The patent relates to blends of encapsulated biocides with free biocides. In particular, it relates to blends of encapsulated “DCOIT” with free biocides.
The patent also relates to marine antifouling coatings and paints incorporating free biocides and encapsulated DCOIT, and using the free biocides and encapsulated DCOIT in marine antifouling coatings and paints.
Brief outline of the procedure
The opposition was rejected.
The opponent appealed the rejection of the opposition.
The board held that claim 1 as granted infringed Art 123(2) in view of the deletion of an essential feature which could be considered unclear and its replacement by a clearer feature.
As the same problem occurred in AR 1-6, the patent was revoked.
The claims at stake
Claim 1 as filed
Claim 1 as filed essentially relates to a coating composition comprising a microencapsulated biocide and a free (i.e. not microencapsulated) isothiazolone biocide or antifouling agent.
In claim 1 as filed, contained the following functional feature:
- ”wherein the concentration of free isothiazolone biocide or antifouling agent is from 0.25 percent, by weight of the composition, up to a concentration that does not reduce the glass transition temperature of the film forming polymer by more than 20° C.”
The functional feature in claim 1 as filed is an essential feature
According to the application as filed, page 2, lines 10 to 14,
- “there is a need for improved marine antifoulant paint compositions in which the balance between free DCOIT and encapsulated DCOIT is such that the amount of free DCOIT available is high enough to control fouling organisms but low enough to ensure that the Tg of the paint film is not reduced to a level wherein the integrity of the paint film is compromised.”
The functionally defined upper limit of the concentration range for the free isothiazolone biocide is set out as being necessary, and hence essential, for solving the technical problems addressed by the application as filed, namely maintaining the integrity of the paint film and avoiding prolongation of the drying time of the coating composition.
Claim 1 as granted
In claim 1 as granted this functional feature was replaced by the following one:
- “wherein the concentration of free isothiazolone biocide is from 0.25 % to 15 % of the weight of the film forming polymer or binder solids”.
The opponent’s position
The functional feature in claim 1 as originally filed was disclosed as essential in the application as originally filed. It could not be deleted, nor could it be replaced by a different non-equivalent feature such as the numerical upper limit in claim 1 as granted.
This was because the question of whether or not the glass transition temperature of the film forming polymer was reduced by more than 20 °C depended on the coating composition under consideration and in particular the actual film forming polymer contained in it.
The proprietor’s position
The proprietor argued that the functional feature of claim 1 as filed had in fact not been deleted but replaced by the numerical upper limit. The application as filed disclosed the plasticising effect of DCOIT (paragraph bridging pages 1 and 2). Therefore, it was clear that the only quantitative teaching in the application as filed relating to DCOIT on page 8, lines 21 to 22, stating that
- “[i]n one embodiment, the free DCOIT is added in an amount of from 0.25% to 15% of the weight of the film forming polymer or the binder solids”,
- was meant to address this plasticisation problem and the reduction in Tg and was applicable to the invention of claim 1 as filed.
The proprietor submitted that the plasticising effect of certain biocides such as DCOIT on film forming polymers was well-known to the skilled person. The wording of claim 1 as granted stated the concentration of the free isothiazolone biocide in relation to the weight of the film forming or binder solids.
For the proprietor, this was a pointer to the skilled person that the coating composition of claim 1 of the main request should not contain too much free isothiazolone biocide, depending on the film forming polymer actually used.
For this reason, compositions in which, for example, concentrations of 15% of free isothiazolone biocide caused a Tg reduction of more than 20 °C precisely did not fall within the subject-matter of claim 1.
The proprietor also argued that the functional feature in claim 1 as filed could not be meaningfully interpreted by the skilled person as defining a boundary.
The replacement of the functional feature in claim 1 as filed by the numerical upper limit in claim 1 as granted was made to address the ED’s objections in this respect under Articles 83 and 84 EPC and should be considered allowable.
The board’s position
The application as filed does not disclose that the numerical upper limit of 15% is meant to be the same as the functionally defined upper limit of claim 1 as filed or that the latter is always complied with when the concentration of the free isothiazolone biocide is <= 15%.
Rather, the opposite conclusion must be drawn, namely that, as argued by the opponent, the question of whether or not the Tg of the film forming polymer is reduced by more than 20 °C depends on the coating composition under consideration and in particular the film forming polymer it contains.
In other words, it is very readily conceivable, and this was acknowledged by the proprietor at the OP, that claim 1 as granted encompasses film forming polymers for which amounts of free isothiazolone biocides close or identical to the numerical upper limit of 15% actually reduce the glass transition temperature by more than 20 °C, contrary to claim 1 as filed.
For the board, the proprietor’s argument ultimately means reading into claim 1 as granted a lower possible concentration for the free isothiazolone biocide precisely when concentrations close or identical to the numerical upper limit of 15% lead to a Tg decrease of more than 20 °C.
The board did not agree as the subject-matter of a claim is determined by its wording, which in the present case provides for an explicit upper limit of 15% for any film forming polymer.
The board did not agree with the last contention of the proprietor relating to the need of overcoming the objection raised under Art 83 and 84 during examination.
It is already clear from the wording of the functional feature that it is intended to define an upper limit for the concentration of the free isothiazolone biocide in the coating composition.
The fact that claim 1 as filed does not define an exact numerical upper limit may be due to the fact that the actual upper limit depends on the composition under consideration (see above).
For the board, any unclarity that may arise from an ambiguity in an application as filed is to the detriment of a patent proprietor, who is ultimately responsible for the drafting of the application as filed and its claims. The fact that a feature in the application as filed is unclear cannot therefore justify or excuse the complete deletion of the unclear feature or its replacement by another feature if this results in an extension beyond the content of the application as filed.
In fact, what prompted a patent proprietor to make a particular amendment to the claims cannot have any influence on the outcome of the assessment of the ground for opposition under Art 100(c).
Some conclusions to be drawn:
- An essential feature does not have to be marked as such for having this quality. It is sufficient that it results from the whole disclosure and in particular is necessary for solving the technical problems addressed in the application as filed.
- Deletion of an essential feature is always problematic, as it is objectionable under Art 123(2) as otherwise, the aim of the invention cannot be achieved. However, this is nothing new.
- An essential feature can at best be replaced by an equivalent feature, provided this equivalent feature is directly and unambiguously disclosed in the originally filed documents.
- If an essential feature is unclear in the independent claim as filed, it cannot be argued that replacing it by a feature which is apparently clearer is allowable under Art 123(2).
- The applicant is solely responsible for any ambiguity in the claims he files. This is nothing new under Art 113(2).