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

Abstract

A copper microparticle with antibacterial and/or biocidal activity, wherein each microparticle has a regular, crystalline and microstructured composition that comprises 5 different copper compounds: Antlerite Cu.sub.3.sup.+2(SO.sub.4)(OH).sub.4, Brochantite Cu.sub.4.sup.+2SO.sub.4(OH).sub.6, Chalcantite Cu.sup.+2SO.sub.4.5H.sub.2O, Natrochalcite NaCu.sub.2.sup.+2(SO.sub.4).sub.2OH.H.sub.2O and Hydrated copper sulfate hydroxide Cu.sub.3(SO.sub.4).sub.2(OH).sub.2.4H.sub.2O/2CuSO.sub.4.Cu(OH).sub.2, with the microparticle having a size of between 5 and 50 m. A process for preparing copper microparticles with antibacterial and/or biocidal activity. A concentrated polymeric composition (masterbatch) with antibacterial and/or biocidal activity that is incorporated during the extrusion process to molten polymers for forming rigid or flexible products such as fibers, filaments, and sheets. A use of a copper microparticle with antibacterial and/or biocidal activity. A use of a concentrated polymeric composition (masterbatch) with antibacterial and/or biocidal activity.

Claims

1. A copper microparticle with antibacterial and/or biocidal activity, characterized in that each microparticle has a regular, crystalline and microstructured composition that comprises 5 different copper compounds: Antlerite Cu.sub.3.sup.+2(SO.sub.4)(OH).sub.4, Brochantite Cu.sub.4.sup.+2SO.sub.4(OH).sub.6, Chalcantite Cu.sup.+2SO.sub.4.5H.sub.2O, Natrochalcite NaCu.sub.2.sup.+2(SO.sub.4).sub.2OH.H.sub.2O and Hydrated copper sulfate hydroxide Cu.sub.3(SO.sub.4).sub.2(OH).sub.2 4H.sub.2O/2CuSO.sub.4.Cu(OH).sub.2, with the microparticle having a size of between 5 and 50 m.

2. The copper microparticle with antibacterial and/or biocidal activity as set forth in claim 1, characterized in that the microparticle has a size of between 10 and 40 m.

3. The copper microparticle with antibacterial and/or biocidal activity as set forth in claim 1, characterized in that the microparticle has a size of between 10 and 15 m.

4. The copper microparticle with antibacterial and/or biocidal activity as set forth in claim 1, characterized in that it can further comprise other metallic and nonmetallic antibacterial compounds.

5. A process for preparing copper microparticles with antibacterial and/or biocidal activity as set forth in claim 1, characterized in that it 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 is obtained that has a pH of between 4 and 6; 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.

6. A concentrated polymeric composition (masterbatch) with antibacterial and/or biocidal activity that is incorporated during the extrusion process to molten polymers for forming rigid or flexible products such as fibers, filaments, and sheets, characterized in that it comprises copper microparticles as set forth in claim 1 and at least one polymer or resin.

7. The concentrated polymeric composition (masterbatch) as set forth in claim 4, characterized in that the polymer or resin corresponds but is not limited to polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), ethylene-vinyl acetate (EVA rubber), polystyrene (PS), styrene-butadiene rubber (SBR), polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), methacrylate (PMMA), polyester, aliphatic polyamides, polyterephthalamides, aramides (aromatic polyamides), rigid and flexible polyurethanes, silicone.

8. A use of a copper microparticle with antibacterial and/or biocidal activity as set forth in claim 1 characterized in that it is useful in the preparation of materials having antibacterial and/or biocidal activity on contact and with sustained effect.

9. A use of a concentrated polymeric composition (masterbatch) with antibacterial and/or biocidal activity as set forth in claim 6, characterized in that it is useful in the preparation of materials having antibacterial activity on contact and with sustained effect.

10. A use of a concentrated polymeric composition (masterbatch) with antibacterial and/or biocidal activity as set forth in claim 6, characterized in that it is useful in the preparation of multilayer sheets having antibacterial activity on contact and with sustained effect.

11. The copper microparticle with antibacterial and/or biocidal activity as set forth in claim 4, wherein the metallic antibacterial compounds are zinc compounds, lead compounds, cadmium compounds, and silver compounds.

12. The method according to claim 5, wherein the drying process is by means of a spray dryer.

13. The method according to claim 12, wherein the spray dryer has an inlet temperature between 220 C. and 280 C. and an outlet temperature between 80 C. and 100 C.

Description

DESCRIPTION OF THE FIGURES

[0020] FIG. 1Scanning electron microscope images of a specimen of copper microparticles of the invention. a) Image obtained at a magnification of 10.00 K; b) Image at a magnification of 2.50 K, c) Image at a magnification of 500y d) Image obtained at a magnification of 100.

[0021] FIG. 2Determination of elemental composition of copper microparticles of the invention by means of scanning electron microscope coupled with an EDS detector. In a), the result of the mapping of the elements that make up the microparticle is presented: carbon, oxygen, sulfur, and copper; b) shows a diagram of the elemental composition of the copper microparticles of the invention.

[0022] FIG. 3X-ray diffraction pattern of specimen of copper microparticle of the invention. The difractogram represented by corresponds to antlerite Cu.sub.3.sup.+2(SO.sub.4)(OH).sub.4, corresponds to brochantite Cu.sub.4.sup.+2SO.sub.4(OH).sub.6, corresponds to chalcantite Cu.sup.+2SO.sub.4.5H.sub.2O, corresponds to natrochalcite NaCu.sub.2.sup.+2(SO.sub.4).sub.2OH.H.sub.2O, and corresponds to hydrated copper sulfate hydroxide Cu.sub.3(SO.sub.4).sub.2(OH).sub.2.4H.sub.2O/2CuSO.sub.4.Cu(OH).sub.2.

DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention relates to a microstructured multicomposite copper microparticle that comprises in its composition 5 different types of copper compound: Antlerite Cu.sub.3.sup.+2(SO.sub.4)(OH).sub.4, Brochantite Cu.sub.4.sup.+2SO.sub.4(OH).sub.6, Chalcantite Cu.sup.+2SO.sub.4.5H.sub.2O, Natrochalcite NaCu.sub.2.sup.+2(SO.sub.4).sub.2OH.H.sub.2O and Hydrated copper sulfate hydroxide Cu.sub.3(SO.sub.4).sub.2(OH).sub.2.4H.sub.2O/2CuSO.sub.4.Cu(OH).sub.2.4H.sub.2O, 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 m, particularly between 10 and 40, and more particularly between 10 and 15 m.

[0024] 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.

[0025] 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 Cu.sub.3.sup.+2(SO.sub.4)(OH).sub.4, Brochantite Cu.sub.4.sup.+2SO.sub.4(OH).sub.6, Chalcantite Cu.sup.+2SO.sub.4.5H.sub.2O, Natrochalcite NaCu.sub.2.sup.+2(SO.sub.4).sub.2OH.H.sub.2O and Hydrated copper sulfate hydroxide Cu.sub.3(SO.sub.4).sub.2(OH).sub.2.4H.sub.2O/2CuSO.sub.4.Cu(OH).sub.2.4H.sub.2O, 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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 Cu.sub.3.sup.+2(SO.sub.4)(OH).sub.4, Brochantite Cu.sub.4.sup.+2SO.sub.4(OH).sub.6, Chalcantite Cu.sup.+2SO.sub.4.5H.sub.2O, Natrochalcite NaCu.sub.2.sup.+2(SO.sub.4).sub.2OH H.sub.2O and Hydrated copper sulfate hydroxide Cu.sub.3(SO.sub.4).sub.2(OH).sub.2.4H.sub.2O/2CuSO.sub.4.Cu(OH).sub.2.4H.sub.2O 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.

[0030] 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.

[0031] 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.

[0032] When it is stated that the material has antibacterial activity, it means that the microparticle inhibits or impedes the proliferation of bacteria.

[0033] In the present invention, the term microstructured means that the materialthe microparticle in this caseconsists 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.

[0034] In the present invention, the term multicomposite means that the microparticle comprises at the same time a certain group of different compounds.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] The exemplary applications presented below illustrate one embodiment of the present invention without limiting the scope thereof.

EXEMPLARY APPLICATIONS

Example 1: Production of Copper Microparticle

[0039] 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:

CuSO.sub.4(ac)+2Na(OH).sub.(ac).fwdarw.Cu(OH).sub.2(s)+Na.sub.2SO.sub.4(ac)

[0040] The reaction produces a precipitate of copper hydroxide in the solution in a gel state, and the supernatant is removed after 24 hours.

[0041] 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.

Example 2: Characterization of Copper Microparticle

[0042] 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.

[0043] 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.

[0044] From the SEM images at different magnifications, it was observed that the particle has a regular spherical shape and a heterogeneous size distribution (FIG. 1 a-d). By means of the EDS detector that was coupled with the microscope, the elemental composition of the microparticle was determined, and it was established that it is made up of the elements copper, sulfur, and oxygen (FIG. 2a-d).

[0045] 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).

TABLE-US-00001 TABLE 1 Representative size of copper particles Specimen MB-1 (m) Specimen MB-2 (m) Measurement 1 10.52 7.480 Measurement 2 19.44 10.88 Measurement 3 7.61 21.94 Measurement 4 7.363 13.61 Average 11.23 13.48

[0046] 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 (FIG. 3).

[0047] 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).

TABLE-US-00002 TABLE 2 Chemical composition of copper microparticle Name of compound Chemical structure Antlerite Cu.sub.3.sup.+2(SO.sub.4)(OH) .sub.4 Brochantite Cu.sub.4.sup.+2SO.sub.4(OH).sub.6 Chalcantite Cu.sup.+2SO.sub.45H.sub.2O Natrochalcite NaCu.sub.2.sup.+2(SO.sub.4).sub.2OHH.sub.2O Hydrated copper Cu.sub.3(SO.sub.4).sub.2(OH).sub.24H.sub.2O/2CuSO.sub.4Cu(OH).sub.24H.sub.2O sulfate hydroxide

Example 3: Preparation of the Masterbatch. Addition of the Copper Microparticles to Multilayer Polymer Sheets

[0048] 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.

a) Preparation of Concentrated Polymeric Composition (Masterbatch)

[0049] 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.

[0050] 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.

b) Inclusion of the Masterbatch in the Process of the Extrusion of Molten Polymer to Form a Multilayer Material.

[0051] 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 m, more specifically of between 5 and 30 m; 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.

Example 4: Antibacterial and/or Biocidal Effect of the Multilayer Polymeric Material with Microstructured Copper Microparticle

[0052] 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.

[0053] 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.

[0054] 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).

TABLE-US-00003 TABLE 3 Count of colony-forming units on sheeting made of polypropylene and copper microparticles (2% w/w). Indicator strain Escherichia coli (CFU) Staphylococcus aureus (CFU) Sampling time 0 h 24 h 0 h 24 h Control 1.6 10.sup.5 1.6 10.sup.5 3.6 10.sup.5 3.6 10.sup.5 material Sheeting 2.7 10.sup.2 4.3 10.sup.2 polypropylene 2% copper masterbatch % reduction >99% >99%

TABLE-US-00004 TABLE 4 Count of colony-forming units on sheeting composed of ethylene- vinyl acetate (EVA rubber) and copper microparticles. Indicator strain Escherichia coli (CFU) Staphylococcus aureus (CFU) Sampling time 0 h 24 h 0 h 24 h Control 8.9 10.sup.5 3.3 10.sup.6 5.0 10.sup.5 6.9 10.sup.7 material EVA rubber 2.5 10.sup.2 5.6 10.sup.4 % reduction >99% >99%