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Case law 5 May 2022

Inventiveness of a flame retardant

An old prior art document competed with a more recent prior art document for being the closest prior art. Based on the problems as addressed in the documents, both documents were suitable as the closest prior art. Still, the old document with the most structural similarities was not selected. The reason for this was that also the expectation to solve the objective technical problem should be included in the consideration. Objectively, the skilled person would only start from a document that holds a reasonable expectation.
  • A closest prior art should represent “a situation as close as possible in reality to that encountered by the inventor”, therefore “the skilled person with a prospect of achieving the goals addressed in the patent in suit would need a valid reason to return to the teaching of the (old) document and disregard the evolution in technology”.
  • The goals of the patent should be realistically obtainable based on the selected closest prior art.


Interpretation of the claim

In this Opposition Appeal, inventiveness of composition claim 1 was discussed. Claim 1 concerned a flame retardant polyamide resin composition, comprising an aromatic polyamide, a phosphinate, an inorganic reinforcing agent, and a synergist.

The Appeal

During opposition two documents were considered as the closest prior art for inventive step; D7 and D11. D7 was a relatively recent document (published in 2004) concerning flame retardants comprising aliphatic polyamides, whilst D11 was much older (published in 1977) and concerned flame retardants comprising aromatic polyamides.

Both documents concern the problem of flame retardation and also addressed a manufacturing issue, being that the matrix resin may decompose upon processing into construction pieces for electrical apparatuses, due to the required high processing temperature. Considering both publication concern the same purpose as the opposed patent, the Opposition Division (OD) deemed D11 to be the closer prior art for the reason of disclosing aromatic polyamides. In view of this, D7 was not further considered and claim 1 was deemed not inventive over D11.

The Patentee appealed the decision pointing to that D11 concerned less demanding and therefore obsolete requirements on flame retardation; moreover, allegedly processing issues were not addressed in D11. The Patentee therefore argued that the skilled person would not consider D11 as a suitable starting point.

The Board of Appeal (BoA) assessed the issue of the selection of the closest prior art as follows. First, the BoA indicated that a document should be the closest prior art when it represents “a situation as close as possible in reality to that encountered by the inventor” (Reason 2 and Case Law book I.D.3.2).

Subsequently, in a first step the purpose of the patent was thoroughly assessed and deemed to be:  1) excellent flame retardation (meeting the latest standard); 2) good heat stability in molding; and 3) excellent moldability. Polyamides were known to be processable only at relatively high temperatures.

The BoA then discussed technological development on flame retardants starting from D11. First, they noted that the phosphinates that were known from D11 were improved over time by combining them with nitrogen-containing compounds resulting in synergistic better flame retardation. Unfortunately, this combination was found to provide partial polymer degradation and discoloration especially at processing temperatures above 300°C. In a next technological development, the teaching of D7 solved this problem and so provided state of the art flame retardance without depolymerization at processing temperatures above 300°C.    

According to the BoA, D7 therefore represented a good starting point as it concerned the more adequate state on the art on flame retardation with regard to the subject-matter as claimed in the patent in suit (meeting the flame retardation criteria in force at the time of filing of the patent under appeal), and provided no degradation during molding at high temperature. This degradation was found to be of importance as it positively affected electric conductivity at high humidity which was undesirable for the construction pieces for electrical apparatuses (with which the appealed patent was concerned). The composition of D7 was also deemed structurally close even whilst it concerned aliphatic polyamides.

The BoA then considered D11 as an alternative closest prior art, and stated that for inventive step assessment purposes, there had to exist valid reason for the skilled person to consider this document as it concerned a less advanced technology. They concluded that the skilled person would only do so, if he could expect to reach its realistic goals by starting from this document. The BoA concluded this was not the case as D11 only disclosed compression molding at 235°C but not at 300°C.  Compression molding at 300°C was demonstrated in the patent and in D7. D11 was also silent on processing of polyamides needing such high processing temperatures. Moreover, the BoA also noted that the skilled person would not expect that the disclosures in D11 would meet the more recent flame retardation standards.

For these reasons, D11 was not deemed to be a realistic starting point, and an inventive step analysis starting from D11 was deemed to lack objectivity.

Decision of the Board of Appeal

An inventive step analysis with D7 as the starting point was not in the decision of the OD, and arguments and evidence provided for such inventive step analysis were not assessed. As a consequence, the BoA saw a “special reason” within the meaning of Article 11 RPBA 2020 and remitted the case to the OD.   

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