The invention patent titled “Polyurethane Polishing Pad” (Patent No. 201410448504.X) was originally owned by Rohm and Haas Electronic Materials CMP Holdings, Inc. and Dow Global Technologies LLC. The patent was subsequently assigned to DuPont Electronics Materials Holdings Co., Ltd. and DDP Specialty Electronic Materials US, LLC.
The two original patentees collectively owned a large number of granted patents relating to polyurethane polishing pads and had built a comprehensive patent portfolio in the CMP (Chemical Mechanical Planarization) field, creating patent barriers for companies engaged in the R&D and manufacture of polyurethane polishing pads.
A joint client of Beijing Kangrui Law Firm and Beijing Kangxin Intellectual Property Agency Ltd. instructed Kangrui and Kangxin to file a request for invalidation against Patent No. 201410448504.X (the “Polyurethane Polishing Pad” patent). A patent-invalidation team composed of Kangrui attorneys and Kangxin patent attorneys filed the first invalidation petition in April 2023. Despite thorough searching and preparation, an unfavorable decision maintaining the patent in force was issued on January 2, 2024. Subsequently, this invalidation case was selected by the China National Intellectual Property Administration (CNIPA) as one of the Top Ten Reexamination and Invalidation Cases of 2024.
In light of the above setbacks, and following the client’s instructions, the Kangrui/Kangxin team continued to work closely with the client to uncover new invalidation evidence. Based on the facts affirmed in the first invalidation decision, the team identified common general knowledge in the polyurethane field—used as the main evidence for combining references in the inventiveness assessment—and re-combined it with D1, the closest prior-art evidence used in the first invalidation. After the patent had been assigned to the new patentees, the team filed a second invalidation petition on January 6, 2025.
Before submitting another statement in response to the patentees’ arguments, the case team and the client repeatedly discussed the relevant technical issues, identified shortcomings in the patentees’ response, submitted well-reasoned arguments, and fully prepared for the oral hearing. During the hearing, the Kangrui/Kangxin team responded actively to the patentees’ positions, pointed out errors in the opposing arguments, addressed the technical questions of the panel in detail, and provided an in-depth technical analysis.
Ultimately, on July 25, 2025, Decision on Request for Invalidation No. 587759 was issued, declaring the patent invalid in its entirety. The panel gave high recognition to the new common-general-knowledge evidence, finding that the technical manual in the polyurethane field provided a clear motivation to combine for a person skilled in the art, thereby leading to the technical solutions of independent claims 1 and 5 and dependent claims 2–4 and 5–8. The decision to invalidate the patent in full removed obstacles to the client’s commercial activities and received high praise from the client.