Date: 24 June 2026

【Volume 173】

In the fields of chemistry and polymer materials, when microscopic structures are too complex to be clearly characterized by nomenclature or composition alone, the use of physical and/or chemical parameters to define claim scope has become an important means of protecting innovation. However, the inventive step of such non-traditional claim limitations is often subject to rigorous scrutiny in patent invalidation proceedings. This article focuses on the “Poly(arylene ether) Copolymer” case (Decision No. 560904), selected as one of the “Top Ten Patent Reexamination and Invalidation Cases of 2023” by the China National Intellectual Property Administration (CNIPA), examining CNIPA’s multi-layered approach to assessing parameter features, as well as the strategic implications for patent portfolio development.

Case Facts

The disputed patent (ZL200680046261.0), owned by GE Speciality Engineering Plastics Global Technology LLC, an affiliate of SABIC, relates to a polymer plastic widely used in fields such as 5G communications and semiconductor chips. The invalidation requester, Hebei Jianxin Biotechnology Co., Ltd., submitted the closest prior art (Evidence 1) and argued that the two inventions employed identical raw materials and reaction types, and that the parameters recited in the disputed patent were already encompassed by the prior art. Accordingly, the invalidation requester asserted that the disputed patent lacked an inventive step. After examination, CNIPA issued Decision No. 560904, maintaining the validity of the disputed patent in its entirety.

Claim 1 of the disputed patent introduces four key physical and/or chemical parameters to distinguish the claimed invention from the prior art:

1.　Hydroxyl number: an average of 1 to 2 terminal hydroxyl groups per molecule;

2.　Intrinsic viscosity: only 0.15 dl/g, measured in chloroform at 25°C;

3.　Bivalent unit content: 40 wt% to 70 wt%; and

4.　Biphenyl unit content: 0.5 wt% to 1.53 wt%.

Legal Standards and CNIPA’s Examination Approach

According to China’s Patent Examination Guidelines, where a product cannot be objectively distinguished from the prior art based on the parameters, the examination authority may apply the presumption principle and directly presume that the claimed product is identical to the prior art, thereby shifting the burden to the patentee to demonstrate differences in microstructures. However, when applying this principle, the examiner must adopt the perspective of a person ordinarily skilled in the art and conduct a three-tier analysis based on the underlying scientific principles:

1.　Conventional Parameter (Hydroxyl Number): Disclosed by the Prior Art

Although Evidence 1 does not expressly disclose the hydroxyl number, it provides detailed disclosures regarding the molecular weight and end-group structure. A person ordinarily skilled in the art could directly calculate the hydroxyl number from such information using well-known formulas, and the resulting value would fall within the claimed range of the disputed patent. Accordingly, this parameter does not constitute a distinguishing feature.

2.　Hydrodynamic Parameter (Intrinsic Viscosity): Successfully Established as a Distinguishing Feature

Intrinsic viscosity reflects the hydrodynamic volume of polymer chains in a solvent, i.e., the coil-to-stretch transition. Even where the overall molecular weight is identical, significant differences in solution flow resistance may arise from variations in internal chain arrangement, branching structure, or spatial configuration. In the present case, the disputed patent and Evidence 1 differ fundamentally in their reaction control and process routes. Accordingly, a person ordinarily skilled in the art would not reasonably expect the two polymers to exhibit identical polymer-chain behavior in chloroform. Therefore, it cannot be presumed that the two products are the same.

3.　Composition Parameters (Bivalent Unit Content and Biphenyl Unit Content): Successfully Established as Distinguishing Features

In a chemical reaction, the “initial feed ratio” is not equivalent to the “unit content” of the final product. Copolymerization is a dynamic and competitive process that is significantly influenced by factors such as relative reactivity ratios, catalyst systems, and reaction temperature. Because the disputed patent and Evidence 1 employ different process routes, a person ordinarily skilled in the art could not determine, based solely on the initial feed ratios, that the resulting products must necessarily possess the same microstructural composition. Accordingly, the Collegiate Panel declined to hastily apply the presumption principle.

Comparative Analysis Summary