent's opinion would prevent the skilled person from preparing a first water-soluble polymer by bulk polymerisation instead of by emulsion polymerisation. This argument also fails to convince, because the skilled person is merely seeking to provide further aqueous coating or ink compositions, i.e. compositions which do not necessarily contain a first water-soluble polymer being identical in all aspects, in particular with respect to architecture and molecular weight distribution.

3.3.10 Accordingly, starting from D1 or D3, in particular from the compositions disclosed either in examples 11 and 12 of D1 or examples 1-3 of D3, the skilled person having in mind the objective to merely provide further aqueous coating or ink compositions would be guided by the prior art to prepare the first water-soluble polymer by bulk polymerisation rather than by emulsion polymerisation, arriving thereby in an obvious manner at aqueous compositions falling within the ambit of present claim 1.

3.4 In view of the above, the subject-matter of claim 1 of the patent in suit does not meet the requirements of Article 56 EPC. Consequently, the main request is not allowable.

Auxiliary requests I to III

4. The compositions prepared in examples 11 and 12 of D1, and examples 1 to 3 of D3 contain adipic acid bishydrazide (ADH) as crosslinking agent and the first water-soluble polymer of those compositions contain diacetone acrylamide as a cross-linkable vinyl monomer bearing a keto group (see above points 2.1.1. and 3.1.4, respectively).

5. Accordingly, the additional modifications contained in the auxiliary requests, i.e. use of a cross-linking agent (auxiliary requests I to III) and of a cross-linkable group which includes keto, aldehyde and/or acetoacetoxy carbonyl groups (auxiliary request II), in particular diacetone acrylamide (auxiliary request III), do not introduce any additional distinguishing features over the aqueous compositions representing the starting point for assessing inventive step (starting from either D1 or D3 as closest prior art). As a result, claim 1 of any of the auxiliary requests still encompasses the embodiments of claim 1 of the main request which have been shown to be derivable in an obvious manner from the state of the art. Accordingly, these auxiliary requests must also fail on the same ground.

Order

For these reasons it is decided that:

1. The decision under appeal is set aside.

2. The patent is revoked.