High pressure treated architectural coating compositions and methods for high pressure treating architectural coating compositions

Abstract

Disclosed herein are methods of pasteurizing or sterilizing architectural coating compositions using high pressure processing (HPP) with or without heat, radiation or other energy source without the need to additionally polymerize the compositions, and methods of storing them.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to architectural coatings, including, but not limited to, paints and stains, that have been pasteurized or sterilized by high pressure treatment to remove or substantially reduce the level of bacteria, fungi, yeast, and / or other biological agents in the architectural composition, and to methods of pasteurizing or sterilizing the same. BACKGROUND

[0003] For environmental and health concerns, there has been a movement to reduce the amount of volatile organic compounds (VOCs) in paints, stains, and other architectural coating compositions that evaporate into the environment after the paint film is formed. Paint additives that promote or impart desirable paint properties, such as better film coalescence, better anti-blocking, better film durability, better physical and chemical scrub resistance, and tougher coatings, among others, also contain VOCs. The evaporation of VOCs often produces undesirable odors, and exposure to such fumes remains a health concern, especially in poorly ventilated areas. Thus, low- or non-volatile additives that impart comparable (or superior) properties to paints and stains have been used in place of higher VOC additives. An article in the New York Times newspaper entitled "The Promise of Green Paint" discusses the search for low VOC paints or better "green paints" (Kershaw, Sarah, The New York Times, May 15, 2008, page F6, which is incorporated herein by reference in its entirety).

[0004] However, the reduction of VOCs in paints, stains, and other architectural coatings, and in additives, has resulted in environmentally friendly paints that are more susceptible to the growth of bacteria, algae, yeast, fungi, and other biological agents that thrive in aqueous environments. These biological agents grow and die in paint cans and containers, and often emit unpleasant odors and render the paint unusable for its intended purpose, and can cause viscosity reduction, discoloration, gassing, blistering, settling, and pH changes. Biological agents also present potential health concerns. Certain biological agents, such as algae and mold, can grow on dried paint films covering walls or other substrates.

[0005] Biocides have been used in aqueous paints or stains to control biological agents within the can and container. Some biocides can remain on dried paint films to control algae and mold. However, it is desirable to minimize the level of biocide in aqueous paints / stains or dried paint / stain films, while preventing unimpeded growth of biological agents.

[0006] Pasteurization of paints and stains has been attempted. U.S. Patent No. 5,529,749 to Rinno et al. teaches the use of dielectric heating, particularly microwaves, to reduce microbial counts in paint compositions. Rinno further teaches that sterilization of paint compositions by direct heating to 80°C - 121°C, even for short periods of time, will produce coagulation or additional cross-linking in the paint composition. Rinno further teaches that sterilization of paint compositions by gamma rays produces hydrogen peroxide and hydroxyl radicals and results in premature cross-linking of the polymers in the paint. Rinno concludes that direct heating and gamma rays are not suitable for industrial sterilization of paint compositions.

[0007] U.S. Patent No. 10,639,386 to Sheerin et al., commonly owned, contradicts the conclusions of Rinno. Sheerin teaches, through experimentation, that successful pasteurization or sterilization of paint and stain compositions can occur at significantly lower temperatures, e.g., from about 49°C to about 72°C (120°F to 162°F), for at least 120 minutes to at least 2 minutes, respectively. Sheerin further teaches, through experimentation, that gamma rays can successfully pasteurize paint compositions at less than about 15 kGys without further polymerizing or cross-linking the latex polymers in the paint.

[0008] The following biological agents can be found in paints:

[0009] i. Bacteria: Pseudomonas species, including Pseudomonas aeruginosa; gram-negative rod-shaped bacteria; Enterobacter aerogenes; Sphingomonas paucimobilis; other gram-positive and gram-negative species, etc.

[0010] ii. Yeast: Candida lambica and Yarrowia lipolytica, etc.

[0011] iii. Fungi (mold): Aspergillus species, Acremonium species, Geotrichum species, and Penicillium species, etc.

[0012] In some embodiments or experiments discussed by Sheerin, an inoculum containing the biological agents listed above was introduced into a paint or paint container and the biological agents were allowed to grow. Thereafter, the paint was pasteurized by heat or gamma rays and the paint was retested to determine the residual concentration of biological agents, if any, and whether the paint remained functional. In other embodiments or experiments, commercially available paints having biocides defeated by one or more known biological agents were pasteurized and retested to determine whether the contaminated paint could be restored to commercial condition and suitable for sale.

[0013] Pseudomonas aeruginosa or P. aeruginosa was found in some contaminated paints. This bacterium is commonly found in moist and warm environments, such as swimming pools and hot tubs. Researchers at the School of Medicine and Public Health have reported that P. aeruginosa can grow in a range of 25°C to 42°C, but can be killed at temperatures of 60°C for about 30 minutes and up to 70°C. P. aeruginosa does not grow at temperatures of 10°C up to 15°C or 20°C, but does not die. These results are reported by A. Tsuji, Y. Kaneko, K. Takahashi, M. Ogawa, and S. Goto, “The Effects of Temperature and pH on the Growth of Eight Enteric and Nine Glucose Non-Fermenting Species of Gram-Negative Rods”, Toho University School of Medicine, Department of Microbiology, Microbiol. Immunol, Vol. 26(1), 15-24, 1982, pp. 15-24, which is incorporated by reference in its entirety.

[0014] Tsuji et al. also reported the effects of heat on the following bacteria.

[0015] Table 1

[0016]

[0017] (E. is Escherichia; K. is Klebsiella; S. is Serratia; P. is Pseudomonas; A. is Acinetobacter; F. is Flavobacterium)

[0018] = survived at least 6 hours; survival tests were performed at 10-70°C in 10°C increments.

[0019] 1 = Survived at 50°C for about 1 hour.

[0020] 2 = Survived at 50°C for about 4 hours.

[0021] 3 = Survived at 50°C for about 2 hours.

[0022] = Growth test at 10-50°C and recorded time to grow from an initial concentration of 10 2 cells / ml to 10 7 cells / ml; observed bacterial growth for 48 hours.

[0023] All tested bacteria were eradicated at 60°C or 70°C for 30 minutes. No bacteria survived at 60°C for more than 2 hours. No bacteria survived at 70°C for more than 30 minutes.

[0024] All tested bacteria survived at 10°C but did not grow. Otherwise, they grew at the reported temperature ranges and peak or optimal growth temperatures would also be reported.

[0025] Tsuji et al. also reported that pH 6.4 to 8.2 had little effect on the growth rate of these bacteria. However, S. Bricha, K. Ounine S. Oulkheir, N. E. El Haloul and B. Attarassi, “Heat Resistance of Pseudomonas Aeruginosa in Preparations at the Base of Cucumber, Tomato and Lettuce as Affected by pH and Sodium Chloride”, Ibn Tofail University, Morocco, ISPROMS ISSN: 1994-5108, WJBR Vol. 3, No. 1, pp. 1-8, reported that at a pH of about 2, heat resistance of one strain of P. aeruginosa was reduced at temperatures of 63°C, but heat resistance of P. aeruginosa was roughly the same at pH of 4.5 and 6. Bricha et al. also reported that at low pH, 2-6% sodium chloride salt can protect the bacteria. Bricha et al. is incorporated by reference in its entirety.

[0026] Yeast cells begin to die at temperatures above 50°C, and most will die at temperatures of about 55°C to about 60°C. Bakers know that yeast added to water that is too hot will be killed and the dough will not rise. At temperatures of 10°C or less, yeast will not grow. Yeast grows in a temperature range of about 27°C to about 32°C, depending on the species. Thus, yeast has a similar dormancy-growth-death temperature profile as the bacteria discussed above. Therefore, yeast can be eradicated and / or controlled by the heating methods described in Sheerin, including storage and transport.

[0027] Mold (including mildew, fungus, and common mold) exists in the same temperature range (and relative humidity) that supports human life. Thus, mold and mold spores are ubiquitous in our environment. Mold can grow at temperatures between 4°C and 38°C (40°-100°F). Below 4°C, mold is in a dormant state, and when the temperature is raised and at the proper relative humidity, mold will revive. Some molds tolerate temperatures as high as 38°C or more. Several dormancy-growth-death temperature states have been reported for mold and spores, as follows. See http: / / www.thermapure.com / environmental-services / mold / .

[0028] Table 2

[0029]

[0030]

[0031] While the lethal temperature for some of the molds discussed above is slightly higher than 60°C, the duration of the kill is much shorter. At 60°C but for a longer duration, most molds can be killed. Thus, mold can be eradicated and / or controlled by the same heating methods described in Sheerin.

[0032] As taught by Rinno and Sheerin, which are incorporated by reference in their entirety, pasteurization or sterilization of paint and stain compositions by various methods is unpredictable. Detailed analysis and experimentation are necessary to determine the efficacy of any pasteurization technique. High pressure processing (HPP), also known as pascalization, bridgmanization, or cold pasteurization, has been used to pasteurize certain foods and beverages. However, its use in pasteurization of paint and stain compositions has not been recognized, and it is not known whether HPP would have a negative impact on architectural compositions, such as coagulation or additional crosslinking of latex polymers.

[0033] Accordingly, there remains a need for additional sterilization or pasteurization techniques for architectural compositions, such as paints and stains. SUMMARY

[0035] Accordingly, the present invention relates to a method of pasteurizing paint with high pressure, with or without an energy source such as heat, to kill any agents that can have been introduced into the paint.

[0036] One embodiment of the present invention relates to a method of reducing biological agents in an architectural coating composition, comprising the steps of:

[0037] (i) preparing the architectural coating composition; and

[0038] (ii) applying a pressure source of from about 50 MPa to about 1,000 MPa, preferably from about 300 MPa to about 700 MPa, or from about 400 MPa to about 700 MPa, or from 450 MPa to about 650 Mpa, to the architectural composition for a duration of up to about 10 minutes, preferably from about 1 to about 5 minutes, or from about 3 to about 5 minutes, or from about 2 minutes to about 4 minutes, or from about 2.5 minutes to about 3.5 minutes, to sufficiently reduce the biological agents.

[0039] Preferably, the architectural composition is stored in a flexible container prior to step (ii). The headspace, if present, in the container should be less than about 10%, preferably less than about 5% or less than about 2.5% of the volume of the flexible container.

[0040] Preferably, the flexible container is made of a material selected from polyethylene terephthalate (PET), amorphous PET (APET), crystalline PET (CPET), high density polyethylene (HDPE), low density polyethylene (LDPE), or polypropylene (PP).

[0041] The flexible container can have a film seal, which is preferably made of PP, PE, HDPE, PP, or other materials.

[0042] Optionally, the method of reducing biological agents further comprises a heating step, either simultaneously with or sequentially to step (ii).

[0043] Optionally, the method of reducing biological agents further comprises a second pressure treatment step. The second pressure treatment step can be at the same pressure and duration as those in step (ii). Alternatively, the second pressure treatment step can be at a different pressure and / or duration than those in step (ii).

[0044] Optionally, the method can also include the step of adding a biocide or antimicrobial component to the architectural composition, preferably in a lower amount than the untreated or non-pasteurized architectural composition.

[0045] Preferably, the eradication is at least a 3-log (99.9%) reduction, preferably a 4-log (99.99%) reduction and more preferably a 5-log (99.999%) or greater reduction. BRIEF DESCRIPTION OF DRAWINGS

[0047] The same reference numerals in the figures indicate the same parts:

[0048] Figures 1(a)-1(c) are flow curves of three commercially available paints, with and without HPP treatment, in log-log scale of viscosity (Y-axis, Pascal seconds, or Pa-s) of the paint sample as a function of applied shear rate or shear stress (X-axis, seconds -1 ).

[0049] Figure 2 A perspective view of an exemplary one-way flow valve is shown.

[0050] DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0051] The one or more paints used herein include waterborne or water-based paint compositions, stains or other architectural compositions. Architectural compositions also include materials understood in the art to be architectural compositions, such as adhesives, caulks, asphalt and the like. The pasteurization or sterilization techniques described herein utilizing HPP are applicable to all architectural compositions. Paint film refers to paint or stain that has been applied to a surface or substrate and dried or the latex particles in the paint have cross-linked to form a film.

[0052] As discussed above, water-based latex architectural coatings, such as paints, stains, other household and industrial coatings, have become more environmentally friendly. This means that modern architectural coatings have less VOC content and have additives and stains that also contain low VOC. The reduction in VOC has made architectural coatings more susceptible to biological factors, such as bacteria and fungi in the aqueous phase and algae and certain fungi, e.g., mold, in the dried film phase. One solution is to add a biocide to the architectural coating at the latex formation stage, the pigment dispersion stage, where the pigments are dispersed with surfactants, dispersants and water, and / or the letdown stage, where the waterborne latex, pigment dispersion and additives are combined. The paint is then put into cans and containers for storage and transportation. At a later time, stains, which can contain their own biocide, are added in the retail store to obtain the paint color that the consumer purchases.

[0053] While biocides can be used to protect paints and other architectural coatings and can be used in dried paint films to help prevent the growth of biological agents, some environmentally conscious consumers have expressed a desire for paints that are free of biocides or have reduced biocides. However, without biocides or with reduced biocides, biological agents will proliferate in the paint or paint film.

[0054] As reported by K. Considine, A. Kelly, G. Fitzgerald, C. Hill, and R. Sleator, "High-pressure Processing - Effects on Microbial Food Safety and Food Quality", FEMS Microbiol. Lett. 281 (2008), 1-9, which is incorporated herein by reference in its entirety, high pressure processing (HPP) (also known as "cold pasteurization") has been used to pasteurize certain foods. In the food industry, HPP is typically carried out at between 50 MPa to 1,000 MPa (about 7,250 psi to about 145,000 psi, or 500 bar to 10,000 bar), or more commonly between 300 MPa to 700 MPa, for durations of a few seconds to a few minutes (e.g., about 10 minutes or less), or more commonly about 1 minute to about 5 minutes, preferably 3 minutes to 5 minutes. HPP typically causes a modest temperature increase (5-15 °C) by adiabatic heating, and the temperature returns to its original temperature after decompression.

[0055] Different microbial organisms respond to HPP with varying degrees of resistance, and HPP sensitivity can vary significantly between bacterial species. In pathogenic bacterial strains, viability loss can vary from 0.5 log to 8.5 log. Generally, prokaryotic cells, including bacteria, tend to be more pressure-resistant than eukaryotes. Morphology also plays a role, reflected in the fact that cocci are more resistant than rod-shaped bacteria. In addition, some bacteria such as Clostridia and Bacilli tend to form endospores when subjected to pressure. Endospores tend to be highly resistant to HPP and can tolerate treatments exceeding 1,000 MPa. Spores of Clostridia are generally more pressure-resistant than spores of Bacilli.

[0056] HPP at lower pressures can induce germination of bacterial spores; interestingly, these spores were found to be more sensitive to subsequent pressure treatments. Simultaneous or sequential combinations of HPP with heat or pressure cycling treatments have achieved some degree of spore inactivation. Gram-positive bacteria are more heat- and pressure-resistant than Gram-negative bacteria. The efficacy of microbial reduction depends on a variety of factors, such as the bacterial species, the number of treatment cycles, the pH, the pressure, the treatment time, and the temperature.

[0057] Yeast and molds are relatively sensitive to HPP, but the ascospores of thermotolerant molds (e.g., Trichoderma, Neosartorya, and Talaromyces) are highly resistant to HPP. Viruses vary greatly in their pressure resistance.

[0058] Ca 2+ Ions and other cations protect E. coli from HPP as well as high sucrose; NaCl and CaCl2protect B. coagulans better than non-ionic solutes such as sucrose and glycerol. Low pH in the suspending medium can make certain pathogens more sensitive to HPP. On the other hand, HPP can be less effective on low acid materials because the low acidity will preserve the spores unless heat is applied. The pH of an acidic solution can reversibly decrease with increasing pressure, but recover during decompression. Because HPP can not kill the spores, bacteria can come back.

[0059] Treatment at temperatures below ambient (e.g., at refrigeration levels) can enhance HPP, and can achieve lower microbial numbers than HPP at 25°C (77°F) or room temperature. Similarly, using HPP in combination with mild heat treatment can yield better results than either method used alone. In one reported example, pressure resistant E. coli was inactivated in a 400 MPa and 50°C HPP treatment for 15 minutes. Neither treatment alone achieved the reported inactivation (5-6 log reduction). By first treating with low HPP and then applying a relatively mild heat treatment, bacterial spores can be inactivated (see, e.g., J. Food Prot. 2013, 76(3), pp. 448-55).

[0060] Without being bound to any particular theory, pressure treatment induces changes in bacterial cells, including inhibition of enzyme and protein synthesis, and changes in cell morphology and cell membranes. Pressure treatment also disrupts processes such as transcription, translation, and cellular functions responsible for survival and reproduction. Bacterial membrane damage can cause leakage of cellular material across the inner and outer membranes, and handling of nutrients and cellular waste.

[0061] HPP can be combined with other antimicrobial agents, including, but not limited to, lacitin 3147, lactoperoxidase, and nisin, which are commonly used in food. HPP can also be used with antimicrobial agents commonly used in paints and colorants.

[0062] One aspect of the present invention is the pasteurization or sterilization of paints, stains and other architectural coatings (such as adhesives, caulks, etc.) to avoid or limit the growth of biological agents in the absence of or with reduced biocides. In a preferred embodiment, architectural compositions such as paints and stains are high pressure pasteurized during or after manufacture with or without an energy source, preferably heat or radiation sources including, but not limited to, gamma rays, infrared, ultraviolet, electron beam and microwave radiation, to significantly reduce the number of biological agents present, if any, in the architectural composition. Preferably, the paints, stains and other architectural compositions are stored in flexible containers that preferably can transmit high pressure to the compositions contained therein. These containers can be quart, pint, gallon or 5-gallon liners or flexible containers that can be sold to the consumer or optionally stored in substantially rigid containers that are sold to the consumer. In a preferred embodiment, the containers are large liners made of flexible materials, for example, 20-gallon or 50-gallon capacity, and the HPP treated architectural coatings are transferred to smaller containers to be sold to the consumer. These paint containers are then stored until sold to the consumer. In most cases, the paint containers are shipped to paint distribution centers and stored and then shipped and stored at retail stores before purchase by the consumer. One advantage of storing pasteurized architectural compositions in flexible containers is that the consumer more easily mixes the paint or stain by rolling, rotating or squeezing the flexible container before use.

[0063] HPP resistant containers used in the food industry can be used as HPP resistant paint / stain containers. Preferably, these containers are sized to hold the volume of paint / stain that is typically sold to the consumer, for example, pint, quart, gallon, etc. The HPP containers should have reliable seals to prevent pressurized water / liquid from entering the container and should be made of flexible, durable materials to withstand the extreme pressures encountered during HPP treatment. Preferably, the air pockets within any HPP container are minimized, preferably to less than about 10% of the total volume and preferably less than about 5% or less than about 2.5%. Typical HPP resistant containers can be bottles with a film seal / cap, bags, cups / tubs / trays with a top film seal, or vacuum bags. Suitable flexible, durable materials include, but are not limited to, polyethylene terephthalate (PET), amorphous PET (APET), crystalline PET (CPET), high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP). Suitable film seal materials include, but are not limited to, PP, PE, HDPE, PET, etc.

[0064] HPP does not break covalent bonds, but only affects non-covalent or physical bonds, such as ionic and hydrogen bonds and hydrophobic interactions. Latex particles or latex resins that form a paint film are primarily formed by covalent bonds, and thus are not expected to be degraded by HPP. However, high pressure can theoretically lead to a loss of colloidal stability, and subsequent irreversible coagulation. In addition, some rheology modifiers, such as thickeners and surfactants, interact with the latex resin through hydrophobic interactions and hydrogen bonds. Thus, HPP can affect the viscosity of architectural compositions, which can reduce the performance of paints and stains and other architectural compositions.

[0065] As further described below, 12-ounce HPP-resistant juice bottles were filled with three commercially available paints: Commercial 1 (a deep base primer), Commercial 2 (a 1-base paint with a flat finish), and Commercial 3 (a 4-base paint with a semi-gloss finish), and subjected to HPP treatment at 86,587 psi (597 MPa) for 3 minutes at 52°F. The standard HPP treatment for food is 85,000 psi (586 MPa) for 3 minutes. The rheological properties of these HPP-treated commercial paint samples were compared to untreated samples or controls, and the results are shown in FIGS. 1(a)-(c). The flow curves were plotted on a log-log scale of the viscosity (Y-axis, Pascal seconds) of the paint samples as a function of the applied shear rate or shear stress (X-axis, seconds -1 ). Viscosity quantifies the resistance of the composition to flow. Shear rate is the change in strain with time. The viscosity of the samples was measured at different shear rates (rotation speeds) (horizontal axis). Low rotation speeds mimic the stage when the paint is in a substantially static condition. At this stage, high viscosity is desirable, indicating low color flow and low color separation. High rotation speeds mimic the stage when the user is applying the paint to a surface, for example, moving a paintbrush or roller. At this stage, low viscosity is desirable, indicating easier application. FIGS. 1(a)-(c) show that the flow curves of all three paint samples were essentially the same between the HPP-treated samples and the untreated control samples. The results indicate that paints and stains can be treated with HPP without loss of physical properties (e.g., rheological properties) and performance.

[0066] The static viscosity (viscosity within the paint can) of these commercial paint samples and HPP-treated samples was also measured, as shown in Table 3 below.

[0067] Table 3.

[0068]

[0069] As shown, the Stormer and ICI viscosities of the HPP treated samples were very close to the untreated samples, indicating that HPP treatment had no significant effect on the viscosity of the paint, from which it can be inferred that HPP treatment did not significantly affect the physical bonds of the thickening agents, surfactants, or other rheology modifiers used in commercially available paints.

[0070] In another experiment, about 2 gallons of paint (a 4-base paint with a semi-gloss finish) was inoculated with a combination of microbial species (see Table 4). The inoculated paint was placed in a 12-ounce HPP-resistant juice bottle.

[0071] Most samples were treated with HPP at 86,587 psi and at 52°F for 3 minutes, while some samples were untreated and held as controls. Two of these samples were tested for biological activity, one sample being an HPP treated sample and the other sample being an untreated control. Both samples had about 0.5 inches of headspace. The amount of headspace is believed to be a factor in HPP treatment because it takes more time to compress the air in the headspace and, therefore, can result in an increase in treatment time.

[0072] Table 4

[0073]

[0074]

[0075] Biological activity results for HPP treated paint samples relative to untreated control paint samples are shown in Tables 5(a)-(b). Aerobic Plate Count (APC) is an indicator of the number of bacteria on a sample and is measured in "cfu / g," which stands for colony forming units per gram of sample. APC assumes that each cell forms one visible colony when mixed with agar containing appropriate nutrients. It is a general test for organisms that grow aerobically or require oxygen at moderate or mesophilic temperatures (25-40°C or 77-104°F).

[0076] The APC results in the tables below were obtained by mixing 1 gram of product with 9 ml of phosphate buffered saline (PBS) as a diluent to a 1 : 10 dilution. 1.0 ml of the resulting mixture was plated on two plates. Trypticase soy agar (TSA) was poured into one dish and sab dextrose (SAB) was poured into the other dish. TSA will grow bacteria and SAB will grow yeast and molds, although some gram negative bacteria will also grow in SAB agar.

[0077] Count the colonies growing on the plate, remembering that a factor of 1 : 10 needs to be applied because the sample was diluted. For example, 5 colonies counted equals 50 colonies present per gram of the original product sample.

[0078] The control sample (no HPP treatment) was plated with multiple dilutions because the initial growth was too dense to count; therefore, the dilutions allowed for accurate counting of the original sample.

[0079] Table 5(a)

[0080]

[0081]

[0082] Table 5(b)

[0083]

[0084] APC does not accurately indicate the type of bacteria present; it is a quantitative test. This is the reason for using the enrichment test, which is a qualitative test; 10 grams of product is added to a jar containing 90 mL of Letheen broth and the mixture is incubated for 48 hours. Next, differential media is used, where each indicates a specific bacteria by changing the color of the media or the color of the growth on the media. The media used is specific for E. coli, S. aureus, P. aeruginosa, and Salmonella. A loop is used to add one drop of broth to each media.

[0085] The analysis shows that the APC was reduced from 1,270,000 cfu / g before HPP treatment to about 30 cfu / g remaining, which represents a near 5-log reduction (99.998%) in bacterial colonies. Preferably, the eradication is at least a 3-log (99.9%) reduction, preferably a 4-log (99.99%) reduction, and more preferably a 5-log (99.999%) or greater reduction. The residual bacterial count in the HPP treated sample was identified as Gram-positive (Gram+) bacteria. The Gram+ bacteria can be contamination introduced by the sample handling, as the enrichment test was S. aureus negative, which is the only Gram+ species present in the mixture of microorganisms used as inoculum. Furthermore, no Gram+ bacteria were detected in the control / no HPP treated sample.

[0086] Therefore, the above experiments show that (i) paint and colorant compositions and other architectural compositions can be treated with HPP and retain their functionality, and (ii) HPP treatment can reduce the bacterial count in paint and colorant compositions to a 5-log reduction.

[0087] According to another embodiment of the present invention, a paint container suitable for HPP is able to add tint to the treated paint within the container. Commonly owned U.S. 9,994,722 discusses that a one-gallon (128-ounce) paint can can reserve up to 24 ounces of free space for tint. This represents about 18.75% of air space. As discussed above, for this amount of free space, HPP treatment takes longer and is more expensive. In this embodiment, a flexible or elastic bag or pouch is partially filled and due to its flexibility or stretchability, the bag or pouch can hold paint at less than full capacity without significant air space within the bag or pouch to maximize HPP treatment. The bag or pouch of the present invention will have a one-way valve such as the duckbill valve (10) shown in Figure 2

[0088] Paints and tints and other architectural compositions can be pasteurized by HPP in a batch process, where the paint and tint stored within a flexible container is pressurized in batches as described above, or in a more continuous manner (e.g., inline HPP), followed by aseptic filling in soft or hard, flexible or metal containers for sale to consumers.

[0089] Preferably, the paint storage in step (iii) includes storing the paint container in an environment where bacteria, if present, do not grow. As discussed above, at 10°C, a large number of bacteria do not grow. In addition, the temperature range for growth of these bacteria is above 15°C, and a very small number of bacteria will grow at temperatures of 20°C. Therefore, preferably, the paint is stored at a temperature of 20°C (68°F) or less, more preferably at a temperature of 15°C (59°F) or less, or more preferably at a temperature of 10°C (50°F) or less. These preferred storage temperatures can be achieved by conventional air conditioning techniques. In addition, it is preferred that the paint is also maintained within these temperature ranges during shipping.

[0090] ​While the exemplary embodiments of the application disclosed herein clearly realize the above-mentioned objects, it is understood that those skilled in the art can design numerous modifications and other embodiments. Therefore, it is understood that the appended claims are intended to cover all such modifications and embodiments which would fall within the spirit and scope of the present application.

Claims

1. A method for reducing biological factors in an architectural coating composition including paint and stain compositions, the method comprising the steps of: (i) preparing the architectural coating composition; (ii) applying a pressure source in the range of about 50 MPa to about 1,000 MPa to the architectural composition for a duration of up to about 10 minutes; and (iii) optionally storing the architectural composition.

2. The method of claim 1, wherein the pressure source is in the range of about 300 MPa to about 700 MPa.

3. The method of claim 2, wherein the pressure source is in the range of about 400 MPa to about 700 MPa.

4. The method of claim 2, wherein the pressure source is in the range of about 450 MPa to about 650 MPa.

5. The method of claim 1, wherein the duration is in the range of about 1 minute to about 5 minutes.

6. The method of claim 1, wherein the duration is in the range of about 3 minutes to about 5 minutes.

7. The method of claim 1, wherein the duration is in the range of about 2 minutes to about 4 minutes.

8. The method of claim 1, wherein the duration is in the range of about 2.5 minutes to about 3.5 minutes.

9. The method of claim 1, wherein the architectural composition is stored in a flexible container prior to step (ii).

10. The method of claim 1, further comprising (iv) applying a heating step concurrently or sequentially with step (ii).

11. The method of claim 1 or 10, further comprising (v) applying a second pressure treatment step.

12. The method of claim 11, wherein the second pressure treatment step is applied at the same pressure and duration as those from step (ii).

13. The method of claim 1, further comprising (vi) applying a radiation step, including gamma ray, infrared, ultraviolet, electron beam, or microwave radiation.

14. The method of claim 1, further comprising (vii) adding a biocide or antimicrobial agent to the architectural composition.

15. The method of claim 9, wherein the void space within the flexible container is less than about 10% of the volume of the flexible container.

16. The method of claim 15, wherein the void space is less than about 5% of the volume of the flexible container.

17. The method of claim 15, wherein the void space is less than about 2.5% of the volume of the flexible container.

18. The method of claim 15, wherein the flexible container is made of a material selected from polyethylene terephthalate (PET), amorphous PET (APET), crystalline PET (CPET), high density polyethylene (HDPE), low density polyethylene (LDPE), or polypropylene (PP).

19. The method of claim 9, wherein the flexible container comprises a film seal.

20. The method of claim 19, wherein the film seal is made of a material selected from PP, PE, HDPE, or PET.

21. The method of claim 1, wherein the reduction in biological agents is at least a 3-log (99.9%) reduction.

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