Method for preparing an antimicrobial solid composite material containing copper

Abstract

The invention relates to the field of surface coatings having antibacterial properties. More particularly, the invention relates to a method for preparing a solid composite material comprising copper particles conferring antimicrobial properties thereto, said copper particles forming a gradient within the material. The resulting material is intended to be applied to various surfaces in order to limit the spread of pathogens by contact.

Description

METHOD FOR PREPARING AN ANTIMICROBIAL SOLID COMPOSITE CONTAINING COPPER

[0001] The invention relates to the field of surface coatings with antimicrobial properties. More particularly, the invention concerns a method for preparing a solid composite material comprising copper particles that impart antimicrobial properties. The resulting material is intended to be applied to various surfaces to limit the spread of pathogens by contact. Scope of the invention

[0002] Antimicrobial materials have attracted increasing interest over the past few decades, in response to global concerns about hygiene, viral infections such as COVID-19, and bacterial infections, including nosocomial infections, and the fight against bacterial resistance.

[0003] Metallic surfaces, particularly those based on copper, silver, and zinc, are known for their inherent antimicrobial properties.

[0004] Used in the form of nanoparticles or ions, silver is incorporated into polymers or textiles for its antimicrobial properties. Effective at very low concentrations, it has a long lifespan under controlled conditions. Its drawbacks include its high cost and environmental concerns related to the dispersion of nanoparticles, for example, as a source of toxicity for aquatic ecosystems.

[0005] It is observed that silver behaves similarly to stainless steel or plastic, despite meeting an antibacterial standard (ISO 22196) in 24 hours at 35°C, with a humidity level exceeding 90%. However, under less aggressive conditions closer to real-world use (lower temperature and humidity), silver remains inert and therefore lacks antibacterial properties. For example, it cannot meet the NF ISO 7581 standard (elimination of bacteria in 1 hour between 18°C ​​and 25°C and a relative humidity between 30% and 65%). See the article: HT Michels, JO Noyce, and CW Keevil, "Effects of temperature and humidity on the efficacy of methicillin-resistant Staphylococcus aureus challenged antimicrobial materials containing silver and copper," Letters in Applied Microbiology, vol. 49, no. 2, p. 191-195, August 2009

[0006] Used in alloys and in its pure form, copper is widely studied for its potent antimicrobial properties. It works by destroying the cell membranes of microorganisms and generating free radicals that are harmful to bacterial DNA. Its effectiveness is proven against a wide range of bacteria and viruses, and its effect is long-lasting. For example, the SARS-CoV-2 virus, responsible for COVID-19, can survive for about 24 hours on cardboard, and even two to three days on plastic or stainless steel. But in contact with copper, the virus is only detectable for four hours.

[0007] A technology exists that leverages the antimicrobial properties of copper, which is incorporated into a cold-applied coating. The product is composed of a copper alloy (over 90% pure) and polymers, forming a specific paint capable of destroying bacteria, viruses, and other germs. This liquid product combines a cross-linked polyester resin (40-50%) and a copper-phosphorus alloy containing 92% copper (50-60%); it is applied at a thickness of 200 µm in certified facilities. Its bactericidal activity complies with the NF S90-700 standard. The paint is dark gray in color. Disadvantages of the state of the art

[0008] State-of-the-art copper-based bactericidal compositions are liquid and must be applied in a very thin layer to a surface. This results in fragility, as the coating can be damaged by contact (repeated rubbing, scraping, etc.), leading to a localized loss of its biocidal effect. When the substrate is exposed, areas of microbial growth can occur. There is a risk of reduced coating effectiveness over time, as well as galvanic corrosion, depending on the nature of the substrate.

[0009] Furthermore, prior art compositions are based on plastics and other petrochemical-derived materials such as polyester-type polymer resins like polyethylene terephthalate (PET). The manufacturing process for such materials involves potentially toxic, flammable, or corrosive substances and has a negative impact on the environment.

[0010] The invention aims to provide a solid, copper-based antimicrobial composite material. To this end, the inventors have developed a process for preparing a solid resin-based composite material in which the copper is arranged in a density gradient to obtain a high density on one face of the material.

[0011] Thus, the invention relates to a process for preparing a solid antimicrobial composite material comprising copper, comprising the steps of:

[0012] a. Mixing a resin with a hardener

[0013] b. Addition of copper particles in powder form to said resin before hardening, in a ratio of between 0.1:99.9 and 80:20 by weight between the quantity of copper and the quantity of said resin, and homogenization by mixing

[0014] c. Pouring said mixture into a pouring frame configured to delimit a pouring volume having a minimum height of at least 0.2 mm, said height corresponding to the thickness of the poured resin

[0015] d. Vacuum-sealing of said mixture by applying a vacuum of between 3 x 10 -3 and 10 -1 mbar for a period of between 1 min and 30 min

[0016] e. Hardening of the mixture to obtain a solid composite material

[0017] f. Surface abrasion of the lower surface of the composite material on which the copper density is highest, so as to expose at least partially copper particles present in said material

[0018] in which the copper particles are smaller than 400 microns.

[0019] The resulting solid antimicrobial composite material and its use for preventing the transmission of pathogenic microorganisms and disinfecting contaminated surfaces are also part of the invention. Advantages of the invention

[0020] The present invention provides a process for preparing a new solid antibacterial composite material based on copper integrated in a resin to address the hygiene, health and environmental problems currently at work.

[0021] The composite material is preferably a bio-based resin, at least partially, to address environmental concerns. Choosing a bio-based resin implies certain constraints compared to petrochemical-based plastics. For example, bio-based resins can be more sensitive to humidity and oxygen, which can affect their vacuum curing. Bio-based resins, particularly those based on vegetable oils, may have a longer curing time or require different catalysts to achieve optimal polymerization. These constraints have been assessed and taken into account.

[0022] Bio-based resins, particularly those made from vegetable oils, generally emit fewer volatile organic compounds (VOCs) than petrochemical resins. This is an advantage when working in sensitive environments where VOCs must be minimized. Bio-based resins also offer the benefit of reduced CO₂ and other chemical emissions during their manufacturing and vacuum curing.

[0023] The composite material made from bio-based resin is a product with no toxicological risk, is odorless, and does not cause allergic reactions. This choice helps reduce the use of fossil fuels, including petroleum and its derivatives.

[0024] The antimicrobial properties of the composite material according to the invention are remarkable. They are based on several characteristics: The size of the copper particles can vary depending on the embodiment while still producing an antimicrobial effect, but it has been demonstrated in particular that a size smaller than 63 microns provides a larger contact surface for an equivalent quantity of larger particles. This embodiment is particularly advantageous. The arrangement of the copper particles in a density gradient within the composite material. The material is essentially "polarized" following the vacuum sealing step during which the copper particles migrate towards the lower surface of the resin. A higher copper density is therefore observed on the lower surface, producing a "copper plate" effect associated with strong antimicrobial activity.This achieves the same effects as copper but with a composite material offering high flexibility and workability. Furthermore, the surface cost is lower than that of copper.

[0025] Thus, the arrangement of copper particles in a gradient is highly advantageous because: it allows for strong antimicrobial efficacy, meeting and even exceeding that established by the current standard; and this efficacy is achieved with a significantly reduced quantity of copper compared to a composition of equivalent efficacy in which the copper concentration is identical throughout the material. Indeed, the weight concentration of copper in the total resin can be less than 5% without affecting the surface antimicrobial efficacy, which remains compliant with the requirements defined by standard NF S90-700. The mechanical properties of the material are little or not at all affected by the presence of copper.

[0026] The composite material complies with the NF S90-700 standard (equivalent to the NF ISO 7581 standard), meaning that it allows the elimination of 4 reference bacteria in less than one hour.

[0027] The material possesses interesting mechanical and aesthetic properties: it is sufficiently flexible and strong to be molded. It allows for the molding of parts ranging in thickness from 0.2 mm to 100 mm or more. Its coppery color on the face with the highest copper density gives it a strong visual identity. This visual property can be adjusted depending on the percentage of copper in the material.

[0028] The antibacterial composite material can be used in many everyday applications such as under the coating of phone cases or other regularly handled objects, or in broader spectrum applications such as the disinfection of surfaces in hospitals or public places, especially high-traffic areas such as door handles, grab bars and medical devices. DETAILED DESCRIPTION OF THE INVENTION

[0029] A first object of the invention relates to a process for preparing a solid antimicrobial composite material comprising copper, comprising the steps of:

[0030] a. Mixing a resin with a hardener

[0031] b. Addition of copper particles in powder form to said resin before hardening, in a ratio of between 0.1:99.9 and 80:20 by weight between the quantity of copper and the quantity of said resin, and homogenization by mixing

[0032] c. Pouring said mixture into a pouring frame configured to delimit a pouring volume having a minimum height of at least 0.2 mm, said height corresponding to the thickness of the poured resin

[0033] d. Vacuum-sealing of said mixture by applying a vacuum of between 3 x 10 -3 and 10 -1 mbar for a period of between 1 min and 30 min

[0034] e. Hardening of the mixture to obtain a solid composite material

[0035] f. Surface abrasion of the lower surface of the composite material on which the copper density is highest, so as to expose at least partially copper particles present in said material

[0036] in which the copper particles are smaller than 400 microns.

[0037] In the context of the present invention, the resin used may be a thermosetting resin, a thermoplastic resin or an elastomeric resin.

[0038] A thermosetting resin is a resin which, through polymerization and / or crosslinking, particularly under the effect of heat, a curing agent or a catalyst, forms a crosslinked matrix exhibiting high mechanical and dimensional stability.

[0039] A thermoplastic resin exhibits thermally reversible behavior and can be melted and reformed repeatedly.

[0040] An elastomeric resin exhibits marked elastic behavior, characterized by a large capacity for reversible deformation.

[0041] In all cases, the resin is chosen so as to be compatible with the casting process and subsequent surface treatment steps, including surface abrasion intended to expose particles incorporated in the resin matrix.

[0042] In a preferred embodiment of the invention, the resin is thermosetting

[0043] These thermosetting, thermoplastic, or elastomeric resins can be produced through various channels. Petrochemical-based resins are derived from fossil resources, such as epoxy, polyester, polyurethane, polyolefin, or acrylic resins. Alternatively, resins can be bio-based, meaning they are obtained wholly or partly from renewable resources, for example, from sugar derivatives, vegetable oils, lignin, cellulose, or organic acids of biological origin. Commonly, resins are hybrids, comprising a mixture of petrochemical and bio-based constituents, in order to combine mechanical, thermal, and processing properties suited to the requirements of the process and the intended application.The choice of the nature and origin of the resin is made according to the performance requirements, manufacturing constraints and, where applicable, environmental or regulatory objectives, without the invention being limited to a particular type of resin.

[0044] Preferably, the process is implemented in an eco-responsible manner by choosing a bio-based resin as the base resin for the composite material.

[0045] In terms of percentage, a resin is considered bio-based when the percentage of bio-based carbon, measured according to ASTM D6866 or ISO 16620-2, reaches a significant threshold. While there is no universally accepted percentage, a resin is generally considered bio-based when the percentage of bio-derived carbon exceeds 20-25%. However, some certifications or labels require higher levels, such as 50% or more, to make specific claims. The remainder of the resin may consist of non-bio-based components, often of fossil origin, depending on the formulation and intended application.

[0046] For the purposes of this invention, "bio-based resin" means a resin comprising at least 30% bio-based carbonaceous material. Preferably, this resin comprises at least 40%, more preferably at least 50%, or even at least 60%, and even more preferably at least 70%, or even at least 80%, of bio-based carbonaceous material. It can be 100% bio-based. These plant-derived components include, for example, monomers derived from plants, polymers obtained from sugars, oils, lignin, and other natural substances… such as sunflower esters, caprolactones, sunflower polyols, sorbitol, oleopolyols….

[0047] Numerous bio-based resins are described in the literature and commercially available. Furthermore, the field of bio-based resins is expanding to meet the growing demand for more environmentally friendly products. All of these resins are available to those skilled in the art when selecting a bio-based resin to implement the invention.

[0048] Examples of bio-based resins include: Bio-based epoxy resins; For example, Super Sap® (Entropy Resin) contains up to 40% bio-based carbon and is made from vegetable oils and agricultural residues. Bio-based polyester resins, such as Polyola® resin, contain up to 69% bio-based carbon and are based on raw materials such as vegetable oils. Bio-based polyurethane resins, such as Bioresin® resin, contain 70% bio-based carbon and are composed of a mixture of oleo-polyols and caprolactones. Bio-based polyamide (Nylon) resins, such as Rilsan® resin, can contain 100% bio-based carbon (for Rilsan® PA11) and are made from castor oil, which is entirely bio-based.PLA (polylactic acid) resins, such as Ingeo® resin, which contains 100% bio-based carbon derived from corn starch or sugarcane. Bio-based thermoplastic polyurethane (TPU) resins, such as Desmopan®, which contains up to 60% bio-based carbon and uses bio-based sources such as vegetable oils. Bio-based acrylic resins, such as Arkema Pebax® Rnew resin, which contains 20 to 50% bio-based carbon and partially uses bio-based polyols. Bio-based polyolefin resins, such as Braskem Green PE® resin, which contains 100% bio-based carbon, namely polyethylene made from sugarcane ethanol. Bio-based polycarbonate resins, such as Lexan® resin, which contains up to 50% bio-based carbon and includes renewable raw materials. certified mass-balance.Bio-based alkyd resins, such as Synolac® resin which contains between 60 and 80% bio-based carbon material and uses vegetable oils as a raw material.

[0049] In a preferred embodiment of the invention, the resin used is a bio-based polyurethane resin, a bio-based epoxy resin or a bio-based polyester resin.

[0050] Other resins of interest include polyacrylate, alkyd, polyamide and vinyl ester resins.

[0051] In a particular embodiment exemplified below, the resin used is thermosetting; it is prepared according to the manufacturer's recommendations or according to the practices of those skilled in the art, by mixing a resin base and a hardener. For general guidance, the weight ratio between the quantity of resin and hardener may be between 30 / 70 and 60 / 40.

[0052] The desired characteristics of the resin are described below in the paragraph relating to the second object of the invention.

[0053] Copper powder must be added before the resin hardens.

[0054] The amount of copper powder added to the resin corresponds to a ratio of between 0.1:99.9 and 80:20 by weight between the amount of copper and the amount of resin. In order to limit the amount of copper used, the ratio is between 0.1:99.9 and 50:50, preferably between 0.1:99.9 and 20:80, or even between 0.1:99.9 and 10:90. In particular embodiments, this ratio is between 0.2:99.8 and 80:20 or between 0.3:99.7 and 80:20 or between 0.5:99.5 and 80:20 or between 1:99 and 80:20 or between 2:98 and 80:20 or between 3:97 and 80:20 or between 5:95 and 80:20. According to other variants of the invention, for example if it is desired to enhance the coppery visual appearance, the ratio can be between 20:80 and 50:50, but also between 30:70 and 70:30, or between 40:60 and 70:30, or between 50:50 and 70:30.

[0055] It should be noted that the composite material will generally be more flexible with smaller quantities of copper incorporated.

[0056] The size of the copper particles is less than 400 microns. Preferably, the size (roughly equivalent to the notion of diameter when the particles are spherical) of the particles is less than 300 microns, or even less than 200 microns and preferably less than 100 microns.

[0057] The small size of the particles increases their surface area, resulting in a greater antimicrobial effect than that obtained with the same quantity of larger diameter particles. To optimize the antimicrobial effect, it is best to choose copper particles with an average size of less than 63 microns.

[0058] In a preferred embodiment, the copper particles (100%) have a size less than or equal to 63 microns and at least 50% of the particles have a size less than or equal to 45 microns.

[0059] Preferably, the size of the copper particles is such that: between 95% and 100% of the particles have a size less than or equal to 45 microns and between 0% and 5% of the particles have a size between 45 and 63 microns.

[0060] Preferably, the copper particles have a purity level of at least 90%. Even more preferably, the copper particles have a purity level of 95% or higher, or even 99%. The purer the copper powder, the greater its antimicrobial effect.

[0061] Homogenization is achieved by simple mechanical mixing, after which the mixture is poured into a suitable mold. Indeed, the composite material cannot be applied by spray or brush; it must be deposited into a mold or other suitable support for vacuum curing. Furthermore, the poured material must be at least 0.2 mm thick. The composite material typically has a thickness between 0.2 mm and 100 mm, preferably between 0.3 mm and 50 mm. In a particular embodiment, the thickness ranges from 0.3 mm to 2 mm; its thickness is chosen according to its mechanical properties and the intended application. The material obtained after molding is stable, and its rigidity depends on the type of resin used.

[0062] To obtain a casting of a specific thickness, the resin mixture containing copper particles is poured into a casting frame configured to define a pouring volume with a minimum height of at least 0.2 mm, this height corresponding to the thickness of the poured resin. The frame thus defines a pouring volume whose height is determined by the height of the frame itself. The frame can be in the form of a mold.

[0063] The casting can be done in a steel casting frame, particularly one made of alloy steel. Alloy steels are mixtures of different metals, such as nickel, copper, and aluminum.

[0064] The resin mixture containing the copper particles is then evacuated using a vacuum bell jar, vacuum bags, vacuum chambers, flexible membranes, vacuum infusion systems, or other vacuum device to create a copper gradient throughout the composite material. The vacuum applied in the device is between 3 x 10 -3 and 10 -1 mbar, preferably between 3 x 10 -3 and 10 -2 The vacuum time varies between 1 and 30 minutes, but generally 1 to 20 minutes is sufficient to obtain a gradient.

[0065] A stabilization of the gradient is observed after vacuum immersion, with the highest copper density found on the lower surface of the material. Vacuum immersion thus corresponds to a cold metallization of the lower surface of the composite material. In a preferred embodiment of the invention, the vacuum immersion step is performed at least twice successively.

[0066] During the vacuum process, the particles gradually arrange themselves, with a higher concentration in the lower part of the material due to their greater density compared to the resin and the outgassing of the material, with air rising and being replaced by copper particles. Thus, the composite material obtained by this process exhibits a higher copper density on its lower surface than the average density in the composite material before vacuuming.

[0067] After the vacuum sealing stage, the process includes a curing stage to obtain a solid composite material. This stage is adapted to the nature of the resin used and must allow for its complete hardening through polymerization. The hardening of

[0068] Resins generally involve a heating step that helps to finalize polymerization.

[0069] It should be noted that the copper gradient is not affected by the solidification of the composite material. Thus, the gradient obtained during vacuum sealing is stable.

[0070] Interestingly, the copper density achieved on the lower surface can give the composite material an antimicrobial effect equivalent to that of a copper plate. However, and very interestingly, the amount of copper required to achieve this effect is significantly less than that which would be needed if the particles were homogeneously distributed. The process thus makes it possible to obtain a "copper plate" type antimicrobial effect with a lower amount of copper than prior art processes. This characteristic contributes to the ecological and economic advantages of the process. An antimicrobial effect is obtained with copper concentrations in the material as low as 0.1% by weight of the total resin. In specific embodiments, the amount of copper introduced into the resin is greater than or equal to 0.2%, 0.3%, 0.4%, 0.5%, 1%, 2%, 3%, 4%, 5%, 7%, or 10%.

[0071] To optimize the contact area with the copper contained in the composite material, a superficial abrasion of the material's underside is carried out after hardening. This abrasion can be achieved, for example, by sanding or polishing.

[0072] Thus, a superficial abrasion is carried out on the lower surface of the composite material where the copper density is highest, so as to expose at least partially the copper particles present in said material. This is a gentle abrasion, so as not to alter the cohesion of the matrix, but sufficient to bring the copper particles to the surface.

[0073] A second object of the invention relates to a solid antimicrobial composite material comprising: 20-99.9% by weight of a resin defined by a viscosity between 50 and 15,000 mPa·s at 23°C measured with a single-cylinder rotary viscometer, and a density between 0.3 and 1.5 g / cm³ 3 a Shore A hardness between 30 and 900, 1-80% by weight of copper particles

[0074] characterized in that: said material is in the form of a molded plate with a thickness of at least 0.2 mm; the size of said copper particles in said material is less than or equal to 400 microns; said material has at least partial exposure of copper particles on one of its surfaces.

[0075] The arrangement of copper particles in the composite material is done according to a density gradient oriented positively towards one of the faces of said material, the one which corresponds to the lower face at the end of the preparation process.

[0076] Furthermore, the composite material exhibits a difference in color intensity between its two sides. The intensity of this coppery color is directly proportional to the amount of copper contained in the material. Generally, the side with a more intense coppery color corresponds to the side with the highest copper density, while the less intensely coppery side, usually not coppery at all, corresponds to the side with the lowest copper density. This orientation of the material results from the arrangement of the copper particles within the material according to a density gradient. The side with the highest copper content has a matte appearance when the copper content exceeds 25%, whereas the side with the lowest copper content exhibits reflections and a certain sheen characteristic of the resin.When the base resin is transparent, the composite material has a translucent appearance when the quantity by weight of copper is less than 25%.

[0077] This composite material can be obtained by the process according to the invention.

[0078] Thermosetting, thermoplastic or elastomer resin can be chosen from the resins mentioned above.

[0079] Preferably, the resin is thermosetting and 70% or more bio-based (it contains at least 70% plant-based components). In a preferred embodiment of the invention, it is a bio-based polyurethane resin.

[0080] For example, the viscosity of the thermosetting resin before curing can range from 50 to 15,000 mPa·s at 23°C, measured with a single-cylinder rotary viscometer. Preferably, the viscosity is between 100 mPa·s and 10,000 mPa·s, more preferably between 500 and 5,000 mPa·s, and most preferably between 800 and 3,000 mPa·s. As an example, it can range from 1,000 to 1,400 mPa·s.

[0081] The density of the thermosetting resin is between 0.3 and 1.5 g / cm³ 3 Preferably, the density is between 0.5 and 1.3 g / cm³ 3 .

[0082] The Shore A hardness of the thermosetting resin is between 30 and 90. Preferably, it is between 45 and 60.

[0083] The composite material has a minimum thickness of 0.2 mm. Preferably, its thickness is between 0.2 mm and 100 mm, and more preferably between 0.3 mm and 3 mm. The thickness is chosen based on the type of resin, the shape of the mold, and the desired mechanical properties for the intended use. The thickness allows for adjustments to the material's flexibility, strength, and workability. It is supplied as a molded sheet, the shape of which is generally adapted to the application without modification.

[0084] The amount of copper powder present in the composite material corresponds to a ratio of between 0.1:99.9 and 80:20 by weight between the amount of copper and the amount of resin. This ratio represents the average relative amounts of the two components in the composite material. However, what characterizes the presence of copper in the composite material is the arrangement of the copper particles along a density gradient oriented positively towards one of the faces of the material, the face corresponding to the bottom at the end of the preparation process. The inventors have demonstrated that the face with the highest copper density has an antimicrobial effect equivalent to that of copper; this can be described as a "copper plate" effect.

[0085] This arrangement of copper within the material is also visually apparent, to a greater or lesser degree depending on the percentage of copper present. Indeed, the material exhibits a copper-colored surface corresponding to the surface with the highest copper density and a weakly colored or non-copper-colored surface corresponding to the surface with the lowest copper density; this orientation of the material results from the arrangement of these copper particles within the material according to a density gradient.

[0086] Thus, the copper effect manifests itself: by an antimicrobial effect equivalent to that obtained via a copper plate – technical effect; by a visual effect reproducing the appearance of a copper plate or its characteristic coppery nuances – visual effect.

[0087] The matte, coppery color present on one side of the material, typically when the copper content exceeds 25%, is both a technical and visual characteristic of the composite material; it contributes to the material's visual identity and unique character. However, it is possible to add coloring agents to modify its appearance. Furthermore, the resin may not be transparent, without affecting its antimicrobial properties.

[0088] The size of the copper particles present in the composite material is less than 400 microns.

[0089] Preferably, the particle size is less than 300 microns, or even less than 200 microns, and more preferably less than 100 microns.

[0090] In a particularly preferred embodiment, the copper particles (100%) have a size less than or equal to 63 microns and at least 50% of the particles have a size less than or equal to 45 microns.

[0091] Preferably, the size of the copper particles is such that: between 95% and 100% of the particles have a size less than or equal to 45 microns and between 0% and 5% of the particles have a size between 45 and 63 microns.

[0092] Preferably, the copper particles present in the composite material have a purity level of at least 90%. Even more preferably, the copper particles have a purity level of 95% or higher, or even 99%.

[0093] The composite material has high antimicrobial properties. It is effective against bacteria, as evidenced by its compliance with standard NF S90-700 (now NF ISO 7581), and also against viruses. Laboratory results indicate disinfection of the antimicrobial material in 1 hour; the results even exceed the standard with an average elimination of 94.4% of bacteria in just 3 minutes.

[0094] A third object of the invention relates to the use of the solid antimicrobial bio-based composite material as defined above for the prevention of the transmission of pathogenic microorganisms and the disinfection of contaminated surfaces.

[0095] It can be applied to objects in the form of cases, for example for phones, but also to flat surfaces such as buttons in elevators, door handles, grab bars in public spaces…

[0096] With an elimination of more than 90% of bacteria and viruses in 3 min instead of a passive presence of at least 15 days, this material makes it possible to eliminate the history of contaminations of several days and to have a minimal bacterial presence and therefore to prevent transmissions by contact.

[0097] The present invention will be better understood by reading the following examples, which are provided by way of illustration and should in no way be considered as limiting the scope of the present invention. DESCRIPTION OF THE FIGURES

[0098] Schematic representation of the process for preparing the antimicrobial composite material

[0099] Bactericidal activity of the antibacterial composite material against E. coli as a function of time EXAMPLES

[0100] EXAMPLE 1: Method for preparing an antibacterial composite material according to the invention

[0101] A schematic representation of one embodiment of the process is presented at the and an example is described below.

[0102] A copper powder with a particle diameter of 63 microns or less is used.

[0103] A thermosetting resin is prepared, for example from a bio-based polyurethane resin of 70% of the oleopolyole and caprolactone type (viscosity: 1000-1400 mPa.s at 23°C, density: 1.1 g / cm3, Shore A hardness: 45-60).

[0104] The copper powder is then mixed with the bio-based casting resin and a suitable hardener with good miscibility (quantity as specified by the supplier, e.g., 50 / 50) in a 50 / 50 ratio. The mixture is immediately poured into an aluminum mold and placed under a vacuum chamber connected to a dedicated vacuum pump. A vacuum of 3 x 10⁻¹¹ bar is applied. - 3A pressure of mbar is applied for 15 minutes. A second vacuum application allowed for complete degassing of the composite material and the creation of a stable copper gradient. The material is then cured by heating for 30 minutes to 1 hour 30 minutes at 45°C and then demolded.

[0105] The underside of the material, where the copper density is highest (darker copper color), is then sanded to bring out the copper particles.

[0106] The resulting composite material has interesting mechanical properties: its modulus is approximately 29.8 MPa, closer to that of an elastomer (typical modulus = 1 MPa) than to that of a rigid polymer (typical modulus = 3,000 MPa for PS, 1,500 MPa for PP, and 200 to 500 MPa for LDPE). The material has a tensile strength of 3.82 MPa, and the post-fracture deformation is almost zero, at 18.9%.

[0107] The material thus prepared comes in the form of a molded plate, more or less flexible depending on the choice of resin, and which can be applied to a contact surface.

[0108] EXAMPLE 2: Antimicrobial effect of the composite material

[0109] Validated bactericidal effect on 4 bacteria: conforms to standard NF S90-700

[0110] In order to validate the bactericidal activity of the composite material, following the criteria of the NF S90-700: 2019 standard, tests were carried out on the 4 reference bacterial strains and the reduction of the bacterial load measured at 1 hour.

[0111] The results are summarized in Table 1.

[0112] Escherichia coli ATCC 10536 Enterococcus hirae ATCC 10541 Pseudomonas aeruginosa ATCC 15442 Staphylococcus aureus ATCC 6538 Quantity of bacteria deposited at t=0h (CFU) 2.25 E+05 2.63 E+05 3.85 E+05 1.87 E+05 Quantity of viable bacteria remaining at t=0h (3 min) (CFU) 1.48 E+02 2.09 E+01 3.02 E+02 6.03 E+00 Bactericidal activity at t=0h (3 min) (Log10 reduction) 2.17 1.32 2.48 0.78 Percentage reduction of bacterial population after ≤ 3 min of contact (%) 99.32 % 95.21 % 99.67 %83.40 %Quantity of viable bacteria remaining at t=1h (CFU)2.77E+024.27E+027.51E+021.87E+03 Bactericidal activity (Log10 reduction)2.912.792.712.00 Percentage reduction in bacterial population after 1 hour of contact (%)99.88 %99.84 %99.81 %99.00 %

[0113] Table 1: Results of bacterial growth inhibition tests by contact with the antibacterial composite material.

[0114] We note a reduction of 99% or more in the quantity of bacteria for the 4 reference strains mentioned in the NF S90-700 standard in less than one hour and of more than 95% in less than 3 minutes for 3 of them, which is very fast.

[0115] After one hour, the bactericidal activity is 2.91, for example for the Escherichia coli bacterium, which represents a reduction of the bacterial population after 1 hour of contact of 99.88%.

[0116] Lamontre has a very rapid bactericidal activity: at 3 min the reduction of Log 10 is 2.17 (the target is at least 2 after one hour) for the Escherichia coli bacterium which represents a reduction in bacterial population after a contact time ≤ 3 min is 99.32%.

[0117] The bactericidal activity is higher than that required by the NF S90-700 standard.

[0118] Furthermore, when comparing the bactericidal activity of the material against E. coli, it is found to be equivalent to that of a copper plate. See the results described in the article: Santo, CE, Taudte, N., Nies, DH, & Grass, G. (2008). Contribution of copper ion resistance to survival of Escherichia coli on metallic copper surfaces. Applied and Environmental Microbiology, 74(4), 977-986.

[0119] This result confirms that the accumulation of copper on one face of the composite material reproduces the bactericidal effect of copper, hence the "copper plate" effect of the antibacterial composite material. Virucidal effect of the composite material

[0120] Regarding the virucidal activity of the material, although it has not been validated, it is expected that the virucidal effect will also be very high by extrapolating from the antimicrobial "copper plate" effect obtained and based on the article by Warnes. – See Warnes, SL, Summersgill, EN, & Keevil, CW (2014). Inactivation of murine norovirus on a range of copper alloy surfaces is accompanied by loss of capsid integrity. Applied and environmental microbiology.

[0121] Effect of the amount of copper in the material on antimicrobial activity

[0122] The antimicrobial activity of different materials was evaluated according to current standards, based on the amount of copper present in these materials. The results are presented in Table 2.

[0123] Standard Bacterial strain Percentage of copper in the material Bactericidal activity (Log reduction) 10)Percentage reduction in the bacterial population after 1 hour of contactBactericidal activity (Log reduction > 2 Log)NF S90-700: 2019Escherichia coliATCC 1053680%-2.9199.88%OKNF ISO 7581:December 2023Escherichia coliCIP 54.12761%-3.3299.99%OKNF ISO 7581: December 2023Escherichia coliCIP 54.12736%-3.6399.99%OKNF ISO 7581: December 2023Escherichia coliCIP 54.12710%-3.2799.98%OK

[0124] Table 2: Antimicrobial effect of the composite material evaluated according to the incorporation of different percentages of copper

[0125] All the materials tested showed an antimicrobial effect in accordance with the current standard.

[0126] These results demonstrate the effectiveness of the process in creating an antimicrobial material through the application of a copper gradient. The composite material complies with the applicable standard regardless of the copper percentage tested. Very low quantities of 10% are sufficient to achieve the desired "copper plate" antimicrobial effect and suggest that a copper concentration below 10% would maintain this effect.

Claims

1. A process for preparing a solid antimicrobial composite material comprising copper, comprising the steps of: a. Mixing a resin with a hardener; b. Adding copper particles in powder form to said resin before hardening, in a ratio of between 0.1:99.9 and 80:20 by weight between the quantity of copper and the quantity of said resin, and homogenizing by mixing; c. Pouring said mixture into a pouring frame configured to delimit a pouring volume having a minimum height of at least 0.2 mm, said height corresponding to the thickness of the poured resin; ed. Vacuum-sealing said mixture by applying a vacuum of between 3 x 10 -3 and 10 -1mbar for a period of between 1 min and 30 min. Hardening of the mixture to obtain a solid composite material. Superficial abrasion of the lower surface of said composite material on which the copper density is highest, so as to expose at least partially copper particles present in said material in which the copper particles have a size of less than 400 microns.

2. A process according to claim 1 in which the copper particles have a size less than or equal to 63 microns.

3. A method according to claim 2 wherein furthermore at least 50% of the particles have a diameter less than or equal to 45 microns.

4. A method according to any one of the preceding claims, wherein the vacuum is obtained by applying a vacuum of between 3 x 10 -3 and 10 -2 mbar.

5. A process according to any one of the preceding claims, wherein said copper particles have a degree of purity of at least 90%.

6. A method according to any one of the preceding claims, wherein said resin is a thermosetting, thermoplastic or elastomer resin.

7. A process according to any one of claims 1 to 6 wherein said resin is a bio-based resin selected from a polyurethane resin, an epoxy resin, a polyester resin, a polyacrylate resin, an alkyd resin, a polyamide resin and a vinylester resin.

8. A method according to any one of the preceding claims, wherein said casting is carried out so as to obtain a resin thickness of between 0.2 and 100 mm.

9. A method according to any one of the preceding claims, wherein said resin has a viscosity of between 50 and 15,000 mPa·s at 23°C measured with a single-cylinder rotary viscometer, and a density of between 0.3 and 1.5 g / cm³. 3 and a Shore A hardness between 30 and 90.

10. A method according to any one of the preceding claims, wherein the vacuuming step is carried out at least twice successively.

11. A solid, bio-based, antimicrobial composite material obtainable by the process as defined in any one of claims 1 to 10, comprising: 20-99.9% by weight of a resin defined by: a viscosity of between 50 and 15,000 mPa·s at 23°C measured with a single-cylinder rotary viscometer; and a density of between 0.3 and 1.5 g / cm³. 3a Shore A hardness between 30 and 900, 1-80% by weight of copper particles characterized in that: said material is in the form of a molded plate of a thickness of at least 0.2 mm the size of said copper particles in said material is less than 400 microns said material has at least partial exposure of copper particles on one of its surfaces.

12. Use of the antimicrobial bio-based composite material as defined in claim 11 for the prevention of the transmission of pathogenic microorganisms and the disinfection of contaminated surfaces.

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