Compositions and methods for microbial control on material surfaces

Abstract

Compositions and methods for microbial control on material surfaces using minimal risk pesticides such as GRAS antimicrobial / preservative components. The GRAS antimicrobial / preservative component is preferably an organic acid.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 955,161 filed in the U.S. Patent and Trademark Office on December 30, 2019, U.S. Provisional Patent Application No. 62 / 955,155 filed on December 30, 2019, and U.S. Patent Application No. 17 / 128,894 filed on December 21, 2020. The disclosures of which are incorporated herein by reference in their entireties. Technical Field

[0003] The present invention relates to compositions and methods for microbial control on material surfaces, and more particularly, to compositions and methods for microbial control on material surfaces using minimal risk pesticides. Background Art

[0004] Microbial control on material surfaces can be achieved by incorporating antimicrobial agents into base materials. Current practice relies heavily on the use of active materials containing metals, such as silver, zinc and / or copper. The presence of "heavy metals" in products that may eventually leach into the environment during use or after the treated product is discarded has become a concern for environmental policy and regulatory agencies and others seeking to influence consumer markets.

[0005] Alternatively, the use of organic molecules such as phenolic resins and azoles can be utilized to treat the surface of the material by mixing it in. These chemicals can be temperature limited, sensitive to UV degradation, and expensive to use when the entire object is to be treated. In addition, many have dangerous toxic properties and can cause undesirable side effects that can affect the aesthetics of the treated article.

[0006] Therefore, there is a need for cost-effective, alternative chemistries for microbial control on material surfaces that have good efficacy but are also safe. Summary of the invention

[0007] The present invention relates to compositions and methods for microbial control on material surfaces using minimal risk pesticides.

[0008] In an embodiment of the present invention, a composition for microbial control on a material surface is provided. The composition exhibits antimicrobial properties. The composition comprises a polymeric material and a generally recognized safe (GRAS) additive or component with antimicrobial or antiseptic properties. Examples of GRAS additives include, but are not limited to, pesticides, food preservatives, etc., with minimal risk.

[0009] In an embodiment of the invention, the GRAS antimicrobial / preservative component is an organic acid.

[0010] In an embodiment of the present invention, the organic acid is selected from benzoic acid, sorbic acid, citric acid and combinations thereof.

[0011] In an embodiment of the invention, the GRAS antimicrobial / preservative component is a food preservative.

[0012] In an embodiment of the present invention, a method for microbial control on a material surface is provided. The method comprises mixing a GRAS antimicrobial / preservative component into a polymeric material.

[0013] Advantages of direct incorporation include increased durability compared to coating techniques and elimination of the coating process step during product manufacturing.

[0014] Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter.It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The invention will be more fully understood from the detailed description and the accompanying drawings, which are not necessarily drawn to scale, in which:

[0016] Figure 1 This is a thermogravimetric analysis (TGA) graph at 10°C / min, showing weight loss of the GRAS salt up to 275°C; almost no volatilization is observed.

[0017] Figure 2 The TGA graph at 10°C / min shows the weight loss of the GRAS acid up to 275°C; considerable volatilization occurs. DETAILED DESCRIPTION

[0018] The following description of the embodiments of the present invention is for exemplary purposes only and is not intended to limit the present invention, its application or use in any way. The following description herein is provided by way of example only, with the purpose of providing the disclosure of the present invention, but not limiting the scope or essence of the present invention.

[0019] The present invention relates to compositions and methods for the control of microorganisms on the surfaces of materials.

[0020] In an embodiment of the present invention, a "generally recognized as safe" (GRAS) composition for microbial control on a material surface is provided. Federal regulatory agencies use the acronym "GRAS" to refer to substances that are considered "generally recognized as safe" when used in accordance with good manufacturing practices. They are often used as food additives. For example, such regulations include 21 CFR 182, 21 CFR 184 and 21 CFR 186.

[0021] The example of GRAS components or compounds includes but is not limited to food preservatives. Food preservatives are suitable for compositions of the present invention because they are classified as the pesticides with the lowest risk, and still provide antimicrobial efficacy. In addition, food preservatives suitable for the present invention will have antimicrobial efficacy with low skin toxicity characteristics and the ability to withstand industrial polymer processing requirements (usually at a temperature of about>200°C) and miscibility with molten polymers. Food preservatives that volatilize or degrade at a temperature lower than 200°C may be suitable, but unique engineering considerations are needed to reduce their thermal exposure during processing.

[0022] In an embodiment of the present invention, the food preservative is an organic acid. Examples of organic acids include, but are not limited to, benzoic acid, propionic acid, sorbic acid, citric acid, lactic acid, ascorbic acid, acetic acid, erythrosonic acid, fumaric acid, malic acid, glycolic acid, derivatives thereof, and combinations thereof. Preferred organic acids include, but are not limited to, benzoic acid, sorbic acid, citric acid, and combinations thereof.

[0023] The compositions of the present invention may include one or more additives. For example, essential oils may be added in combination with benzoic acid, sorbic acid, or a combination thereof to have a stronger activity against fungal species. Some essential oils, such as cinnamon oil, have little to no antibacterial activity but have a unique effect on fungal species.

[0024] Examples of essential oils include, but are not limited to, cedarwood oil, tea tree oil (Melaleuca alternifolia), eucalyptus oil (Eucalyptus globulus or E. radiata), clove oil (Eugenia caryophyllata), oregano oil (Origanum vulgare), thyme oil (Thymus vulgaris), geranium oil (Pelargoniumgraveolens), cinnamon bark oil (Cinnamomum zeylanicum), peppermint oil (Mentha piperita), citronella oil (Cymbopogon flexuosus), basil oil (Ocimum basilicum), lavender oil (Lavandulaangustifolia), lemon oil (Citrus limon), rosemary oil (Salvia rosmarinus), bergamot oil (Citrus bergamia), perilla oil (Perilla frutescens), coriander oil (Coriandrum sativum), citron oil (Citrus serrulata), and thyme oil (Thymus vulgaris). Preferred essential oils include, but are not limited to, cinnamon bark oil (Cinnamomumzeylanicum), citronella oil (Cymbopogon flexuosus), thyme oil (Thymus vulgaris), cedar oil, citronella oil, peppermint oil, rosemary oil, clove oil, and combinations thereof.

[0025] In addition, it may be necessary to control odors that are not related to microorganisms. Organic acids (or combinations thereof) can provide the ability to neutralize alkali-based odors (such as ammonia) through their acidic properties. Acids with aromatic groups, such as benzoic acid, have the potential to chelate ring-based odor substances (such as pyridine). In order to supplement these effects, additional odor mitigation compounds can be added to the combination of organic acids and / or essential oils to remove existing odors. Adding odor mitigation compounds produces a unique blend that can provide antimicrobial and odor control benefits. The example of odor mitigation compounds includes but is not limited to metal oxides, activated carbon, sodium bicarbonate, calcium carbonate and zinc ricincoleate.

[0026] Adding a metal oxide (eg, ZnO) to any chemical creates a unique blend that can provide antimicrobial and odor control benefits.

[0027] In an embodiment of the present invention, the composition of the present invention is preferably in the form of a polymer concentrate, such as a masterbatch or a polymer binder for coatings, comprising benzoic acid, sorbic acid or a combination thereof. In the polymer concentrate, an active substance concentration of 1% to 60% or more preferably 5% to 40% by weight of the composition is required. In the polymer binder for durable coatings, a concentration of 0.1% to 40% range based on solution % solids is required. If more than one acid is used in combination, the total weight of the active acid is between 5% and 40% by weight of the final composition.

[0028] The compositions of the present invention may optionally comprise essential oils in concentrations of from 1% to 50% or more preferably from 5% to 20% by weight of the total composition and may optionally comprise odour reducing compounds in concentrations of from 1% to 60% or more preferably from 5% to 40% by weight of the total composition.

[0029] The carrier for the masterbatch is preferably a low melting point polymer or copolymer compatible with the base material to be mixed with the masterbatch. It is desirable to minimize any high thermal history of the heat-sensitive acid active substance. The carrier will provide protection during high temperature processing to allow the polymer of higher temperature to be mixed, such as polypropylene (PP). The example of the base polymer material includes but is not limited to PP, EMA, polyolefin, SAN, TPU, ABS, PS and PC and PVC. For example, polypropylene (PP) is a kind of polyolefin polymer, which is generally used to manufacture a lot of consumer products. The concentrate is then pellet-pellet blended with the base raw material (such as PP), and injection molded to form a part (based on the final product weight) with a concentration of 0.05% to 10% active substance. The final concentration of the essential oil is preferably 0.05% to 5.0%, and the concentration range of the odor mitigation compound is similar to that of acid, such as 0.05% to 10%. The use of ethylene methacrylate (EMA), propylene-ethylene copolymers (such as Vistamaxx), SEBS, PE and PP as masterbatch carriers is an example of the concept of using low melting point polymers to encapsulate raw heat sensitive additives (such as these GRAS acids) without damaging them or causing them to volatilize, and then using concentrates to handle polymers that must be processed at temperatures higher than would otherwise be possible.

[0030] The use of direct blending of these acids for antimicrobial protection rather than using a typical coating process is an important improvement because it eliminates the expensive coating step and further improves product quality; the blended antimicrobial agent is more durable and will not wear off or wear away. In the case of polymers, when the organic acid is incompatible with the base resin, a stabilizer or compatibilizer can be added to the masterbatch to improve the shelf life stability of the product.

[0031] In the embodiment where coating is needed, the polymer binder can be composed of or substantially composed of: acrylic acid, acrylate, carbamate, isocyanate, polyvinylidene chloride (PVDC), polyvinylidene fluoride (PVDF), hexafluoropropylene, carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), polyvinyl acetate (PVAc), polyamide and polyimide. These can be added with any combination of any suitable oligomer, homopolymer, copolymer or elastomer. In some embodiments, the binder can be aqueous, non-aqueous, or contain trace cosolvents. The type of polymer binder is not particularly limited, and can include any polymer that its composition can be suitable for coating. Add GRAS to form a coating with a concentration of 0.05% to 10% by weight of the final coating. Non-limiting examples can be PVDC polymer binder water-based coatings with a concentration of 0.5% benzoic acid active substance. Once mixed in, GRAS acid becomes bonded to the substrate.

[0032] Applications include, but are not limited to, treating polymeric materials to produce antimicrobial and / or odor benefits on the surface of said materials.

[0033] Unlike current technologies that are classified as possible toxins, the compositions of the present invention are non-toxic, suitable for use in most forms of polymer manufacturing, stable to polymer processing shear and heat, and do not significantly affect final product properties. Table A below shows that when benzoic acid is mixed at different levels with different polymer concentrate carriers, there is little change in tensile, flexural and impact measurements of PP.

[0034] Table A

[0035]

[0036] Table A – Physical testing results of injection molded PP parts treated with GBA between 0.2% and 0.35% using two different polymer carriers for the masterbatch concentrate.

[0037] Example 1

[0038] Initial work focused on three GRAS chemicals: benzoate, sorbate and citrate. Figure 1 The TGA graphs of these salts are shown, indicating that all salts are thermally stable to temperatures above 300°C.

[0039] exist Figure 1The TGA graph at 10°C / min shows volatilization of the GRAS salts until 275°C. The sorbate and citrate salts are stable (do not lose any mass) to temperatures above 275°C, while the citrate salt is about 10% water, which is why it loses about 10% of its weight before reaching equilibrium - there is no volatilization of the salt itself. This thermal stability and the reported antimicrobial efficacy make these compounds seem ideal for this application.

[0040] Each salt chemistry was evaluated by compounding it at a 10% concentrate level into a polyolefin carrier and then using the polymer concentrate as a masterbatch to injection mold PP plaques for testing at various end-use levels. Commercial PP and EMA materials were compounded in a twin-screw extruder and used to make test plaques in a 35-ton injection molding machine.

[0041] This served the dual purpose of testing processing compatibility as well as providing samples to test active efficacy levels.

[0042] Table 1

[0043] sample ISO 22196 ISO 22196 TM90 TM90 PP w / 0.25% GNC .3 NR NZ NZ PP w / 0.5% GNC .4 NR NZ NZ PP w / 0.5% GKS NR NR NZ NZ PP w / 1.0% GKS .2 NR NZ NZ PP w / 0.5% GNC and 1.0% GKS combination NR NR NZ NZ PP w / 0.5% GNB 1.0 NR NZ NZ PP w / 1.0% GNB .4 NR NZ NZ

[0044] Table 1 – Results of TR19031210 testing of GRAS salts in PP. A log reduction > 1 is required to pass ISO 22196. NR = No Reduction. NZ = No Zone. Both indicate failure. GNC = Sodium Citrate, GKS = Potassium Sorbate, GNB = Sodium Benzoate

[0045] Surprisingly, regardless of Figure 1 As shown in Table 1, the salts of each of the above acids (sodium benzoate, potassium sorbate and trisodium citrate) alone did not result in significant bacterial efficacy at any active substance concentration up to 1% tested according to ISO 22196. Using the inhibition zone test (AATCC TM90), the samples also did not show any efficacy. In addition, the use of salt treatment of the plates caused the plates to become opaque due to the high levels used.

[0046] Secondly, the acid moieties (benzoic acid, sorbic acid, and citric acid) were investigated, although they did not appear to be sufficiently thermally stable to withstand PP processing, e.g. Figure 2studied in . Citric acid begins to volatilize at 200°C. Benzoic acid and sorbic acid begin to volatilize at about 100°C and are essentially completely gone before the TGA test sample reaches 200°C, indicating that they are not suitable for direct processing into PP. Rather than compounding directly into PP to prepare a PP masterbatch concentrate, it is better to choose a polymer with a lower processing temperature range. EMA is compatible with PP and has a very wide processing temperature range. It can be compounded at temperatures as low as 120°C and can withstand processing temperatures in excess of 250°C. The above three acids were successfully compounded into EMA at 10% concentration to prepare a masterbatch concentrate, with negligible losses due to volatilization.

[0047] Despite the TGA thermal properties, the three EMA / acid masterbatches were compounded into PP at temperatures above 200°C and surprisingly, the analysis showed very little loss of acid active during processing. Pre-encapsulation of the acid in EMA prevented loss of the active ingredient through volatilization and enabled production of PP parts regardless of processing temperature. Compounding the acid into a compatible low melting point carrier to minimize volatilization losses of the GRAS acid during processing was found to be a critical part of the incorporation process.

[0048] Test panels were made by injection molding into PP at 0.5% and 1% active level concentrations, and all samples showed little aesthetic impact from the acid additives. All samples produced showed good antimicrobial efficacy, except for citric acid (GCA), which was good at higher levels but declined at lower levels (Table 2). Further experiments showed that the efficacy of sorbic acid (GSA) as low as 1000 ppm and benzoic acid (GBA) at 2000 ppm to 3500 ppm was strongly reduced when it was considered to be entered into PP.

[0049] Table 2

[0050] sample ISO 22196 ISO 22196 TM90 TM90 PP w / 0.5% GCA NR 1.9 NZ NZ PP w / 1.0% GCA 3.4 3.0 NZ NZ PP w / 0.5% GBA 4.3 3.0 NZ NZ PP w / 1.0% GBA 4.5 3.0 NZ NZ PP w / 0.5% GSA 4.0 3.0 NZ NZ PP w / 1.0% GSA 4.5 3.0 NZ NZ

[0051] Table 2 shows the log reduction results for the TR19031105 test of GRAS acids in PP panels. A log reduction > 1 requires a significant difference in the bacterial population. NZ = No Zone, indicating a TM90 failure. GCA = Citric Acid, GBA = Benzoic Acid, GSA = Sorbic Acid. The acids did not leach, so TM90 is not suitable for determining efficacy, but all but the lowest GCA sample passed ISO 22196. Panels were tested in Xenon Arc and QUV instruments to ensure good UV stability, and it was found that the sample color changed only slightly, responding to a much stronger preference for a dark yellow cast produced by the zinc pyrithione treated sample or a brown cast produced by the silver treated sample.

[0052] In addition to processing at 200° C., samples were also run with PP at 250° C. to simulate the use of these GRAS acids in polymers that are processed at higher temperatures than polypropylene. Samples were also run in the injection molding machine using an extended dwell time (from the normal 30 second dwell time to a 120 second dwell time) to simulate a longer cycle time process that would hold the polymer material at a certain temperature for an extended period of time, with the extended cycle being run at both 200° C. and 240° C. The samples produced from these runs also showed excellent efficacy and very little aesthetic change (slight darkening at the higher temperature).

[0053] Table 3

[0054] sample ISO 22196 ISO 22196 PP w / 0.25% GBA (120s dwell time, 240℃) 3.7 2.6 PP w / 0.5% GBA (120s dwell time, 240℃) 4.6 3.2 PP w / 0.25% GSA (120s dwell time, 240℃) 4.0 3.2 PP w / 0.5% GSA (120s dwell time, 240℃) 4.3 3.2

[0055] Table 3 shows the log reduction resulting from holding the samples at 240°C in the injection molding machine for an extended residence time of 2 minutes, demonstrating thermal stability in a production relevant environment.

[0056] Table 4. Log reduction of PE and EVA samples with 0.1% GBA

[0057] sample ISO 22196 ISO22196 PE with 0.1% GBA > 3 > 1 EVA with 0.1% GBA > 3 > 1

[0058] Table 5. Efficacy of GBA-treated PE and EVA against yeast Candida albicans (Ca) and fungus Aspergillus niger (An) using ASTM E2180 procedure

[0059] sample ASTM E2180 ASTM E2180 PE with 0.3% GBA > 2 > 2 EVA with 0.1% GBA n / a > 1

[0060] The materials treated with benzoic acid and sorbic acid were tested for antifungal resistance using qualitative methods and did not show any difference between untreated and treated. As is well known, most plastics do not support fungal growth, and common industry qualitative standards such as AATCC TM30 (Part 3) or ASTM G21 are not sensitive enough to prove their efficacy. Even untreated PP or PE materials usually do not have observable fungal growth after testing. However, the quantitative fungal method of ASTM E2180 rules is more sensitive, proving that GRAS organic acids (such as benzoic acid) are mixed into materials, and for PE, more than 99% (2log) fungal growth reduction will be provided, and more than 90% will be reduced when mixed into EVA. Adding essential oils to benzoic acid or sorbic acid will further improve the antifungal efficacy of the treated materials.

[0061] Therefore, it should be readily understood by those skilled in the art that the present invention allows wide range of uses and applications. From the present invention and its previous description, many embodiments and adaptations of the present invention beyond those described herein and many changes, modifications and equivalent arrangements will be apparent or reasonably proposed without departing from the essence or scope of the present invention. Therefore, although the present invention is described in detail herein about preferred embodiments, it should be understood that the present disclosure is only an illustration and example of the present invention, and is made only to provide the completeness of the present invention and to allow disclosure. The foregoing disclosure is not intended to or should not be interpreted as limiting the present invention or excluding any such other embodiments, adaptations, changes, modifications and equivalent arrangements in addition.

Claims

1. An additive composition for microbial control in polymer articles, the composition comprising: a polymer carrier which is ethylene methacrylate (EMA), wherein the polymer carrier has compounded therein 1 wt % to 60 wt % of a GRAS additive or component having antimicrobial or preservative properties; wherein the GRAS additive or component is selected from benzoic acid, sorbic acid, citric acid, and combinations thereof, and wherein the additive composition exhibits antimicrobial properties.

2. The composition according to claim 1, further comprising an essential oil.

3. The composition according to claim 2, wherein the essential oil is selected from the group consisting of cedarwood oil, tea tree oil (Melaleucaalternifolia), eucalyptus oil (Eucalyptus globulus or E.radiata), clove oil (Eugeniacaryophyllata), oregano oil (Origanum vulgare), thyme oil (Thymus vulgaris), geranium oil (Pelargonium graveolens), cinnamon bark oil (Cinnamomum zeylanicum), peppermint oil (Menthapiperita), citronella oil (Cymbopogon flexuosus), basil oil (Ocimum basilicum), lavender oil (Lavandula angustifolia), lemon oil (Citrus limon), rosemary oil (Salvia rosmarinus), bergamot oil (Citrus bergamia), perilla oil (Perilla frutescens), coriander oil (Coriandrumsativum), citron oil (Citrus medica), and combinations thereof.

4. The composition of claim 1 further comprising an odor reducing compound.

5. The composition of claim 4, wherein the odor reducing compound is selected from the group consisting of metal oxides, activated carbon, sodium carbonate, calcium carbonate, zinc rincoleate, and combinations thereof.

6. The composition of claim 2, wherein the concentration of the essential oil is 1% to 50% by weight of the composition.

7. A composition according to claim 4, wherein the concentration of the odour reducing compound is from 1% to 60% by weight of the composition.

8. A method for microbial control in a polymer article, the method comprising: A GRAS additive or component with antimicrobial or preservative properties selected from benzoic acid, sorbic acid, citric acid and a combination thereof is mixed into a polymer material, wherein the GRAS additive or component with antimicrobial or preservative properties is added in the form of a masterbatch, the masterbatch comprises a polymer carrier, the polymer carrier is ethylene methacrylate, the masterbatch is mixed into the polymer material, the polymer material is selected from: PP, EMA, polyolefin, SAN, TPU, ABS, PS, PC and PVC, and the GRAS additive or component is an organic acid.

9. The method of claim 8, further comprising mixing the essential oil with a GRAS additive or component having antimicrobial or preservative properties.

10. The method according to claim 9, wherein the essential oil is selected from the group consisting of cedarwood oil, tea tree oil (Melaleucaalternifolia), eucalyptus oil (Eucalyptus globulus or E.radiata), clove oil (Eugeniacaryophyllata), oregano oil (Origanum vulgare), thyme oil (Thymus vulgaris), geranium oil (Pelargonium graveolens), cinnamon bark oil (Cinnamomum zeylanicum), peppermint oil (Menthapiperita), citronella oil (Cymbopogon flexuosus), basil oil (Ocimum basilicum), lavender oil (Lavandula angustifolia), lemon oil (Citrus limon), rosemary oil (Salvia rosmarinus), bergamot oil (Citrus bergamia), perilla oil (Perilla frutescens), coriander oil (Coriandrumsativum), citron oil (Citrus medica), and combinations thereof.

11. The method of claim 8, wherein the carrier is compatible with the polymeric material.

12. The method of claim 8, further comprising forming an article from the polymeric material having the GRAS additive or component incorporated therein.

13. The method of claim 12, wherein the GRAS additive or component having antimicrobial or preservative properties is present at an active concentration ranging from 0.05% to 10% by weight of the article.

14. The method of claim 12, wherein the essential oil is present in an active concentration ranging from 0.05% to 5.0% by weight of the preparation.

15. The method of claim 8, further comprising an odor reduction compound.

16. The method of claim 15, further comprising forming an article from the polymeric material having a GRAS additive or component incorporated therein, wherein the odor reduction compound is present at an active concentration ranging from 0.05% to 10% by weight of the article.

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