Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Using disinfecting or sterilizing substance
Reexamination Certificate
1999-04-14
2002-09-17
Warden, Sr., Robert J. (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Using disinfecting or sterilizing substance
C422S029000, C422S037000, C424S661000, C424S665000, C423S472000, C423S477000, C252S187210
Reexamination Certificate
active
06451253
ABSTRACT:
FIELD OF THE INVENTION
Field of the Invention
The herein disclosed invention is directed to chlorine dioxide formulations to be applied as disinfectants, deodorants, topical preparations and for like uses. More specifically, the invention is involved with the preparation gels of chloride dioxide to be used as disinfectants, deodorants and the like.
BACKGROUND OF THE INVENTION
While there is much literature describing chloride dioxide gels, there is a need in the industry for gel products with controlled amounts of chlorine dioxide and which are easy to prepare. In addition to ease of preparation, there is a need for gel compositions with high concentrations of chlorine dioxide.
The gums employed as the gels or thickeners of this invention are generally supplied as powders and with the addition of water, thicken and become a gel.
The patent literature contains references to the use of gels for various applications ranging from a biocidal wound dressing, skin sterilants, veterinarian applications, treatment of skin conditions such as psoriasis, fungal infections, eczema, dandruff, acne, genital herpes lesions, and leg ulcers. Chlorine dioxide gels made in situ by mixing a chlorite containing gel with a lactic acid gel have been cited for prevention of transmission of HIV virus. Gels have also been cited as anti-inflammatory agents for reducing various tissue inflammations.
Prior Art Patents
A review of the patent literature on the topic of the preparation of chlorine dioxide containing gels, discloses prior art patents which involve the use of sodium chlorite as the precursor for chlorine dioxide preparations, along with some method of converting said chlorite to chlorine dioxide at the time of use.
The one patent which claims chlorine dioxide as an actual component in a gel is the Hutchings Patent, U.S. Pat. No. 4,861,514. Hutchings mixes chlorite and “initiator”. Included among the “initiators” is hydroxalklycelluloses, alkali metal alginates, xanthan gum, cargeenen, agar and compounds containing an aldehyde substituent group. Methyl cellulose and sodium carboxymethylcellulose were found not to be initiators. The sodium chlorite disclosed in the patent is used at a concentration of 0.01 to 1% by weight, and the initiator is used at levels greater than 0.05, and preferably above 0.1%. Dyes, perfumes and reducing sugars were also included in the mix. Hutchings claims a chlorine dioxide equilibrium concentration formed within a week of 0.1 to about 10 ppm, with a preferable concentration 0.1 to 2 ppm (column 7, line 9). The patent claims disinfection at greater than 1 ppm chlorine dioxide, and cleaning and sanitizing at about 2 ppm. The chlorine dioxide achieves an equilibrium at a low concentration. With the equilibrium concentration of chlorine dioxide is from 0.1 to about 10 ppm and preferably 0.1 to 2 ppm, it can be readily discerned that the concentration of chlorine dioxide taught by Hutchings does not come close to that desired in the present invention.
U.S. Pat. No. 4,861,514 cites formation of chlorine dioxide from chlorite and xanthan gum initiator. As chlorine dioxide reacts with organics, or decomposes spontaneously, chlorite is one of the decomposition products. Formed chlorite would be encouraged to reform chlorine dioxide by reaction with the acid functionality inherent in the xanthan gum, supporting the claim of gel stability using xanthan gum. Hutchings (U.S. Pat. No. 4,861,514) actually uses this chemistry to make his chlorine dioxide in situ. This stability is in contrast to the behavior of xanthan gum in the presence of other oxidants, such as persulfates, peroxides and hypochlorites, all of which depolymerize xanthan gum. As manufactured either as a 25% aqueous solution, or an 80% solid, sodium chlorite contains alkalinity to provide chemical stability. The chlorite is inert and does not convert to chlorine dioxide in a high pH environment. Addition of acid is required to promote conversion to chlorine dioxide. If the acidity is provided by xanthan gum alone, without the addition of any other organic or inorganic acids, then the amount of chlorite which can be included in the mix is limited, since the accompanying alkalinity of the chlorite partially neutralizes the acidity of the xanthan gum, preventing conversion of chlorite to chlorine dioxide. This limits the final concentration of chlorine dioxide which can be prepared in the absence of additional added acid to less than 200 ppm. Hutchings does not state this, but he is claiming only very dilute chlorine dioxide systems, and therefore is out of the range of gel concentration possible with the herein disclosed invention.
Crotty et al in U.S. Pat. No. 3,741,805 teaches a cleaning and sanitizing composition containing xanthan gum. Chlorine compounds are mentioned, but chlorine dioxide is not mentioned.
Iwahashi in U.S. Pat. No. 5,360,574 discloses a polyethylene-imine gel system containing chlorine dioxide. The system with the gel is actually a chlorite which is stabily stored in alkali and becomes active in acid (column 1). Iwakhashi is not, in fact, pertinent for while the patent refers to “stabilized chlorine dioxide” the product of the patent is actually a solution of sodium chlorite which has an alkaline pH. This high pH is necessary in order to insure the stability of the product. In short, the Iwakhashi product is sodium chlorite and not chlorine dioxide.
In brief, the prior art processes, unlike the instant invention, do not start with chlorine dioxide per se in solution and thicken, but rather start with chlorite which when mixed with an acid-containing gel partially converts to chlorine dioxide after mixing.
Objects of the Invention
This invention has for an object the efficient preparation of chlorine dioxide gels.
Another object of this invention is the preparation of chlorine dioxide formulations in chlorine dioxide concentrations not attained by the prior art.
A significant object of this invention is to prepare a gel composition with high concentrations of chlorine dioxide.
These and other objects of the present invention will become apparent from a reading of the following specification.
BRIEF SUMMARY OF THE INVENTION
Detailed Description of the Invention
The herein disclosed invention sets forth the novel methods for preparing higher concentrations of chlorine dioxide gel compositions. Involved are two types of chlorine dioxide gels, namely, those formed directly from aqueous chlorine dioxide solutions and added thickeners; and those formed by adding a specific thickener to dilute chlorite solutions, and having the chlorine dioxide generated spontaneously on storage.
Gels of this invention are novel in that the chlorine dioxide solution is prepared before the gelling action takes place, so that the concentration of the final gel can be set to any desired level beforehand by using a chlorine dioxide solution with a concentration appropriate for the intended application. The gels may be used as is without any need for additional mixing or preparation. This method allows preparation of gels with a wide range of concentrations. The use of xanthan gum as the thickener is most preferred because this polysaccharide has acid functionality which contributes to the stability of the chlorine dioxide in the gel.
Gels using various quantities of xanthan gum thickener and aqueous chlorine dioxide were prepared. It was observed that xanthan gum appeared to improve chlorine dioxide storage stability. Systems of aqueous chlorine dioxide mixed with guar gel, xanthan gel, and a mix of guar and xanthan gel all retained high levels of chlorine dioxide in the gel, but the systems with the highest levels of xanthan gum retained more chlorine dioxide than similar concentrations of guar gel. There are three possible reasons for this:
1. The higher viscosities help retain chlorine dioxide in the gel phase by reducing diffusion and consequent volatility.
2. The acid functionality on the xanthan gum polysaccharide polymer improves chlorine dioxide stability and encourages chlorine dioxide formation from any chlorite
Miller Jennifer R.
Pitochelli Anthony R.
Bloom Leonard
Rosen Sam
Soubra Imad
Vulcan Chemical Technologies, Inc.
Warden, Sr. Robert J.
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