Rohm and Haas Co & Anor v Collag Ltd & Anor

Patent claims must be construed purposively by reading the claims with the specification. The court must avoid both strict literalism and an unfettered use of the claims as guidelines, seeking fair protection with reasonable certainty for third parties. The judge determines the meaning of the specification, assisted by expert evidence on technical terms of art.

On this patent, “surfactant” meant an amphiphilic substance and did not include a non-amphiphilic flow aid. The Improver questions applied to the alleged variant, which was outside the claim because it materially affected how the invention worked. The court also indicated, obiter, that public prosecution-file material may be used cautiously to resolve genuine ambiguity after considering the specification and drawings.

Rohm and Haas brought patent infringement proceedings concerning a process for manufacturing water-dispersible propanil granules. Collag counterclaimed for revocation and a declaration of non-infringement in relation to Process B. The revocation claim was later abandoned.

The High Court, Chancery Division (Patents Court), determined preliminary issues in favour of Collag. It construed “surfactant” in claim 1 as limited to amphiphilic substances and held that Process B did not infringe, including because the use of a non-amphiphilic flow aid was not an immaterial variant. Rohm and Haas appealed. The central questions concerned construction of the claim, the burden of proof, expert evidence, prosecution history and application of the Improver questions.

Lord Justice Robert Walker gave the leading judgment. Lord Justices Keene and Peter Gibson agreed. The appeal was dismissed.

1. Construction. Claims had to be construed purposively, by reading them with the specification. The court endorsed the approach described in Hoechst Celanese Corporation v BP Chemicals [1999] FSR 319 and Kastner v Rizla Ltd [1995] RPC 585. The objective was to avoid both a strict literal construction and treating the claims merely as guidelines, while securing fair protection and reasonable certainty.
2. The purpose of the patentee had to be ascertained objectively from the specification and other admissible material. The specification was poorly drafted, but its language, context and examples supported the conclusion that “surfactant” meant an amphiphilic substance. Its reference to the broad sense of the term did not extend the claim to non-amphiphilic flow aids.
3. The judge remained responsible for deciding what the specification meant. Expert witnesses could assist with scientific terms of art, particularly where terminology had several meanings, but their evidence could not replace the judge’s function.
4. Burden of proof. Since the preliminary issues arose solely from Collag’s counterclaim for a declaration of non-infringement, the burden on the factual issue lay with Collag. The judge had been entitled to reach that conclusion, following Mallory Metallurgical Products v Black Sivalls & Brison Inc [1977] RPC 321.
5. Prosecution history. Obiter, the court considered that public material from the granting file could be used with restraint where, after consideration of the description and drawings, the meaning of the claims remained genuinely uncertain. The court regarded Ciba-Geigy v Oté Optics (13 January 1995) as persuasive guidance. The issue did not need to be decided for the appeal.
6. Variant. The Improver or protocol questions were applicable. The first question was essentially factual. The use of a non-amphiphile as a flow aid had a material effect on how the invention worked, so the variant was outside the claim. The fact that both processes produced a saleable product did not establish that their products were identical. The judge’s affirmative answers to the second and third questions were academic but were also upheld.
7. The appellants were ordered to pay 85 per cent of the respondents’ costs, with an interim payment of £30,000 to Agform, subject to the further directions recorded in the order.

• Court of Appeal (Civil Division): Dismissed the appeal from the order determining the preliminary issues. The court upheld the construction of “surfactant” and the declaration of non-infringement.
• High Court, Chancery Division (Patents Court): On 28 July 2000, Neuberger J determined the preliminary issues in favour of Collag and made a declaration of non-infringement in relation to Process B.