Antimicrobial copper-based polyurethane

Abstract

The antimicrobial polyurethane and method of making the antimicrobial polyurethane may include mixing a plurality of hydrophobic antimicrobial metal compound particles into a reaction mixture. The reaction mixture may include a polyol and an isocyanate. The method may include mixing the polyol with a plurality of hydrophobic copper oxide particles to produce a polyol slurry, and subsequently mixing the polyol slurry with an isocyanate to form a polyurethane foam. Other polyurethane articles and methods may be utilized.

Description

[Technical field]

[0001] The present invention relates generally to foamed plastic materials, and more specifically to foamed polyurethanes having antimicrobial properties. The present invention describes a method and composition for making highly effective antimicrobial foam products that contain uniformly distributed and consistent cuprous oxide. [Background technology]

[0002] Polyurethanes are ubiquitous and can be found in liquid coatings and paints, other tough elastomers such as roller blade wheels, rigid insulation, and soft flexible foams.

[0003] Flexible polyurethane foam is used as cushioning for a variety of consumer and commercial products, including bedding, furniture, automotive interiors, carpet underlay and packaging. Flexible foam can be made in any of a wide variety of shapes and firmnesses. It is lightweight, durable, supportive and comfortable.

[0004] These flexible foam substrates, especially bedding products such as mattresses, mattress toppers, pillows, etc., are excellent substrates for microorganisms to thrive and grow in both healthcare and consumer environments.

[0005] Lange et al. (2014) found that 38% of hospital pillows were colonized with MRSA and E. coli and concluded that disposable pillows could be a more hygienic option for use in hospital beds. Shik et al. (2014) cut open nominally fluid-proof (stitched) pillows in a burn unit and found that many were visibly contaminated with body fluids. Mottar et al. (2006) observed significant differences in pillow mass in a burn center. Investigation revealed fluid leakage into the pillow interior through the stitches and isolation of multiple pathogens from the inside of the pillow, which correlated well with patient infections and indicate such potential sources of infection. Lippmann et al. (2014) searched for a source of infection to explain a large outbreak of Klebsiella pneumoniae carbapenemase (KPC) in Germany. They found that the interior of positioning pillows was contaminated and had remained so for at least 6 months.

[0006] From these disclosures, it is clear that the common practice of placing pillows and mattresses in waterproof covers does not prevent pathogens from entering and multiplying within the pillow or mattress. Because pillows (or other parts of the structure) inevitably compress and expand during normal use, air must flow in as the pillow expands and out as the pillow compresses. It is estimated that approximately 2 liters of air enters and leaves the pillow within a few seconds when the pillow is compressed or expanded. In the case of a simple waterproof pillow, the air can flow through an opening flap or, if the cover is sewn, through a suture hole in the seam of the cover. This latter scenario is particularly troublesome. High concentrations of contaminants can be introduced just inside the stitching of the interior of the pillow (Dewhurst et al. 2012). Here, they persist and multiply in latency. The contaminated air is then expelled from the pillow through a small suture hole when the patient places his or her head on the pillow. Exhaled air generates aerosols of microorganisms that can persist in the ambient air for long periods of time and have the ability to recolonize not only the patient or subsequent patients, but also the patient's environment (Kalogerakis 2005).

[0007] The polymeric material used for filling provides available carbon and nitrogen sources to support growth (Jenkins et al., 2005). Woodcock et al. (2006) also found that 47 fungal species were endemic to the pillows, including Aspergillus fumigatus, Aureobasidium pullulans, and Rhodotorula mucilaginosa.

[0008] In "Antimicrobial Activity of Copper Sulfate and Copper Oxide Embedded on Polyurethane Foam", Materials Science Forum, Vol. 917, pp. 22-26 (2018), Pulutan et al. describe CuSO4 and CuO deposited polyurethane foams. CuSO4 deposited polyurethane foams were prepared by immersing the foam in CuSO4 solution and compression molding the foam. Compression molding of the polyurethane foam was done to ensure the removal of air from the foam cavities and more complete contact of the solution with the foam, allowing the copper ions from the solution to enter these cavities.

[0009] To deposit CuO onto polyurethane foam, CuO was added to a sodium hydroxide solution on a hot bath at 70° C. The sodium hydroxide reacts with the copper ions to form a precipitate of copper hydroxide, which is metastable and oxidizes to copper oxide. The polyurethane foam is then immersed in the solution and compression molded to deposit the copper onto the foam. This method of treating polyurethane foam is messy and requires special processing and handling.

[0010] In another method, Sportelli et al. in "Investigation of Industrial Polyurethane Foams Modified with Antimicrobial Copper Nanoparticles", Materials, Vol. 9, 544 (2016) describe antimicrobially active copper nanoparticles that were electrosynthesized and applied for the controlled impregnation of industrial polyurethane foams used as padding in textile production or filters for air conditioning systems. This method involves the use of expensive nanoparticles and, depending on the application method, the antimicrobial activity may not be distributed evenly and homogeneously throughout the foam substrate.

[0011] In US Patent Application No. 20120322903, Karandikar describes a method for producing polyurethane foams with antimicrobial properties using silver, zinc, or copper. This invention also suffers from a significant drawback in that the silver saccharinate and silver nanoparticles are not consistently and uniformly distributed within the substrate, resulting in significant variability in the antimicrobial performance of the foam product. Furthermore, this invention describes the need for a complexing agent to form a stable blend of antimicrobial additives. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] U.S. Patent Application No. 20120322903 [Non-patent literature]

[0013] [Non-Patent Document 1] Pulutan et al. “Antimicrobial Activity of Copper Sulfate and Copper Oxide Embedded on Polyurethane Foam”, Materials Science Forum, Vol. 917, pp. 22-26 (2018) [Non-Patent Document 2] Sportelli et al. “Investigation of Industrial Polyurethane Foams Modified with Antimicrobial Copper Nanoparticles”, Materials, Vol. 9, 544 (2016) Summary of the Invention [Problem to be solved by the invention]

[0014] There is a need for antimicrobial polyurethane foams and also for antimicrobial polyurethane foam fillings for pillows and mattresses, particularly pillows and mattresses used in hospitals, to prevent the growth and survival of microorganisms. [Means for solving the problem]

[0015] An embodiment of a method for making a polyurethane includes mixing a polyol, an isocyanate, and a plurality of hydrophobic antimicrobial metal compound particles to form a polyurethane foam. In such an embodiment, the method may include mixing a polyol with a plurality of hydrophobic copper oxide particles to produce a polyol slurry, and subsequently mixing the polyol slurry with an isocyanate to form the polyurethane foam.

[0016] The antimicrobial compound particles can include, but are not limited to, copper oxide, cuprous oxide, cupric oxide, copper iodide, zinc oxide (ZnO), and silver oxide (Ag2O). For example, the antimicrobial particles can be water-insoluble copper compound particles. The water-insoluble copper compound particles can be exposed and protruding from the surface of the polymeric material, where the water-insoluble copper oxide particles migrate to Cu when in contact with a fluid. + ions and Cu ++ The copper oxide may be cupric oxide or cuprous oxide.

[0017] Hydrophobic copper oxide particles have low miscibility with hydrophilic polyols. An embodiment of the hydrophobic copper oxide particles may be surface-modified copper oxide particles. The surface modification may be any modification that imparts hydrophobicity to the copper oxide particle surface. The surface modification may be achieved by reacting the copper oxide surface moiety with a hydrophobic compound. For example, the copper oxide particles may be surface-modified by reacting with a fatty acid, such as a saturated fatty acid. The fatty acid may be stearic acid. Alternatively, a hydrophobic coating or partial coating may be applied to the copper oxide particles. The coating may be applied to the copper oxide particles such that the copper oxide particles are hydrophobic when the copper oxide particles come into contact with a fluid. + ions and Cu ++ It should be such that it releases at least one of the ions to provide antimicrobial activity.

[0018] The polyol may be any polyol capable of reacting with an isocyanate to form a polymer. As used herein, "polyol" refers to compounds having at least two hydroxyl groups, including, but not limited to, difunctional polyols, i.e., diols, and compounds containing three or more hydroxyl groups, such as, but not limited to, triols. In embodiments, exemplary polyols may have from about 2 to about 5 hydroxyl groups. In some embodiments, the polyol may be a difunctional polyol. Additionally, the polyol may include amino end groups.

[0019] In embodiments, the polyol may be an alkene oxide polyol, an ethylene oxide polyol, a propylene oxide polyol, a polyether polyol, a polyester polyol, a polycarbonate polyol, a hydrocarbon polyol, a polysiloxane polyol, copolymer polyols of these polymers, combinations thereof, and the like.

[0020] In embodiments, the isocyanate may be at least one of methylene diphenyl diisocyanate, toluene diisocyanate, and combinations thereof.

[0021] Another embodiment is an antimicrobial polyurethane article. The antimicrobial polyurethane article may be a foam, fiber, coating, elastomer, or other article. An embodiment of the antimicrobial polyurethane article includes a polyurethane and a plurality of antimicrobial particles, at least a portion of which are modified to be hydrophobic.

[0022] An embodiment of the antimicrobial polyurethane article may be a monomer derived from the reaction of a polyol with an isocyanate. The isocyanate may be selected from the group including, but not limited to, methylene diphenyl diisocyanate, toluene diisocyanate, and combinations thereof.

[0023] Embodiments of polyurethane articles include foams, mattresses, pillows, carpet padding, insulation, seat cushions, vehicle seats, wound dressings, kitchen sponges, sponges, packaging, footwear including insoles, laminates, fibers including spandex fibers, and other articles. Such articles can be manufactured using the present method. Additionally, the polyurethane article can be a polyurethane foam having a density greater than 3.0 pounds per square foot.

[0024] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. Furthermore, terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in light of the relevant art and this disclosure, and should not be interpreted in an idealized or overly formal sense unless so clearly defined in the present specification.

[0025] It will be understood that in the description of the present invention, a number of techniques and steps are disclosed. Each of these has its own advantages, and each can also be used in combination with one or more, or in some cases all, of the other disclosed techniques. Thus, for purposes of clarity, this description avoids repeating every possible combination of the individual steps in an unnecessary manner. However, the specification and claims should be read with the understanding that such combinations fall entirely within the scope of the present invention and the claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] An embodiment of a method for making polyurethane includes mixing a polyol, an isocyanate, and a plurality of hydrophobic antimicrobial metal compound particles to form a polyurethane foam. The plurality of hydrophobic antimicrobial metal compounds may be added to the other components either individually, as part of a raw material blend, in a masterbatch, or a combination thereof. For example, the method may include mixing a masterbatch including a plurality of antimicrobial hydrophobic copper oxide particles with a polyol or an isocyanate. Alternatively, the method may include mixing a polyol directly with a plurality of hydrophobic copper oxide particles to make a polyol slurry, and then mixing the polyol slurry with an isocyanate to form a polyurethane foam.

[0027] <Antimicrobial particles> The method and polyurethane article may include any hydrophobic antimicrobial metal compound particles, including but not limited to antimicrobial metal oxide particles, which should be treated to render them hydrophobic so that their antimicrobial properties are retained in the resulting polyurethane product.

[0028] The present inventors have surprisingly discovered that hydrophobic antimicrobial particles have improved antimicrobial efficacy and activity over other antimicrobial particles.Without limiting the present invention, it is hypothesized that the hydrophobic particles migrate from the center of the foam network structure to the outer surface of the network.This structure allows the polyurethane article, such as polyurethane foam, to have greater antimicrobial activity.

[0029] Hydrophobic antimicrobial compound particles that may be used in the polyurethane and method include, but are not limited to, copper oxide, cuprous oxide, cupric oxide, copper iodide, zinc oxide (ZnO), and silver oxide (Ag2O). For example, the antimicrobial particles may be water-insoluble copper compound particles. The water-insoluble copper compound particles may be exposed and protruding from the surface of the polymeric material, where the water-insoluble copper oxide particles migrate to Cu when in contact with a fluid. + Ion and Cu ++ The copper oxide may be cupric oxide or cuprous oxide.

[0030] The hydrophobic copper oxide particles have low miscibility with hydrophilic polyols. In an embodiment, the hydrophobic copper oxide particles are surface-modified copper oxide particles. The surface modification can be any modification that imparts hydrophobicity to the copper oxide particle surface. The surface modification can be achieved by reacting a surface portion of the copper oxide with a hydrophobic compound. For example, the copper oxide particles can be surface-modified by reacting with a fatty acid, such as a saturated fatty acid. The fatty acid can be stearic acid. Alternatively, a hydrophobic coating or partial coating can be applied to the copper oxide particles. The coating can be applied such that, once the copper oxide particles come into contact with a fluid, the copper oxide particles are hydrophobic. + Ion and Cu ++ It should be such that it releases at least one of the ions to provide antimicrobial activity.

[0031] As used herein, "hydrophobic" means that the contact angle between the particle and water is greater than 90 degrees due to a coating or other hydrophobic modification. To improve particle segregation to the outer regions of the polyurethane article, the contact angle may be greater than 120 degrees. The stearic acid modified hydrophobic copper oxide particles used herein have a contact angle with water greater than 120 degrees.

[0032] The antimicrobial metal compound particles may have an average particle size ranging from 0.5 to 10 microns, in other embodiments, the copper oxide particles may have an average particle size of 1.0 to 2.0 microns.

[0033] <Polyol> The polyol may be any polyol capable of reacting with an isocyanate to form a polymer. As used herein, "polyol" refers to compounds having at least two hydroxyl groups, including, but not limited to, difunctional polyols or diols, and compounds containing three or more hydroxyl groups, such as, but not limited to, triols. In embodiments, exemplary polyols may have from about 2 to about 5 hydroxyl groups. In some embodiments, the polyol may be a difunctional polyol. Additionally, the polyol may include amino end groups.

[0034] In embodiments, the polyol may be an alkene oxide polyol, an ethylene oxide polyol, a propylene oxide polyol, a polyether polyol such as, but not limited to, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, a polyester polyol such as, but not limited to, branched polyester polyols, a polycarbonate polyol, a hydrocarbon polyol, a polysiloxane polyol, copolymer polyols of these polymers, polyols formed from cyclic ethers, combinations thereof, and the like.

[0035] <Isocyanate> In embodiments, the isocyanate may be at least one of methylene diphenyl diisocyanate, toluene diisocyanate, and combinations thereof.

[0036] Another embodiment is an antimicrobial polyurethane article. The antimicrobial polyurethane article may be a foam, fiber, coating, elastomer, or other article. An embodiment of the antimicrobial polyurethane article includes a polyurethane and a plurality of antimicrobial particles, at least a portion of which are modified to be hydrophobic.

[0037] An embodiment of the antimicrobial polyurethane article may be a monomer derived from the reaction of a polyol with an isocyanate. The isocyanate may be selected from the group including, but not limited to, methylene diphenyl diisocyanate, toluene diisocyanate, and combinations thereof.

[0038] The polyurethane article may be a polyurethane foam having a density greater than 3.0 pounds per square foot.

[0039] <Antimicrobial effect of foam samples> The term "antimicrobial" will be understood to include antibacterial, antifungal, antiviral, and / or antiparasitic activity, activity against protozoa, yeasts, and / or molds. Antimicrobial may be, for example, bacteriocidal or bacteriostatic.

[0040] In an embodiment, the hydrophobic antimicrobial particles may be water-insoluble copper compound particles. The water-insoluble copper oxide particles are capable of converting Cu to copper oxide upon contact with the fluid. + Ion and Cu ++ The water-insoluble copper compound particles may be exposed and protruding from the surface of the polyurethane, where they release at least one of the Cu ions when the water-insoluble copper oxide particles come into contact with the fluid. + Ion and Cu ++ At least one of the ions is released.

[0041] <Preparation of hydrophobic copper oxide> Copper oxide particles were prepared by surface treatment with stearic acid. To prepare the copper particles coated with stearic acid, 17g of stearic acid was added to a 1L beaker, followed by 400mL of ethanol and 200mL of distilled water. The mixture was heated to 70°C and constantly stirred until the stearic acid was completely dissolved. Then, 100g of copper oxide particles was added to the stearic acid solution and constantly stirred at 70°C for 5 hours. The mixture was allowed to stand and finally filtered to obtain the product. The copper oxide coated with stearic acid was dried in a vacuum oven at 60°C for 6 hours and then crushed to form a powder.

[0042] <Method of manufacturing polyurethane foam> To make the foam slabs, a plurality of hydrophobic cuprous oxide particles (prepared above) were added to a polyol (Voranol 1447™ available from Dow Chemical Company) and blended using a high speed mixer until substantially uniform. A compatible surfactant and a compatible polymeric thickener (each at a level less than 5 w / w%) were added to the polyol along with a hydrophobic antimicrobial agent. Stannous octoate was added at 0.1 wt% as a catalyst to control the initiation of the reaction.

[0043] This polyol slurry was then added to either toluene diisocyanate (TDI) or methylene diphenyl diisocyanate (MDI) and mixed in a disposable wax paper cup. The reactants were then poured into a rectangular wax paper mold. Within a few minutes, the poured reactants expanded as the mixture began to foam and harden. The mold and its contents were left under very low light inside a ventilated hood for approximately 30 minutes. At this time, the hardened foam mass was non-tacky to the touch. The foam was removed from the mold, placed on a pile of disposable paper towels, and heated in a microwave oven for 5-10 minutes. The sample foams were then transferred to a conventional oven at 55°C and allowed to dry completely overnight. A control foam sample was made in the same manner except that the hydrophobic cuprous oxide particles were not added.

[0044] All foam samples were evaluated for antimicrobial efficacy using the AATCC-100 test method. 1" x 1" samples with a thickness of 0.5" were cut from the foam substrate for testing. The foam samples were inoculated with bacteria and incubated for a period of time called the contact time (usually 24 hours or 2 hours). After the contact time, bacteria were recovered from the samples by stomaching. The recovered bacteria were enumerated by colony forming units using a serial dilution method.

[0045] [Table 1]

[0046] [Table 2]

[0047] At a contact time of 24 hours, both samples above (Test 2.1 and Test 2.2) showed the same effect and were indistinguishable from each other in terms of antimicrobial performance, despite the lower cuprous oxide content of the sample made with MDI. Surprisingly, we discovered that at a contact time of 2 hours, the sample made with methylene diphenyl diisocyanate (MDI) performed significantly better than the foam sample made with toluene diisocyanate (TDI), despite the lower cuprous oxide content of the MDI sample.

[0048] <Active copper> Active copper is determined by measuring the amount of readily available copper in the foam that can be extracted without destroying the foam. A solution of bicinchoninic acid (BCA), a known copper complexing agent, is prepared in phosphate buffered solution (PBS). A known amount of foam sample is immersed in the BCA solution for 2 hours. During this time, the BCA reacts with the copper to form a purple BCA-copper complex. After 2 hours, a small amount of solution is obtained and the copper in solution is estimated by a colorimetric assay.

[0049] [Table 3]

[0050] The % active copper extracted from the foam samples made with TDI ranged from 12% to 23%, but surprisingly, the foam samples made with MDI had much more extractable copper, ranging from 46% to 56%.

[0051] In another example, polyurethane foams were made in two different densities (2.2 lbs / ft 3 and 3.5 lbs / ft 3 ) and compared for activated copper.

[0052] [Table 4]

[0053] Surprisingly, the polyurethane foam samples having higher densities exhibited higher percentages of extractable or active copper.

[0054] In another example, cuprous oxide was made hydrophobic by treating it with sodium stearate. Polyurethane foams were made with regular cuprous oxide and hydrophobic cuprous oxide treated with sodium stearate. The samples were compared for active copper.

[0055] [Table 5]

[0056] Surprisingly, the polyurethane foam samples containing the hydrophobically treated cuprous oxide exhibited a much higher percentage of extractable or active copper than regular cuprous oxide.

[0057] The described embodiments of the polyurethane products and methods of making the polyurethane products are not limited to the specific embodiments, components, method steps, and materials disclosed herein, as such components, method steps, and materials may vary. Additionally, the terminology used herein is used only for the purpose of describing exemplary embodiments, and is not intended to be limiting, since the scope of the various embodiments of the present invention is limited only by the appended claims and equivalents thereof.

[0058] Thus, although embodiments of the present invention have been described with reference to exemplary embodiments, those skilled in the art will recognize that variations and modifications can be made within the scope of the invention as defined in the appended claims. Accordingly, the scope of various embodiments of the present invention should not be limited to the above-described embodiments, but should be defined only by the following claims and all equivalents.

Claims

1. A method for producing a polyurethane foam, comprising the following steps: a step of mixing a polyol and a plurality of hydrophobic copper oxide particles to form a polyol slurry; and a step of mixing the polyol slurry with methylene diphenyl diisocyanate to form a polyurethane foam The manufacturing method including.

2. The method according to claim 1, wherein the hydrophobic copper oxide particles are surface-modified copper oxide particles.

3. The method according to claim 2, wherein the copper oxide particles are surface-modified by reaction with a fatty acid.

4. The method according to claim 3, wherein the fatty acid is stearic acid.

5. The method according to claim 4, wherein the fatty acid contains a hydrophobic tail.

6. The method according to claim 2, wherein the copper oxide particles are surface-modified by reaction with oleic acid or coconut oil.

7. The method according to claim 2, wherein the copper oxide particles are surface-modified by reaction with a saturated fatty acid.

8. The method according to claim 1, wherein the polyurethane foam has a density greater than 3.0 pounds per square foot.

9. The method according to claim 1, further comprising a step of mixing at least one of a polymer thickener and a surfactant with the polyol and copper oxide.

10. The method according to claim 1, further comprising a step of reacting a surface portion of the copper oxide with a hydrophobic compound.

11. The method according to claim 1, wherein the hydrophobic compound is a fatty acid.

12. A polyurethane; and A plurality of copper oxide particles, at least a part of which has a hydrophobic coating on its surface, An antimicrobial polyurethane article containing.

13. The antimicrobial polyurethane article according to claim 12, wherein the polyurethane contains monomer units derived from at least one methylene diphenyl diisocyanate.

14. The antimicrobial polyurethane article according to claim 12, which is a polyurethane foam and has a density greater than 2.0 pounds per square foot.

15. The antimicrobial polyurethane article according to claim 12, which is a polyurethane foam and has a density greater than 3.0 pounds per square foot.

16. The antimicrobial polyurethane article according to claim 12, which is at least one of a mattress, a pillow, a carpet padding, a heat insulating material, a seat cushion, a vehicle seat, a wound dressing, a kitchen sponge, a sponge, a packaging, footwear including an insole, a laminate, a fiber, and a spandex fiber.