Obviousness

Obviousness Analysis of US Patent 9,730,443 Under 35 U.S.C. § 103

This analysis identifies combinations of prior art references that would render the independent claims of US Patent 9,730,443 obvious to a person having ordinary skill in the art (PHOSITA), along with the motivations for such combinations. The analysis focuses on the prior art explicitly discussed within the patent document's "BACKGROUND OF THE INVENTION" section.

Independent Claims of US 9,730,443

The independent claims of US 9,730,443 define:

• Claim 1: A method for continuously or intermittently generating a non-equilibrium solution of peracetic acid (PAA) on-site for use as a disinfectant or sanitizer, comprising introducing a hydrogen peroxide-acetyl precursor solution to flowing water, mixing them, and then adding an aqueous source of an alkali metal or earth alkali metal hydroxide to form a reaction medium where PAA is generated within 30 seconds to five minutes.
• Claim 8: A method for continuously or intermittently generating a non-equilibrium solution of PAA on-site in a batch process, comprising providing a container of water, introducing a hydrogen peroxide-acetyl precursor solution to the water, mixing them, and then adding an aqueous source of an alkali metal or earth alkali metal hydroxide to form a reaction medium where PAA is generated within 30 seconds to five minutes, and the PAA solution has a pH of about 11.2 to about 13.37.
• Claim 15: A liquid composition for generating non-equilibrium solutions of PAA on-site, comprising about 23% to about 40% aqueous hydrogen peroxide, about 20% to about 52% triacetin, and water, wherein a trace amount of PAA is formed within the first day of preparation, and the mole ratio of hydrogen peroxide:triacetin is about 2.98:1 to about 12.84:1, and the pH is about 1.46 to about 2.2.

Analysis of Obviousness

Combination 1: WO 01/46519 A1 in view of known problems with TAED and general chemical knowledge.

Primary Reference:

• WIPO International Publication No. WO 01/46519 A1: This reference describes a process for generating non-equilibrium solutions of PAA on-site at the point-of-use. It involves metering an aqueous solution of hydrogen peroxide into an agitated tank, co-metering a solid dry source of tetraacetylethylenediamine (TAED) from a storage hopper using a screw feeder, and then feeding the mixture to an in-line static mixer where aqueous sodium hydroxide is introduced. The mixture is then directed through coiled tubing immersed in a cooling tank. This reference teaches the core concept of on-site PAA generation using hydrogen peroxide, an acetyl precursor, and an alkaline activator, in both flowing (static mixer, coiled tubing) and batch-like (agitated tank) contexts.

Motivation to Combine/Modify:
The background of US 9,730,443 explicitly highlights several disadvantages of the system described in WO 01/46519 A1 and other TAED-based systems:

1. Metering Difficulty: WO 01/46519 A1 suffers from "the difficulty of accurately metering a solid and a liquid simultaneously".
2. Solubility and Efficiency: TAED has "low water solubility, especially at the cooler water temperature bleaching cycles" and "only two [of four] acetyl groups on TAED" are available for perhydrolysis, making it "an expensive acetyl precursor on a weight basis". Undissolved TAED can also deposit on fabrics.
3. Stability: "solid TAED can react with the solid source of hydrogen peroxide and the free water to form PAA, as well as degrade the activity, making it less effective over time."
4. Cost and Complexity: The WO 01/46519 A1 system involves "high capital equipment cost of the metering system, electronic controllers, agitation tank, coiled tubular reactor, and the cooling system."

A person having ordinary skill in the art (PHOSITA) would be highly motivated to overcome these known problems. Given the solubility and efficiency issues of solid TAED, a PHOSITA would logically seek a liquid acetyl precursor that is more soluble and efficient. Triacetin is a well-known chemical compound and a recognized acetyl precursor, further noted in the patent as Generally Recognized as Safe (GRAS) by the FDA, non-toxic, and non-corrosive. The patent itself states that triacetin "displays an unexpectedly high solubility in hydrogen peroxide." Even if the exact degree of solubility was unexpected, the motivation to seek a more soluble, liquid acetyl precursor to avoid the problems of solid TAED would be evident.

Obviousness Argument for Claim 1 (Flowing Method):
WO 01/46519 A1 teaches a system for on-site PAA generation in a flowing stream using hydrogen peroxide, an acetyl precursor (TAED), and sodium hydroxide. A PHOSITA, motivated to address the known difficulties of metering solid TAED and its poor solubility and efficiency, would replace solid TAED with a liquid acetyl precursor like triacetin. It would be obvious to pre-mix the liquid triacetin with the aqueous hydrogen peroxide to create a single liquid stream, simplifying the metering process (addressing the "difficulty of accurately metering a solid and a liquid simultaneously" problem) before introduction to the flowing water. The subsequent addition of an alkali metal hydroxide (e.g., sodium hydroxide, as in WO 01/46519 A1) to trigger the perhydrolysis reaction is well-established in the art. Optimizing reaction time to maximize PAA generation (e.g., within 30 seconds to five minutes) for efficient on-site use would be a matter of routine experimentation.

Obviousness Argument for Claim 8 (Batch Method):
WO 01/46519 A1 also describes introducing hydrogen peroxide into an "agitated tank" with solid TAED, which encompasses a batch or semi-batch process in a container of water. The same motivations apply: a PHOSITA would replace solid TAED with a pre-mixed liquid hydrogen peroxide-triacetin solution to overcome the metering and solubility problems. The addition of aqueous sodium hydroxide, as taught by WO 01/46519 A1, would lead to an alkaline pH, which the patent itself notes is essential for "meaningful percent of the triacetin converted into PAA" (pH above 12 in Table VIII), and would naturally result in a PAA solution within the claimed pH range of 11.2 to 13.37. Optimizing reaction time would be routine.

Obviousness Argument for Claim 15 (Liquid Composition):
Given the strong motivation to replace solid TAED with a more soluble, liquid acetyl precursor, a PHOSITA would investigate known liquid acetyl precursors. Triacetin is a well-known example. The discovery that triacetin has good solubility in aqueous hydrogen peroxide would lead a PHOSITA to formulate a stable liquid pre-mix of these components. The patent explicitly states that the "hydrogen peroxide component of these compositions is remarkably stable" and their pH is "about 1.46 to about 2.2". It is well-known in the art that hydrogen peroxide and peracids are generally more stable under acidic conditions. Therefore, formulating a concentrated (e.g., 23-40% H2O2, 20-52% triacetin), acidic (pH 1.46-2.2) liquid pre-composition for simplified transport and later on-site activation would be an obvious step for a PHOSITA seeking to improve upon existing PAA generation methods. The formation of a "trace amount of PAA" during storage is an expected outcome of an ester (triacetin) and hydrogen peroxide in an aqueous solution, even at low pH, especially over extended periods, and does not negate the stability for practical storage and transport. The specific ratios would be a matter of routine optimization to achieve the desired concentration and stability for the subsequent on-site generation.

Summary of Combinations and Rationale:
The central inventive step claimed by US 9,730,443 relies on the specific combination of hydrogen peroxide with triacetin as a liquid acetyl precursor, especially as a stable pre-mix, for on-site generation. However, the background of the patent itself articulates the very problems with the prior art (e.g., solid TAED in WO 01/46519 A1) that the claimed invention purports to solve. A PHOSITA would be motivated to address these known problems by:

1. Replacing solid TAED with a liquid acetyl precursor: Triacetin is a known liquid acetyl precursor.
2. Forming a stable pre-mix: To overcome the difficulties of metering a solid and liquid simultaneously, and to streamline on-site delivery, it would be obvious to create a stable liquid solution of the chosen liquid acetyl precursor (triacetin) and hydrogen peroxide. The inherent stability of these components at low pH would be known or readily discoverable through routine experimentation.
3. Utilizing an alkaline environment: The perhydrolysis reaction with an acetyl precursor and hydrogen peroxide to form PAA is known to be base-catalyzed, and WO 01/46519 A1 already teaches the addition of aqueous sodium hydroxide. Achieving an alkaline pH for the reaction medium would be an expected and desired outcome.

Therefore, claims 1, 8, and 15 appear to be obvious combinations or modifications of the teachings of WO 01/46519 A1 with general chemical knowledge and the explicit motivations provided in the patent's own background section. The "unexpectedly high solubility" of triacetin in H2O2, while beneficial, might be considered a matter of degree or a result of routine experimentation in the context of seeking improved liquid acetyl precursors, rather than a truly non-obvious breakthrough that would overcome the strong motivation to combine.