AU2004320908A8 - Method of producing metal-containing particles - Google Patents

Description

WO 2006/031229 PCT/US2004/029891 METHOD OF PRODUCING METAL-CONTAINING PARTICLES CROSS REFERENCE TO RELATED APPLICATION [0001] This application claims the priority of United States provisional patent application number 60/501, 084, filed September 9, 2003.

.FIELD OF THE INVENTION [00021 This invention is directed generally to particles, and more particularly to methods of making micro-particles and/or nano-particles.

BACKGROUND OF THE INVENTION 100031 There has been a great deal of attention in recentryears given to the hazards of bacterial contamination from potential everyday exposure. With' such an increased consumer interest in this area, manufacturers have begin introducing antimicrobial agents within various household products and articles. For instance; certain brands of polypropylene cutting boards, liquid soaps, etc., all contain antimicrobial compounds.

100041 In addition, the risk of bacterial infection is also prevalent in medical instances. For example, a variety of medical articles are designed particularly for contact with a patient's bodily fluids. The duration of this contact may be relatively short, as is typical with wound dressings, or may be long term, as is typical with prosthetic heart valves implanted into the body of a recipient. Some articles such as catheters may have either short term or relatively long term contact. Other articles typically having relatively short term contact with the patient include, without limitation, burn dressings and contact lenses. Other articles typically having long term contact with a patient.include, without limitation, implanted prostheses.

[00051 Contact of articles with bodily fluids creates a risk of infection. This risk may be very serious and even life threatening. In addition, considerable costs, and longer or additional hospital stays may result due to. infection. For example, infections associated with dressings may increase the seriousness of the injury for bum victims.

JWP195340C;2 WO 2006/031229 PCT/US2004/029891 Also, infection associated with an implanted prosthesis may necessitate replacement of the device.

100061 Accordingly, the prior art has attempted to examine methods to help reduce the risk of bacterial infection and/or to prevent infection from even occurring. One approach has been through the use of anti-microbial agents and/or inicrobiocides.

100071 The most popular antimicrobial for many articles is triclosan. Although the incorporation of such a compound within liquid or }polymeric media has been relatively simple, other substrates, including the surfaces of textiles and fibers, have proven less accessible. There has a long-felt need to provide effective, durable, and long-lasting antimicrobial characteristics, for textile surfaces, in particular on apparel fabrics, and on film surfaces. Such proposed applications have been extremely difficult to accomplish with triclosan, particularly when wash durability is a necessity (triclosan easily.washes off any such surfaces). Furthermore, although triclosan has proven effective as an.

antimicrobial compound, the presence of chlorines within such a compound causes skin irritation which makes the utilization of such with fibers, films, and textile fabrics for Sapparel uses highly undesirable.

[0008] Furthermore, there are commercially available textile products comprising acrylic and/or acetate fibers co-extruded with triclosan (for example Celanese markets such acetate fabrics under the name Microsafe T and Acordis,markets such acrylic fibers, under the tradename Amicorr), However, 'such an application is limited to those types of fibers; it does not work at all for natural fibers and specifically does not work for and/or within polyester, polyamide, cotton, spandex, etc., fabrics. Furthermore, this coextrusion procedure is very expensive. In addition, the zone of inhibition for the antimicrobial agent is limited in these applications.

100091 Silver-containing inorganic microbiocides have recently been 'developed and utilized as antimicrobial agents on and within a plethora of different substrates and surfaces. In particular, such microbiocides have been adapted for incorporation within -melt spun synthetic fibers, as taught within Japanese unexamined Patent Application No.

H 1-124729, to provide certain fabrics which selectively and inherently exhibit antimicrobial characteristics. Furthermore, attempts have been made to apply such Sspecific microbiocides on the surfaces of fabrics and yars with little success.from a iWPi9340:21 WO 2006/031229 PCT/US2004/029891 durability standpoint. A topical treatment with such compounds has never been successfully applied as a durable finish or coating on a fabric.or yam substrate.

[0010] There have been improvements in the area of fiber technology that permit the formation of silver textiles in an efficient and/or cost-effective manner. However, these manners are still directed to the formation of fibers and fabrics having silver thereon, In some instances, these fabrics and fibers are not useful as the size of the fabric or fiber is too big for the selected application.

[0011 Accordingly, what is needed is a method of preparing metal-based particles that have greater utility than prior art anti-microbial solutions. Also what is needed is a method for producing micro-sized and/or nanb-sized particles containing silver.

SUMMARY OF THE INVENTION 00121'. The present invention provides a method of producing metal-containing particles. The metal-cohtaining particles are micro-sized and/or nano-sized particles.

The metal is complexed with an alkali agent to form the particles. In one embodiment, the metal is silver and the particles include silver hydroxide.' The particles have antimicrobial properties. For embodiments wherein silver is used, the particles may also provide anti-fungal properties, anti-static properties, and/or conductive properties. The particles may range in size from about 0.01 to about 300 pm.

[0013] These and other embodiments are described in more detail below.

DETAILED DESCRIPTION OF THE INVENTION (00141 The present invention is more particularly described in the following description and examples that are intended to be. illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. As used in the specification and in the claims, the singular form and "the" may include plural referents unless the context clearly dictates otherwise. Also, as used in the specification and in the claims, the term "comprising" may include the embodiments "consisting of" and "consisting essentially of." [00151 The present invention provides a method of preparing metal-based particles. In one aspect, the method is used to form micro-sized and/or hano-sized 4WPI95340;2t WO 2006/031229 PCT/US2004/029891 particles that include a metal. In one embodiment, the metal is silver. These micro-sized and/or nano-sized particles have utility in a wide variety of different applications due to their size. Additionally, these particles retain the anti-microbial, anti-fungal, anti-static, and/or conductive properties of the metal used. As a result, micro-sized and/or nanosized particles including silver offer one or more properties such as antirmicrobial, antistatic and/or conductive.

[00161 Accordingly, in one aspect, the present invention provides a method of making micro-sized and/or nano-sized metal-containing particles. In one embodiment, the metal is silver. In alternative embodiments, the metal may be copper, alumiinum, zinc, nickel, or the like.' The method makes micro-sized and/or nano-sized particles that contain a metal, such as silver. As used herein, "micro-sized particles" are particles that have a diameter of from about I to about 300 wrn. As used herein, "nano-sized particles" are particles that have a diameter of from about 0.01 to about I p.m. Depending on different process parameters, the method may be used to form micro-size particles only, nano-sized particles only, or a combination thereof, with the resulting mixture either being used as a mixture, or further including a separation step to sort the particles into different size ranges. One example of such a separation step is -a screening step to separate the particles into different sizes.

.[00171 The methods of the present invention form these metal-containing particles using a series of process steps, although not all process steps are necessary for each embodiment. The first step is to take a source of the metal, such as silver nitrate powder for embodiments wherein silver particles are to be formed, and dissolve it in water. '.In one embodiment, the water is de-ionized water. In-an alternative embodiment, a predissolved silver nitrate solution may be used provided the amount of water in the solution is known. The table below references to different embodiments for various amounts of silver nitrate and water that may be used in an embodiment wherein the source of silver is silver nitrate and de-ionized water is used.

JWPi19534;21 WO 2006/031229 PCIT/US2004/029891 Amount of Silver Nitrate in gm per liter of DI water SFirst Embodiment about 3 to about 500 Second Embodiment about 50 to about 350 Third Embodimefnt about 100 to about 200 Fourth Embodiment about 150 [00181 The above mentioned solution may then treated with an alkali solution. In one embodiment, the alkali solution is sodium hydroxide. Sodium hydroxide may be used due to its great tendency to complex with the metallic solution. However, any alkali solution that is able to complex with the metallic solution used in a particular embodiment may be used in the present invention. In this embodiment, the metallic solution is silver nitrate dissolved in Dl water. Other alkali solutions that may be used include, but are not limited to, ammonium hydroxide.

[00191 The table below references to different embodiments of the present invention for various amounts of sodium 'hydroxide that may. be used in those emboditments wherein sodium hydroxide is the alkali solution. It should be noted that the starting point to make the solution is 50% sodium hydroxide solution (50:50 v/v) which is readily available from multiple vendors, ml of NaOH from 50:50 First Embodiment about 10 to about 500 Second Embodiment about 50 to about 300 Third Embodiment about 75 to about 150 Fourth Embodiment about 100 [00201 The reaction may take place at room temperature, or at a temperature of from about 15 to about 30° C. During the reaction, the alkali solution complexes ivith the metal to form a.precipitate containing the metal. In those embodiments wherein sodium hydroxide is used, brown precipitate is formed as the sodium hydroxide is added. The solution may be stirred while the precipitate is forming. After all the alkali solution is added, the resultant mixture may be allowed to settle down for a period of time to permit settling of any precipitate. The amount of time permitted for settling may vary, but may be from about 5 to about 15 minutes.

tWP195340;2j WO 2006/031229 PCTJ/S2004/029891 [0021] After settling, the precipitate is .then removed. The precipitate may be filtered using standard filter paper, such as a Buckner funnel. Depending on the pH of the solution, the solution may be neutralized. As the alkali solution will generally increase the pH to above 7, an acid may be used to bring the solution to a pH of approximately 7.

In one embodiment, sulfuric acid may be used, although other acids may also be used including, but not limited to, hydrochloric acid and nitric acid, among others. .Bringing the pH of the solution to about 7 is beneficial in that it will facilitate easy processing from waste treatment point of view, although this step is not necessary in the formation of the micro-sized and nano-sized, particles of the present invention.

[0022] The precipitate is then rinsed with water, such as deionized water. The water is; beneficially,'used to wash the precipitate thoroughly. Washing of the precipitate helps facilitate nano- and micro-sized particles of the complexed metal precipitate to be collected in pure form. In an embodiment wherein silver is the metal and sodium hydroxide is the alkaii solution, the resulting precipitate includes nano- and micro-sized particles of silver hydroxide. The rinsing may be done anywhere, including within the funnel itself.

[00231 The precipitate may then be dried in a conventional oven or other drying mechanism until the precipitate is substantially dry. In one embodiment, the drying temperature is from about 50 to about 90" C. After drying the precipitate, the resulting product includes the micro-sized and/or nano-sized particles of the present invention.

10024]. It is to be understood that since the micro-sized and/or nano-sized particles of the present invention include silver, the beneficial properties of silver are retained, even with the smaller size of the particles. As a result, the particles of the present invention may be used in any application taking advantage of one or more of the beneficial properties of silver. These properties, include, but are not limited to, antimicrobial, anti-fungal, anti-static, conductive, electromagnetic, interference (EMI) shielding, filtration, or a combination thereof.

[0025] The present invention will now be further described through examples. It is to be understood that these examples are non-limiting and are presented to provide a better understanding of various embodiments of the present invention.

jWP195340;21 WO 2006/031229 PCT/US20041029891

EXAMPLES

Example I |00261 75 gm of silver nitrate salt was weighed out. This was then dissolved in 500 ml of deionized water at room temperature (app. 22 Upon dissolving the salt the final volume could raise up to 600 ml. 100 ml of 50:50 NaOH was added slowly to the silver nitrate solution. A brown precipitate formed. immediately. The solution with precipitate was then stirred with a rod. The mixture was then allowed to settle down for about 10 minutes. The precipitate was then filtered using standard filter paper using a buckner funnel, 0027] The solution was neutralized using'50% sulfuric acid. The precipitate was then rinsed with deionized water using 50 100 ml at a time through the buckner funnel 5000 ml of DI water was used to rinse the precipitate in this example [0028] The resulting precipitate was then dried in a conventional oven until dry at temperature maintained between about 60 to about 80' C.

[00291 Approximately 46 gnm of brown silver, hydroxide nano- and micro-sized particulates were collected, Example 2 O0030] The resultant nano powder obtained from Example 1 was then subjected to high heat (i.e..greater than about >100' C) for a few minutes. This heating resulted in the formation of shiny white micro- and nano-sized particles of silver. The resultant powder weighed approximately 43 gm, Example 3 j00311 The resultant powder from Example I was then incorporated into the outer surface of a hydrogel bandage at the ratio of 10:1 by Weight of the hydrogel to the weight of the silver powder. The surface was dipped to apply the hydrogel mixture to the surface. This sample was then subjected to Dow Coming Corporate Test Method 0923 using Staphylococcus aureus ATCC 6538. After 1 hour the organism'count CFU/ml reduced from 1.6 x 10i at zero time to <10. The percentage reduction was >99.99%. As (WPW95340;21 WO 2006/031229 PCTIIJS2004/029891 a result, the anti-microbial properties of the micro- and nano-sized silver hydroxide particles is clearly seen.

Example 4 [00321 The resultant powder from Example 1 was then incorporated into the outer surface of a hydrogel bandage at the ratio of 10:1 by weight of the hydrogel to the weight of the silver powder and then subjected to the same test as Example 3 over a period of 4 hours.. The reduction was again 99.99%. This clearly suggests the enormous surface area of the nano particles and its effectiveness in small quantities.- Example [00331 The resultant powder from Example I -was then incorporated into the outer surface of a hydrogel bandage at the ratio of 100:1 by weight of the hydrogel to the weight of the silver powder and then subjected to the same test as Eiample 3 over a period of 4 hours. The reduction was an amazing 94%, again indicating the effectiveness of the nano particles as well as -the surface area benefits. The test result also indicates a great zone of inhibition of the nano particles.

0034] The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of this invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of this invention.

Claims (15)

1. A method of making metal-containing particles comprising: forming a solution of a metal in a solvent; mixing the metal solution with an alkali solution to form a precipitate containing the metal; separating the precipitate; and drying the precipitate to form the metal-containing particles.

2. The method of claim 1, wherein the metal is selected from silver, copper, nickel, zinc, aluminum, or a combination thereof.

3. The method of claim 2, wherein the metal is silver,

4. The method of claim 1, wherein metal-containing particles from about 0.01 um to about 300 pm. The method of claim 4, wherein metal-containing.particles from about I pm to about 300 unm.

6. The method of claim 4, wherein metal-containing particles from about 0.01- um to about I anm. range ii size range in size range in size

7. The method of claim 1, fiarther comprising the step of rinsing the precipitate with water prior to drying.

8. The method of claim 1, wherein the solution of a metal in a solvent comprises silver nitrate powder dissolved it in water. WO 2006/031229 PCT/US2004/029891

9. The method of claim 8, wherein the amount of silver nitrate in grams per liter of water is from about 3 to about 500. The method of claim 9, wherein the amount of silver nitrate in grams per liter of water is from about 100'to about 200.

11. The method of claim 1, wherein the alkali solution is selected from sodium hydroxide, ammonium hydroxide, or a combination thereof.

12. The method of claim 11, wherein the alkali solution is sodium hydroxide.

13. The method of claim 12, wherein the sodium hydroxide solution is a sodium hydroxide solution. 14, A particle made by the method of claim 1.. The particle of claim wherein the metal is selected from silver, copper, nickel, zinc, aluminum, or a combination thereof,

16. The particle of claim 15, wherein the metal is silver.

17. The particle of claim 14, wherein metal-containing particles range in size from about 0.01 4m to about 300 inm.

18. The particle of claim 17, wherein- metal-containing particles range in size from about I ,m to about 300 m.

19.' The particle of claim 1.7, wherein metal-containing particles range in size from about 0.01 pm to about 1 Imn. A silver hydroxide particle comprising: WO 2006/031229 PCT/US2004/029891 silver complexed with a hydroxide; wherein the particle is from about 0,01 gmn to about 300 p~m in diameter.