Lanxess and Cabb fighting over a transport drum filled with thionyl chloride

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Case No. O2020_008 | Hearing of 24 November 2021

CABB logo

The plaintiff, Lanxess Deutschland GmbH, had sued CABB AG for infringement of the Swiss part of EP 2 468 653 B1, i.e. EP(CH) 2 468 653 H1.

EP 653 as initially granted pertained to a bunghole closure for closing a transport drum containing thionyl chloride (claim 1), a transport drum comprising a bunghole closure (claim 6), and a use of perhalogenated polymers for sealing a transport drum which at least partly contains thionyl chloride (claim 11).

Lanxess logo

The key feature of the patent pertains to a sealing which consists essentially of a perhalogenated polymer, in particular PTFE (more widely known as Teflon®) and/or PCTFE. According to EP 653, such sealings significantly reduce the corrosion of the transport drum which would occur if the thionyl chloride escaped and reacted with the humidity of ambient air.

The partial waiver published as EP(CH) 653 H1 was registered in accordance with a request filed by the proprietor in September 2019  — while, according to the avail­able online registers, the European patent was abandoned in all other countries. With the partial waiver, the independent claims directed to the bunghole closure and the use were deleted, and the remaining claim on the transport drum was limited, inter alia, to the feature that the drum is actually filled with thionyl chloride (and not only that it is suitable for this purpose).

Defendant did not dispute the infringement; only the question of validity of the patent remained. The defendant had relied on four public prior uses as closest prior art. One of the prior uses related to a drum containing a PTFE seal. However, the drum had been used for storing oxalyl chloride instead of thionyl chloride.

As became apparent in the course of the hearing, the expert opinion of the judge-rapporteur had been much in favor of defendant’s arguments.

Lonesome drum, corroded

Plaintiff argued that thionyl chloride is an exceptionally aggressive liquid requiring safety considerations going far beyond those for oxalyl chloride. This would be of utmost importance, in particular during transport of the drums when the sealing could be heavily and plastically deformed. Furthermore, plaintiff referred to a warning of Tri-Sure, a global leader in industrial closures and packaging components, according to which PTFE is not recommended for aggressive chemicals. In addition, the drums of the prior uses had not been suitable for storing thionyl chloride. Further, plaintiff questioned the public availability of the alleged prior uses.

In response, defendant argued that, on the basis of their inherent physical properties, the drums were actually suitable for storing thionyl chloride. Furthermore, plaintiff had not proven the alleged advantages re deformation behavior over previously known sealings. Moreover, the patent had not distinguished between thionyl chloride and less aggressive substances. Instead, it referred only generally to difficulties in storing corrosive liquids of which oxalyl chloride was just another example. The objective technical problem was therefore only to fill the drum with another corrosive liquid. Relating to the public availability, defendant offered two witnesses.

Close to the end of the hearing, some confusion arose as to where the seal was exactly located in some of the prior uses. Plaintiff’s statements in this respect appeared to surprise the judges. It was briefly discussed whether this issue had to be regarded as a novum (and would therefore not be admissible). However, plaintiff pointed to a passage in a written submission which allegedly contained this reasoning before closure of the file.

No settlement discussions took place. The President finally announced that a judgment could probably be expected in early 2022.

Reported by Stephan BALLIEL-ZAKOWICZ and Martin WILMING


Case No. O2020_008 | Hearing of 24 November 2021

Lanxess Deutschland GmbH

Panel of Judges:

    • Dr. Mark SCHWEIZER
    • Dr. Tobias BREMI
    • Dr. Martin SPERRLE


    • Dr. Tobias BREMI

Court Clerk:

    • Susanne ANDERHALDEN

Representative(s) of Plaintiff:

Representative(s) of Defendant:

    • Klaus FEGER (Holzach)
    • Dr. Cornelia HOFFMANN (SBMP), assisting in patent matters



As initially granted:

After the partial waiver:


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