Patent Application
20190367380
The present invention relates to a microstructured multicomposite copper microparticle with antibacterial and/or biocidal activity that comprises in its structure 5 different types of copper compounds, all regular and crystalline, that explain the advantageous structural properties of the microparticle: Antlerite Cu3+2(SO4)(OH)4, Brochantite Cu4+2SO4(OH)6, Chalcantite Cu+2SO4.5H2O, Natrochalcite NaCu2+2(SO4)2OH.H2O, Copper sulfate hydroxide Cu3(SO4)2(OH)2.4H2O/2CuSO4.Cu(OH)2. The homogeneous composition of the microstructured multicomposite microparticle enables differential release speed characteristics of each one of the 5 different copper compounds to be uniform throughout the material in which they are incorporated, with each copper compound carrying out its antibacterial and/or biocidal effect individually at the same time in all of the places where the microparticle structure is present. Due to the inclusion of the five copper compounds in the same microstructured microparticle, we have homogeneous and uniform distribution of these compounds, which also enables fewer doses to be used, contributing to the translucent characteristic of the material.
The production process of the microstructured multicomposite microparticle consists in the preparation of a dispersion of copper hydroxide in gel state, which is emulsified with a solution of copper sulfate in water as the solvent, this dispersion/solution is immediately followed by a spray drying process in a hot air flow.
The use of the microparticle in the production of materials with antibacterial and/or biocidal activity is also disclosed.
The scope of the invention also includes a concentrated polymeric composition (masterbatch) which comprises the described microstructured multicomposite copper microparticle and a polymer or resin, which can be included in other/various materials to impart antibacterial and/or biocidal activity to them. Particularly, the masterbatch can be utilized in the structuring of multilayer sheets with antibacterial and/or biocidal activity.
The appearance of multidrug-resistant microorganisms has triggered the search for novel compounds which are capable of combating bacterial proliferation without acquiring resistance as is the case with the agents currently being used (Betancourt et al. 2016).
The development of nanotechnology has permitted the creation of materials which can have dimensions within the order of micrometers and nanometers, materials which show very promising characteristics as antimicrobial agents (Chatterjee et al. 2014). The nano- and microparticles, have the ability to act independently or as transporters of other molecules, and by virtue of their characteristics of surface area, volume, and structure, can trigger biological responses (Chatterjee et al. 2014).
Copper is among the chemical elements used to form nano and microparticles. Copper compounds and complexes have been used in formulations and products for the disinfection of liquids, solids, and human tissues (Delgado et al. 2011).
Different documents from the prior art have described the incorporation of copper compounds and copper nano-/microparticles into solids with the objective of producing a product with antibacterial and/or biocidal properties.
In the case of textile-type materials and fibers, the document U.S. Pat. No. 8,183,167 (B1) discloses fabric substrates which are covalently bonded with copper and/or silver nanoparticles which show antimicrobial activity.
The document U.S. Pat. No. 5,458,906 A presents a method for treating biodegradable substrates with antibacterial compounds, among them, copper. U.S. Pat. No. 7,754,625B2 describes an antimicrobial textile that comprises one or more natural or synthetic fibers or filaments that are combined with an antimicrobial agent, where said antimicrobial agent comprises a predominant quantity of a water-soluble zinc salt in combination with at least one source of antimicrobial silver ions and at least one source of copper ions.
The document U.S. Pat. No. 7,169,402B2 presents an antimicrobial and antiviral polymeric material that has microscopic particles of ionic copper encapsulated in it, which are included in the surface of the product to be formed.
In the document CL201300332 (WO 2014117286 A1) an impregnable matrix of vegetable, animal, or synthetic origin or mixtures thereof in different proportions which contains an antimicrobial compound corresponding to Cu4SO4(OH)6 is disclosed.
The document CL201500921 discloses a cellulose-based material that incorporates an antibacterial agent corresponding to a copper compound, mixed copper microparticles or nanoparticles. A method for manufacturing a cellulose-based material which includes steps for the addition of copper microparticles or nanoparticles is included.
The document CL 201503652, in turn, presents a translucent adhesive film which shows surface-protecting antibacterial activity, adhesive film which comprises nanoparticles of copper, chitosan, gelatin, and glutaraldehyde.
Various materials have been developed specifically for the food industry for packaging foods. The documents WO 2014001541 A1, WO 2012127326 A1, and WO 2000053413 A1 describes the production of polymeric materials that contain copper particles for the purpose of use in food packaging with antibacterial and/or biocidal properties. The materials envisaged in these documents include copper compounds or copper particles, with copper oxide primary among them.
Although there are several previous antecedents with reference to the addition of copper compounds and copper microparticles supported on different types of carrier or mixtures of them in matrices and polymeric materials to grant antibacterial properties, the proposals vary with respect to the oxidation state of copper. The oxidation state of the copper will influence the solubility of the kind of copper, and, consequently, in the release behavior thereof from the polymeric material; what is more, the different carriers used tend to make the essential particles bulky.
With regards to antibacterial and/or biocidal materials for packaging or containers, it is necessary to produce quick and instantaneous release in the container to inhibit the surface growth of microorganisms on the foods which cause them to deteriorate and are present at the time of packaging (RAM bacteria). Medium-term release is also necessary to inhibit outbreaks caused by the particular handling of each operation, temperature changes, and storage, among other things. In practice, it is therefore necessary that a material include copper microparticles having a solubility (Kps) that enables it's immediate, ongoing, and residual release over time, maintaining concentrations of copper that allow it to have an antibacterial and/or biocidal effect, but which also are copper concentrations which allow avoidance of the toxicity associated with this compound or excess migration to the food products in contact. In other words, a material with improved antibacterial and/or biocidal effect at lower concentrations of copper is required.
The specific composition of the microparticle of the present invention enables translucent materials to be produced, an important characteristic in the case of food packaging materials, because the particle does not have any carrier to support it and render it bulky gives translucency to the material.
In the case of the present invention, the production of a microparticle of copper which comprises 5 types of copper compounds, each having different solubilities (Kps) is proposed. On the one hand, the presence of copper sulfate compounds (Kps=4×10−36), which dissociate instantaneously on contact with moisture—a quick-release copper compound—will make it possible to produce a direct and immediate antibacterial and/or biocidal effect in the material containing it. On the other hand, the presence of copper hydroxide compounds (Kps=2.2×10−14)—a compound with less solubility—will impart to it a bactericidal and/or biocidal effect that is sustained over time. This microparticle offers the advantage that it has the ability to provide 5 different copper compounds, with their own, non-transferable qualities and advantages, which are provided in the same place or physical space upon being introduced into the final polymer or wherever they are placed, providing all of the qualities and advantages of each one of the individual compounds at the same time in the same place and physical space, which is an indispensable condition when low dosages are required, to avoid a loss of translucency and releases of copper that could pass to the products in contact, without diminishing its antibacterial and/or biocidal efficacy, being efficient over time, all in the same place, in a homogeneous form and in contact with foods or other types of products or surfaces where high levels of free circulating copper ions are not required. Thus, the antibacterial and/or biocidal effect of each of the 5 copper compounds can be provided homogenously and at low dosages due to the specific composition of the microparticle according to the present invention.
corresponds to antlerite Cu3+2(SO4)(OH)4,
corresponds to brochantite Cu4+2SO4(OH)6,
corresponds to chalcantite Cu+2SO4.5H2O,
corresponds to natrochalcite NaCu2+2(SO4)2OH.H2O, and
corresponds to hydrated copper sulfate hydroxide Cu3(SO4)2(OH)2.4H2O/2CuSO4.Cu(OH)2.
The present invention relates to a microstructured multicomposite copper microparticle that comprises in its composition 5 different types of copper compound: Antlerite Cu3+2(SO4)(OH)4, Brochantite Cu4+2SO4(OH)6, Chalcantite Cu+2SO4.5H2O, Natrochalcite NaCu2+2(SO4)2OH.H2O and Hydrated copper sulfate hydroxide Cu3(SO4)2(OH)2.4H2O/2CuSO4.Cu(OH)2.4H2O, all regular and crystalline in shape, which give the advantageous structural properties of the microparticles. The microparticle that is part of the scope of the invention has a defined size of between 5 and 50 μm, particularly between 10 and 40, and more particularly between 10 and 15 μm.
The above described microparticle is produced by the means of a method that comprises the following steps:
a) Preparing a solution of solubilized copper sulfate in distilled water in a ratio of 1:10 w/w.
b) Adding to the solution obtained in step a) a 10% w/v sodium hydroxide solution and distilled water until a solution with a pH of between 4 and 6 is obtained.
c) After 24 hours, separating the supernatant and the precipitate which is a copper hydroxide gel;
d) The precipitate in a gel state obtained in step c) is emulsified in a copper sulfate solution in distilled water prepared in a ratio of 1:5 w/v;
e) Subjecting the emulsion obtained in step d) to a drying process, preferably by means of a spray dryer at an inlet temperature of preferably between 220° C. and 280° C. and an outlet temperature of preferably between 80° C. and 100° C.
In carrying out step d) using a dryer of the type spray dryer with the temperatures in the indicated ranges, microparticles are produced in which each of them contains different types of copper compound: Antlerite Cu3+2(SO4)(OH)4, Brochantite Cu4+2SO4(OH)6, Chalcantite Cu+2SO4.5H2O, Natrochalcite NaCu2+2(SO4)2OH.H2O and Hydrated copper sulfate hydroxide Cu3(SO4)2(OH)2.4H2O/2CuSO4.Cu(OH)2.4H2O, with this not being comparable with a mixture of components or an agglomeration thereof, but rather, on the contrary, being a single microstructured microparticle that comprises the 5 compounds.
The scope of the invention includes a concentrated polymeric composite for use in the plastics industry or in other materials (called masterbatch) that comprises the described copper microparticle and a polymer or resin, which can be included in materials in order to impart antibacterial and/or biocidal activity to them. Particularly but not exclusively, the masterbatch can be utilized in the formation of multilayer sheets having antibacterial and/or biocidal activity.
The technical problem which the present invention intends to resolve is the provision of a novel type of microparticle that comprises 5 types of copper whose regular, crystalline, and microstructured composition enables a controlled release of copper ions that give it antibacterial and/or biocidal properties. The kinetics of the differential release of the 5 different copper compounds included in the microparticle make possible a primary antibacterial and/or biocidal effect on contact and an antibacterial and/or biocidal effect that is sustained over time thanks to the secondary and subsequent release of other kinds of copper present therein. On the other hand, the copper microparticle with these characteristics can form part of a concentrated polymeric composition or masterbatch that can be incorporated during the extrusion process into the molten polymer used to form rigid molds, fibers, filaments, and sheets for the purpose of producing a film, sheet, or structure that incorporates the microparticle and has antibacterial and/or biocidal activity with the technical characteristics and advantages described above.
This structured microparticle can also be used directly or in a mixture to produce an antibacterial and/or biocidal effect in the places in which it is placed.
The targeted placement of the 5 types of copper as part of one and the same microparticle provides substantial technical advantages in terms of its degree of dissociation and release. What is more, the addition of this copper microparticle comprising this multiple composition improves the dispersion of the microparticles, since the Antlerite Cu3+2(SO4)(OH)4, Brochantite Cu4+2SO4(OH)6, Chalcantite Cu+2SO4.5H2O, Natrochalcite NaCu2+2(SO4)2OH H2O and Hydrated copper sulfate hydroxide Cu3(SO4)2(OH)2.4H2O/2CuSO4.Cu(OH)2.4H2O will be present in the same proportions throughout the material, which enables antibacterial and/or biocidal activity to be achieved with advantageously very small doses and with a homogeneous distribution of the 5 types, which also contributes to the translucency of the materials in which they are incorporated, such as in packaging, covering films, or rigid molds, among other things. In addition, all of the compounds that make up the microparticle are in a crystalline form, maintaining an ordered, non-amorphous structure that enables a specific general structure with particular properties to be defined.
The invention also provides for the use of the copper microparticle and of a concentrated polymeric composition (masterbatch) as being useful in the preparation of materials having antibacterial and/or biocidal activity on contact and as a sustained effect. The microstructural configuration of the components comprised by the microparticle allows that when the material comes into contact with bacterial and/or pathogenic agent, it is simultaneously in direct contact with the copper compounds, excercising an immediate antibacterial and/or biocidal effect on contact. The presence of 5 different copper compounds with different solubilities and/or dissociations also enables a sustained effect of the antibacterial and/or biocidal activity of the disclosed microparticle to exist.
When it is noted in the present invention that the material has “biocidal activity,” it means that the microparticle is capable of inhibiting the development and growth of bacteria and fungi.
When it is stated that the material has “antibacterial activity,” it means that the microparticle inhibits or impedes the proliferation of bacteria.
In the present invention, the term “microstructured” means that the material—the microparticle in this case—consists of a set of phases or components that form it. In the area of materials science, it is said that the microstructure of a material determines its properties.
In the present invention, the term “multicomposite” means that the microparticle comprises at the same time a certain group of different compounds.
The term “masterbatch” refers to a concentrated polymeric composition that comprises a pre-mixture of the elements that will be incorporated into the material to be produced.
The materials that fall within the scope of the invention can include but are not limited to polymers, fibers, fabrics, types of glasses, resins, among others. The polymers include but are not limited to polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), ethylene-vinyl acetate (EVA rubber), among others.
In one embodiment of the invention, the microparticle can further comprise other metallic and nonmetallic compounds which have antibacterial action. These compounds include but are not limited to zinc compounds, lead compounds, cadmium compounds, silver compounds, among others.
The exemplary applications presented below illustrate one embodiment of the present invention without limiting the scope thereof.
The copper hydroxide that makes up the microparticles is prepared by alkalizing a copper sulfate solution containing 100 g/l of pentahydrated copper sulfate, which should produce a completely soluble solution. It is then necessary to dilute sodium hydroxide or another alkali with an OH base to 10% in water; this solution is added slowly and under stirring to the copper sulfate solution that was prepared until a pH of between 4 and 6 is reached, with the following reaction being produced:
CuSO4(ac)+2Na(OH)(ac)→Cu(OH)2(s)+Na2SO4(ac)
The reaction produces a precipitate of copper hydroxide in the solution in a gel state, and the supernatant is removed after 24 hours.
The resulting precipitate, which contains copper hydroxide, is emulsified in a copper sulfate solution in a ratio of 1:5. This suspension containing a solubilized ionic phase of copper sulfate and another in gel form such as copper hydroxide is subjected to a drying process using a spray dryer at an inlet temperature of between 220 and 280° C. and outlet temperature of 80° C. to 100° C.
To characterize the structure, size, and distribution of the copper microparticles produced by means of the protocol described in example 1, a scanning electron microscope (SEM) analysis was performed.
The SEM analysis was performed using the scanning electron microscope (SEM), Zeiss model EVO MA 10 using EDS mode with the Penta FET Precision detector, Oxford Instruments X-act. This analysis consisted in scanning representative specimens of the powder of (solid) copper microparticles and selecting a representative area in order to determine the elemental composition of the microparticle.
From the SEM images at different magnifications, it was observed that the particle has a regular spherical shape and a heterogeneous size distribution (
With regard to the size of the particles, four independent representative areas of the images taken from two independent specimens of the particles were evaluated. It was determined that the particles have a micrometric size of between 7-22 micrometers (see table 1).
In order to determine the specific chemical composition of the microparticle and to determine the oxidation states of the types of copper contained, an X-ray diffraction analysis was performed. Based on this analysis, an X-ray diffraction pattern was determined by the presence of various compounds (
In order to define the compounds present in the microparticle, the crystalline powder PDF-2 database was consulted and compared with the pattern obtained. It was determined that the microparticle of the invention is composed of 5 types of copper compound: Antlerite, Brochantite, Chalcantite, Natrochalcite, and Hydrated copper sulfate hydroxide (table 2).
The microparticle described in example 2 can be included in different polymeric materials and resins to form multilayer fibers and sheets. In this example, the protocol followed in preparing the concentrated polymeric composition (masterbatch) and the conditions for the inclusion thereof in resins and polymers are described.
To prepare the masterbatch, a premixture of the polymeric material and the microparticle is prepared. For this, the resin or polymeric material is subjected to pulverization in a mill and then cold-mixed with the microparticle.
The premixture is molten at temperatures between 120 and 250° C., depending on the type of resin or polymer: Polypropylene (PP), polyethylene (PE), PET, EVA rubber, and passed through a pellet extruder, which results in a pellet referred to as masterbatch.
The masterbatch can be added to the process of the extrusion of molten polymer used to form rigid or flexible polymers such as fibers, filaments, and sheets. The sheets that are produced by means of this procedure can correspond to multilayer structures in which each sheet has a thickness of between 5 and 120 μm, more specifically of between 5 and 30 μm; that is, it is possible to form a final material that can contain 2, 3, and even 5 of these layers of polymeric resins such as PE, PA, PP and/or PET.
To evaluate the antibacterial and/or biocidal effect of the multilayer material with microstructured copper microparticles, a test was performed consisting of the addition of a bacterial culture that had been grown previously on the surface of the multilayer material made up of different polymers. The antibacterial and/or biocidal effect on Escherichia coli and Staphylococcus aureus was evaluated.
The multilayer material was incubated for 24 hours at the temperature required for the growth of bacteria. Once the incubation period had lapsed, a count was performed of the colony-forming units on the material, and this was compared to a material that did not contain copper microparticles. Two types of sheeting were tested depending on the type of polymer added to the masterbatch: 1) sheeting made of polypropylene and copper microparticles (2% w/w added to a masterbatch); and 2) sheeting made of ethylene-vinyl acetate (EVA rubber) with microstructured copper microparticles added into a masterbatch.
The results indicate that, when the colony-forming unit (CFU) count for the sheeting composed of polypropylene and microstructured copper microparticles (2% w/w added to a masterbatch) is compared to the control sheeting that does not include the components of the masterbatch, the sheeting with copper microparticles shows a 99% reduction in the quantity of CFUs, with the bacterial count having been reduced by 3 orders of magnitude (table 3). In the case of the sheeting composed of ethylene-vinyl acetate (EVA rubber) and copper microparticles, an equivalent phenomenon was observed, reflecting a decrease in the CFU count for the bacteria tested on the sheeting that comprises the masterbatch in relation to the control material (table 4).
Escherichia coli (CFU)
Staphylococcus aureus (CFU)
Escherichia coli (CFU)
Staphylococcus aureus (CFU)
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/IB2018/053819 | May 2018 | US |
| Child | 16358384 | US |
