Obviousness

Obviousness Analysis of US 9737072 under 35 U.S.C. § 103

This analysis examines whether the inventions claimed in US patent 9,737,072 would have been obvious to a Person Having Ordinary Skill in the Art (POSITA) at the time the invention was made. The analysis focuses on independent claims 1, 14, and 20.

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Claim 1 & 14: Method for On-Site Generation of Peracetic Acid (PAA)

Summary of Claims:

• Claim 1 describes a continuous or intermittent method for generating PAA on-site by: (a) providing a pre-mixed solution of aqueous hydrogen peroxide and triacetin; (b) introducing this solution into flowing water; (c) mixing; and (d) adding an aqueous alkali/earth alkali metal hydroxide to initiate the reaction.
• Claim 14 describes a parallel batch method where the same chemical steps are performed in a container of water (e.g., a mixing tank) instead of a flowing stream.

These two claims share the same core inventive concept: a specific on-site generation process using a pre-mixed liquid precursor solution of hydrogen peroxide and triacetin, which is then activated by an alkali.

Obviousness Argument:
Claims 1 and 14 are arguably obvious over WIPO International Publication No. WO 01/46519 A1 (hereafter "WO '519") in view of general knowledge in the art regarding suitable acetyl precursors, such as triacetin.

1. Primary Reference: WO 01/46519 A1
   WO '519 discloses a method for generating non-equilibrium solutions of PAA on-site at the point-of-use. The process described involves:

   • Metering an aqueous solution of hydrogen peroxide into an agitated tank.
   • Co-metering a solid dry source of an acetyl precursor, tetraacetylethylenediamine (TAED).
   • Introducing aqueous sodium hydroxide (an alkali metal hydroxide) into the mixture.
   • Directing the mixture through a reactor to form PAA, which is then sent to the point-of-use.

   WO '519 teaches all the key steps of the claimed methods except for two critical differences: it uses a solid acetyl precursor (TAED) and consequently meters the precursor and the hydrogen peroxide separately rather than as a pre-mixed solution.

2. Motivation to Modify WO '519
   A POSITA would have been motivated to modify the process disclosed in WO '519 to overcome its inherent operational challenges. The '972 patent itself articulates the problem with the approach in WO '519, stating, "Disadvantages of this approach include the difficulty of accurately metering a solid and a liquid simultaneously, and the high capital equipment cost of the metering system..." (Description, Col. 5, lines 34-39).

   This known difficulty provides a clear motivation for a POSITA to seek a simpler, more reliable, and less expensive alternative. The most direct and logical solution would be to replace the solid acetyl precursor (TAED) with a liquid acetyl precursor. This modification would transform the system from a complex solid-liquid metering process into a simpler, all-liquid system, which is well known to be easier to control and less costly to implement.

3. Obvious Choice of Triacetin as the Liquid Acetyl Precursor
   The substitution of TAED with triacetin would have been an obvious choice for a POSITA for the following reasons:

   • Known Acetyl Precursor: Triacetin was a well-known acetyl precursor for generating PAA via a perhydrolysis reaction with hydrogen peroxide. The base-catalyzed perhydrolysis reaction is the same fundamental chemical mechanism used for TAED in laundry bleaching applications.
   • Physical State: Triacetin is a liquid at room temperature, directly addressing the motivation to replace the solid TAED.
   • Safety and Availability: As noted in the '972 patent, triacetin is inexpensive, non-toxic, non-corrosive, and recognized as safe (GRAS) by the FDA (Description, Col. 8, lines 2-5). These properties make it an ideal candidate for industrial applications like those described.

   A POSITA, motivated to improve the on-site generation process of WO '519, would have found it obvious to substitute the solid TAED with the known liquid acetyl precursor, triacetin, to simplify the metering process. This substitution would lead directly to the methods described in claims 1 and 14, with only routine experimentation needed to optimize flow rates and concentrations.

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Claim 20: Hydrogen Peroxide-Triacetin Composition

Summary of Claim:

• Claim 20 claims the specific liquid precursor composition itself, comprising: (a) ~23% to 40% hydrogen peroxide; (b) ~20% to 52% triacetin; (c) water; and (d) a trace amount of PAA.

Obviousness Argument:
Claim 20 is arguably obvious in light of the combination of the motivation to create a convenient precursor for an on-site generation system (like that derived from WO '519) and the teachings of prior art such as CN 107602435 A (hereafter "CN '435").

1. Motivation to Create a Pre-Mixed Composition
   Once a POSITA decided to use liquid triacetin in the on-site generation process of WO '519, the next logical step would be to devise the most efficient way to supply the liquid reactants (hydrogen peroxide and triacetin). Providing the two liquids in a single, stable, pre-mixed solution is far more convenient for storage, transport, and on-site metering than handling two separate liquid streams. This provides a strong motivation to develop the claimed composition.

2. Prior Art Teaching of Triacetin-H₂O₂ Mixtures
   The '972 patent highlights the "unexpectedly high solubility" of triacetin in hydrogen peroxide and the stability of the mixture. However, prior art demonstrated that these components could be mixed.

   • CN '435 discloses a method for preparing PAA using triacetin and hydrogen peroxide. Its examples explicitly teach mixing 10-50 parts by weight of triacetin with 10-50 parts by weight of 50% hydrogen peroxide. These ranges directly overlap with and teach the concentration ranges recited in claim 20.

   While CN '435 uses an acid catalyst to produce an equilibrium PAA solution, it teaches a POSITA that triacetin and concentrated aqueous hydrogen peroxide are miscible and can be combined to form a solution. This teaching removes the argument of "unexpectedness" regarding the ability to create such a mixture.

3. Reasonable Expectation of Success
   With the knowledge from CN '435 that the components can be mixed, a POSITA motivated to create a stable precursor for a base-catalyzed on-site system would have a reasonable expectation of success. The work required to determine the optimal concentration ranges for stability and efficacy would constitute routine experimentation, not an inventive step. The stability studies presented in the '972 patent (Tables I-VI) represent this type of routine optimization.

   Finally, the claimed "trace amount of peracetic acid" is not an inventive element but rather an inherent and unavoidable result of storing an acetyl precursor and an oxidizer like hydrogen peroxide together over time, as the patent's own data demonstrates.

Conclusion:
The methods claimed in claims 1 and 14 would have been obvious to a POSITA by modifying the on-site generation system of WO '519 with the known liquid acetyl precursor, triacetin, to solve the well-understood problems associated with metering solids. The composition of claim 20 would have been obvious from the motivation to create a convenient single-liquid feed for such a system, combined with the teaching of CN '435 that the principal components are miscible, which would have given a POSITA a reasonable expectation of success in formulating a stable product through routine experimentation.