Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-03-23
2002-09-24
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S287000, C524S403000, C524S492000
Reexamination Certificate
active
06455610
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to certain non-silicone pre-vulcanized raw rubber formulations that include silver-based compounds to provide highly desirable long-term antimicrobial characteristics within the ultimate cured rubber articles made therefrom. Such formulations are intended to be vulcanized to provide solid or blown (foam or sponge) rubber articles which can be utilized in a variety of different applications (as well as multi-layered composites including such antimicrobial rubber. As silver-based compounds are deleteriously affected by utilization of standard curing agents and curing accelerators, such as sulfur-based compounds and/or systems, the ability to provide such an effective antimicrobial vulcanized rubber article is rather difficult. However, this invention encompasses the presence of different non-sulfur-based curing systems and curing agents, such as inorganic and organic peroxides and oxides, as some examples, that permit vulcanization and do not irreversibly bind silver ions thereto, thereby resulting in long-term antimicrobial performance of the ultimate rubber article itself. The raw rubber formulations may also comprise fillers and may also include plasticizers to provide desired characteristics of dimensional stability, stiffness, flexural modulus, tensile strength, abrasion resistance, elongation, and the like, for the ultimate rubber article, while simultaneously and surprisingly enhancing the control of antimicrobial efficacy in the rubber article as well.
DISCUSSION OF THE PRIOR ART
All U.S. Patents listed below are herein entirely incorporated by reference.
There has been a great deal of attention in recent years given to the hazards of microbial contamination from potential everyday exposure. Noteworthy examples of such concerns include the fatal consequences of food poisoning due to certain strains of
Eschericia coli
being found within undercooked beef in fast food restaurants;
Salmonella enteritidis
contamination causing sicknesses from undercooked and unwashed poultry food products; and illnesses and skin infections attributed to
Staphylococcus aureus, Klebsiella pneumoniae
, yeast (
Candida albicans
), and other unicellular organisms. With such an increased consumer interest in this area, manufacturers have begun introducing antimicrobial agents within various everyday products and articles. For instance, certain brands of cutting boards, , shoe inserts, medical devices and implements, liquid soaps, etc., often contain antimicrobial compounds. The most popular antimicrobial agent for such articles is triclosan. Although the incorporation of such a compound within a liquid or certain polymeric media has been achieved, other substrates, specifically vulcanized rubber and surfaces thereof, have proven less accessible. For instance, triclosan itself diffuses easily within and out of polymeric substrates and/or matrices,and thus is not very durable. Furthermore, triclosan lacks the desired thermal stability for plastic processing at high temperatures, and does not provide a wide range of bacterial kill. For instance, triclosan does not exhibit any kill for
Pseudomonas aeruginosa.
Antimicrobial raw rubber formulations are certainly highly desired for the production of vulcanized rubber articles to provide not only antibacterial benefits, but also antifungal, antimildew, antistaining, and odor control properties. Rubber articles are utilized in many different applications, including automobiles (hoses, tires, bumpers, etc.), food processing equipment (conveyor belts, wheels, tubing, gaskets), household items (toys, sink washers, gaskets, appliances, rubber door mats, rubber floor mats, carpeted floor or door mats, gloves, and the like), basically any rubber applications in which bacterial and fungal growth is a potential problem. There thus remains a long-felt need to provide an effective, durable, reliable antimicrobial vulcanized rubber formulation which will provide such long-term antimicrobial and/or antifungal effects within the final vulcanized rubber article. Unfortunately, such a highly desired antimicrobial raw rubber formulation and/or vulcanized rubber article comprising silver-based antimicrobial agents has heretofore not been provided by the pertinent prior art.
The closest art includes Japanese Patent Application 1997-342076 which discloses the production of unvulcanized rubber formulations and articles exhibiting antibacterial properties due to the presence of silver complexes. Such formulations are formed through high temperature kneading in an oxygen-free atmosphere and are used as parts in a water disinfection system. Again, no vulcanized rubber is taught or obtained within or through this disclosure. Antimicrobial rubber bands have been taught in Japanese Patent Application 1997-140034 in vulcanized form with silver antimicrobials therein. However, such compounds are rather limited in use and the vulcanization step must include a sulfur curing agent to effectuate the final vulcanized arrangement of the subject rubber. Such sulfur curing agents have a remarkably deleterious effect on certain silver-based antimicrobials such that the sulfur reacts with the silver ion, to form silver sulfide, thus rendering it ineffective as a bactericide. As such, the utilization of such specific rubber band formulations for and within large-scale antimicrobial articles is basically unworkable.
Certain types of antimicrobial peroxide-catalyst vulcanized rubber formulations have been produced in the past; however, such peroxide-cured rubbers are all silicone-based. It is well understood and accepted that silicone rubbers cannot be vulcanized by typical sulfur-based catalysts. Thus, the antimicrobial rubber formulations of Japanese Patent Applications 1997-026273 and 1995-065149 as well as U.S. Pat. No. 5,466,726 are standard vulcanized silicone rubber formulations and articles which also include certain antimicrobial compounds.
Furthermore, rubber latexes (non-vulcanized) comprising antimicrobials have been disclosed (U.S. Pat. No. 5,736,591, for example), as have floor mats having silver-based antimicrobials incorporated within pile fiber components and which have non-antimicrobial rubber backings cured through peroxide-catalyzed vulcanization to protect the pile fiber antimicrobial compounds from attack by any sulfur compounds (as in Japanese Patent Applications 1993-3555168 and 1995-38991). Again, however, to date there have been no disclosures or suggestions of producing a non-silicone raw rubber formulation or vulcanized rubber article made therefrom exhibiting excellent antimicrobial properties through the long-term effective utilization of silver-based antibacterial compounds. This invention fills such a void.
OBJECT OF THE INVENTION
It is therefore an object of this invention to provide an antimicrobial substantially non-silicone pre-vulcanized raw rubber formulation that ultimately provides a vulcanized non-silicone rubber article of sufficient antimicrobial activity and structural integrity to withstand repeated use without losing an appreciable level of either antimicrobial efficiency or modulus strength. Another object of the invention is to ultimately provide an antimicrobial non-silicone pre-vulcanized rubber formulation comprising silver-based antimicrobial compounds which include curing agents and curing accelerators which do not deleteriously effect the antimicrobial activity of the ultimate vulcanized rubber article (and thus is essentially free from sulfur-based curing agents and accelerators). Yet another object of this invention is to provide an unvulcanized non-silicone raw rubber formulation that, upon vulcanization, cures to form such an antimicrobial non-silicone vulcanized rubber article exhibiting log kill rates for
Staphylococcus aureus
and
Klebsiella pneumoniae
(and/or other types of bacteria as well) of at least 1.0 after 24 hours exposure at room temperature. Still another object of the invention is to provide an unvulcanized rubber formulation that, upon vulcanization, cures to form an a
Haas Geoffrey R.
Lever John G.
Patel Bhawan
Milliken & Company
Moyer Terry T.
Parks William S.
Sanders Kriellion A.
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