Invented by Subramaniam Sabesan, EIDP Inc
The EIDP Inc invention works as followsProvided is a material with a solid-surface antimicrobial agent, in a thermoplastic or thermoset resin matrix. The antimicrobial component comprises a metal-chitosan complex.
Background for Antimicrobial Solid Surface Materials containing Chitosan-Metal Complexes
Artificial or Synthetic Marble” is a generic term for a variety of building materials, including bathroom vanity tops (sinks), shower stalls, kitchen counters and other decorative surfaces. The material is suitable for furniture, linings, and stationary small items. Artificial marble is easy to keep clean and tidy. It is increasingly used in hospitals and nursing homes as well as commercial and residential food prep facilities.
As evidenced by the numerous materials on the market, it is clear that there is a demand for products and/or methods which minimize or eliminate harmful microorganisms found in the environment. These materials can be used in food preparation, service, or handling. These materials are also useful for areas that require personal hygiene such as bathrooms. Such antimicrobial materials are also useful in nursing homes and hospitals where patients with low resistance to microorganisms are at risk.
Solid surfaces materials that are made from acrylic resins, unsaturated polyesters resins, epoxy resins, or any other resins and incorporate certain antimicrobial agents within the resins, as described in WO97/49761 by E. I. du Pont de Nemours and Company” These antimicrobial agents are expensive and can result in high installation costs for solid surface materials.
Chitosan, and chitosan metal compounds, are known to have antimicrobial activity, as bactericides, and fungicides. (See, for example, T. L. Vigo’s?Antimicrobial Fibers and Polymers: Retrospective, and Prospective? In Bioactive Fibers & Polymers (J. V. Edwards & T. L. Vigo eds. ACS Symposium Series 792): J. V. Edwards & T. L. Vigo. American Chemical Society 2001, pp. 175-200. Chitosan also has antiviral properties, although the mechanism of action is still not well understood.
Chitosan is the commonly used name for poly-[1-4]-?-D-glucosamine. Chitosan is chemically derived from chitin (a poly-[1-4]-?-N-acetyl-D-glucosamine) which, in turn, is derived from the cell walls of fungi, the shells of insects, and, especially, crustaceans. It is therefore a cheap material that can be derived from a wide range of materials. Primex (Iceland), Biopolymer Technology, Inc., (Westborough) and Biopolymer Engineer, Inc., (St. Paul Minn.), are all companies that sell it. CarboMer, Inc., Westborough, Mass. Chitosan may also be treated using metal-salt solution so that metal ions form a complex with chitosan. U.S. Pat. Nos. Nos. 5,541,233, and 5,643,971 describe a method for making durable antimicrobial agents. A chitosan solution is treated with zinc and copper metal salts and then chelated to a potentiator like imidazole. The WO 99/37584 application discloses the preparation chitosan, zinc sulfate copper sulfate silver nitrate compounds for treating water in order to reduce pathogen levels.
In the commonly assigned U.S. Patent Application No. In U.S. Patent Application No. 60/290 297 (filed on 11 May 2001), it is shown that chitosan, in the form of a solution acidic applied to polyester articles, imparts antimicrobial properties. “The chitosan treated article can be treated with a solution containing zinc sulfate or cupric sulfate to increase antimicrobial activity.
Cultured Marbles” have been developed that incorporate an antimicrobial agent only in the gel coating (i.e. not throughout the matrix substrate). These materials were disclosed in Japanese Patent Application Publication Kokai 7-266522. The gel coating is typically 15 mils thick. When the gel coating is worn away, or the antimicrobial agent is removed from the gel, or when the gel is otherwise removed or depleted, the gel’s antimicrobial properties are significantly reduced or lost completely.
The problem is still to be solved. It’s to develop solid surface materials that contain either an acrylic resin or an unsaturated polymer resin, epoxy, or another similar resin with an antimicrobial agent.
This invention is directed at a solid-surface material that comprises a matrix made of at least one type of resin and an antimicrobial agent distributed in the matrix. The antimicrobial is a chitosan/metal complex that is isolated and prepared in homogenous conditions. The resin may be thermoplastic or thermoset. At least one filler may be added to the matrix.
In a preferred form, the resin is a mixture of a monomer mix containing an acrylic monomer and a vinyl monomer to copolymerize with an acrylic monomer monomer as the main component. The filler is an alumina trihydrate. And the antimicrobial agent is a complex of silver with chitosan or a compound of silver.
The artificial marbles in the present invention consist of a resin composition that contains a metal-chitosan complex as a antimicrobial agent. By the term “complex” as used in this document, we mean a compound. By a complex, we mean a compound where the bonding is caused by the interaction between the electrons from the donor and the empty orbitals of acceptor. In certain complexes the electron flow can occur in both directions at once. A New Dictionary of Chemistry Fourth Edition. L. M. Miall & D. W. A. Sharo, eds. John Wiley & Sons, Inc., New York, N.Y., 1968, p. 157). The preferred embodiment of this invention is a chitosan and silver complex.
The artificial marble materials in this invention inhibit or destroy many harmful microorganisms commonly found in home, food preparation, health care and other environments. Bacteria, yeasts and fungi are among the microorganisms that can be found in these environments, especially when they remain moist or damp. Examples include but are not restricted to Escherichia colitis, Candida albicans, Staphylococcus, Salmonella cholerasuis, Listeria, and Klebsiella pneumococcal.
The present invention is directed at antimicrobial surfaces. Antimicrobial surfaces are meant by the term “antimicrobial”. By?antimicrobial? The term “microbe” is used. The term?microbe’ will be used in the same way to refer to a bacterium or virus. The term “antimicrobial effectiveness” is used. The term?antimicrobial effectiveness’ is meant to indicate that, when a sufficient amount antimicrobial agent is applied, the microbial content of a test sample will be reduced by at least 3 log factors (i.e. 99.9%), over a certain period of time. The antimicrobial efficacy of an antimicrobial depends on the resin matrix and bacteria used.
The term “solid surface materials” is used here to describe materials that are essentially non-porous composites of finely divided mineral fillers dispersed in an organic polymer matrix. Herein, the term “solid surface materials” refers to materials which are essentially nonporous composites consisting of finely dispersed mineral fillers in an organic matrix. The term “organic polymer matrix” is used in this context. The term’resin matrix’ is equivalent to?organic polymer matrix? Solid surface materials can include materials used for decorative solid surfaces, such as those used in building products, such as bathroom vanities, sinks or shower stalls. Solid surface materials can also be used to construct furniture, sanitary products, linings, office supplies, and other articles.
Resin Matrix Materials
The present invention includes epoxy resins such as bisphenol type A and type F, phenol Novolak type, alicyclic, halogenated, and cycloaliphatic resins.
Unsaturated Polyester Resins” useful in the invention are those whose reactivity is dependent on the presence or absence of double or triple carbon bonds. Unsaturated polymers are produced by reacting molar quantities of dibasic acid or anhydride with glycols. The unsaturation sites are then used to crosslink the polyester chains via vinyl-containing polymers, such as but not restricted to styrene or MMA.
As those with ordinary knowledge of the art know, epoxy or unsaturated polymers can have many additives. These materials are typically cured using cross-linking catalysts and agents to increase the cross-linking effect.
The present invention is not limited to acrylic resins as long as they can be cured into solid surfaces. Acrylic resins that are useful include vinyl monomers other than acrylic monomers or partial polymers. (Meth)acrylic ester should be used as the monomer of the acrylic group. As used herein, ? (meth)acrylic? It is meant to be?acrylic or methacrylic’. Examples of (meth)acrylic esters include methyl(meth)acrylic ester, ethyl(meth)acrylic ester, butyl (meth)acrylic ester, 2-ethylhexyl(meth)acrylic ester, benzyl(meth)acrylic ester, glycidyl(meth)acrylic ester.Click here to view the patent on Google Patents.