Polymeric broad spectrum antimicrobial coatings

Details Polymeric broad spectrum antimicrobial coatings Polymeric broad spectrum antimicrobial coatings

1999-09-30

2002-04-02

Page, Thurman K. (Department: 1615)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Wearing apparel, fabric, or cloth

C424S402000, C424S443000, C424S400000

Reexamination Certificate

active

06365169

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to polymeric coatings which comprise reaction products of polyvinyl alcohol (PVA) which are insoluble in boiling water and subsequently complexed with iodine and/or borates that exhibit antiseptic, broad-spectrum antimicrobial activity in a controlled and sustained manner. More specifically, the present invention relates to a method of rendering a polyvinyl alcohol substrate coating insoluble in boiling water by using non-mineral acid catalysts and specific curing agents.
DESCRIPTION OF THE RELATED ART
Disinfectants can be defined as chemical agents that kill pathogenic organisms. Disinfection is directed against fungi, viruses, bacteria and eukaryotic parasites, such as Giarda. Traditional disinfectants act in dilute solutions by diverse mechanisms, to kill microorganisms, but can leave potentially contaminating residues behind. When applied to animate surfaces, some disinfectants may be undesirable because they also can leave rather high residual concentrations behind on the wound surface, which can adversely affect surrounding healthy tissue. Iodine is an example of a very effective disinfectant which is active in parts per million, but damaging to healthy tissue in larger amounts. In the liquid forms currently commercially available, the amount of iodine administered cannot be controlled. Other typical disinfectants include sodium hypochlorite/Chlorox, aqueous and alcoholic iodine, povidone iodine, aqueous silver nitrate, hydrogen peroxide, phenol, alcohols, benzalkonium chloride, etc.
Solid phase disinfectants are known as “contact” antimicrobials that require that the pathogenic microorganisms contact a biocidal surface, which then release an antimicrobial agent. Some solid phase disinfectants release this toxic dose of disinfectant to microorganisms upon contact, leaving very little extra or residual disinfectant behind in the absence of any microorganisms. These are called demand solid phase contact release disinfectants. Iodine, in certain complexed forms, can be such a disinfectant, and, in addition, even have some capability to differentiate between the proteinaceous matter of bacteria and the proteins present in surrounding healthy tissue. This PVA/iodine starch complex will therefore lose less specificity or effectiveness against the bacteria. Most disinfectants are soon rendered ineffective, since they are reactive toward diluting body fluids and tissue. Well known, demand release type disinfectants include strong base anion exchange resins described in U.S. Pat. No. 5,431,908, and other U.S. Pat. Nos. 3,817,860 and 3,923,665, describing other types of ion exchange resins that bind or complex iodine for use in water treatment disinfection. Insolubilized PVA/iodine complexes, even though not an ion exchange resin also releases small, controlled amounts of iodine (U.S. Pat. No. 5,071,648), which performs as a solid phase antimicrobial on contact, and can also be formed into a useful coating.
U.S. Pat. No. 5,071,648, discloses a post treatment insolubilizing process for forming a free standing film. However, insolubilizing the free standing film requires its post immersion in a solution of formaldehyde and sulphuric acid to cause the acetal cure and insolubility. U.S. Pat. No. 5,071,648 also discloses effective antimicrobial polyvinyl acetal sponge wipes. However, they are generally too costly for most applications because they are based in its entirety on one expensive material (PVA sponge) and also because of this limitation, cannot form the various shapes and combinations necessary to fulfill many industrial and consumer needs.
U.S. Pat. No. 5,071,648 also discloses another free standing film forming process for forming highly insoluble films, which resin solution also contains formaldehyde and sulphuric acid to form insoluble acetals. It further describes a coating of a matrix reinforcement which is sized with pure PVA, without a curing agent, to be subsequently complexed with iodine. However, these sizing coatings are not highly insolubilized, nor do they have to be, as they are proposed for use in non-wiping applications, e.g., to create a single use antiseptic area or environment for application to surgical drapes, gowns and wet dressings, which do not require high coating strength, as would be necessary in a multi-use wiping or scrubbing product.
The prior art in general also teaches coating a PVA foam onto a polyester (Dacron) reinforcing substrate which resin formula also contains mineral acid and formaldehyde curing agents to form acetal cures. These non-iodine complexed PVA foam products are used as car chamois and sport toweling. Polyester is resistant to mineral acid attack, but polyester is limited in the forms available, e.g. no sponges or papers, and the prior art does not describe iodine complexing these polyester reinforced PVA foam sheets.
It is important to note that in order to deposit insolubilized PVA onto a cellulose substrate, previous to iodine complexing, the insolubilizing components of the PVA coating solution must not contain a component that can substantially attack or break down the substrate. Since mineral acid catalysis to form insoluble acetals is the means by which PVA in the prior art is commonly cured, and mineral acids break down cellulose sponges, papers, and cotton cloths, etc., other means by which PVA can be insolubilized are required. In addition, the alternative PVA curing or insolubilizing agents also must not attack cellulose, and must effectively and economically cure the PVA without interfering with the subsequent step of iodine complexing.
The present invention provides a method of making highly insolubilized PVA coatings without the use of mineral acids. Surprisingly, the insolubilizing PVA agents of the present invention not only do not degrade the cellulose substrate but also do not interfere in the iodine complexing reaction, permit a more controllable iodine release with wider applicability at less cost.
SUMMARY OF THE INVENTION
It is the object of this invention to provide a method for preparing less expensive, more widely applicable antimicrobial sponges, cloths and papers.
It is also the object of this invention to form highly insoluble PVA non-mineral acid catalyzed coating (not soluble in boiling water) systems for depositing on, and interstitially onto a variety of readily available, inexpensive, e.g. cellulose derived, or other economical substrates without attacking such substrates.
It is a further object of this invention to complex this coating with iodine and/or borates, to produce controlled iodine release coating materials inexpensively, in the form of conventional cellulose sponges, cloths, papers, non-wovens, etc.
It is a further object of this invention to control the amount of iodine content, and its release, by controlling the amount of insolubilized PVA on the substrate to which it is complexed.
It is also another object of this invention to mix PVA with other iodine compounds and/or iodine complexing materials that are also compatible with PVA and/or iodine.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a method for making a substrate normally not capable of being complexed with iodine, said substrate being made capable of iodine complexing, by coating or impregnating the substrate with a solution containing a PVA polymeric mix that can be rendered insoluble by curing in the presence of a non-mineral acid catalysts and optionally a cross-linking agent, and subsequently iodine complexing to act as a solid state antimicrobial device.
The presence of the curing agent (which is defined herewith as the non-mineral catalyst and optionally the cross-linking agent) of the present invention has an insolubilizing effect, yet still permits the formation of post iodine complexes, and most important, has little or no noticeable effect on the mechanical strength of the substrate receiving the coating, and is economical and allows ease of manufacture.
Preferably, the non-mineral acid catalyst is selected from the group consisting

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