BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a novel antimicrobial inorganic composition and articles coated with the inorganic composition, and an organic antimicrobial composition, and a process of making such articles. More specifically, it relates to a composition comprising low temperature far infrared irradiating metals supported on a porous honeycomb shaped substrate, and an organic quaternary ammonium salt bonded on a porous honeycomb-shaped substrate.
2. Prior Art
Antimicrobial metals have been known to be incorporated into paints and fibers for industrial or home applications. Organic quaternary ammonium silane has been shown to have anti-algae properties. The following patents show the use of silver, copper, and zinc in antimicrobial substances, and the use of organosilicon compounds.
U.S. Pat. No. 3,865,728 discloses an organosilicon compound coated on a fibrous substrate and then heated to 65-100 degrees C. The resulting product is used for control of algae in aquarium tanks.
U.S. Pat. No. 5,147,686 discloses an antimicrobial powder made by coating a titanium oxide substrate with antimicrobial metals including copper, zinc or alloys of Cu—Zn, Cu—Ag, Cu—Al, Cu—Sn or the combination of these metals. The composition is useful against various microorganisms such as E. Coli, Salmonella typhimurium, and others. The coated substrate is fired at 400 degrees C. The powder form of this product is intended to be incorporated into a resin.
U.S. Pat. No. 5,151,122 relates to an antibacterial ceramic material. Various ceramics such as zeolite or alumina or clay are described as being fired at temperatures as high as 1200-1300 degrees C so as to lock in the absorbed antibacterial metals such as silver, copper, or zinc. The patent further suggests that the product can be added to a resin which can be molded into any shape.
U.S. Pat. No. 5,415,775 relates to an ultrafiltration membrane consisting of alumina and titanium dioxide which has been sintered at 1000-1500 degrees C and then coated with metal oxide. The membrane exhibits anti-bacterial properties.
U.S. Pat. Nos. 5,618,762, 5503,840, and 5,595,750 variously show Ag, Cu, Zn. Pt, Cd, Cr as antibacterial components including protective coatings.
None of the above patents shows an antimicrobial composition as disclosed herein. Furthermore, none of the above patents addresses the problem of keeping streams, water reservoirs, public baths, and fish farms clear of harmful micro-organisms including algae or bacteria. In addition to their antimicrobial properties, the articles of the present invention show high efficacy due to the honeycomb structure of the substrate which provides multitude of antimicrobial sites per unit volume and prolonged antimicrobial efficacy in flowing air or water due to strong adhesion of the antimicrobial component on the substrate, without any adverse environmental effects such as are encountered when chemical pesticides, bactericides or herbicides are used.
The object of this invention is to provide antimicrobial articles having coated thereon a novel metal composition or an organic quaternary ammonium salt according to a specific process to eliminate harmful microbes such as E. coli, Salmonella typhimurium, and Saccharomycetes such as Saccharomyces cerevisiae, Candida albicans; Algae groups, such as Blue Green Algae, Brown Algae, and Green Algae, and Bacteria such as Chaetomium globosum, Penicillium funiculosum including Legionella pneumophila. Another object is to provide inexpensive articles having the shape of porous honeycombs treated with the antimicrobial substances of this invention. Such articles can be placed in nets or cages in streams, rivers or stationary bodies of water to eliminate harmful microbes. Still another object is to provide methods to prolong the life of such articles, thereby increasing and prolonging antimicrobial effectiveness. These objects of the invention will become apparent from the following description.
SUMMARY OF THE INVENTION
The articles of this invention are porous honeycomb-shaped substrates having coated theron inorganic or organic antimicrobial components. The inorganic component is selected from the Low Temperature Irradiating Far Infrared Material, herein referred to as metal composition. Said metal composition comprises metals capable of emitting far infrared radiation having a wavelength of from 3 to 30 microns below 60° C., which eliminates microbes. The metal composition has the general formula: AB2 O4 of a regular spinel structure. It is to be noted that A and B are not chemical symbols. A is magnesium, divalent iron, nickel, manganese, cobalt or zinc. B is aluminum, trivalent iron, trivalent manganese, or trivalent chromium. O is oxygen. The composition may contain one or more of the following compounds: ferric oxide, ferric sulfide, zinc oxide, calcium oxide, titanium oxide, cupric oxide, aluminum oxide, aluminum sulfide, strontium oxide, and tantalum oxide as impurities.
The organic antimicrobial component is a quaternary ammonium salt having the formula:
wherein m+n is 16 to 19, m is 1 to 6, and n is 13 to 17; or m+n is 20 to 23, m is 4 to 11 and n is 9 to 17; X is halogen; and Y is a hydrolyzable radical or hydroxy group.
The porous substrate of the antimicrobial article in accordance with this invention is sodium silicate, or diatomaceous earth or a ceramic material or siliceous clay or material comparable to silicon dioxide or aluminum oxide, which has been made into a honeycomb structure either by molding or extruding. The substrate is impregnated with either one of the above antimicrobial substances and calcined at a predetermined temperature.
DETAILED DESCRIPTION OF THE INVENTION
The Inorganic Antimicrobial Article
The substrate of the antimicrobial article is made of siliceous clay, ceramic or Boehmite powder mixed with water to form a slurry and extruded into a honeycomb-shaped preformed substrate having high porosity.(herein referred to as preformed substrate). This preformed substrate has about 400 cells per square inch, providing a large surface area for the deposition of antimicrobial material. An alternative substrate may be made from a polymer material having the honeycomb shape and coated with the substrate material.
In fabricating the antimicrobial inorganic article using the metal composition as the antimicrobial component, the metal composition is blended with an appropriate bonding agent to form a soaking slurry or solution. A preformed substrate is impregnated with the soaking slurry.
The metal composition can be MgFe2O4. Zn Fe2O4., FeCr2O4. MnFe2 O4.or any combination of metals selected from the A and B groups.
The bonding agent to be mixed with the metal composition can be an alkali metal silicate, such as sodium silicate. The metal composition should be 10-75%, preferably 25-50% by weight of the mixture.
Alternatively, the metal composition of this invention may be blended with the powder substrate directly, without soaking, and then molded into a honeycomb-shape, and calcined. The metal composition should be 10-85% of the total weight of the mixture, preferably 25-75%. The impregnating process is preferred to the blending process.
The impregnated substrate is calcined at a temperature of 700-1100° C., preferably 800-1000° C. The calcining time is not critical; it can be based upon the size the articles.
The Organic Antimicrobial Article
Quaternary ammonium organosiloxane salt (herein referred to as quaternary ammonium salt) used as algaecide by coating on a fibrous material as shown in U.S. Pat. Nos. 3,817,452 and 3,865,728 forms no part of this invention. Rather, this invention provides a new method of preparing an antimicrobial article. Moreover, the article kills not only algae but also bacteria. The relevant portions of the above patents are incorporated herewith by reference.
In the process of this invention, the quaternary ammonium salt is dissolved in water to form a moiety of —Si(OH)3 and the preformed substrate is soaked in the solution. The moiety of the quaternary ammonium salt reacts with the SiO2 of the substrate thereby forming a strong bond. 3-(Trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride is representative of the group of silyl quaternary ammonium salts that may be used in the instant application.
It has been found that in the process of making the organic antimicrobial article of this invention, a special calcining aid can be used to enhance the adhesion or bonding of the quarternary ammonium salt to the preformed substrate. The calcining aid is aluminum oxide with high pore surface per unit volume, such as Boehmite, which is available from Condea Corporation in Germany. Other calcining aids can be SiO2 or SiO2.Al2 O3.
In the preparation of the organic antimicrobial article, aluminum oxide is mixed with water in the ratio of 1:1 to 1:10 by weight. An acid such as nitric, hydrochloric, or oxalic acid is added to adjust the pH to 3-6. After the mixture is ground to a gelatinous solution, the porous preformed substrate (as first described in connection with the inorganic antimicrobial article ) is dipped into the gelatinous solution. This calcining-aid-coated preformed substrate is then calcined at 400 to 1500° C., preferably at 500 to 800° C.
Quaternary ammonium salt is dissolved in a solvent selected from the group consisting of water, alcohols, ketones, esters, hydrocarbons and chlorinated hydrocarbons in a concentration of about 0.05 to 20%, preferably 0.3 to 0.6% by weight. Water is the preferred solvent. The calcined substrate as prepared from above is impregnated with the quaternary ammonium salt solution until saturated or 50% of the solution is absorbed. The impregnated substrate is then dried at 50 to 200° C., preferably at 60 to 150° C. to form the organic antimicrobial article. Drying time depends on the size of the substrate.
The antimicrobial articles of this invention may be placed in water to kill microbes in, for example, cooling water. They may be placed in circulating air in air conditioning system to sterilize the air. After a period of use, the articles may be regenerated by flushing with clean water or vibrated with a ultrasonic device to remove any accumulated debris.
The following examples illustrate the preparation of the antimicrobial articles of this invention and their efficacy.