US 9363997

US Patent 9363997 Summary:

• Title: Methods and compositions for the generation of peracetic acid on site at the point-of-use
• Assignee: Enviro Tech Chemical Services Inc
• Inventors: Michael S. Harvey, Jonathan N. Howarth
• Filing Date: April 8, 2015
• Issue Date: June 14, 2016
• Abstract: The patent discloses methods for generating non-equilibrium solutions of peroxyacetic acid (PAA) on-site. These methods involve introducing triacetin and aqueous hydrogen peroxide to water, mixing them, and then adding an aqueous source of an alkali metal or earth alkali metal hydroxide. Triacetin is rapidly and highly converted into peracetic acid, resulting in solutions with a high PAA concentration.

Plain-Language Overview of Independent Claims:

• Claim 1 (Method for On-Site PAA Generation): This claim describes a method for continuously or intermittently creating a peracetic acid (PAA) solution at the location where it will be used (point-of-use) for disinfection or sanitation. The method involves:

  1. Providing water at the point-of-use.
  2. Providing a pre-mixed solution containing hydrogen peroxide and an acetyl precursor (a substance that reacts to form the acetyl group), which is soluble in aqueous hydrogen peroxide.
  3. Introducing this hydrogen peroxide-acetyl precursor solution to the water to form a mixture.
  4. Adding an aqueous source of an alkali metal or earth alkali metal hydroxide to the mixture to form a reaction medium, where hydrogen peroxide reacts with the acetyl precursor to produce PAA.

• Claim 17 (Liquid Composition for PAA Generation): This claim covers a liquid composition designed to produce a non-equilibrium solution of peracetic acid at the point-of-use. The composition includes:

  1. Aqueous hydrogen peroxide.
  2. A liquid acetyl precursor that can dissolve in aqueous hydrogen peroxide.
  3. A small amount of peracetic acid (trace amount).
  4. Water.

• Claim 21 (Solid Peroxygen Composition for Bleaching/Stain Removal): This claim describes a free-flowing, solid composition containing peroxygen for use in laundry bleaching and stain removal. It consists of:

  1. A liquid acetyl precursor.
  2. A water-soluble solid source of hydrogen peroxide.
  3. A water-soluble solid source of alkalinity.

• Claim 26 (Method of Preparing a Hydrogen Peroxide-Acetyl Precursor Solution): This claim outlines a method for preparing the hydrogen peroxide-acetyl precursor solution mentioned in Claim 17. The method involves:

  1. Introducing a liquid acetyl precursor that is soluble in aqueous hydrogen peroxide to a solution of aqueous hydrogen peroxide.
  2. Allowing these components to mix to form the hydrogen peroxide-acetyl precursor solution.

• Claim 29 (Method of Preparing a Solid Peroxygen Composition): This claim details a method for preparing the free-flowing, solid peroxygen composition described in Claim 21. The method involves:

  1. Blending a liquid acetyl precursor, a water-soluble solid source of hydrogen peroxide, and a water-soluble solid source of alkalinity to create the solid composition.

Litigation/Legal Status (as of April 26, 2026):

US Patent 9363997 is currently active and is involved in litigation.

• It is asserted in a district court lawsuit, Enviro Tech Chemical Services, Inc. v. Clean Chemistry, Inc., Case No. 1:24-cv-1313, filed in the Western District of Texas on October 29, 2024. This case also involves related patents US 8,546,449, US 9,737,072, and US 9,730,443. A trial in this District Court Case is scheduled for the week of December 28, 2026.
• An Inter Partes Review (IPR2025-01471) challenging claims 1-14 of US 9363997 was filed by Clean Chemistry, Inc. on September 2, 2025, before the Patent Trial and Appeal Board (PTAB). This IPR is currently marked as "Not Instituted - Procedural."
• Separately, a related patent (US 10,912,321), which is a continuation-in-part of a patent in the same family, was the subject of an appeal to the Federal Circuit (Enviro Tech Chem. Servs., Inc. v. Safe Foods Corp., Appeal No. 2024-2160). On May 4, 2026, the Federal Circuit affirmed a district court ruling that certain claims of US 10,912,321 were invalid as indefinite, specifically concerning the term "about" in relation to a claimed pH range. While this ruling is not directly on US 9363997, it indicates ongoing challenges to Enviro Tech Chemical Services' patent portfolio in the peracetic acid field.