T 0243/23, can a polymer that “consists of” a matrix polymer and a dispersed polymer comprise any further components?

In T 0243/23 the decision to revoke the patent EP 3307820 for lack of sufficient disclosure was contested by the Patentee (P). Claim 1 of the patent claimed a polymer dispersion: a heterophasic propylene copolymer “consisting of” a propylene-based matrix and a dispersed ethylene-alpha-olefin copolymer and was further defined in having specific product properties (a high melt flow rate and a low emission of organic compounds). 

The examples in the patent demonstrated a method for obtaining the copolymer composition. In this method after combining the two polymers to form a dispersion a ‘visbreaking’ step was carried out. Visbreaking is a method for reducing the viscosity of a polymer by partly breaking down the polymer chains. In the examples a reaction with an additional peroxide compound was used for reducing the chain length. The visbreaking was presented as a method for obtaining the claimed product properties. 

Claim 1 claimed a composition “consisting of”. The OD found this feature clear and therefore saw no need to consult the description. 

The OD then assessed that the examples exclusively demonstrated polymer compositions comprising peroxide breakdown products (due to the visbreaking). Since these products were deemed excluded by the “consisting of” definition, the examples were found not to be representative for the claims, and the patent was therefore considered not enabled. 

The Appeal

The P appealed this decision and opposed the narrow interpretation of the compounds ‘ethylene-alpha-olefin copolymer’ and ‘propylene-based matrix’ and pointed to the description and to the knowledge of the skilled person as support for this argument. G1/24 was deemed relevant for the current procedure, and the Appeal was stayed to await the outcome of that decision. In G1/24 claim interpretation and the relevance of the description for claim interpretation was assessed. 

In the decision the Board started with pointing out that assessing sufficiency starts with understanding how the skilled person understands the definition of claim 1 in the context of the description and the drawings. According to the Board the description points out that: 

So the Board found that the “consisting of” primary points to the dispersion morphology. The Board then assessed how a skilled person would read the ‘ethylene-alpha-olefin copolymer’ and ‘propylene-based matrix’ that form this morphology.

The propylene-based matrix was deemed broad by nature, since such definition covers a wide range of propylene related compounds. The ‘ethylene-alpha-olefin copolymer’ was discussed in more detail, and the Board referred to positions of the Respondents (Opponents) and to literature on how to interpret this feature.

The Board made a difference between the copolymer being a physical entity, so a phase in the dispersion and the chemical composition per se. The Board found that ‘ethylene-alpha-olefin copolymer’ in the context of the dispersed phase of claim 1 refers to the base polymer. The Board pointed to that the prior art demonstrated that such base polymer may contain additives usual in the art and comprises anyhow catalyst residues because without a catalyst no polymer can be formed. 

The Board also made a comment on the two-part form of the claim. The disputed feature was in the re-amble. Such preamble designates the technical features necessary for the definition of the claimed subject matter and forms part of the prior art. The Board saw this as a motivation to further consult the understanding of the prior art and found confirmation in the prior art on file that heterophasic propylene copolymers contained residues of organic peroxides.

The Board therefore concluded that the patent in suit taught the skilled person at least one way for carrying out the claimed invention since the examples are representative for the claimed subject matter. 

Decision of the Board

The invention in accordance with the main request (patent as granted) had not been shown to be insufficiently disclosed within the meaning of Article 100 (b) EPC. The case was remitted to the Od for further prosecution. 

Summary written by Vincent Verhoeven and Kolja Adamczyk of the NLO EPO Case Law Team