Delivery systems for peracetic acid

Abstract

A dry to the touch delivery system for a peracetic acid composition is produced. The dry to the touch delivery system for a peracetic acid composition includes a dry powder that releases the peracetic acid quickly and completely when needed. The dry to the touch delivery system for a peracetic acid composition may be produced by combining a liquid peracetic acid or a solution of the peracetic acid composition in liquid with an inorganic solid support that is inert to the peracetic acid and is capable of adsorbing large amounts of the liquid peracetic acid or solution of the peracetic acid composition in liquid while remaining dry to the touch. The dry to the touch delivery system for a peracetic acid composition can be formulated in preparations of powders, liquids, foams, sprays, fogs, gels, ointments, creams, sticks, or pastes that can be utilized in a variety of applications

Description

[0001] DELIVERY SYSTEMS FOR PERACETIC ACID

[0002] FIELD OF THE INVENTION

[0003] A delivery system for peracetic acid is disclosed. The delivery system is prepared by combining solutions of stabilized peracetic acid with an inorganic solid material carrier. The delivery system is dry to the touch and the peracetic acid is stable for long periods of time. The peracetic acid is stabilized with a combination of stabilizers.

[0004] BACKGROUND OF THE INVENTION

[0005] Peracetic acid and solutions of peracetic acid are useful for many applications from industrial sources of oxidizers and free radicals to cosmetics and, industrial and household sanitizers. Peracetic acid solutions, typically in equilibrium with hydrogen peroxide, water and acetic acid, are generally unstable and reactive. Convenient storage and delivery has long been a challenge.

[0006] Aqueous solutions of peracetic acid are commercially available. Such solutions may be produced by reacting appropriately concentrated hydrogen peroxide and acetic acid in an aqueous medium in the presence of an acid catalyst such as sulfuric acid or other strong mineral acid. Aqueous solutions of peracetic acid represent equilibrium mixtures of the reactants and the reaction products. Concentrations of peracetic acid above 0.5% by weight for example from 0.5% to 1 % by weight, are particularly effective bactericides. Such dilute peracetic acid solutions may be produced directly by reacting acetic acid and hydrogen peroxide in a suitably dilute reaction medium.

[0007] In aqueous solution of peracetic acid, the peracetic acid is susceptible to degradation. When peracetic acid dissolves in water, upon reaction, it decomposes to hydrogen peroxide and acetic acid, which will degrade to water, oxygen and carbon dioxide. Peracetic acid degradation products are non-toxic and can easily dissolve in water. An object of the present invention is to provide a solid form of a peracetic acid that could take the form of a dry powder, pellet, tablet, bead, or brick, having long term stability. US Patent Publication No. 2020 / 0299621 discloses a delivery system for peroxide compounds wherein the peroxide compound is adsorbed by an inorganic support such as fumed silica. The present inventor discovered that peracetic acid products such as Sanidate® 5.0 or Sanidate® 12.0 (BioSafe Systems, LLC) are unstable when adsorbed on an inorganic support such as fumed silica. The present inventor discovered that peracetic products degrade very rapidly (within a few days or weeks) at ambient temperature under typical shelf life conditions, when adsorbed on an inorganic support such as fumed silica. The present inventor discovered a stabilizer package that when combined with peracetic acid and adsorbed onto a crystalline or amorphous solid material provides peracetic acid stability to the system.

[0008] The solid form of peracetic acid of the present invention would have a broad range of applications including formulations for sanitization, personal care, cosmetic, agriculture, water treatment and health care applications, to mention only a few. Peracetic acid sees broad use as a disinfectant in food handling and preparation as well as water treatment applications.

[0009] The present invention provides a technology and a process for preparing a solid form of peracetic acid. A non-liquid peracetic acid in the form of solid, powder, granules, or blocks is often desired in applications such as agrochemical and food preparation, storage and handling operations. In other applications, peracetic acid cannot be handled or delivered in a liquid form, such as in air filters or in some surface treatments, and therefore must be delivered in a solid form.

[0010] Peracetic acid is a highly effective biocide that has gained in popularity as a chlorine alternative. Increased interest is driven by several desirable characteristics of peracetic acid:

[0011] Efficacy at low concentration

[0012] - Performance at low temperature

[0013] Small dependence on pH

[0014] Relative insensitivity to organic loading, total suspended solids and the presence of ammonia, nitrite and phosphates

[0015] Ease of application

[0016] - Rapid degradation and low residual aquatic toxicity Favorable economics compared to several alternative disinfection technologies

[0017] These characteristics make a solid peracetic product highly desirable in many markets where disinfection and sustainability are important factors.

[0018] Peracetic acid is a powerful sanitizer. It has many advantages compared to chlorine based sanitizers such as sodium hypochlorite. Advantages of peracetic acid include: wide temperature spectrum, environmentally clean, no microbial resistance, etc. On the other hand, peracetic acid is well known to be less stable than solutions of hydrogen peroxide and solutions of chlorine. At room temperature, 40% solutions of peracetic acid can lose between 1 and 2% of their active ingredient per month while 30-90% solution of hydrogen peroxide can lose only 1% of their active ingredient per year.

[0019] The degradation pathways for peracetic acid will depend on several factors. In a spontaneous decomposition reaction, peracetic acid is decomposed to form acetic acid and oxygen (O2), thus representing a loss of the oxidation power. In a hydrolysis reaction, peracetic acid is hydrolyzed to form acetic acid and hydrogen peroxide. Finally, the presence of transition metals in a peracetic acid solution may catalyze decomposition to O2 and other products.

[0020] In typical commercial liquid peracetic acid formulations, the degradation is relatively slow. The hydrolysis and the spontaneous decomposition are slow unless triggered by a high pH or the presence of free radicals. The metal catalyzed degradation can be minimized by choosing the appropriate chelating agent. For example, typical commercial liquid peracetic acid solutions are relatively stable due to the presence of a stabilizing chelating agents such as HEDP (hydroxy ethylidene diphosphonic acid). HEDP is a type of organic phosphonic acid (commercially available as Dequest® 2010).

[0021] There is a long-felt need for a solid peracetic acid delivery system that can be produced with relatively cost-effective materials, using easily scaled-up, robust production methods. Further, a solid peracetic acid delivery system that has long term-stability, can be handled like a powder, can be easily mixed into a desired matrix or reaction media and is capable of delivering the peracetic compound using non-toxic materials that are safe for personal care products and additionally are not harmful to the environment has potential for large appeal. SUMMARY OF THE INVENTION

[0022] A delivery system for peracetic acid (PAA) is disclosed. The delivery system uses an inorganic solid support that is substantially inert / inert to the peracetic acid oxidation and is capable of adsorbing a considerable quantity of peracetic acid liquid solution while remaining dry to the touch. The peracetic acid itself can be a liquid or is provided in a liquid solution that is capable of being adsorbed by the inorganic solid support. A stabilizer package for the peracetic acid is included to counter the instability that arises when a liquid peracetic acid is adsorbed unto the inorganic solid support.

[0023] Various non-limiting aspects of the invention may be summarized as follows:

[0024] Aspect 1 : A dry to the touch delivery system for a peracetic acid composition comprising: an inorganic solid support, wherein the inorganic solid support is inert to the oxidation of the peracetic composition and is capable of adsorbing a liquid while remaining dry to the touch; and the peracetic acid composition, wherein the peracetic acid composition comprises an aqueous peracetic acid and a stabilizer combination comprising hydroxyethylidene diphosphonic acid and at least one of dipicolinic acid, 8- hydroxy quinoline and mixtures thereof capable of being adsorbed by the inorganic solid support; whereby the peracetic acid composition is adsorbed by the inorganic solid support, thereby forming the dry to the touch delivery system for the peracetic acid composition.

[0025] Aspect 2. The dry to the touch delivery system for a peracetic acid composition according to claim 1, wherein the inorganic solid support has a pH less than 6.

[0026] Aspect 3. The dry to the touch delivery system for a peracetic acid composition according to claim 1 wherein the inorganic solid support comprises less than 50 ppm of any individual contaminant selected from the group consisting of Al, Ca, Fe, K, Mg, Ti, and Zr. Aspect 4. The dry to the touch delivery system for a peracetic acid composition according to claim 1, wherein the inorganic solid support comprises fumed silica.

[0027] Aspect 5. The dry to the touch delivery system for a peracetic acid composition according to claim 4, wherein the fumed silica comprises hydrophilic fumed silica and the peracetic acid composition is in a liquid solution comprising peracetic acid in water.

[0028] Aspect 6. The dry to the touch delivery system for a peracetic acid composition according to claim 4 wherein the fumed silica comprises less than 50 ppm of any individual contaminant selected from the group consisting of Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, Sb, Si, Sn, Sr, Ti, V, W, Zn, and Zr.

[0029] Aspect 7. The delivery system for the at least one peroxide compound according to claim 4 wherein the fumed silica comprises less than 50 ppm of any individual contaminant selected from the group consisting of Al, Ca, Fe, K, Mg, Ti, and Zr.

[0030] Aspect 8. The delivery system for the a peracetic acid composition according to claim 4, wherein the fumed silica comprises less than 10 ppm of any individual contaminant selected from the group consisting of Al, Ca, Fe, K, Mg, Ti, and Zr.

[0031] Aspect 9. The delivery system for a peracetic acid composition according to claim 5, wherein the solution of peracetic acid in water comprises at least 0.001% by weight of the stabilizer combination for peracetic acid.

[0032] Aspect 10. The delivery system for a peracetic acid composition according to claim 1 wherein the peracetic acid composition liquid solution weight comprises at least 50% of the total delivery system weight.

[0033] Aspect 11. The delivery system for a peracetic acid composition according to claim 6 wherein the solution of a peracetic acid composition in water comprises at least up to 40% by weight of peracetic acid.

[0034] Aspect 12. The delivery system for a peracetic acid composition according to claim 6 wherein the solution of a peracetic acid composition comprises at least 70% of the total delivery system weight.

[0035] Aspect 13. A delivery system for a peracetic acid composition comprising: fumed silica, wherein the fumed silica is inert to the peracetic acid composition, is capable of adsorbing up to 70% of a liquid by weight of the delivery system while remaining dry to the touch, has a pH less than 6, and contains less than 50 ppm of any individual contaminant selected from the group consisting of Al, Ca, Fe, K, Mg, Ti, and Zr; and a peracetic acid composition wherein the peracetic acid composition is a liquid peracetic acid or is a solution of the peracetic acid composition in liquid, wherein the liquid peracetic acid or is a solution of the peracetic acid composition in liquid is capable of being adsorbed by the fumed silica and wherein the peracetic acid or is a solution of the peracetic acid composition in liquid contains at least 0.001% of a stabilizer combination comprising hydroxy ethylidene diphosphonic acid and at least one of dipicolinic acid, 8-hydroxyquinoline and mixtures thereof ; whereby up to 70% of the liquid solution of the peracetic acid composition by weight of the delivery system is combined with the fumed silica, thereby forming the delivery system for the peracetic acid composition.

[0036] Aspect 14. The delivery system for the peracetic acid composition according to claim 1, wherein the peracetic acid composition has an initial active oxygen content and wherein the peracetic acid composition retains at least 80% of the initial active oxygen content after storage for 2 months.

[0037] BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a graph of peracetic acid stability over time as described in comparative Example 3.

[0039] Figure 2 is a graph of peracetic acid stability over time as described in comparative Example 3.

[0040] Figure 3 is a graph of peracetic acid stability over time as described in comparative Example 4. Figure 4 is a graph of peracetic acid stability over time as described in comparative Example 5.

[0041] Figure 5 is a graph of peracetic acid stability over time as described in comparative Example 6.

[0042] Figure 6 is a graph of peracetic acid stability over time as described in comparative Example 7.

[0043] Figure 7 is a graph of peracetic acid stability over time as described in comparative Example 8.

[0044] DETAILED DESCRIPTION OF THE INVENTION

[0045] The solid supports useful in the invention are high purity, inorganic powders. The solid support (also called a carrier) for the liquid peracetic acid is required to be inert to the peracetic acid oxidation. As used herein, inert to peracetic acid means that the solid support does not react with the peracetic acid and is not oxidized (loss of active oxygen as measured by titration using potassium permanganate) by the peracetic acid in the delivery system. “Inert to peracetic acid” as used herein means that less than 10% of the initial active oxygen of the peracetic acid is lost upon storage of the delivery system in a sealed opaque container at ambient temperature for 2 weeks.

[0046] The peracetic acid delivery system thus provided is in a solid form and has good longterm stability. The peracetic acid delivery system remains dry to the touch as the stabilized peracetic acid solution is adsorbed onto the solid support. The delivery system is a dry to the touch material. Dry to the touch means that a 1 ply AccuWipe® brand #29712 by Georgia- Pacific absorbs less than 15% moisture by weight after being immersed in the peracetic acid delivery system for 24 hours at 23° C. The peracetic acid is easily released merely by mixing the delivery system into a desired matrix or reaction media.

[0047] The present inventor discovered that a commercial liquid peracetic acid products such as Sanidate® 5.0 and Sanidate® 12.0 become unstable when adsorbed onto a solid inorganic support comprising fumed silica. The present inventor discovered that the addition of the common HEDP stabilizer to the Sanidate® peracetic acid product did not enhance peracetic acid stability when adsorbed onto a solid inorganic support. HEDP (hydroxyethylidene diphosphonic acid) is a type of organic phosphonic acid (commercially available as Dequest® 2010). It was also discovered that the addition of a large excess of HEDP stabilizer actually made stability worse.

[0048] The pH of the solid support used in the peroxide delivery system also affects the longterm stability of the peracetic acid in the peracetic acid delivery system. Preferably, the pH of the solid support should be below 6 and most preferably below 5.5.

[0049] The present inventor discovered that select stabilizers, when blended with the HEDP stabilizer added to commercial peracetic acid solutions such as Sanidate®, provided for good stability when the peracetic acid with the stabilizer blend was adsorbed unto an organic solid support such as fumed silica.

[0050] The present inventor discovered that a stabilizer blend of HEDP with dipicolinic acid or HEPD with 8-hydroxyquinoline or mixtures thereof provided for peracetic acid stability when the combination was adsorbed onto an organic solid support such as fumed silica. Comparable stability was not provide with other known hydrogen peroxide stabilizers such as benzoic acid and sodium salicylate when combined with the HEDP in Sanidate® peracetic acid material.

[0051] As will be detailed below, extensive tests of the long term stability for peracetic acid with various stabilizer blends adsorbed upon a fumed silica organic solid support were conducted.

[0052] The delivery system for peracetic acid of the present invention comprises an inorganic solid support and a peracetic acid component comprising aqueous peracetic acid solution and a stabilizer blend. The inorganic solid support is inert to the peracetic acid component and also can adsorb a liquid while remaining dry to the touch. The peracetic acid component is a liquid peracetic acid with a stabilizer blend in a liquid solution. The liquid peracetic acid component is combined with the inorganic solid support, which forms the delivery system for peracetic acid.

[0053] The peracetic acid component contains blend of two or more stabilizers for the peracetic acid component.

[0054] The pH of inorganic solid support can be less than 6. Fumed silica is a preferred material for the inorganic support. The fumed silica may be hydrophilic fumed silica. The peroxide compound in liquid may be a solution of peracetic acid in water. The aqueous solution of peracetic acid also may contain at least one stabilizer for the peracetic acid.

[0055] The fumed silica can have less than 50 ppm of any of these individual contaminants: Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, Sb, Si, Sn, Sr, Ti, V, W, Zn, or Zr. The fumed silica may contain less than 50 ppm of any of these individual contaminants: Al, Ca, Fe, K, Mg, Ti, or Zr. The fumed silica can have less than 10 ppm of any of these individual contaminants: Al, Ca, Fe, K, Mg, Ti, or Zr.

[0056] The peracetic acid delivery system may contain hydrophilic fumed silica and a solution of peracetic acid with a blend of two or more suitable stabilizers in water. The level of peracetic acid stabilizer blend in the peracetic acid delivery system can be 0.001 % to 0.95% by weight of the delivery system for peracetic acid.

[0057] The peracetic acid delivery system has a total delivery system weight and the liquid peracetic acid in liquid solution has a liquid peracetic acid weight or a peracetic acid liquid solution weight and the weight of the peracetic acid liquid solution makes up at least 70% of the total delivery system weight. The weight of the liquid peracetic acid or the weight of the peracetic acid liquid solution can make up at least 50% of the total delivery system weight.

[0058] The stabilizers for the peracetic acid in the peracetic acid delivery system include HEDP (hydroxyethylidene diphosphonic acid) in combination with 8-hydroxyquinoline or dipicolinic acid.

[0059] An exemplary delivery system for peracetic acid is disclosed. The system comprises fumed silica. The fumed silica is inert to the peracetic acid component and has a pH less than 6. The fumed silica is capable of adsorbing up to 70% of a liquid by weight of the delivery system while remaining dry to the touch. The fumed silica also contains less than 50 ppm of any individual of these contaminants: Al, Ca, Fe, K, Mg, Ti, and Zr. The stabilizer peracetic acid component may be a liquid peracetic acid or a liquid solution of peracetic acid. The liquid peracetic acid or the liquid solution of peracetic acid is capable of being adsorbed by the fumed silica. The liquid peracetic acid or the liquid solution of peracetic acid contains at least 0.001% by weight of a stabilizer for the peracetic acid. Up to 70% of the liquid peracetic acid or the liquid solution of peracetic acid by weight of the delivery system is combined with the fumed silica, which forms the delivery system for the peracetic acid compound. The delivery system for peracetic acid can be used as an antimicrobial for indoor or outdoor use on hard surfaces. The delivery system can be used as is or combined with water or other formulations. Use sites and applications include agricultural premises, food establishments, medical facilities, food storage rooms (including cold rooms) and bathrooms. The delivery system for peracetic acid can be use in dairy and cheese processing plants, on food processing equipment, and in pasteurizers in breweries, wineries, and beverage plants. The delivery system for peracetic acid can prevent biofilm formation especially in various processes using water such as cooling tower water or irrigation systems for example. Another exemplary application may also be the treatment of ponds, retention basin, canals, lakes and all bodies of water to reduce or limit algae proliferation, pathogens proliferation, organic contamination or chemical contamination. Another exemplary application may be the remediation of soil by injecting the delivery system within a well into the ground.

[0060] The peracetic acid delivery composition may also be used for disinfection on soil (on surfaces or in furrows) and living organisms such as plants, leaves of plants, flowers, fruits and vegetables or seeds. Exemplary disinfection systems are those used to treat agrochemical diseases on plants and fruit bodies (via spraying, irrigating, dusting, fogging), in soil (via direct application to seedlings, seeds or roots) or seeds prior to planting. Another exemplary application is the treatment of produce post-harvest.

[0061] The peracetic acid delivery system may also be formulated into a cleaning composition. Exemplary cleaning systems are those that are used to clean, for instance, laundry, kitchens, or floors, or for other general cleaning purposes.

[0062] The peracetic acid delivery system may be also formulated into cosmetic compositions to be used for bleaching of skin or hair or for general antiseptic purposes.

[0063] Hair bleaching compositions can comprise the peracetic acid delivery system. Hair dye compositions also may comprise the peracetic acid delivery system.

[0064] Antiseptic compositions intended for a variety of disinfecting purposes can comprise the peracetic acid delivery system disclosed herein.

[0065] Other non-limiting examples of applications for the peracetic acid delivery system disclosed herein are any application where a peroxide would be useful, e.g. as an antiseptic for personal hygiene, for cleaning, or for bleaching laundry or teeth. The peroxide delivery system can be made into preparations of powders, liquids, foams, sprays, fogs, gels, ointments, creams, or pastes, and be tableted in various forms and shapes to be used for a variety of cleaning, stain removal and antiseptic products. Other non-limiting uses are cosmetic applications such as creams and ointments or bleaching systems for hair or skin as well as for use in hair dye compositions requiring an oxidizer; personal care such as deodorants and washing products; oral care such as tooth whitening, toothpastes, powders that can be mixed into mouthwash; cleaning applications, for instance carpet cleaning powder or powders to mix with water to make a peroxide solution; stain removal applications, such as for laundry, either for direct stain removal or formulated with laundry detergent powders; formulated into cleaning pods for laundry or dish detergent; and odor removal from rooms or refrigerators or other enclosed spaces, for instance cars.

[0066] The invention will be illustrated with a series of Examples.

[0067] Solid Support: Hydrophilic Fumed (or Pyrogenic) Silica

[0068] Fumed (also called pyrogenic) silica has a very different morphology from precipitated silica. Fumed silica products (e.g., Aerosil® from Evonik / Degussa and Cab-O-Sil® from Cabot) are characterized by an amorphous structure and a range of primary particle sizes. The primary particles do not exist in isolated form, but as aggregates and agglomerates. Fumed silica, also referred to as pyrogenic silica because it is produced in a flame, consists of microscopic droplets (the primary particles) of amorphous silica that are fused into branched, chainlike, three- dimensional secondary particles or aggregates, which then agglomerate into tertiary particles. The individual microscopic droplets are essentially non-porous. The structure of these branched, chainlike, three-dimensional secondary particles or aggregates.

[0069] Without wishing to be bound by theory, it is speculated that because the individual primary particles of fumed silica are non-porous, that upon addition of a liquid, the liquid is not absorbed inside the fumed silica particles (as one might expect for precipitated silica, which is porous) but remains on the surface of the branched, chainlike, three-dimensional secondary particles or aggregates which form larger agglomerates. Even though the agglomerates are formed of individual aggregates, one could appreciate that the intricate surface morphology of fumed silica aggregates and agglomerates should be sufficient to retain large amounts of liquid, if the liquid is able to wet the surface. Therefore, for aqueous or polar solutions of peroxide, hydrophilic fumed silica might be expected to adsorb a great deal of liquid.

[0070] Hydrophilic fumed silica can be subjected to a variety of post-treatment steps that can bind other moieties to its surface. Thus, hydrophilic fumed silica can be transformed into a fumed silica product that can be wetted by non-aqueous solutions of peracetic acid. Again, without wishing to be bound by theory, it is expected that such a treated fumed silica would similarly expected to be capable of adsorbing large amounts of a non-polar or non-aqueous solution of peracetic acid as long as the solution is capable of wetting the surface of such a surface-modified fumed silica.

[0071] The invention will be illustrated with a series of Examples as follows:

[0072] Examples

[0073] Example 1 : Preparation of peracetic acid delivery systems

[0074] Process: Commercial aqueous peracetic acid solutions (Sanidate® 5.0 and Sanidate® 12.0 available from Biosafe Systems) at a ratio of 30% silica and 70% PAA formulation were added slowly and continuously to fumed silica (Cab-O-Sil® M5) in order to distribute the solutions as uniformly as possible onto the silica carrier.

[0075] Sanidate® 5.0 is a commercial peracetic acid solution comprising 16.0 to 26.0 % w / w hydrogen peroxide; 4.2 to 6.0 % w / w peroxyacetic acid, 8.0 to 12.0 % w / w acetic acid. Sandidate® 12.0 is a commercial peracetic acid solution comprising 16.6 to 20.4 % w / w hydrogen peroxide; 10.8 to 13.2 % w / w peroxyacetic acid, 18.0 to 22.0 % w / w acetic acid. Both solutions were further stabilized with the addition of at least 600 ppm of the typical HEPD stabilizer.

[0076] The fumed silica was in the form of very fluffy powder, which has the capacity to adsorb a great deal of liquid. The liquid was added in a drop-wise manner or as a spray such that the silica powder remained dry to the touch during the application. It is anticipated that the production technique on a large scale could encompass either batch- wise mixing, or continuous or semi-batch processes. Mixing under high shear was not necessary. The powder easily adsorbed the liquid. The powder could form a few agglomerates, which easily re-dispersed when the mixture was stirred thoroughly to homogenize it. If needed, the peracetic acid delivery system product could be pushed through a sieve, e.g., 1.4 mm (14 mesh) or any size smaller or larger as needed to break lumps, if they form. The resulting peroxide delivery system was a dry to the touch, completely friable and pulverulent powder. There is no need for solvent removal or any additional steps to this process.

[0077] The silica product tested adsorbed more than its weight of liquid. The silica powder was able to easily adsorb about 2 1 / 3 times its weight of liquid, i.e., about 70% of the total weight of the peracetic acid delivery system (liquid plus silica) is the liquid portion.

[0078] After mixing as described above, the resulting solid appeared as a dry, white powder. The mixture was completely dry to the touch and the liquid did not seep out or otherwise caused the final powder to feel damp or wet even after long periods of storage. It was noted that the peracetic acid solutions would evaporate from the solid to some extent if the powders were left in unclosed containers for a period of time.

[0079] Example 2: Surface moisture on peracetic acid component delivery system

[0080] This test was developed to assess the amount of liquid, if any, present at the surface of the powder loaded with the peracetic acid solution. If free liquid were present at the surface of the powder, it would quickly be transferred to an absorbent material.

[0081] A small strip of thin paper (cut from 1 ply AccuWipe brand #29712 by Georgia-Pacific) 10 cm long by 1 cm wide, able to absorb many times its own weight in liquid was added to Cabosil® M5 silica and one strip was added to the peracetic acid delivery system loaded with 68% Sanidate® 12.0 leading to final concentration in PAA of approximately 8%. Each strip of paper was re-weighed after being immersed in the powders for 24 hours at 23 °C. Table 1 shows the average results (3 replicates) of this experiment.

[0082] As expected, due to the equilibrium between the powder and its environment, a minimal weight gain was observed when the paper strip is left in direct contact with the 68% Cab-O-Sil® M5 powder containing 68% PAA solution. Some residual powder remained on each strip. A quick air blow from a compressed air cylinder was directed at the paper strips to remove as much residual powder as possible before weighing, but it was still difficult to assess how much of the observed weight gain was due to powder sticking to the paper and how much was due to the actual moisture absorption. The paper felt completely dry after removal from the peroxide delivery system. Any moisture absorption is likely due to an equilibrium established between the paper and the peroxide delivery system.

[0083] These results show clearly that virtually no moisture is present on the surface of the peracetic acid delivery system. “Dry to the touch” is thus established to mean that a 1 ply AccuWipe brand #29712 by Georgia-Pacific absorbs less than 15% moisture by weight after being immersed in the peroxide delivery system for 24 hours at 23 degrees C.

[0084] Comparative Example 3 : Stability of Peracetic Acid on Fumed Silica

[0085] Sanidate® 5.0 and Sanidate® 12.0 (commercially available from BioSafe Systems, LLC) was added to Cab-O-Sil® M5 fumed silica (available from Cabot Corporation) at a ratio of 32% silica and 68% PAA formulation. The stability of the PAA was monitored over a period of 2.5 months by titration of the PAA and H2O2 amounts. The results are summarized in Table 2 and Figure 1. The data shows that after an initial vague plateau of about one month, more than 40% of the PAA degraded in less than 2 months of storage at room temperature (23 degrees C).

[0086] The following formulations were tested:

[0087] KFD-20-04: formulation with Sanidate® 5.0. Initial PAA concentration: 3.5% A & B are repeat.

[0088] KFD-20-05: formulation with Sanidate® 12.0. Initial PAA concentration: 8.4%

[0089] A & B are repeat.

[0090] Table 2. Data of Figure 1

[0091] Days Time (month)

[0092] A repeat of these experiments (with only Sanidate® 12.0) was done with multiple samples in order to confirm the degradation. The replicates confirmed the one-month plateau before the formulations started quickly degrading. In some instance, it is necessary to sieve the powder to insure a maximum particle size that might be required for a specific application. This operation is usually carried out using a typical ASTM metal sieve. The results are summarized in Table 3 and Figure 2. The PAA degradation is particularly marked in the formulation that was sieved with a metal sieve - leading to the belief that metal degradation pathways might be a culprit in the observed rapid degradation. In sample KFD-20-09 a large excess of Dequest® 2010 LC was added (1% or 10,000 ppm) to evaluate the impact of additional metal chelating agents on PAA stability. Not only did the addition of a large amount of HEDP not improve PAA stability, the stability actually was made worse.

[0093] The following samples were tested:

[0094] KFD-20-09- Extra HEDP (+ 1%) Dequest 2010LC - Initial PAA cone. 8.32%

[0095] KFD-20-10A Repeat of KFD-20-05 (no sieving) KFD-20- 10B Repeat of KFD-20- 10A (no sieving)

[0096] KFD-20-10C same as KFD-20-10A with sieving (metallic sieve)

[0097] Initial PAA cone. KFD-20-10 samples: 8.40%

[0098] Table 3. Data of Figure 2.

[0099] Comparative Example 4: Stability of Peracetic Acid on Fumed Silica with Stabilizer Combination

[0100] The stability of several formulations - in which, in addition to the HEDP initially added to Sanidate® 12.0, the following stabilizers were added:

[0101] HEPD 600 ppm (control)

[0102] Sodium salicylate

[0103] Benzoic acid

[0104] - Dipicolinic acid

[0105] 8-hydroxy quinoline

[0106] The target concentration was 1000 ppm (or 0.1%) of additional stabilizer.

[0107] In each graph, the two curves represent PAA and hydrogen peroxide concentrations over time. Hydrogen peroxide is always present (part of an equilibrium with PAA). Hydrogen peroxide titration was included in the protocol because hydrogen peroxide auto-titration is more precise and sensitive than the manual titration of PAA. It gives an accurate snapshot of the degradation rate. The stability was followed over a period of two months.

[0108] Solid PAA formulation have the following ratio:

[0109] 80 g Silica Ratio: 32 / 68

[0110] 170 g PAA 12,0 with stabilizer: 169.83 g Sanidate® 12.0

[0111] 250 g Total 0.17 g stabilizer 170.00 g

[0112] Following blending, the formulations were kept at ambient temperature (23°C) in HDPE bottles in the laboratory. Table 4 shows the results of stability testing of Sanidate® 12.0 containing 600 ppm of HEDP. The results are also set out in Figure 3. The results show that when PAA stabilized with HEPD was adsorbed on fumed silica, approximately 41% of the PAA was lost in less than 2.5 months. Table 4: data for Figure 3.

[0113] Example 5: Stability of Peracetic Acid with Additional Stabilizers on Fumed Silica

[0114] Table 5 shows the results of stability testing of Sanidate® 12.0 containing 600 ppm of HEDP with the addition of 1000 ppm of benzoic acid. The results are also set out in Figure 4. The data shows that when PAA stabilized with HEPD was treated with 1000 ppm of benzoic acid and adsorbed on fumed silica, approximately 10.6% of the PAA was lost in less than 2.5 months.

[0115] Table 5: data for Figure 4.

[0116]

[0117] Comparative Example 6: Stability of Peracetic Acid on Fumed Silica with Stabilizer Combination

[0118] Table 6 shows the results of stability testing of Sanidate® 12.0 containing 600 ppm of HEDP with the addition of 1000 ppm of sodium salicylate. The results are also set out in Figure 5. The data shows that when PAA stabilized with HEPD was treated with 1000 ppm of sodium saliclylate and adsorbed on fumed silica, approximately 14.2% of the PAA was lost in less than 2.5 months.

[0119] Table 6: data for Figure 5.

[0120]

[0121] Example 7: Stability of Peracetic Acid on Fumed Silica with Stabilizer Combination

[0122] Table 7 shows the results of stability testing of Sanidate® 12.0 containing 600 ppm of HEDP with the addition of 1000 ppm of dipicolinic acid. The results are also set out in Figure 6. The data shows that when PAA stabilized with HEPD was treated with 1000 ppm of dipicolinic acid and adsorbed on fumed silica, essentially no PAA was lost in more than two months. The slight increase observed might be due to a slightly underestimated concentration at time zero, some evaporation or a rebalancing of the equilibrium between PAA and hydrogen peroxide.

[0123] Table 7: data for Figure 6.

[0124]

[0125] Example 8: Stability of Peracetic Acid on Fumed Silica with Stabilizer Combination

[0126] Table 8 shows the results of stability testing of Sanidate® 12.0 containing 600 ppm of HEDP with the addition of 1000 ppm of 8-hydroxy quinoline. The results are also set out in Figure 7. The data shows that when PAA stabilized with HEPD was treated with 1000 ppm of 8-hydroxy quinoline and adsorbed on fumed silica, essentially no PAA was lost in more than two months. The slight increase observed might be due to some evaporation or a rebalancing of the equilibrium between PAA and hydrogen peroxide.

[0127] Insert Table 8: data for Figure 7.

[0128]

[0129] The testing show that PAA with HEDP as a stabilizer is unstable when adsorbed on fumed silica. Both PAA and hydrogen peroxide curves (Figure 3) show a definite loss in active ingredient over time.

[0130] Adding the known stabilizers benzoic acid or sodium salicylate to the PAA formulation containing HEDP did not help with the stability. While the PAA degradation appears to slow down (Figures 4 and 5), it still degrades at a rate that is not commercially acceptable.

[0131] The results obtained with HEDP and the addition of DPA and 8-hydroxyquinoline (Graphs 6 and 7 respectively) show a much-improved stability for over 2 months for both PAA and hydrogen peroxide. Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.

Claims

What is claimed is:

1. A dry to the touch delivery system for a peracetic acid composition comprising: a) an inorganic solid support, wherein the inorganic solid support is inert to the oxidation of the peracetic composition and is capable of adsorbing a liquid while remaining dry to the touch; and b) the peracetic acid composition, wherein the peracetic acid composition comprises an aqueous peracetic acid and a stabilizer combination comprising hydroxyethylidene diphosphonic acid and at least one of dipicolinic acid, 8- hydroxy quinoline and mixtures thereof capable of being adsorbed by the inorganic solid support; whereby the peracetic acid composition is adsorbed by the inorganic solid support, thereby forming the dry to the touch delivery system for the peracetic acid composition.

2. The dry to the touch delivery system for a peracetic acid composition according to claim 1, wherein the inorganic solid support has a pH less than 6.

3. The dry to the touch delivery system for a peracetic acid composition according to claim 1 wherein the inorganic solid support comprises less than 50 ppm of any individual contaminant selected from the group consisting of Al, Ca, Fe, K, Mg, Ti, and Zr.

4. The dry to the touch delivery system for a peracetic acid composition according to claim 1, wherein the inorganic solid support comprises fumed silica.

5. The dry to the touch delivery system for a peracetic acid composition according to claim 4, wherein the fumed silica comprises hydrophilic fumed silica and the peracetic acid composition is in a liquid solution comprising peracetic acid in water.

6. The dry to the touch delivery system for a peracetic acid composition according to claim 4 wherein the fumed silica comprises less than 50 ppm of any individual contaminant selected from the group consisting of Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, Sb, Si, Sn, Sr, Ti, V, W, Zn, and Zr.

7. The delivery system for the at least one peroxide compound according to claim 4 wherein the fumed silica comprises less than 50 ppm of any individual contaminant selected from the group consisting of Al, Ca, Fe, K, Mg, Ti, and Zr.

8. The delivery system for the a peracetic acid composition according to claim 4, wherein the fumed silica comprises less than 10 ppm of any individual contaminant selected from the group consisting of Al, Ca, Fe, K, Mg, Ti, and Zr.

9. The delivery system for a peracetic acid composition according to claim 5, wherein the solution of peracetic acid in water comprises at least 0.001% by weight of the stabilizer combination for peracetic acid.

10. The delivery system for a peracetic acid composition according to claim 1 wherein the peracetic acid composition liquid solution weight comprises at least 50% of the total delivery system weight.

11. The delivery system for a peracetic acid composition according to claim 6 wherein the solution of a peracetic acid composition in water comprises at least up to 40% by weight of peracetic acid.

12. The delivery system for a peracetic acid composition according to claim 6 wherein the solution of a peracetic acid composition comprises at least 70% of the total delivery system weight.

13. A delivery system for a peracetic acid composition comprising: a) fumed silica, wherein the fumed silica is inert to the peracetic acid composition, is capable of adsorbing up to 70% of a liquid by weight of the delivery system while remaining dry to the touch, has a pH less than 6, and contains less than 50 ppm of any individual contaminant selected from the group consisting of Al, Ca, Fe, K, Mg, Ti, and Zr; and b) a peracetic acid composition wherein the peracetic acid composition is a liquid peracetic acid or is a solution of the peracetic acid composition in liquid, wherein the liquid peracetic acid or is a solution of the peracetic acidcomposition in liquid is capable of being adsorbed by the fumed silica and wherein the peracetic acid or is a solution of the peracetic acid composition in liquid contains at least 0.001% of a stabilizer combination comprising hydroxy ethylidene diphosphonic acid and at least one of dipicolinic acid, 8- hydroxyquinoline and mixtures thereof ; whereby up to 70% of the liquid solution of the peracetic acid composition by weight of the delivery system is combined with the fumed silica, thereby forming the delivery system for the peracetic acid composition.

14. The delivery system for the peracetic acid composition according to claim 1, wherein the peracetic acid composition has an initial active oxygen content and wherein the peracetic acid composition retains at least 80% of the initial active oxygen content after storage for 2 months.

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