WO2006049478A1

WO2006049478A1 - Anti-microbial fiber products

Info

Publication number: WO2006049478A1
Application number: PCT/KR2005/003773
Authority: WO
Inventors: Hae-Jun Park; Sung Ho Kim; Hwa Jung Kim; Hae Jin Park
Original assignee: Bio Dreams Co. Ltd.
Priority date: 2004-11-08
Filing date: 2005-11-08
Publication date: 2006-05-11
Also published as: WO2006049479A1

Abstract

Disclosed is an antimicrobial composition for coating fiber products. The antimicrobial composition includes nanosized silica-silver particles in which nano-silver is bound to silica molecules and a water-soluble polymer, the nanosized silica-silver particles prepared by irradiating a solution comprising a silver slat, silicate and the water-soluble polymer with radiation rays. Also disclosed are antimicrobial fiber products coated with the composition and a method of antimicrobially treating fiber products by coating the fiber products with the composition.

Description

ANTI-MICROBIAL FIBER PRODUCTS

Technical Field

The present invention relates to an antimicrobial composition for coating fiber products comprising nanosized silica-silver particles, in which nano-silver is bound to silica molecules and a water-soluble polymer, the nanosized silica-silver particles prepared by irradiating a solution comprising a silver salt, silicate and the water-soluble polymer with radiation rays. Also, the present invention is concerned with antimicrobial fiber products coated with the composition.

Background Art

General fiber products prepared using fibers as major materials, such as blankets, sofa and socks, are problematic in that they provide a good environment for microbial growth from sweat, oils, proteins and other organic materials affixed thereto and accumulated therein through direct contact with the human body. This microbial contamination, which is accompanied by color changes of fiber products or production of offensive odors, causes various respiratory diseases or skin diseases, such as atopic dermatitis, by promoting the propagation of various harmful bacteria such as mites

Recently, xn order to prevent harmful microbes from damaging the body, antimicrobial fabrics have been developed by imparting antimicrobial properties to fiber products, and are being applied to various articles

The antimicrobial fiber products are generally manufactured mainly by coating the surface of fiber products with various antimicrobial substances A conventional method of coating fiber products with antimicrobial substances mainly employs a colorless water- soluble liquid, N,N-Dimethylformamide (DMF) or methyl ethyl ketone (MEK) , as a solvent However, DMF, used as a solvent, irritates the respiratory tract, skin, eyes, and the like. Also, DMK is very well absorbed into the body through the skin and injures the liver due to its toxicity. MEK is also a chemical compound very harmful to the human body MEK also irritates the respiratory tract, skin, eyes, and the like. When inhaled, MEK causes vomiting, difficulty m breathing, headache, drowsiness and dizziness, and in severe cases, causes central nervous system disorders The use of these harmful chemical compounds for coating antimicrobial substances generates a great quantity of environmentally harmful substances during the manufacturing of antimicrobial fibers. In addition, antimicrobial fiber products prepared usinq the solvents become very slippery when it rains or when the fiber products become wet, due to the solvents' characteristics, and have the risk of growing harmful fungi capable of generating offensive odors and causing dermatxtis. The solvents have a further problem xn that long-term use hardens fiber products.

In order to solve the aforementioned problems, fiber products having antimicrobial effects are manufactured using silver (Ag) particles. For example, Korean Design Registration No. 392113 describes an antimicrobial cloth comprising nano-silver particles and its use in fiber products. Silver (Ag) , which is known as a strong bactericidal agent, destroys unicellular microorganisms through its antimicrobial activity against enzymes performing metabolic functions m microbes (T. N. Kim, Q. L. Feng, et al. , J. Mater. Sci. Mater. Med., 9, 129 (1998)) . Heavy metals such as copper and zinc also have the same function as silver. However, silver has the strongest bactericidal effect and also has excellent effects on algae. Silver has been studied as a substitute for chloride or other toxic microbicides. To date, a variety of inorganic antimicrobial agents using silver have been developed.

Silver-based inorganic antimicrobial agents in current use are commercially available in the form of silver-supported inorganic powder, silver colloids, metal silver powder, and the like. Of them, the silver-supported inorganic powder form makes up the largest part of this demand, and this form is generally referred to as an inorganic antimicrobial agent. When silver exists in an xon state, it has good antimicrobial activity However, silver is unstable due to its high reactivity and is easily oxidized or reduced to a metal according to the surrounding atmosphere, thereby spontaneously changing m color or causing other materials to be changed in color These phenomena lead to a reduction in the duration of the antimicrobial action of silver When present in a metal or oxidized form, silver is stable in the environment but must be used m relatively large amounts due to its low antimicrobial activity

Silver, having the advantages and drawbacks as noted above, is spotlighted in the form of nanoparticles Nanoparticles are synthesized by physical methods, such as mechanical grinding and wet reduction Of the physical methods, the electrolysis technique requires high production costs, has difficulty producing nanoparticels m a large scale, and has difficulty controlling the size of formed particles In contrast, a method of preparing nanometer-sized particles by irradiation with radiation rays has the following advantages it easily controls the size, shape and size distribution of particles, it can form nanoparticles at room temperature, and it provides a simple process and thus makes mass production possible with low costs Korean Pat Registration No 0425976 discloses a method of preparing nanometer-sized silver colloids by irradiation with radiation rays and nanometer s_zed silver colloids The method of preparing silver colloids comprises dissolving a silver salt m triple distilled water, adding sodium dodecyl sulfate (SDS) , polyvinyl alcohol (PVA) , polyvinylpyrrolidone (PVP) and others as colloid stabilizers to the solution, carrying out nitrogen purging, and irradiating the resulting solution with radiation rays However, since this method produces silver colloids having a particle size greater than 100 nm, high concentrations of silver colloids should be produced for use as an antimicrobial agent against microbes, especially fungi.

In addition to the aforementioned methods, many efforts have been made to provide nano silver applicable to a broad range of fields with purposes including anti- bacteria, cleaning and deodoπzation. Despite these efforts, there is still a need for the development of a more simple process for preparing cheaper and more stable nano-silver.

Silicon (Si) , which is the second most abundant material m the earth, is taken up by plants and enhances resistance to diseases and stress therein (Role of Root hairs and Lateral Roots m Silicon Uptake by Rice J F Ma et al. Ichii Plant Physiology (2001) 127: 1773-1780, etc.) . In particular, when plants are treated with an aqueous solution of silicate, silicate displays excellent preventive effects on ma]or plant diseases including powdery mildew and downy mildew. Also, silicate promotes physiological activity of plants and improves plant growth while providing resistance to diseases and stress (Suppressive effect of potassium silicate on powdery mildew of strawberry in hydroponics T Kanco et al J GenPlant Pathol (2004) 70 207-211) etc ) However, since silica does not have direct disinfecting effects on plant pathogens, it does not exhibit positive effects when diseases develop m plants

Based on this background, the present inventors prepared nanosized silica-silver particles, m which nano silver is bound to silica molecules and a water-soluble polymer, by mixing a silver salt, silicate and a water- soluble polymer and irradiating the resulting mixture with radiation rays, and found that the nanosized silica silver particles thus prepared are uniform m size, are stable and have excellent antimicrobial effects even in very low concentrations The present inventors further found that fabrics coated with such antimicrobial particles retains antimicrobial activity even after being laundered and dried twenty times or more, thus leading to the present invention

Disclosure of the Invention

It is therefore an object of the present invention to provide an antimicrobial composition for coating fiber products comprising nanosized silica-silver particles in which nano-silver is bound to silica molecules and a water- soluble polymer, the nanosized silica-silver particles prepared by irradiating a solution comprising a silver salt, silicate and the water-soluble polymer with radiation rays

It is another object of the present invention to provide an antimicrobial fiber product coated with the composition

It is a further object of the present invention to provide a method of antimicrobialIy treating a fiber product comprising coating the fiber product with the composition

Brief Description of the Drawings

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken m conjunction with the accompanying drawings, in which

Fig Ia is a flowchart of a process of preparing nanosized silica-silver, and Fig Ib shows TEM images of nanosized silica-silver formed after irradiation with gamma rays, Fig 2 shows the colloidal stability of nanosized silica-silver m water;

Fig 3 shows the absorption spectrum of nanosized silica silver at 403 nm compared with the absorption spectra of water and silver ions, Fig 4 shows the change of nanosized silica-silver in absorbance at 403 nm according to concentrations of sodium silicate (Na₂SiO₃) ;

Fig. 5 shows the absorption spectra at 403 nm of nanosized silica-silver prepared with varying concentrations of polyvinylpyrrolidone (PVP) ;

Figs. 6a and 6b show the absorption spectra at 403 nm of nanosized silica-silver prepared with other water- soluble polymers (high levan and corn starch, respectively) ; Fig. 7 shows the absorption spectra at 403 nm of nanosized silica-silver according to radiation doses;

Fig. 8 shows the antibacterial effects of nanosized silica-silver on Escherichia coli, Bacillus subtilis and Pseudomonas synngae subsp. Syringae according to concentrations;

Fig. 9 shows a embodiment of a method of coating a fabric with a composition comprising nanosized silica- silver; and

Fig. 10a shows the antimicrobial activity of a fabric coated with nanosized silica-silver against Klebsiella pneumoniae, and Fig. 10b shows the antimicrobial activity of the fabric laundered once against K. pneumoniae.

Best Mode for Carrying Out the Invention

In one aspect, the present invention relates to an antimicrobial composition for coating fiber products comprising nanosized silica-silver particles in which nano silver is bound to silica molecules and a water-soluble polymer the nanosized silica silver particles prepared by irradiating a solution comprising a silver salt, silicate and the water soluble polymei with radiation rays

The term "nanosized silica silver", as used herein, refers to a composite m which nano sized silver particles and silica molecules are bound to a water-soluble polymer According to a detailed aspect, the nanosized silica silver may be prepared by irradiating a solution containing a silver salt, silicate and a water-soluble polymer with radiation rays A form of the composite is exemplified by a structure m which nano-sized silver particles, formed from silver ions, and silica molecules, formed from silicate, are individually or together surrounded by a water-soluble polymer by irradiation with radiation rays The nanosized silica-silver thus prepared is present in a form in which nanoparticles are dissociated from each other at a colloidal state or assembled into loose spherical aggregates (Fig Ib) The aggregates are disassembled into dispersed nanoparticles when temperature increases Nano- silvei particles m which nano-silver is coated with silica particles were conventionally developed However, these particles, unlike the nanosized silica silver particles contained in the antifungal coating composition of the present invention, do not include a water-soluble polymer in the particle composition Also, a water-soluble polymer was conventionally used to form nano-silver particles However, in this case, the water-soluble polymer was used not as a component of nano-silver particles but as a dispersing agent for forming a colloidal solution The nanosized silica silver contained in the antimicrobial composition of the present invention, as demonstrated from the absorption spectrum of Fig. 3, absorbs light at 403 nm, characteristic for nano silver, and as shown in Fig Ib has a uniform nanoparticle size The nanosized silica-silver has a particle size of preferably 0 5 to 30 nm, more preferably 1 to 20 nm, and most preferably 1 to B nm The nanosized silica silver is prepared by preparing a solution containing a silver salt, silicate and a water soluble polymer and irradiating the solution with radiation rays This method may further include bubbling (or purging) with inert gas before, after, or before and after irradiation with radiation rays The inert gas is exemplified by nitrogen and argon, and nitrogen gas is preferred The bubbling is preferably carried out for 10 mm to 30 mm In the method, the solution containing a silver salt, silicate and a water soluble polymer may further include a radical scavenger for scavenging radicals generated by irradiation with radiation rays The radical scavenger is exemplified by alcohols, glutathione, vitamin E, flavonoid and ascorbic acid Available alcohols may include methanol, ethanol, nor propanol, isopropanol (IPA) and butanol Of them, isopropanol is preferred The alcohol may be used xn an amount of 0 1 to 20%, and preferably 3 to 10% based on the total amount of the solution containing a silver salt, silicate and a water-soluble polymer The silver salt contained in the antimicrobial composition of the present invention may be exemplified by siver nitrate (AgNO₃) , silver perchlorate (AgClO₄) , silver chlorate (AgClθ₃) , silver chloride (AgCl) , silver iodide (AgI) , silver fluoride (AgF) , and silver acetate (CH₃COOAg) A highly water-soluble silver salt (e g , silver nitrate) is preferred The water-soluble polymer used m the preparation of nanosized silica-silver may be exemplified by polyvinylpyrrolidone (PVP) , polyvinyl alcohol (PVA) , polyacrylic acid and derivatives thereof, levan, pullulan, gellan, water-soluble cellulose, glucan, xanthan, water soluble starch, and corn starch Of them, polyvinylpyrrolidone (PVP) is preferred. The silicate used in the preparation of nanosized silica-silver may be exemplified by sodium silicate, potassium silicate, calcium silicate, and magnesium silicate Of them, sodium silicate is preferred The use of silicate for preparing nano-silver was not reported prior to the present invention The present inventors are the first to describe the use of silicate, not a silica form, in the reaction with a silver salt m order to provide nanosized silica-silver having excellent antibacterial effects, in which silica molecules and a water-soluble polymer are bound to nano-silver In the preparation of nanosized silica-silver, the silver salt and silicate are reacted in a weight ratio of 1 0 5 to 1.3 (silver salt- silicate) . Preferably, the reaction is carried out in a weight ratio of 1:1. The particle size of nanosized silica-silver may be controlled according to the amount of silicate The use of silicate m a small amount results m increased size of particles In contrast, when an excess amount of silicate compared to the silver salt is used, particles do not form. In the nanosized silica-silver preparation, the silver salt and water-soluble polymer are reacted m a weight ratio of 1:0.5 to 2.5 (silver salt, water soluble polymer) . Preferably, the reaction is carried out in a weight ratio of 1:1. For the preparation of nanosized silica-silver, radiation rays may be used, which include beta rays, gamma raya, X-rays, ultraviolet and electron rays A gamma ray dose of 10 to 30 kGy is preferred.

Generally, nano-sized particles are able to penetrate the plasma membrane, and silica is well taken up by fungi. The nanosized silica-silver is taken up by fungal cells, m which the nanosized silica-silver exhibits increased antimicrobial activity mediated by silver nanoparticles, and forms a physical barrier against pathogenic fungi due to the property of silica to increase resistance by inducing dynamic resistance to diseases, thereby preventing recurrence of diseases for a considerable period of time after pathogens are disinfected. The antimicrobial composition of the present invention may be used in the form of a colloidal solution in which the aforementioned nanosized silica-silver is dispersed/suspended m a solvent (e.g., water, alcohol, or combinations thereof, etc.) As used herein, the term "weight percentage (wt%) " is based on the total weight of a composition containing a solvent.

The nanosized silica-silver particles contained m the antimicrobial composition of the present invention have a particle size of 0.5 to 30 nm, preferably 1 to 20 nm, and more preferably 1 to 5 nm.

In addition to the nanosized silica silver, the antimicrobial composition of the present invention may further include a surfactant. The surfactant useful in the present invention may include nonionic, anionic, cationic and/or amphoteric forms. Also, any surfactants known to those skilled in the art are available Available nonionic surfactants may include polyoxyethylene-polyoxypropylene copolymers, sorbitan ester, polyoxyethylene sorbitan, polyethylene glycol and polyoxyethylene ether Available anionic surfactants may include alkyl sulfate, alkyl ether sulfate, alkaryl sulfonate, alkanoyl lsethionate, alkyl succinate, alkyl sulfosuccmate, N-alkyl sarcosmate, alkyl phosphate, alkyl ether phosphate, alkyl ether carboxylate and alpha olefin sulfonate. Available cationic surfactants may include 1,2-dioleoyl 3 trimethylammonium propane (DOTAP) , dimethyl dioctadecyl ammonium chloride (DDAC) , N- [1- (1,2-dioleoyloxy)propyl] -N,N,N-trimethylammonium chloride (DOTMA), l,2-dioleoyl-3-ethylphosphocholine (DOEPC), and 3β- [N- [(NjN'- dimethylamino) ethane] carbamoyl] cholesterol (DC-Choi) . Available amphoteric surfactants may include cocodimethylcarboxymethylbetaine, coca imidopropylbetaine, cocobetaine, laurylbetaine, laurylamidopropylbetaine, and oleylbetaine.

The present composition used in the coating of antimicrobial fiber products preferably includes a nonionic surfactant, and according to the intended use, may further include, in addition to the nonionic surfactant, other types of surfactants. Surfactants more suitable for use in the present composition include Tween 20, Tween 80, sorbitan monooleate and polyethylene glycol.

The present composition comprising a surfactant for use in the coating of antimicrobial fiber products may appear colorless or colored. For this use, a surfactant suitable for the colorless or colored appearance may be selected taking into consideration precipitation, turbidity and other factors. In a preferred aspect, sorbitan monooleate and polyethylene glycol may be used as surfactants.

The present composition for use in the coating of antimicrobial fiber products includes nanosized silica- silver and a surfactant in a weight ratio of 1:0.2 to 20 (nanosized silica-silver: surfactant), and more preferably 1 1 to 10 The surfactant may be contained m an amount of less than 30 wt%, preferably 0 1 to 20 wt%, and more preferably 0 5 to 10 wt%, based on the total weight of the composition The present composition for use m the coating of antimicrobial fiber products may further include an aromatic agent Any aromatic agents that are known m the art are suitable for use in the present invention The aromatic agents may be contained in an amount of less than 10 wt%, preferably 0 05 to 5 wt%, and more preferably 0 125 to 1 25 wt%, based on the total weight of the composition

The present composition for use m the coating of antimicrobial fiber products may further include an alcohol Alcohols suitable for use in the present invention preferably have a carbon number of 5 or less, and are more preferably ethanol, methanol and isopropanol The alcohol may be contained m an amount of less than 15 wt%, preferably 1 to 10 wt%, and more preferably 3 to 5 wt%, based on the total weight of the composition According to the intended use, the antimicrobial composition of the present invention may further include a deordorizing agent (e g , flavonoid, phytoncide, wood vinegar liquor plant extracts cyclodextπn, metal ions titanium dioxide) , and a precipitation inhibitor (e g , polyvmylalcohol (PVA) , pullulan, gellan, water-soluble cellulose, glucan, xanthan, water-soluble starch, levan) Also, the present composition may further include a widely known disinfecting agent, for example, antimicrobial plant extracts and an organic synthetic product

In another aspect, the present invention relates to antimicrobial fiber products coated with the antimicrobial composition

The antimicrobial fiber products of the present invention exhibited excellent antimicrobial effects In detailed practice, when the present composition comprising nanosized silica silver was applied to a cloth (fabric) m a concentration of 6 4 mg/yard, the viable cell number decreased to less than 10 cells before and after laundering, resulting m a reduction of 99 9% or greater in the viable cell number (Table ) The present composition displays long-lasting potent disinfecting effects on a wide spectrum of bacteria and fungi even in a small concentration while being little affected by the surrounding environment

The term "antimicrobial" as used herein, includes both growth inhibition of pathogenic microbes, including bacteria and fungi, and disinfection through survival inhibition

The nanosized silica-silver, contained in the present composition used xn antimicrobial coating, allows antimicrobial treatment against all pathogenic microbes in the surrounding environment Non-limiting examples of the pathogenic microbes may include fungi which are exemplified by Candida, Cryptococcus, Aspergillus, Trichophyton, Trichomonas, Chaetomium, Gliσcladium, Aureobasidium, Penicillium, Rhizopus, Cladosporium, Mucor, Pullulana, Tnchoderma, Fusaπum, Myrothecium and Memnoniella, and bacteria, which are exemplified by Escherichia, Bacillus, Pseudomonas, Chetonium, Staphylococcus, Klebsiella, Legionella, Salmonella, Vibrio and Rickettsia

The term "fibers", as used herein, includes all fiber materials, yarns and cloths Fiber materials constitute yarns yarns (filaments, threads, etc ) are the constituents of cloths Cloths include products made from yarns for example, woven fabrics, knitted fabrics, felts, plaited fabrics, braided fabrics, lace fabrics, non woven fabrics, laminated fabrics and molded fabrics In the present invention, the term "fibers" is mterchangably used with "fiber products" The fibers are classified according to their sources into natural fibers (e g , vegetable fibers, animal fibers, mineral fibers, pulp fibers, etc ), synthetic fibers (e g , regenerated fibers, semi synthetic fibers, complete synthetic fibers, etc ) , and inorganic fibers (e g , metal fibers, silicate fibers, ceramic fibers, etc ) Vegetable fibers include seed fibers, such as cotton and kapok, bast fibers, such as flax, ramie, true hemp, ^ute and kudzu fiber, leaf fibers, such as manila hemp, sisal hemp and New Zealand hemp, and fruit fibers, such as coconut fiber and coier Animal fibers include wool, animal hairs, cow hair, leather, fur and silks Mineral fibers include asbestos Regenerated fibers include those made from cellulose, such as viscose rayon, cuprammonium rayon, polynosic rayon, high-performance rayon and Tencel, and those made from proteins, such as casein fiber, arachin fiber, zein fiber and glycinm fiber Semi synthetic fibers include acetate fiber and triacetate fiber Natural rubber fiber, alginate fiber, chitosan fiber and chitm fiber are also included in the regenerated fibers Synthetic fibers include addition polymers, such as polyvinyl chloride, polyethylene, polypropylene, acrylic, polyurethane, polyvinyl alcohol and teflon fibers, and condensation polymers, such as polyester and nylon fibers Inorganic fibers include metal fibers, such as silver thread, aluminum thread, gold thread and stainless steel fiber, silicate fibers, such as glass fiber and rock fiber, and ceramic fibers, such as boron fiber Fiber products manufactured with these fibers, for example, clothing (e g , underwear, sportswear, night clothes, plain clothes, mountain-climbing clothes, et ) , bedclothes, shoe insoles, carpets, towels and curtains, are included in the scope of the present invention

The term "fibers" also includes paper The term "papermakmg fibers" includes all known cellulosic fibers or fiber mixes comprising cellulosic fibers Fibers useful m the present invention comprise any natural or synthetic cellulosic fibers including, but not limited to nonwoody fibers, such as cotton, abaca, kenaf, sabai grass, flax, esparto grass, straw, jute, hemp, bagasse, milkweed floss fibers, and pineapple leaf fibers, and woody fibers such as fibers obtained from deciduous and coniferous trees, including softwood fibers, such as northern and southern softwood kraft fibers, hardwood fibers, such as eucalyptus, maple, birch, aspen, or the like Fiber products manufactured with such fibers, for examples, wallpaper, paper towels (wipes) , clothing, shoes and shoe insoles, carpets, furniture fabrics, bedclothes, bags, automobile fabrics and carpets, mats and other floor rugs, hats, dish towels, toilet bowl sheets and rugs, are included in the scope of the present invention In particular, disposable paper towels impregnated with the present composition are capable of simply cleaning surfaces for antimicrobial treatment of the surfaces, and are thus convenient and easy to use in the daily life

In another aspect, the present invention relates to a method of antimicrobially treating a fiber product comprising coating the fiber product with a composition, that comprises nanosized silica-silver particles in which nano-silver is bound to silica molecules and a water soluble polymer, the nanosized silica-silver particles prepared by irradiating a solution comprising a silver salt, silicate and the water-soluble polymer with radiation rays

The antimicrobial fiber product according to the present invention may be coasted using a coating method widely known m the art, which may be suitably selected according to coated materials Examples of coating methods include brushing, padding, spray (e g heat-spray, airless spray, etc ) coatxng, electrocoatmg, roller coating, curtain flow coating, flow coating, dip coating, tumbling, blade coating, spatula coating, spin coating and die coating After being coated with the composition comprising nanosized silica silver by the coating method, the fiber product may be further subjected to heat treatment The heat treatment may be conducted using, for example, lamps emitting ultraviolet rays, infrared rays, or the like, hot wires, hot wind and irons at 80 to 200 C m order to induce absorption of the nanosized silica silver containing composition by the fiber The fiber coating with the composition comprising nanosized silica-silver particles may be conducted by coating the whole of a material to be coated or a ma]or part thereof in order to allow a coating material to be contained in the material to be coated and thus give antimicrobial properties The nanosized silica silver, coated onto an antimicrobial fiber according to the present invention, may be applied to the fiber m an amount of about 0 01 to 100 mg/yard, and preferably 0 5 to 50 mg/yard In detail, when the coating is achieved by impregnation, the nanosized silica-silver may be applied in an amount of about 0 01 to 100 mg/yard, and preferably 0 5 to 50 mg/yard In the case of spray coating, the nano-silca silver may be applied in an amount of about 0 01 to 100 mg/yard, and preferably 0 5 to 50 mg/yard

In a detailed aspect, in addition to the nanosized silica silver, the coating composition used in the antimicrobial treatment method according to the present invention, may further include an aromatic, a surfactant and a stabilizer Also, the composition may include, in addition to the aromatic, surfactant and stabilizer, a humectant, a dispersing agent, a stabilizer, an inactivating agent, an adhesion enhancer, a permeating agent, and an antifoammg agent For example, in a coating method based on applying of a spray form of concentrates or wet powders, the coating composition comprising nanosized silica-silver may further include a hemectant and a dispersing agent

The coating composition comprising nanosized silica- sliver may be m an aqueous or solid phase When present m a solid phase, the coating composition may be used after being dissolved or suspended m a proper solvent (e g , water)

A better understanding of the present invention may be obtained through the following examples which are set forth to illustrate, but are not to be construed as the limit of the present invention

EXAMPLE 1 Preparation of nanosized silica-silver bound to silica molecules and water-soluble polymer 1 g of sodxum silicate (Na₂SiOJ, 1 g of silver nitrate (AgNO₃) , 1 g of polyvinylpyrrolidone (PVP) and 12 ml of isopropylalcohol (IPA) were dissolved in distilled water at a total volume of 200 ml Nitrogen gas was injected into the resulting solution for 20 min After bubbling, the solution was irradiated with gamma rays of 25 kGy, thereby preparing nanosized silica silver

Fig Ia is a flowchart of a method of preparing nanosized silica-silver bound to silica molecules and a water-soluble polymer according to one embodiment of the present invention After irradiation with gamma rays, the solution appeared yellow, characteristic for nano-silver particles This result indicates the formation of stable nano-sized silica silver particles through linkage of silica molecules, the water-soluble polymer and silver particles by the above reactions

The particles formed by the above reactions were examined to determine if they were nano-silver particles Test samples were prepared according to the compositions described m Table 1, below, and were allowed to stand for 24 hrs at room temperature Thereafter, test samples were examined for color change

TABLE 1

Solution prepared in this example

Test samples A and B were the prepared solutions irradxated with radiation rays, and test samples C and D were the prepared solutions containing Ag⁺ ions but not irradiated with radiation rays Test samples SW and DW were used as controls, not containing silver ions or silver particles

Silver is easily oxidized in an ionic state. In the presence of Cl ions, silver ions are precipitated as a brown precipitate, AgCl, wherein they turn brown. Based on this fact, the state of silver was investigated using tap water containing Cl ions. Silver forms precipitates in an ionic state (Ag⁺) , and appears yellow when present as stable nano-silver particles. The results are given m Table 2, below.

TABLE 2

As shown in Table 2, test samples SW, D and DW were colorless with no change m color after incubation for 24 hrs, indicating that silver ions, chloride ions, or neither silver ions nor chloride ions were m existence In contrast test sample C changed from colorless to reddish brown This is because silver ions bonded to chloride ions contained m tap water to form a precipitate of AgCl Test samples A and B appeared yellow with no change in color, indicating that the irradiation with radiation rays formed stable nano-silver particles bound to silica molecules and a water soluble polymer, with no formation of AgCl precipitates even in the presence of chloride ions The color changes are also photographically shown m Fig 2 Fig 3 shows the absorption spectrum of the nanosized silica-silver of the present invention, prepared as described above The absorption spectrum of the nanosized silica-silver was compared with absorption spectra of test samples DW, B and D, described in Table 2 Only test sample B absorbed light at 403 nm, characteristic for nano silver Test samples DW and D did not absorb light at the same wavelength

As revealed from the results obtained after incubation for 24 hrs and the absorption spectra, the irradiation of a solution containing sodium silicate, silver nitrate and PVP with radiation rays forms stable nanosized silica silver bound to silica molecules and a water soluble polymer

Fig Ib shows TEM (Transmission Electron Microscope) images of the nanosized silica-silver prepared as described above As shown in Fig Ib, nanosized silica-silver particles have a uniform particle size distribution with a particle size less than 20 nm, specially, ranging from 1 nm to 5 nm. The nanosized silica-silver particles are dissociated from each other or assemble into loose spherical aggregates by intermolecular attractive forces. The aggregates are easily disassembled by heating.

EXAMPLE 2: Preparation of nanosized silica-silver bound to silica molecules and water-soluble polymer

Nanosized silica-silver was prepared according to the same method as in Example 1, except that sodium silicate (Na₂SiO₃) was used in varying amounts of 0.5 to 2 g. Various test samples, described in Table 3, below, were prepared with varying amounts of sodium silicate and examined.

TABLE 3

Fig. 4 shows the changes in absorbance and color of nanosized silica-silver according to varying concentrations of sodium silicate, described in Table 3.

As shown in Fig. 4, the highest absorbance was observed in a sodium silicate to silver nitrate ratio of 1:1. The absorbance decreased when sodium silicate was used m a 1 5-fold hxgher amount than silver nitrate Also, when sodium silicate was used m a 0 5-fold lower amount than silver nitrate, orange gold color was observed, indicating that silver particles increased in size The above results indicate that the added amount of sodium silicate is an important factor upon preparation of nanosized silica-silver, and that the particle size of nanosized silica-silver can be controlled by varying the amount of sodium silicate

EXAMPLE 3 Preparation of nanosized silica-silver bound to silica molecules and water-soluble polymer

Nanosized silica-silver was prepared according to the same method as in Example 1, except that polyvinylpyrrolidone (PVP) was used m varying amounts of 0 5 to 2 g

The changes in absorbance and color of nanosized silica-silver according to varying concentrations of polyvinylpyrrolidone (PVP) are given in Table 4, below, and Fig 5

TABLE 4

As shown in Table 4 and Fig. 5, when sodium silicate was used in an equal ratio to silver nitrate, polyvinylpyrrolidone (PVP) can be used in a concentration

0.5 to 2-fold higher than sodium silicate (or silver nitrate) .

EXAMPLE 4 : Preparation of nanosized silica-silver bound to silica molecules and water-soluble polymer

Nanosized silica-silver was prepared according to the same method as in Example 1, except that high levan or corn starch was used instead of polyvinylpyrrolidone (PVP) .

The absorbance and absorption spectra of the prepared nanosized silica-silver are given in Table 5, below, and Figs. 6a and 6b.

TABLE 5

Test samples Ab. at 403 nm

High levan 0. 208

Corn starch 0. 211

As shown in Table 5 and Figs. 6a and 6b, polysaccharides such as levan or corn starch are available for preparation of nanosized silica-silver although the use of levan or corn starch resulted in decreased absorbance at

403 nm.

EXAMPLE 5: Preparation of nanosized silica-silver bound to silica molecules and water-soluble polymer Nanosxzed silica-silver was prepared according to the same method as in Example 1, except that varying radiation doses were used

The absorbance and absorption spectra of the prepared nanosized silica silver are given in Table 6, below, and Fig 7

TABLE 6

As shown in Table 6 and Fig 7, the absorbance at 403 nm occurred even m a gamma-ray dose of 10 kGy, and increased with increasing gamma-ray doses These results indicate that nanosized silica silver can be prepared using a radiation dose higher than 10 kGy.

TEST EXAMPLE 1: Antifungal activity of nanosized silica- silver against pathogenic fungi

Minimal inhibitory concentrations (MICs) of nanosized silica-silver, tolnaftate, amphotericin B and itraconazole against various human pathogenic fungi were measured The pathogenic fungi included Candida lusitaniae, Candida tropicalis, Candida albicans, Candida krusei, Candida glabrata, Candida parapsilosis, Cryptococcus neoformans, Mucor ramosissmus, Aspergillus fumigatus, Aspergillus flavus, and Aspergillus terreus The MICs were measured using a standard procedure proposed by the AFST-EUCAΞT (Anitifungal Susceptibility Testing Subcommittee of the European Committee on Antibiotic Susceptibility Testing; Rodriguez-Tudela et al. , (2003) Method for the determination of minimum inhibitory concentration by broth dilution of fermentative yeasts, Clinical Microbiology and Infection, 9, I-VIII) . This standard is based on the reference procedure of the National Committee for Clinical Laboratory Standards (NCCLS) , which is described in the literature (National Committee for Clinical Laboratory Standards (2002) Reference Method for Broth Dilution Antifungal Susceptibility Testing of Yeast-Second Edition: Approved Standard M27-A2 NCCLS, Wayne, PA, USA) .

In detail, of the pathogenic fungi, Candida species, Cryptococcus neoformans and Mucor ramosissmus were cultured using SDA (Sabouraud Dextrose Agar) medium at 35^°C for 24 hrs for Candida species and for 48 hrs for C. neoformans and M. ramosissmus About five colonies of less than 1 mm were picked, suspended in 5 ml of 0.85% saline (8 5 g/L NaCl), and adjusted to a final density of 2X10³ cells/ml with RPMI 1640 medium to give an inoculum. Also, Aspergillus species were sufficiently cultured at 35^°C for 7 days using PDA (Potato Dextrose Agar) medium. After 5 ml of sterile distilled water and one drop of Tween 20 were poured onto the PDA plate, spores were scratched with a sterile micropipette tip and placed into a test tube After the test tube was allowed to stand for 3 to 5 nun, the supernatant was recovered and adjusted to a density of 2XlO⁴ CFU/ml to give an inoculum Of the nanosized silica- silver prepared in the above Examples and demonstrated to have antifungal activity, the nanosized silica silver prepared in Example 1 was used in this test and was two fold serially diluted with RPMI 1640 medium Also, as controls, tolnaftate, amphotericin B and itraconazole were dissolved in DMSO (dimethyl sulfoxide) and two-fold serially diluted with RPMI 1640 medium The final concentration of DMSO was 2 5% 100 βH of each dilution and 100 fύ of each inoculum were aliquotted into 96-well plates, thereby giving a final concentration of 128 ng/rwi to 0 0313 ig/iii-P for antifungal agents contained m the two-fold serial dilutions 96 well plates seeded with Candida species and Aspergilles fumigatus were incubated at 35 C for 48 hrs Cryptococcus neoformans and Mucor ramosissmus were cultured at 35 C for 72 hrs After cultivation, the culture was observed with the naked eye, and the lowest concentration inhibiting visible fungal growth was considered a minimum growth inhibitory concentration (MIC l≥/ig/urf) The results are given m Table 7, below

TABLE 7

(Unit: ug/ml)

As shown in Table 7, the nanosized silica-silver exhibited antifungal activity against pathogenic fungi, Candida, Cryptococcus, Mucor and Aspergillus.

TEST EXAMPLE 2: Antibacterial activity of nanosized silica- silver according to concentrations

Nanosized silica-silver bound to silica molecules and a water-soluble polymer was examined for growth inhibitory effects versus bacteria, Escherichia coli, Bacillus subtilis KCTC 1021, and Pseudomonas syringae subsp. syringae KCTC 2440, according to concentrations. Bacteria were incubated in 500-ml Erlenmeyer flasks containing 100 ml LB medium under aerobic conditions with shaking at 190 rpm for 15 to 16 hrs at 37 C for Escherichia coli and at 30^°C for other bacteria Thereafter, 20 uJl of each culture was inoculated onto LB agar plates containing nano-silver bound to silica molecules and a water-soluble polymer in concentrations of 0, 1, 10, 100 and 1000 pptn Incubation was conducted for 6 to 7 days at 37^°C for E coli and at 30^°C for other bacteria

Fig 8 shows the growth inhibitory effects of nanosized silica-silver versus Escherichia coli, Bacillus subtilis 1021 and Pseudσmoπas syπngae subsp Synngae 2440

The gram positive bacterium, Bacillus subtilis, exhibited decreased growth at 100 ppm of nanosized silica- sliver compared to a control (LB agar plate) The gram- negative bacteria, Escherichia coli (Probe, PR2) and Pseudomonas synngae, showed similar growth rates at 10 ppm of nanosized silica-silver to those of controls (LB agar plates) , and their growth was completely inhibited at 100 ppm of nanosized silica silver

TEST EXAMPLE 3 Antimicrobial activity of nanosized silica- silver against indoor microorganisms

In order to determine whether nanosized silica-silver has antimicrobial effects versus indoor microorganisms according to concentrations, the nanosized silica-silver was examined for growth inhibitory effects versus an indoor fungus, Cha.etortu.um globosum KCTC 6988, in concentrations of 0 3, 3, 10 and 100 ppm

In detail, MSA (mineral salt agar) plates, containing nanosized silica silver at 0 3, 3, 10 and 100 ppm, were inoculated with the indoor fungi, Chaetomium globosum KCTC 6988, with a disk cut with a 6-mm-diameter cork borer, followed by incubation m an incubator for 7 days at 25 G On Day 7, the cultures were compared with a culture not containing nanosized silica-silver m order to determine whether the nanosized silica-silver has an antimicrobial effect on C globosum

Chaetomium globosum was found not to grow even at 0 3 ppm of nanosized silica-silver These results indicate that the nanosized silica-silver has excellent antimicrobial effects even m small concentrations

TEST EXAMPLE 4 Antimicrobial activity of nanosized silica silver on fabrics

This test was carried out according to a test method for antimicrobial activity of fabrics, (K0693) -2001, provided by Korean FITI Testing & Research Institute

Staphylococcus aureus strain 209 (American Type

Culture Collection No 6538) and Klebsiella pneumoniae

(American Type Culture Collection No 4352) were streaked onto nutrient agar plates (prepared by dissolving 5 g of peptone and 3 g of beef extract m 1000 ml by heating, adjusting the resulting medium to pH 6 8+0.2 with 0 1 ml/L of sodium hydroxide and adding 15 g of agarose to the nutrient medium) , and were cultured for 24 to 48 hrs at 37+l°C The two known bacteria, cultured as described above, were inoculated in 100-ml Erlenmeyer flasks containing 20 ml of a nutrient medium (prepared by dissolving 5 g of peptone and 3 g of beef extract in 1000 ml by heating and adjusting the resulting medium to pH 6 8±0.2 with 0.1 ml/L of sodium hydroxide) , and were cultured for 24 to 48 hrs at 37±1^°C with agitation Thereafter, absorbance was measured using a spectrophotometer to determine cell density Each culture was then adjusted to a density of l±O.3xlO⁵ cells/ml with the 20-fold diluted nutrient medium precooled to 0^°C, and was used as an inoculum m the next step

A fabric specimen was prepared by a method illustrated m Fig. 9 A polyester fabric Ia (control specimen) to be coated with nanosized silica-silver was allowed to pass a staining bath 2, a roller 3 and a dryer 4 to produce a test specimen Ib In the staining bath 2, the fabric Ia was allowed to absorb about 100 ml/yard (about 6.4 mg/yard) of the nanosized silica silver (hereinafter, referred to as "NSA" ) prepared according to the method as m Example 1 or a 2-fold dilution (hereinafter, referred to as "NSB") of the nanosized silica-silver with a levan solution In order to remove water absorbed along with the nanosized silica-silver, the fabric was compressed using the roller 3, thus removing a part of water, and was dried xn the dryer 4 at 140^°C for 15 mxn to completely remove water

The control specxmen and the test specimen, prepared by the above method, were placed into about 30 ml sterile glass containers each having a screw-type cap Exactly 0 2 ml of the inoculum prepared above was inoculated m the containers while evenly placed on the control and test specimens The inoculated control and test specimens were incubated at 37±1^°C for 18 hrs

Immediately after inoculation and 18 hrs later, 20 ml of an neutralization solution precooled to 0^°C (prepared by dissolving 5 g of sodium chloride and 2 g of a nonionic surfactant in 1000 ml of distilled water, aliquotting the solution in 20 ml into 100-ml Erlenmeyer flasks, and autoclavmg the flasks in a high-pressure sterilizer under steam pressure of 1055 g/cm³ at 120±2^°C for 20 mm) was added to the glass containers containing the inoculated control and test specimens The flasks were vigorously shaken to release bacterial cells from the fabric specimens into the neutralization solution The neutralization solution was then serially diluted m physiological saline by 10°, 10¹, 10², 10³ and 10⁴ times Exactly 1 ml of each dilution was collected, placed onto a petri dish, evenly mixed with 15 ml of nutrient agar medium at 45 to 46^°C, and incubated at 37 C for 24 to 48 hrs Thereafter, the viable cell number was calculated according to the following Equation 1 (there are two significant figures) .

[Equation 1] M = Z x r x 20

(M viable cell number Z colony number, r dilution time, 20 the amount of physiological saline used for release of bacterial cells)

On the other hand, m order to determine whether a fabric coated with nanosized silica-silver retained antimicrobial effects after laundering, the above fabric was laundered using an agitator-type automatic washing machine, and the viable cell number was measured. Laundering was carried out as follows. The agitator-type automatic washing machine was set to a cleaning cycle of 2 mm, and filled with water of 40±3"C to high level. The control and test specimens were placed into the washing machine along with a fabric for weight calibration, prescribed by the KS K 0465 method, to give a total weight of 0.9 kg. After 90 g of a commercial laundry detergent powder (Trade name: One-Scoop, LG Household & Health Care Co , Ltd.) was added to the washing machine, the washing machine was allowed to run. Rinsing was carried out using water of 30±3^°C The fabric specimens were then horizontally placed on a mosquito net and allowed to air- dry for 1 day. After washing and drying, the control and test specimens were inoculated with the inoculum prepared above, and the viable cell number was measured by a viable cell counting method.

A reduction of viable cells in the fabric as treated above was determined according to Equation 2, below, and the results are given in Table 8, below.

In addition, Fig. 10a shows the antimicrobial activity of the control specimen and the test specimen treated with nanosized silica-silver (NSA) against Klebsiella pneumoniae. Fig. 10b shows the antimicrobial activity of the control specimen and the test specimen treated with nanosized silica-silver (NSA) after being laundered once against K. pneumoniae.

[Equation 2]

Percentage reduction = [ (M_a-M_b) /M₃] ^x 100

(M_a- the number of viable cells in control specimen after incubation for 18 hrs,- M_b: the number of viable cells in test specimen after incubation for 18 hrs)

TABLE 8

In Table 8, the control specimen is a known fabric not having undergone antimicrobial treatment, which is employed in a test method for antimicrobial activity of fabrics provided by the Korean FITI Testing & Research Institute.

As shown in Table 8, the nanosized silica-silver, prepared according to the method described in Example 1, exhibited a reduction of 99.9% in viable cells both before and after the coated fabric specimen was laundered.

In order to determine whether a fabric coated with nanosized silica-silver retains the antimicrobial activity provided by the nanosized silica-silver after laundering twenty times, the above laundry cycle was repeated twenty times. Viable cells for the same bacteria were counted, and the percentage reduction of viable cells was calculated according to Equation 2, above. The results are given in Table 9, below.

TABLE 9

In Table 9 the control specimen is a known fabric not having undergone antimicrobial treatment, which is employed in a test method for antimicrobial activity of fabrics provided by the Korean FITI Testing & Research Institute

As shown in Table 9, the nanosized silica-silver, prepared according to the method described in Example 1, exhibited a reduction of 99 9% in viable cells both before and after the coated fabric specimen was laundered twenty times

These results indicate that the nanosized silica- silver imparts excellent antimicrobial activity to its processed products for a long period of time, even after repeated laundering

TEST EXAMPLE 5 Evaluation of fungal resistance of fibers coated with composition comprising nanosized silica silver particles according to times

The nanosized silica-silver was evaluated for antifungal activity, as follows Fabrics contaminated with Aspergillus niger ATCC 9642, PeniciIlium pmophilum ATCC 11797 Chaetomxum globosum ATCC 6205, Gliocladium virens ATCC 9645 and Aureobasidium pullulans ATCC 15233 were coated with the composition comprising 64 ppm of the nanosized silica silver particles prepared in Example 1 according to the method described in Test Example 4 and illustrated m Fig 9 After 1, 2, 3, and 4 weeks the viability of the above fungi was assessed according to the ASTM G-21 method provided by the Korean Testing and Research Institute for Chemical Industry

In the antifungal fabrics coated with the composition comprising nano silica particles, all fungi lost their viability by the antimicrobial activity of nanosized silica-silver Even after 1 to 4 weeks, no viable cells were detectable

TEST EXAMPLE 6 Antifungal activity of nanosized silica- silver according to surfactant addition

The nanosized silica-silver solution prepared m Example 1 was supplemented with a surfactant and was evaluated for antifungal activity The nanosized silica- silver prepared in Example 1 was supplemented with a surfactant, PEG 400 (Polyethylene glycol, CELL CHEMICAL) or

CELNON-80TW(Sorbitan monoolate, CELL CHEMICAL) The surfactant-containing nanosized silica silver solutions

(PEG 400 and CELNON-80TW samples) , a positive control and a negative control were inoculated with Aspergillus niger

KCTC 6960, diluted with 0 05% Tween 20 to a density of

3 25xlO⁴ spores/ml, m a ratio of 9 1 After the inoculated samples were allowed to stand for 60 mm, 200 μg of each sample was smeared onto PDA and MEA plates After cultxvatxon, the nanosized silica-silver supplemented with a surfactant was assessed for antxfungal actxvity The results are given in Table 10, below

TABLE 10

As shown xn Table 12 except for the negative control, the nanosized silica-silver solutions supplemented with surfactants were found to have the same antifungal effects as m the nanosized silica silver solution not containing a surfactant

TEST EXAMPLE 7 Color intensity and clarity of nanosized silica-silver-containmg solutions according to mixing ratios of nanosized silica-silver and surfactant

In order to investxgate the color intensity and clarity of a nanosized silica-silver-containmg solution according to mixing ratios of nanosized silica silver and a surfactant, nanosized silica silver (NSS) and a surfactant,

CELNON 80TW, were mixed in various ratios and then mixed with water, enough to give a total volume of 100 ml The resulting solutions and a control were examined for color intensity and clarity The results are given in Table 11, below.

TABLE 11

^a (no precipitation) 0 3 (formation of precipitates greater than

5 mm in diameter) ^b (not turbid) 0 > > > ■ > > 3 (completely turbid) ^c (colorless (white)) 0 m>'i 5 (no color change, color appears when

NSS is added to distilled water) ^α changed to grayish brown when NSS is precipated m

As shown in Table 11, no precipitation was observed m S-I to S-Il samples, and these samples were not turbid. In contrast, S-12 to S-15 samples were colorless immediately after being prepared, and after 3 days, became turbid and changed color when precipitates were formed m these samples The precipitation and color changes decreased with increasing content of CELNON-80TW Samples containing CELNON-80TW in 2 to 5 fold higher amounts than nanosized silica silver were colorless. Industrial Applicability

As described hereinbefore, fiber products coated with a composition comprising nanosized silica-silver particles, m which nano-silver is bound to silica molecules and a water soluble polymer, the nanosized silica-silver particles prepared by irradiating a solution comprising a silver salt, silicate and the water-soluble polymer with radiation rays, retain excellent antimicrobial activity before and after laundering. Thus, the nanosized silica- silver has a wide spectrum of applications in the fiber industry

Claims

1 An antimicrobial composition fox coating a fiber product comprising nanosized silica-silver particles 0 5 to 30 nm in size, in which nano silver is bound to silica molecules and a water soluble polymer, the nanosized silica-silver particles prepared by irradiating a solution comprising a silver salt, silicate and the water soluble polymer with radiation rays

2 The composition as set forth in claim 1, further comprising a surfactant

3 An antimicrobial fiber product coated with a composition comprising nanosized silica-silver particles 0 5 to 30 nm m size in which nano-silver is bound to silica molecules and a water soluble polymer, the nanosized silica-silver particles prepared by irradiating a solution comprising a silver salt, silicate and the water soluble polymer with radiation rays

4 The antimicrobial fiber product as set forth in claim 3, which is coated with 0 01 to 100 mg/yard of the nanosized silica-silver particles

5 The antimicrobial fiber product as set forth m claim 3, wherein the fiber is a synthetic fiber 6 The antimicrobial fiber product as set forth m claim 3, which is selected from among clothing, ornaments, bedclothes, shoe insoles, carpets, towels and wallpaper

7 A method of antimicrobially treating a fiber product, comprising coating the fiber product with a composition comprising nanosized silica-silver particles 0 5 to 30 nm in size, m which nano-silver is bound to silica molecules and a water-soluble polymer, the nanosized silica-silver particles prepared by irradiating a solution comprising a silver salt, silicate and the water-soluble polymer with radiation rays

8 The method as set forth in claim 7, wherein the composition further comprises a surfactant

9 The method as set forth in claim 7, wherein the coating is carried out by applying, dipping or blending

10 The method as set forth in claim 9, further comprising heating after coating by applying, dipping or blending

11 The method as set forth m claim 9, wherein the applying is carried out by spraying