Federal Court Finds “Rigidification” Patent to be Sufficient but Obvious

Federal Court Finds “Rigidification” Patent to be Sufficient but Obvious

SNF Inc v Ciba Specialty Chemicals Water Treatments Limited, 2015 FC 997

SNF Inc. made a direct challenge to the validity of a patent owned by Ciba Specialty Chemicals Water Treatments Limited, its Canadian Patent No. 2,515,581 (“the ‘581 patent”), for anticipation, obviousness, insufficiency, overbroad claims, and for making false and misleading statements. [28] The ‘581 Patent was directed toward a process of “rigidifying” a slurry material at a waste site, but did not make clear what “rigidification” meant. The Federal Court (“the Court”) found that the invention was merely to add a polymer to the slurry, which was known in the prior art, and to continue to do so until the slurry rigidified. [191] The Court found this solution to be obvious to try, [195] and sufficiently disclosed, [206] even though the meaning of “rigidify” was never made clear.

The ‘581 Patent

The ‘581 Patent does not contain a formula to achieve the benefits of rigidification nor did it specify what constituted rigidification. [23]

As a result of claim dependencies and the state of the art, the validity of the entire ‘581 patent rested on Claim 1, and the validity of Claim 1 rested on the meaning of “rigidify”: [26]

A process of rigidifying a material whilst retaining the fluidity of the material during transfer, in which the material comprises an aqueous liquid with dispersed particulate solids that is transferred as a fluid to a deposition area, then allowed to stand and rigidify, by combining with the material during transfer an effective rigidifying amount of an aqueous solution of a water-soluble polymer, said water-soluble polymer having an intrinsic viscosity of at least 5 dl/g (measured in 1 M NaCl at 25°C). [court’s emphasis]

The parties generally agreed about the makeup of the Skilled Person and their Common General Knowledge, [100] but there was disagreement about what the Skilled Person would have known about “rigidifying” a slurry.

The Court emphasized that the Skilled Person would have a familiarity with the hands-on skills involved in troubleshooting and varying routine parameters to attain the objectives of a particular waste management site. [102] One of the tools that would have been available to the Skilled Person was the in-line addition of water-soluble polymer to a slurry. [126] Although this technique may not have been reduced to print form, and may not have been the currently most widespread approach to rigidifying a slurry, it was still part of the Common General Knowledge. [105, 121, 123]

This technique is the same technique that is applied in the ‘581 Patent, but the patentee’s argument was that the patent took the technique further, and that was an issue that would turn on the precise meaning of “rigidification”. Failing to find guidance in the disclosure, [137] the Court needed to adopt the admittedly  imprecise definition that “rigidification” means “increasing the yield stress of a mineral deposit rapidly whereby the flow of the deposit is minimized and the weight of subsequent layers of like deposits is supported.” [158, 163]


Of particular interest in the anticipation analysis was that the Court could not discern whether one particular prior art publication, the “SBB Publication”, was anticipatory or not. The SBB publication arguably disclosed all 3 steps of claim 1, but, partially due to the imprecise description of the term “rigidify” given in the ‘581 Patent, the Court was unable to determine if rigidification actually occurred in SBB. It therefore could not be said to anticipate. [172]

The remaining prior art documents cited against the ‘581 Patent were not anticipatory simply because the precise iteration of the invention was not disclosed. [167, 175] The alleged prior uses of the claimed method could not be corroborated with evidence. [167-177, 180]


The Court’s finding that the Skilled Person would have the ability to vary routine parameters at any given waste treatment site was integral to the finding that the ‘581 Patent was obvious to try.

Since it was known to the Skilled Person that in-line addition of a water-soluble polymer in aqueous solution could result in some degree of rigidification, [186] the invention of the ‘581 Patent was simply “the effective rigidifying amount of an aqueous solution of water soluble polymer that leads to rigidification as defined by the Court”. [191]  Given that it was Common General Knowledge for the Skilled Person to troubleshoot and vary routine parameters to attain the objectives of the particular waste management, it would have been obvious to try for the Skilled Person to continue applying the polymer until an effective amount is reached and to discontinue once overdosing occurred. [195]

It was appropriate to apply the “obvious to try” test in these circumstance since the addition of polymer to rigidify a slurry at a waste management site involves a degree of experimentation due to the different objectives, slurry compositions, and site mechanics at each site. [196]

Sufficiency, Overbreadth & False and Misleading Statements

Even though the whole issue surrounding the ‘581 Patent was that it was not clear what “rigidify” meant, the Court found the patent to be sufficient. This conclusion was legally required, the Court thought, since it found that the Patent would have been obvious to try. [206] The Court commented that if it had accepted the patentee’s construction that “rigidification occurs when one obtains the result one desires”, then that construction would have rendered the patent insufficient. [207, 209]

Similarly, given the narrow scope that the Court gave to the invention, the Court did not find the claims to be overbroad. [213]

The Court also found that the ‘581 Patent falsely, and with an intention to mislead, made statements to the effect that certain prior art taught away from using water-soluble polymer, but these statements were not material. [225, 230]


This case put the Court in the odd position of having to find that the method to achieve “rigidification” was sufficiently disclosed, in order to support its finding that it was obvious to try, even though the whole problem with the patent was that it was not clear what “rigidification” meant in the first place. It seems that without a detailed description of how to achieve “rigidification”, the ‘581 Patent amounted to simply teaching that one should add a well-known polymer to a slurry until it works – an idea which would have been considered routine to a Skilled Person whose job is to constantly  vary and troubleshoot process parameters at a waste management site. If the ‘581 Patent had been construed to teach anything more, it would not have sufficiently disclosed that teaching. [209]