Obviousness

Obviousness Analysis of US Patent 9363997 under 35 U.S.C. § 103

US Patent 9363997 (hereafter '997 patent) discloses methods and compositions for the generation of peracetic acid (PAA) on-site at the point-of-use. The invention primarily focuses on:

1. Liquid compositions comprising aqueous hydrogen peroxide and a liquid acetyl precursor (preferably triacetin) for generating non-equilibrium PAA solutions.
2. Methods for continuously or intermittently generating non-equilibrium PAA solutions on-site using these liquid compositions, by introducing them to water and then adding an aqueous source of alkali metal or earth alkali metal hydroxide.
3. Freely-flowable, solid peroxygen compositions for laundry bleaching and stain removal, comprising a liquid acetyl precursor (preferably triacetin), a water-soluble solid source of hydrogen peroxide, and a water-soluble solid source of alkalinity.

The obviousness analysis under 35 U.S.C. § 103 requires identifying prior art combinations that would make the claimed invention obvious to a person having ordinary skill in the art (PHOSITA) and articulating a motivation to combine those references.

1. Obviousness of Liquid Compositions and Methods for On-Site PAA Generation

The '997 patent's liquid compositions and methods for on-site PAA generation generally involve:

• A pre-mixture of aqueous hydrogen peroxide and a liquid acetyl precursor (specifically highlighting triacetin due to its unexpected solubility in hydrogen peroxide).
• Adding this pre-mixture (or its components separately) to water.
• Subsequently adding an aqueous source of alkali (e.g., NaOH) to rapidly generate PAA.

Prior Art Combination: WO 01/46519 A1 in view of the '997 patent's own discussion of TAED drawbacks and common chemical knowledge regarding triacetin and perhydrolysis.

Explanation of Obviousness:

WO 01/46519 A1 explicitly discloses a process for generating non-equilibrium solutions of PAA on-site at the point-of-use. This process meters an aqueous solution of hydrogen peroxide into an agitated tank and co-meters a solid dry source of tetraacetylethylenediamine (TAED) from a storage-hopper. Aqueous sodium hydroxide is then introduced downstream to an in-line static mixer, and the mixture is directed through coiled tubing in a cooling tank to manage the exothermic reaction. This reference clearly teaches the core concept of on-site PAA generation using hydrogen peroxide, an acetyl precursor, and an alkali (sodium hydroxide) for rapid reaction.

The '997 patent itself identifies significant disadvantages of the WO 01/46519 A1 system, including "difficulty of accurately metering a solid and a liquid simultaneously, and the high capital equipment cost of the metering system, electronic controllers, agitation tank, coiled tubular reactor, and the cooling system."

The '997 patent also discusses prior art concerning solid TAED-based laundry bleaches, noting issues such as "low water solubility, especially at the cooler water temperature bleaching cycles" and that "Undissolved TAED... can even deposit on fabrics." Furthermore, the '997 patent highlights the drawbacks of using acetic anhydride in other on-site PAA generation methods, describing it as "expensive, very corrosive, an irritant, and highly flammable."

Motivation to Combine: A person having ordinary skill in the art (PHOSITA) would be highly motivated to overcome the known problems associated with using solid TAED or corrosive acetic anhydride as acetyl precursors in on-site PAA generation systems. Specifically, they would seek a liquid, safer, and more easily metered acetyl precursor to simplify the system described in WO 01/46519 A1 and address the solubility/metering challenges.

Triacetin (glycerol triacetate) is a well-known chemical compound with three acetyl groups capable of undergoing perhydrolysis. It is also known to be non-toxic, safe, non-corrosive, non-irritating, non-flammable, and Generally Recognized as Safe (GRAS) by the FDA, as stated in the '997 patent. Faced with the explicit problems of solid TAED metering (WO 01/46519 A1) and its solubility (as detailed in the '997 patent's background on laundry bleaches), a PHOSITA would naturally consider alternative acetyl precursors. Triacetin, being a readily available liquid and known source of acetyl groups, would be an obvious candidate to investigate as a replacement for solid TAED or hazardous acetic anhydride.

Replacing the solid TAED in the WO 01/46519 A1 system with a liquid acetyl precursor like triacetin would directly address the "difficulty of accurately metering a solid and a liquid simultaneously" and could lead to a simpler and less capital-intensive system by eliminating the need for a screw feeder for solids. While the '997 patent claims "unexpectedly high solubility in 50% hydrogen peroxide" for triacetin, the initial motivation to try a liquid acetyl precursor to solve known metering and safety problems would render the general substitution obvious. The specific formulation details, such as optimal mole ratios and pH for rapid reaction, would be arrived at through routine experimentation by a PHOSITA once the decision to use triacetin in such a system was made.

Therefore, combining the on-site PAA generation system and alkaline perhydrolysis principle from WO 01/46519 A1 with the substitution of a liquid, safer, and more easily handled acetyl precursor like triacetin would have been obvious to a PHOSITA motivated to improve the prior art methods.

2. Obviousness of Solid Peroxygen Bleaching and Stain Removal Compositions

The '997 patent's solid compositions involve:

• A liquid acetyl precursor (preferably triacetin).
• A water-soluble solid source of hydrogen peroxide (e.g., sodium percarbonate).
• A water-soluble solid source of alkalinity.
• The composition produces PAA upon introduction to water.

Prior Art Combination: General knowledge of TAED-based solid peroxygen bleaches (as discussed within the '997 patent's background) in view of common chemical knowledge regarding triacetin.

Explanation of Obviousness:

The '997 patent itself extensively details the problems with existing "TAED-based laundry bleaches." It states that:

• "only two [of four acetyl groups] are known to be available for perhydrolysis, making TAED an expensive acetyl precursor on a weight basis." (Inefficiency)
• "TAED has low water solubility, especially at the cooler water temperature bleaching cycles that are less damaging to fabrics." (Poor performance at desired conditions)
• "Undissolved TAED... can even deposit on fabrics, necessitating a separate rinse step to remove it." (Undesirable side effect)
• "over time, when exposed to high humidity, 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. Because the PAA is volatile, It imparts an undesirable pungent odor to the product." (Storage instability and odor problem)

Motivation to Combine: A PHOSITA in the field of laundry bleaching and stain removal would be highly motivated to replace TAED with an alternative acetyl precursor that overcomes these well-documented deficiencies. The desired characteristics for such an alternative would include higher efficiency (more available acetyl groups), better water solubility (especially in cool water), and improved storage stability (less PAA odor formation).

Triacetin, being a triglyceride of acetic acid, is a known chemical with three acetyl groups. As noted by the '997 patent, triacetin is also inexpensive, non-toxic, safe, non-corrosive, non-irritating, non-flammable, and GRAS by the FDA. Given these characteristics, a PHOSITA seeking to improve upon TAED would find triacetin to be a logical candidate for investigation. While triacetin is a liquid, the concept of incorporating a liquid component into a solid, freely-flowable particulate composition is a common practice in formulation chemistry, often achieved by absorption onto solid carriers or careful blending techniques. The '997 patent even teaches specific methods for blending a liquid acetyl precursor like triacetin into a solid peroxygen composition to maintain flowability.

The advantages claimed by the '997 patent for its solid triacetin composition—such as efficiently utilizing acetyl groups, high solubility in cool water, and absence of undesirable PAA odor upon storage—directly correspond to the identified problems of TAED. This strong problem-solution relationship indicates that a PHOSITA, motivated by the known drawbacks of TAED, would have a clear reason to modify existing TAED-based solid bleach formulations by substituting triacetin as the acetyl precursor. The development of a "freely-flowable" solid composition containing a liquid triacetin would be the result of routine formulation optimization.

Therefore, the substitution of triacetin for TAED in a solid peroxygen bleaching composition comprising a solid hydrogen peroxide source and a solid alkalinity source, driven by the desire to solve the known problems of TAED, would have been obvious to a PHOSITA.