Tuesday, 18 November 2014

T 0109/07 - Using the Problme-solution approach


The patent seems to cover an obvious embodiment according to the Problem-solution approach. The proprietor finds this unfair, since the prior art does not teach his broad idea and finds it inappropriate to use the problem-solution approach. The Board does not agree.

Summary of Facts and Submissions
I. European patent EP-B-1 104 493 was granted with 12 claims. The independent claims 1, 9 and 12 thereof read as follows :
"1. An electrodeposition bath, said electrodeposition bath comprising a resinous phase dispersed in an aqueous medium, said resinous phase comprising:
(a) an active hydrogen group-containing ionic electrodepositable resin, and
(b) a curing agent having functional groups reactive with the active hydrogen groups of (a),
comprising a lead-free electrodeposition bath containing at least one calcium compound selected from calcium acetate, calcium chloride, calcium formate, calcium nitrate, calcium oxalate, calcium molybdate, calcium titanate, calcium fluorosilicate and calcium carbonate present in an amount from about 10 parts per million to about 10,000 parts per million of total calcium and not more than about 200 parts per million soluble calcium, based on electrodeposition bath weight."
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III. The opposition division relied inter alia on the following documents: […]
IV. The opposition division rejected the patentee's main request for amendments to the description because they did not meet the requirements of Rule 88 EPC and Article 123(2) EPC. However, the claims of the auxiliary request, which were identical with the claims as granted, were found to meet the requirements of sufficiency of disclosure, novelty and inventive step. In particular, the disclosure of the zinc/calcium/molybdate compound Moly-White 212 in E1 was not considered to be an unambiguous disclosure of calcium molybdate and/or calcium carbonate as required by the claim language. The opposition division also held that, starting from either document E6 or document E1 as closest prior art, there was no incentive in the prior art to use calcium compounds in the specified amounts in order to obtain electrodeposition baths having the balanced improved properties demonstrated by the opposed patent.
V. The appeal was filed with letter dated 11 January 2007; the statement of grounds of appeal was filed under
VI. The patentee's (respondent's) observations were received under cover of a letter dated 5 September 2007. Also submitted were claims 1 to 12 as a first auxiliary request.
Further submissions of the appellant were received with letters dated 4 July 2008 and 28 November 2008.
VII. Under cover of letter dated 22 April 2009, the respondent filed an amended set of claims as a first auxiliary request.
Claim 1 of the said auxiliary request differs from claim 1 of the main request in that the term "calcium molybdate" is deleted from the claim.
VIII. The following new documents were submitted during the appeal proceedings: […]
IX. The arguments of the appellant may be summarised as follows:
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X. The arguments of the respondent may be summarised as follows:
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Inventive step
The invention related to the effect of insoluble and soluble calcium on corrosion inhibition and appearance. The problem consisted in providing an electrodeposition bath that resulted in an improved balance of appearance and corrosion resistance. The prior art exclusively dealt with the effect of the anion, for example molybdate and chromate, on corrosion inhibition. Calcium was only disclosed in the prior art as a suitable counter-ion. It was not suggested that calcium in itself had a corrosion-inhibiting effect. Furthermore, the claimed limits of total and soluble calcium required for obtaining a balance of corrosion-inhibiting effect and appearance were not derivable from the prior art.
XI. Requests
The appellant requested that the decision under appeal be set aside and that the European patent be revoked.
The respondent requested that the appeal be dismissed, or, in the alternative, that the decision under appeal be set aside and the patent be maintained on the basis of the claims 1 to 12 filed with letter dated 22 April 2009 as a first auxiliary request.
Reasons for the Decision
1. Amendments (auxiliary request) […]
2. Objections under Article 100(b) EPC
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3. Novelty (main request, auxiliary request)
3.1 The appellant cited document E1, in particular example 3 thereof, as novelty destroying for the subject matter of the respective claims 1 of the main request and the auxiliary request.
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The board, having examined the remaining prior art documents, concludes that claim 1 of the main request satisfies the requirements of Article 54 EPC.
The same applies to process claim 9 and product-by-process claim 12, which refer directly or indirectly back to claim 1, and to the dependent claims 2 to 9, 10 and 11.
3.3 Claims 1 to 12 of the (first) auxiliary request are narrower in scope than the respective claims of the main request and are therefore novel for the same reasons as those given in respect of the main request.
4. Inventive step
4.1 Main request
4.1.1 The opposed patent concerns electrodeposition baths for the coating of metallic substrates.
The baths comprise a resinous phase, which consists of an electrodepositable resin and a curing agent, the resinous phase being dispersed in an aqueous medium, and a corrosion inhibitor selected from at least one calcium compound selected from calcium acetate, calcium chloride, calcium formate, calcium nitrate, calcium oxalate, calcium titanate, calcium fluorosilicate and calcium carbonate, present in amounts as stated in the claim.
4.1.2 The board considers that the most relevant prior art is to be found in documents dealing with electrophoretic coating compositions containing similar corrosion inhibitors, for instance E6.
Document E6 discloses an electrophoretic coating composition comprising an aqueous medium having dispersed therein a polycarboxylic acid binder resin and a sparingly soluble alkaline earth metal molybdate, preferably calcium molybdate. E6 reports that the alkaline earth metal molybdate has a rust-inhibiting effect equally excellent as chromic acid salts. According to example 3, calcium molybdate is employed in an amount of 1.2 parts per 100 parts of aqueous dispersion. See E6, abstract, column 1, lines 8 to 11; column 2, lines 2 to 6; column 2, lines 26 to 43; example 3; columns 5 and 6, Table 1; and claim 1.
The resin component according to E6 is self-hardening.
4.1.3 The next step in assessing inventive step is to define the problem underlying the patent in suit in the light of E6.
According to the patent in suit an objective of the invention was to provide lead-free electrodeposition baths which provide improved corrosion resistance of the electrocoated metal substrates, especially untreated steel (page 2, paragraph [0006]). However, since there is no evidence on file showing an improvement in corrosion resistance between the examples of the invention and examples according to E6, the problem to be solved has to be reformulated in less ambitious terms.
4.1.4 The technical problem underlying the patent in suit in the light of E6 may thus be seen in the provision of an alternative electrodeposition bath.
4.1.5 As a solution to this problem, the patent in suit proposes an electrodeposition bath according to claim 1 of the main request, characterised in that it comprises a resinous phase which contains
(a) an active hydrogen group-containing ionic electrodepositable resin, and
(b) a separate curing agent having functional groups reactive with the active hydrogen groups of (a).
4.1.6 The next step is to verify whether the problem has actually been solved.
Invention examples 1 to 5 of the patent in suit illustrate electrodeposition bath compositions containing soluble calcium compounds, whereas those of invention examples 9 and 10 to 15 contain insoluble calcium compounds. According to the invention, certain calcium compounds selected from the list recited in claim 1 and present in an amount indicated in the claim calculated as total calcium and soluble calcium and contained in an electrodeposition bath composition exhibit a corrosion-inhibiting effect. The opposed patent contains undisputed experimental evidence that the calcium compounds effectively reduce corrosion of untreated cold rolled steel panels coated with the claimed electrodeposition bath composition, measured as a reduced "scribe creep" after a salt spray test carried out in accordance with ASTM B117. At the same time, the visual appearance of the coated panels according to the invention, evaluated in terms of surface roughness and pinholing, was rated from the upper range of from 7 to 10 (10 = no defects; 0 = rough and pinholed). It was thus comparable to results obtainable with conventional electrodeposition bath compositions containing for instance the conventional corrosion inhibitor calcium molybdate (see Tables 1, 2 and 3).
In view of this evidence, the board is satisfied that the technical problem is successfully solved over the whole range claimed.
4.1.7 It remains to be decided whether the proposed technical solution is obvious in view of the prior art.
The electrophoretic resins according to E6 comprise a resin component which is self-hardening. The question arises whether it was obvious to replace a self-hardening resin by a resin hardening with a curing agent (b).
Electrodeposition resins comprising a separate curing agent, as opposed to self-hardening resins, are per se known in the pertinent art (see E1, E8). The respondent has admitted during oral proceedings that it is not per se inventive to replace a self-hardening resin by a resin hardening by addition of a curing agent. Further, the use of calcium molybdate as corrosion inhibitor with a polycarboxylic acid binder was known from E6 (example 3, claim 1). There is no evidence in the patent in suit that the calcium molybdate corrosion inhibitor interacts in some specific and surprising way with electrophoretic resins which contain a separate curing agent, as opposed to self-hardening resins.
4.1.8 The respondent argued that the invention resided in the teaching that calcium (rather than calcium molybdate) was corrosion-inhibiting. This teaching was not suggested by the prior art. Therefore, the well-known problem-solution approach for assessing inventive step had reached its limits and should not be applied in this particular case, or should at least be applied differently, in order to do justice to the achievements of the invention.
The board cannot accept this argument. The respondent's reasoning implies that following the problem-solution approach one would disregard a positive aspect of the invention counting in favour of the presence of an inventive step. However, neither the determining of the closest prior art nor the definition of the problem underlying the patent in suit in the light of E6 eliminate any aspects of the invention regarding soluble and insoluble calcium compounds or calcium pigments. When assessing inventive step, document E6 cannot be ignored, as it discloses the same calcium molybdate corrosion inhibitor as the patent in suit.
Even if the gist of the invention was in the discovery of the corrosion-protective activity of calcium in electrodeposition baths, the claims of the main request encompass the embodiment of an electrodeposition bath which comprises a conventional resin composition and the well-known corrosion inhibitor "calcium molybdate" in a conventional amount of from 10 to 10 000 ppm. It is this particular embodiment which renders the claimed subject matter obvious, for the reasons discussed under point 4.1.7.
The board also sees no peculiarity in the present case to justify not relying on the well-tried and proven problem-solution approach for assessing inventive step.
4.1.9 Therefore, the subject matter of claim 1 of the main request lacks an inventive step and the main request must be rejected.
4.2 Auxiliary request
4.2.1 Claim 1 of the auxiliary request differs from claim 1 of the main request in that calcium molybdate no longer appears in the list of calcium compounds.
4.2.2 The reasoning under points 4.1.1. to 4.1.5 (closest prior art, technical problem, technical solution) applies mutatis mutandis to the subject matter of claim 1 of the auxiliary request.
4.2.3 Hence, as a solution to the technical problem (4.1.4), the patent in suit proposes an electrodeposition bath according to claim 1 of the auxiliary request, characterised in that it comprises a resinous phase which contains (a) an active hydrogen group-containing ionic electrodepositable resin, and (b) a separate curing agent having functional groups reactive with the active hydrogen groups of (a), and a calcium compound selected from the list of claim 1.
4.2.4 It remains to be decided whether the proposed solution is obvious having regard to the prior art.
The corrosion-protective effect of calcium molybdate, known from documents E6 and E1 and exploited in the commercial product Moly-White 212, has generally been attributed in the prior art to the molybdate (MO3) - moiety, not to the calcium counter-ion. This may be immediately seen from the facts that document E6 advocates the use of any sparingly soluble alkaline earth molybdate, in particular of strontium and calcium molybdate, and that no particular preference is given to calcium over strontium as a counter-ion.
Document E9 discloses poly(arylenesulfide) (PAS) resin compositions showing little tendency to cause metal corrosion and comprising a corrosion inhibitor selected from molybdenum, oxoacids of Mo, sodium, potassium and strontium salts of ortho- and isopolymolybdic acid, basic calcium molybdates and others (see claim 1). Preferred corrosion inhibitors are basic zinc molybdate, basic zinc calcium molybdate and basic zinc molybdate phosphate (claim 3; example 6, Table 7). The skilled person derives from E9 that apparently the passivating activity is borne by the molybdenum containing moiety and not by the calcium counter-ion.
There is also no indication in the art that any other calcium compound not containing the molybdate moiety could be useful as a corrosion-inhibitor in an electrodeposition bath. Document E7, page 10, line 23 to page 11, line 30, discloses, as examples of passivators in anticorrosive paint compositions, molybdates, vanadates, chromates, stannates, manganates, titanates, phosphomolybdates and phosphovanadates, preferably in the form of salts of a divalent metal, such as zinc, calcium, manganese, magnesium, barium and strontium. Here, too, the passivating activity is attributed to the anion, not to the cation or in particular to the calcium ion.
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In summary, there is no suggestion in the prior art that the calcium compounds listed in claim 1 of the auxiliary request exhibit a corrosion-protective effect in an electrodeposition bath.
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4.2.6 For these reasons, the subject matter of claim 1 of the auxiliary request involves an inventive step.
The same applies to independent method claim 9 which refers back to claim 1 and to independent claim 12, referring back to claim 9.
Dependent claims 2 to 8, 10 and 11 define particular embodiments of the inventive compositions and methods and are therefore also patentable.
The requirements of Article 56 EPC are thus met for the claims of the auxiliary request.
Order
For these reasons it is decided that:
1. The decision under appeal is set aside.

2. The case is remitted to the department of first instance with the order to maintain the patent in amended form on the basis of claims 1 to 12 filed with letter dated 22 April 2009 as a first auxiliary request, and a description to be adapted.
This decision has European Case Law Identifier ECLI:EP:BA:2010:T010907.20100715.The decision can be found here The file wrapper can be found here. Photo by David Hayward obtained via Flickr (unchanged).

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