CNIPA Sets Out When Parameter Features Qualify as Distinguishing Features
Date: 4 September 2025
【Volume 157】
In chemical patents, the physical or chemical properties of the claimed polymer are often described using parameter features in order to demonstrate novelty and inventive step. However, this practice has led to considerable controversy in patent examination, especially when it is difficult to directly compare the claimed invention with the prior art in terms of the parameter features. Determining whether such parameter features have already been disclosed in prior art has become one of the common challenges in the examination and invalidation of polymer-related patents. In a recent invalidation case involving a poly(arylene ether) copolymer, the China National Intellectual Property Administration (CNIPA) provided a concrete example illustrating how to assess whether a parameter feature constitutes a distinguishing technical feature when examining novelty and inventive step.
Case Fact
The disputed patent is titled "Poly(arylene ether) copolymer" (Patent No. ZL200680046261.0, ‘261 patent) and owned by the patentee SABIC Global Technologies B.V. The requester for the invalidation is Hebei Jianxin Biotechnology Co., Ltd. Upon examination, the CNIPA issued an Invalidation Decision, No. 560904, maintaining the validity of the patent.
Comparison Between ‘261 patent and the Exhibit
Claim 1 of ‘261 patent claims a poly(arylene ether) copolymer, which is the product of oxidative copolymerization of 2,6-dimethylphenol and 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane. The claimed poly(arylene ether) copolymer is defined by four parameter features:
(A) “the poly(arylene ether) comprises, on average, 1.8 to 2 hydroxyl groups per molecule” (hereinafter as “number of hydroxyl groups”);
(B) “the poly(arylene ether) copolymer has an intrinsic viscosity of 0.04 to 0.15 deciliter per gram” (hereinafter as “intrinsic viscosity”);
(C) “the poly(arylene ether) copolymer comprises 10 to 70 mole percent of copolymer chains comprising a terminal unit derived from the dihydric phenol” (hereinafter as “terminal dihydric phenol content”);
(D) “the poly(arylene ether) copolymer comprises 0.5 to 1.5 weight percent of units derived from 3,3′,5,5′-tetramethyl-4,4′-biphenol.”
Exhibit 1 (WO2005/003211A1), which is the most relevant prior art to claim 1 of the ’261 patent, also relates to a poly(arylene ether) copolymer. This copolymer is obtained by oxidative copolymerization of 2,6-dimethylphenol and 2,2’,3,3’,5,5’-hexamethyl-(1,1’-biphenyl)-4,4’-diol, and is defined by four parameter features:
(1) Hydroxyl equivalent;
(2) Number-average molecular weight (Mn);
(3) Weight-average molecular weight (Mw);
(4) Width of molecular weight distribution (Mw/Mn).
It is evident that the ‘261 patent differs from Exhibit 1 in both the selection of bisphenol monomers and the parameter features used to define the claimed invention.
The following will introduce the principles of determining whether Exhibit 1 discloses parameter features (A), (B), and (C) of the ‘261 patent, as demonstrated in the invalidation decision.
Opinion in the Decision of Invalidation:
1、 Parameter Feature (A): “Number of Hydroxyl Groups”
Regarding the “parameter feature (A): number of hydroxyl groups” in the ‘261 patent, although Exhibit 1 does not explicitly disclose this parameter, it does disclose the molecular weight and hydroxyl equivalent of the polymer. Moreover, it is known to a person skilled in the art that: number of hydroxyl groups = molecular weight / hydroxyl equivalent. Based on this formula, the number of hydroxyl groups disclosed in Exhibit 1 can be calculated and shown to fall within the scope of the ‘261 patent. Therefore, it is concluded that the number of hydroxyl groups in Claim 1 has been disclosed by Exhibit 1.
2、 Parameter Feature (B): “Intrinsic Viscosity”Regarding “parameter feature (B): intrinsic viscosity,” the dihydric phenol material used in the poly(arylene ether) copolymer of the ‘261 patent differ from that in Exhibit 1 (resulting in different molecular weights). Moreover, the polymer chains formed in the ‘261 patent and Exhibit 1 also exhibit significant differences. A person skilled in the art would not be able to determine whether the two possess the same macromolecular chain structure in chloroform, and thus cannot confirm that Exhibit 1 has the same intrinsic viscosity as the ‘261 patent. Therefore, the intrinsic viscosity in Claim 1 constitutes a distinguishing feature over Exhibit 1.
3、 Parameter Feature (C): “Terminal Dihydric Phenol Content”First, since the dihydric phenol monomer in Exhibit 1 differs from that of the ‘261 patent, its reactivity and potential side reactions may also differ from those in the ‘261 patent. Moreover, although the specification of the ‘261 patent states that the terminal dihydric phenol content varies with the intrinsic viscosity of the poly(arylene ether), this does not imply that the content depends solely on the intrinsic viscosity of the polymer. Additionally, a person skilled in the art would not be able to confirm that the bifunctional phenylene ether oligomer in Exhibit 1, when measured in chloroform at 25 °C, exhibits the same intrinsic viscosity as that in the ‘261 patent. Therefore, the terminal dihydric phenol content in Claim 1 constitutes a distinguishing feature over Exhibit 1.
Wisdom Analysis and Suggested Strategies
The decision in the field of polymer chemistry serves as a valuable example, illustrating whether a parameter feature used to define the disputed patent constitutes a distinguishing feature when such a parameter is not explicitly disclosed in the prior art.
First, even if the prior art does not clearly disclose a parameter feature, a parameter feature cannot be considered a distinguishing feature if it can be derived through a known formula.
Second, if a known equation demonstrates a correlation between a characteristic parameter and a structural feature, and differences in raw materials and processing conditions can further support that the local structure remains distinct, then it can be further concluded that “it cannot be confirmed based on its differing structure that the prior art possesses the same characteristic parameter as that of the disputed patent.”
Moreover, when interpreting the disclosures of prior art, an objective analysis must be conducted from the perspective of a person skilled in the art. If the disputed patent and the prior art share only partially similar processing conditions but employ different raw materials, it can be reasonably anticipated that the chemical reactions involved may differ, and it cannot be concluded that the prior art implicitly discloses the claimed characteristic parameters.
